© 2018 Elsevier LtdModern high-performance aircrafts operate in regular flight regimes, in which the nonlinearities of the system directly influence the dynamical response of the aircraft. This work studies the dynamics of a fighter aircraft operating at high angles of attack of the wing. A mathematical model was developed deriving a system of nonlinear dynamical differential equations representing the longitudinal flight of the aircraft, considering the effect of the variation of the wind speed due to the atmospheric turbulence in the dynamic response of the aircraft. The dynamics of the aircraft is modeled as a two-degrees-of-freedom system, and the variation of the wind gusts is considered as a single-degree-of-freedom system. The analysis of the behavior of the system is carried out through the 0–1 test method to determine if the system is chaotic or periodic, which is applied in relation to the speed and angle of attack of the aircraft. As an object of study, all the considerations and analyses regarding the F-8 aircraft “Crusader” were took into account. A control technique is proposed in a nonlinear way, at which the angle of tail deflection is considered as a control parameter and projected using the method of control of the State Dependent Riccati Equations (SDRE) in order to stabilize the wing angle oscillations, considering critical regions of the behavior of the aircraft. Numerical simulations demonstrated the efficiency of the SDRE control, taking into account the comparison of the dynamics of the system with and without control, by using phase planes and parametric uncertainties, where the controller showed to be able to respond quickly and reliably to recover the aircraft from a stall situation.

© 2018 Elsevier LtdThis paper concerns the probabilistic modeling of uncertainties in structural dynamics. For real complex structures, the accurate modeling and identification of uncertainties is challenging due to the large number of involved uncertain parameters. In this context, the nonparametric probabilistic approach which consists in modeling globally the uncertainties by replacing the mass, stiffness and damping reduced matrices by random matrices is attractive since it yields a stochastic modeling for which the level of uncertainties is controlled by a small number of dispersion parameters. In its classical version, these random matrices are assumed to be independent. This assumption is valid (and proven) in absence of information concerning the dependence structure of these random matrices. In some situation, such as the presence of geometry uncertainties, this assumption is not valid any more and may yield an overestimation of the output levels of fluctuation. In this context, the present paper presents an extension of the classical nonparametric probabilistic to take into account a dependence between the random mass and stiffness matrices. This new modeling is illustrated on a beam structure for which the diameter presents spatial random fluctuations along the longitudinal direction.

© 2018, Springer Science+Business Media B.V., part of Springer Nature.This paper was written in honor of Prof. Viktor Olimpanovich Kononenko from Ukraine and takes into account reports of recent progress about non-ideal vibrating systems (NIS) published in the period from 2004 to 2017. New and old studies of NIS, with limited power supply (small DC motors or electrodynamical shakers), are usually used in laboratory tests, and therefore, the investigation of mutual interactions of driven and driving sub-system is very important. In this paper, main properties of NIS have been reviewed, such as the Sommerfeld effect, i.e., jump phenomena and the increase in power supply that is required by an excitation source operating near resonance; the possibility of saturation phenomenon occurrence, i.e., the transference of energy from higher frequency and lower amplitude to lower frequency and higher amplitude mode; and the existence of regular (periodic motion) and irregular (chaotic motion) behaviors, depending on the value of control parameters (voltage of a DC motor). This paper is divided into two goals: on the one hand will be treated about NIS and on the other hand will be provided an overview of the main engineering applications, analyzing their physical phenomena involved and the adequate methodologies to deal with them.

© The Authors, published by EDP Sciences, 2018.The studies on the so-called smart materials have grown in the last years due to the diverse possibilities that these materials can provide. These types of materials have the ability to respond to an external excitation, altering its physical form, and being able to be considered as actuators. Among these materials are the Shape Memory Alloys (SMA), several metal alloys that are able to memorize a shape and recover it after a deformation through an increase of its thermal energy. In this paper, an actuator consisting of an SMA wire is used to attenuate the vibration and Sommerfeld effect of a non-ideal type oscillator. The temperature control of the actuator was carried out through the application of an electric current in the wire. Results are presented for different currents, with the objective of investigating the temperature variation for vibration control applications. The results showed that it is possible to apply SMA actuators to the attenuation of the Sommerfeld Effect as well as in the reduction of the total vibration of the system.

© CSP - Cambridge, UK; I & S - Florida, USA, 2018.The aeronautical industry is continuously investigating nonlinear phenomena that might happen as it evaluates. Every dynamic system is subject to nonlinear behavior, especially if it is very complex like an aircraft. The nonlinearity nature, for these cases, can be aerodynamic, such as dynamic stall or shock waves, or structural, for example, freeplay or large displacements and high flexibility. This work will investigate a very flexible wing with high aspect ratio subjected to unsteady flow with a slender body at the wing tip to induce flutter. A flutter analysis is proceeded in order to evaluate the error between the computational results and the experiment. Since the linear flutter theory considers small displacements, nonlinear phenomena are expected. So the experiment time series shall be analyzed and this nonlinearity studied. The evaluation if the system presents chaotic behavior will be performed through the 0-1 test.

© 2018 SPIE.This paper discusses the detection of borders vulnerability through remote sensing. Remote sensors enable government to collect rapidly synoptically data from areas where the access is restricted. Accordingly, we propose a preliminary survey of Brazil's borders and its structures by using remote sensing techniques. The extent of the area is a difficulty, as Brazilian borders measures more than 15,000 kilometers in total and marks the limit to 10 countries. The methodology used can be summarized in the following steps: (i) choosing twelve sample-areas along Brazil's frontier vis-à-vis each neighboring country, focusing on the existent infrastructure; (ii) defining classes of land-use and land-cover based on the elements of visual image interpretation; (iii) creating an image interpretation key; (iv) measuring spectral signature from different targets. Results allow creating a hierarchical model of bodies related to the visual image interpretation element and spectral curves. This model has been divided between natural and anthropogenic features, it is compared the infrastructure, land-cover and land-use from distinct parts along the Brazilian land border. It is concluded there are serious problems of frontier governance due to Brazil's border is very heterogeneous.

© Springer International Publishing AG, part of Springer Nature 2019.This work describes the nonlinear identification applied to an aeroelastic pitch-plunge system using polynomial NARMAX model and a stability analysis. The apparatus is available and consists of a wing typical section with pitch and plunge degrees of freedom. The identification procedure aims to obtain the parameters for the mathematical model including the torsional stiffness as a quadratic polynomial function. The candidate structure to the polynomial model is obtained from discretization of a continuous-time state-space model and the predictions are obtained via the identification procedure using simulated data. The simulation is performed considering the aerodynamics with free stream velocity increased within an established velocity range which includes the flutter phenomenon. In future work, a data acquisition from the experimental apparatus will be performed. The NAR-MAX model indicates a polynomial function of fourth order for the nonlinearity and a stability analysis, discussed in this work, mapping the nonlinear regions.

© Springer International Publishing AG, part of Springer Nature 2018.This work presents the modeling and simulation of a manipulator robot with three degrees of freedom and considering its structures with rigid behavior. The concepts of kinematics for the mathematical deduction and the Lagrangian mechanics were used to obtain the dynamic models of the manipulator and the DC actuators with permanent magnet. Due to nonlinearity and dynamics characteristics, both the states observer and the control used were based on State Dependet Ricatti Equation (SDRE). The simulations made for constant performance parameters demonstrated the effectiveness of the optimal control applied to the manipulator and to the chosen DC actuator models. The applications of trajectories to the manipulator enrich the applicability of the project and the results obtained with the techniques chosen show his efficiency.

© The Brazilian Society of Mechanical Sciences and Engineering 2018.This study analyzes a nonlinear system with a crank–shaft–slider mechanism linked to a pendulum. The crank is powered by a DC motor that moves horizontally the pendulum pivot. The speed of the motor is influenced by the pendulum dynamics, reason for calling the system as nonideal. In literature, the vibration of the pendulum support by a crank–shaft– slider is generally considered as harmonic what neglects the real complexity of the mechanism. It is also common, for the crank speed or the excitation frequency to be considered constant, so a unique degree-of-freedom can take place. The novelty in this research is the analysis of the feedback effect of the pendulum over the crank speed and the complexity of crank–slider mechanism without approaching to a harmonic motion. Different types of motion occur as oscillations, rotations, and chaos. Results with different initial conditions are worked out and basins of attractions plotted. Chaos was obtained when small variations of parameters are made. The methods of analysis include phase portraits, time histories, bifurcations diagrams, and basins of attraction. The verification of chaotic phenomena is performed through the 0–1 test. By the end, the feedback control is applied using the method of Tereshko by altering the energy of the chaotic system, leading the pendulum to a limit cycle.

© 2018, Brazilian Association of Computational Mechanics. All rights reserved.Shape distortions and warpage are a major source of problems for composite manufacturers. These distortions are usually accompanied by built up residual stresses. They can deform a component so that it becomes useless. It also has the capability to reduce the strength of the structure. In this paper, the three-dimensional version of the constitutive model originally proposed by Svanberg and Holmberg is employed to predict the warpage of a wing planform. The model takes into account important mechanisms such as thermal expansion, resin shrinkage and frozen-in strains developed during curing cycles. The model was implemented into ABAQUS Finite Element code as a user subroutine UMAT. The macromechanical properties of each composite layer were predicted using a micromechanics based approach, implemented into MATLAB. Results show that wings with cross ply laminates with reducing thickness along the span experienced more warpage than quasi-isotropic laminates. Furthermore, for wings with equal thickness along the span, the results show that the quasi-isotropic laminates experienced more warpage than cross ply laminates. Lastly, the results show that wings with progressively reducing thickness experience twist that is varying from the wing root to the wing tip while wings with a constant thickness experience twist mainly at the centre of the wing.

© 2018, Universidade Federal de Uberlandia. All rights reserved.This study discusses the microstructure, quasi-static mechanical strength and failure modes of TWIP steel weld spots. Weld spots were produced by varying the main resistance spot welding parameters: welding current, welding time and electrode compression force. All the samples showed a remarkable material hardness mismatch between the fusion zone, the heat affected zone and the base material, as evidenced by microindentation maps. Hardness at the fusion zone is lower than that of heat-affected zone and base metal, which facilitates interfacial failure mode during tensile-shear tests. However, high heat inputs promoted the failure mode changes to partial interfacial mode and then to pullout mode during tensile-shear tests as confirmed by Scanning Electron Micrographs. These changes in failure mode were accompanied by a notable increase in tensile-shear strength and energy absorption capability.

© 2018, The Brazilian Society of Mechanical Sciences and Engineering.As shown in the literature, there is plentiful information about sandwich panels. Two of the most common points under discussion are the failure modes and the efficiency of numerical simulations considering the stiffness and interlaminar stress. The failure modes in the literature are not always likely to happen in practice, and representing them becomes a challenging task. Regarding the numerical simulations, new assumptions and formulations appear in order to consider the shear stress in the honeycomb CORE and to minimize processing time in 3D models. Although new mathematical solutions emerge, in some cases they are unpractical for engineering applications and must be evaluated and compared with test results in order to verify their consistency. Therefore, experimental results are necessary to validate theories to comply with the failure modes observed in sandwich panels and to validate the finite element model. Also, the main focus of the literature is on the theoretical formulation and not in engineering applications. In this sense, the main contribution of this paper is to bring forward experimental results of aeronautical sandwich panels whose data are scarce and therefore contributes to the validation of new developments. In addition, the purpose of this work contributes to the use of the finite element models with composite sandwich panels where the appropriate input for 2D (plate) and 3D (solid) elements is unclear. It should be pointed out that for failure investigation the first step is validating the finite element model. In this sense, a typical aircraft panel with experimental results is presented. The finite element model and the input parameters that are not mentioned in the classical literature are also presented. The experimental strain from specimen tested agreed well with the numerical simulations results.

© 2018, © IMechE 2018.Deep rolling is performed on crankshafts since the 1960s, yet there is still a knowledge gap regarding residual stress generation. Until this moment, there is no consolidated and widespread procedure to predict such stresses during the crankshaft design cycle. This study establishes an analysis procedure and correlates it with experimental results. An explicit finite element model with real boundary conditions is developed together with a converged mesh for the fillet radius. Simulation nodal displacement and strain output are compared to geometrical measurements using a coordinate-measuring machine. Outputs in terms of residual stresses are related to X-ray diffraction measurements taken along fillet depth. The experimental results attest to the accuracy of the model and correctness in predicting the process outcomes.

© 2017 Elsevier LtdA beam element is proposed that captures through the thickness effects in composite laminated beams, namely, transverse shear and normal stresses and strains. Stress continuity along the thickness is inherently enforced leading to a system of algebraic equations that is solved in the element level, permitting independence between the number of layers and the number of degrees of freedom, with all of them possessing a clear physical significance. Global-local superposition is performed in the thickness direction, where a cubic global displacement field, that guarantees imposition of the boundary conditions at the top and bottom surfaces of the beam, is combined with a layerwise linear local displacement distribution that assures zig-zag behavior of the stresses and displacements. The element behavior for different length-to-thickness ratios is assessed and compared to the analytical elasticity solution, as well as a commercial finite element alternative.

© 2018, Brazilian Association of Computational Mechanics. All rights reserved.An adaptation of the conventional Lanczos algorithm is proposed to solve the general symmetric eigenvalue problem Kϕ = λKGϕ in the case when the geometric stiffness matrix KG is not necessarily positive-definite. The only requirement for the new algorithm to work is that matrix K must be positive-definite. Firstly, the algorithm is presented for the standard situation where no shifting is assumed. Secondly, the algorithm is extended to include shifting since this procedure may be important for enhanced precision or acceleration of convergence rates. Neither version of the algorithm requires matrix inversion, but more resources in terms of memory allocation are needed by the version with shifting.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This paper evaluates the impacts of the technological improvement of transonic airfoil design in a case study of multi-disciplinary optimization of a near-sonic business jet aircraft. The aerodynamic transonic drag divergence characteristics twenty three transonic airfoils were quantified trough Navier-Stokes CFD simulations. The technological factor that quantifies the mach number of drag divergence in association with the geometrical parameters were then related to several mathematical combinations of the geometrical parameters in order to access which parameters are relevant. This relation enables the estimation of the technological factor based on the geometry of an airfoil, closing part of the gap between which geometrical design variables are necessary to guarantee the desired performance.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The continuous search for aircraft flight performance to obtain lower fuel consumption leads to the optimization of wings shape and structure focused in the longer flight phase of its mission, the cruise phase. However, this leads to a loss of efficiency for other flight phases such as take-off and landing, resulting in the need for high-lift surfaces, that are basically triggered by electro-mechanical or hydro-mechanical actuators, adding a considerable amount of weight, complexity and cost to the design project. New concepts of aircraft have wing solutions that are optimized for every flight phase and, consequently, are capable of adjusting their structures in order to achieve the best performance on each flight situation. One of the main ideas on how to get this result is the implement of morphing wings by using smart actuators. Shape memory alloys are classified as smart materials and they can be used in order to develop light, simple and cheap solutions to obtain controlled modifications on aircraft aerodynamic surfaces. This paper focuses on evaluating the airfoil thickness effects on morphing wings composed by memory alloy actuators capable of camber adjustment. In order to achieve this goal, the morphing NACA 0020 designed for the present project is compared to a morphing NACA 0012 wing prototype. The fact that previously mentioned prototypes have different airfoil thickness promotes the ideal environment to investigate this effect on the performance of morphing wings capable of camber adjustment. In addition, each previously mentioned morphing wing prototype was compared to its traditional flap configuration to investigate the aerodynamic pros and cons related to this morphing mechanism. The comparison shows that despite the morphing wing as studied resulting in a lower performance, it’s design simplicity and weight reduction brings advantages to the whole aircraft in certain conditions.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Aircraft with three engines, as known as trijet, became a standard design among manufacturers after 1964 when the FAA's 60-minute rule was established for these aircraft. This regulation restricted the flight path to 60 minutes' flying time to a suitable airport, therefore affecting the operation costs and limiting the range of twin-jet aircraft. However, improvements to the engine's reliability in the following decades allowed ETOPS certification for twinjet aircraft. The traditional trijet designs were slowly retired, the last commercial trijet flight was in 2014.The industry abandoned the trijet design as solution for commercial aviation; however, executive jets such as the Falcon 7x and Falcon 8x, certified in 2016, show that this configuration might still be advantageous for specific markets. The certification at one engine inoperative condition presents an advantage for trijet aircraft, reducing takeoff thrust, since when one engine is inoperative, 75% of the total thrust is available for the trijet aircraft, while this value is only 50% for a twin-jet aircraft. An initial study conducted showed a trend of lower thrust to weight ratio for trijet aircraft when compared to twinjet aircraft, being particularly evident for MTOW (maximum takeoff weight) lower than 75,000 lb. The aircraft design is related to a multidisciplinary view. So, the thrust reduction and the implementation of a third engine have impacts on fuel burn, structural weight, external noise, performance, certification, maintenance, and the fuel feed system. In this sense, the multidisciplinary view justifies distinct thrust to weight ratio reduction caused by trijet configuration for different MTOW range. The aim of this work was to study the viability of a trijet aircraft configuration and potential advantages for a regional aviation scenario. The trijet configuration performance was evaluated and compared to twinjet configuration in a multidisciplinary design environment considering disciplines such as aerodynamics, noise, performance, flight mechanic, weight, and structure. An aircraft with MTOW of 48,500 lb. was studied and the results showed that a reduction up to 6.25% of installed thrust might be achieved with the trijet design compared to twin-jet aircraft when the field length defined by aviation regulations is the critical constraint. However, flyover noise, structural weight and direct operating cost might increase in trijet design.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.An experimental investigation has been undertaken to study the wavy leading edge phenomena on rectangular wing of aspect ratio 4 with a NACA 0020 airfoil at Reynolds number range from 700,000 to 3,000,000. Force measurements for various shapes of sinusoidal leading edge indicate smaller amplitude and shorter wavelength configuration (A3λ11) presenting a substantial increase in aerodynamic performance at entire range of Reynolds number tested when compared to baseline configuration, as result achieving 28.3 % of increasing in maximum lift coefficient. Oil flow visualizations reveal that tubercles with smaller amplitude have the role of delaying trailing edge flow separation. At high angles of attack, the A3 λ 11 configuration is shown to present spanwise wavelengths for which the optimal generation of streaks in turbulent boundary layers is expected according to previous experimental works. The appearance of such streaky boundary layers is a possible reason for the delay in flow separation and increase of maximum lift coefficient.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Optimization of wing shapes has been a constant struggle throughout the years of aircraft and aerodynamic development. Innovations have flourished in all scientific fields that influence wing design, such as materials, structural, manufacturing and aeronautical engineering, in order to improve performance and consequently reduce fuel consumption of aircraft, which translates in a light wing with an airfoil shape that assures the best lift coefficients required for a specific mission. On the other hand, this penalizes other maneuver possibilities for the same aircraft, hindering its capabilities and demanding development of different solutions, impacting on costs and draining resources. An “one fits all” concept solves this hurdle, since one design could accomplish a variety of missions, with adequate values for lift coefficient for each different flight phase. This concept can be achieved by wings capable of morphing, adjusting their structures on demand. One widely investigated field of research is morphing wings that uses smart materials, such as shape memory alloys, for actuation. Shape memory alloys are lightweight, simple and cheap materials that, combined with a morphing compliant rib, can achieve controlled displacements on aerodynamic surfaces. This paper analyses different rib concepts modifying chordwise positions for actuation by making use of shape memory alloy wires built-in a NACA 0012 reference wing. A comparison is made between different percentages of chordwise morphing capability and a simple NACA 0012 wing with a 25 percent chord plain flap, as usually seen on many simple aircraft designs. The results show an increase on lift coefficient values and a delay of stall angle for some chordwise actuation locations. The comparison parameter was a 15 degree of trailing-edge tip displacement related to the airfoil leading-edge. By reducing external surface gaps and steps, a simple and lightweight smart morphing wing can overcome a common flap design and still achieve a variety of different missions by adjusting itself in flight.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This work investigates wavy leading edge phenomena at transonic flow regime. Pressure sensitive paint measurements are performed over upper surface airfoil at transonic flow regime. The experimental investigation was conducted at a transonic wind tunnel at Reynolds number of 1,000,000, Mach number from 0.6 to 0.7, and angle of attack from 0 to 4 degrees. Two sets of airfoil were used, a smooth NACA0012 profile as baseline model and a wavy leading edge NACA0012 profile with amplitude of 3% and wavelength of 11% both related to chord of the airfoil. The models were manufactured using a 3D rapid prototyping which significantly improved time and cost, and also the feasibility and accuracy of such complex wavy leading edge airfoil. Pressure sensitive paint measurements indicates an impressive modification on flow pattern caused by tubercles when compared to baseline airfoil. If on hand, the baseline airfoil presents lambda-shock wave pattern, on the other hand, the wavy leading edge model changes this flow pattern avoiding shock wave structure. A likely explanation for tubercles avoid shock wave is related to possible counter-rotating vortex generated by wavy configuration upstream of the shock wave line. Thus, the results presented here indicates a potential to apply tubercles in commercial aircraft wings at transonic regime in order to decrease drag rise.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The swept wing configuration showed interesting results for the leading edge phenomena in recent studies. The most important outcomes showed that configurations with higher wing loading at the tip (such as tapered and swept wings), tend to be more susceptible to the effect of tubercles, giving an important increase in stall angle, and consequently, in maximum lift coefficient. A remarkable gain of about 20% on CLmax (without large penalties on drag coefficient) was obtained in 30° swept models with taper ratios of 1 and 0.5.This increase in lift force is associated to the fact that the wavy configurations exhibit a delay on stall progression from wing tip to the root as consequence of the tubercle effects, which maintain the flow attached on leading edge at high angles of attack. To investigate the relationship between the increase in maximum lift coefficient and the swept angle, and continue with the study presented by Abrantes et al.11, a series of experiments were conducted on six wing configurations. The range of sweep-angles include wings with 30°, 40° and 50°, as well as two variations of taper ratio (TR=1 and TR=0.5). All models had an underlying NACA 0020 airfoil and a wavy geometry with amplitude A=0.03c and wavelength λ=0.11. The purpose of this research consisted in evaluating the drag and lifts forces at Reynolds number of 200,000 for all seven models and compares their results with the smooth wings. In addition, a flow visualization analysis using oil technics was included in order to better understand the involved phenomena.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The study of wavy leading edge phenomena on finite wings conducted on recent research has shown results that demonstrate improvements in aerodynamic characteristics for certain configurations. The most important outcomes were observed on swept and swept-tapered wings, attaining improvement in lift coefficients of around 20% when compared with their equivalent baseline models. This increase on lift force is associated to the fact that the wavy configurations exhibit a delay on the stall angle due to the effect of the tubercles, which main effect is to delay the stall progression from tip to root by keeping the flow attached on the leading edge at high angles of attack. Visualization results confirmed larger effect of these phenomena on the wingtip area. In order to give continuity to previous works that investigated swept wing with wavy leading edge, obtain a deeper knowledge of this phenomena and delimit the design space in which the wavy leading edge could be efficiently applied, a series of experiments were conducted on sixteen wing configurations including swept angles of 30 and 50 degrees, taper ratio of 1 and 0.5, and wavy span length of 20, 40 and 100% (from tip to root). All models had an underlying NACA 0020 airfoil and a wavy geometry with amplitude A = 0.03 and wavelength λ = 0.11 considering the root chord as reference. The purpose of this research consist in evaluating of drag and lift forces at Reynolds number of Re = 200, 000 for all models showing comparative results with the baseline wings. In addition, a flow visualization analysis using oil technique was included in order to better understand the involved phenomena.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.As a passive flow control mechanism inspired in nature, the wavy leading edge modifications have been tested here for specific rotary-wing airfoils. After examining previously studies, it was observed that these geometric devices could delay the boundary layer separation that usually occurs at high angles of attack in retreating blades, avoiding their abrupt stall. In order to evaluate if wavy leading edges could be applied successfully on helicopter blades, a series of wind tunnel tests have been performed for selected rotary-wing airfoils used in the H-60 Black Hawk aircraft. The waviness has shown a great potential to make softer the stall characteristics for the Sikorsky SC1094-R8 airfoil, a modified profile of the Sikorsky SC1095, while delaying the initial stall by up to 3◦, without a relevant increase in drag coefficient. The experimental investigation was based on force measurements (lift and drag coeficients) and oil flow visualization.

© 2018 The Author(s).Aircraft with three engines, as known as trijet became a standard design among manufacturers after 1964 when the FAA's 60-minute rule was established for these aircraft. This regulation restricted the flight path to 60 minutes' flying time to a suitable airport, therefore affecting the operation costs and limiting the range of twin-jet aircraft. However, improvements to the engine's reliability in the following decades allowed ETOPS certification for twin-jet aircraft. The traditional trijet designs were slowly retired, the last commercial trijet flight was in 2014.The industry abandoned the trijet design as solution for commercial aviation; however, executive jets such as the Falcon 7x and Falcon 8x, certified in 2016, show that this configuration might still be advantageous for specific markets. The certification at one engine inoperative condition presents advantage for trijet aircraft reducing take-off thrust, since when one engine is inoperative, 75% of the installed thrust is available for the trijet aircraft, while this value is only 50% for a twin-jet aircraft. An initial study conducted showed a trend of lower thrust to weight ratio for trijet aircraft when compared to twin-jet aircraft, being particularly evident for MTOW (maximum take-off weight) lower than 75,000 lb. The aim of this work is to study the viability of a trijet aircraft configuration and potential advantages for a regional aviation scenario. The trijet configuration performance was evaluated and compared to twin-jet configuration in a multidisciplinary design environment considering disciplines such as aerodynamics, noise, performance, flight mechanic, weight, and structure. An aircraft with MTOW of 48,500 lb was studied and the results show that a reduction up to 9.4% of installed thrust might be achieved with the trijet design compared to twin-jet aircraft when the balanced field length is the critical constraint. However, flyover noise and structural weight might increase slightly in trijet design.

© 2018 American Chemical Society.The oxygen reduction reaction (ORR) on platinum in perchloric acid is studied under transient conditions at stationary and nonstationary electrodes. Only under these conditions, the presence of a fast initial chemical step in the mechanism, giving rise to a soluble, short-lived intermediate proposed to be the HO2∗ radical, is revealed by comparing experimental and calculated curves by numerical simulations of simple reaction schemes. The formation of this species and the existence of a zero-current cycle involving it would be the main reasons for the lack of reduction currents at potentials higher than the ORR reaction onset. Additionally, regardless of the exact subsequent steps after the initial chemical reaction, if HO2∗ is generated it would disproportionate to hydrogen peroxide, which implies that both species would be always produced during the ORR on Pt. The presence of HO2∗ and H2O2 would profoundly affect the durability of Pt-based catalysts and should be taken into account in the design of materials for fuel cell cathodes.

© 2018 Elsevier B.V.In this work, recent progress in the understanding of the mechanism of the oxygen reduction reaction at Pt surfaces is shortly reviewed. Specifically, the presence of a soluble and short-lived intermediate different to H2O2 in the ORR reaction path and the interrelated effect between the surface arrangement, adsorption of oxygen-containing species and water structure in the ORR reactivity in acid environments are discussed. Besides, the influence of the proton concentration on the ORR product distribution, the existence of a chemical step and the possible role of the soluble intermediate as a bifurcation point in the mechanism are also analyzed.

© 2018 Elsevier B.V.In this work, a short revised analysis regarding the ORR mechanism at Pt-based surfaces has been performed and some common kinetic criteria have been reexamined in light of recent experimental results. In this sense, the production of H2O2 under high mass transport conditions and the lack of reduction currents at potentials higher than the experimental reaction onset, Eonset ORR, have been analyzed, considering the existence of a soluble intermediate species and an outer sphere reaction inside the ORR mechanism, besides the possible occurrence of a zero current cycle at Eonset ORR. Finally, the implications of these findings in the stability and durability of Pt-based catalysts have been also discussed.

© 2018 Elsevier Inc. All rights reserved.The oxygen reduction reaction (ORR) is one of the fundamental reactions in electrochemistry. Unfortunately, despite many years of research, the exact ORR mechanism is still unknown. In this work, a short revision of the ORR on platinum single crystals is summarized, including the effect of strongly adsorbing electrolytes and the water structure near the electrode surface on the ORR activity. Recent information from scan rate studies at stationary and rotating disk electrodes, suggesting the possible existence of a soluble intermediate species close to the reaction onset on Pt(111) is presented. In addition, the possible role of adsorbed hydroxyl, OHads; adsorbed oxygen, Oads; and Pt-oxides in the reaction dynamics is also discussed.

© 2017 Elsevier LtdNiobium carbide (NbC) exhibits important properties which make it an alternative for cutting tool material. Nowadays, the cutting tool market is dominated by the tungsten carbide, which is used in cemented carbide grades of tool materials. However, the research of a novel substrate material for cutting tool application requires mainly two aspects of study. The assessment of the cutting tool characteristics which influence the machining performance, and the machining experiments themselves. Thus, the features evaluating of the cutting tool made of niobium carbide, which indicate its potential application as the main hard phase in cutting tool substrates, were performed. Cutting tools analyses were carried out in parallel with machining experiments. Tool life experiments were carried out in external cylindrical turning conditions, in order to evaluate tool lifetimes and tool wear evolution of the cutting tools in study.

© 2018 American Physical Society.Vortex models have been used for decades as computationally efficient tools to investigate unsteady aerodynamics. However, their utility for separated flows - particularly when such flows are subjected to incident disturbances - has been hindered by the tradeoff between the model's physical fidelity and its expectation for fast prediction (e.g., relative to computational fluid dynamics). In this work, it is shown that physical fidelity and speed can be simultaneously achieved by assimilating measurement data into the model to compensate for unrepresented physics. The underlying inviscid vortex model captures the transport of vortex structures with a standard collection of regularized vortex elements that interact mutually and with an infinitely thin flat plate. In order to maintain a low-dimensional representation, with fewer than O(100) degrees of freedom, an aggregation procedure is developed and utilized in which vortex elements are coalesced at each time step. A flow state vector, composed of vortex element properties as well as the critical leading-edge suction parameter, is advanced within an ensemble Kalman filter (EnKF) framework. In this framework, surface pressure is used to correct the states of an ensemble of randomly initiated vortex models. The overall algorithm is applied to several scenarios of an impulsively started flat plate, in which data from a high-fidelity Navier-Stokes simulation at Reynolds number 500 are used as a surrogate for the measurements. The assimilated vortex model efficiently and accurately predicts the evolving flow as well as the normal force in both the undisturbed case (a separated flow) as well as in the presence of one or more incident gusts, despite lack of a priori knowledge of the gust's characteristics.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.A data-driven vortex model of the unsteady aerodynamics of a two-dimensional separated flow is constructed. The vortex model relies on a standard collection of regularized vortex elements that interact mutually and with an infinitely-thin flat plate. In order to maintain a low-dimensional representation, with fewer than O(100) degrees of freedom, a novel aggregation procedure is developed and utilized in which vortex elements are coalesced at each time step. A flow state vector, composed of vortex elements properties as well as the critical leading-edge suction parameter of Ramesh and Gopalarathnam (J. Fluid Mech., 2014), is advanced within an ensemble Kalman filter (EnKF) framework. In this framework, surface pressure measurements, sampled from a truth case, are used to correct the states of an ensemble of randomly-initiated vortex element models. The estimation algorithm is applied to several scenarios of a flat plate impulsively started at 20 degrees angle of attack at Reynolds number 500, in which the truth case comprises a high-fidelity Navier–Stokes simulation. The algorithm provides a good estimate of the flow as well as the aerodynamic force in both the baseline undisturbed case (a separated flow) as well as in the presence of one or more incident gusts, despite lack of a priori knowledge of the incident gust character.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Ensemble methods can integrate measurement data and CFD-based models to estimate the state of fluid systems in a robust and cost-efficient way. However, discretization errors can render numerical solutions a biased representation of reality. Left unaccounted for, biased forecast and observation models can lead to poor estimator performance. In this work, we propose a low-rank representation for the bias whose dynamics is represented by a colored-noise process. System state and bias parameters are simultaneously corrected on-line with the Ensemble Kalman Filter (EnKF) algorithm. The proposed methodology is demonstrated to achieve a 70% error reduction for the problem of estimating the state of the two-dimensional low-Re flow past a flat plate at high angle of attack using an ensemble of coarse-mesh simulations and pressure measurements at the surface of the body, compared to a bias-blind estimator. Strategies to determine the bias statistics and to deal with nonlinear observation functions in the context of ensemble methods are discussed.

© 2018 by the American Institute of Aeronautics and Astronautics, Inc.Regardless of the plant model, robust flow estimation based on limited measurements remains a major challenge in successful flow control applications. Aiming to combine the robustness of a high-dimensional representation of the dynamics with the cost efficiency of a low-order approximation of the state covariance matrix, a flow state estimator based on the ensemble Kalman filter is applied to two-dimensional flow past a cylinder and an airfoil at high angle of attack and low Reynolds number. For development purposes, the numerical algorithm is used as both the estimator and as a surrogate for the measurements. Estimation is successful using a reduced number of either pressure sensors on the surface of the body or sparsely placed velocity probes in the wake. Because the most relevant features of these flows are restricted to a low-dimensional manifold of the state space, asymptotic behavior of the estimator is shown to be achieved with a small ensemble size. The relative importance of each sensor location is evaluated by analyzing how they influence the estimated flowfield, and optimal locations for pressure sensors are determined. Covariance inflation is used to enhance the estimator performance in the presence of unmodeled freestream perturbations. Acombination of parametric modeling and augmented state methodology is used to successfully estimate the forces on immersed bodies subjected to deterministic and random gusts.

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature.In this study the parabolized stability equations (PSE) are used to build reduced-order-models (ROMs) given in terms of frequency and time-domain transfer functions (TFs) for application in closed-loop control. The control law is defined in two steps; first it is necessary to estimate the open-loop behaviour of the system from measurements, and subsequently the response of the flow to an actuation signal is determined. The theoretically derived PSE TFs are used to account for both of these effects. Besides its capability to derive simplified models of the flow dynamics, we explore the use of the TFs to provide an a priori determination of adequate positions for efficiently forcing along the direction transverse to the mean flow. The PSE TFs are also used to account for the relative position between sensors and actuators which defines two schemes, feedback and feedforward, the former presenting a lower effectiveness. Differences are understood in terms of the evaluation of the causality of the resulting gain, which is made without the need to perform computationally demanding simulations for each configuration. The ROMs are applied to a direct numerical simulation of a convectively unstable 2D mixing layer. The derived feedforward control law is shown to lead to a reduction in the mean square values of the objective fluctuation of more than one order of magnitude, at the output position, in the nonlinear simulation, which is accompanied by a significant delay in the vortex pairing and roll-up. A study of the robustness of the control law demonstrates that it is fairly insensitive to the amplitude of inflow perturbations and model uncertainties given in terms of Reynolds number variations.

© 2018 Elsevier Inc.We present a fast numerical framework for the computation of acoustic scattering by poroelastic plates of arbitrary geometries. A boundary element method, BEM, is applied to solve the Helmholtz equation subjected to boundary conditions related to structural vibrations. This analysis is performed by rewriting the BEM boundary conditions in terms of a modal basis of the poroelastic plate which is computed by the finite element method, FEM. The current formulation allows a direct solution of the fully coupled fluid-structure interaction problem. In order to accelerate the solution of the large dense linear systems from the BEM formulation in three-dimensional problems, a wideband adaptive multi-level fast multipole method, FMM, is employed. A parametric study is carried out for the trailing-edge scattering of sample acoustic sources, representative of either uncorrelated turbulent eddies or a non-compact turbulent jet. Firstly, the noise scattering by a compact quadrupole source is analyzed for low and high frequencies for square and trapezoidal plates. Results show that geometric features such as trailing-edge sweep and serrations are very effective in the reduction of noise scattering. Moreover, it is shown that finite elastic plates are more effective in reducing the scattered noise at higher frequencies. On the other hand, porosity is more effective in reducing the radiated sound for lower frequencies. Results demonstrate that elasticity and porosity can be combined with trailing-edge sweep and serrations to reduce the scattered noise at a broader range of frequencies for poroelastic plates.

© 2018 Cambridge University Press.Motivated by the problem of jet-flap interaction noise, we study the tonal dynamics that occurs when an isothermal turbulent jet grazes a sharp edge. We perform hydrodynamic and acoustic pressure measurements to characterise the tones as a function of Mach number and streamwise edge position. The observed distribution of spectral peaks cannot be explained using the usual edge-tone model, in which resonance is underpinned by coupling between downstream-travelling Kelvin-Helmholtz wavepackets and upstream-travelling sound waves. We show, rather, that the strongest tones are due to coupling between Kelvin-Helmholtz wavepackets and a family of trapped, upstream-travelling acoustic modes in the potential core, recently studied by Towne et al. (J. Fluid Mech. vol. 825, 2017) and Schmidt et al. (J. Fluid Mech. vol. 825, 2017). We also study the band-limited nature of the resonance, showing the high-frequency cutoff to be due to the frequency dependence of the upstream-travelling waves. Specifically, at high Mach number, these modes become evanescent above a certain frequency, whereas at low Mach number they become progressively trapped with increasing frequency, which inhibits their reflection in the nozzle plane.

© 2018, The Author(s).This work deals with the feedforward active control of Tollmien–Schlichting instability waves over incompressible 2D and 3D boundary layers. Through an extensive numerical study, two strategies are evaluated; the optimal linear–quadratic–Gaussian (LQG) controller, designed using the Eigensystem realization algorithm, is compared to a wave-cancellation scheme, which is obtained using the direct inversion of frequency-domain transfer functions of the system. For the evaluated cases, it is shown that LQG leads to a similar control law and presents a comparable performance to the simpler, wave-cancellation scheme, indicating that the former acts via a destructive interference of the incoming wavepacket downstream of actuation. The results allow further insight into the physics behind flow control of convectively unstable flows permitting, for instance, the optimization of the transverse position for actuation. Using concepts of linear stability theory and the derived transfer function, a more efficient actuation for flow control is chosen, leading to similar attenuation of Tollmien–Schlichting waves with only about 10% of the actuation power in the baseline case.

© 2018 Cambridge University Press.To investigate the effects of the nozzle-exit conditions on jet flow and sound fields, large-eddy simulations of an isothermal Mach 0.9 jet issued from a convergent-straight nozzle are performed at a diameter-based Reynolds number of. The simulations feature near-wall adaptive mesh refinement, synthetic turbulence and wall modelling inside the nozzle. This leads to fully turbulent nozzle-exit boundary layers and results in significant improvements for the flow field and sound predictions compared with those obtained from the typical approach based on laminar flow in the nozzle. The far-field pressure spectra for the turbulent jet match companion experimental measurements, which use a boundary-layer trip to ensure a turbulent nozzle-exit boundary layer to within 0.5 dB for all relevant angles and frequencies. By contrast, the initially laminar jet results in greater high-frequency noise. For both initially laminar and turbulent jets, decomposition of the radiated noise into azimuthal Fourier modes is performed, and the results show similar azimuthal characteristics for the two jets. The axisymmetric mode is the dominant source of sound at the peak radiation angles and frequencies. The first three azimuthal modes recover more than 97 % of the total acoustic energy at these angles and more than 65 % (i.e. error less than 2 dB) for all angles. For the main azimuthal modes, linear stability analysis of the near-nozzle mean-velocity profiles is conducted in both jets. The analysis suggests that the differences in radiated noise between the initially laminar and turbulent jets are related to the differences in growth rate of the Kelvin-Helmholtz mode in the near-nozzle region.

© 2018 Acoustical Society of America.Trailing edge scattering is a significant source of sound, and elasticity is known to decrease the radiated sound by a process involving coupled acoustic and bending waves. Most of the analysis available in the literature to deal with this problem is limited to structures of isotropic material. A numerical method is extended, based on the solution of a boundary element method with boundary conditions given by the structural problem, to account for anisotropic composite plates, restricted to symmetric laminates. These conditions are recast in terms of the vibration modes of a rectangular plate. To obtain these modes, the hierarchical finite element method is used to model an elastic flat plate. Expressions for bending waves propagating in such plates are derived, and how the solution of the problem is modified to account for these effects is shown. Results show modifications in the scattered sound as a function of ply orientation and stacking sequence. Composite materials are shown to be advantageous, since laminates lead to lower acoustic scattering when compared to structurally equivalent metallic plates. This is due to a lower specific mass, leading to higher coupling between fluid and solid, and thus to more significant elasticity effects, decreasing substantially the radiated sound.

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature.We study a modified backwards-facing step flow, with the addition of two different plates; one is a baseline, impermeable plate and the second a perforated one. An experimental investigation is carried out for a turbulent reattaching shear layer downstream of the two plates. The proposed setup is a model configuration to study how the plate characteristics affect the separated shear layer and how turbulent kinetic energies and large-scale coherent structures are modified. Measurements show that the perforated plate changes the mean flow field, mostly by reducing the intensity of reverse flow close to the bottom wall. Disturbance amplitudes are significantly reduced up to five step heights downstream of the trailing edge of the plate, more specifically in the recirculation region. A loudspeaker is then used to introduce phase-locked, low-amplitude perturbations upstream of the plates, and phase-averaged measurements allow a quantitative study of large-scale structures in the shear-layer. The evolution of such coherent structures is evaluated in light of linear stability theory, comparing the eigenfunction of the Kelvin–Helmholtz mode to the experimental results. We observe a close match of linear-stability eigenfunctions with phase-averaged amplitudes for the two tested Strouhal numbers. The perforated plate is found to reduce the amplitude of the Kelvin–Helmholtz coherent structures in comparison to the baseline, impermeable plate, a behavior consistent with the predicted amplification trends from linear stability.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.This work deals with the feedforward active control of velocity fluctuations over incompressible 3D boundary layers. Two strategies are evaluated, the Linear Quadratic Gaussian (LQG) controller, built using the eigensystem realization algorithm (ERA), is compared to a wave-cancellation scheme, obtained via the direct inversion of the frequency-domain transfer functions of the system. For the evaluated cases, it is shown that LQG leads to a wave-cancelling signal of the incoming Tollmien-Schlichting wavepacket. Such result allows further insight into the physics behind the active control of convectively unstable flows permitting, for instance, the optimization of the transverse position for actuation via a linear stability approach.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.This work deals with the characterization of the control of convective wavepackets, typical of the initial stages of transition to turbulence, using the Kuramoto-Sivashinsky equation [1] as a model problem representative of the transitional 2D boundary layer. Its simplified structure and reduced order provide a manageable framework for the study of fundamental concepts involving the control of linear wavepackets. The objective of this paper is to explore how the sensor-actuator placement interferes in the control problem. This is carried out by evaluating errors of the optimal estimator at positions where control gains are significant. Results show, in quantitative manner, why some choices of sensor/actuator placement are more effective than others for flow control.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.The present work considers control of perturbations in the boundary layer over a flat plate by means of adaptive methods. In particular, we focus our attention on a control law based on a multi-input-multi-output (MIMO) filtered-x least-mean-square (fxLMS) adaptive algorithm. The studies are performed through direct numerical simulations. The perturbation field studied here mimics those generated by freestream turbulence with different amplitude and scales. Plasma actuators and shear-stress sensors are considered to mimic a real case scenario.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.In the present work, we investigate efficient placement of sensors and actuators for closed-loop control of boundary-layer flows. The focus of this work is on the transitional flow cases where perturbation field is dominated by streaks. This is done using a reduced-order model based on resolvent analysis, an approach that also allows us to analyse the sensitivity of the flow response to control. A numerical sensitivity analysis was performed in this first approach, leading to conclusions about best choices of velocity components to be sensed and directions to be forced. Afterwards, we compared the performance between gaussian and shear sensors at the wall, focusing on the damping of the first resolvent gain using these devices. We close the work with the analysis of a plasma actuator, a configuration closer to standard choices for this kind of problem in both simulations and experiments.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved. Turbulent flow over a NACA 4412 airfoil with an angle of attack AoA = 5 ◦ was analysed using an incompressible direct numerical simulation (DNS) at chord Reynolds number of Re c = 4 · 10 5 . Snapshots of the flow field were analysed using the method of Spectral Proper Orthogonal Decomposition (SPOD) in frequency domain, in order to extract the dominant coherent structures of the flow. Focus is given to two-dimensional disturbances, known to be most relevant for aeroacoustics. The leading SPOD modes show coherent structures forming a wavepacket, with significant amplitudes in the trailing-edge boundary layer and in the wake. To model coherent structures in the turbulent boundary layer, the optimal harmonic forcing and the associated linear response of the flow were obtained using the singular value decomposition of the linear resolvent operator. The resolvent analysis shows that the leading SPOD modes can be associated to most amplified, linearised flow responses. Furthermore, coherent structures in the wake are modelled as the Kelvin-Helmholtz mode from linear stability theory (LST).

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.Unstable flows can be classified as absolutely unstable, when perturbations grow throughout the domain, and convectively unstable, where amplified perturbations are convected downstream, the flow locally returning to its equilibrium position. Absolute instabilities can be understood as a feedback loop, which can be long-ranged, as in impinging jets, or local, as in wakes and hot jets. Local feed-back mechanism involves an upstream- and a downstream-traveling mode. It is well know in the literature that in sheared flows the latter is typically a Kelvin-Helmholtz mode; however little is found on the former. Inspired by recent findings in high Mach subsonic jets, that identified trapped acoustic waves in the jet core, we examine the role of such acoustic modes on the stability of jets and wakes. Using a Double Vortex-Sheet (DVS) model, we derive conditions for which these flows behave as wave-guides, emulating acoustic ducts. We show that the upstream-traveling mode that leads to absolute instability is acoustic in essence, explaining differences in hot jets (symmetric) and cold wakes (antisymmetric) instabilities. Moreover, to evaluate the occurrence of such acoustic modes in turbulent flows, two-point correlations for a 0.4 Mach jet LES are constructed, highlighting that upstream influence in the flow is due to an acoustic mode. This novel way to understand jet and wake instabilities can lead to novel control methods which can be used, for instance, to reduce aircraft noise and drag, and minimize cyclic loads in civil and maritime structures, and might be expanded as to explain other jet/wake behaviors, as instability trends with compressibility and with instability modes other then than Kelvin-Helmoltz.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.In this work we deal with the problem of trailing edge noise scattered by a flat elastic plate. We use a model based on a boundary element method that couples the acoustic problem with the fluid-structure interaction and takes into account structural damping. The solution is obtained using the modal basis of the free vibration problem. The objective of this paper is to expand the acoustic scattering analysis for different damped plates to increase knowledge about the effects of structural damping and to identify potential benefits of using inherently damped structures, such as viscoelastic materials. It is found that there is a range of damping coefficients, capable of reducing peaks in the acoustic spectra associated with structural resonance, while mantaining the reduction of scattered sound due to elasticity. When the damping coefficient is increased above this range, the rigid-plate limit is recovered and acoustic benefits are reduced. The present results allow the selection of optimally-damped structures with respect to acoustic radiation.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.An experimental investigation has been undertaken to study the wavy leading edge phenomena on rectangular wing of aspect ratio 4 with a NACA 0020 airfoil at Reynolds number range from 700,000 to 3,000,000. Force measurements for various shapes of sinusoidal leading edge indicate smaller amplitude and shorter wavelength configuration (A3λ11) presenting a substantial increase in aerodynamic performance at entire range of Reynolds number tested when compared to baseline configuration, as result achieving 28.3 % of increasing in maximum lift coefficient. Oil flow visualizations reveal that tubercles with smaller amplitude have the role of delaying trailing edge flow separation. At high angles of attack, the A3 λ 11 configuration is shown to present spanwise wavelengths for which the optimal generation of streaks in turbulent boundary layers is expected according to previous experimental works. The appearance of such streaky boundary layers is a possible reason for the delay in flow separation and increase of maximum lift coefficient.

© 2018, Journal of Aerospace Technology and Management. All rights reserved.The flow patterns over a finite square cylinder of aspect ratio of 3 were analyzed experimentally in a subsonic wind tunnel using the time-resolved particle image velocimetry (TR - PIV) techniques. The near wake flow structures and vortex shedding characteristics were investigated using mean flow analysis, spectral analysis and proper orthogonal decomposition (POD). The cylinders were fixed on a elliptical leading edge flat plate, creating a boundary layer which interacted with the cylinder wake. The 2D PIV measurements were conducted at a low horizontal plane, z/h = 0.3, to investigate possible boundary layer interactions. Due to the complexity of the phenomena, the flow was characterized both in terms of average behavior and time-resolved velocity fields. Both symmetrical and anti-symmetrical vortices structures occur in the cylinder wake, which can be identified based on the coefficients of the first four POD modes. The results indicated that the alternating Karman vortex structures are dominant, described by the first two POD modes.

© 2018 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.The dominant acoustic radiation from turbulent jets has been associated with coherent wavepacket structures in the core. Predictive models for jet noise are therefore often designed using the statistics of decomposed coherent fluctuations, which display wavepacket attributes. In the absence of a universal definition for the wavepacket component of fluctuations, there exist various approaches to educe wavepackets using different techniques, such as azimuthal and/or proper orthogonal decompositions, on variables including pressure and velocity. This yields distinct models that differ from each other. In this work, we suggest a candidate field, comprised of the irrotational and isentropic component of momentum fluctuations, termed the acoustic component/mode, to obtain wavepacket statistics. We test the statistical properties of this mode to show that it reproduces wavepacket statistics known to be crucial for acoustic field modeling, and smoothly degenerates to the pressure field (scaled by the ambient speed of sound) outside of the turbulent core. A Large-Eddy Simulation of a turbulent Mach 0.9 jet is considered. The acoustic component extracts the wavepacket form of turbulent momentum density in the turbulent jet by effectively filtering out the high-energy hydrodynamic fluctuations. Wavepacket properties, including local spatio-temporal coherence and radiative efficiency, are demonstrated through several statistical analyses. Cross-spectral-density maps and amplitude envelopes of the acoustic mode show higher spatio-temporal coherence than axisymmetric components of raw fluctuations, which are typically used to define traditional wavepacket structures. The fluctuation amplitude of the acoustic mode scales directly according to a homogeneous wave propagator. Furthermore, compared to the raw pressure fluctuations, it optimally reconstructs the near and farfield acoustic radiation. The inherent difference between the acoustic mode and the pressure field is related to the distribution of phase speeds: at all jet Mach numbers, the former successfully filters out the convective hydrodynamic component, thus correctly isolating those components that are efficient at radiating sound.

© 2018 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.A study of the influence of the incidence angle in the acoustics of installed jets is presented here. Acoustic measurements of turbulent jets in the vicinity of a _at plate, mimicking a neighbouring wing, were compared to results from two models previously studied in the literature, both based on a wavepacket source: the Tailored Green's Function method, which considers the radiation of the turbulent structure in the vicinity of a semi-infinite flat plate, and the Boundary Element Method, which can represent the full geometry of the plate used in the experiments. Particular interest is given to analysing how the angle of attack of the plate affects the sound radiated by this installed jet configuration. The results herein confirm the behaviour identified by the said models: the scattered acoustic field follows the rotation of the plate, shifting the silence region and creating regions with lower noise levels in positions that, for an aircraft with engines under its wings, correspond to the ground. The robustness of this phenomenon is assessed by means of a Mach number analysis with the experimental approach, showing that this trend is present whenever the acoustic scattering is dominant.

© 2018 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.This work presents a study of acoustic scattering by 3D elastic plates made of composite materials. A fast multipole boundary element method is employed to solve the Helmholtz equation subject to boundary conditions consisting of the vibration of the elastic plate. Such boundary conditions are obtained by the solution of a structural modal basis which satisfies the free vibration problem of plates composed of orthotropic materials. The fluid-structure interaction problem is coupled through the linearized Euler equation. An important difference between the composite and aluminum plates is observed in terms of the specific mass, which impacts the fluid-structure coupling. Results demonstrate that the higher frequency propagation of bending waves along composite plates leads to a further noise reduction when compared to elastic aluminum plates. Solutions obtained by twodimensional plates are compared to those obtained by fully three-dimensional ones. It is shown that the 2D models of composite plates cannot recover the directional aspects of trailing-edge noise scattering by 3D plates due to the spanwise effects of propagation of bending waves that impact on the acoustic solution.

© 2018 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.The proximity of the source and an edge can make the acoustic scattering by wings a significant source of aerodynamic sound. Theoretical results have shown that elastic edges lead to reductions of acoustic scattering; however, experimental confirmation of theoretical trends is difficult, since surface vibrations modify both the source structure and the scattering properties. A simplified, controlled setting for measurements of acoustic scattering, allowing the evaluation of fluid-structure interactions, would thus be desirable to study how elastic edges modify the radiated sound. We present an experimental procedure to isolate the scattered field using a loudspeaker in the vicinity of at plates. The methodology is applied to three different plates, made of steel, aluminum and carbon fiber, as a demonstration. The responses of these elastic plates are studied for a sound source of dipole type near the trailing edge. The method is based on the experimental determination of frequency response functions between source and radiated sound for experiments with and without the plate; subtraction of results, accounting for amplitude and phase, isolates the scattered field. Experimental results treated with the developed procedure were compared with predictions made by numerical simulations performed with a Boundary Element Method (BEM), coupling the acoustic problem with the plate vibration. The comparison between experimental and numerical results revealed that a two-dimensional model can predict satisfactorily the reductions in scattered field by elastic plates observed in the experiment. The present methods can be used to support the choice between different materials for edges focusing on their respective acoustic benefit.

© 2018 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.Measurements of the sound radiated by subsonic jets with Mach numbers ranging from 0.3 to 0.9 are carried out, with a view to examining the two-point statistics of the far-field sound, and, in particular, the two-point coherence. It is seen that the cross-correlation between neighbouring microphones in a polar arc decreases with increasing Mach number. The same happens with the two-point coherence, a feature predicted by wave-packet models including jitter.1 The far-field coherence results are shown to be consistent with the mentioned wave-packet model. In particular, a collapse of coherence results for all Mach numbers is obtained once measurements are plotted as a function of the angular dependence expected by the model. The results show that the far-field is consistent with a jittering wave-packet source model, which explains the observed decrease of coherence for higher Mach numbers.

© 2018 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.Wavepackets modelling large-scale coherent structures are related to the peak noise ra- diation by subsonic jets. Such wavepacket models are well developed in the literature, and are often based on a linearization of the Navier-Stokes system; solutions of the resulting linear problem have a free amplitude, which can be obtained by comparison with experi-ments or simulations. In this work we determine amplitudes of turbulent-jet wavepackets by comparing large-eddy simulation (LES) data from Brès et al.2, 4 of a Mach 0.9 jet and fluctuation fields using the parabolized stability equations (PSE) model (Sasaki et al.18). Projection of the leading mode from spectral proper orthogonal decomposition (SPOD), applied to the LES data, onto the PSE model solutions is a way to determine the free am- plitude, and by analyzing such amplitudes for different Strouhal numbers and azimuthal modes of the turbulent jet, it is possible to notice a clear pattern of the scaling factor with varying St. Azimuthal wavenumbers m = 0, 1 and 2 show an exponential dependence of wavepacket amplitude with Strouhal number. This sheds light on how wavepackets amplitudes behave and how they are excited upstream.

© 2017, The Author(s) 2017.The main concern related to the flutter phenomenon is predicting and avoiding it. This paper describes the application of a flexural-torsional flutter testbed for acceleration reduction by applying active and passive model-based control. The model consists of the 2D typical section, with aerodynamic loads estimated by an unsteady time-domain formulation based on Wagner’s function. The active control architecture consists of a stability augmentation system with output feedback and gain scheduling via the linear-quadratic regulator theory and actuation by servomechanism. The passive control employs a shape-memory alloy to provide additional torsional stiffness. Experimental results show considerable reduction of oscillations at a relative low cost for both active and passive control strategies, and that the use of shape memory alloys in aeroelastic stability problems is promising.

© 2018 Elsevier Masson SASAircraft point-mass equations of motion have been largely adopted to calculate optimal trajectories with local aerodynamic models, i.e. valid in a restricted domain. However, some optimal maneuvers may need aerodynamic models valid for a broader range of flight conditions. For this purpose, global aerodynamic models are attractive but their nonlinear structure can preclude obtaining optimal trajectories by an indirect method together with the point-mass equations of motion. To solve this impasse without resorting to direct methods the authors propose a new set of aircraft equations of motion. When compared to the point-mass equations, the proposed set permits the inclusion of the angular velocity in the evaluation of aerodynamic forces, making them more accurate. Another advantage of the proposed model over the point-mass one is that it allows a qualitative estimate of the control surface deflections after the trajectory is obtained, which enables to discard solutions with infeasible deflections. To verify consistency, the proposed equations of motion are compared by simulation to the point-mass and to the rigid-body equations. The use of the proposed set of equations is demonstrated by three optimizations of a 360∘ roll problem.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All right reserved.The interest in the class of unmanned vehicle known as High Altitude Long Endurance aircraft has been growing in the latest years. In this paper, stability problems associated with flight control law design for flexible aircraft are evidenced. A fuzzy-based gain-scheduling approach is proposed to adequate closed-loop response. The application of the technique was demonstrated for the flexible X-HALE aircraft and compared to classical interpolation-based gain-scheduling techniques. Nonlinear simulation results revealed that fuzzy-based gain-scheduling is promising for flexible aircraft control.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.PIO (Pilot-Induced Oscillations) phenomena have been widely explored over the past recent years and led to the development of mathematical models to describe human pilot behavior as well as frequency domain analysis criteria. However, both these pilot models and prediction criteria have been developed neglecting the influence of airframe flexibility. Since aircraft are becoming more flexible, this influence has to be considered during the development of fly-by-wire systems. In this paper, we address the effects of aeroelastic dynamics in aircraft handling qualities analysis using an adequate representation of the aircraft flight dynamics as a flexible body and mathematical pilot models.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.The advantages of full-state feedback adaptive control in dealing with uncertainties of a flexible aircraft model are demonstrated with the use of model reference adaptive control. Design of an output-feedback system with an observer, based on the separation principle, is attempted. Differences in both stability and performance characteristics of the full-state feedback and the output-feedback closed-loop systems demonstrate that further investigation is needed to design adaptive output-feedback controllers.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.Flight simulation of flexible aircraft is computationally expensive. This paper presents an approach based on reduced-order models for computational cost reduction of the aeroelastic equations. The model order reduction technique, the X-HALE aircraft and a low computational cost model are described. Finally, simulation time histories are presented comparing time responses and computational costs. Numerical results show good agreement between full-order and reduced-order models, with the latter presenting a significant reduction in computational time.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.This paper presents a new concept on pilot model that allows the study of handling qualities and PIO (Pilot-Induced Oscillations) of elastic aircraft since it computes not only the voluntary pilot inputs in order to accomplish a given task, but also the involuntary commands due to the biodynamic feedthrough (BDFT) or Pilot-Assisted Oscillations (PAO) phenomena. Frequency-domain criteria used for PIO prediction are analyzed and pilot simulations are also presented.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.To stabilize a very flexible wing with a control system it is necessary to feedback wing measurements such as accelerations, deformations or displacements. In a previous work, displacement sensors were positioned at the wing tips and then the gain matrix of the feedback control was optimized. In this way, the performance of the control is restricted to the predetermined position of the sensors. Hence, in this paper we apply another methodology to simultaneously optimize the sensors positioning and the gain matrix. The results are compared in order to evaluate the benefits of this methodology in the considered problem.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.This article presents the development of a real-time flight load measurement system convertible to real-time flight geometry measurement. It uses already known full bridge strains gages in a different manufacturing possibility: inside composite layers before resin cure. The manufacturing process is validated using a composite bar prototype. The prototype is submitted to a four points structural test in order to validate the measurements and influences of the manufacturing process. The whole process is applied to X-HALE aircraft disclosing a composite built-in measurement system for real-time flight load and flight geometry.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.The assumption of small deformations in the formulation of the flight dynamics of flexible aircraft can be very convenient as it allows the use of a reduced number of modes of vibration to represent the structural dynamics with little loss of accuracy. However, depending on the level of structural flexibility, deformations may become large enough to violate this simplifying assumption, making geometrically-nonlinear formulations necessary. Delimiting the range of validity of small deformations is then indispensable for the flight-mechanics engineer in state-of-the-art aircraft design. In this paper, small- and large-deformation formulations are compared in equilibrium conditions and in time-marching simulations for aircraft with different levels of structural flexibility. The importance of geometrical nonlinearities and the range of validity of small deformations are assessed.

© 2018 Elsevier B.V.Amorphous carbon thin films were grown by magnetron sputtering on crystalline Si and fluorine-doped tin oxide (FTO) substrates and annealed at 600 °C in vacuum. Subsequently, the films were subjected to SF6 plasma nanotexturing processes using different secondary gases such as H2, O2, and Ar. The samples were characterized by profilometry, atomic force microscopy, Raman spectroscopy, FTIR spectroscopy, and contact angle measurement. The samples have shown nanostructured surface patterns that strongly depended on the secondary plasma gas used (H2, O2, or Ar); the films subjected to the SF6 + Ar plasma nanotexturing presented the highest surface roughness. Investigation of the atomic structure indicated that the annealing process is responsible for a significant increase in sp2 hybridization of C. The contact angle measurement results have revealed the hydrophilic to hydrophobic transition owing to the annealing process. In contrast, super hydrophilic behavior was observed after the plasma nanotexturing processes. The increase in both the surface roughness and hydrophilicity of these nanotextured carbon thin films are highly desirable characteristics for their application as counter-electrodes in dye-sensitized solar cells and batteries.

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature.The authors regret an error in the Experimental section of the published article:

© 2018 by the authors. Licensee MDPI, Basel, Switzerland.This work aimed to enhance the creep resistance of Ti-6Al-4V alloy treated by plasma nitriding. The nitriding was performed on specimens with a Widmanstätten microstructure for four hours at 690°C under a gas atmosphere containing Ar:N2:H2 (0.455:0.455:0.090). X-ray diffraction analysis showed that the ε-Ti2N and δ-TiN formed on the nitrided sample, in addition to the α-Ti and β-Ti matrix phases. The layer thickness of this sample was about 1 µm. Hot tensile tests were performed in the temperature range of 500 to 700°C on nitrided and non-nitrided samples, which indicated an increased strength of the nitrided samples. The same temperature range was used for the creep tests in a stress range of 125 to 319 MPa. The plasma-nitrided samples exhibited better creep resistance when compared to the untreated samples. This result was demonstrated by the decreased secondary creep rate and the increased final creep time. This improvement in the creep resistance appeared to be associated with the formation of the nitrided layer, which worked as a barrier to oxygen diffusion into the material and due to the formation of a surface residual compressive stress.

© 2017, Springer-Verlag GmbH Germany.Plasma-treated carbon thin films are investigated as counter electrodes for dye-sensitized solar cells. The films were grown onto fluorine-doped tin oxide (FTO) substrates by magnetron sputtering using pure graphite target and argon atmosphere and subsequently annealed at 600 °C for 30 min in vacuum. These films were then submitted to a plasma texturing process in a reactive ion etching reactor using three different gas combinations: sulfur hexafluoride/argon (SF6 + Ar), sulfur hexafluoride/hydrogen (SF6 + H2), and sulfur hexafluoride/oxygen (SF6 + O2). The morphology and structure of the obtained films were characterized by scanning electron microscopy and Raman spectroscopy. Cyclic voltammetry technique allowed accessing the improvements in their catalytic properties, while the photocurrent-voltage curves under simulated solar illumination AM 1.5G (100 mW/cm2) evaluated the performance of the respective assembled solar cells. The results show that photovoltaic performance is significantly affected by the different plasma texturing conditions used. The carbon counter electrode obtained after SF6 + O2 plasma texturing achieved the best power conversion efficiency of 2.23%, which is comparable to the 2.31% obtained using the commercial platinum counter electrode.

Copyright © 2018 by ASME.This work describes a methodology used for counter-rotating (CR) propellers performance estimation. The method is implemented in an in-house program for gas turbine performance prediction, making possible the simulation of the counter-rotating open rotor (CROR) architecture. The methodology is used together with a variable geometry compressor control strategy to avoid surge conditions. Two cases are simulated under transient operation for both fixed and variable geometry compressor. The influence of the variable geometry control on the transient performance of CROR engines is evaluated and a comprehensive understanding on the transient behavior of this type of engine could be obtained. It is shown that the use of the variable geometry compressor control does not significantly affect the overall engine performance, while avoiding the surge conditions, thus ensuring the engine operation safety.

© 2018 Elsevier Inc.This paper reports the development and convergence analysis in steady-state of an effective and robust implicit finite-volume solver for compressible Euler equations on three-dimensional unstructured grids. A second-order upwind scheme (MUSCL) was employed based on Roe's approximate Flux-Difference Scheme (FDS) by using Venkatrakishnan flux limiters. The construction of the linear system for the implicit scheme was performed by applying the backward Euler on the left-hand side of the conservation equation and Newton-type linearization on the right-hand side. The Jacobian matrix that resulted from the linearization process was computed analytically using Roe flux terms. In this phase, the defect-correction technique was employed allowing effective time-dependent computations by an implicit time-integration scheme. In this approach, the flux integral on the right-hand side is computed based on a high-order of accuracy whilst the left-hand side the Jacobian is performed based on the low-order. The resulting sparse and large system of linear equations is solved by a sequential Gauss–Seidel iterative method. Simulations were performed and the developed implicit defect-correction solver was validated and verified. In addition, convergence analysis comparing the implicit solver and the explicit Runge–Kutta of 5-steps using Implicit Residual Smoothing (IRS) were performed showing the significant speed-up of the implicit solver over the explicit one. Simulations were performed for case studies to demonstrate the robustness of the developed implicit defect-correction solver in solving typical problems of aerodynamic involving transonic condition and shock wave captures for internal and external flows. Finally, the main particularities of the implicit scheme were investigated and discussed considering the simulation results, showing also its capacity to serve as an effective preconditioner (start-up method) to other implicit techniques.

© 2018 by ASME.This paper describes a methodology used for propeller performance estimation, which was implemented in an in-house modular program for gas turbine performance prediction. A model based on subsonic generic propeller maps and corrected for compressibility effects, under high subsonic speeds, was proposed and implemented. Considering this methodology, it is possible to simulate conventional turboprop architectures and counter-rotating open rotor (CROR) engines in both steady-state and transient operating conditions. Two simulation scenarios are available: variable pitch angle propeller with constant speed; or variable speed propeller with constant pitch angle. The simulations results were compared with test bench data and two gas turbine performance commercial software packages were used to fulfill the model validation for conventional turboprop configurations. Furthermore, a direct drive CROR engine was simulated using a variable inlet guide vanes (VIGV) control strategy during transient operation. The model has shown to be able to provide several information about propeller-based engine performance using few input data, and a comprehensive understanding on steady-state and transient performance behavior was achieved in the obtained results.

© 2018, The Brazilian Society of Mechanical Sciences and Engineering.The association of turbochargers with piston engines is widespread since both the efficiency and the power output of an engine could be improved. However, a piston engine operational range is wide and highly variable. This characteristic imposes challenges for the project and application of a turbocharger that should perform properly within the operational range. An important tool used to evaluate the performance of both turbine and compressor, which compose a turbocharger, is the characteristic map. The map condenses the main performance parameters into a single graphic that allow the evaluation of the machine characteristics, such as the operational width. A typical characteristic map relates the pressure ratio, mass flow rate, rotation and efficiency for each operational condition. The present work provides a technique to obtain the characteristic map of a turbocharger centrifugal compressor with reduced time consumption through steady state simulation using a fully unstructured mesh. Evaluation of the results indicated good accuracy for the predicted mass flow rate and pressure ratio. However, the resulting efficiency presented considerable discrepancy, which was aggravated when simulating extreme operational conditions or when the mass flow was used as a boundary condition. At last, the porter shroud and volute were evaluated within the entire range to provide an insight into the compressor operation.

© 2018, The Brazilian Society of Mechanical Sciences and Engineering.Advances in turbofan engine technology have led to engines with growing bypass ratios and lower fan pressure ratios, increasing the complexity of the in-flight thrust determination. Thrust values cannot be directly measured in flight; therefore, ground-level test are carried out, and the results calculated from thermodynamic properties of the gas are compared to the force exerted by the engine on the test bench. The result of this comparison is a scalar that is applied to the fan pressure ratio, fan pressure correlation, which attempts to minimize the error between the measured and calculated values. After the thermodynamic properties of the gas are measured during in-flight tests and together with the fan pressure correlation are used to calculate the in-flight thrust. The calculation procedure is implemented through VISUAL BASIC scripts, in the MICROSOFT EXCEL® environment. These scripts are used to calculate the generated thrust and the mass flow that go through the engine from the thermodynamic properties of the gas obtained from a high-fidelity numerical simulation of this engine. These results are then validated against the thrust and mass flow values calculated by this model. An analysis of the free-stream suppression effects on thrust is carried making use of these scripts.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.The pursuit of lower fuel consumption for aircraft is promoting a departure from contemporary arrangements. One example is the development of more synergetic airframe and propulsion system designs, which are expected to increase significantly aircraft efficiency mainly by means of boundary layer ingestion. By integrating propulsion and airframe, both systems will significantly impact each other. This mutual interference requires the development of novel performance evaluation methods that consider such effects. This manuscript introduces a propulsive efficiency equation for boundary layer ingestion propellers based on the power balance method. Two formulations are presented for numerical and analytical evaluations. The equation is bounded between 0 and 1 and allows a meaningful evaluation of shaft to propulsive powers conversion, which results in an accurate determination of thrust and drag. This manuscript is the first advance of a project that will develop an optimizing tool for boundary layer ingestion propellers based on computational fluid dynamic simulations. The results will be presented in subsequent manuscripts.

© Copyright 2018 ASME.Boosters are commonly used in liquid propellant rocket engines (LPRE) to allow lower propellant pressures in their storage tanks and, thus, smaller structural masses, contributing to cavitation free operation in the subsequent main turbopumps (TP). Boosters can be identified as key components for the overall performance of large engines, and if their operating requirements are stringent, they can operate under cavitation. Thus, effective design and performance tools are fundamental to design the components of these boosters considering this phenomenon. The simulation techniques based on turbulent and multiphase 3-D Computational Fluid Dynamics (CFD) were used in this work at steady state regime. The simulations were done using the commercial software CFX from ANSYS® Workbench. The study was conducted analyzing the performance of the first stage of the hydraulic axial turbine of the liquid oxygen (LOX) booster of the Space Shuttle Main Engine (SSME), at various operation points under cavitation, considering 3.0% tip clearance relative to blade height. The results obtained for, the performance parameters of this stage were compared with those obtained through monophase simulation, and the multiphase technique showed results closer to the experimental ones around the design point (DP), with increased simulation times acceptable for the computational resources currently available. Moreover, the results from the current work show the importance of considering the effects of cavitation through multiphase flow in hydraulic turbines.

Copyright © 2018 ASME.In modern gas turbine engines, many sophisticated cooling schemes are used to maintain the turbine blade temperature in acceptable levels. These schemes, such as convective cooling, film cooling, impingement cooling and the use of pin fins, can be combined to increase the cooling effectiveness. Jet impingement cooling, pin fins and convective cooling are internal cooling techniques, in which the cooling is achieved based on coolant flow through internal blade channels decreasing the blade metal temperature. Film cooling is an external cooling technique, in which the cold fluid (air) is injected into the hot gas flow through discrete holes providing a coolant film at blade surface, protecting the blade metal. In this way, the present work refers to the numerical investigation of internal and external cooling strategies applied in gas turbines. The methodology developed to analyze such strategies is based on the flat-plate approach with laboratory length scales and Computational Fluid Dynamics (CFD) techniques, being the flow, in the study domain, considered viscous, turbulent and compressible. A commercial CFD program is used to solve the general equations of fluid mechanics with Reynolds Average Navier-Stokes (RANS) technique for steady state regime and Shear Stress Transport (SST) turbulence model to determine the flow eddy viscosity. The combined effects of internal and external cooling is studied through a highly sophisticated scheme, called louver, which combines the effects of impingement and film cooling. Pin fins and ribs turbulator geometries applied in the channel between the impingement and the film cooling have the purpose of evaluating the impact of these geometries on the film cooling effectiveness over the flat surface in comparison to the louver scheme without turbulator. This study concluded that, pin fins proved to be the most promise solution because they increased in 7% the film cooling effectiveness. Ribs also have a good potential to increase the effectiveness, because an increase of 4% in film cooling effectiveness was observed. In addition, the effects of the turbulator are dependent on their location, since the turbulator positioned near the film cooling hole exit showed improvements in the film cooling effectiveness in relation to the turbulator near of the impingement cooling jet.

© 2018, Journal of Aerospace Technology and Management. All rights reserved.This article describes the run time characteristics of a gas turbine performance simulation using different solvers and components off-design performance database formats. Two different nonlinear systems of equation solvers, Newton-Raphson’s and Broyden’s, and two different formats of compressor and turbine off-design performance database (maps), tabulated values and fitted surface equations, were compared. Based on the results it is then possible to trade off and select the most appropriate combination of solver and component map type for the gas turbine performance simulation for real-time application.

Copyright © 2018 by ASME.A laser-induced fluorescence (LIF)-based nitric-oxide flow-tagging technique was applied to measure both velocity and NO lifetime in a hypersonic shock tunnel from two experimental test runs. The results were supported by an analytical profile proposed in this paper that provides a way to correct velocity measurements under unknown systematic error sources. This procedure provided velocities with discrepancies lower than 3% for a total of five measurements, and lower than 2% when compared with that obtained from a linear fit. Additionally, the comparison between the proposed and experimental profiles allowed us to obtain the fluorescence NO lifetime from only one image.

© 2018 IEEE.Shape memory alloy (SMA) wires have extensive use in many areas of the industry nowadays and its development continues reaching new applications as studies progress. This paper proposes a SMA measurement device that uses affordable components, such as the Arduino micro-controller and a LabVIEW programming language interface. With an antagonistic mechanism design, data on temperature, strain and stress is acquired to confirm the measuring capabilities of the full equipped instrument, rendering visualizations of phase transformations and opening way for further development in control and detailed acquisition of shape memory alloy wire properties.

© 2018 IADIS Press. All Rights Reserved.The development of transversal competences is essential for the success of engineers, who need to have the ability to adapt to the new and changing demands posed by modern society and scientific advances. It is a challenge for professors to teach and evaluate transversal competences, since such competences are related to attitudes and values. We present a program, held in an Engineering school, with the goal of motivating young people in STEM (Science, Technology, Engineering and Mathematics) areas. Results from the designed initiatives pointed to success in the development of transversal competences, including problem solving, communication, leadership, teamwork, self-management, creativity and innovation.

© 2018 IADIS Press. All Rights Reserved.Despite the technological development, the digital era, and the fact that Science, Technology, Engineering and Mathematics (STEM) permeates all the modern world, the number of students choosing to pursue a career in STEM areas is very small in comparison to other careers. In particular, considering the gender, the gap increases even more. In this work, we present an industry-university program designed to stimulate STEM education and fostering the female interest and development in these areas. Considering our female undergrad students, the proposal was to engage them in the process, as the main agents. Our students prepared and gave lectures in schools about STEM areas. Together with some faculty members, they also developed and applied workshops based on hands-on and minds-on learning activities to spark young girls’ curiosity in STEM areas. In all activities, it was performed an evaluation of learning outcomes, as STEM skills and interest. The program showed to be effective producing very positive remarks.

Copyright © 2018 by SCITEPRESS - Science and Technology Publications, Lda. All rights reserved.Engineering technical competence is an indisputable need in an engineer professional life. However, to be a complete engineer, able to work in an ever changing globalized world, but sensible to cultural differences, it is necessary more than technical skills. It is then important for students acquiring non-technical competences, such as intercultural appreciation, leadership, self management, service and civic responsibility, teamwork, and understanding of engineering ethics. Here, we present the "Women in STEM2D" Program, developed with undergraduate engineering students, whose goal is to attract and keep female students in the technological and science areas. We provide a critical analysis about how the planning and execution of the program activities contribute to the development of non-technical skills in the engineering students.

© 2018 IEEE.Typical industrial applications, which can benefit from using Micro Aerial Vehicles (MAV) take place at well-controlled environments. In this case, the MAVs can rely on a fiducial system to improve their navigation based on a reliable map of the environment. In this work, we assess the use of artificial landmarks for accurate and robust visual-inertial navigation within a controlled environment. The use of artificial landmarks presents relevant advantages over techniques that assume an unknown environment. They require less processing effort and provide more robustness for dynamic and large environments. As a result, one can employ simpler, affordable platforms enabling commercially attractive applications due to cost reduction, energy efficiency, simplicity and determinism during operation. Therefore, this work presents the design and development of an accurate and efficient visual-inertial navigation system to provide feedback information allowing low and high-level control functionalities for MAV applications.

© 2018, The Brazilian Society of Mechanical Sciences and Engineering.In this work, the authors propose a formation control strategy of a group of three multirotor aerial vehicles being able to avoid multiple obstacles and collisions. To deal with this problem, a decentralized architecture is proposed which has one model predictive controller per vehicle including a set of convex constraints on the vehicle’s position to prevent collisions with other agents and different shapes of obstacles. The resulting decentralized scheme controls the formation based on a virtual structure approach. For the purpose of avoiding collisions, each local controller considers the predicted position of every neighbor vehicles. The effectiveness of the developed scheme is demonstrated through numerical simulations considering a “figure-of-eight” as the reference trajectory, and the results show its capability to handle thrust force, obstacle and collision avoidance constraints.

© 2018 ISAThe present paper is concerned with the design and experimental evaluation of optimal control laws for the nonlinear attitude dynamics of a multirotor aerial vehicle. Three design methods based on Hamilton-Jacobi-Bellman equation are taken into account. The first one is a linear control with guarantee of stability for nonlinear systems. The second and third are a nonlinear suboptimal control techniques. These techniques are based on an optimal control design approach that takes into account the nonlinearities present in the vehicle dynamics. The stability Proof of the closed-loop system is presented. The performance of the control system designed is evaluated via simulations and also via an experimental scheme using the Quanser 3-DOF Hover. The experiments show the effectiveness of the linear control method over the nonlinear strategy.

© 2018 Elsevier LtdAmong various strategies developed for the attenuation of noise and vibration in mechanical structures, piezoelectric shunt damping, which consists in connecting piezoelectric transducers integrated in a structure to electric or electronic circuits, is a promising alternative for use in small- and mid-scale structural components. Despite the fact that the shunt damping technology has been investigated for quite a long time, it is recognized that its application to real-world structures still requires developments aiming at improving its effectiveness and range of application under unavoidable practical constraints. As a result, research on improved solutions related to piezoelectric shunt damping is still very active. Due to the very nature of the piezoelectric shunt damping, it becomes clear that further improvements must consider both mechanical and electrical/electronic aspects. Based on the current state-of-the-art, this paper provides a systematic literature review of different piezoelectric shunt damping strategies developed for the attenuation of vibration and noise in mechanical systems, including an assessment of the basic principles underlying the electromechanical behavior, as well as design procedures and numerical modeling of piezoelectric shunt damping devices applied to elastic vibrating systems. Emphasis is placed on the various types of shunt circuits, including the traditional passive resonant circuits, multimode resonant circuits, adaptive tuning circuits, switching circuits, and negative capacitance. The strategies for location and shape of the piezoelectric transducers is also discussed. A variety of applications recently reported in the scientific literature and in patents are presented. An assessment is made about more significant recent achievements and technological issues to be faced in further developments.

© 2018 IEEE.Shape memory alloy (SMA) wires have extensive use in many areas of the industry nowadays and its development continues reaching new applications as studies progress. This paper proposes a SMA measurement device that uses affordable components, such as the Arduino micro-controller and a LabVIEW programming language interface. With an antagonistic mechanism design, data on temperature, strain and stress is acquired to confirm the measuring capabilities of the full equipped instrument, rendering visualizations of phase transformations and opening way for further development in control and detailed acquisition of shape memory alloy wire properties.

© 2018 Elsevier LtdNonlinear aeroelastic systems are prone to the appearance of limit cycle oscillations, bifurcations, and chaos. Such problems are of increasing concern in aircraft design since there is the need to control nonlinear instabilities and improve safety margins, at the same time as aircraft are subjected to increasingly critical operational conditions. On the other hand, in spite of the fact that viscoelastic materials have already been successfully used for the attenuation of undesired vibrations in several types of mechanical systems, a small number of research works have addressed the feasibility of exploring the viscoelastic effect to improve the behavior of nonlinear aeroelastic systems. In this context, the objective of this work is to assess the influence of viscoelastic materials on the aeroelastic features of a three-degrees-of-freedom typical section with hardening structural nonlinearities. The equations of motion are derived accounting for the presence of viscoelastic materials introduced in the resilient elements associated to each degree-of-freedom. A constitutive law based on fractional derivatives is adopted, which allows the modeling of temperature-dependent viscoelastic behavior in time and frequency domains. The unsteady aerodynamic loading is calculated based on the classical linear potential theory for arbitrary airfoil motion. The aeroelastic behavior is investigated through time domain simulations, and subsequent frequency transformations, from which bifurcations are identified from diagrams of limit cycle oscillations amplitudes versus airspeed. The influence of the viscoelastic effect on the aeroelastic behavior, for different values of temperature, is also investigated. The numerical simulations show that viscoelastic damping can increase the flutter speed and reduce the amplitudes of limit cycle oscillations. These results prove the potential that viscoelastic materials have to increase aircraft components safety margins regarding aeroelastic stability.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The active control of aeroelastic flutter panel and optimization of the best placement location of the piezoelectric patch is evaluated in composite tow steered laminates. The aerodynamic model is based on potential supersonic flow piston theory. The structural model based on Ritz method is used to represent the tow steered composite laminate and the PZT transducers. Classical lamination plate theory and symmetric stacking sequence are used and the fiber trajectories are defined by Lagrange interpolation functions. The control system is designed using the proportional-derivative feedback approach, resulting in active damping and stiffness effects. The flutter stability boundaries for optimal tow steered composite laminates layups and optimal active steered laminate (using piezoelectric patch) are numerically compared to quantify the benefits of active control system. The instability analysis varying the proportional feedback gains is also investigated. The position and size of the patch and tow steered paths are optimized using a differential evolution algorithm to increase the aeroelastic instability margin.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The continuous search for aircraft flight performance to obtain lower fuel consumption leads to the optimization of wings shape and structure focused in the longer flight phase of its mission, the cruise phase. However, this leads to a loss of efficiency for other flight phases such as take-off and landing, resulting in the need for high-lift surfaces, that are basically triggered by electro-mechanical or hydro-mechanical actuators, adding a considerable amount of weight, complexity and cost to the design project. New concepts of aircraft have wing solutions that are optimized for every flight phase and, consequently, are capable of adjusting their structures in order to achieve the best performance on each flight situation. One of the main ideas on how to get this result is the implement of morphing wings by using smart actuators. Shape memory alloys are classified as smart materials and they can be used in order to develop light, simple and cheap solutions to obtain controlled modifications on aircraft aerodynamic surfaces. This paper focuses on evaluating the airfoil thickness effects on morphing wings composed by memory alloy actuators capable of camber adjustment. In order to achieve this goal, the morphing NACA 0020 designed for the present project is compared to a morphing NACA 0012 wing prototype. The fact that previously mentioned prototypes have different airfoil thickness promotes the ideal environment to investigate this effect on the performance of morphing wings capable of camber adjustment. In addition, each previously mentioned morphing wing prototype was compared to its traditional flap configuration to investigate the aerodynamic pros and cons related to this morphing mechanism. The comparison shows that despite the morphing wing as studied resulting in a lower performance, it’s design simplicity and weight reduction brings advantages to the whole aircraft in certain conditions.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.This paper presents a numerical investigation of the effects of parametric uncertainties propagated through Polynomial Chaos Expansion on the design of a Receptance-based active controller for aeroelastic systems. The test-case is representative of an experimental rig featuring a subsonic flexible wing with multiple control surfaces. The uncertainty is introduced in the Young's modulus of the main spar. Such uncertainty is firstly propagated to assess the open loop behavior of the aeroelastic system in terms of flutter velocity and frequency responses. A Receptance-based controller is then designed deterministically with the goal of increasing the flutter boundary and its performance is tested against the uncertain aeroelastic system. Finally, the PDFs of the receptance control gains are evaluated and discussed.

© Proceedings of ISMA 2018 - International Conference on Noise and Vibration Engineering and USD 2018 - International Conference on Uncertainty in Structural Dynamics. All rights reserved.In composite materials, previous studies show that carbon-fiber reinforced polymers (CFRP) can be designed in terms of damping characteristics by acting on its physical and geometric features. In recent years, the development of automatic fiber placement (AFP) allows the realization of variable stiffness composite laminates (VSCL), among which tow steered composites are considered very promising. Therefore, the objective of this paper is to present a numerical assessment of the influence of fiber steering on the modal damping of CFRP plates for different fiber trajectories. The dynamic model is derived by using a semi-analytical approach based on the combination of the Classical Lamination Theory with the Rayleigh-Ritz (Assumed-Modes) approach. The modal damping factors are calculated using the Strain Energy Method, which is based on the ratio between the stored and the dissipated energies, giving the specific damping capacity (SDC) for each vibration mode.

© Proceedings of ISMA 2018 - International Conference on Noise and Vibration Engineering and USD 2018 - International Conference on Uncertainty in Structural Dynamics. All rights reserved.It has been shown in the literature that temperature variations can induce modifications of the static and dynamic characteristics of beam-like and plate-like structures, due to the so-called stress-stiffening effect. In most cases of practical interest, temperature variations associated to environmental and operational conditions are very difficult to control and can be rationally considered as random quantities. In this context, the present paper addresses the propagation of uncertainties affecting the temperature on the natural frequencies of thin rectangular plates. A Rayleigh-Ritz-based dynamic model is first derived for the bending vibrations of plates, accounting for the presence of thermal stresses. This model is combined with a Karhunen-Loève expansion (KL), used to discretize the temperature distribution, which is modeled as a Gaussian random field. The results enable to quantify the influence of temperature randomness on the thermal stresses, and evaluate the sensitivities of the natural frequencies with respect to such randomness.

© Springer International Publishing AG, part of Springer Nature 2019.In the last years, many techniques and procedures have been employed to optimize traditional composite laminates, which can be classified as constantstiffness composite laminates (CSCL), since the local stiffness is independent on the position over the laminate. On the other hand, recent advances in manufacturing processes now enable to explore non conventional designs. In particular, the development of automatic fiber placement allows the realization of variable stiffness composite laminates (VSCL), in which the local stiffness varies over the laminated as intended by the designer. In practice, VSCL can be achieved by making the fibers follow curvilinear trajectories over the plies (tow steering), or varying the matrix/fiber fraction over the laminate. Some authors have explored the benefits of VSCL to improve the performance of composite laminates in terms of stress distributions, static deformations, buckling, dynamic behavior and aeroelastic stability. In this context, this work proposes a strategy to optimize tow steered rectangular plates by controlling the angles that define the fiber trajectories. These latter are described by Lagrange polynomials of different orders, and two different sets of boundary conditions are considered. A structural model based on the Ritz method, combined with the classical lamination theory to model the composite laminate are used. The plate is considered thin, being modeled based on Kirchhoffs hypotheses. The equations of motion are obtained from Lagrange equations. The proposed model is validated by comparing natural frequencies and mode shapes with the counterparts obtained by using Nastran finite element software. The model is also validated by using experimental results obtained from a tow steered plate manufactured by the automatic fiber placement. A convergence analysis is carried-out to determine the number of functions in the Ritz basis necessary to ensure convergence of the semi-analytical model. A differential evolution (DE) algorithm is used to maximize the first natural.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Optimization of wing shapes has been a constant struggle throughout the years of aircraft and aerodynamic development. Innovations have flourished in all scientific fields that influence wing design, such as materials, structural, manufacturing and aeronautical engineering, in order to improve performance and consequently reduce fuel consumption of aircraft, which translates in a light wing with an airfoil shape that assures the best lift coefficients required for a specific mission. On the other hand, this penalizes other maneuver possibilities for the same aircraft, hindering its capabilities and demanding development of different solutions, impacting on costs and draining resources. An “one fits all” concept solves this hurdle, since one design could accomplish a variety of missions, with adequate values for lift coefficient for each different flight phase. This concept can be achieved by wings capable of morphing, adjusting their structures on demand. One widely investigated field of research is morphing wings that uses smart materials, such as shape memory alloys, for actuation. Shape memory alloys are lightweight, simple and cheap materials that, combined with a morphing compliant rib, can achieve controlled displacements on aerodynamic surfaces. This paper analyses different rib concepts modifying chordwise positions for actuation by making use of shape memory alloy wires built-in a NACA 0012 reference wing. A comparison is made between different percentages of chordwise morphing capability and a simple NACA 0012 wing with a 25 percent chord plain flap, as usually seen on many simple aircraft designs. The results show an increase on lift coefficient values and a delay of stall angle for some chordwise actuation locations. The comparison parameter was a 15 degree of trailing-edge tip displacement related to the airfoil leading-edge. By reducing external surface gaps and steps, a simple and lightweight smart morphing wing can overcome a common flap design and still achieve a variety of different missions by adjusting itself in flight.

© 2018 Elsevier B.V.Amorphous carbon thin films were grown by magnetron sputtering on crystalline Si and fluorine-doped tin oxide (FTO) substrates and annealed at 600 °C in vacuum. Subsequently, the films were subjected to SF6 plasma nanotexturing processes using different secondary gases such as H2, O2, and Ar. The samples were characterized by profilometry, atomic force microscopy, Raman spectroscopy, FTIR spectroscopy, and contact angle measurement. The samples have shown nanostructured surface patterns that strongly depended on the secondary plasma gas used (H2, O2, or Ar); the films subjected to the SF6 + Ar plasma nanotexturing presented the highest surface roughness. Investigation of the atomic structure indicated that the annealing process is responsible for a significant increase in sp2 hybridization of C. The contact angle measurement results have revealed the hydrophilic to hydrophobic transition owing to the annealing process. In contrast, super hydrophilic behavior was observed after the plasma nanotexturing processes. The increase in both the surface roughness and hydrophilicity of these nanotextured carbon thin films are highly desirable characteristics for their application as counter-electrodes in dye-sensitized solar cells and batteries.

© 2018 Author(s).The influence of the reactive magnetron sputtering deposition power on determining the stoichiometry and structure of cobalt oxide polycrystalline films is investigated using experimental and simulated data. Direct current discharges with powers in the 80 - 240 W range are tested using a metallic Co target and an Ar + O 2 plasma. X-ray diffraction results show that lower deposition powers favor the spinel C o 3 O 4 phase, while higher powers produce films presenting the rocksalt CoO phase. Computer simulations indicate that lower power processes occur in the poisoned target regime, while higher power depositions favor the metallic target regime. Consistent with the simulations, oxygen optical emissions (O I = 777.3 m) from the plasma show a significant decrease while the cobalt emissions (e.g., the C o I = 340.5 nm line) are significantly increased when the deposition power is increased. The results show that the film stoichiometry and structure are directly related to the deposition power, at constant O 2 flow.

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature.The authors regret an error in the Experimental section of the published article:

© 2017, Springer-Verlag GmbH Germany.Plasma-treated carbon thin films are investigated as counter electrodes for dye-sensitized solar cells. The films were grown onto fluorine-doped tin oxide (FTO) substrates by magnetron sputtering using pure graphite target and argon atmosphere and subsequently annealed at 600 °C for 30 min in vacuum. These films were then submitted to a plasma texturing process in a reactive ion etching reactor using three different gas combinations: sulfur hexafluoride/argon (SF6 + Ar), sulfur hexafluoride/hydrogen (SF6 + H2), and sulfur hexafluoride/oxygen (SF6 + O2). The morphology and structure of the obtained films were characterized by scanning electron microscopy and Raman spectroscopy. Cyclic voltammetry technique allowed accessing the improvements in their catalytic properties, while the photocurrent-voltage curves under simulated solar illumination AM 1.5G (100 mW/cm2) evaluated the performance of the respective assembled solar cells. The results show that photovoltaic performance is significantly affected by the different plasma texturing conditions used. The carbon counter electrode obtained after SF6 + O2 plasma texturing achieved the best power conversion efficiency of 2.23%, which is comparable to the 2.31% obtained using the commercial platinum counter electrode.

© 2018, Springer-Verlag London Ltd., part of Springer Nature.The determination of the thermal field in a turning process is fundamental to improve the process quality. Recently, the carbide tools have been coated with ceramic materials that present insulating characteristics. This work presents an analysis of the thermal effects of coating in a carbide tool during a turning process using the COMSOL® software and a nonlinear inverse problem. The thermal model consists of a coated carbide tool, a tool holder, and a shim represented by the transient three-dimensional heat diffusion equation with heat loss by convection and radiation. The heat flux, previously unknown, is obtained through the function specification method. In order to validate the methodology, the heat flux is compared with the author’s previous work. Titanium nitride (TiN) and aluminum oxide (Al2O3) are utilized as the coating materials. Both coatings present the expected behavior when less heat is dissipated to the cutting tool substrate. The coated carbide tools present higher temperatures than the uncoated carbide tool in the contact area. The study also found that the thicker the coating, the higher the temperature in the contact area. The results presented in this work may help the development of new long-lasting coated carbide tools.

© 2018 Elsevier Masson SASThis works proposes an Inverse methodology to estimate the thermal efficiency of a Gas Tungsten Arch welding (GTAW) process as a time-dependent function. The direct model consists in solving the non-linear three-dimensional heat diffusion equation through the Finite Difference Method in a C++ code. As the inverse methodology, the Golden Section optimization technique was used together with the Time Travelling Regularization to estimate the applied heat rate in the GTAW process. The Time Travelling Regularization was used to reduce the noise on the estimated heat input. Furthermore, a numerical Temperature moving sensor is proposed to determine the heat input as a time-dependent function. The methodology was applied in lab-controlled experiments based on a Robust Project matrix. The numerical analysis revealed that the thermal efficiency decreased as the arch torch moves. The proposed methodology also presented a higher sensitivity than the usual methods for the heat rate estimation and is a cheaper way to determine the melting efficiency in welding processes.

© 2018 Elsevier LtdThe heat flux inverse analysis is significantly affected by the heat flux distribution in laser welding simulation. This work proposed a different approach for the heat distribution which predicts the temperature and the weld bead in laser welding. The influence of the heat flux distribution in an inverse heat conduction problem applied on laser welding simulation is studied by comparing different heat distribution models. An inverse heat conduction algorithm based on the three-dimensional (3D) heat diffusion equation and the enthalpy function to model the phase change problem are used to estimate the heat flux under different heat distributions. The Time Traveling Regularization is applied with the Golden Section method to estimate the heat flux in the studied cases. The proposed cubic root and square root of the volumetric heat distribution presented a good agreement between the weld profile and the experimental temperatures. The heat rate estimation proves to be dependent on the heat distribution. The proposed methodology is an alternative to predict the weld bead profile and the thermal efficiency in low penetration laser welding.

© 2018 by the authors. Licensee MDPI, Basel, Switzerland.This work presents a technique called Time Traveling Regularization (TTR) applied to an optimization technique in order to solve ill-posed problems. This new methodology does not interfere in the minimization technique process. The Golden Section method together with TTR are applied only to the objective function which will be minimized. It consists of finding an ideal timeline that minimizes an objective function in a defined future time step. In order to apply the proposed methodology, inverse heat conduction problems were studied. Controlled experiments were performed on 5052 aluminum and AISI 304 stainless steel samples to validate the proposed technique. One-dimensional and three-dimensional heat input experiments were carried out for the 5052 aluminum and AISI 304 stainless steel samples, respectively. The Sequential Function Specification Method (SFSM) was also used to be compared with the results of heat flux obtained by TTR. The estimated heat flux presented a good agreement when compared with experimental values and those estimated by SFSM. Moreover, TTR presented lower residuals than the SFSM.

© 2018 Elsevier LtdDue to the current pace of technological growth, the management of system safety has evolved with complex causes of accidents that are often beyond the identification of traditional safety assessment techniques. Recently, the hazard analysis tool Systems Theory Process Analysis (STPA) has emerged as an approach to improve safety of modern complex systems in concert with other hazard analysis tools. However, the effectiveness of STPA is a debatable issue in the industry and efforts towards incorporating some level of formalization in STPA steps are welcome. In this direction, this work presents a method for combining STPA and model checking, in order to provide a formal and unambiguous representation of the system under analysis and the threats identified by STPA. A practical case study of a robotic flight simulator is presented as an example of the proposed method. The results achieved with the proposed approach indicates that the merging of the two techniques improves the knowledge about the system under design and the consistence of the design changes proposed to tackle the safety constraints identified in STPA.

© 2018, The Brazilian Society of Mechanical Sciences and Engineering.This work investigates the energy consumption of industrial robots in the context of automotive industry. The purpose is to identify the most influencing parameters and variables and to propose best practices with focus on energy efficiency. The analysis approach is composed of three experiments performed in a simulation environment that test different values of programming parameters and variables, such as joint speed, acceleration, robot payload. The first experiment focuses on energy consumption of robots at standstill. The second one considers the robot moving along different paths. Finally, the third one analyses how the joint friction is affected by load, speed and temperature and how it influences the energy consumption. Results show that at standstill, it is important to reduce dwell time, select an energy efficient position and reduce the programmed value of the timer responsible for turning off the servomotors. While moving, it is important to select maximum continuous termination for intermediate points and avoid low speeds. Regarding friction variation, results show that at high motor speed, low temperatures increase energy consumption. In order to evaluate the contribution of the best practices in a real environment, they are applied to a welding robotic cell of an automotive industry.

© 2018 IEEE.The use of commercial robots in aircraft industry faces many challenges. Among them, this work approaches the problem of maintaining the robotic end-effector perpendicular to the work surface. The perpendicularity error when performing operations such as drilling and riveting affects can affect the overall aircraft drag and cause fatigue cracks. In this work, we present, compare and analyse two different solutions for the correction of the perpendicularity error of a robot. Both solutions are different from existing ones described in the literature. The first solution uses only a point distance laser sensor fixed in robot end effector. The end effector moves in its X and Y axes sequentially to determine the correct robot angle B, C. It then correct distance Z to normalize the pose and adjust the position between the effector and target. Two different point distance lasers were tested. The second solution normalizes the robot pose through a linear scan sensor and a point sensor that allows us to quickly generate the correction angles and Z distance direct without robot movements. The paper verifies if the methods are able to comply with a perpendicularity requirement of 0.5° of maximum error between the manipulator and the normal of the tested table. The results showed that only the second solution is able to achieve the required perpendicularity.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.The aircraft design problem is an example of a highly integrated design, which calls for a multidisciplinary approach from the very beginning. With every generation of aircraft, it gets more difficult to make substantial improvements since so much have already been done to make aircraft as possible. Next generation civil aircraft needs to take every possibility to increase efficiency. One potential area of improvement is to reduce drag due to the requirement of positive stability. However, with the present state of the art it is difficult to get a system that can artificially stabilize an aircraft, certified. If this can be overcome, there are potential gains in drag, since all horizontal surfaces can be used for lift. Another advantage is that a wider range for center gravity can be allowed. In flight control the input signal to the aircraft are usually taken to be position of control surfaces. This is then translated to requirements on the actuation system, where the natural compliance of these systems is regarded, as something unwanted, when in fact it can also be used to tailor characteristics also at the aircraft level. This is relevant to both civil and military aircraft. The approach used here is to look at control surface actuators and different means to utilize also force control, possibly together with position control, and to introduce compliance in proper positions of the system. The pressure feedback is evaluated in a simulation environment using HOPSAN simulation package. Furthermore, an experiment is performed with the pilot in the loop to evaluate the different values of feedback gain. Statistical analysis of the results shows a significant influence of feedback level in the ability of the pilot to control the aircraft.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.This paper presents a data-driven failure identification of flight control surfaces using neural networks. Experiments were performed in a motion-based flight simulator (SIVOR) that has been developed at Aeronautics Institute of Technology (ITA). We use a two-layer feed-forward network and we analyze the influence of the input parameters and the number of neurons in the hidden layer on the performance of the failure identification task. The evaluation of the neural network's performance is based on overall accuracy, training time, number of iterations, precision and recall. Best results were found for networks with 100 neurons in the hidden layer, presenting 97.2% of overall accuracy.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.A great amount of aeronautical accidents and incidents in the last decades are associated with human causes, which can be related not only to the human itself, but with the human machine interface associated to a piloting task. This work presents a preliminary experiment that aims at analysing how a set of different tasks increases the workload of the pilot and how pilot's performance is affected by the increasing workload under different flight conditions (normal and abnormal). The experimental procedure considers 3 pilots executing a take-off and stabilization mission, where a group of tasks, based on the MATB-II approach, are systematically presented to the pilot. Variables such as altitude, heading, rate of climb and yaw rate, are measured. The results show that the variables measured near the pilot input command are more affected by the different levels of workload.

© 2018 Paulo Diego Barbosa da Silva et al.Operational simulators have a fundamental role in space programs. During a satellite operation, these simulators are essential for validating critical manoeuvres, testing new on-board software versions, and supporting the diagnosis of anomalies. With the purpose of reusing the operational simulators, the Brazilian National Institute for Space Research has proposed a new standard for the specification of the components that must be integrated in their in-house developed simulators. The new standard describes the behaviour of satellite subsystems using cause-effect tables that relate telecommands, electrical switches, equipment working states, energy consumption, telemetries, and operating modes of the subsystem. Using this new standard as input, this work proposes an approach that merges model-based testing and model checking to verify the correct implementation of new components in the satellite simulator. The verification approach consists of extracting state machines from the cause-effect tables and used it to automatically derive a test case suite. In order to validate the proposal, we applied it to three different satellite subsystems and assessed the results obtained from the test campaigns. In all the three cases, the proposed approach identified errors in the simulator components that were not initially detected by the traditional testing approach used at the Brazilian National Institute for Space Research.

© 2018 by University of Lavras, University of Campinas, National Institute of Space Research and Aeronautics Technological Institute. Published by the American Institute of Aeronautics and Astronautics, Inc.Problems in requirements documents are among the root cause of a number of accidents in space missions. A common approach toward the minimization of these problems is to transform the requirements into models that represent the system's behavior. However, this solution requires dealing with issues such as choosing the best modeling formalism, defining to what extent the transformation process should be automated, and assuring the quality of the requirements documents to be used as input. In space missions, requirements are frequently tailored from standard documents, such as the Packet Utilization Standard, which are composed of mandatory and optional requirements. This paper presents a semi-automatic method to transform standard requirements documents into extended finite state machines. Toevaluate it, we apply the methodtoa setofrequirements from the Packet Utilization Standard. We evaluate the method using some Packet Utilization Standard services. In light of the results, the paper discusses advantages and potential problems of each approach.

© 2018 European Control Association (EUCA).Quaternion algebra is frequently employed for spacecraft attitude description due to its convenient numerical properties when compared to minimal formulations. In parallel, Linear Quadratic Control (LQR)-based attitude controllers are often applied to underactuated vehicles due to its intuitive tuning process and satisfactory stability robustness properties. However, nonlinear quaternion differential equations of motion linearization yields non-stabilizable systems. Thus, LQR techniques cannot be directly employed since the associated algebraic Riccati equation is ill-posed. The commonplace solution resorts to a reduced quaternion model where only three out of four quaternion coordinates are exploited. The present work shows that such choice exhibits numerically unstable regions that impedes solving the LQR problem for all possible operating points. Additionally, we propose two methods to obtain wellposed LQR problems over all operating points. The first is based on the reduced quaternion model with an appropriate change of coordinates. The second is to append a virtual stabilizing input (VSI) to the nonlinear system to attain controllable linearized systems. The VSI direction should be appropriately chosen to not disturb the controllable modes of the system. Finally, we show that a class of constant angular velocity tracking problems is time-invariant under an appropriate change of variables such that time-invariant LQR techniques are applicable.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.The assumption of small deformations in the formulation of the flight dynamics of flexible aircraft can be very convenient as it allows the use of a reduced number of modes of vibration to represent the structural dynamics with little loss of accuracy. However, depending on the level of structural flexibility, deformations may become large enough to violate this simplifying assumption, making geometrically-nonlinear formulations necessary. Delimiting the range of validity of small deformations is then indispensable for the flight-mechanics engineer in state-of-the-art aircraft design. In this paper, small- and large-deformation formulations are compared in equilibrium conditions and in time-marching simulations for aircraft with different levels of structural flexibility. The importance of geometrical nonlinearities and the range of validity of small deformations are assessed.

© 2018In this paper, the mathematical model of a flexible spacecraft system composed of a hub and two symmetrical beams loaded with tip masses is reconsidered to design a control law for internal disturbance rejection. This model has a port-Hamiltonian structure and is passive. The disturbance rejection is performed by a feedback control law using the angular rates at the two tips of a beam. The closed-loop asymptotic stability of such a collocated / non-collocated control is analyzed through explicitly solving the Partial Differential Equations (PDE) of the system. Finally, the experimental results are carried out to assess the validity of the proposed control methodology.

© 2018Discretizing open systems of conservation laws while preserving the power-balance at the discrete level can be achieved using a new Partitioned Finite Element Method (PFEM), where an integration by parts is performed only on a subset of the variables in the weak formulation. Moreover, since boundary control and observation appear naturally in this formulation, the method is suitable both for simulation and control of infinite-dimensional port-Hamiltonian systems. The method can be applied using FEM software, and comes along with worked-out test cases on the 2D wave equation in different geometries and coordinate systems.

Copyright © 2017 John Wiley & Sons, Ltd.Three-dimensional hybrid-Trefftz stress finite elements for plates and shells are proposed. Two independent fields are approximated: stresses within the element and displacement on their boundary. The required stress field derived from the Papkovitch-Neuber solution of the Navier equation, which a priori satisfies the Trefftz constraint, is generated using homogeneous harmonic polynomials. Restriction on the polynomial degree in the coordinate measured along the thickness direction is imposed to reduce the number of independent terms. Explicit expressions of the corresponding independent polynomials are listed up to the fifth order. Illustrative applications to evaluate displacements and stresses are conducted by hexahedral hybrid-Trefftz stress element models. The hierarchical p- and h-refinement strategy are exploited in the numerical tests.

© 2017 Elsevier B.V.Hexahedral hybrid-mixed finite elements are proposed for free vibration analysis of three-dimensional solids. The element formulation relies on the simultaneous and independent approximations of stress and displacement in the element domain as well as the displacement on their boundary. Sets of complete and linearly independent non-nodal Legendre polynomials used for the field variables lead to symmetric, highly sparse and well conditioned solving systems. Numerical tests show that the elements yield accurate results, even in the presence of high stress gradients, and they seem to be free of shear and volumetric locking and have low sensitivity to mesh distortion. The hierarchical p-refinement strategy is exploited.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.This article presents a Fluid Structure Iteration method applied as a study case to a recent conventional transport aircraft with aspect ratio of 12. It evaluates the nonlinear structure effect on the static limit loads calculation. It uses the tool called E2-FSI, which stands for Nonlinear High-fidelity Static Fluid-structure Iteration, developed for high flexibility static aeroelastic evaluations. It uses Reynolds Average Navier Stokes Computational Fluid Dynamics combined with detailed Finite Elements Method in linear and nonlinear structural analyses. A discussion about the use and applicability of high fidelity static Fluid Structure Iteration for static loads calculation is presented as part of the conclusion, for both current and future conventional transport aircrafts.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.Conventional transport aircrafts are becoming more flexible in order to achieve lower fuel consumption. Most part of the additional flexibility comes from the increased wing aspect ratio. This line of studies is composed by sequential phases which come from Aerodynamics to Structures passing through Loads and Aeroelasticity technologies. This work proposes the integration of Aerodynamics and Structures through a multidisciplinary analysis, focusing on the high flexibility aspects of the wing in-flight shape for a recent, high aspect ratio aircraft. This work aims to understand the changes in the loads and structural sizing processes due to the increased flexibility of the wing. It uses a recent and high aspect ratio aircraft as a study case. Potential Computational Fluid Dynamics and nonlinear Finite Elements Method analyses are integrated employed in this study. Large displacements was included in the process, showing impacts for future development methodologies.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.This article presents the development of a real-time flight load measurement system convertible to real-time flight geometry measurement. It uses already known full bridge strains gages in a different manufacturing possibility: inside composite layers before resin cure. The manufacturing process is validated using a composite bar prototype. The prototype is submitted to a four points structural test in order to validate the measurements and influences of the manufacturing process. The whole process is applied to X-HALE aircraft disclosing a composite built-in measurement system for real-time flight load and flight geometry.

© 2018 IEEE.Titanium dioxide (TiO(2) thin films were deposited on conductive (titanium and fluorine tin oxide glass), insulant (mica, cover glass and thermal SiO(2 thin film on silicon) and semiconductive (silicon (100) and 4H-SiC) substrates by atomic layer deposition (ALD) technique. The metal and ligand precursors used were titanium tetrachloride and water, respectively. Grazing incidence X-ray diffraction (GIXRD) analysis was performed to investigate the dependence of crystalline phase of the as-deposited thin films on different substrates for process temperatures ranging from 150-450 °C. Results indicate that the ALD TiO(2 crystalline phase is dependent on the substrate nature which modifies the required temperature for phase change, i.e. from amorphous to anatase to rutile. For example, for conductive substrates the temperature for formation of rutile phase is around 350 °C while for semiconductor substrates it was observed only from 400 °C. By other hand, when the substrate has an amorphous structure there is not a common rule, i.e. for mica and thermal SiO(2 thin film on silicon only anatase phase was formed in all temperature range investigated while, for cover glass, it was possible to observe all stages of TiO(2 phase change, highlighting the formation of brookite phase for temperatures between 300 and 350 °C. Moreover, it is shown that rutile phase can be obtained, in pure phase, at temperatures higher than 400 °C, however only for glass and titanium substrates. These results allow us to infer that less expensive Ti thin film could act as a good seed layer for growth of good quality rutile TiO(2 phase, by using ALD process on Si substrate and using precursors such as TiCl4 and H2O.

© 2018 IOP Publishing Ltd.Materials used in space vehicles components are subjected to thermally aggressive environments when exposed to atmospheric reentry. In order to protect the payload and the vehicle itself, ablative composites are employed as TPS (Thermal Protection System). The development of TPS materials generally go through phases of obtaining, atmospheric reentry tests and comparison with a mathematical model. The state of the art presents some reentry tests in a subsonic or supersonic arc-jet facility, and a complex type of mathematical model, which normally requires large computational cost. This work presents a reliable method for estimate the performance of ablative composites, combining empirical and experimental data. Tests of composite materials used in thermal protection systems through exposure to a plasma jet are performed, where the heat fluxes emulate those present in atmospheric reentry of space vehicles components. The carbon/phenolic material samples have been performed in the hypersonic plasma tunnel of Plasma and Process Laboratory, available in Aeronautics Institute of Technology (ITA), by a plasma torch with a 50 kW DC power source. The plasma tunnel parameters were optimized to reproduce the conditions close to the critical re-entry point of the space vehicles payloads developed by the Aeronautics and Space Institute (IAE). The specimens in study were developed and manufactured in Brazil. Mass loss and specific mass loss rates of the samples and the back surface temperatures, as a function of the exposure time to the thermal flow, were determined. A computational simulation based in a two-front ablation model was performed, in order to compare the tests and the simulation results. The results allowed to estimate the ablative behavior of the tested material and to validate the theoretical model used in the computational simulation for its use in geometries close to the thermal protection systems used in the Brazilian space and suborbital vehicles.

© Sociedade Brasileira de Física 2018. Hollow cathode discharge (HCD) is widely used in material processing and plasma emission spectroscopy due to several advantages over other plasma sources. Basically, the HCD consists of a cathode with a hollow structure (cavity, hole, or parallel faces) and an anode of arbitrary shape. In this investigation, experimental studies on low-pressure plane-parallelHCD operated at different process conditions are reported. Herein, we investigate the dependence of the discharge current on the product of the gas pressure and intercathode distance (pD). In addition, the electron temperature and density were inferred from the current-voltage characteristics of a single cylindrical Langmuir probe positioned between the cathodes, on the discharge axis. The measurements were carried out at different gas pressures, magnetic field intensities, working gases, inter-cathode distances, cathode materials, and discharge voltages. The results showed that, at different gas pressures, the maximum discharge current (I d,max ) is not only a function of the product pD, but also of the pressure itself. Application of a uniform longitudinalmagnetic field improved plasma confinement between cathodes, leading to a substantial increase in I d,max in most of the situations considered in this study. However, for oxygen discharge, a strong discharge current reduction after the application of the magnetic field was observed. In relation to the Langmuir probe studies, it was observed that the uniform longitudinal magnetic field reduced the electron temperature, but this behavior depends strictly on pD. The typical values of electron density and electron temperature in the case of the nitrogen discharge were n e = 10 17 m −3 and T e = 2.5 eV, respectively. Finally, our experiments showed that the pD range for hollow cathode effects was between 0.2–5 Pa m.

© 2018 ASM International® All rights reserved.The plasma torch design affects the particle-plasma interaction, in-flight properties and the coating microstructure. When spraying metallic powders, the in-flight oxidation as well as the particle velocity and temperature determine the mechanical, corrosion and oxidation properties, which have a major impact on the in-service degradation of bond coats. This study aims to determine the microstructural and mechanical properties of as-sprayed CoNiCrAlY coatings deposited on the Inconel 718 alloy. Depositions were made using a High Velocity Plasma Spray Process (HVPS), which is based on a special plasma torch design. In-flight particle characteristics were determined to elucidate the kinetic and thermal regime of HVPS process.

© 2018, University of Tehran.Activated carbon (ACAcaí) was obtained from the activation of açaí seeds at 800 °C under CO2 flow. The surface groups of the material were determined by Boehm titration and information about surface charge was obtained using the methodology of the point of zero charge (PZC). Boehm titration and PZC tests showed that the ACAcaí sample has a basic character. The optimum pH range for the adsorption process is 3.5–8 and the optimum dosage is 0.1 g/50 mL of phenol solution. ACAcaí has a surface area of 496 m2 g−1 and pore volume of 0.217 cm3 g−1. The adsorption kinetics follows the pseudo-second-order model. The Langmuir isotherm model satisfactorily described the experimental data. The maximum adsorption capacity obtained was of 133 mg g−1 at 25 °C. Deionized water, NaOH solution (0.1 M), and ethanol were used as desorption agents, but none of them showed promising results for the regeneration of ACAcaí. The thermodynamic studies show that the adsorption process is exothermic, spontaneous, and favorable.

© 2018, Springer Science+Business Media, LLC, part of Springer Nature.Homogeneous dispersion of carbon nanotubes (CNTs) in polymers has significantly improved their processing and application as nanomaterials. Generally, CNTs tend to agglomerate due to their high aspect ratios and strong van der Waals interaction. Surface functionalization appears to be a solution to this problem. This study presents a controlled dispersion of carbon nanotubes in polyethylene through surface modification using a mixture of concentrated acid and octadecylamine (ODA). CNTs were characterized by Fourier transform infrared, Raman and X-ray photoelectron spectroscopy, and transmission electron microscopy. The results confirmed that carboxyl and alkane groups were successfully introduced on CNT surfaces. The acid- and amine-functionalized carbon nanotubes were dispersed in four solvents with different polarities (water, ethanol, acetone, and xylene) to correlate the degree of dispersion of CNT with their polarity. The results showed that CNT dispersion stability strongly depends on solvent and carbon nanotube polarities after the functionalization step. The nanohardness and tensile tests showed that the addition of CNTs, especially the functionalized with ODA, leaded the polymer harder, increasing its Young’s modulus and tensile strength. However, its toughness and deformation capacity were reduced. The potential applications of CNT-based polymer nanocomposites broaden considerably due to the surface engineering of carbon nanotubes.

© 2018 Elsevier B.V.Activated carbon from coconut shells is known as an excellent adsorbent to remove contaminants, it was successfully inserted into the TiO2 structure via sol-gel method, and the sonocatalysis of methylene blue was evaluated. TiO2 nanoparticles and coconut shell were used for synthesizing activated carbon composite (TiO2–COC) with carbon contents in the range of 0.5–10% by weight. These nanomaterials were characterized by X-ray powder diffraction (XRD), Raman spectroscopy, Emission gun scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), Brunauer-Emmett-Teller (BET) surface area, Fourier transform infrared spectroscopy (FT-IR), Field Emission Gun Scanning Electron Microscope (FEG–SEM) and Transmission electron microscopy (TEM). The physical-chemical properties of the catalysts were investigated in depth; in particular the kinetic studies conducted to determine the real degradation capacity of each material. The nanocomposites with carbon content of 0.5, 1.0, 2.0% in mass presented better catalytic activity when compared to a commercial one (Degussa-P25) and a lower dye adsorption was observed. The catalyst with 10% of carbon mass removed all methylene blue content through the adsorption process. Some catalysts reached high activity; the ultrasound effect was increased in 22% after only 2 h using low effective power output (40 W). The main reason for the increased catalytic was the perfect insertion of TiO2, which fill the coconut structure, sealing pores, reducing the carbon roughness and decreasing the TiO2 particle size. The electrical charge recombination on TiO2 surface enhances the sonocatalytic activity.

© 2018, Springer Science+Business Media, LLC, part of Springer Nature.The aim of this study was the development of low-cost tannin-formaldehyde xerogel/TiO2 (XTi-w) and carbon xerogel/TiO2 (XTiC-w) photocatalysts. The materials used as precursors were recycled titanium scraps and black wattle tannin extract, highlighting the low-cost approach employed in the synthesis. The materials were characterized by diffuse reflectance spectroscopy, scanning electron microscopy, dispersive energy spectrophotometry, X-ray diffractometry, infrared and Raman spectroscopy. X-ray diffractometry showed that the XTiC-w have tetragonal crystalline structure (anatase), whereas the XTi-w has an amorphous structure. The Raman and infrared analysis also showed the presence of titanium dioxide in the composition of both XTi-w and XTiC-w. XTi-w and XTiC-w showed photocatalytic activity at the visible wavelength. Titanium dioxide displayed no photocatalytic activity at the visible wavelength. The XTi-60 composite displayed the highest efficiency in the removal of the methylene blue from the system, as well as good reusability properties. The radicals with higher influence in the photocatalytic reaction mechanism are the photo generated electron and the singlet oxygen molecule. The effect of the heat treatment is negative on the photocatalytic properties of the hybrids produced, due to the removal of acid sites, adsorbed water and OH surface groups. [Figure not available: see fulltext.].

© 2018 Elsevier B.V.This paper evaluates the feasibility of using niobium-based catalysts for the photodegradation of organic dyes. The metal oxides were prepared using niobium scraps and chips as precursors. The semiconductors were characterized by diffuse reflectance spectroscopy, scanning electron microscopy (SEM), X-ray diffraction, infrared and Raman spectroscopy. The as-prepared anhydrous niobium oxide has a pseudohexagonal structure, whereas the hydrated niobium oxide is an amorphous material. The specific surface area of the hydrated niobium oxide is found to be double the area of its calcined counterpart. The photocatalytic efficiency of the materials was evaluated by methylene blue (MB) decomposition, measured by UV-visible spectroscopy. The effects of catalyst dosage and initial dye concentration were investigated in both the adsorption and photocatalysis processes. Increasing the initial MB concentration leads to increase the amount of adsorbed MB but to decrease the photocatalytic efficiency for all materials. In contrast, both the amount of adsorbed dye and the photocatalytic efficiency increase with increasing the catalyst dosage (0.5–2 g L−1). The highest photodegradation efficiency is achieved using UVC radiation. The specific surface area as well as the amount of acid sites, adsorbed water, and OH− surface groups on the catalyst surface demonstrates to be fundamental to the photocatalytic properties of the materials. Furthermore, the photocatalytic mechanism is controlled by superoxide and singlet oxygen species for the hydrated material, whereas the hydroxyl radical is the main active species in the photodegradation employing the anhydrous oxide. The hydrated material achieved a complete degradation of the methylene blue.

© 2018 Elsevier Ltd and Techna Group S.r.l.This work explores the development of hybrid Nb2O5/carbon xerogel photocatalysts. The precursor materials used, such as tannin and recycled niobium scraps, enhance the economic and environmental aspects of the synthesis. The materials were characterized by diffuse reflectance spectroscopy, scanning electron microscopy, dispersive energy spectroscopy, infrared spectroscopy, Raman spectroscopy and X-ray diffraction. The photocatalytic action of the material was evaluated by methylene blue decomposition as determined by UV–visible spectroscopy. Anhydrous niobium oxide has a hexagonal structure. The X-ray profiles of the materials developed (XC-wNb) are similar to Nb2O5, confirming the presence of inorganic oxide in the matrix of these composites. The chemical elements that compose the samples are homogeneously distributed on the surface of the samples, confirming the dispersion of the oxide in the carbonaceous matrix. The XC-wNb absorbs radiation in a considerably wider range than inorganic oxides, in this case, for the entire wavelength range used in the experiments, thereby suggesting the synergistic effect of xerogel and niobium oxide on the optical properties of the XC-wNb samples. All XC-wNb presented photocatalytic activity under visible radiation, evidencing the beneficial coupling effect on the photocatalytic properties of the material. The XC-24Nb was the most effective photocatalyst at the wavelength used due its composition, morphological and photochemical properties. The methylene blue photodegradation is controlled to a greater extent by reaction with the OH• radical. The XC-24Nb also presents high stability and reusability, which are optimal properties for industrial application.

© 2017 Society of Plastics EngineersThis review describes the use of cellulose nanocrystals (CNC) as fillers in biodegradable polymer matrices over the past few years. The preparation and characterization of CNC-based nanocomposites are highlighted here with a focus on thermophysical and mechanical properties. The characterization and isolation of nanocellulose from different raw material sources are discussed in detail, as well as different surface modifications. The addition of CNC in biodegradable polymer, combined with nanocellulose surface engineering and driven by sustainability trends, has the potential to impact various industrial sectors. POLYM. COMPOS., 39:E9–E29, 2018. © 2017 Society of Plastics Engineers.

© 2018, Journal of Aerospace Technology and Management. All rights reserved.Lately, nanomaterials have been largely studied as reinforcements for epoxy resin. Although their usage is highly promising, the literature has reported some drawbacks regarding the improvement of mechanical properties in nanocomposites. These difficulties are usually due to dispersion of nanomaterials and its adhesion to the polymeric matrix. One approach to this problem is the functionalization of nanomaterials such as carbon nanotubes (CNTs) and graphene. In this work, we have studied the synthesis and functionalization process of CNTs and graphene oxide (GO) to be used as reinforcements for epoxy resin nanocomposites. CNTs were synthesized at 850 °C in a quartz furnace, from hexane and ferrocene vapor, and functionalized by acids and ethylenediamine treatments. GO was obtained by graphite exfoliation through a modified Hummer’s method. The nanomaterials were characterized by Raman spectrum, FT-IR, XRD, and SEM images. Nanocomposites were prepared using these nanomaterials and evaluated by DMA. While both nanomaterials showed an improvement in mechanical properties, suggesting a chemical bond between nanomaterial and the epoxy matrix, it was clear that GO reinforced samples presented a higher storage modulus.

© 2018 Elsevier Ltd and IIRThe number of air-conditioning (AC) applications where natural refrigerants are used has grown in the past few years, mainly due to their favorable thermodynamic characteristics. Hence, a numerical investigation based on the second law of thermodynamics and Seasonal Energy Efficiency Ratio (SEER) for R-290/POE ISO 22 condensers is performed, where the impact of the transversal number of tubes, fin density and length of the finned tube is evaluated for three types of fins (plain, wavy and louver). Thermodynamic properties were generated via the departure function approach using the Peng–Robinson equation of state. The influence of the POE ISO 22 concentration is also accounted for in the heat transfer and pressure drop calculations. Depending on the available heat transfer area, plain or louver fins are more indicated to enhance the AC performance enhancement. For a fixed cooling capacity, points of maximum second law efficiency are achieved when the transversal number of tubes and tube length are varied.

© 2017 Elsevier LtdThe use of natural convection as a passive heat removal mechanism has been widely explored as a safety system of nuclear power plants. Characteristics like low complexity and economy makes Natural Circulation Loop (NCL) an encouraging technology which is being investigated for the Generation IV nuclear energy systems. As a manner to enhance the performance prediction of NCL, this study provides an evaluation of the adaptive time-stepping scheme that the RELAP5/3D code uses to calculate the time-step size applied during a transient simulation. Additionally, the Fast Fourier Transform (FFT) and the Root-Mean-Square Deviation (RMSD) procedures were conducted in order to investigate the agreement between the numerical and experimental data during the time frame when two-phase flow instabilities appear. Temperature measurements extracted from an experimental facility were used as the baseline data. For this evaluation, four different maximum time-step sizes were considered and their effect on the prediction of NCL temperatures was analyzed.

© 2018 Elsevier LtdThis paper describes how the scientific contributions of Prof. Szargut and his co-workers have inspired the academic activities of the Exergy Team of the Laboratory of Environmental and Thermal Engineering (LETE) of the Polytechnic School of the University of Sao Paulo. The work of Prof. Szargut was at first used for preparing a course on Exergy Analysis, which has been taught since 1992 to MSc and Ph.D. students of the graduate program in Mechanical Engineering of the Polytechnic School of the University of Sao Paulo. Since then, the methods and concepts established by Prof. Szargut have played an important role in the development of the various research lines at LETE for the past fifteen years. Complex thermodynamic systems, such as petroleum production and refining plants, biofuel production routes, combined production of ethanol and electricity technologies, aircraft systems, environmental impact mitigation processes, CO2 capture units, ammonia production facilities, and the human body and its systems were analyzed using the concepts and tools suggested by Prof Szargut. The present article illustrates how the application of exergy analysis, thermoeconomic and environmental performance indicators, cumulative exergy consumption, definition of reference environment and chemical exergy can serve different purposes when evaluating thermodynamic systems.

Copyright © 2018 by ASME.This work describes a methodology used for counter-rotating (CR) propellers performance estimation. The method is implemented in an in-house program for gas turbine performance prediction, making possible the simulation of the counter-rotating open rotor (CROR) architecture. The methodology is used together with a variable geometry compressor control strategy to avoid surge conditions. Two cases are simulated under transient operation for both fixed and variable geometry compressor. The influence of the variable geometry control on the transient performance of CROR engines is evaluated and a comprehensive understanding on the transient behavior of this type of engine could be obtained. It is shown that the use of the variable geometry compressor control does not significantly affect the overall engine performance, while avoiding the surge conditions, thus ensuring the engine operation safety.

© 2018, Emerald Publishing Limited.Purpose: The present work aims to analyze the feasibility of wingtip device incorporation into transport airplane configurations considering many aspects such as performance, cost and environmental impact. A design framework encompassing optimization for wing-body configurations with and without winglets is described and application examples are presented and discussed. Design/methodology/approach: modeFrontier, an object-oriented optimization design framework, was used to perform optimization tasks of configurations with wingtip devices. A full potential code with viscous effects correction was used to calculate the aerodynamic characteristics of the fuselage–wing–winglet configuration. MATLAB® was also used to perform some computations and was easily integrated into the modeFrontier frameworks. CFD analyses of transport airplanes configurations were also performed with Fluent and CFD++ codes. Findings: Winglet provides considerable aerodynamic benefits regarding similar wings without winglets. Drag coefficient reduction in the order of 15 drag counts was achieved in the cruise condition. Winglet also provides a small boost in the clean-wing maximum lift coefficient. In addition, less fuel burn means fewer emissions and contributes toward preserving the environment. Practical implications: More efficient transport airplanes, presenting considerable lower fuel burn. Social implications: Among other contributions, wingtip devices reduce fuel burn, engine emissions and contribute to a longer engine lifespan, reducing direct operating costs. This way, they are in tune with a greener world. Originality/value: The paper provides valuable wind-tunnel data of several winglet configurations, an impact of the incorporation of winglets on airplane design diagram and a direct comparison of two optimizations, one performed with winglets in the configuration and the other without winglets. These simulations showed that their Pareto fronts are clearly apart from each other, with the one from the configuration with winglets placed well above the other without winglets. The present simulations indicate that there are always aerodynamic benefits present regardless the skeptical statements of some engineers. that a well-designed wing does not need any winglet.

© 2018 Elsevier Inc.This paper reports the development and convergence analysis in steady-state of an effective and robust implicit finite-volume solver for compressible Euler equations on three-dimensional unstructured grids. A second-order upwind scheme (MUSCL) was employed based on Roe's approximate Flux-Difference Scheme (FDS) by using Venkatrakishnan flux limiters. The construction of the linear system for the implicit scheme was performed by applying the backward Euler on the left-hand side of the conservation equation and Newton-type linearization on the right-hand side. The Jacobian matrix that resulted from the linearization process was computed analytically using Roe flux terms. In this phase, the defect-correction technique was employed allowing effective time-dependent computations by an implicit time-integration scheme. In this approach, the flux integral on the right-hand side is computed based on a high-order of accuracy whilst the left-hand side the Jacobian is performed based on the low-order. The resulting sparse and large system of linear equations is solved by a sequential Gauss–Seidel iterative method. Simulations were performed and the developed implicit defect-correction solver was validated and verified. In addition, convergence analysis comparing the implicit solver and the explicit Runge–Kutta of 5-steps using Implicit Residual Smoothing (IRS) were performed showing the significant speed-up of the implicit solver over the explicit one. Simulations were performed for case studies to demonstrate the robustness of the developed implicit defect-correction solver in solving typical problems of aerodynamic involving transonic condition and shock wave captures for internal and external flows. Finally, the main particularities of the implicit scheme were investigated and discussed considering the simulation results, showing also its capacity to serve as an effective preconditioner (start-up method) to other implicit techniques.

© 2018 by ASME.This paper describes a methodology used for propeller performance estimation, which was implemented in an in-house modular program for gas turbine performance prediction. A model based on subsonic generic propeller maps and corrected for compressibility effects, under high subsonic speeds, was proposed and implemented. Considering this methodology, it is possible to simulate conventional turboprop architectures and counter-rotating open rotor (CROR) engines in both steady-state and transient operating conditions. Two simulation scenarios are available: variable pitch angle propeller with constant speed; or variable speed propeller with constant pitch angle. The simulations results were compared with test bench data and two gas turbine performance commercial software packages were used to fulfill the model validation for conventional turboprop configurations. Furthermore, a direct drive CROR engine was simulated using a variable inlet guide vanes (VIGV) control strategy during transient operation. The model has shown to be able to provide several information about propeller-based engine performance using few input data, and a comprehensive understanding on steady-state and transient performance behavior was achieved in the obtained results.

© 2018, The Brazilian Society of Mechanical Sciences and Engineering.The association of turbochargers with piston engines is widespread since both the efficiency and the power output of an engine could be improved. However, a piston engine operational range is wide and highly variable. This characteristic imposes challenges for the project and application of a turbocharger that should perform properly within the operational range. An important tool used to evaluate the performance of both turbine and compressor, which compose a turbocharger, is the characteristic map. The map condenses the main performance parameters into a single graphic that allow the evaluation of the machine characteristics, such as the operational width. A typical characteristic map relates the pressure ratio, mass flow rate, rotation and efficiency for each operational condition. The present work provides a technique to obtain the characteristic map of a turbocharger centrifugal compressor with reduced time consumption through steady state simulation using a fully unstructured mesh. Evaluation of the results indicated good accuracy for the predicted mass flow rate and pressure ratio. However, the resulting efficiency presented considerable discrepancy, which was aggravated when simulating extreme operational conditions or when the mass flow was used as a boundary condition. At last, the porter shroud and volute were evaluated within the entire range to provide an insight into the compressor operation.

© 2018, The Brazilian Society of Mechanical Sciences and Engineering.Advances in turbofan engine technology have led to engines with growing bypass ratios and lower fan pressure ratios, increasing the complexity of the in-flight thrust determination. Thrust values cannot be directly measured in flight; therefore, ground-level test are carried out, and the results calculated from thermodynamic properties of the gas are compared to the force exerted by the engine on the test bench. The result of this comparison is a scalar that is applied to the fan pressure ratio, fan pressure correlation, which attempts to minimize the error between the measured and calculated values. After the thermodynamic properties of the gas are measured during in-flight tests and together with the fan pressure correlation are used to calculate the in-flight thrust. The calculation procedure is implemented through VISUAL BASIC scripts, in the MICROSOFT EXCEL® environment. These scripts are used to calculate the generated thrust and the mass flow that go through the engine from the thermodynamic properties of the gas obtained from a high-fidelity numerical simulation of this engine. These results are then validated against the thrust and mass flow values calculated by this model. An analysis of the free-stream suppression effects on thrust is carried making use of these scripts.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.The pursuit of lower fuel consumption for aircraft is promoting a departure from contemporary arrangements. One example is the development of more synergetic airframe and propulsion system designs, which are expected to increase significantly aircraft efficiency mainly by means of boundary layer ingestion. By integrating propulsion and airframe, both systems will significantly impact each other. This mutual interference requires the development of novel performance evaluation methods that consider such effects. This manuscript introduces a propulsive efficiency equation for boundary layer ingestion propellers based on the power balance method. Two formulations are presented for numerical and analytical evaluations. The equation is bounded between 0 and 1 and allows a meaningful evaluation of shaft to propulsive powers conversion, which results in an accurate determination of thrust and drag. This manuscript is the first advance of a project that will develop an optimizing tool for boundary layer ingestion propellers based on computational fluid dynamic simulations. The results will be presented in subsequent manuscripts.

© Copyright 2018 ASME.Boosters are commonly used in liquid propellant rocket engines (LPRE) to allow lower propellant pressures in their storage tanks and, thus, smaller structural masses, contributing to cavitation free operation in the subsequent main turbopumps (TP). Boosters can be identified as key components for the overall performance of large engines, and if their operating requirements are stringent, they can operate under cavitation. Thus, effective design and performance tools are fundamental to design the components of these boosters considering this phenomenon. The simulation techniques based on turbulent and multiphase 3-D Computational Fluid Dynamics (CFD) were used in this work at steady state regime. The simulations were done using the commercial software CFX from ANSYS® Workbench. The study was conducted analyzing the performance of the first stage of the hydraulic axial turbine of the liquid oxygen (LOX) booster of the Space Shuttle Main Engine (SSME), at various operation points under cavitation, considering 3.0% tip clearance relative to blade height. The results obtained for, the performance parameters of this stage were compared with those obtained through monophase simulation, and the multiphase technique showed results closer to the experimental ones around the design point (DP), with increased simulation times acceptable for the computational resources currently available. Moreover, the results from the current work show the importance of considering the effects of cavitation through multiphase flow in hydraulic turbines.

Copyright © 2018 ASME.In modern gas turbine engines, many sophisticated cooling schemes are used to maintain the turbine blade temperature in acceptable levels. These schemes, such as convective cooling, film cooling, impingement cooling and the use of pin fins, can be combined to increase the cooling effectiveness. Jet impingement cooling, pin fins and convective cooling are internal cooling techniques, in which the cooling is achieved based on coolant flow through internal blade channels decreasing the blade metal temperature. Film cooling is an external cooling technique, in which the cold fluid (air) is injected into the hot gas flow through discrete holes providing a coolant film at blade surface, protecting the blade metal. In this way, the present work refers to the numerical investigation of internal and external cooling strategies applied in gas turbines. The methodology developed to analyze such strategies is based on the flat-plate approach with laboratory length scales and Computational Fluid Dynamics (CFD) techniques, being the flow, in the study domain, considered viscous, turbulent and compressible. A commercial CFD program is used to solve the general equations of fluid mechanics with Reynolds Average Navier-Stokes (RANS) technique for steady state regime and Shear Stress Transport (SST) turbulence model to determine the flow eddy viscosity. The combined effects of internal and external cooling is studied through a highly sophisticated scheme, called louver, which combines the effects of impingement and film cooling. Pin fins and ribs turbulator geometries applied in the channel between the impingement and the film cooling have the purpose of evaluating the impact of these geometries on the film cooling effectiveness over the flat surface in comparison to the louver scheme without turbulator. This study concluded that, pin fins proved to be the most promise solution because they increased in 7% the film cooling effectiveness. Ribs also have a good potential to increase the effectiveness, because an increase of 4% in film cooling effectiveness was observed. In addition, the effects of the turbulator are dependent on their location, since the turbulator positioned near the film cooling hole exit showed improvements in the film cooling effectiveness in relation to the turbulator near of the impingement cooling jet.

© 2018, Journal of Aerospace Technology and Management. All rights reserved.This article describes the run time characteristics of a gas turbine performance simulation using different solvers and components off-design performance database formats. Two different nonlinear systems of equation solvers, Newton-Raphson’s and Broyden’s, and two different formats of compressor and turbine off-design performance database (maps), tabulated values and fitted surface equations, were compared. Based on the results it is then possible to trade off and select the most appropriate combination of solver and component map type for the gas turbine performance simulation for real-time application.

© 2018, The Author(s).The present work presents and discusses the results of a comprehensive study on the bioactive properties of Nb-substituted silicate glass derived from 45S5 bioglass. In vitro and in vivo experiments were performed. We undertook three different types of in vitro analyses: (i) investigation of the kinetics of chemical reactivity and the bioactivity of Nb-substituted glass in simulated body fluid (SBF) by 31P MASNMR spectroscopy, (ii) determination of ionic leaching profiles in buffered solution by inductively coupled plasma optical emission spectrometry (ICP-OES), and (iii) assessment of the compatibility and osteogenic differentiation of human embryonic stem cells (hESCs) treated with dissolution products of different compositions of Nb-substituted glass. The results revealed that Nb-substituted glass is not toxic to hESCs. Moreover, adding up to 1.3 mol% of Nb2O5 to 45S5 bioglass significantly enhanced its osteogenic capacity. For the in vivo experiments, trial glass rods were implanted into circular defects in rat tibia in order to evaluate their biocompatibility and bioactivity. Results showed all Nb-containing glass was biocompatible and that the addition of 1.3 mol% of Nb2O5, replacing phosphorous, increases the osteostimulation of bioglass. Therefore, these results support the assertion that Nb-substituted glass is suitable for biomedical applications.

© 2018 Elsevier B.V.In this work we synthesized an activated carbon/magnetite composite by a simple co-precipitation method. The activated carbon (AC) was synthesized from the solid waste obtained in the extraction process of the peroxidase enzyme and the magnetic composite was used as support for the immobilization of soybean peroxidase (SP). After the determination of the optimal immobilization parameters, a 100% yield was achieved under the following conditions: support:enzyme proportion of 1.0:0.05 g, equilibration time of 7 h, pH 3.0 (citrate buffer phosphate 0.1 mol L−1) and temperature of 50 °C. The determination of pH to the point of zero charge was also done to assist in the understanding of the immobilization process at different pH values. Several characterization techniques were used, such as thermogravimetric analysis, elemental analysis composition, X-ray powder diffraction, Fourier transform infrared spectroscopy and Scanning electron microscopy. The biocatalyst presented excellent operational stability and was reused for 11 consecutive cycles. The magnetic properties inserted in the AC contributed to the removal of the biocatalyst from the reaction medium without interfering in the adsorptive characteristics of the AC. Thus, the activated carbon/magnetite composite can be applied to different research fields with high performance.

© 2017, Springer Science+Business Media B.V.The heterogeneous catalytic route to produce biodiesel can reduce the amount of effluents generated in the steps of esters purification and allows the reuse of catalysts. Specially, when the catalytic supports are synthesized from biomass wastes the process become even more environmentally friendly. In this work, we have synthesized activate carbons (ACs) from agroindustry waste generated after the extraction of essential oil of Candeia wood residue. These ACs were used to support H3PMo12O40. The performances of all the supported catalysts were evaluated on the lauric acid esterification reactions with methanol. The catalysts were produced through impregnation method, varying the H3PMo12O40 load and the support nature (i.e. commercial AC or produced from agroindustry residue). All materials were characterized by thermal analysis, FT-IR spectroscopy, SEM, EDS, BET surface area and powder X-ray diffraction. The catalysts showed good thermal stability. Data of the X-ray diffraction indicated that regardless support origin, a high dispersion of H3PMo12O40 was achieved. High turnover numbers were achieved by the H3PMo12O40/AC catalysts; 7205 for 10 wt% H3PMo12O40/commercial AC and 3571 for 10 wt% H3PMo12O40/agroindustry waste AC. Tests of reuse and leaching of the catalysts were also carried out. A strong deactivation of the catalyst was observed when it was reused directly, without previous treatment.

© 2018, ASM International.NiTi-based shape memory alloys are successful owing to its capacity to cover specific applications unreachable by binary NiTi. The additions of ternary, and even quaternary, elements are intended to change specific properties. Known for its antibacterial activity, Ag became an alloying element in a search for a functional biomaterial; however, the melting appears to hampering the system exploration. A special melting procedure by vacuum arc remelting was developed based on chemical and thermal analysis, via EDS, XRF, and DSC, assessing the element loss and ingot homogeneity, respectively. By alloy design, different Ag content NiTiAg SMA were produced and analyzed on as-cast condition. The melting procedure developed involves specific feedstock cares and preparation, melting, and some remelting steps. The measured chemical composition slightly differs from the nominal due to alloying element loss and the melting reaction thermodynamics. Being the lower the possible, the remelting steps were optimized to maintain the compromise between chemical composition and compositional homogeneity through the ingot, since the Ag content stabilizes along them, also indicating a limited content possible to be alloyed. Ag-yields are content-dependent, while the Ni:Ti relation is stable, being therefore the melting of NiTiAg SMA better performed by VAR than other melting routes under high vacuum conditions.

© 2018, Universidade Federal de Uberlandia. All rights reserved.This study discusses the microstructure, quasi-static mechanical strength and failure modes of TWIP steel weld spots. Weld spots were produced by varying the main resistance spot welding parameters: welding current, welding time and electrode compression force. All the samples showed a remarkable material hardness mismatch between the fusion zone, the heat affected zone and the base material, as evidenced by microindentation maps. Hardness at the fusion zone is lower than that of heat-affected zone and base metal, which facilitates interfacial failure mode during tensile-shear tests. However, high heat inputs promoted the failure mode changes to partial interfacial mode and then to pullout mode during tensile-shear tests as confirmed by Scanning Electron Micrographs. These changes in failure mode were accompanied by a notable increase in tensile-shear strength and energy absorption capability.

© 2018 Universidade Federal de Sao Carlos. All rights reserved.In the current work, XRD, SEM, EBSD and TEM techniques were used to evaluate the microstructure of stainless Fe-Mn-Si-Cr-Ni-Co shape memory steel processed by ECAE and annealed for one hour at temperatures ranging from 650ºC to 950ºC. The results were then correlated with the mechanical and shape-memory properties of the steel. It was observed that the samples containing large grains and a microstructure free of defects or precipitates presented a high volume fraction of multi-variant thermal martensite and stress-induced martensite, resulting in good shape recovery, owing to the memory effect. The grain refinement and precipitation of second-phase particles decreased the volume fraction and number of martensite variants and considerably increased the mechanical resistance, enhancing the elastic shape recovery. It was shown that shape memory properties were essentially related to the mechanical resistance of the matrix, which in turn was related to the microstructure.

© 2018 Universidade Federal de Sao Carlos. All rights reserved.The present work studied the influence of annealing on a Ni-Ti alloy submitted to uniaxial compression. The stress-strain curve under compression showed the absence of the Stress-Induced-Martensite (SIM) plateau and 42% of remaining austenitic phase (B2). identified by the Electron Backscattered Diffraction (EBSD) technique on a Scanning Electronic Microscope (SEM). Annealing at 150 ºC increased the volume fraction of austenite to 70%. Annealing at 200 ºC reduced the volume fraction of austenite to 33% and increased the classical Vickers hardness and the dynamic elastoplastic hardness. This increase suggests the presence of a phase with higher indentation resistance, which can be the R phase reported in the literature. Annealing at 250 ºC decreased the classical Vickers hardness and the dynamic elastoplastic hardness, probably due to recovery. Annealing at 300 ºC advanced the recovery process and promoted some recrystallization, as suggested by the large standard deviation observed in the hardness results.

© 2018 Universidade Federal de Sao Carlos. All rights reserved.The wire drawing mechanic of Ti-49.82Ni (at. %) Shape Memory Alloy (SMA) was investigated through the true stress-strain curves and drawing stresses. The tensile tested solution treated wire presented a four steps elongation at temperatures below the austenite finish temperature (AF), and a conventional one-step behavior above the martensite deformation temperature (MD). The tensile yield stress for the formation of detwinned martensite (DTM) or stress-induced martensite (SIM) increased as the testing temperature increased; however, for larger deformation, the behavior reversed. The efficiency of drawing work, which is the ratio of uniform work to total work, increased from 10% for 0.07 mm2.mm-2 area reduction at 25 °C to 50% for 0.21 mm2.mm-2 at 110 °C. Therefore, wire drawing temperature and area reduction should be combined to increase the efficiency, taking into account the desired properties with reasonable workability. Furthermore, transformation work should be considered on wire drawing shape memory alloys as phase transformation occurs in temperatures below MD.

© 2018, Revista Ingenieria e Investigacion - Editorial Board. All rights reserved.This paper presents the results from blast tests conducted on four 50 MPa concrete slabs with reinforcement ratios of 0,175% and 0,37%. Two of the slabs were retrofitted with 50 mm thick foam in order to investigate the potential of using the foam as a strengthening option. The slabs were simply supported on two sides. Non-confined PBX (Plastic bonded explosive) was molded with the form of a cylinder measuring 20 cm in height and 10,5 cm in diameter. The explosive was detonated at 2 m stand-off distance. The equivalent TNT mass of the explosive ranges from 2,58 to 2,72 kg for the four tests. Accelerometers, displacement and pressure gages were used to measure blast wave parameters and global response of the slabs. A high-speed digital camera in conjunction with a rugged notebook recorded images. Qualitative and quantitative results are included. Slabs retrofitted with foam showed a different pressure pattern as recorded by the sensors and resulted in higher displacement, acceleration and linear momentum.

© 2018 Sociedade Brasileira de Quimica. All rights reserved.The combustion process of triethylaluminum is investigated by means of reactive molecular dynamics simulations using the ReaxFF force field. The behavior of the system in five different temperatures ranging from 2000-4000 K was evaluated. As a pyrophoric material, TEA reacts also with water, generating gaseous hydrogen, whose content increases with the system temperature. Rapid water formation and O2 depletion were observed and, using Arrhenius equation, the preexponential factor and activation energy were found to be 9.67E+09 s-1 and 1.242 kJ mol-1, respectively. The results obtained are in accordance to the expected for pyrophoric materials and the simulation in question can help elucidating and analyzing the complex reaction mechanism of TEA combustion.

© 2018 Sociedade Brasileira de Quimica. All rights reserved.Prediction of chemical explosions parameters is an important step for blast tests for civil and military applications. Applying computational chemistry and experimental results, this paper presents the decay rate of pressure in air from the epicenter of 2.70 kg of PBX-Plastic bonded explosive detonation to the distance of 2.0 meters. Pressure in the epicenter was calculated using reactive molecular dynamics simulations and the incident pressure at 1.3; 1.6 and 2.0 meters were measured with piezoelectric pressure sensors. The explosive for the full-scale test were non-confined in a cylindrical shape. Results of simulation and recorded values were consolidated and the rate of pressure decay was verified by statistic regression. Good agreement was verified between computational and experimental pressures data. This research can help designers to prepare protection devices in test areas, storages of explosives or important buildings for military proposes.

© 2018, DESIDOC.Explosions emanating from terrorist attacks or military weapons cause damage to civilian and military facilities. Understanding the mechanical behaviour of reinforced concrete structures subjected to blast is of paramount importance for minimizing the possible blast damage. A full-scale experimental program consisting of six reinforced concrete slabs with compressive strengths of 60 MPa, 50 MPa and 40 MPa, measuring 1.0 m × 1.0 m × 0.08 m, and subjected to 2.7 kg of non-confined plastic bonded explosive, was conducted in blast test area of Science and Technology Aerospace Department (Brazilian Air Force). This paper compares experimentally measured peak displacement values with theoretical values. Theoretical analysis was carried out using single degree of freedom (SDOF) models. The comparison showed that SDOF analysis worked very well in predicting the reinforced concrete slab peak displacement against blast effects. Qualitative analysis after the experiments showed that the blast wave shape generated by the cylindrical explosive was not uniformly distributed on the slabs for the standoff distance of 0.927 m/kg13.

© 2018, Journal of Aerospace Technology and Management. All rights reserved.The present study assesses the influence of non-metallic constituents and manufacturing parameters, such as compaction pressure and sintering temperature, to produce a metal matrix composite (MMC) of copper/iron, based on the brake disc of aircraft AT-29 SuperTucano. The samples were produced with six different compositions, by varying the amount of abrasive particles (quartz and zirconia silicate) and the solid lubricant (graphite), with one of the compositions manufactured without the addition of graphite. The compaction pressures were 210 and 420 MPa, with sintering temperatures of 950 °C and 1050 °C in a furnace with controlled atmosphere of argon + 10% H2. After sintering, the effectiveness of the sintering process was evaluated through the apparent density (Archimedes’s method), Brinell and Vickers hardness, and the microstructure by Scanning Electron Microscopy (SEM). The sintering process was severely affected by the solid lubricant (graphite): its reduction resulted in a density increase near 18%, and the hardness of the compound up to 62%. The hardness values demonstrated significant variation with compaction pressure, with a pronounced effect on compounds with less non-metallic elements. SEM analysis demonstrated that not only graphite, but also the ceramic particles affected the sintering process through the agglomeration of inclusions into the metal-metal interface. The samples without graphite exhibited almost the same value of pores after sintering, regardless of the compaction pressure, indicating that the graphite content affects directly the sintering process, regardless of the compaction pressure.

© 2017 Acta Materialia Inc.We characterized the morphology, substructure and crystallography of lenticular martensite in a Fe-Ni-C alloy by means of electron backscatter diffraction and scanning electron microscopy. Electron backscatter diffraction maps were used to determine the orientation relationship between austenite and martensite across large regions of the microstructure. We employed orientation distribution functions as a statistical representation method for the observed orientation relationships. High-resolution point-to-point scans were used to normalize the effects of the orientation changes in the austenite caused by the plastic deformation during the formation of lenticular martensite. The analysis revealed that most of the transformation in this material follows an orientation relationship close to the one proposed by Greninger and Troiano.

© 2018, The Brazilian Society of Mechanical Sciences and Engineering.This paper describes an application of the virtual commissioning technology applied to the design of a robotized manufacturing cell. Virtual commissioning requires the integration of different technologies, such as PLC (programmable logic controller) programming, device communication with OPC (OLE for process control), off-line robot programming, HIL (hardware-in-the-loop), as well as the design of devices and tools using computer-aided design (CAD) applications. Within this application, the virtual commissioning resource evaluates the operation of an assembly line, simulates several processes in a digital environment, tests real equipment and tools and integrates a system that shares the signals of the sensors and actuators with the simulation environment in the computer. The case study described herein compares a conventional design process of a car floor spot welding station to the design approach using virtual commissioning. The robotic welding cell is controlled by a PLC integrated in a simulation environment that uses two industrial robots created in the Process Simulate Robotics application of Siemens Tecnomatix®.

© 2018, The Brazilian Society of Mechanical Sciences and Engineering.This paper presents the development of design to center of gravity (DT_CG) method, a new member of the DFX (design-for-excellence) design methodology. DT_CG constantly updates the position of the center of gravity of a product under development and inputs it as a requirement into the conceptual phase of the product development process. The CG requirement is yet another requirement to be considered and balanced with others such as weight, cost, and assembly within the Integrated Product Development. The DT_CG method has been successfully applied to the design of a robot end-effector constituted of components that execute a number of functions required for manufacturing processes as drilling, welding, or sanding. The DT_CG was essential to find the geometric constraints between the end-effector CG and the robot’s TCP (tool center point). Despite this paper describes a robotic application, the DT_CG design method is presented in a generic way so that it may be used in any product design where the position of the CG has to be taken into account right from the beginning of the design conceptual phase.

© 2017 Elsevier B.V.Currently, neural networks deliver state of the art performance on multiple machine learning tasks, mainly because of their ability to learn features. However, the architecture of the neural network still requires problem-specific tuning and the long training times and hardware requirements remain an issue. In this work, the Multi-Scale Auto-Tuned Extreme Learning Machine (MSATELM) architecture is proposed, which does not require any manual feature crafting or architecture tuning and automatically learns structure and weights using an auto-tuned ELM as building block. It learns a simple model that achieves the required accuracy. The GPU implementation in OpenCL allows handling any number of samples while still delivering portable code and high performance. Results on MNIST, CIFAR-10 and UCI datasets demonstrate that this approach provides competitive results even though no problem-specific tuning is used.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.This paper presents a rationale for structuring a distributed human factors laboratory for future air systems. The distributed herein refers to two aspects: content and geographic. As for content, the laboratory is structured in two levels, namely, individual, and team. As for geographic, the laboratory infrastructure is distributed in three physically separate facilities, namely, Department of Computer and Information Science (IDA) and Department of Management and Engineering (IEI) from Linköping University - Sweden and the Competence Center in Manufacturing from the Aeronautics Institute of Technology (ITA) - Brazil.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.This paper describes the utilization of large amount of data to analyze the performance of pilots under different flight circumstances assessing the influence of human factors like workload and pilot experience. The methodological approach described herein consists of establishing main research questions, defining hypothesis, acquiring and analyzing simulated flight data. Methods include subjective and objective measurements of qualitative and quantitative nature. After declaring the research questions and hypothesis, simulated flights were performed and analyzed. The preliminary results inspired the creation of a roadmap for assessing Human Factors influence on pilot performance based on simulated flights.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.A great amount of aeronautical accidents and incidents in the last decades are associated with human causes, which can be related not only to the human itself, but with the human machine interface associated to a piloting task. This work presents a preliminary experiment that aims at analysing how a set of different tasks increases the workload of the pilot and how pilot's performance is affected by the increasing workload under different flight conditions (normal and abnormal). The experimental procedure considers 3 pilots executing a take-off and stabilization mission, where a group of tasks, based on the MATB-II approach, are systematically presented to the pilot. Variables such as altitude, heading, rate of climb and yaw rate, are measured. The results show that the variables measured near the pilot input command are more affected by the different levels of workload.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.Embraer was founded in 1969 to accomplish the vision of the Brazilian government to have the capacity of designing and manufacturing airplanes. The company is organized in three business units: Commercial Aviation, Executive Jets and Defense&Security. In order to have recently graduated engineers prepared to tackle its future challenges, Embraer created in 2001 the PEE - Engineering Specialization Program in partnership with ITA - Aeronautics Institute of Technology. In 2016, more than 6,500 candidates applied for 30 positions. Since 2004, PEE is following the principles of CDIO initiative principles in both the selection of young engineer's process and curriculum design philosophy for the graduate program. As a strategy from Engineering and Technology Department of Embraer, the company needs to adapt its selection process and the curriculum for new engineers to fit to current and future challenges. For instance, from 2008 until now, the number of delivered executive jets dropped from 1315 to 700. Trying to avoid commoditization, the company looks for diversification, searching for new business opportunities. Therefore, offering more services is a natural source of new revenues. More than that, to develop a product and its services simultaneously (Product Service System - PSS from the literature) is a company current objective considering, for instance, the new digital era (Big Data, Industry 4.0 and Internet of Things). To understand how to develop a PSS for the executive jets owners is a major challenge. The other is to present suggestions on how to select and prepare the future engineers of Embraer to be able to conceive, design and implement Product Service Systems for the Executive Aviation Market. For that, a study is being conducted to analyze which competencies and profile are required for that challenge. This paper present as results some guidelines for the selection and education of future engineers of the company in the PSS context.

© 2018, Journal of Aerospace Technology and Management. All rights reserved.Initial Maintenance Review Board Report (MRBR) uses in service operation experience as a reference to define maintenance tasks intervals. However, in general, there is no structured data to compare systems performance and provide useful information to the analysts’ decision-making. Even when engineering judgment is based on certification process, structural design, components intrinsic reliability and so on, the analysts responsible for maintenance tasks definitions tend to choose rather conservative proposals. This article presents a method to optimize preventive maintenance tasks intervals and use structured data based on interval optimization process to define maintenance intervals to those of similar systems under development. The method has been applied in an aircraft manufacturing company using current operation database after regulatory authorities’ approval. As a result, it has been feasible to propose to the selected system, a maintenance task interval 100% higher than the one applicable to a similar system under operation.

© Springer International Publishing AG 2018.This study is one of a series of studies, researching various aspects that all aim at enhanced simulation based certification aiding for aircraft. An experimental within-group design study was performed with 10 participants (5 male, and 5 female). The results showed a significant difference, F(2,16) = 5.11, p = 0.019, in mental workload between an engine failure condition and an normal condition for eye blink frequency. No effect of speed at the engine failure event on mental workload was found.

© Springer International Publishing AG 2018.This paper shows studies for the development of a mathematical model that adequately represents a pilot behavior in the specific task of offset landing, using data-driven modeling techniques. Flight test data was used for the identification procedure. Considerations on the pilot’s cognitive process and mathematical modeling possibilities were discussed to select the most appropriate inputs and outputs for the model. This data was used to identify the model using artificial neural network techniques. The models obtained were validated against the identification data and different data not used in the training process to evaluate the quality of the models. Conclusions include the difficulties of showing the generalization capabilities of those non-linear models and further studies.

© 2017, SBMAC - Sociedade Brasileira de Matemática Aplicada e Computacional.The present work quantifies the fuel consumption of a space vehicle in bi-impulsive interplanetary trajectories with an intermediary swing-by maneuver with the Moon. In this way, an interplanetary patched-conic approximation with a lunar swing-by maneuver is formulated with an important characteristic: the swing-by maneuver is designed before the determination of the trajectory by specifying its geometry. The transfer problem is then solved by a multi-point boundary value problem (MPBVP) with two constraints. The intermediary constraint is related to the geometry of the swing-by maneuver with the Moon, and the terminal constraint is related to the altitude of the arrival at the low orbit around the target planet. The proposed algorithm is built in such way that the MPBVP is split into two-point boundary value problems (TPBVPs): the first one is solved to ensure the satisfying of the intermediary constraint, and the second TPBVP is solved next to satisfy the final constraint. Both TPBVPs are solved by means of Newton–Raphson algorithm. The proposed algorithm is then utilized to determine the Earth–Mars and Earth–Venus trajectories with several geometric configurations. The geometric configuration with the smallest fuel consumption is obtained for both missions and compared to an interplanetary patched-conic approximation without swing-by maneuver with Moon. The results show advantages in performing swing-by maneuver with the Moon for interplanetary missions by saving fuel consumption without much increase of the time of flight.

© 2017, SBMAC - Sociedade Brasileira de Matemática Aplicada e Computacional.A study of Earth–Moon bi-impulsive trajectories is presented in this paper. The motion of the space vehicle is described by the classic planar circular restricted three-body problem. The velocity increments are computed through analytical expressions, which are derived from the development of the Jacobi Integral expression. To determine the trajectories, a new two-point boundary value problem (TPBVP) with prescribed value of Jacobi Integral is formulated. Internal and external trajectories are determined through the solution of this new TPBVP for several times of flight. A relation between the Jacobi Integral and the Kepler’s energy at arrival is derived and several kinds of study are performed. Critical values of the Jacobi Integral, for which the Kepler’s energy of the space vehicle on the arrival trajectory becomes negative, are calculated for several configurations of arrival at the low Moon orbit in both directions: clockwise and counterclockwise. Results show that the proposed method allows the estimation of the fuel consumption before solving the TPBVP, and it facilitates the determination of trajectories with large time of flight. However, increasing values of the time of flight are not necessarily related with the increase of the Jacobi Integral value, which means that the obtaining of new trajectories becomes more difficult as the Jacobi Integral increases. Moreover, the proposed method provides results to be used as initial guess for more complex models and for optimization algorithms in order to minimize the total fuel consumption. For this case, this paper presents an example where an internal trajectory with large time of flight is optimized considering the Sun’s attraction.

© 2018 IAAThe present work formulates an orbital transfer for an Earth-to-Earth mission between non coplanar orbits with different altitudes with a special feature: the occurrence of a lunar flyby during the transfer orbit. This lunar flyby is intended to help change the plane of motion of the spacecraft without fuel consumption. Only two-impulsive trajectories are considered with the velocity increments applied at the initial and final orbits. In order to solve this problem, a 3D patched-conic approximation associated with a two-point boundary value problem is proposed. The same transfer problem is formulated considering the spatial circular restricted three-body problem (SCR3BP). The results of the patched-conic approximation is compared with the results of the SCR3BP showing a good agreement between the models. This work also determines several trajectories in order to perform a study of the fuel consumption considering several inclinations and altitudes of both initial and final orbits around the Earth. The longitude of the ascending node of the initial orbit, and, the altitude of close approach with the Moon during the flyby are also analyzed. According to the total velocity increment analysis, the changing plane assisted by a lunar flyby can be very favorable. Despite the increase of the time of flight, the saving of fuel is considerable. Indeed, the total velocity increment of this kind of maneuver is in some cases better than the velocity increment provided by the bi-parabolic transfer.

© 2017, SBMAC - Sociedade Brasileira de Matemática Aplicada e Computacional.In this work, a study about minimum fuel trajectories in a round trip journey to the Moon is presented. It is assumed that the velocity changes are instantaneous, that is, the propulsion system is capable of delivering impulses such that the fuel consumption is represented by the total velocity increment applied to the space vehicle. It is also assumed that the velocity increments are applied tangentially to the terminal orbits, and, the outgoing trip and the return trip are analyzed separately such that the whole mission is performed with four impulses (two impulses in each trip). The mathematical models used to describe the motion of the space vehicle are three: the lunar patched-conic approximation; the classic planar circular restricted three-body problem, and, the planar bi-circular restricted four-body problem (PBR4BP). For computing the optimal trajectories, the Sequential Gradient-Restoration Algorithm with constraints is used. The influence of the Sun on round trip lunar missions is analyzed through the PBR4BP model. For all models, the trajectories studied are direct ascent maneuvers, and, both the outgoing and return trips are considered. The results obtained through the different models are compared with each other. The optimal results for the PBR4BP model show that a small reduction of the fuel consumption can be achieved if the initial phase angle of the Sun is chosen properly.

© 2017 IEEE.A methodology was developed in this work for the automatic counting of individual seedlings in plantations of Eucalyptus spp from high definition photographs with the help of Scientific Python Libraries from literature. The problem to be investigated was presented and two different ways of solving it were discussed together with their implications. With the algorithm properly validated on training data, an actual business case of seedlings detection and counting out of a mosaic aerial image was proposed as testing data. The high-definition pictures were taken by multispectral sensor onboard an UAV from an Eucalyptus spp plantation stand of approximately 25 hectares and provided by Eldorado Brasil. The results were considered very encouraging, stimulating future works in this line of research.

© 2018, The Brazilian Society of Mechanical Sciences and Engineering.Due to the increase in aircraft systems complexity along the decades and the continuous certification requirement improvements for safer operations, the safety assessment accomplished by systems engineers has been demanding more effort from the specialists to make a complete evaluation of the system and respective interfaces. The capability of predicting the real effects of components failures in the system behavior to make better assessments of their severities and to support troubleshooting processes during aircraft operation has also represented a challenging activity. In that context, the development of computational models and simulation has become a common practice in the industry. Therefore, the aim of the present work was to demonstrate the benefits of working in a cohesive manner with two particular modeling techniques: a physical modeling based computational software and the bond graph concepts, to enhance the specialist’s comprehension about the impacts of particular failures in system performance. As a case study, an aircraft hydraulic brake system has been chosen since it performs important, safety-related functions in aircraft operation. For that purpose, a computational model parameterized in LMS Amesim® software is used, after a deep validation process, to assess the behavior of system relevant variables in normal and faulty operating conditions. In parallel, a bond graph diagram representative of a system component is applied as a support tool to assess typical failure modes and help selection of relevant ones for simulation.

© 2018 IEEE.Shape memory alloy (SMA) wires have extensive use in many areas of the industry nowadays and its development continues reaching new applications as studies progress. This paper proposes a SMA measurement device that uses affordable components, such as the Arduino micro-controller and a LabVIEW programming language interface. With an antagonistic mechanism design, data on temperature, strain and stress is acquired to confirm the measuring capabilities of the full equipped instrument, rendering visualizations of phase transformations and opening way for further development in control and detailed acquisition of shape memory alloy wire properties.

© 2018, The Brazilian Society of Mechanical Sciences and Engineering.In this work, the authors propose a formation control strategy of a group of three multirotor aerial vehicles being able to avoid multiple obstacles and collisions. To deal with this problem, a decentralized architecture is proposed which has one model predictive controller per vehicle including a set of convex constraints on the vehicle’s position to prevent collisions with other agents and different shapes of obstacles. The resulting decentralized scheme controls the formation based on a virtual structure approach. For the purpose of avoiding collisions, each local controller considers the predicted position of every neighbor vehicles. The effectiveness of the developed scheme is demonstrated through numerical simulations considering a “figure-of-eight” as the reference trajectory, and the results show its capability to handle thrust force, obstacle and collision avoidance constraints.

© 2017, Springer Science+Business Media B.V.This paper presents position control of the control surface of an aeroelastic typical section using shape memory alloy (SMA) actuators. The actuator was designed using an antagonistic pair of SMA wires, thus allowing its use to move the control surface to up and down. The mathematical model adopted here describes the relations among aeroelastic section, models of SMA wire heat convection, constitutive law and phase transformations of the SMA. Three types of controllers are presented based on variable structure control approach and the deflection of the control surface via two pairs of antagonistic wires are made in a closed loop system. The effectiveness of the actuation system in positioning the control surface is evaluated numerically.

© 2003-2012 IEEE.The present work describe the use of different maneuvers with intention to improve the identification of latero directional model of an Unmanned Aerial Vehicle (UAV). The best flight datas was selected according to criteria described in this paper. It was used the methodology of 4 M's (Maneuver, Model, Method and Measure) identification, to estimate the parameters of the model.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Morphing wings can optimize their performance during the whole mission profile. Using a morphing wing can make landing speeds lower and flying safer, make wings produce less noise and drag and reduce fuel consumption. This paper describes how a morphing wing is designed, constructed and tested. Table tests show a significant change in air profile is achieved within 1 second of actuation. Wind tunnel tests show that morphing the wing shifts the Cl − α graph. This means that morphing the wing performs the same function as actuating a flap. Therefore, using SMA wire to create a morphing wing is possible and it is proven that morphing wings provide benefits over a normal wing.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.This work presents a methodology for system identification of a large flexible aircraft operating in closed-loop. The feedback in some cases is necessary because the system in open-loop is unstable or because a controller, known or not, is present on system and is not possible to removed it. The synthetic data of a nonlinear dynamic to the aircraft considering three symmetric and two anti-symmetric flexible modes are used in the identification algorithm. The identification algorithm is a non iterative subspace method well applied for both open and closed-loop data. The preliminary results suggest a representative model for the aircraft, obtaining the state-space matrices that are of very interest and used for control system analysis and design.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.This paper proposes a novel LTA platform, the tethered airship that is a merge of airship and tethered aerostat functionalities, combining the navigation abilities of airships and the hovering performance of tethered aerostats that is designed to remain stationary in high wind conditions, to transfer data with high speed data link to the ground base through an electric tether and to fly unlimited time periods. This paper presents the sizing based in a scaled model of the YEZ-2A airship, the designing and fabrication of each component, and the integration that originates the novel tethered airship prototype in which it is validated through flight experiments.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.The present work describes the system identification process of the lateral-directional stability derivatives of an Unmanned Aerial System (UAS) [1]. The Maneuver, Model, Method, Measures and Validation (M4V) [2], is a well known in-flight identification methodology that was applied to the VECTOR-P UAS. The maneuvers adopted to excite the lateral modes of the system were evaluated with the energy spectral density (ESD). The data was acquired during flight tests by the data acquisition system specifically developed to the Vector-P. Finally, the validation of the identified parameters was performed using statistical methods.

© 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.In the context of system failures analysis, the present work aims to demonstrate the benefits of working in a cohesive manner with two particular modeling techniques, a physical modeling-based computational software and the bond graph concepts, when identifying failure modes and assessing the impacts of typical failures in an aircraft hydraulic brake system. The brake system performs an important, safety-related function in aircraft operation.

© Proceedings of ISMA 2018 - International Conference on Noise and Vibration Engineering and USD 2018 - International Conference on Uncertainty in Structural Dynamics. All rights reserved.Due to the increasing complexity of aeronautical systems, it became more and more important to detect possible failures, avoiding costs with maintenance and time out of operation. Modeling techniques and computational softwares made possible to analyze systems behaviour under normal and failure conditions, helping to prevent these problems. In this work, an aircraft anti-skid brake system is considered as a study case. Therefore, the aircraft brake dynamics and the brake system are modeled using Simulink. In the brake model, some common faults are introduced in order to observe its impacts on the braking performance. A model based fault detection and isolation (FDI) method using analytical redundancy relations (ARRs) is proposed. ARRs are equations relating the system constraints. The numerical evaluation of these equations generates residuals indicating the system deviation from its normal operation. The coupling of the Simulink behavior model with the ARRs is presented, permitting the residuals analyses for each failure mode.

© Springer International Publishing AG, part of Springer Nature 2019.This work describes the nonlinear identification applied to an aeroelastic pitch-plunge system using polynomial NARMAX model and a stability analysis. The apparatus is available and consists of a wing typical section with pitch and plunge degrees of freedom. The identification procedure aims to obtain the parameters for the mathematical model including the torsional stiffness as a quadratic polynomial function. The candidate structure to the polynomial model is obtained from discretization of a continuous-time state-space model and the predictions are obtained via the identification procedure using simulated data. The simulation is performed considering the aerodynamics with free stream velocity increased within an established velocity range which includes the flutter phenomenon. In future work, a data acquisition from the experimental apparatus will be performed. The NAR-MAX model indicates a polynomial function of fourth order for the nonlinearity and a stability analysis, discussed in this work, mapping the nonlinear regions.

© 2018, Springer Nature B.V.This contribution deals with fast Earth–Moon transfers with ballistic capture in the patched three-body model. We compute ensembles of preliminary solutions using a model that takes into account the relative inclination of the orbital planes of the primaries. The ballistic capture orbits around the Moon are obtained relying on the hyperbolic invariant structures associated to the collinear Lagrangian points of the Earth–Moon system, and the Sun–Earth system portion of the transfers are quasi-periodic orbits obtained by a genetic algorithm. The trajectories are designed to be good initial guesses to search optimal cost-efficient short-time Earth–Moon transfers with ballistic capture in more realistic models.

© 2017, SBMAC - Sociedade Brasileira de Matemática Aplicada e Computacional.We investigate multistability and global bifurcations in the general standard map, a biparametric two-dimensional map. Departing from the conservative case of the map, we describe the evolution of periodic solutions and their basins of attraction as dissipation builds up, paying special attention on how the biparametric variation affects multistability. We examine general and specific phenomena and behavior for three distinct dynamical regimes, namely small, moderate, and large damping and different forcing amplitudes. Also, we report numerically the mechanism of global bifurcations associated to small chaotic attractors in the multistable system. Several global bifurcations are investigated as dissipation increases. Specifically, through the characterization of an interior, a merging and a boundary crisis, we study the crucial role played by fundamental hyperbolic invariant structures, such as unstable periodic orbits and their stable and unstable invariant manifolds, in the mechanisms by which the phase space is globally transformed.

© 2018, © 2018 Taylor & Francis Group, LLC. Walls made of layers of different materials and sizes, including empty spaces, can be used for modulating energy transfer across such composite structures. By changing layer thicknesses and by using distinct porous and solid materials, the overall cavity Nusselt number can be modified in regard to its traditional behavior found in cavities fully fitted with porous materials or with no obstructions. Numerical simulations of transport equations for such composite systems poses an additional difficulty if one considers the different layers, appropriate interface conditions between them and the need to use one single computational domain for simplicity. Motivated by such engineering application and numerical need, this work presents the analysis about natural convection in a two-dimensional horizontal composite square cavity, using laminar and k-ε turbulence models. Both the one energy equation (1EEM) and two energy equation (2EEM) closures are applied. The composite square cavity is equally divided and formed by three distinct regions. Non-dimensional temperatures are proposed such that the entire computational domain is handled in a single numerical scheme. It was found that the fluid begins to permeate the porous medium for values of Ra greater than 10 6 . Nusselt number values show that for the range of Ra analyzed there are no significant variation between the laminar/turbulent and 1EEM/2EEM model solution. When comparing the effects of Ra, thermal conductivity ratio k s /k f and Da on Nu, results indicate that (Formula presented.) has a greater influence in controlling heat transfer rates across the composite cavity.

© 2018 Taylor & Francis.The aim of this work is to estimate the permeability of porous enclosures for numerical solutions of turbulent natural convection in a square cavity. The motivation is that available permeability correlations were proposed based on force rather than natural convection through permeable media. Although commonly seen as a medium property, permeability is measured with a flow through the permeable structure and, as such, its value may carry a flow type dependency. Here, it is assumed that a fixed amount of a solid conducting material is distributed within the cavity and two mathematical models are used and compared when calculating the cavity Nusselt number. First, a porous-continuum model is considered based on the assumption that the solid and the fluid phases are observed as a single medium, over which volume- and time-averaged transport equations apply. Second, a continuum model is used to solve local momentum and energy equations, in both the solid and void spaces, through a conjugate heat transfer solution. The average Nusselt number at the hot wall obtained from the porous-continuum model for several Darcy numbers are compared with those obtained with the continuum model using up to N = 1,024 obstacles within the cavity. When comparing the two methodologies, this study shows that the average Nusselt number calculated by each approach differs by as much as 32% when the number of obstacles N is increased to 1,024. Based on that, an adjustment on the used correlation for calculating the porous medium permeability is proposed to match the Nusselt numbers calculated with the two models. Results indicate that the use of the new correlation gives results for Nu that differ less than about 4% for the range 4 < N < 1,024.

© 2018 by Begell House, Inc.This work presents a study on double-diffusive free convection in a porous square cavity saturated with a Newtonian fluid under laminar flow simulated with the thermal equilibrium model. Transport equations are discretized using the control-volume method and the system of algebraic equations is relaxed via the SIMPLE algorithm. The effect of Ram and porosity on average Nusselt and Sherwood values was investigated. Results show that as Ram increases, both Nusselt and Sherwood numbers increase, indicating enhancement of heat and mass transfer across the cavity. Further, when the Lewis number is increased while keeping the same thermal properties, reduction of mass diffusivity further enhances flow recirculation for aiding flows (N = 1) within the cavity, which leads to a further increase in Nuw and Shw. When varying the buoyancy ratio N from aiding (N > 0) to opposing flow (N < 0), simulations indicate that when both drives are of equal strength, minimum values for Nusselt and Sherwood occur for N = −1, regardless of Ram. For larger values of |N|, aiding drives will promote fluid rotation in the clockwise direction, for the gradients of T and C applied here, whereas for opposing flows, the fluid rotates in the counterclockwise direction for opposed conditions at the lateral walls. Porosity and thermal conductivity ratio also affect Nuw and Shw.

© 2017 Wiley Publishing Ltd.A critical aspect of standard test methods for fatigue characterization is that they do not provide any information on heat dissipation in the material and involve very expensive experimental campaigns in time and costs. In recent years, thermographic methods capable of reducing testing time have been developed, also providing more information on damage occurring in the material. A commonly used approach is based on the assessment of the temperature plateau during a stepwise loading procedure. At times, however, this approach can fail if temperature stabilization is not achieved. In this regard, in this paper, a new approach based on the assessment of 3 different thermal indexes was proposed to estimate the fatigue limit of 3 stainless steels: AISI 316, 17-4PH, and ASTMA890 grade 4a, respectively, exhibiting fully austenitic, fully martensitic, and duplex biphasic microstructure. The fatigue tests were carried out by using a stepwise loading procedure, under loading ratio of 0.5. The analysis demonstrated the possibility to further reduce testing time and, consequently, the fatigue experimental campaign. Moreover, some ideas are discussed about how to justify the different thermal behaviour of a biphasic stainless steel, in total temperature variation. Moreover, a discussion of results regarding the various thermal behaviours of the investigated steels and a possible correlation with the microstructure has been proposed.

© 2018 IADIS Press. All Rights Reserved.The development of transversal competences is essential for the success of engineers, who need to have the ability to adapt to the new and changing demands posed by modern society and scientific advances. It is a challenge for professors to teach and evaluate transversal competences, since such competences are related to attitudes and values. We present a program, held in an Engineering school, with the goal of motivating young people in STEM (Science, Technology, Engineering and Mathematics) areas. Results from the designed initiatives pointed to success in the development of transversal competences, including problem solving, communication, leadership, teamwork, self-management, creativity and innovation.

© 2018 IADIS Press. All Rights Reserved.Despite the technological development, the digital era, and the fact that Science, Technology, Engineering and Mathematics (STEM) permeates all the modern world, the number of students choosing to pursue a career in STEM areas is very small in comparison to other careers. In particular, considering the gender, the gap increases even more. In this work, we present an industry-university program designed to stimulate STEM education and fostering the female interest and development in these areas. Considering our female undergrad students, the proposal was to engage them in the process, as the main agents. Our students prepared and gave lectures in schools about STEM areas. Together with some faculty members, they also developed and applied workshops based on hands-on and minds-on learning activities to spark young girls’ curiosity in STEM areas. In all activities, it was performed an evaluation of learning outcomes, as STEM skills and interest. The program showed to be effective producing very positive remarks.