© 2019 The Franklin InstituteThis paper deals with a non-ideal system with memory by possessing a fractional damping term. The system is characterized by additional cubic nonlinearity. Based on the time series form of the numerical simulations of this non-ideal model, the nonlinear dynamical response of the system is investigated. A DC electric motor with limited power supply driving by an unbalanced rotating mass provides the non-ideal excitation. To distinguish between periodic and non-periodic behaviors, they are used three different mathematical tools, which are the 0–1 test, scale index and wavelet technique. The response of the considered system is investigated with respect to the fractional damping derivative term and the voltage applied in the DC motor, which is considered as a control parameter. Numerical results showed that, the scale index, 0–1 test and the wavelet transform technique defined very accurately the periodic and non-periodic motions.

© 2019, Krishtel eMaging Solutions Private Limited.Objective: This paper presents a systematic approach to quantify the uncertainties that influences directly the design of a Piezoelectric Vibration Absorber applied to shell structures with arbitrary shape, normally employed in automotive body structures. Methodology: Sensitivity and spectral analyses are performed to study the impact of randomness in the optimal piezoelectric patch implementation in automotive structures. The randomness arising from the manufacturing process of the mechanical structure, such as stamping spring back effects, as well as in the boundary conditions, is considered in the analyses, likewise the effects of variability during the positioning process for piezoelectric patches. The effects of the inherent uncertainties in the dynamic behavior of the mechanical structure, the optimal electromechanical coupling coefficient and the piezoelectric vibration absorber attenuation are presented. Results: The present paper has the advantage of indicating the loss in the vibration attenuation when Piezoelectric Vibration Absorbers are used in arbitrary shape structures, such as automotive hoods, fenders and doors. The Dynamic Vibration Absorber deterministically optimized provides an attenuation of approximately 18 dB in the theoretical model. However, losses of 5 dB in the attenuation can be obtained when the uncertainties are taken into account, and can reach up to 10 dB when the temperature effects are involved, representing more than 50% loss in attenuation for real applications, such as automotive body structures.

© Springer Nature Switzerland AG 2020.The aim of the current work is to discuss the dynamic buckling of a sandwich plate, to identify the response signals, and to find the relevant frequencies and amplitudes. The analyses consider the thin face-sheets of the sandwich plate which are subject to in-plane compressive load lower than the estimated critical value for the local buckling, but the plate is also subject to vibration in specific frequency causing variation of the load amplitude. The dynamic variation of the inplane stress stiffening changes the natural frequencies representing the out-of-plane modes dynamically. The nonlinear variation of the response for the out-of-plane displacements is analyzed with the continuous wavelet transform (CWT) method for characterizing this behavior.

© 2020 Elsevier LtdA unified theory to formulate a family of quasi-2D composite finite elements that capture through-the-thickness effects is proposed. The formulation is based on the superposition of global and local displacement fields and includes thermal effects, as a response to the claim of the scientific community. First are presented the fundamentals of the unified formulation: the kinematic assumptions; the imposition of continuity of displacements and transverse stresses, and of non-homogeneous boundary conditions; and the mathematical manipulations that render its numerical efficiency. Then, the new family of elements is assessed in problems involving different boundary conditions. Results are compared to analytical and highly refined 2D finite elements solutions, providing a benchmark of the elements capabilities. Mesh convergence is assessed, together with the influence of the global and local displacement fields. The numerical efficiency of the formulation is attested and an expansion for a 3D formulation is outlined.

© 2020 World Scientific Publishing Company.In this paper, a canonical transformation is proposed to solve the eigenvalue problem related to the dynamics of rotor-bearing systems. In this problem, all matrices are real, but they may not be symmetric, which leads to the appearance of complex eigenvalues and eigenvectors. The bi-iteration method is selected to solve the original eigenproblem whereas the QR algorithm is adopted to solve the reduced or projected problem. A new canonical transformation of the global eigenproblem which reduces the quadratic eigenproblem to a linear eigenproblem, maintaining numerical stability since all that is required is that the stiffness matrix is well-conditioned, which is always true when it comes to applications in dynamic problems. The proposed technique is good for obtaining dominant eigenvalues and corresponding eigenvectors of real nonsymmetric matrices and it possesses the following properties: (i) the matrix is not transformed, therefore sparsity is maintained, (ii) partial eigensolutions can be obtained and (iii) use may be made of good eigenvectors predictions.

© 2020, The Brazilian Society of Mechanical Sciences and Engineering.The bearing investigation on mechanical joints of composite materials is extensive. The main reason for bearing investigation, in a certain aspect, is related to the variability of parameters associated with bearing behavior. In this sense, theoretical and/or experimental studies have been exhaustively conducted. Depending on the solution obtained, there is a cost/benefit relationship for the problem in question. However, in the case of aeronautical applications, an important factor to be considered is the safety, which reflects into safety margin. In this sense, an excess of tests is needed for design that reflects in high cost and time-consuming. Therefore, simpler approaches are necessary in the pre-design phase, where quick answers are required for the initial product definition. In this way, the present work presents composite bearing tests with two distinct environmental conditions, i.e., low-temperature dry (LTD) and room-temperature dry (RTD) in order to show that there is one procedure to simplify the process and gain cost and time. For this, five different configurations specimens with 12 coupons each one were tested in two different environmental conditions. The fastened joint manufactured used protruding fastener, two different diameters (3/16″ and 5/32″) and three laminates (10, 12 and 14 plies). Based on the ASTM D5961 standard, the experimental results showed a linear response not showed in the literature for composite materials. The proposal presented here showed an excellent way to avoid others tests with different conditions, i.e., with different layups and fastener diameters.

© 2020 SAE International. All Rights Reserved.Residual stress prediction arising from manufacturing processes provides paramount information for the fatigue performance assessment of components subjected to cyclic loading. The determination of the material model to be applied in the numerical model should be taken carefully. This study focuses on the estimation of residual stresses generated after deep rolling of cast iron crankshafts. The researched literature on the field employs the available commercial material codes without closer consideration on their reverse loading capacities. To mitigate this gap, a single element model was used to compare potential material models with tensile-compression experiments. The best fit model was then applied to a previously developed crankshaft deep rolling numerical model. In order to confront the simulation outcomes, residual stresses were measured in two directions on real crankshaft specimens that passed through the same modeled deep rolling process. Electrolytic polishing was used to etch the region of interest and enable in-depth residual stress analysis through X-ray diffraction method. The comparison revealed the model's ability to follow the residual stress state tendency, predicting compressive stresses at the surface, a subsurface peak and eventual transition to the tractive state. Magnitude discrepancies were discussed and hypotheses related to the specimen preparation procedure were raised. Overall, the activities described in this study yielded in a model confidence increase, which further enables its usage into the crankshaft design stage.

© 2020, © 2020 Taylor & Francis.The present study investigates the evolution of the residual stresses in TWIP steels induced by manufacturing chain for the production of automotive body-in-white. Two different manufacturing routes were considered. The first route encompassed a plastic deformation prior to the welding stage, whereas the second involved the spot welding followed by a baking treatment. A convergent approach was adopted to isolate the effects of the first and final manufacturing steps. The findings showed that the plastic deformation prior to the welding stage is not annihilated by the welding thermomechanical cycle. Abrupt hardness gradients along small material fractions are observed. The residual stresses state changes, although its profile is still defined by the welding stage. The post-weld bake treatment showed to promote slight residual stresses relaxation, but it is not effective in inducing the same post-weld residual stresses state for different RSW parameters set.

© 2019 Wiley Publishing Ltd.The requirements for mechanical reliability of automotive crankshafts are continuously increasing, thus pushing the demand for an optimized processing. Nonetheless, the manufacturing-induced residual stresses at critical sites for fatigue enhancement are not clarified in the state-of-the-art on the topic. In particular, there is a lack of information on the effect of final manufacturing stages to improve the component life endurance, such as deep rolling, in the overall stress state while the component is under operational loads. This study deepens the validation of a finite element deep rolling model under development with the aid of an in-house developed crankshaft resonance fatigue test rig. The stress state obtained from the deep rolling simulation was input as a predefined stress field for the simulation of operational conditions experimented at the test rig. Test results produced cracks at the fillet radii of the cast iron crankshafts as anticipated. Overlapping the fractography with the simulation's final stress field yielded interesting correlation with the crack morphology. This contributed with a strong indication of the model correctness. Moreover, it can be further implemented to indicate whether the process parameters such as roller force and angle are fully optimized for each particular crankshaft application.

© 2019 Elsevier Masson SASThe accuracy of the results obtained with Finite Element Methods depends on the basis functions employed to approximate the displacement fields. If the beam is very thin, there can be shear locking and the numerical approximation leads to erroneous solutions. In this work, shear locking is analyzed by calculating expressly the curves of the transverse deflection, the cross-section rotation, and the shear strain in different approaches. The influence of the ratio between the shear stiffness and the bending stiffness is explicitly shown when force and moment loads are applied. It is concluded that the locking behavior at nodes is not the decisive factor to assess the quality of the solution. The important point is to analyze the entire curves when the ratio between the stiffnesses is varied. It is verified that the mixed interpolation and the discrete shear gap approaches are superior to the pure displacement and to the field consistency approaches.

© 2019 Elsevier B.V.Manufactured components are submitted to thermo-mechanical loads that can blemish their surface integrity and change the inherent residual stress distribution. The discontinuous machining process is relevant to the integrity conception because of their potential application at the end of the manufacturing chain. In order to consolidate a method to predict the residual stress state with a reduced CPU effort, this paper addresses the prediction of residual stress fields resulting from the milling process. The approach is using the hybrid FEM approach combined with the analysis of the plastic flow. The results obtained point out to the validity of the combination of the hybrid method and the visualization of the equivalent stress and equivalent strain rates. Moreover, a direct correspondence between the references and experimental dataset was observed, even when the input data for the model is associated with macro-loads obtained by piezoelectric platform measurements. The determination of the stress state as residual stress in mainly associated to the mesh convergence and the time to equilibrate the plastic flow. A conclusion is drawn regarding the viability of applying the same combination for other manufacturing processes.

© 2020. All Rights Reserved.In this work, a numerical study of flow around an airfoil with wavy leading edge is presented at a Reynolds number of 3×106. The flow is resolved by considering the RANS (Reynolds Average Navier-Stokes) equations. The baseline geometry is based on the NACA 0021 profile. The wavy leading edge has an amplitude of 3% and wavelength of 11%, both with respect to the airfoil chord. Cases without and with wavy leading edges are simulated and compared. Initially, studies of the numerical sensitivity with respect to the obtained results, considering aspects such as turbulence modeling and mesh refinement, are carried out as well as by comparison with corresponding results in the literature. Numerical data such as pressure distribution, shear stress lines on the wing surface, and aerodynamics coefficients are used to describe and investigate the flow features around the wavy leading airfoil. Comparisons between the straight leading edge and the wavy leading edge cases shows an increase of the maximum lift coefficient as well as stall angle for the wavy leading edge configuration. In addition, at an angle of attack near the stall, the present numerical results shows an increase of the drag coefficient with the wavy leading edge airfoil when compared with the corresponding straight leading edge case.

Copyright © 2020 American Chemical Society.Modification of electronic and chemical properties of a material by the introduction of another element into its lattice is one of the most common methods for designing new catalysts for different applications. In this work the effect of modifying molybdenum carbide with transition metals (Fe, Co, Ni, Cu), TM-Mo2C composites, upon the catalytic activity toward hydrogen evolution reaction (HER) in mild acidic and alkaline media has been studied. Catalysts were prepared by carbothermal reduction of molybdenum and TM oxides precursors and were characterized by different physicochemical techniques. Results evidenced a strong pH effect on the catalytic performance of TM-Mo2C, while, at pH = 5, inclusion of TM into the Mo2C lattice has a deleterious effect on the HER activity and, at pH = 9, a promoting effect was observed, highlighting the importance of considering specific operation conditions during the catalyst design process. Analysis of in situ near-edge X-ray adsorption data reveals a decrease on the oxidation state and average bond ionicity of dopant metal upon a pH increase, shedding light of the different effects of TMs on the resulting HER activity in acidic and alkaline media. Finally, stability tests demonstrated no deterioration on catalysts' performance after 8 h of continuous cycling within the HER working range, confirming the suitability of Mo2C materials as promising HER catalysts.

© 2020 Author(s).In this work, the oxygen reduction reaction (ORR) on tellurium-modified Pt(111) surfaces has been studied. Adsorption of Te adatoms on Pt(111) progressively shifts toward less positive values of both the ORR reaction onset and the half-wave potential in 0.1M HClO4 for 0 < θTe < 0.25. However, at θTe > 0.25, the ORR activity increases relative to the one at θTe < 0.25, but remains lower than that on clean Pt(111). Results were analyzed in light of simulations of kinetic currents as a function of θTe, calculated by employing a simple mean field model including both site blocking and electronic effects. Inside this framework, experimental data are best explained by considering that oxygenated Te species inhibit the ORR by either negatively modifying adsorption energies of reaction intermediates or combined site-blocking and electronic effects. A redox ORR catalysis due to redox properties of Te adatoms is discarded. Contrarily, in 0.05M H2SO4, a positive catalytic effect has been found, interpreted in terms of a competitive adsorption-desorption mechanism involving the replacement of adsorbed sulfate by Te adatoms. On the other hand, despite the strong site-blocking effect on Hads and OHads adsorption by Te adatoms, it appears that the reduced Te-Pt(111) adlayer does not inhibit the reaction, suggesting different active sites for Hads and OHads adsorption and for the rate-determining step of the ORR mechanism.

© 2020, Springer-Verlag London Ltd., part of Springer Nature.This research had the objective of investigating the viability of using niobium carbide–Nickel binder-cemented carbides as an alternative material for cutting tools. The high hardness and high wear resistance associated with niobium carbide (NbC) fulfills one of the main requirements for cutting tool material. In order to achieve this objective, insert tools with square shapes were manufactured using samples at 5 different grades. The samples were developed with different ratios of NbC carbide/Ni binder, compaction parameters, and sintering conditions. The samples were qualified in terms of micro-hardness and physical properties. The inserts were also qualified in terms of their macro-geometry, surface finish, and cutting edge micro-geometry. Machining experiments were performed under different cutting parameters on tempered ANSI 4340 steel workpieces. Flank wear progression was the control parameter, and wear analyses were made using a CCD camera and SEM/EDS. The main wear mechanisms observed were abrasion, followed by adhesion, while no traces of tribooxidation and diffusion were observed. The results led to the conclusion that the ratio of NbC carbide/Ni binder had the greatest influence on wear, but the leading parameter is the sintering conditions.

© 2020 The Author(s). Published by Cambridge University Press.Ensemble data assimilation methods integrate measurement data and computational flow models to estimate the state of fluid systems in a robust, scalable way. However, discretization errors in the dynamical and observation models lead to biased forecasts and poor estimator performance. We propose a low-rank representation for this bias, whose dynamics is modelled by data-informed, time-correlated processes. State and bias parameters are simultaneously corrected online with the ensemble Kalman filter. The proposed methodology is then applied to the problem of estimating the state of a two-dimensional flow at modest Reynolds number using an ensemble of coarse-mesh simulations and pressure measurements at the surface of an immersed body in a synthetic experiment framework. Using an ensemble size of 60, the bias-aware estimator is demonstrated to achieve at least 70 % error reduction when compared to its bias-blind counterpart. Strategies to determine the bias statistics and their impact on the estimator performance are discussed.

© 2020, Springer-Verlag GmbH Germany, part of Springer Nature.This work deals with the characterization of the closed-loop control performance aiming at the delay of transition. We focus on convective wavepackets, typical of the initial stages of transition to turbulence, starting with the linearized Kuramoto–Sivashinsky equation 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 characterization is then extended to the 2D Blasius boundary layer. The objective of this study is to explore how the sensor–actuator placement affects the optimal control problem, formulated using linear quadratic Gaussian (LQG) regulators. This is carried out by evaluating errors of the optimal estimator at positions where control gains are significant, through a proposed metric, labelled as γ. Results show, in quantitative manner, why some choices of sensor–actuator placement are more effective than others for flow control: good (respectively, bad) closed-loop performance is obtained when estimation errors are low (respectively, high) in the regions with significant gains in the full-state-feedback problem. Unsatisfactory performance is further understood as dominant estimation error modes that overlap spatially with control gains, which shows directions for improvement of a given set-up by moving sensors or actuators. The proposed metric and analysis explain most trends in closed-loop performance as a function of sensor and actuator position, obtained for the model problem and for the 2D Blasius boundary layer. The spatial characterization of the γ-metric provides thus a valuable and intuitive tool for the problem of sensor–actuator placement, targeting here transition delay but possibly extending to other amplifier-type flows.

© 2020 Elsevier Inc.Turbulent channel flow was analysed using direct numerical simulations at friction Reynolds numbers Reτ=180 and 550. The databases were studied using spectral proper orthogonal decomposition (SPOD) to identify dominant near-wall coherent structures, most of which turn out to be streaks and streamwise vortices. Resolvent analysis was used as a theoretical approach to model such structures, as it allows the identification of the optimal forcing and most amplified flow response; the latter may be related to the observed relevant structures obtained by SPOD, especially if the gain between forcing and response is much larger than what is found for suboptimal forcings or if the non-linear forcing is white noise. Results from SPOD and resolvent analysis were compared for several combinations of frequencies and wavenumbers. For both Reynolds numbers, the best agreement between SPOD and resolvent modes was observed for the cases where the lift-up mechanism from resolvent analysis is present, which are also the cases where the optimal resolvent gain is dominant. These results confirm the outcomes in our previous studies (Abreu et al., 2019; Abreu et al., 2020), where we used a DNS database of a pipe flow for the same Reynolds numbers.

© The Author(s), 2020.Linearisation of the Navier-Stokes equations about the mean of a turbulent flow forms the foundation of popular models for energy amplification and coherent structures, including resolvent analysis. While the Navier-Stokes equations can be equivalently written using many different sets of dependent variables, we show that the properties of the linear operator obtained via linearisation about the mean depend on the variables in which the equations are written prior to linearisation, and can be modified under nonlinear transformation of variables. For example, we show that using primitive and conservative variables leads to differences in the singular values and modes of the resolvent operator for turbulent jets, and that the differences become more severe as variable-density effects increase. This lack of uniqueness of mean-flow-based linear analysis provides new opportunities for optimising models by specific choice of variables while also highlighting the importance of carefully accounting for the nonlinear terms that act as a forcing on the resolvent operator.

© 2020, Springer-Verlag GmbH Germany, part of Springer Nature.The problem of finding optimal forcing and response for unbounded base flows, exemplified by the Blasius boundary layer, is assessed by means of a locally parallel resolvent analysis. A new analysis of previous results in the literature, which stated that a maximum resolvent gain occurs for spanwise wavenumber kz≈ 0.2 , revealed that this result was not domain converged, and larger domains lead to peak amplification for kz→ 0 ; this result is seen to depend strongly on domain size. It is seen that forcing and response modes for low frequency and wavenumber tend to be extended throughout the computational domain, with substantial support in the free stream. Free-stream modes and their gains are found analytically by considering the resolvent operator for uniform flow, and it is seen that low frequencies and wavenumbers lead to a dominance of such free-stream modes in the resolvent analysis of boundary layers. The lack of domain convergence is explained by the analysis, as gains scale with the square of the domain height. We then propose a new approach to evaluate the resolvent gains for this kind of unbounded flows, by means of a weighting function for the chosen norm that neglects response modes above a cut-off height yp, typically placed outside the boundary layer thickness; this ensures that relevant responses will only be sought in a region of interest, which here corresponds to the boundary layer. The method proved to solve the problem raised by the presence of free-stream modes, resulting in domain-converged forcing and response modes with the shape of streamwise vortices and streaks, respectively. The results were also shown to be independent of the choice of the filter parameters, leading to converged gains for the whole spectrum.

© The Author(s), 2020.In resolvent analyses of turbulent channel flows it has been common practice to neglect or model the nonlinear forcing term that forms the input of the resolvent. However, the spatiotemporal structure of this term is mostly unknown. Here, this nonlinear forcing term is quantified. The Fourier transform of its two-point space-time correlation, its cross-spectral density (CSD), is computed. The CSD is evaluated for two channel flows at friction Reynolds numbers Reτ = 179 and Reτ = 543 via direct numerical simulations (DNS). The CSDs are computed for energetic structures typical of buffer-layer and large-scale motions, for different temporal frequencies. It is found that the forcing is structured and that its solenoidal part, which is the only one affecting the velocity field, is the combination of an oblique streamwise vortical forcing and a streamwise component that counteract each other, as in a destructive interference. It is shown that a rank-2 approximation of the forcing, with only the most energetic spectral proper orthogonal decomposition (SPOD) modes, leads to the bulk of the response. Moreover, it is found that the nonlinear forcing term has a non-negligible projection onto the linear sub-optimal forcings of resolvent analysis, which demonstrates that the linear optimal forcing is not representative of the nonlinear forcing. Finally, it is clarified that the Cess eddy-viscosity-modelled forcing improves the accuracy of resolvent analysis prediction because the modelled forcing projects onto the linear sub-optimal forcings similarly to DNS data.

© The Author(s), 2020. Published by Cambridge University Press.Direct numerical simulations, performed with a high-order spectral-element method, are used to study coherent structures in turbulent pipe flow at friction Reynolds numbers and. The database was analysed using spectral proper orthogonal decomposition (SPOD) to identify energetically dominant coherent structures, most of which turn out to be streaks and quasi-streamwise vortices. To understand how such structures can be modelled, the linear flow responses to harmonic forcing were computed using the singular value decomposition of the resolvent operator, using the mean field as a base flow. The SPOD and resolvent analysis were calculated for several combinations of frequencies and wavenumbers, allowing the mapping out of similarities between SPOD modes and optimal responses for a wide range of relevant scales in turbulent pipe flows. In order to explore physical reasons behind the agreement between both methods, an indicator of lift-up mechanism in the resolvent analysis was introduced, activated when optimal forcing is dominated by the wall-normal and azimuthal components, and associated response corresponds to streaks of streamwise velocity. Good agreement between leading SPOD and resolvent modes is observed in a large region of parameter space. In this region, a significant gain separation is found in resolvent analysis, which may be attributed to the strong amplification associated with the lift-up mechanism, here understood as nonlinear forcing terms leading to the appearance of streamwise vortices, which in turn form high-amplitude streaks. For both Reynolds numbers, the observed concordances were generally for structures with large energy in the buffer layer. The results highlight resolvent analysis as a pertinent reduced-order model for coherent structures in wall-bounded turbulence, particularly for streamwise elongated structures corresponding to near-wall streamwise vortices and streaks.

© The Author(s), 2020. Published by Cambridge University Press.A model problem for analysing the interaction between coherent structures in shear flows with the presence of a convective instability is proposed in this work. Starting from Couette flow, a permanent forcing in the shape of a hyperbolic tangent is introduced in the laminar equations, leading to a wall-bounded flow with an inflection point, which triggers a hydrodynamic instability. Temporal linear stability analysis applied to this new flow model shows that this flow is unstable at low Reynolds numbers, giving rise to Kelvin-Helmholtz-like vortices. Due to the presence of shear, streaks and rolls (streamwise vortices), predicted by resolvent analysis, are also present in the flow, and these structures will interact with vortices via oblique waves. Results of locally parallel analysis inspired the design of a computational box for a direct numerical simulation of such flow and the numerical results exhibit a limit cycle involving streaks, vortices, rolls, oblique waves and the mean flow, so that the flow becomes periodically unstable for the present case. The flow dynamics is shown to reproduce some of the features of jets and mixing layers, such as jitter and translational instability, showing that the present model can potentially clarify some of the phenomena involved in the turbulent dynamics of such flows.

© © The Author(s), 2020. Published by Cambridge University Press.Three amplification mechanisms present in turbulent jets, namely lift-up, Kelvin-Helmholtz and Orr, are characterized via global resolvent analysis and spectral proper orthogonal decomposition (SPOD) over a range of Mach numbers. The lift-up mechanism was recently identified in turbulent jets via local analysis by Nogueira et al. (J. Fluid Mech., vol. 873, 2019, pp. 211-237) at low Strouhal number and non-zero azimuthal wavenumbers . In these limits, a global SPOD analysis of data from high-fidelity simulations reveals streamwise vortices and streaks similar to those found in turbulent wall-bounded flows. These structures are in qualitative agreement with the global resolvent analysis, which shows that they are a response to upstream forcing of streamwise vorticity near the nozzle exit. Analysis of mode shapes, component-wise amplitudes and sensitivity analysis distinguishes the three mechanisms and the regions of frequency-wavenumber space where each dominates, finding lift-up to be dominant as. Finally, SPOD and resolvent analyses of localized regions show that the lift-up mechanism is present throughout the jet, with a dominant azimuthal wavenumber inversely proportional to streamwise distance from the nozzle, with streaks of azimuthal wavenumber exceeding five near the nozzle, and wavenumbers one and two most energetic far downstream of the potential core.

© The Author(s), 2020. Published by Cambridge University Press.An analysis of the statistics of the nonlinear terms in resolvent analysis is performed in this work for turbulent Couette flow at Reynolds number 400. Data from a direct numerical simulation of a minimal flow unit is used to compute the covariance matrix of the velocity. From the same data, we computed the nonlinear terms of the Navier-Stokes equations (treated as forcing), which allowed us to compute the covariance matrix of the forcing. The quantitative relation between the two covariances via the resolvent operator is confirmed here for the first time, accounting for relevant signal processing issues related to the windowing procedure for frequency-domain quantities. Such exact correspondence allowed the eduction of the most relevant force components for the dominant structures in this flow, which participate in the self-sustaining cycle of turbulence: (i) streamwise vortices and streaks, and (ii) spanwise-coherent fluctuations of spanwise velocity. The results show a dominance by a subset of the nonlinear terms for the prediction of the full statistics of streamwise vortices and streaks; a single term is seen to be dominant for spanwise motions. A relevant feature observed in these cases is that the forcing covariance is dominated by its first eigenfunction, showing that nonlinear terms also have a coherent structure at low frequencies in this flow. Different forcing components are also coherent between them, which leads to constructive and destructive interferences that greatly modify the flow response. These are key features of forcing 'colour' for the present flow.

© 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.A comparative study of the acoustic far-field radiation of a subsonic jet near a folded plate with an opening, intended to represent a flapped wing with thrust gate, is presented in this work. Three openings with different widths were used to evaluate experimentally the influence of the gaps in the far-field noise radiation, for two folding angles. Boundary Element Method (BEM) simulations with a wavepacket model to represent the jet acoustic source were both used to calculate the noise far-field for comparison with the patterns found experimentally and for investigating the acoustic field at others points. The BEM simulations showed trends similar to those found experimentally. Through parametric simulations, it was also possible to estimate that openings widths greater than one diameter do not contribute significantly to reducing the far-field noise. The results show that even the smallest tested openings were able to reduce the noise in the far-field for the tested positions.

© American Institute of Aeronautics and Astronautics Inc.. All rights reserved.An investigation is carried out to evaluate how an external uniform stream affects turbulent-jet coherent structures. The presence of this uniform stream outside the jet represents the effect of forward flight on the velocity field. Coherent structures are modelled as wave packets, and the flight effect is studied using the parabolized stability equations (PSEs). Measurements of mean base flows and axial velocity fluctuations on the jet centerline at assumed flight conditions are described. The velocity fields were supplied to a PSE model to retrieve the wave packet signatures of axial velocity fluctuations. Overall results are in good agreement with experimental measurements. There is an observed increase in wave packet wavelengths and phase velocities (with respect to the nozzle) as flight velocity increases. Also, axial amplification rates are determined and show stabilization in the near-nozzle region, which is confirmed by experimental power spectral densities on the jet centerline. This tendency holds as the freestream velocity increases.

© The Author(s), 2020. Published by Cambridge University Press.We extend the resolvent-based estimation approach recently introduced by Towne etal. (J. Fluid Mech., vol. 883, 2020, A17) to obtain optimal, non-causal estimates of time-varying flow quantities from low-rank measurements. We derive optimal transfer functions between the measurements and certain nonlinear terms that act as a forcing on the linearised Navier-Stokes equations, and show that the resulting transfer function to the flow state is equivalent to a multiple-input, multiple-output Wiener filter if the colour of the forcing statistics is known. A matrix-free implementation is developed based on integration of the direct and adjoint linearised Navier-Stokes operators, enabling application to the large systems encountered for transitional and turbulent flows without the need for a priori model reduction. Using a linearised Ginzburg-Landau problem, we show that the non-casual resolvent-based method outperforms a casual Kalman filter for general sensor configurations and recovers the Kalman filter transfer function in specific cases, leading to causal estimates at a significantly reduced computational cost. Additionally, our method is shown to be more accurate and robust than popular approaches based on truncation of the resolvent operator to its leading modes. The applicability of the method to transitional and turbulent flows is demonstrated via application to a (linearised) transitional boundary layer and a (nonlinear) turbulent channel flow. Errors on the order of 2A are achieved for the boundary layer, and the channel flow case highlights the need to account for the forcing colour to achieve accurate flow estimates. In practice, our method can be used as a post-processing tool to reconstruct unmeasured quantities from limited experimental data, and, in cases where the transfer function can be accurately truncated to its causal components, as a low-cost estimator for flow control.

© 2020 Elsevier LtdRecent aircraft are increasingly presenting unconventional wing configurations, resulting in unusual aeroelastic responses and consequently giving rise to different technological strategies to enhance aeroelastic stability. Among them, the technique of stress stiffening by piezoelectric actuation emerged as a promising technological solution to improve the aeroelastic stability of structures with both ends axially constrained. Therefore, an aeroelastic model employing smart composite beam elements and time domain aerodynamic loads with strip theory for stress stiffening aeroelastic problems was developed and carefully validated. In addition, the effect of bending-torsion coupling provided by concentrated masses on the aeroelastic response of the structure is also taken into account, which was included by the presence of a slender ballast arbitrarily positioned along the span and chord. Parametric studies were performed investigating the influence of aspect ratio, fiber orientation angle, ballast position, as well as piezoelectric unit position along the span and its input voltage. Results showed a promising performance of such technique, as it could increase the bandwidth of two flexible modes associated with the flutter mechanism.

© 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The constant demmand for more efficient aircraft design has resulted in a progressive reduction of the frequency separation between rigid-body and elastic modes, so that the effects of aeroelasticity upon handling qualities cannot be discarded anymore. One of these undesirable effects is the biodynamic feedthrough, in which structural vibration at the cockpit is transmitted by the human pilot to involuntary commands at the inceptors. If there is an instability in the closed-loop formed by the pilot and the aircraft, then a Pilot-Augmented Oscillation may be verified. This phenomenon is similar, although very different in its cause, to the more famous Pilot-Induced Oscillation one. Several handling qualities criteria were proposed in the past to analyze and mitigate the Pilot-Induced Oscillation problem. This paper aims then to propose a new handling qualities criterion, focused on the Pilot-Augmented Oscillations problem.

© 2020 The Author(s). published on behalf of Materials Research Society by Cambridge University Press.Austenitic stainless steel is used in several industrial branches due to its mechanical and thermal properties, and to its good corrosion resistance. With low cost and biocompatibility, it is used to manufacture prostheses and devices for bone fixation. However, direct contact with body fluids may cause corrosion. Thin films of FeAlCr intermetallic alloy can be used to increase service life of prostheses and avoid replacement surgeries. The aim of this work was to cover the austenitic stainless steel to study the effect of target-substrate distance on the film characteristics. Coatings were performed using the magnetron sputtering technique with the substrate positioned at different distances from the target. The influence on film thickness, morphology, roughness, and adhesion to the substrate was investigated. The thin films of FeAlCr (160 nm thick deposited at 100 mm far from the substrate) were formed by smaller particles (11.2 nm long), densely packed (551,000 particles/mm2), with flat and regular appearance, and greater adherence to the substrate.

© 2020 Universidade Federal de Sao Carlos. All rights reserved.This work reports how the solar conversion efficiency of dye-sensitized solar cells (DSSCs) depends on the crystalline structure of both the compact TiO2 blocking layer (BL) and homoepitaxially grown porous TiO2 mesoporous structure. The films were grown by simultaneous sputtering of titanium targets by DC magnetron and by high-power impulse magnetron systems (HiPIMS). The deposition conditions were managed to produce in situ dense BLs and porous TiO2 films. The only variable was the polarization of the BLs (0 to -200V). The polarization caused phase transformations from pure anatase phase through rutile-anatase mixed phases to rutile phase. The polarization results in decreasing intensity of the anatase (101) peak of the porous layers. The latter promptly decreased linearly the value of the short-current Isc and exponentially the open-circuit voltage Voc of the cells. Another inference is the surface energy of the BLs, which follows an exponential decay as a function of the film polarization. XPS study of the Ti 2p3/2 – Ti 2p1/2 doublet reveals an appearance of a shake-up satellite, whose area exponentially decreases as the polarization potential rises. This phenomenon is discussed and related with other physical aspects of the homo-epitaxially grown films with different texture. The anatase phase content and its purity predefined by the experimental conditions determine the quality of the DSSC, as well as other components such as the dye type, the electrolyte, and the electrode materials.

© 2020 by the authors.This work proposes the use of a dielectric barrier discharge (DBD) reactor operating at atmospheric pressure (AP) using air and sub-atmospheric pressure (SAP) using air or argon to treat polyamide 6.6 (PA6.6) fabrics. Here, plasma dosages corresponding to 37.5 kW·min·m-2 for AP and 7.5 kW·min·m-2 for SAP in air or argon were used. The hydrophilicity aging effect property of untreated and DBD-treated PA6.6 samples was evaluated from the apparent contact angle. The surface changes in physical microstructure were studied by field emission scanning electron microscopy (FE-SEM). To prove the changes in chemical functional groups in the fibers, Fourier transform infrared spectroscopy (FTIR) was used, and the change in surface bonds was evaluated by energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). In addition, the whiteness effect was investigated by the color spectrophotometry (Datacolor) technique. The results showed that the increase in surface roughness by the SAP DBD treatment contributed to a decrease in and maintenance of the hydrophilicity of PA6.6 fabrics for longer. The SAP DBD in air treatment promoted an enhancement of the aging effect with a low plasma dosage (5-fold reduction compared with AP DBD treatment). Finally, the SAP DBD treatment using argon functionalizes the fabric surface more efficiently than DBD treatments in air.

© 2020 by the authors. Licensee MDPI, Basel, Switzerland.Black TiO2 materials have been quite widely explored due to their large solar absorption and superior photocatalytic activity. In this paper, the blackening process of titanium dioxide (TiO2) thin film using the hollow cathode hydrogen plasma (HCHP) technique is reported. First, pristine anatase TiO2 films were grown by magnetron sputtering onto silicon and cover glass substrates and then annealed at 450◦C for 2 h. Then, the as-grown TiO2 films were treated with HCHP for 15 min. The physical, chemical and morphological properties of the films were analyzed by profilometry, X-ray diffraction (XRD), UV-Vis spectrophotometry, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques. Electrical and photocatalytic measurements were performed by four-point probe and methylene blue UV degradation assays, respectively. The results showed that the black TiO2 film is highly absorbent in the UV-visible region, has low electrical resistance and greater surface area compared to the non-treated TiO2 film. These properties of black TiO2 film, as well as its performance as a photocatalytic agent, were investigated, indicating the superior quality of this material in thin film form and the promising potential of the HCHP treatment to produce hydrogenated TiO2 in short process time.

© 2020 Elsevier Ltd. All rights reserved.An experimental study on the degradation of organic compounds from radioactive oil sludge by the ozonation process is presented. The effects of different concentrations of ozone in the oil sludge degradation over time were investigated. The experiments were performed in a 0.125 L glass reactor with magnetic stirring and a diffuser plate at the bottom to feed the ozone. The ozone concentration varied from 13 to 53 mg L-1 and the total interaction time was 1 h. To investigate the physicochemical properties of the oil sludge (solid and liquid components) prior to and after the treatment, multiple analytical characterization methods were used: Thermal Gravimetric Analysis, X-ray diffraction, Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy, Fourier Transform Infrared spectroscopy, Spectrophotometer, and Residual Gas Analyzer. The most perceptive change is in the color of the liquid medium turned from dark brown to light yellow, especially under ozone concentrations higher than 33 mg L-1. Absorbance values decreased about 3.5 times after 30 min of treatment with [O3] =53 mg L-1. FTIR spectroscopy showed that the bands associated with the CH3 and CeH in CH2 disappeared during treatment. On the other hand, a greater presence of C]C aromatics was observed. By residual gas analysis, various organic and inorganic gases were identified during the treatment, such as CH4, H2, CO2, and H2S. Finally, the ozonation of the oil sludge proved to be effective, due to its high reaction capacity.

© 2020The present article aims to implement and investigate a different preconditioning method based in a three-dimensional in-house compressible CFD code that ensures the robustness and numerical stability to determine the flowfield considering low Mach number flow. The present preconditioning method involve two different methodologies developed by references [8, 32]. The CFD solver was developed to calculate the Euler and Navier-Stokes equations, numerically, for steady-state regime based on the cell-centered finite volume method (FVM) using Reynolds Averaged Navier-Stokes equations (RANS). The centered second-order scheme was used for the discretization of convective terms from momentum equations. The explicit second-order five-step Runge-Kutta scheme was employed for the time-marching procedure, using an implicit residual smoothing technique to enhance the numerical stability. A local preconditioning method was implemented due to its robustness in predicting low Mach number flows in a compressible CFD code environment. However, for low Mach number flows, near stagnation points, numerical perturbations were amplified generating a stiffness in the convergence rate, which provided an inaccurate solution and numerical stability degradation. Aiming to improve the preconditioning robustness, a flux function and a new limiter were applied to operate with the preconditioning technique based on a pressure sensor. Those corrections re-scale the eigenvectors and ensure the locality of the algorithm, which improves the numerical stability and guarantees the convergence for low-speed flows. The inviscid flow over a NACA 0012 airfoil for compressible and incompressible cases shown accurate and robust solutions. For a viscous flow over a flat plate case in the compressible and incompressible cases, the preconditioning technique purposed in this work supplied good numerical solution in agreement with the analytical solution.

© 2020 Elsevier LtdGrowing environmental concerns are driving the energy market toward the development of thermodynamic cycles to harness renewable energy and waste heat. This manuscript introduces the novel organic Rankine flash cycle, which combines the organic Rankine cycle with the trilateral cycle, merging their advantages in terms of high specific power output and low heat transfer irreversibility, respectively. By comparing the organic Rankine flash cycle to the organic flash cycle, it was found that the proposed architecture reaches a peak exergy efficiency at a more realistic value of two-phase expansion volume flow ratio, consistently achieves higher energy and exergy efficiencies, presents a lower cost, and is not constrained to operate close to the working fluid saturation temperature, promising easier operability. Considering pentane as working fluid, the exergy efficiency of the organic Rankine flash cycle is 18%p higher for a heat source temperature of 150 °C, 12%p for 175 °C, and 4%p for 200 °C. The attractive thermoeconomic performance of the proposed organic Rankine flash cycle highlights the potential of such a cycle as a new paradigm in the ORC panorama, encouraging further investigation towards practical demonstration.

© Royal Aeronautical Society 2019.This paper presents a review of the various aeronautical air conditioning systems that are currently available and discusses possible system configurations in the context of the aeronautical environmental control systems. Descriptions of the standard vapor compression cycle and air cycles are provided. The latter includes, simple-cycle, bootstrap-cycle, simple-bootstrap cycle (3-wheel) and condensing cycle (4-wheel). Water separation and air recirculation systems are also explored. A comparison between vapor compression cycles and air cycles is provided, as well as a comparison between different air cycles. Air cycle units are far less efficient than vapor compression cycle units, but they are lighter and more reliable for an equivalent cooling capacity. Details regarding the aircraft conceptual design phase along with general criteria for the selection of an air conditioning system are provided. Additionally, industry trends and technological advances are examined. Conclusions are compiled to guide the systems engineer in the search for the most appropriate design for a particular application.

© 2019 Elsevier LtdIn an increasingly decentralized energy market, micro gas turbines are seen with great potential due to their low emissions and fuel flexibility, which aligns with growing environmental concerns. Although presenting a relatively low efficiency, these machines could be improved by coupling it with an organic Rankine cycle. This manuscript covers the thermoeconomic design and optimization of such bottoming cycle for a 100 kWe micro gas turbine. The tool employed for such calculations is extensively described and was developed using solely open resources. The results shown that the saturation temperature at ambient pressure was an important variable when the minimum pressure is constrained above ambient and that a high degree of superheating was favored when the recuperated cycle is heated directly by the microturbine flue gases. Pentane was flagged as the best working fluid, generating 14.1 kWe of additional power and increasing the overall electric efficiency from 30 to 34.2%. The Authors show that at the current state of the art an efficiency of around 35% is the upper practical limit for such microturbine organic Rankine cycle combination.

Copyright © 2020 ASMEThis work presents the implementation of an interactive learning platform for turbine design in an engineering teaching environment. Due to the abundance of strategies and problems encountered in a multidisciplinary iterative design process, presenting the student to the multitude of scenarios can be a laborious and time-consuming task, often not possible in one-semester courses for undergraduate students. The developed computational program breaks down the preliminary design methodology into a step-by-step analysis of a single-stage axial turbine for aeronautical application. In it, the student is guided through velocity diagram construction, performance prediction, tridimensional and compressible effects considerations, blade designing as well as accounting for losses. In this interactive learning tool, it is possible to explore the sensitivity and effects of each design choice at various design steps, generating insight and hopefully a more intimate understanding. This exploration generates real-time changes in the output interface, for example the velocity diagrams and major geometrical features, in which the student is able through different trials to observe and compare the impact of different approaches, choices and assumptions. The program is written in Python language and the loss models chosen were Kacker and Okapuu; Dunham and Came; and Ainley and Mathieson. As the same set of design requirements can lead to different - yet optimal - configurations, the student will be given guidelines based on established design methodologies with the aid of graphs and the usual ranges of the calculated parameters found in practice. At the end of this process, the student is able to harvest a final design from which it is possible to generate discussions among a class or examine the suitability of a final product in regards to a proposed assignment, objective or application.

Copyright © 2020 ASMEFilm cooling is an important technique to ensure safe operation and performance fulfillment of turbines. Its ultimate goal is to protect the axial turbine blades from high gas temperatures. An appropriate study is necessary in order to obtain a reliable representation of the flow characteristics involved in such phenomena. Because of the high computational cost of high-fidelity simulations, the low-fidelity simulation method Reynolds Averaged Navier Stokes (RANS) is commonly used in practical configurations. However, the majority of the current turbulent heat flux models fail to accurately predict heat transfer in film cooling flows. Recent work suggests the use of machine learning models to improve turbulent closure in these flows. In the present work, a machine learning model for spatially varying turbulent Prandtl number previously described in the literature is applied to a transverse film cooling flow consisting of a jet square channel. The results obtained in the present work were compared to adiabatic effectiveness experimental data available in the literature to assess the performance of the machine learning model. The results shown that for low blowing ratios (BR =0.2 and BR = 0.4) the proposed machine learning model has poor performance. However, for the case with the highest blowing ratio (BR = 0.8), the proposed model presented better results. These results are then explained in terms of the resulting turbulent Prandtl number field and suggest that the training set is not appropriate for capturing the turbulent heat flux in fully attached jets in crossflow.

Copyright © 2020 ASMEThe aim of this work is the evaluation of different mesh types applied in turbomachines area, in this case in an axial turbine stage used in turbopumps (TP) applications. The tip clearance region was considered in this study because it has high influence in turbomachines performance. Due to the complexity of the tip clearance region, structured mesh generation is not always feasible, therefore it is necessary to generate unstructured meshes that allow flow calculation through Computational Fluid Dynamics (CFD) techniques. The use of different mesh type is an interesting topic when different rotor tip geometries are evaluated, in which the desensitization methods are applied. In this work, only the common flat-tip was consider. Thus, as a first step, unstructured tetrahedral meshes (with prismatic layers close to the surfaces) with different y+ values were generated. After this, turbulent 3-D flow calculations were performed at design and off design conditions, based con Reynolds Averaged Navier-Stokes (RANS) equations. The methodology used is to present in a didactic way, for under and graduate students, the advantages and disadvantages of the unstructured mesh in relation to the structured one, already used in previous research. Unstructured meshes were generated using ICEM software (ANSYS), while structured ones were generated using AxCent software developed by CONCEPTS NREC. The machine under study is the first stage of the hydraulic axial turbine used in the Low Pressure Oxidizer Turbopump (LPOTP) of the Space Shuttle Main Engine (SSME), considering 3.0% tip clearance configuration relative to blade height. All simulations were done using CFX program (ANSYS). The result shows the comparison between the two mesh types considering the difficulty and time generation, discretization quality, effect of y+ parameter variation on flowfield, simulation time, and stage performance parameters calculation for different operating points.

© 2020 ASMENumerical simulations were carried out with the purpose of investigating the effect of applying circumferential grooves at axial compressor casing passive wall treatment to enhance the stall margin and change the tip leakage flow. The tip leakage flow is pointed out as one of the main contributors to stall inception in axial compressors. Hence, it is of major importance to treat appropriately the flow in this region. Circumferential grooves have shown a good performance in enhancing the stall margin in previous researches by changing the flow path in the tip clearance region. In this work, a passive wall treatment with four circumferential grooves was applied in the transonic axial compressor NASA Rotor 37. Its effect on the axial compressor performance and the flow in the tip clearance region was analyzed and set against the results attained for the smooth wall case. A 2.63% increase in the operational range of the axial compressor running at 100%N, was achieved, when compared with the original smooth wall casing configuration. The grooves installed at compressor casing, causes an increase in the flow entropy generation due to the high viscous effects in this gap region, between the rotor tip surface and casing with grooves. These viscous effects cause a drop in the turbomachine efficiency. For the grooves configurations used in this work, an efficiency drop of 0.7% was observed, compared with the original smooth wall. All the simulations were performed based on 3D turbulent flow calculations using Reynolds Averaged Navier-Stokes equations, and the flow eddy viscosity was determined using the two-equation SST turbulence model. The details of the grooves geometrical dimensions and its implementation are described in the paper.

© 2020 Royal Aeronautical Society.The increasing use of unmanned aerial vehicles in areas such as rescue, mapping, and transportation have made it necessary to study more accurate techniques for calculating flight time estimates. Such calculations require knowing the battery discharge profile. Simplified flight time calculation methods provide data with uncertainties as they are based solely on manufacturer datasheet information. This study presents a setup to measure the battery discharge curve using a LabVIEW interface with a low-cost acquisition system. The acquired data passes through a nonlinear optimisation algorithm to find the battery coefficients, which enables the more precise estimation of its range and endurance. The great advantage of this model is that it makes it possible to predict how the battery will discharge at different rates using just one experimental curve. The methodology was applied to three different batteries and the model was validated with different discharge rates in a controlled environment, which resulted in endurance lower than 3.0% for most conditions and voltage estimation error lower than 3.0% in operational voltage. The work also presented a methodology for estimating cruise time based on the current used during each flight stage.

© 2020 Elsevier LtdLaminar burning velocity is considered as being one of the fundamental properties of a premixed flame and reliable data are constantly required for practical applications. Although it is possible to find an extensive amount of experimental laminar burning velocity data for fuels containing one or two components, data for fuels with three or more components are scarce. The goal of this study is to help fill this gap by providing experimental laminar burning velocity data for a fuel mixture with five components (H2:CO:CO2:CH4:N2). The fuel composition utilized is proposed as surrogates of the fuel provided by a downdraft gasifier, the most common and the most efficient type of gasifier. Experimental measurements were carried out for different fuel-to-air equivalence ratios (0.88 < ϕ < 1.74) at atmospheric conditions, 954 mbar and 298 K. The method utilized was the conical-flame surface using OH PLIF images (Planar-Laser-Induced Fluorescence imaging of OH). The area method provides a good approximation of the unstretched laminar burning velocity. Experimental data were compared with the simulated results obtained from a CHEMKIN chemical kinetics software. The highest experimental laminar flame speed of a downdraft syngas air mixture was 0.3491 m s−1 and occurred when ϕ ∼1.3.

© 2019 Elsevier LtdAnhydrous ethanol can be considered as one of the main alternatives to replace fossil fuels. However, the removal of water consumes the greatest fraction of the energy necessary for its production. Thus, the use of hydrous ethanol arises from a new fuel possibility and it has been successfully tested in a device such as a spark-ignition engine. For this reason, there is a need for the determination of fundamental properties of the ethanol-water-air mixtures. There are few experimental works in this area and the majority of them have been carried out in test conditions of pressure up to 1 atm. Thus, the main goal of the present work is to bridge this data gap. For this, the laminar burning velocities and Markstein length of ethanol-water–air flames at water content up to 30% v/v over a range of equivalence ratios from 0.7 to 1.4 up to 5 MPa and 380 and 450 K were experimentally determined. The method used was a constant volume bomb method with a central ignition. The results were compared to literature data and with predictions carried out with CHEMKIN-PRO using the three different kinetic mechanisms. In general, the results of the mechanisms lead to an overprediction in relation to the experimental results, though all of them predicted the burning velocity peaks at an equivalence ratio close to 1.1, which agreed with the experiments. The experiments conducted that increased water content of water fuel mixtures have a tendency to remain stable under a stretch influence. Also, it is possible to observe a linear relationship describing the influence of the diluent on the laminar burning velocity.

© 2020 IOP Publishing Ltd.A single-image nitric-oxide molecular tagging velocimetry (NO-MTV) is reported and employed in a real air driven hypersonic shock tunnel and provided velocities of 3240 170(5.2%) and 3030 160(5.3%) m , insignificantly different from previous results of 3037 98(3.2%) obtained by an ordinary multi-image MTV technique. The proposed methodology relies on an one-dimensional analytical description of the spatial intensity profile registered by a single MTV image.

© 1965-2011 IEEE.This article is concerned with the robust flight control of multirotor aerial vehicles (MAVs) subject to bounded force and torque disturbances. The focus is on the entire class of MAVs containing an arbitrary even number (${\geq}4$) of fixed (not vectoring) rotors. To deal with this problem, first, a ubiquitous hierarchical control architecture in which the attitude control loop is nested inside the position control loop is adopted and augmented with a control allocator which makes the design of the control laws themselves independent of the rotor arrangement. Specially, the control allocation problem is formulated as a quadratic program that minimizes the thrust commands and accounts for the thrust range and rate bounds. Second, geometric attitude and position control laws are designed separately using a multi-input fast nonsingular terminal sliding mode control (FNTSMC) strategy, which guarantees singularity-free finite-time stability and robustness. The main contributions are, first, the augmentation of the hierarchical control scheme for extending its applicability to any fixed-rotor MAV and, second, a detailed geometric design and finite-time stability analysis of the position and attitude control loops using the FNTSMC theory. The system is evaluated on computational simulations as well as on a hardware-in-the-loop experiment, showing that it is effective, simple to implement and adjust, and reliable to operate in nonlinear regimes as well as under bounded disturbances.

Copyright © 2020 ASMEThe present work addresses the subsonic aerodynamic coefficients model for bluff ellipsoidal hulls at transitional and turbulent Reynolds number. The drag, lift, and moment aerodynamic coefficients model are based on computational fluid dynamics (CFD) simulations for four bluff ellipsoids with aspect ratio of 1, 2, 3, and 4, in the Reynolds number range of 1×103 to 2×106 and angle of attack range from 0 to 20 degrees. The Large Eddy Simulation (LES) turbulence model is used with the sub-grid turbulence model Wall-Adapting Local-Eddy Viscosity (WALE) to solve the fluid field. To reduce computational simulation time, at a first instant, the mesh is gradually refined until the point that it does not influence anymore in the final result (mesh independence). For each aerodynamic coefficient a nonlinear equation structure, valid for all the ellipsoids, is proposed as a parametric model with parameters estimated using the least mean square algorithm applied to the results of the computational fluid dynamics simulations. The proposed equations have a superior performance, in terms of precision and number of terms, when compared to polynomial equations fitted to the same data.

© 2020 Elsevier LtdThis present paper is devoted to the numerical and experimental investigation of the modal characteristics of composite laminates, with emphasis on damping. Complementing previous studies dedicated to conventional laminates, one considers variable-angle tow laminates, in which the fibers are deposited following curvilinear trajectories. The main objective is to characterize the influence of fiber steering on the damping levels, and evaluate the possibility of achieving increased damping. A dynamic model is derived by combining the semi-analytical Rayleigh-Ritz approach, the Classical Lamination Theory, and the Strain Energy Method. This later enables to estimate the specific damping capacity of each vibration mode. Based on this model, analytical developments are performed aiming at putting in evidence the contribution of each strain component in each layer of the laminate to the specific damping capacities. The results of numerical simulations are presented, enabling to compare the values of specific damping capacities and vibration natural frequencies obtained for variable-angle tow and conventional laminates in a variety of simulation scenarios. Some of the numerical results are validated by comparisons with experimental counterparts. The results confirm the effectiveness of design strategies intended to regulate and possibly increase the damping levels of composite laminates by exploring fiber steering.

© 2020, The Brazilian Society of Mechanical Sciences and Engineering.This article presents a novel morphing unit cell concept which relies on the combination of shape memory alloy wires for actuation and permanent magnets to enable multistability. Two distinct applications are investigated experimentally, consisting in a morphing beam metastructure made with three unit cells and a variable camber airfoil metastructure having six unit cells in the chord-wise direction. Tests are performed to assess the influence of the permanent magnets on the morphing behavior of the two referred metastructures. It is verified that the permanent magnets are able to provide new stable equilibrium configurations to the metastructure and to reduce the time necessary for morphing. Another interesting feature, which enables the reduction in energy consumption, is that, due to the magnetic interactions, the thermal activation of the SMA wires can be ceased once an equilibrium configuration is achieved. The paper describes the design premises, evaluates its limitations and devises future improvements.

© 2020 Proceedings of ISMA 2020 - International Conference on Noise and Vibration Engineering and USD 2020 - International Conference on Uncertainty in Structural Dynamics. All rights reserved.Electrodynamic loudspeakers can be used to absorb sound energy in a narrow frequency band around the loudspeaker resonance. To increase the operational bandwidth, active and passive impedance control techniques have been described in the literature. In this work, we propose a passive technique that makes use of a periodic array of small loudspeakers mounted as side branches along a straight duct. A larger loudspeaker is mounted at one end of the duct, which acts as a conventional narrow-band absorber. This system aims at absorbing the sound energy flowing inside the duct, leading to a small reflection coefficient at the entry of the periodic waveguide. We investigate the sound absorption of such a device through numerical simulations based on the transfer matrix method. The unit cell is made up of a one-dimensional acoustic waveguide with a side-branch loudspeaker. It is shown that the proposed approach might increase the absorption bandwidth, even with 1-inch loudspeakers and a number of cells as small as five in the periodic structure.

© 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Transonic flows at high Reynolds numbers can lead to high dynamic pressures and, consequently, aerostructural deflections of the aircraft. Computational Fluid Dynamics (CFD) tools have been widely integrated with Computational Solid Mechanics (CSM) solvers, based on finite element discretization, in order to improve predictions of the aerodynamic performance and aircraft structural loads. The main objective of the paper is to describe the methodology and the numerical effort to integrate an in-house CFD code with a CSM solver for static aeroelastic applications in a high fidelity approach. The cases used for process validation are the static aeroelastic results from the High Reynolds Aerostructural Dynamics project (HIRENASD) and NASA’s Common Research Model (CRM) from the 6th AIAA CFD Drag Prediction Workshop. All fluid-structure interaction (FSI) procedures have been implemented in FORTRAN and integrated via shell script. Results demonstrating converged wing surface pressures and deflections are compared to available experimental data. For the HIRENASD model, FSI aerodynamic results indicated considerable degradation in both pitching and rolling moment curves when compared with ideal rigid CFD simulations. Moreover, NASA CRM FSI simulations are performed for two different sets of modal shapes, showing wing tip deformation sensitivity.

© 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Panel flutter is a real design issue for supersonic flying aerospace vehicles caused by flexible panels subject to unsteady supersonic aerodynamics loading that can lead to critical fatigue damages and catastrophic failures. Many efforts earlier were devoted to this problem, considering the numerical evaluation of a single panel solution typically. Rather than this approach, it is proposed in this paper the nonlinear aeroelastic analysis of adjacent panels, the so-called multibay panels, within the context of variable stiffness composites laminates (VSCL). The aeroelastic model is based on coupling the first-order piston theory with the VSCL structural model developed in accordance with the Classical Lamination Theory (CLT) using the von Kármán’s assumptions to account for geometrical structural nonlinearities. Moreover, the Newmark numerical time-integration is used, aiming to improve computational efficiency. The results of numerical solutions considering four different scenarios are presented, enabling the aeroelastic performance comparison with a conventional laminate, taking into account different fiber trajectories with and without ply contiguity between panels.

© 2020 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.The numerical investigation of the stochastic aeroelastic characteristics of conventional and tow-steered composite laminates subjected to random uncertainties affecting the laminate fiber volume is addressed in the present paper. A computationally efficient stochastic model is constructed combining the semi-analytical Rayleigh-Ritz approach with the Karhunen-Loève discretization of the two-dimensional random field representing the fiber volume. In addition, polynomial chaos expansions are used as stochastic metamodels of the output random variables characterizing the onset of aeroelastic instability and the mass of the laminate. Such a metamodeling approach enables to alleviate the computational cost involved in the estimation of the statistics of the output variables of interest based on Monte Carlo simulations. In addition, the study encompasses both subsonic and supersonic flow conditions, for which two appropriate aerodynamic models are used. The numerical results provide effective uncertainty quantification in a variety of simulation scenarios, which are found to be useful for the incorporation of uncertainty quantification in the design of aircraft and spacecraft structures when uncertainties induced by the manufacturing process must be dealt with.

© 2020 Elsevier B.V.The demand for the development of more efficient, low emission, and high-performance aircraft have required new methods to obtain lighter materials, with higher temperature resistance and chemical stability. For these purposes, Environmental Barrier Coatings (EBC) are largely studied. EBC's are commonly obtained through Atmospheric Plasma Spray, where the process parameters, as well as the precursor characteristics, and its interaction with the plasma jet influence the properties of the deposited material. In this context, this work aims to deposit EBC on C/C composites through the high-velocity plasma spray (HVPS) using a new concept of hybrid SiO2 + ZrO2 precursor. For this, a solid load of 7% yttria-stabilized zirconia (7YSZ) is mixed in a Si(OH4) solution with concentrations of 10, 20, and 30 g/L. From Raman and XRD analyses, ZrSiO4 and SiC were identified, its formations occur due to the reactions of SiO2 with ZrO2 (7YSZ) and the SiO2 precursor with C/C substrate. Finally, we demonstrate the versatility of the HVPS process using a hybrid precursor, capable of producing micro/nanostructured EBC coatings.

© 2020 Universidade Federal de Sao Carlos. All rights reserved.This work reports how the solar conversion efficiency of dye-sensitized solar cells (DSSCs) depends on the crystalline structure of both the compact TiO2 blocking layer (BL) and homoepitaxially grown porous TiO2 mesoporous structure. The films were grown by simultaneous sputtering of titanium targets by DC magnetron and by high-power impulse magnetron systems (HiPIMS). The deposition conditions were managed to produce in situ dense BLs and porous TiO2 films. The only variable was the polarization of the BLs (0 to -200V). The polarization caused phase transformations from pure anatase phase through rutile-anatase mixed phases to rutile phase. The polarization results in decreasing intensity of the anatase (101) peak of the porous layers. The latter promptly decreased linearly the value of the short-current Isc and exponentially the open-circuit voltage Voc of the cells. Another inference is the surface energy of the BLs, which follows an exponential decay as a function of the film polarization. XPS study of the Ti 2p3/2 – Ti 2p1/2 doublet reveals an appearance of a shake-up satellite, whose area exponentially decreases as the polarization potential rises. This phenomenon is discussed and related with other physical aspects of the homo-epitaxially grown films with different texture. The anatase phase content and its purity predefined by the experimental conditions determine the quality of the DSSC, as well as other components such as the dye type, the electrolyte, and the electrode materials.

© 2020 by the authors. Licensee MDPI, Basel, Switzerland.Black TiO2 materials have been quite widely explored due to their large solar absorption and superior photocatalytic activity. In this paper, the blackening process of titanium dioxide (TiO2) thin film using the hollow cathode hydrogen plasma (HCHP) technique is reported. First, pristine anatase TiO2 films were grown by magnetron sputtering onto silicon and cover glass substrates and then annealed at 450◦C for 2 h. Then, the as-grown TiO2 films were treated with HCHP for 15 min. The physical, chemical and morphological properties of the films were analyzed by profilometry, X-ray diffraction (XRD), UV-Vis spectrophotometry, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques. Electrical and photocatalytic measurements were performed by four-point probe and methylene blue UV degradation assays, respectively. The results showed that the black TiO2 film is highly absorbent in the UV-visible region, has low electrical resistance and greater surface area compared to the non-treated TiO2 film. These properties of black TiO2 film, as well as its performance as a photocatalytic agent, were investigated, indicating the superior quality of this material in thin film form and the promising potential of the HCHP treatment to produce hydrogenated TiO2 in short process time.

© 2020 Elsevier Masson SASWhen the oil and gas extraction in a well is over or ended by wellbore issues, a Plugging and Abandoning (P&A) operation is required. The usual method is the well cementation. A recent process is the rock fusion method through a thermite reaction for wellbore buffering operation. This paper presents a numerical thermal study for this new process. The developed model is based on the solution of the three-dimensional heat diffusion equation by a seven points Finite Difference scheme. A multi-layer geometry, composed of dolomite, cement, carbon iron steel, and thermite, is used to simulate the oil well. The phase change problem is approached through the enthalpy function. In order to optimize the problem solution, an in-house parallel algorithm in CUDA-C language was developed to solve the problem in a Graphical Process Unity (GPU). A modify Successive Over-Relaxation (SOR-M) scheme was applied to minimizing the computational time. The thermal fields are analyzed to determine if the thermite generation heat is enough to create the plug. The study found that high-power thermite is required to make the P&A process. The study also found that a coupling between the cracks in the cement at high-temperature, liquid dolomite, and the mix of the liquid steel duct, and thermite are responsible to break the cement and create a plug to perform the P&A operation.

Copyright © 2020 ASMEThe present work addresses the subsonic aerodynamic coefficients model for bluff ellipsoidal hulls at transitional and turbulent Reynolds number. The drag, lift, and moment aerodynamic coefficients model are based on computational fluid dynamics (CFD) simulations for four bluff ellipsoids with aspect ratio of 1, 2, 3, and 4, in the Reynolds number range of 1×103 to 2×106 and angle of attack range from 0 to 20 degrees. The Large Eddy Simulation (LES) turbulence model is used with the sub-grid turbulence model Wall-Adapting Local-Eddy Viscosity (WALE) to solve the fluid field. To reduce computational simulation time, at a first instant, the mesh is gradually refined until the point that it does not influence anymore in the final result (mesh independence). For each aerodynamic coefficient a nonlinear equation structure, valid for all the ellipsoids, is proposed as a parametric model with parameters estimated using the least mean square algorithm applied to the results of the computational fluid dynamics simulations. The proposed equations have a superior performance, in terms of precision and number of terms, when compared to polynomial equations fitted to the same data.

© 2020 IEEE.Optimization of motion cueing algorithms is a relevant topic in flight simulation industry. To achieve this goal, a representative model of the motion platform is needed. With this intent, this work presents a black-box approach to identify a model for the SIVOR flight simulator. The model receives position/orientation inputs in Cartesian space and streams out accelerations/angular speeds measured on the pilots' head. A comprehensive experimental analysis is carried out using a dataset based on isolated positional and rotational inputs. A frequency domain analysis is performed to evaluate signal measurement noise and to determine the model structure. As a result, a combination of continuous time linear transfer functions were identified to represent each of the direct and cross relations mapped throughout the process.

© 2020 IEEE.The Small Size League (SSL) is a robot soccer league of the Robot World Cup (RoboCup). A recent trend in hardware design in SSL involves multiple angles kicking mechanisms. Combining a multiple angles kicker with a dribbler, which consists of a spinning bar to manipulate the ball through friction, a robot can execute angled and curved shoots and passes. However, due to the complex physical interactions involved, determining how to control the kicking and dribbling devices in order to obtain the desired ball trajectory is not simple. The ball motion may be mathematically modelled by a nonlinear ordinary differential equation (ODE). The parameters needed to perform a desired curved kick are the solution of the inverse problem of the nonlinear ODE. Since this is hard to compute in real-time, this work proposes a neural network to solve this inverse problem. The network is trained using many simulated ball trajectories. Finally, we show simulation results to validate the proposed method.

© 2020 IEEE.The aim of this work is to implement a representative dynamics model of the SIVOR flight simulator. Two experiments were conducted and used to estimate and validate the model; the first one excites one robot channel at once and the second excites more than one robot channel. Based on a previous study, we established the model structure. Three distinct approaches of black-box identification model were employed: transfer function models, space-state models and ARX models. The results obtained were similar and satisfactory for inputs until 1 Hz.

Copyright © 2020 The Authors. This is an open access article under the CC BY-NC-ND licenseThe propagation of acoustic waves in a 2D geometrical domain under mixed boundary control is here described by means of the port-Hamiltonian (pH) formalism. A finite element based method is employed to obtain a consistently discretized model. To construct a model with mixed boundary control, two different methodologies are detailed: one employs Lagrange multipliers, the other relies on a virtual domain decomposition to interconnect models with different causalities. The two approaches are assessed numerically, by comparing the Hamiltonian and the state variables norm for progressively refined meshes.

© 2020 Society of Plastics EngineersAdditively manufactured composites have been demonstrating promising results with the development of new materials of high mechanical performance, which draws attention from several fields, for example, biomedical, electronics and aeronautics. However, as such materials are based on novel technologies, it is necessary to better understand their resulting characteristics and properties. For instance, evaluating the effect of environmental conditions on their mechanical performance is important, especially when moisture-sensitive polymers such as polyamide (PA) are employed as matrix. This work aims to understand and to characterize the moisture effect on the mechanical properties of additively manufactured Nylon and continuous carbon fiber (CF)-reinforced Nylon-based thermoplastic. Tensile and compressive tests were carried out in accordance with ASTM standards for the printed samples at their maximum moisture content and for samples submitted to drying after the saturated condition. Moreover, moisture absorption and swelling behaviors were assessed and discussed. The experimental results showed that moisture significantly affects the fiber/matrix interface, as well as the adhesion between printed filaments. These changes led to a decrease in the general mechanical properties in saturated state, including those in the fiber direction. Furthermore, a permanent degradation was observed in some properties after drying. Thus, the importance of considering water content and aging effect on the characterization and engineering application of 3D printed CF/PA composite was evidenced.

© 2020, Brazilian Association of Computational Mechanics. All rights reserved.Hybrid-Trefftz finite elements have been applied to the analysis of several types of structures successfully. It is based on two different sets of approximations applied simultaneously: stresses in the domain and displacements on its boundary. This method presents very large linear systems of equations to be solved. To overcome this issue, most authors have been careful in the choice of the approximation fields in order to have highly sparse linear systems. The natural choice for the stress basis has been linearly independent, hierarchical and orthogonal polynomials which typically result in more than 90% of sparsity in 3-D finite elements. Functions derived from associated Legendre and Chebyshev orthogonal polynomials have been used with success for this purpose. In this work the non-orthogonal polynomials available in the Pascal pyramid are proposed to derive a harmonic and complete set of polynomial basis as an alternative to the above-cited functions. Numerical tests show this basis produces accurate results. No significant differences were found when comparing the sparsity of the linear system of equations for both functions.

© 2020, The Brazilian Society of Mechanical Sciences and Engineering.This paper presents a fluid–structure iteration method applied as a study case to a conventional transport aircraft with wing aspect ratio of 12. It evaluates the nonlinear structure effect on the calculation of static limit loads. The numerical tool presented herein is named E2-FSI, which stands for nonlinear high-fidelity static fluid–structure iteration, developed for high flexibility static aeroelastic evaluations. A discussion about the use and the applicability of high-fidelity static fluid–structure iteration for the calculation of static loads is presented as part of the conclusion, for both current and future conventional transport aircraft.

© 2020 Elsevier B.V.The demand for the development of more efficient, low emission, and high-performance aircraft have required new methods to obtain lighter materials, with higher temperature resistance and chemical stability. For these purposes, Environmental Barrier Coatings (EBC) are largely studied. EBC's are commonly obtained through Atmospheric Plasma Spray, where the process parameters, as well as the precursor characteristics, and its interaction with the plasma jet influence the properties of the deposited material. In this context, this work aims to deposit EBC on C/C composites through the high-velocity plasma spray (HVPS) using a new concept of hybrid SiO2 + ZrO2 precursor. For this, a solid load of 7% yttria-stabilized zirconia (7YSZ) is mixed in a Si(OH4) solution with concentrations of 10, 20, and 30 g/L. From Raman and XRD analyses, ZrSiO4 and SiC were identified, its formations occur due to the reactions of SiO2 with ZrO2 (7YSZ) and the SiO2 precursor with C/C substrate. Finally, we demonstrate the versatility of the HVPS process using a hybrid precursor, capable of producing micro/nanostructured EBC coatings.

© 2020 by the authors.This work proposes the use of a dielectric barrier discharge (DBD) reactor operating at atmospheric pressure (AP) using air and sub-atmospheric pressure (SAP) using air or argon to treat polyamide 6.6 (PA6.6) fabrics. Here, plasma dosages corresponding to 37.5 kW·min·m-2 for AP and 7.5 kW·min·m-2 for SAP in air or argon were used. The hydrophilicity aging effect property of untreated and DBD-treated PA6.6 samples was evaluated from the apparent contact angle. The surface changes in physical microstructure were studied by field emission scanning electron microscopy (FE-SEM). To prove the changes in chemical functional groups in the fibers, Fourier transform infrared spectroscopy (FTIR) was used, and the change in surface bonds was evaluated by energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). In addition, the whiteness effect was investigated by the color spectrophotometry (Datacolor) technique. The results showed that the increase in surface roughness by the SAP DBD treatment contributed to a decrease in and maintenance of the hydrophilicity of PA6.6 fabrics for longer. The SAP DBD in air treatment promoted an enhancement of the aging effect with a low plasma dosage (5-fold reduction compared with AP DBD treatment). Finally, the SAP DBD treatment using argon functionalizes the fabric surface more efficiently than DBD treatments in air.

© 2019, Springer Nature B.V.Abstract: Dielectric Barrier Discharge (DBD) can be used to produce a large volume of non-thermal plasma at atmospheric pressure. Such plasmas are sources of highly reactive species (radicals, ozone, atoms, ions and excited molecules). Due to its characteristics, the DBD plasma can be applied for the pretreatment of lignocellulosic materials, in order to extract lignin that prevents the access to remained fermentable sugars in the biomass. In this context, an alternative method for pretreatment of lignocellulosic material in an in-liquid DBD plasma reactor using non-contact electrodes, working with atmospheric air, has been proposed. After the pretreatment, the solids were washed and submitted to enzymatic hydrolysis with a commercial enzyme complex, at 10 FPU/g of pretreated biomass and 50 g/L solids concentration (dry basis), for 72 h. The release of fermentable sugars was measured, comparing the samples obtained with and without plasma treatment. The highest sugar release was achieved using the plasma-in-liquid pretreatment in a single step, with glucose and xylose yields of 51.3 and 38.5%, respectively, after enzymatic hydrolysis. Thus, an effective pretreatment was developed to be applied to biomass such as: corn cob, sugarcane bagasse, bamboo, eucalyptus, etc., in order to reduce the environmental impact and, at the same time, produce biofuels. Graphic Abstract: [Figure not available: see fulltext.]

Copyright © 2020 by ASME.In this study, a hypersonic plasma setup was constructed based on a vortex plasma heater with prenozzle gas-dynamic insertion. The prenozzle allows the improvement of the characteristics of the vacuum system according to the necessities of the experiments. The plasma setup produces a hypersonic thermal flow, which is capable to test the thermal oxidation of ultrahigh temperature ceramics (UHTC) composites, such as zirconium diboride (ZrB2). Thereby, ZrB2 samples were prepared with a variation of 10, 20, and 30% of silicon carbide (SiC) in volume, in order to investigate the oxidation mechanisms and microstructural properties of the samples tested under hypersonic thermal flow. The results of the oxidation tests showed that the samples with 10 and 30% of SiC undergo to the active oxidation and forms an unstable and fragile ZrO2 oxide. The formed ZrO2 does not withstand the drag force and the thermal flux of the hypersonic plasma jet, partially volatilizing the oxide layer, causing an accentuated loss of mass. For the oxidation tests of the sample with 20% of SiC, the gain of mass was observed due to the formation of ZrSiO4 passivation layer, which is a stable oxide and promotes mechanical resistance, and low degradation rate. These results can be associated with the variation of SiC, which demonstrates an ideal proportion of 20% of SiC in ZrB2, which influences the oxidation mechanisms and produce a protective layer.

© 2020, Akadémiai Kiadó, Budapest, Hungary.In this paper, a review of radioactive wastes treatment using thermal plasma technology is presented as a treatment method for radioactive waste management.Virtually all waste streams can be treated by the thermal plasma technologies, resulting in a conditioned product, free from organics and liquids, definitely meeting the acceptance criteria for safe storage and disposal. The application of the thermal plasma system in the nuclear area is still one of the current research topics due to the theoretical and practical complexity of the treatment. This paper discusses the performance of the thermal plasma systems, addressing the advantages and limitations of the method.

© 2020 by the authors. Licensee MDPI, Basel, Switzerland.Black TiO2 materials have been quite widely explored due to their large solar absorption and superior photocatalytic activity. In this paper, the blackening process of titanium dioxide (TiO2) thin film using the hollow cathode hydrogen plasma (HCHP) technique is reported. First, pristine anatase TiO2 films were grown by magnetron sputtering onto silicon and cover glass substrates and then annealed at 450◦C for 2 h. Then, the as-grown TiO2 films were treated with HCHP for 15 min. The physical, chemical and morphological properties of the films were analyzed by profilometry, X-ray diffraction (XRD), UV-Vis spectrophotometry, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques. Electrical and photocatalytic measurements were performed by four-point probe and methylene blue UV degradation assays, respectively. The results showed that the black TiO2 film is highly absorbent in the UV-visible region, has low electrical resistance and greater surface area compared to the non-treated TiO2 film. These properties of black TiO2 film, as well as its performance as a photocatalytic agent, were investigated, indicating the superior quality of this material in thin film form and the promising potential of the HCHP treatment to produce hydrogenated TiO2 in short process time.

© 2019Nuclear reactors, hospitals, industries and research institutes generate considerable amounts of radioactive waste every day. To dispose this waste in a safe and cost-effective manner, it must be treated by immobilising the radionuclides and, for better stocking capacity, it must be volumetrically reduced as much as possible. To this end, plasma technology, among other promising technologies for radioactive waste treatment, exposes radioactive waste to temperatures above 1400 °C, thereby substantially reducing its volume. In the planning and managing of radioactive waste, the challenges related to plasma technology are presented as a motivation factor for the possible implantation of plasma reactors in nuclear plants and research centres, thereby improving radioactive waste management. In this study, a thermal plasma treatment process was established, and a plasma reactor was used for compactable waste processing. After 30 min of thermal plasma treatment, the volume reduction factor reached 1:99. The results demonstrate the viability of using a thermal plasma process for the volumetric reduction of radioactive waste in a safe and cost-effective manner.

© 2020 Elsevier Ltd. All rights reserved.An experimental study on the degradation of organic compounds from radioactive oil sludge by the ozonation process is presented. The effects of different concentrations of ozone in the oil sludge degradation over time were investigated. The experiments were performed in a 0.125 L glass reactor with magnetic stirring and a diffuser plate at the bottom to feed the ozone. The ozone concentration varied from 13 to 53 mg L-1 and the total interaction time was 1 h. To investigate the physicochemical properties of the oil sludge (solid and liquid components) prior to and after the treatment, multiple analytical characterization methods were used: Thermal Gravimetric Analysis, X-ray diffraction, Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy, Fourier Transform Infrared spectroscopy, Spectrophotometer, and Residual Gas Analyzer. The most perceptive change is in the color of the liquid medium turned from dark brown to light yellow, especially under ozone concentrations higher than 33 mg L-1. Absorbance values decreased about 3.5 times after 30 min of treatment with [O3] =53 mg L-1. FTIR spectroscopy showed that the bands associated with the CH3 and CeH in CH2 disappeared during treatment. On the other hand, a greater presence of C]C aromatics was observed. By residual gas analysis, various organic and inorganic gases were identified during the treatment, such as CH4, H2, CO2, and H2S. Finally, the ozonation of the oil sludge proved to be effective, due to its high reaction capacity.

© 2020 Universidade Federal de Sao Carlos. All rights reserved.In this study, the hybrid corona-dielectric barrier discharge plasma treatment was employed to modify the physical, chemical and morphological characteristics of a half-knitted fabric composed of 92% polyamide 6.6 and 8% elastane (PA). These properties of the fabric were evaluated by the water contact angle, x-ray diffraction, infrared spectroscopy, scanning electron microscopy and atomic force microscopy techniques. In addition, the dyeing and washing processes were also investigated. A significant reduction of the contact angle was observed for plasma-treated PA. Infrared spectroscopy analyses indicated that C-H, N-H, and N-O groups in PA increased after plasma treatment, explaining the improved coloring strength for the plasma-treated samples when dyed with reactive and acid dyes. A better fixation of dye was also observed after the atmospheric plasma treatment. Furthermore, dyeing with a basic and acid dye caused the dyeability increases for the plasma-treated sample compared with the untreated sample.

© 2020 The Author(s). Published by IOP Publishing Ltd.The development of efficient, reliable and affordable propulsion units is one of the main objectives in the development of aerospace technology. Typically the final cost of the vehicle is deeply affected by this subsystem. In this study, a hybrid combination of the ablative chamber is presented where graphite nozzles coated with chemical vapor deposited Silicon Carbide (CVD-SiC) is submitted to the ablative environment, generated by a DC plasma torch operating at a power of 35 kW and homogeneous heat flow of 0.75 MW m-2. The ablative properties of the samples were evaluated by measuring the weight loss as a function of the exposure time, weight loss of 0.11% after 70 s of exposition due to the formation of SiO gas was observed. The microstructure characteristics of SiC coating before and after ablation tests were carried out by SEM and XRD showing that it goes to scale oxidation to forming of SiO2 (β-quartz) and SiC (β to α) phase transformation. Whereas the ablation mechanism showed to be dependent on the initial coating thickness and exposure time.

© 2020 Elsevier Ltd and Techna Group S.r.l.This work aimed to study the development and properties of Bi-doped ZnO/β-Bi2O3/Carbon xerogel composites towards visible light photocatalysis applications. The materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, dispersive energy spectroscopy, infrared spectroscopy, nitrogen adsorption isotherms, Raman spectroscopy, diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. The photocatalytic activity of the developed composites was evaluated through the photodegradation of the 4-chlorophenol molecule and by chronoamperometry tests. The results obtained show that the calcination temperature poses a major influence in the final structure of the materials developed. The calcination temperature of 600 °C resulted in the formation of the β-Bi2O3 and Bi0 phases, consequently enhancing the photocatalytic activity of the composites due to the increased charge mobility provided by the heterojunctions between zinc oxide, carbon xerogel, bismuth oxide and metallic bismuth. The composite with intermediate bismuth composition (XC/ZnO–Bi2O3 5%) displayed the best photocatalytic response among the materials tested, which was confirmed by its increased photocurrent generation capability. The photocatalytic mechanism is highly dependent in the generation of hydroxyl radicals and the composite presents good reusability properties.

© 2020 Informa UK Limited, trading as Taylor & Francis Group.Nanoparticles (NPs) have been studied for a wide variety of applications, due to the elevated surface area and outstanding properties. Several types of NPs are available nowadays, each one with particular characteristics and challenges. Bionanocomposites, especially composed by polymer matrices, are gaining attention in the biomedical field. Although, several studies have shown the potential of adding NPs into these materials, some investigation is still needed until their clinical use for in vivo application is consummated. Besides that, is essential to evaluate whether the addition of nanoparticles changes the matrix property. In this review, we summarize the latest advances concerning polymeric bionanocomposites incorporated with organic (polymeric, cellulosic, carbon-based), and inorganic (metallic, magnetics, and metal oxide) NPs.

© 2020 Elsevier LtdIt aimed to evaluate if silica infiltration might influence the hydrothermal degradation of zirconia by determining: the phases formed, hardness, microstructure, and flexural strength of a 3Y-TZP. Yttria partially stabilized zirconia discs (1.2 mm thickness x 13 mm diameter) (InCeram YZ, Vita Zanhfabrik) were produced and assigned into 6 groups, considering 2 factors: silica infiltration in 2 levels (as-sintered or infiltration) and hydrothermal aging (LTD-Low Temperature Degradation) in 3 levels (baseline, aging at 132 °C for 35 h or 140 h). All the groups were subjected to the biaxial flexural test (n = 30), and Vickers hardness (n = 42). Weibull analysis was performed to determine the Weibull moduli (m) and characteristic strenghts (σ0). The specimens were characterized by scanning electron microscopy (SEM) to evaluate microstructure and X-ray diffraction (XRD) for phases percentages determination. For as-sintered condition: there was saturation of the amount of monoclinic zirconia after 35 h of hydrothermal aging, with 66% of monoclinic zirconia formed on the surface. LTD generated a progressive reduction in hardness over time; flexural strength was increased by the 35-h treatment (baseline: 974 MPa; 35 h: 1161.5 MPa), but, the 140 °C treatment was deleterious (698.5 MPa). On the other hand, the infiltrated specimens had an increase in the amount of cubic zirconia on the surface and showed 26% (35h) and 31% (140h) of monoclinic zirconia after the hydrothermal aging ; the strength was kept unaltered after LTD–35 h (935.9 MPa) and an increase was observed after LTD–140 h (1033.6 MPa); the hardness values had no statistically significant changes during the process. Thus, one can concludes that the silica infiltration can prevent the decrease in the mechanical properties due to the LTD on partially stabilized zirconia materials.

© 2020 Elsevier Ltd and Techna Group S.r.l.This work studied the influence of two sol-gel synthesis routes in obtaining a bioactive glass-ceramic derived from the 45S5 composition: a polymeric and a colloidal route. The main difference between the routes is in the silica precursor employed. The tetraethyl orthosilicate metal alkoxide (Si(OC2H5)4 - TEOS) is used in polymeric route and the silicic acid (H4SiO4) was used in the colloidal route. The synthesized xerogels were calcined at different temperatures to eliminate undesirable compounds and to verify the crystallization behavior. Afterwards, the calcined xerogels were submitted to in vitro bioactivity assay. The samples were also characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and laser diffraction. After calcination, the glass-ceramics obtained by the colloidal route showed greater number of bioactive phases and, consequently, of NBO bonds. The larger amount of NBO bonds resulted in a higher bioactivity of the materials synthesized by the colloidal route. In addition, the long hydrolysis step of the metal alkoxides was eliminated with colloidal synthesis. This allowed a significant reduction in the total synthesis time from 13 days to 24 h. To the best of our knowledge, this seems to be the first time this colloidal route has been employed in the synthesis of bioglass 45S5.

© 2020, Springer Nature B.V.This paper evaluates the influence of synthesis route (acidic or alkaline) on the structure, morphology, and photocatalytic properties of ZnO/Carbon xerogel composites. Structurally, both classes of materials present the wurtzite phase of zinc oxide. Composites derived from acidic route displayed facile thermal degradation of the zinc oxalate precursor when compared with pure zinc oxalate. Morphology-wise, materials produced through alkaline route are composed of nodular and plate-like particles, whereas acidic route composites are heterogeneously formed by large polyhedral particles and small particle agglomerates. Elemental distribution analysis confirms the heterogeneity of the acidic route composites, showing clear phase separation between the ZnO and the carbon xerogel. The composites prepared using the alkaline route are superior in the photodegradation of 4-chlorophenol, probably due to higher homogeneity and synergy between the semiconductor and carbonaceous phases. The superiority of alkaline route composites is confirmed by electrochemical impedance spectroscopy, which shows that such materials have enhanced charge separation capability. [Figure not available: see fulltext.]

© 2020, Society for Experimental Mechanics.The multireflection grazing incidence X-ray diffraction method (MGIXD) was used to analyze the surface residual stresses in 7050 Al alloy samples. This technique can provide a non-destructive stress profile in function of sample depth, avoiding the relaxation effects intrinsic to destructive methods. The state of residual stress in aeronautical aluminium samples was modulated by milling and shot peening processes. After structural characterization, the residual stress states of the samples were analyzed by multireflection and conventional stress measurement methods. The milled samples presented tensile surface residual stress relaxation attributed to thermal effects and the shot peened samples showed strong compressive stress at sub-surface, which intensity was reduced near the surface. The residual stress profiles of the Al samples were obtained by MGIXD method that evidenced properties commonly undetected in conventional residual stress studies.

© 2019 Elsevier Ltd and Techna Group S.r.l.The phase of crystalline α-wollastonite (α-CaSiO3) powders was prepared at low temperature via sol gel method. The formation mechanisms of α-wollastonite (α-CaSiO3) using different calcium salts were examined. The synthesis was carried out in absence of organic solvents, using as starting materials silicic acid and inorganic salts (CaCl2.H2O and Ca(NO3)2.4H2O). The samples were analyzed by Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetry/Differential Scanning Calorimetry (TGA-DSC), X-Ray Diffraction (XRD) and Field Emission Gun-Scanning Electron Microscopy (FEG-SEM). The experimental results demonstrate that the calcium source strongly influences the characteristics of the resultant powders, as phase purity and morphology of the wollastonite particles. XRD analysis showed that, using CaCl2.H2O on the synthesis, α-wollastonite started to crystallize as majority phase at 700 °C. The complete crystallization of α-wollastonite was observed after the calcination at 1000 °C for 5 h, while samples prepared with Ca(NO3)2.4H2O, only crystallized α-wollastonite at 1200 °C. This difference in crystallization temperature is probably related to the higher homogeneity and the elevated number of Si–O–Ca bonds present in samples prepared with CaCl2.H2O.

© 2019 Elsevier LtdThis study aimed to evaluate the effects of low temperature degradation (LTD) on commercial dental zirconias (conventional and high-translucent - HT) with different microstructures, as well as on their mechanical properties and t-m phase transformation. The amount of monoclinic zirconia in different depths was quantified using X-ray diffraction (XRD) with different anode tubes (Cr, Co and Cu). XRD was also used to measure the residual stress of the materials at 0 h, 26 h and 140 h aging times. Vickers microhardness and biaxial flexural strength tests were performed. Data were subjected to two-way ANOVA and Tukey's post-hoc test, both with α = 0.05 for means comparisons. Weibull parameters were calculated and compared based on the overlapping of confidence intervals (CI = 95%). HT Zirconia presented smaller grain sizes and had a higher rate of t-m transformation over time. The microstructure of the conventional zirconia showed an expressive increase of the grain size and consequently greater morphological variation with the LTD. The non-aged samples (control) did not present any residual stress and the aged ones presented compression stress. All zirconia showed a residual stress increase with the increase of LTD time, but the conventional one showed a decrease after 140 h. HT zirconia showed no significant change in flexural strength over LTD time, but the conventional one showed a strength decrease after 140 h (681.78 ± 121.18 MPa). Vickers hardness decreased for all zirconia samples after 26 h. The mechanics of LTD is significantly altered in different zirconia microstructures. Zirconias with smaller grains are more prone to t-m phase transformation, but present lower variation of residual stress, while larger grains zirconias have a lower surface area and therefore a more pronounced increase in stress over LTD time. Stress values close to the maximum compression stress generates ejection of the zirconia grains, producing defects and causing reduction of the compression stress and consequently decrease of flexural strength.

© 2019 Elsevier B.V.The effect of synthesis medium (ethanol and water) on ZnO/Carbon xerogel photocatalysts was studied in order to increase the efficiency of the photocatalytic degradation of 4-chlorophenol and bisphenol A. The use of carbon xerogel is justified due to its excellent electrical conductivity, high surface area and porosity. The effect of the carbon content in the composites was also evaluated. The composites were characterized using scanning electron microscopy, transmission electron microscopy, dispersive energy spectrometry, X-ray diffractometry, infrared spectroscopy, nitrogen isotherms, differential scanning calorimetry, thermogravimetry, electrochemical impedance spectroscopy and Raman spectroscopy. All materials present the hexagonal crystalline structure of zinc oxide. Materials without carbon in their composition also presented the zinc hydroxychloride monohydrate phase. X-ray diffractograms and bandgap values obtained confirm the incorporation of carbon in the crystalline structure of zinc oxide. Materials produced in ethanol medium have lower values of crystallite and particle size, as well as higher graphite contents in their composition and higher specific surface area. All materials displayed photocatalytic activity when subjected to visible and solar radiation. Materials produced in ethanol displayed superior performance when compared to those synthesized in aqueous medium. The maximum values found for the degradation of 4-chlorophenol and bisphenol A were 88% and 78%, respectively, after 5 h. The mechanism of photocatalysis is strongly influenced by the generation of hydroxyl radicals and the materials were stable for three cycles of reuse. The electrochemical impedance spectroscopy confirms that the charge separation efficiency was optimized in the presence of the carbon xerogel and when the composite was produced in ethanol medium.

© 2020 by the authors. Licensee MDPI, Basel, Switzerland.Carbon nanotubes (CNT)-reinforced polymeric composites are being studied as promising materials due to their enhanced properties. However, understanding the behavior of polymers during non-isothermal crystallization is important once the degree of crystallinity and crystallization processes are affected when nanoparticles are added to matrices. Usually, crystallization kinetics studies are performed using a model-fitting method, though the isoconversional method allows to obtain the kinetics parameter without assuming a crystallization model. Therefore, in this work, CNTs were oxidized (CNT-Ox) and functionalized with gamma-aminobutyric acid (GABA) (CNT-GB) and incorporated into a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) matrix. The influence of the addition and functionalization of CNT in the crystallization kinetics of PHBV was evaluated using the isoconversional method with differential scanning calorimetry (DSC), and by polarized light optical microscopy (PLOM) and Shore D hardness. The incorporation and functionalization of CNT into PHBV matrix did not change the Šesták and Berggren crystallization model; however, the lowest activation energy was obtained for the composite produced with CNT-GB, suggesting a better dispersion into the PHBV matrix. PLOM and Shore D hardness confirmed the results obtained in the kinetics study, showing the smallest crystallite size for CNT-containing nanocomposites and the highest hardness value for the composite produced with CNT-GB.

© 2020 Elsevier LtdNuclear power conversion in space has been approached by various means since the first space missions, with the advent of concepts such as thermoelectric, thermionic and thermodynamic conversion. Nowadays, thermal cycles are under greater focus for being capable of providing higher conversion efficiencies. In this context, one of the main concerns of engineers is the trade-off between power and mass. Therefore, this work aims the optimization of a recuperator used in a regenerative closed Brayton cycle applied for power conversion in the project of a small-scale nuclear reactor. The recuperator consists of a cross-flow, shell-and-tube heat exchanger with a matrix of tubes distributed in a staggered configuration. In this work, the number of tubes and the mass flow rate are varied. The number of tubes distributed axially is fixed as 4, whereas the quantity around the axis can be 5, 7, 9, 12 and 16 tubes. The working fluid considered in this study is a mixture of noble gases He-Xe with a molecular weight of 40 g/mol, whereas Inconel alloy 617 is applied as the recuperator material. The optimization procedure was based on the entropy generation minimization and the heat exchanger effectiveness, using the Computational Fluid Dynamics (CFD) technique to obtain the flow field. Optimum mass flow rates are obtained for all the geometries at the points of minimum entropy generation number, around which lie the ranges of tested mass flow rates. The ratio between the entropy generation number and effectiveness associated with the optimum mass flow rate is considered a performance evaluation criterion, and the dependence of this parameter with exchanger mass is assessed in order to select the most suitable geometry for the studied application. This analysis leads to the optimum design point at the geometry of 9 tubes around the recuperator axis, yielding a lost available work of 929.76 W for an ambient temperature of 298 K.

© 2020, The Brazilian Society of Mechanical Sciences and Engineering.Air-breathing hypersonic vehicles can be powered by scramjet (supersonic combustion ramjet) engines, whose inlet requires blunt leading edges in order to overcome the high heat fluxes that are inherent of hypersonic flights. Thus, this work has the purpose of evaluating, through detailed two-dimensional computational fluid dynamics analysis, the influence of the leading-edge bluntness and isolator height on the airflow of a scramjet intake. Three radii have been analyzed for the forebody and cowl leading edges: sharp, 0.5 and 1.0 mm. Moreover, two different isolator heights were varied: 15 and 20 mm. Fixed temperatures of 300 K and 1300 K were considered along the hypersonic vehicle wall. The static temperature, pressure, and Mach number contour are part of the analysis, as well as the Stanton number and the adiabatic kinetic efficiency of the scramjet. It was evidenced that both leading-edge bluntness and isolator height performed great influence on the intake airflow structure. Results showed that the isolator height had a major effect on the flow separation at the isolator entrance yielding a recirculation zone that increases with the isolator height. Furthermore, higher Stanton numbers and temperature along the isolator were found for the shorter isolator height due to stronger shock waves and higher frequency of shock-wave train. The leading-edge bluntness, in this analysis, was taken as a parameter to reduce the heat flux at the stagnation point of leading edges. However, a decrease in the adiabatic kinetic efficiency was observed when the leading-edge radius is increased. Moreover, blunt leading edges promoted a decrease in Stanton number along the scramjet intake walls and also a decrease in average temperatures throughout the isolator.

© 2020 Elsevier LtdRegarding space exploration, an adequate design of an energy conversion system for power generation is essential and plays an important role in the mission feasibility, having low total mass and size as key features that differ space power plants from grounded power stations. The waste heat system of space power plants consists of heat pipes attached to a radiator panel and, as they are responsible for the highest size proportion of the total energy conversion system, special attention must be directed to these components during the design phase. Considering these aspects, this short communication aims the optimization of the cold-side temperature of a recuperated closed Brayton cycle for space power production. For this purpose, an endoreversible thermodynamic modeling is proposed, based on overall thermal conductances of heat exchangers and heat pipes, whereas a set of algebraic equations characterized the compressor and turbine performance. The ratio of the cycle power output per radiator area was considered as the objective function which is maximized. For a fixed heat input of 157 kW and heat source and sink temperatures of 1150 K and 200 K respectively, it was evidenced an optimum operating temperature ranging from 450 to 500 K for the cold heat pipe. Based on this range of operation, heat pipes made of titanium-water with rectangular grooves as the wick structure were chosen as reference for design modeling and assembly of the heat rejection system.

© ECOS 2020.All right reserved.Focusing on the great challenges of space exploration for the coming decades, there is a need for more efficient and compact energy conversion systems for space applications. To this end, a thermodynamic model was applied to analyze the energy and exergy efficiency of space nuclear power plant that operates with freepiston Stirling cycle for deep space exploration purposes. The model considered conduction losses (thermal bridge), heat pipe efficiency, finite regeneration time, and radiation losses. Thermodynamic irreversibilities of the reactor, regenerator, and radiator were computed in order to find which component is accountable for the highest exergy destruction. Results have shown that most of the exergy is destroyed in the regenerator and the radiator. With the increasing radiator area, the irreversibility of the radiator tends to decrease, but the mass per power output ratio also decreases. The optimum power output per radiator area and mass per radiator area pointed for 2.697m2of the radiator area for this energy conversion system. Furthermore, it was evidenced that the regenerator effectiveness considerably influences the overall cycle efficiency, as well as reference temperature (environment) and cold source temperature. These results can provide relevant guidelines for future design of a space power plant where the Stirling cycle is the chosen dynamic energy conversion system.

© ECOS 2020.All right reserved.Focusing on the great challenges of space exploration for the coming decades, there is a need for more efficient and compact energy conversion systems for space applications. To this end, a thermodynamic model was applied to analyze the energy and exergy efficiency of space nuclear power plant that operates with freepiston Stirling cycle for deep space exploration purposes. The model considered conduction losses (thermal bridge), heat pipe efficiency, finite regeneration time, and radiation losses. Thermodynamic irreversibilities of the reactor, regenerator, and radiator were computed in order to find which component is accountable for the highest exergy destruction. Results have shown that most of the exergy is destroyed in the regenerator and the radiator. With the increasing radiator area, the irreversibility of the radiator tends to decrease, but the mass per power output ratio also decreases. The optimum power output per radiator area and mass per radiator area pointed for 2.697m2of the radiator area for this energy conversion system. Furthermore, it was evidenced that the regenerator effectiveness considerably influences the overall cycle efficiency, as well as reference temperature (environment) and cold source temperature. These results can provide relevant guidelines for future design of a space power plant where the Stirling cycle is the chosen dynamic energy conversion system.

© 2020 Inderscience Enterprises Ltd.In the present work, the rate of living theory and exergy analysis are gathered to assess the effects of cancer on life expectancy. An exergy model of a cancer cell metabolism is proposed taking into account the changes in the metabolic paths. Results indicate a threefold increase in the rate of exergy metabolism of a cancer cell. Moreover, per mole of glucose, a cancer cell obtains 8.9 moles of ATP against 32 synthesised by a healthy one. However, because of the increase in the rate of glucose uptake, the metabolic routes of the tumour are less efficient but are faster. The analysis of a generic tumour progression indicates that, in the absence of treatment, survival time would be around three years. Furthermore, in case of complete removal of the tumour, every six months living with the disease would lead to a reduction of almost four years in life expectancy.

© 2020The present article aims to implement and investigate a different preconditioning method based in a three-dimensional in-house compressible CFD code that ensures the robustness and numerical stability to determine the flowfield considering low Mach number flow. The present preconditioning method involve two different methodologies developed by references [8, 32]. The CFD solver was developed to calculate the Euler and Navier-Stokes equations, numerically, for steady-state regime based on the cell-centered finite volume method (FVM) using Reynolds Averaged Navier-Stokes equations (RANS). The centered second-order scheme was used for the discretization of convective terms from momentum equations. The explicit second-order five-step Runge-Kutta scheme was employed for the time-marching procedure, using an implicit residual smoothing technique to enhance the numerical stability. A local preconditioning method was implemented due to its robustness in predicting low Mach number flows in a compressible CFD code environment. However, for low Mach number flows, near stagnation points, numerical perturbations were amplified generating a stiffness in the convergence rate, which provided an inaccurate solution and numerical stability degradation. Aiming to improve the preconditioning robustness, a flux function and a new limiter were applied to operate with the preconditioning technique based on a pressure sensor. Those corrections re-scale the eigenvectors and ensure the locality of the algorithm, which improves the numerical stability and guarantees the convergence for low-speed flows. The inviscid flow over a NACA 0012 airfoil for compressible and incompressible cases shown accurate and robust solutions. For a viscous flow over a flat plate case in the compressible and incompressible cases, the preconditioning technique purposed in this work supplied good numerical solution in agreement with the analytical solution.

© 2020 Elsevier LtdGrowing environmental concerns are driving the energy market toward the development of thermodynamic cycles to harness renewable energy and waste heat. This manuscript introduces the novel organic Rankine flash cycle, which combines the organic Rankine cycle with the trilateral cycle, merging their advantages in terms of high specific power output and low heat transfer irreversibility, respectively. By comparing the organic Rankine flash cycle to the organic flash cycle, it was found that the proposed architecture reaches a peak exergy efficiency at a more realistic value of two-phase expansion volume flow ratio, consistently achieves higher energy and exergy efficiencies, presents a lower cost, and is not constrained to operate close to the working fluid saturation temperature, promising easier operability. Considering pentane as working fluid, the exergy efficiency of the organic Rankine flash cycle is 18%p higher for a heat source temperature of 150 °C, 12%p for 175 °C, and 4%p for 200 °C. The attractive thermoeconomic performance of the proposed organic Rankine flash cycle highlights the potential of such a cycle as a new paradigm in the ORC panorama, encouraging further investigation towards practical demonstration.

© Royal Aeronautical Society 2019.This paper presents a review of the various aeronautical air conditioning systems that are currently available and discusses possible system configurations in the context of the aeronautical environmental control systems. Descriptions of the standard vapor compression cycle and air cycles are provided. The latter includes, simple-cycle, bootstrap-cycle, simple-bootstrap cycle (3-wheel) and condensing cycle (4-wheel). Water separation and air recirculation systems are also explored. A comparison between vapor compression cycles and air cycles is provided, as well as a comparison between different air cycles. Air cycle units are far less efficient than vapor compression cycle units, but they are lighter and more reliable for an equivalent cooling capacity. Details regarding the aircraft conceptual design phase along with general criteria for the selection of an air conditioning system are provided. Additionally, industry trends and technological advances are examined. Conclusions are compiled to guide the systems engineer in the search for the most appropriate design for a particular application.

© 2019 Elsevier LtdIn an increasingly decentralized energy market, micro gas turbines are seen with great potential due to their low emissions and fuel flexibility, which aligns with growing environmental concerns. Although presenting a relatively low efficiency, these machines could be improved by coupling it with an organic Rankine cycle. This manuscript covers the thermoeconomic design and optimization of such bottoming cycle for a 100 kWe micro gas turbine. The tool employed for such calculations is extensively described and was developed using solely open resources. The results shown that the saturation temperature at ambient pressure was an important variable when the minimum pressure is constrained above ambient and that a high degree of superheating was favored when the recuperated cycle is heated directly by the microturbine flue gases. Pentane was flagged as the best working fluid, generating 14.1 kWe of additional power and increasing the overall electric efficiency from 30 to 34.2%. The Authors show that at the current state of the art an efficiency of around 35% is the upper practical limit for such microturbine organic Rankine cycle combination.

Copyright © 2020 ASMEThis work presents the implementation of an interactive learning platform for turbine design in an engineering teaching environment. Due to the abundance of strategies and problems encountered in a multidisciplinary iterative design process, presenting the student to the multitude of scenarios can be a laborious and time-consuming task, often not possible in one-semester courses for undergraduate students. The developed computational program breaks down the preliminary design methodology into a step-by-step analysis of a single-stage axial turbine for aeronautical application. In it, the student is guided through velocity diagram construction, performance prediction, tridimensional and compressible effects considerations, blade designing as well as accounting for losses. In this interactive learning tool, it is possible to explore the sensitivity and effects of each design choice at various design steps, generating insight and hopefully a more intimate understanding. This exploration generates real-time changes in the output interface, for example the velocity diagrams and major geometrical features, in which the student is able through different trials to observe and compare the impact of different approaches, choices and assumptions. The program is written in Python language and the loss models chosen were Kacker and Okapuu; Dunham and Came; and Ainley and Mathieson. As the same set of design requirements can lead to different - yet optimal - configurations, the student will be given guidelines based on established design methodologies with the aid of graphs and the usual ranges of the calculated parameters found in practice. At the end of this process, the student is able to harvest a final design from which it is possible to generate discussions among a class or examine the suitability of a final product in regards to a proposed assignment, objective or application.

Copyright © 2020 ASMEFilm cooling is an important technique to ensure safe operation and performance fulfillment of turbines. Its ultimate goal is to protect the axial turbine blades from high gas temperatures. An appropriate study is necessary in order to obtain a reliable representation of the flow characteristics involved in such phenomena. Because of the high computational cost of high-fidelity simulations, the low-fidelity simulation method Reynolds Averaged Navier Stokes (RANS) is commonly used in practical configurations. However, the majority of the current turbulent heat flux models fail to accurately predict heat transfer in film cooling flows. Recent work suggests the use of machine learning models to improve turbulent closure in these flows. In the present work, a machine learning model for spatially varying turbulent Prandtl number previously described in the literature is applied to a transverse film cooling flow consisting of a jet square channel. The results obtained in the present work were compared to adiabatic effectiveness experimental data available in the literature to assess the performance of the machine learning model. The results shown that for low blowing ratios (BR =0.2 and BR = 0.4) the proposed machine learning model has poor performance. However, for the case with the highest blowing ratio (BR = 0.8), the proposed model presented better results. These results are then explained in terms of the resulting turbulent Prandtl number field and suggest that the training set is not appropriate for capturing the turbulent heat flux in fully attached jets in crossflow.

Copyright © 2020 ASMEThe aim of this work is the evaluation of different mesh types applied in turbomachines area, in this case in an axial turbine stage used in turbopumps (TP) applications. The tip clearance region was considered in this study because it has high influence in turbomachines performance. Due to the complexity of the tip clearance region, structured mesh generation is not always feasible, therefore it is necessary to generate unstructured meshes that allow flow calculation through Computational Fluid Dynamics (CFD) techniques. The use of different mesh type is an interesting topic when different rotor tip geometries are evaluated, in which the desensitization methods are applied. In this work, only the common flat-tip was consider. Thus, as a first step, unstructured tetrahedral meshes (with prismatic layers close to the surfaces) with different y+ values were generated. After this, turbulent 3-D flow calculations were performed at design and off design conditions, based con Reynolds Averaged Navier-Stokes (RANS) equations. The methodology used is to present in a didactic way, for under and graduate students, the advantages and disadvantages of the unstructured mesh in relation to the structured one, already used in previous research. Unstructured meshes were generated using ICEM software (ANSYS), while structured ones were generated using AxCent software developed by CONCEPTS NREC. The machine under study is the first stage of the hydraulic axial turbine used in the Low Pressure Oxidizer Turbopump (LPOTP) of the Space Shuttle Main Engine (SSME), considering 3.0% tip clearance configuration relative to blade height. All simulations were done using CFX program (ANSYS). The result shows the comparison between the two mesh types considering the difficulty and time generation, discretization quality, effect of y+ parameter variation on flowfield, simulation time, and stage performance parameters calculation for different operating points.

© 2020 ASMENumerical simulations were carried out with the purpose of investigating the effect of applying circumferential grooves at axial compressor casing passive wall treatment to enhance the stall margin and change the tip leakage flow. The tip leakage flow is pointed out as one of the main contributors to stall inception in axial compressors. Hence, it is of major importance to treat appropriately the flow in this region. Circumferential grooves have shown a good performance in enhancing the stall margin in previous researches by changing the flow path in the tip clearance region. In this work, a passive wall treatment with four circumferential grooves was applied in the transonic axial compressor NASA Rotor 37. Its effect on the axial compressor performance and the flow in the tip clearance region was analyzed and set against the results attained for the smooth wall case. A 2.63% increase in the operational range of the axial compressor running at 100%N, was achieved, when compared with the original smooth wall casing configuration. The grooves installed at compressor casing, causes an increase in the flow entropy generation due to the high viscous effects in this gap region, between the rotor tip surface and casing with grooves. These viscous effects cause a drop in the turbomachine efficiency. For the grooves configurations used in this work, an efficiency drop of 0.7% was observed, compared with the original smooth wall. All the simulations were performed based on 3D turbulent flow calculations using Reynolds Averaged Navier-Stokes equations, and the flow eddy viscosity was determined using the two-equation SST turbulence model. The details of the grooves geometrical dimensions and its implementation are described in the paper.

© 2019 Wiley Periodicals, Inc.In vitro and in vivo experiments were undertaken to evaluate the solubility, apatite-forming ability, cytocompatibility, osteostimulation, and osteoinduction for a series of Nb-containing bioactive glass (BGNb) derived from composition of 45S5 Bioglass. Inductively coupled plasma optical emission spectrometry (ICP-OES) revealed that the rate at which Na, Ca, Si, P, and Nb species are leached from the glass decrease with the increasing concentration of the niobium oxide. The formation of apatite as a function of time in simulated body fluid was monitored by 31P Magic Angle Spinning (MAS) Nuclear magnetic resonance spectroscopy. Results showed that the bioactive glasses: Bioglass 45S5 (BG45S5) and 1 mol%-Nb-containing-bioactive glass (BGSN1) were able to grow apatite layer on their surfaces within 3 h, while glasses with higher concentrations of Nb2O5 (2.5 and 5 mol%) took at least 12 h. Nb-substituted glasses were shown to be compatible with bone marrow-derived mesenchymal stem cells (BMMSCs). Moreover, the bioactive glass with 1 mol% Nb2O5 significantly enhanced cell proliferation after 4 days of treatment. Concentrations of 1 and 2.5 mol% Nb2O5 stimulated osteogenic differentiation of BMMSCs after 21 days of treatment. For the in vivo experiments, trial glass rods were implanted into circular defects in rat tibia in order to evaluate their osteoconductivity and osteostimulation. Two morphometric parameters were analyzed: (a) thickness of new-formed bone layer and (b) area of new-formed subperiostal bone. Results showed that BGNb bioactive glass is osteoconductive and osteostimulative. Therefore, these results indicate that Nb-substituted glass is suitable for biomedical applications.

© 2019 Wiley Periodicals, Inc.Here, we investigated the biocompatibility of a bioactive sodium calcium silicate glass containing 2.6 mol% Nb2O5 (denoted BGPN2.6) and compare the results with the archetypal 45S5 bioglass. The glass bioactivity was tested using a range of in vitro and in vivo experiments to assess its suitability for bone regeneration applications. in vitro studies consisted of assessing the cytocompatibility of the BGPN2.6 glass with bone-marrow-derived mesenchymal stem cells (BM-MSCs). Systemic biocompatibility was verified by means of the quantification of biochemical markers and histopathology of liver, kidneys, and muscles. The glass genotoxicity was assessed using the micronucleus test. The regeneration of a calvarial defect was assessed using both qualitative and quantitative analysis of three-dimensional microcomputed tomography images. The BGPN2.6 glass was not cytotoxic to BM-MSCs. It is systemically biocompatible causing no signs of damage to high metabolic and excretory organs such as the liver and kidneys. No mutagenic potential was observed in the micronucleus test. MicroCT images showed that BGPN2.6 was able to nearly fully regenerate a critical-sized calvarial defect and was far superior to standard 45S5 Bioglass. Defects filled with BGPN2.6 glass showed over 90% coverage compare to just 66% for 45S5 Bioglass. For one animal the defect was completely filled in 8 weeks. These results clearly show that Nb-containing bioactive glasses are a safe and effective biomaterial for bone replacement.

© 2020, © 2020 Taylor & Francis.The present study investigates the evolution of the residual stresses in TWIP steels induced by manufacturing chain for the production of automotive body-in-white. Two different manufacturing routes were considered. The first route encompassed a plastic deformation prior to the welding stage, whereas the second involved the spot welding followed by a baking treatment. A convergent approach was adopted to isolate the effects of the first and final manufacturing steps. The findings showed that the plastic deformation prior to the welding stage is not annihilated by the welding thermomechanical cycle. Abrupt hardness gradients along small material fractions are observed. The residual stresses state changes, although its profile is still defined by the welding stage. The post-weld bake treatment showed to promote slight residual stresses relaxation, but it is not effective in inducing the same post-weld residual stresses state for different RSW parameters set.

© 2019 by the authors. Licensee MDPI, Basel, Switzerland.The microstructural characterization and corrosion resistance behavior of Fe-Mn-Si-Cr-Ni alloy with shape memory effect was studied under different mechanical processing conditions and heat treatments, which were produced using conventional casting and routing methods to reduce costs and make production viable. Microstructural characterization was performed with electron microscopy and x-ray diffraction techniques, electrochemical tests with polarization, and thermogravimetry techniques. The cast condition presented a dendritic structure and the presence of the secondary phases: ferrite-δ and Chi-X phase. The heat treatment eliminated phases, reincorporated elements in the matrix, and increased the austenitic grain. After the hot rolling process, the alloy exhibited a refined microstructure with recrystallized austenitic grains. The heat-treated condition presented better oxidation resistance than the other conditions, while the hot-rolled condition showed repassivation of the pits, raising them to higher levels. All conditions presented low corrosion resistance in environments containing chloride ions.

© 2020 by the authors.The design and evaluation of structures subjected to blast loads has increased steadily since the 11 September 2001 terrorist attacks. While shock tube testing has filled some of the data gap by replicating blast waves in a controlled fashion, there is only scant field explosion data that is easily accessible for the structural engineering community for hypothesis testing or model validation. This paper summarizes experimental design, pre-test sensor verification, and data collection from 10 reinforced concrete slabs subjected to field explosions using a modest budget. The experimental record contains pressure, displacement, and acceleration measurements of each slab except in a few cases where the sensors have failed. The data is archived at George Mason Dataverse. Following detailed description of the experimental record for each slab, an example is provided in which the data can be utilized for finite element model verification.

© 2020 IOP Publishing Ltd. All rights reserved.Predicting explosion parameters is an important step when planning for blast tests or the design of blast resistant buildings and of explosive materials and formulations. This paper presents reactive molecular dynamics simulations of furazanotetrazinedioxide (FTDO) explosive, a new and highly energetic material, calculated with the software LAMMPS with ReaxFF force field. The decomposition steps and chemical mechanism of the material decomposition was elucidated and the Arrhenius parameters of the global decomposition reaction was calculated based on a first order approach with six different isothermal simulations sets. Results present an original mechanism for the detonation/decomposition and an activation energy and frequency factor with high linear determination coefficient. These results are the first ones published for this material and present a good comparison for future experiments.

© 2020 Sociedade Brasileira de Quimica. All rights reserved.The molecular dynamics simulations were used to study the epoxy ring-opening in the determination of kinetic parameters, with a temperature range from 1500 to 2500 K in a 20 x 20 x 20 Å unit cell containing 15 molecules of C2H4O (ethylene oxide) and 35 molecules of CH6N2 (methanediamine). The activation energy values for epoxy and diamine was 66 and 92 kJ mol-1, respectively. The simulation showed epoxy ring breakage in some of the molecules, but mainly the release of ammonia by diamine. It was observed that the activation energy involved in diamine consumption for ammonia formation is higher than for the epoxy ring opening. The results of the epoxy ring-opening study show that the polymerization occurs slowly, which leads to high computational simulation values.

© 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The design of solid rocket motors is considered relatively dominated technology in the various areas of knowledge. Even so, there are variables that still need to be better explored. Therefore, the topic presented in this work is related to problems found in designs of HTPB-AP-AL based solid rocket motors that are related to the formation of Plateau in the performance curves (pressure and thrust). This phenomenon has been studied by many researchers, in the way that studies mention different causes. Among the main causes studied, research reports that this phenomenon is related to Ammonium Perchlorate and its granulometric distribution and size, the thermal decomposition kinetics of Ammonium Perchlorate, the distribution and morphology of aluminum and also to the curing agents used in the propellant formulations. The main objective of this work is to present a model built with propellant formulations, considering these variables above mentioned in order to address a good practice to avoid this phenomenon. This work presents burning rates as a function of pressure of several propellant formulations based on ammonium perchlorate (AP) and hydroxyl-terminated polybutadiene cured by isophorone diisocyanate (IPDI) and aluminum (Al), in order to evaluate values of the pressure exponent of the burning rate in distinct pressure ranges, termed as plateau burning rate trends.

© 2019, The Brazilian Society of Mechanical Sciences and Engineering.Propellants based on HTPB/AP (hydroxyl-terminated polybutadiene/ammonium perchlorate) are the most commonly used in most of the rocket engines used by the Brazilian Armed Forces. This work aimed at the possibility of extending its useful life (currently in 10 years) by performing chemical kinetic analysis of the energetic material via differential scanning calorimetry (DSC) and also performing computer simulation of aging process using the software Large-scale Atomic/Molecular Massively Parallel Simulator. The simulations presented the experimental behavior of the aging process, showing the bending and cross-link of the binder with the volume contraction and the energetic stabilization. Thermal analysis via DSC was performed in triplicate and in 3 heating ratios (5 °C, 10 °C and 15 °C) of rocket motor with 11-year shelf-life, using the Arrhenius equation to obtain its activation energy, using Ozawa and Kissinger kinetic methods, allowing comparison with manufacturing period data (standard motor). The obtained activation energies were 126.67 kJ/mol (Ozawa) and 122.85 kJ/mol (Kissinger), much higher than that of the aged propellants (~ 78 kJ/mol, based on literature data), showing that the propellant has not yet aged significantly. In addition, the kinetic parameters of internal pressure of the combustion chamber in 8 rocket engines with 11 years of shelf-life were also acquired, for comparison purposes with the engine start-up data.

© 2020, Eduem - Editora da Universidade Estadual de Maringa. All rights reserved.Predicting explosion parameters is an important step when planning for blast tests or the design of blast resistant buildings. This paper presents a comparison of recorded pressure that was reflected on the surface of reinforced concrete slabs with and without EPS (Expanded Polystyrene) foam retrofit measured from a detonation of 2.7 kg of non-confined plastic explosive. Two 50 MPa reinforced concrete slabs measuring 1.0×1.0×0.08 m, simply supported on two sides were tested. The explosive was suspended at a distance of 2.0 m from the upper surface of the slabs; one of the slabs had 5.0 cm thick foam on the top side. Eight piezoelectric pressure sensors were positioned at a distance of 2.0 m from the explosive. Results showed that the foam retrofit reduced the reflected pressure by approximately 57% when compared to the slab without EPS foam retrofit.

© 2020 Trans Tech Publications Ltd, Switzerland.In this work, the consolidation of blended elemental powders of iron, manganese and aluminum (Fe-25Mn-15Al wt.%) was performed by Equal Channel Angular Pressing (ECAP). Samples were consolidated at room temperature in a Φ = 120° die by a single pass and a second pass in route A. Both samples were heat treated at 650 °C and water cooled. Prior to heat treatment, samples presented a dense but chemically inhomogeneous structure. Fe and Al particles were highly deformed, whereas, Mn was almost undeformed. Mn particles were partially shattered by friction with Fe and Al particles. After heat treatment, the samples were characterized by SEM-EDX and presented substantial interdiffusion along the particles interfaces. It is believed that higher deformations by ECAP may improve the sinterability of consolidated samples in order to densify and chemically homogenize it.

© 2020, Springer-Verlag London Ltd., part of Springer Nature.The aerospace industry is searching to enhance product quality and performance with lower process cost and investments. One way to achieve that is to maximize automation with less operational resources and machine downtime toward to a friendly product and process assembly. Conventional jigs have rigid frame as main structure and workpieces are loaded by accurate holders, rendering it static. Within this domain, this paper identifies and compares state of art jigs used on automated cells with those of novel jig that meets the operational needs of ordinary aircraft assembly in a disruptive way. This paper details the novel jig as well as the manufacturing benefits using the jigless assembly concept in a drilling robotic working cell. The gains yielded such as infrastructure required, solution cost, performance, and product accessibility are qualitatively demonstrated herein. Additionally, the jigless assembly concept connects the manufacturing demand with the product development environment, based upon Lean manufacturing concepts.

© Published under licence by IOP Publishing Ltd.A well defined manufacturing company focuses on lean practices along the whole product development process, not exclusively during the manufacturing and production phases. This study focuses on the application steps to be adopted for productivity improvement trough lean methods assessments in a product development company for the aeronautical industry. It also aims to provide insights for decision makers along the whole lean transformation patch, and to reduce the waste generation by eliminating the non-value-added activities resulted by a bad execution of the lean implementation tools and methods. By deploying the proposed study, the assessed enterprise increased its overall lean engagement level and production outputs.

© Published under licence by IOP Publishing Ltd.Today manufacturing sectors are more competitive than before. Thus, to execute an enterprise's transformation in a company emerging as a lean organization it is crucial to have assessments and performance measurements that observe multiple variables during the lean implementation patch. The objective of this paper is to demonstrate a research method focused on lean performance measurement assessments from previous works, summarizing and organizing the existing evaluation standards in a way to allow different industrial segments to replicate the screening steps for a literature review construction. As a result, the existing lean performance measurements and methods from the last 23 years were refined in order to highlight opportunities and insights for future researches to be developed on the lean field.

© The Author(s) 2019.The problem this work aims to solve is the improvement of the leanness level of a company jeopardized by the lack of lean engagement. The objectives of the research are to present a method based on a lean self-assessment approach, consisted of a qualitative self-assessment method based on lean elements that drives an index definition associated with a roadmap. The method consists in providing a roadmap for the assessed enterprise composed by the company’s lean index, recommendations and countermeasures deriving from Delphi and Kendall Coefficient of Concordance (W) application among lean experts, leading the assessed enterprise to achieve results in terms of lean engagement, autonomy, and decision support criteria for future resource allocation. The results demonstrated that method can highlight gaps where additional improvements and investments would be necessary in the assessed enterprise. Finally, the study concludes that the lean performance identification associated to a lean roadmap in a company can be a highly effective tool to improve lean adoption in a leanness organization.

© Royal Aeronautical Society 2019.The ever-growing need to improve manufacturing processes has led recently to an increase in the number of automation solutions used to assemble aircraft structural elements. A process of interest to this industry is the alignment of fuselage sections, which is currently done either manually or by complex, expensive automated systems. The manual method introduces a significant production delay and most automated systems have limited flexibility. This article presents an integration solution implemented in an alternative low-cost, high-flexibility alignment robotic cell. The performance of an optical coordinate measuring machine (CMM) as feedback source for the adaptive control of a conventional industrial manipulator is assessed. Laser interferometry readings are used as reference. The contribution of the work lies in the execution of experiments based on the EN ISO 9283 standard (Manipulating industrial robots - performance criteria and related test methods) to determine the adequacy of the commercial off-the-shelf system to the tolerances and requirements of the fuselage alignment process at hand. The optimal configuration of the integrated system attained the nominal alignment position with an average accuracy of 0.16mm and 0.004◦, partially meeting the required tolerances, and the obtained values are nearly 16x better compared to a baseline, open-loop manipulator. These results serve as reference for the aerospace industry in the development of the next generation of tools and automated assembly processes.

© Springer Nature Switzerland AG 2019. All rights reserved.Brazil as an emerging country needs to catch up with technology to extend its position on the international market, especially in the space sector. The Technology Nationalization Framework (TNF) is a strategy for nationalization and industrialization of high technology products. The TNF is meant to assure that strategic technologies, that are currently lacking, will be designed, produced, and operated in Brazil as long as needed, without the risk of export bans or unavailability of components. The framework is based on reengineering with subsequent transfer to the national industry. The strategy starts with the identification of strategic technologies in relation to technologies already present in Brazil. For the nationalization process of these technologies a decision-making process is needed taking into account available resources and competencies. In this chapter the TNF will be introduced and explained, while also a pilot project is described in which the TNF strategy is applied.

© 2020 Elsevier LtdThis paper shows the results of traditional aerodynamic analysis and the flexible flight dynamics modeling including the effects of structural motion for a flexible wing unmanned aerial vehicle. The influence of some design parameters such as wing flexibility, horizontal/vertical tail aerodynamics is investigated for aeroelasticity and flight dynamics of flexible aircraft. The research platform is an Unmanned Aerial Vehicle (UAV), made of composite material. Its wing span is 4 m and reaches a high aspect ratio, whose value is 18.9. For a traditional analysis, the Vortex Lattice Method (VLM) was used to obtain conventional aerodynamic and control derivatives. The flexible flight dynamics model is based on the work of Waszack and Schmidt. In this approach, it is used the mean-axes reference system and it is assumed that structural deformations is small and described by a set of eigenmodes. The dynamics model incorporates the first normal modes obtained by Ground Vibration Test (GVT) campaigns. A focus of the paper lies on providing a useful model for dynamics system identification and in-flight aeroelastic testing. A developed platform for in-flight system identification and the acquisition system is described. A flight path reconstruction process from a flight test campaign results is shown.

© 2020 AIAA.With an always increasing demand for more efficient aircraft due to both economic and environmental purposes, academy and industry are studying hybrid-electric and full-electric concepts to explore new aircraft design opportunities. This paper proposes a study based on a Cessna 208B Grand Caravan, using it as a platform to implement distributed electric propulsion and enable the use of high-lift propellers by electrifying the propulsive system. Key design parameters of the aircraft are varied to evaluate the effectiveness of the lift augmentation system as well as its effects on generated thrust and aerodynamic efficiency. The effects of the propellers slipstreams on the wing are implemented on SUAVE, a conceptual level design environment, which is used to integrate the aircraft model and run the simulations. Results of the analyses differ from what is available on the literature, yielding aerodynamic efficiency gains that are much more modest than what was expected according to assumptions made on recent publications.

© 2020 Proceedings of ISMA 2020 - International Conference on Noise and Vibration Engineering and USD 2020 - International Conference on Uncertainty in Structural Dynamics. All rights reserved.A Bond Graph model for a light business aircraft and its brake system has been developed. The dynamic response of the aircraft is analyzed with two degrees of freedom considering it as a rigid body. Dual stage servo-valves, the hydraulic tubing and hoses, and brake assemblies behavior are considered on the analysis. The simulations are run using 20-Sim® software. Braking performance efficiency is assessed considering three different methods: Torque Method (AC 25-7D), Stopping Distance Efficiency and Developed μ Efficiency Methods (SAE AIR1739B). For each method, an On-Off pressure and slip control technique is implemented. The analysis of the results provides key insights for a better correlation between aircraft braking performance top level requirements and brake system specification. Therefore, this paper supports system and performance engineers on the definition of more accurate requirements on the aircraft early design phases.

© 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.With an always increasing demand for more efficient aircraft due to both economic and environmental purposes, academy and industry are studying hybrid-electric and full-electric concepts to explore new aircraft design opportunities. This paper proposes a study based on a Cessna 208B Grand Caravan, using it as a platform to implement distributed electric propulsion and enable the use of high-lift propellers by electrifying the propulsive system. Key design parameters of the aircraft are varied to evaluate the effectiveness of the lift augmentation system as well as its effects on generated thrust and aerodynamic efficiency. The effects of the propellers slipstreams on the wing are implemented on SUAVE, a conceptual level design environment, which is used to integrate the aircraft model and run the simulations. Results of the analyses differ from what is available on the literature, yielding aerodynamic efficiency gains that are much more modest than what was expected according to assumptions made on recent publications.

© 2020 Elsevier Masson SASWhen the oil and gas extraction in a well is over or ended by wellbore issues, a Plugging and Abandoning (P&A) operation is required. The usual method is the well cementation. A recent process is the rock fusion method through a thermite reaction for wellbore buffering operation. This paper presents a numerical thermal study for this new process. The developed model is based on the solution of the three-dimensional heat diffusion equation by a seven points Finite Difference scheme. A multi-layer geometry, composed of dolomite, cement, carbon iron steel, and thermite, is used to simulate the oil well. The phase change problem is approached through the enthalpy function. In order to optimize the problem solution, an in-house parallel algorithm in CUDA-C language was developed to solve the problem in a Graphical Process Unity (GPU). A modify Successive Over-Relaxation (SOR-M) scheme was applied to minimizing the computational time. The thermal fields are analyzed to determine if the thermite generation heat is enough to create the plug. The study found that high-power thermite is required to make the P&A process. The study also found that a coupling between the cracks in the cement at high-temperature, liquid dolomite, and the mix of the liquid steel duct, and thermite are responsible to break the cement and create a plug to perform the P&A operation.

© 2020 Elsevier LtdThermocline energy storage systems can be adapted to store energy in a tank where the hot fluid is pumped in during a charging cycle and cold fluid during a discharging cycle, substituting the need for two storage tanks. Here, a numerical investigation of a hot air flow transferring thermal energy to a solid porous bed is performed to evaluate the influence of the thermal conductivity and capacity ratios on the efficiency of a charging cycle of a thermocline storage tank. The numerical model considers the mixed convection turbulent flow (k-ε model) through clear and porous media using the Local Thermal Non-Equilibrium approach to provide solutions for the solid and fluid phases separately. Macroscopic equations are obtained by the method of volume averaging and numerically processed by finite volume method. The system was modelled as a vented axisymmetric cavity, partially filled with a porous medium, with hot fluid inflow from the top and outflow at the bottom. The investigation included changing Reynolds number (Ret from 8.3 × 103 to 5 × 104), thermal conductivity ratios (ks/kf from 3.5 to 1062) and thermal capacity ratio (ρscps/ρfcpf from 1483 to 7415). It was found that lower ks/kf ratios decrease the heat loss throughout the charging cycle which allow for higher temperatures in the later stages of the cycle and thus improve charging efficiency. However, this effect decreases in importance as the system undergoes higher Ret number flows. On the other hand, increasing the ρscps/ρfcpf ratio affects the entire cycle, increasing the temperature difference between phases, lowering the velocity in which the solid raises its temperature but storing heat more efficiently. Finally, a design consideration is highlighted as the importance of the ks/kf ratio on the thermal efficiency is predominant at lower Ret flows, whereas as Ret increases, ρscps/ρfcpf becomes the dominant parameter providing efficiency gains.

© 2020This work investigates the thermal behavior of the charging cycle of a thermal energy storage system for a concentrated solar power plant filled with solid porous material. A transient model that describes turbulent flow in a hybrid medium (porous/clear) with both forced and natural convection was used. The mean flow macroscopic equations are developed based on the concept of double-decomposition. Governing equations were discretized using the SIMPLE method and the system of algebraic equations was relaxed by the SIP procedure. The k-ε turbulence model was used for modeling turbulence. The two-energy equation model was used to evaluate heat transfer between the solid and fluid phases. Simulations are based on an axisymmetric tank with external convection, hot fluid inlet at the top and distributor regions at the top and bottom of the tank. Effects of Reynolds number (Ret), porosity (ϕ) and permeability (K) were investigated. Additionally, storage (ηst) and charging (ηchg) efficiencies were compared to quantify the effectiveness of the charge. Consequently, a new thermal charge efficiency (ηth) was proposed to evaluate the charging cycle. Finally, it was found that the most efficient charging parameters were the ones with higher porosity and lower permeabilities. Moreover, increasing Ret values increased the thermal charge efficiency up to a maximum and thereafter presented a stabilized trend with further increasing of Ret values.

© 2019Volumetric heat absorbers made of porous materials allow for a greater contact area between the porous matrix and the working fluid. In such devices, heat is collected in a volume rather than a surface. This work deals with transient behavior of Volumetric Heat Receivers using the thermal non equilibrium approach. Balances for energy amounts for the porous ceramic materials and air are solved numerically using the backward Euler discretization method and application of the SIMPLE method. After obtaining the algebraic equation system, relaxation by the SIP method is applied. We investigate here the effects of permeability, thermal conductivity ratio, inlet velocity and porosity on the temperature reached after thermal equilibrium. Higher inlet velocities attain quicker stabilization times and decreases equilibrium temperature, Teq. In addition, increasing porosity lower Teq and shorten time for temperature stabilization. Less permeable solid matrices, i.e. porous structures with lower Da, result in slightly higher Teq due to better enhancement of energy exchange between phases. Increasing kskf/ increases stabilization time as well as equilibrium temperatures. Thermal efficiency increases for lower inlet velocities and higher thermal conductivity ratios, whereas η is reduced for more permeable structures and higher porosities.

© 2020Aeronautic structures are exposed to a great variety of temperatures and humid environments during service. Nowadays, it is known that the combined influence of moisture and temperature induces further detrimental effects on the fatigue behavior of bonded joints when compared to the influence of each isolated condition. The effect of hygrothermal pre-conditioning on the fatigue delamination growth onset of different bonded technologies was investigated. This paper provides a material database for composite-joints tested under different environments and gives important insights on the failure mechanisms observed under cyclic loadings. This information can be latter used to validate analytical and numerical models.

© 2020 Elsevier LtdAdhesively bonded composite structures, if designed properly, have proven to be stiffer and to possess a higher specific strength than their mechanically fastened counterparts. To increase the applicability of these bonded joints in the aircraft industry, a study was performed to investigate the influence of hygrothermal aging on co-bonded composite stiffened panels with an initial disbond under cyclic compression loading. Experiments showed that hygrothermal aging led to a decrease in disbond growth throughout cyclic loading. The decreased disbond growth was likely caused by the increased ductility of the bond due to the presence of moisture. A higher ductility can lead to crack blunting and stress relaxation, resulting in higher fracture toughness of the bond. Furthermore, it was shown that hygrothermal aging did not influence the residual strength and stiffness of the panels after cyclic loading. The experiments were simulated numerically to gain a better understanding of the crack growth behavior and to aid future numerical crack growth predictions.

© 2020, The Brazilian Society of Mechanical Sciences and Engineering.A constitutive damage model is proposed in order to investigate the crushing response of 0 ∘ plies composite laminates, using a VUMAT subroutine implemented in ABAQUS/Explicit. This damage model predicts five failure mechanisms commonly observed in unidirectional carbon fibre-reinforced composite structures: fibre failure in tension, fibre failure in compression, matrix cracking in tension, matrix cracking in compression and in-plane shear failure. Its formulation is based on an energy framework which combines stress-based fracture mechanics and damage mechanics approaches within a unified way, enabling the prediction of the five failure mechanisms aforementioned in terms of damage initiation and damage propagation. In this work, a new strategy is also implemented to remove fully damage elements in order to ensure numerical stability and avoid element distortion problems. An experimental test campaign is proposed for verification of the numerical models. Preliminary results have shown a fairly good correlation between numerical predictions and experimental results for wedge-shaped tip composite laminates.

© 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Glare reinforcements have been adopted in the aeronautics industry to improve fatigue performance of structural components. Glare can be applied on early stages of the project’s design or used as temporary repairs, bonded on monolithic aluminum panels to improve crack retardation. In this work, experimental tests and verified numerical models are used to analyze the crack propagation in hybrid aeronautical structures. A Glare panel bonded to a monolithic aluminum plate with an initial crack, both with the same thickness, is tested under Mode I cyclic loading and fatigue crack propagation is measured. In order to optimize the reinforcement effect of Glare on monolithic aluminum structures, a parametric analysis is performed using verified numerical models, with different monolithic aluminum and Glare thicknesses ratio. The numerical results indicate that, for short cracks, a thinner Glare reinforcement results in a greater fatigue life. On the other hand, thicker Glare reinforcement leads to better results for long cracks. It is concluded that the damage tolerance requirements shall guide the definition of the ratio between plate and Glare thicknesses.

© Springer Nature Switzerland AG 2020.This paper presents a novel damage mechanics based failure model enabling the prediction of low cycle fatigue life and residual strength of isotropic structures under multiaxial loading. The approach herein proposed does not discretize every load cycle but instead takes an envelope loading whereby the numerical load remains constant at a maximum load level and the number of cycles is obtained from a given elapsed time defined within a pseudo-time framework. The proposed formulation is based on the smeared cracking approach accounting for damage propagation due to static and fatigue loadings, where the static component is based on the Von-Mises yield criterion and Prandtl-Reuss stress flow rule; whereas the crack propagation in cyclic loading component is based on the Paris-law. Furthermore, the formulation combines damage mechanics and fracture mechanics within a unified approach enabling the control of the energy dissipated in each loading cycle.

© 2020 Society of Plastics EngineersAdditively manufactured composites have been demonstrating promising results with the development of new materials of high mechanical performance, which draws attention from several fields, for example, biomedical, electronics and aeronautics. However, as such materials are based on novel technologies, it is necessary to better understand their resulting characteristics and properties. For instance, evaluating the effect of environmental conditions on their mechanical performance is important, especially when moisture-sensitive polymers such as polyamide (PA) are employed as matrix. This work aims to understand and to characterize the moisture effect on the mechanical properties of additively manufactured Nylon and continuous carbon fiber (CF)-reinforced Nylon-based thermoplastic. Tensile and compressive tests were carried out in accordance with ASTM standards for the printed samples at their maximum moisture content and for samples submitted to drying after the saturated condition. Moreover, moisture absorption and swelling behaviors were assessed and discussed. The experimental results showed that moisture significantly affects the fiber/matrix interface, as well as the adhesion between printed filaments. These changes led to a decrease in the general mechanical properties in saturated state, including those in the fiber direction. Furthermore, a permanent degradation was observed in some properties after drying. Thus, the importance of considering water content and aging effect on the characterization and engineering application of 3D printed CF/PA composite was evidenced.

© 2020 Elsevier B.V.This study introduces fast manufactured (4−5 hours) vertical aligned carbon nanotubes/polydimethylsiloxane (VACNT/PDMS) stretchable sensor for aircraft structures and polymer composites. The VACNT growth method from thermal CVD with camphor and ferrocene precursors create a dense and homogeneous CNT structure with many ohmic conducting paths that surpass any more resistive tunneling phenomena. The extensive AC/DC piezoresistive performance investigation shows ohmic conduction. The VACNTs/PDMS sensor presented high linearity (r2 = 0.99) under ∼20 % strain with an average gauge factor of 3.28 at DC measurements and minor resistance variations (0.052 %) attributed to the copper terminals electrodeposition. An important feature is the resistance value compatible with conventional extensometry equipment. The DC gauge factor was ∼60 % higher than the conventional metallic strain gauge allowing measurements within a wider strain range.

© 2020Aeronautic structures are exposed to a great variety of temperatures and humid environments during service. Nowadays, it is known that the combined influence of moisture and temperature induces further detrimental effects on the fatigue behavior of bonded joints when compared to the influence of each isolated condition. The effect of hygrothermal pre-conditioning on the fatigue delamination growth onset of different bonded technologies was investigated. This paper provides a material database for composite-joints tested under different environments and gives important insights on the failure mechanisms observed under cyclic loadings. This information can be latter used to validate analytical and numerical models.

© 2020 Elsevier LtdRecent aircraft are increasingly presenting unconventional wing configurations, resulting in unusual aeroelastic responses and consequently giving rise to different technological strategies to enhance aeroelastic stability. Among them, the technique of stress stiffening by piezoelectric actuation emerged as a promising technological solution to improve the aeroelastic stability of structures with both ends axially constrained. Therefore, an aeroelastic model employing smart composite beam elements and time domain aerodynamic loads with strip theory for stress stiffening aeroelastic problems was developed and carefully validated. In addition, the effect of bending-torsion coupling provided by concentrated masses on the aeroelastic response of the structure is also taken into account, which was included by the presence of a slender ballast arbitrarily positioned along the span and chord. Parametric studies were performed investigating the influence of aspect ratio, fiber orientation angle, ballast position, as well as piezoelectric unit position along the span and its input voltage. Results showed a promising performance of such technique, as it could increase the bandwidth of two flexible modes associated with the flutter mechanism.

© 2020 Elsevier LtdA cohesive zone model is proposed to analyse composite delamination propagation under high-cycle fatigue loading. A new method to compute the strain energy release rate at any point within the element fatigue life cycle range is presented. The proposed scheme is based on the J-integral method evaluated at an estimated position of the crack-tip within the element, instead of the element integration points. Furthermore, a new fatigue damage evolution law is proposed to account for the unwanted quasi-static damage during the element fatigue degradation process. The model prediction capabilities were verified against experimental data available in the literature and theoretical solutions using a double cantilever beam configuration for mode I loading, four-point end-notched flexure configuration for mode II loading, and mixed-mode bending configuration for mixed-mode loading. The simulations were performed at both constant and variable amplitude loading. The numerical predictions obtained using the proposed model correlated very well with literature's experimental data.

© 2020 Elsevier LtdAdhesively bonded composite structures, if designed properly, have proven to be stiffer and to possess a higher specific strength than their mechanically fastened counterparts. To increase the applicability of these bonded joints in the aircraft industry, a study was performed to investigate the influence of hygrothermal aging on co-bonded composite stiffened panels with an initial disbond under cyclic compression loading. Experiments showed that hygrothermal aging led to a decrease in disbond growth throughout cyclic loading. The decreased disbond growth was likely caused by the increased ductility of the bond due to the presence of moisture. A higher ductility can lead to crack blunting and stress relaxation, resulting in higher fracture toughness of the bond. Furthermore, it was shown that hygrothermal aging did not influence the residual strength and stiffness of the panels after cyclic loading. The experiments were simulated numerically to gain a better understanding of the crack growth behavior and to aid future numerical crack growth predictions.

© 2020 Elsevier LtdMode I interlaminar fracture toughness of CFRP joints co-cured and co-bonded was experimentally characterised under several environmental conditions. Two test campaigns were carried out: one with as-received specimens tested at −54 °C and 25 °C, and another with hygrothermally aged samples tested at 25 °C and 80 °C. Dynamic mechanical analysis and scanning electron microscopy were used to explain distinct results. For co-cure, the propagation onset for as-received samples started at the interlayer region between the two adherends before migrating deeper into the adherend, while for as-received co-bonded samples, propagation onset was mainly cohesive. After aging, both bonding techniques failed directly in the adherend, in a fibre-tear fashion. Thus, the aging process presented a higher influence on failure mechanisms than the testing temperature. Regarding performance, mode I fracture toughness did not present a great variation for co-cured samples, since failure locus was always in the adherend. However, the initiation mode I fracture toughness of co-bonding decreased between as-received and aged samples. This difference is attributed to the presence of the adhesive in co-bonded systems, which showed to be more affected by environmental conditions than systems formed by fibre and matrix only, such as co-cured ones.

© 2020, The Brazilian Society of Mechanical Sciences and Engineering.A constitutive damage model is proposed in order to investigate the crushing response of 0 ∘ plies composite laminates, using a VUMAT subroutine implemented in ABAQUS/Explicit. This damage model predicts five failure mechanisms commonly observed in unidirectional carbon fibre-reinforced composite structures: fibre failure in tension, fibre failure in compression, matrix cracking in tension, matrix cracking in compression and in-plane shear failure. Its formulation is based on an energy framework which combines stress-based fracture mechanics and damage mechanics approaches within a unified way, enabling the prediction of the five failure mechanisms aforementioned in terms of damage initiation and damage propagation. In this work, a new strategy is also implemented to remove fully damage elements in order to ensure numerical stability and avoid element distortion problems. An experimental test campaign is proposed for verification of the numerical models. Preliminary results have shown a fairly good correlation between numerical predictions and experimental results for wedge-shaped tip composite laminates.

© 2020 Elsevier LtdA discussion on cohesive zone model formulation for prediction of interlaminar damage in composite laminates is presented in this paper. The degradation of interlaminar mechanical properties is analysed from a physical point of view. Firstly, the damage evolution is evaluated according to the traction-separation law and it is demonstrated that if a linear elastic unloading/reloading curve is assumed, the softening function must also be linear. Secondly, issues regarding damage onset and fracture criteria in mixed-mode loading are critically addressed and commented. A new set of criteria is proposed, and the limitations of existing criteria are discussed.

© 2019 Elsevier LtdAdhesive bonding technologies exhibit several advantages over conventional mechanical fasteners which include lower weight, reduced stress concentration in the adherents and excellent fatigue properties allowing the design of smooth surface contour and damage tolerant aerostructures. The overall structural performance of the composite joint depends on several factors related to the manufacturing process, such as surface preparation procedure, adhesive type, aging effects, and deficiency of inspection procedures. For this reason, there is a clear need to understand better how the joints behavior can be affected by them and the causes of their failure in order to improve the design and performance. In this context, this work presents the application of Scanning Electron Microscopy (SEM) technique to perform the fractographic analysis in two different types of joints namely co-bonded (CB) and secondary bonding (SB) that were submitted to a interlaminar fracture toughness tests under Mode II loading at Room Temperature Ambient (RTA) and Environmental Temperature Wet (ETW) conditions. The fracture surface of each sample submitted Mode II was prepared and analyzed regarding its failure aspects, enabling their association with the mechanical behavior of the samples during the fracture toughness tests and the values obtained. A detailed study on the fracture aspects of the composite joints was carried out correlating the fracture aspects with the mechanical behavior, type of processing and environmental conditioning in which each type of joint was tested, thus validating the use of these joints for operating conditions similar to those experienced in-service concerning aeronautical applications.

© 2019 Elsevier LtdAdhesive joints exhibit several advantages over conventional joints based on mechanical fasteners such as more uniform stress distribution, enhanced fatigue performance, stiffer connection, lower weight, smooth surface countor. However, the influence of environmental effects related to temperature and moisture absorption on the mechanical performance of these types of composite joints are not yet fully understood. This work investigates the hygrothermal effects on fracture toughness of composite carbon/epoxy joints under Mixed Modes I/II loading in different mode ratios (35%, 50% and 75%). Joints were produced using co-curing (CC), co-bonding (CB) and secondary bonding (SB) technologies. The specimens were submitted to an elevated temperature wet condition (ETW) at a high moisture content (90% R.H.) and high temperature (80 °C) and compared with results obtained at a room temperature ambient (RTA). The SB samples under ETW condition exhibited higher GII/GT values when compared to CC and CB specimens tested under the same aging condition. Using the scanning electronic microscopy (SEM) technique, it was possible associate the delamination process behavior of aging specimens with the fracture toughness values. The wet and hot environment affect both adhesive and adherent what results in significant changes in the failure aspects during the delamination induced failure process.

© Springer Nature Switzerland AG 2020.This paper presents a novel damage mechanics based failure model enabling the prediction of low cycle fatigue life and residual strength of isotropic structures under multiaxial loading. The approach herein proposed does not discretize every load cycle but instead takes an envelope loading whereby the numerical load remains constant at a maximum load level and the number of cycles is obtained from a given elapsed time defined within a pseudo-time framework. The proposed formulation is based on the smeared cracking approach accounting for damage propagation due to static and fatigue loadings, where the static component is based on the Von-Mises yield criterion and Prandtl-Reuss stress flow rule; whereas the crack propagation in cyclic loading component is based on the Paris-law. Furthermore, the formulation combines damage mechanics and fracture mechanics within a unified approach enabling the control of the energy dissipated in each loading cycle.

© 2019 SAE International. All rights reserved.Recently, the advance of computational fluid dynamics simulation applied on design of internal combustion engines (ICE) has highlighted the need of reliable chemical kinetics models for most common fuels applied on ICE operation, such as ethanol, gasoline and blends. Therefore, the mainly motivation for this study is determine and evaluate the influence of the water content on ethanol flames for laminar flame speed and chemical kinetics. For this goal, laminar flame speed measurements by OH-Emission and OH-PLIF were conducted on anhydrous and hydrous ethanol premixed flames at atmospheric pressure. Distinct fuel samples were evaluated at several equivalence ratios. Chemical kinetic simulation considering Marinovs mechanism was performed in order to match velocities obtained from experimental data versus values obtained through numerical simulation, and to verify the characteristics of hydroxyl production at conditions studied. A sensitivity analysis for defined species was performed for the test conditions and the images obtained by laser techniques were correlated to simulated cases.

© 2020 Society of Plastics EngineersAdditively manufactured composites have been demonstrating promising results with the development of new materials of high mechanical performance, which draws attention from several fields, for example, biomedical, electronics and aeronautics. However, as such materials are based on novel technologies, it is necessary to better understand their resulting characteristics and properties. For instance, evaluating the effect of environmental conditions on their mechanical performance is important, especially when moisture-sensitive polymers such as polyamide (PA) are employed as matrix. This work aims to understand and to characterize the moisture effect on the mechanical properties of additively manufactured Nylon and continuous carbon fiber (CF)-reinforced Nylon-based thermoplastic. Tensile and compressive tests were carried out in accordance with ASTM standards for the printed samples at their maximum moisture content and for samples submitted to drying after the saturated condition. Moreover, moisture absorption and swelling behaviors were assessed and discussed. The experimental results showed that moisture significantly affects the fiber/matrix interface, as well as the adhesion between printed filaments. These changes led to a decrease in the general mechanical properties in saturated state, including those in the fiber direction. Furthermore, a permanent degradation was observed in some properties after drying. Thus, the importance of considering water content and aging effect on the characterization and engineering application of 3D printed CF/PA composite was evidenced.

© 2020 Elsevier LtdHomogenization techniques are very important in describing the mechanical behavior of high performance composite materials. Among the different techniques applied to this modeling, the RVE (Representative Volume Element) and AH (Asymptotic Homogenization) play an important role. In this context, the present work aims to present a complete implementation methodology for Asymptotic Homogenization using ABAQUS® software. Although recent work have provided proper methodologies to describe the mechanical behavior of composite materials based on their constituents, the authors verified that gaps still exist. In contrast, this paper presents all the required steps in details. The application of periodic boundary conditions, which is not straightforward on ABAQUS® software, is described for all the load cases to be solved. The computation of required data from software output files as well as the calculation of the homogenized matrix are also described. The expanded equations to obtain the stresses at microscopic level using finite element commercial software, which could not be seen in recent literature, are detailed and the required emphasis is given. This paper also presents examples to validate and evaluate the obtained results.

© 2020, The Author(s).The Hashin’s strength criteria are usually employed in first ply failure and damage-onset analysis of fibre-reinforced composites. This work presents optimality conditions of local material orientations for these criteria, in terms of principal stresses and material strength parameters. Each criterion (matrix tensile/compressive, fibre tensile/compressive modes) has its conditions separately derived, analytically, based on a fixed stress field assumption. The conditions found show that orientations which coincide and do not coincide with principal stress directions may minimise local failure indices. These solutions are employed in a proposed algorithm, named HA-OCM (Hashin Optimality Criteria Method), which selectively satisfies the matrix failure modes (either tensile or compressive), iteratively and finite element-wise in composites. It is demonstrated that the HA-OCM is able to design single-layer plane structures with improved failure loads in comparison with designs following only maximum (in absolute) principal stress orientations. Results show that the material orientations have a trend to end up either aligned or at 90° with maximum in absolute principal stress directions. Global optima for compliance are, however, not guaranteed. To give an idea of gains in terms of failure loads, some HA-OCM designs show improvements of 71% and 140%, for example, in comparison with principal stress design.

© 2020 by the authors.The present work expands the application of Puck and Schurmann Inter-Fiber Fracture criterion to fiber reinforced thermoplastic 3D-printed composite materials. The effect of the ratio between the transverse compressive strength and the in-plane shear strength is discussed and a new transition point between the fracture conditions under compressive loading is proposed. The recommended values of the inclination parameters, as well as their effects on the proposed method, are also discussed. Failure envelopes are presented for different 3D-printed materials and also for traditional composite materials. The failure envelopes obtained here are compared to those provided by the original Puck and Schurmann criterion and to those provided by Gu and Chen. The differences between them are analyzed with the support of geometrical techniques and also statistical tools. It is demonstrated that the Expanded Puck and Schurmann is capable of providing more suitable failure envelopes for fiber reinforced thermoplastic 3D-printed composite materials in addition to traditional semi-brittle, brittle and intrinsically brittle composite materials.

© 2020 IOP Publishing Ltd. All rights reserved.Predicting explosion parameters is an important step when planning for blast tests or the design of blast resistant buildings and of explosive materials and formulations. This paper presents reactive molecular dynamics simulations of furazanotetrazinedioxide (FTDO) explosive, a new and highly energetic material, calculated with the software LAMMPS with ReaxFF force field. The decomposition steps and chemical mechanism of the material decomposition was elucidated and the Arrhenius parameters of the global decomposition reaction was calculated based on a first order approach with six different isothermal simulations sets. Results present an original mechanism for the detonation/decomposition and an activation energy and frequency factor with high linear determination coefficient. These results are the first ones published for this material and present a good comparison for future experiments.

© 2020 Elsevier LtdLaminar burning velocity is considered as being one of the fundamental properties of a premixed flame and reliable data are constantly required for practical applications. Although it is possible to find an extensive amount of experimental laminar burning velocity data for fuels containing one or two components, data for fuels with three or more components are scarce. The goal of this study is to help fill this gap by providing experimental laminar burning velocity data for a fuel mixture with five components (H2:CO:CO2:CH4:N2). The fuel composition utilized is proposed as surrogates of the fuel provided by a downdraft gasifier, the most common and the most efficient type of gasifier. Experimental measurements were carried out for different fuel-to-air equivalence ratios (0.88 < ϕ < 1.74) at atmospheric conditions, 954 mbar and 298 K. The method utilized was the conical-flame surface using OH PLIF images (Planar-Laser-Induced Fluorescence imaging of OH). The area method provides a good approximation of the unstretched laminar burning velocity. Experimental data were compared with the simulated results obtained from a CHEMKIN chemical kinetics software. The highest experimental laminar flame speed of a downdraft syngas air mixture was 0.3491 m s−1 and occurred when ϕ ∼1.3.

© 2020 Sociedade Brasileira de Quimica. All rights reserved.The molecular dynamics simulations were used to study the epoxy ring-opening in the determination of kinetic parameters, with a temperature range from 1500 to 2500 K in a 20 x 20 x 20 Å unit cell containing 15 molecules of C2H4O (ethylene oxide) and 35 molecules of CH6N2 (methanediamine). The activation energy values for epoxy and diamine was 66 and 92 kJ mol-1, respectively. The simulation showed epoxy ring breakage in some of the molecules, but mainly the release of ammonia by diamine. It was observed that the activation energy involved in diamine consumption for ammonia formation is higher than for the epoxy ring opening. The results of the epoxy ring-opening study show that the polymerization occurs slowly, which leads to high computational simulation values.

© 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The design of solid rocket motors is considered relatively dominated technology in the various areas of knowledge. Even so, there are variables that still need to be better explored. Therefore, the topic presented in this work is related to problems found in designs of HTPB-AP-AL based solid rocket motors that are related to the formation of Plateau in the performance curves (pressure and thrust). This phenomenon has been studied by many researchers, in the way that studies mention different causes. Among the main causes studied, research reports that this phenomenon is related to Ammonium Perchlorate and its granulometric distribution and size, the thermal decomposition kinetics of Ammonium Perchlorate, the distribution and morphology of aluminum and also to the curing agents used in the propellant formulations. The main objective of this work is to present a model built with propellant formulations, considering these variables above mentioned in order to address a good practice to avoid this phenomenon. This work presents burning rates as a function of pressure of several propellant formulations based on ammonium perchlorate (AP) and hydroxyl-terminated polybutadiene cured by isophorone diisocyanate (IPDI) and aluminum (Al), in order to evaluate values of the pressure exponent of the burning rate in distinct pressure ranges, termed as plateau burning rate trends.

© 2019, The Brazilian Society of Mechanical Sciences and Engineering.Propellants based on HTPB/AP (hydroxyl-terminated polybutadiene/ammonium perchlorate) are the most commonly used in most of the rocket engines used by the Brazilian Armed Forces. This work aimed at the possibility of extending its useful life (currently in 10 years) by performing chemical kinetic analysis of the energetic material via differential scanning calorimetry (DSC) and also performing computer simulation of aging process using the software Large-scale Atomic/Molecular Massively Parallel Simulator. The simulations presented the experimental behavior of the aging process, showing the bending and cross-link of the binder with the volume contraction and the energetic stabilization. Thermal analysis via DSC was performed in triplicate and in 3 heating ratios (5 °C, 10 °C and 15 °C) of rocket motor with 11-year shelf-life, using the Arrhenius equation to obtain its activation energy, using Ozawa and Kissinger kinetic methods, allowing comparison with manufacturing period data (standard motor). The obtained activation energies were 126.67 kJ/mol (Ozawa) and 122.85 kJ/mol (Kissinger), much higher than that of the aged propellants (~ 78 kJ/mol, based on literature data), showing that the propellant has not yet aged significantly. In addition, the kinetic parameters of internal pressure of the combustion chamber in 8 rocket engines with 11 years of shelf-life were also acquired, for comparison purposes with the engine start-up data.

© 2020, Eduem - Editora da Universidade Estadual de Maringa. All rights reserved.Predicting explosion parameters is an important step when planning for blast tests or the design of blast resistant buildings. This paper presents a comparison of recorded pressure that was reflected on the surface of reinforced concrete slabs with and without EPS (Expanded Polystyrene) foam retrofit measured from a detonation of 2.7 kg of non-confined plastic explosive. Two 50 MPa reinforced concrete slabs measuring 1.0×1.0×0.08 m, simply supported on two sides were tested. The explosive was suspended at a distance of 2.0 m from the upper surface of the slabs; one of the slabs had 5.0 cm thick foam on the top side. Eight piezoelectric pressure sensors were positioned at a distance of 2.0 m from the explosive. Results showed that the foam retrofit reduced the reflected pressure by approximately 57% when compared to the slab without EPS foam retrofit.

© 2020 Elsevier LtdCurrent trends in the aircraft industry involve higher aspect-ratio wings made of lighter materials. These trends seek to reduce fuel emissions and increase flight efficiency by reducing drag to lift ratio and overall weight, respectively, of the aircraft. This results in reduced structural stiffness and coupling between the aeroelastic modes and flight dynamics. The flutter phenomenon is of particular interest for aeroelastic studies, and modeling post-flutter limit-cycle oscillations (LCO) is a challenging problem. Several studies have been developed to allow fast simulations of the highly non-linear aerodynamic situations, with leading-edge vortex modulation been a proved solution for modeling some forms of LCOs in airfoils. This article proposes a framework based on the 3D expansion of this method using strip theory and coupling with modal structural model for simulations of aerodynamic based non-linear phenomenon. A cantilevered flat plate is used for testing and validating the framework against wind-tunnel experiments and the industry standard approach. The results show that the proposed model is able to capture the main behavior of the LCO observed in the experiments and is directly comparable with the current approaches used at the industry. The framework allows for scalability and is also fast enough to provide time-based results in under two days for a desktop simulation, reducing the need of expensive cluster computations. Finally, since it is completely physics-based it allows for the engineer to get insights on the aerodynamic flow at a fraction of the cost of more detailed CFD models.

© The Institution of Engineering and Technology 2020.This chapter discusses new approaches to sense and acquire vibration data and to pre-process these data on aeroelastic certification test flights. These new approaches aim to reduce the time to identify the aeroelastic phenomenon and to reduce the size of hardware that must be boarded in the aircraft, thus minimising the risks and costs of the vibration tests. The presented experiments construct a way to develop a non -contact measurement system for flight vibration tests in the aircraft certification process. These experiments have shown that the techniques used today for in-flight trials will be obsolete in the near future, as the aeronautical structures are becoming lighter every day, thus not admitting any additional mass for instrumentation in-flight trials.

© 2020 American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Electric propulsion has become a subject of great interest in the aeronautical community. The present work focuses on the optimal climb performance of such aircraft, in the sense of minimizing the electric charge consumed. This analysis is relevant, since this flight phase is very energy consuming and demanding on the propulsion system. A cost function – the electric charge consumed – is derived in parametric form, with both aircraft and motor parameters. Analytical expressions for the optimal lift coefficient, throttle, velocity and electric charge are derived as solutions for a static optimal control problem. The solutions are also presented in parametric form, being useful for applications in conceptual design and performance analysis. This is supplemented by simulations in order to provide a quantitative insight to the problem.

© 2019 Elsevier Inc.This study considers the spatial eigensolution analysis of spectral/hp continuous Galerkin (CG) schemes, complementing a recent work by Moura et al. (2016) [15] which addressed CG's temporal analysis. While the latter assumes periodic boundary conditions, the spatial approach presumes inflow/outflow type conditions and therefore provides insights for a different class of problems. The linear advection-diffusion problem is considered for a wide range of Péclet numbers, allowing for viscous effects at different intensities. The inviscid (linear advection) case receives particular attention owing to the manifestation of peculiar characteristics previously observed for discontinuous Galerkin (DG) schemes in the limit of strong over-upwinding. These effects are discussed in detail due to their potential to negatively affect solution quality and numerical stability of under-resolved simulations at high Reynolds numbers. The spectral vanishing viscosity (SVV) technique is subsequently considered as a natural stabilization strategy, in the context of linear advection. An optimization procedure is employed to match SVV diffusion levels to those of DG at appropriate polynomial orders. The resulting CG-SVV discretisations are tested against under-resolved computations of spatially developing vortex-dominated flows and display excellent robustness at high Reynolds numbers along with superior eddy-resolving characteristics at higher polynomial orders. This highlights the importance of appropriate stabilization techniques to improve the potential of spectral/hp CG methods for high-fidelity simulations of transitional and turbulent flows, including implicit LES / under-resolved DNS approaches.

© 2020, The Author(s).Erosion wear is the loss of mass on the surface of a solid body in contact with a moving fluid. When the fluid under study has solid particulate material or sediments, the erosion could be significant (Kulu and Kleis, Solid particle erosion: occurrence, prediction and control. Springer, London, 2008; Karimi and Schmid, Wear 156(1):33–47, 1992). Several studies (Karimi and Schmid, Wear 156(1):33–47, 1992; Neopane and Cervantes, Global J Res Eng Mech Mech Eng 11:17–26, 2011; Zeng et al., Proc IMechE 231(3):182–196, 2017; Padhy and Saini, Energy 39(1):286–293, 2012; Bajracharya et al., Wear 264(3–4):177–184, 2008; Kumar and Saini, Renew Sust Energ Rev 14(1):374–383, 2010; Xiao et al., J Hydrodyn B 19(3):356–364, 2007; Zhu et al., Nucl Eng Des 273:396–411, 2014; Chongji et al., IOP Conf Ser Earth Environ Sci 22(5):052019, 2014; Finnie and Kabil, Wear 8(1):60–69, 1965; Finnie, Wear 3(2):87–103, 1960; Finnie, Wear 19(1): 81–90, 1972) have been developed to investigate this phenomenon. Nevertheless, few attention has been paid to influence of small eddies during the erosion process, limiting the accuracy of the results in the simulation. The use of spectral element methods can allow increasing accuracy in the simulation due to the potential to consider these smaller scales.To the best of the authors’ knowledge, there is no work that uses high order methods to evaluate erosion wear rate. This research aim is to assess the impact of higher resolution methods on the prediction of erosion wear rate and distribution. Nektar+ + is a framework to solve partial differential equations using spectral/hp element method (Cantwell et al., Comput Phys Commun 192:205–219, 2015). This work presents a methodology to model erosion wear in Nektar+ +, with the creation of two modules. The first one is for the particle tracking evaluation and the record of impact on the walls of interest. The second one implements the Hutchings and Finnie models (Finnie, Wear 3(2):87–103, 1960; Finnie, Wear 19(1):81–90, 1972; Padhy and Saini, Renew Sust Energ Rev 12(7):1974–1987, 2008; Dutta, Bulle-effect and its implications for morphodynamics of river diversions. Ph.D. Thesis. University of Illinois at Urbana-Champaign, 2017) to predict the material removal rate as a function of the velocity and the angle of impact of each particle, the particle diameter and density, and the hardness relationship between particles and the wall. At the end, the particles trajectories and erosion distribution on walls are obtained. To assess effectiveness of the methodology a Backward Facing Step was investigate and the erosion patterns were found.

© 2020, The Author(s).We present the first eigenanalysis of hybridisable discontinuous Galerkin (HDG) schemes for the advection-diffusion equation in one dimension. This study is also one of the first to include viscous diffusion effects in the eigenanalysis of discontinuous spectral element methods. The interplay between upwind dissipation and viscous diffusion is discussed and preliminary insights deemed relevant to (under-resolved) turbulence computation approaches are presented.

© Springer Nature Switzerland AG 2020.This study assesses the suitability of spectral/hp continuous Galerkin (CG) schemes [1] for model-free under-resolved simulations of a non-trivial turbulent boundary layer flow. We consider a model problem proposed by Spalart in [2] that features a rotating free-stream velocity and admits an asymptotic solution with significant crossflow effects. Note this test case is substantially more complex than typical turbulent boundary layer canonical problems owing to its unsteadiness and enhanced small-scale anisotropy. Reported LES-based solutions to this problem are known to require sophisticated modelling and relatively fine grids to achieve meaningful results, with traditional models exhibiting poor performance. The model-free CG-based approach advocated, on the other hand, yields surprisingly good results with considerably less degrees of freedom for higher order discretisations. Usefully accurate results for the mean flow quantities could even be obtained with half as many degrees of freedom per direction (in comparison to reference LES solutions). Usage of high-order spectral element methods (CG in particular) is therefore strongly motivated for wall-bounded turbulence simulations via under-resolved DNS (uDNS), sometimes called implicit LES (iLES), approaches.

© 2020, © 2020 Taylor & Francis.The present study investigates the evolution of the residual stresses in TWIP steels induced by manufacturing chain for the production of automotive body-in-white. Two different manufacturing routes were considered. The first route encompassed a plastic deformation prior to the welding stage, whereas the second involved the spot welding followed by a baking treatment. A convergent approach was adopted to isolate the effects of the first and final manufacturing steps. The findings showed that the plastic deformation prior to the welding stage is not annihilated by the welding thermomechanical cycle. Abrupt hardness gradients along small material fractions are observed. The residual stresses state changes, although its profile is still defined by the welding stage. The post-weld bake treatment showed to promote slight residual stresses relaxation, but it is not effective in inducing the same post-weld residual stresses state for different RSW parameters set.

© 2020, Society for Experimental Mechanics.The multireflection grazing incidence X-ray diffraction method (MGIXD) was used to analyze the surface residual stresses in 7050 Al alloy samples. This technique can provide a non-destructive stress profile in function of sample depth, avoiding the relaxation effects intrinsic to destructive methods. The state of residual stress in aeronautical aluminium samples was modulated by milling and shot peening processes. After structural characterization, the residual stress states of the samples were analyzed by multireflection and conventional stress measurement methods. The milled samples presented tensile surface residual stress relaxation attributed to thermal effects and the shot peened samples showed strong compressive stress at sub-surface, which intensity was reduced near the surface. The residual stress profiles of the Al samples were obtained by MGIXD method that evidenced properties commonly undetected in conventional residual stress studies.

© 2019 Elsevier B.V.Manufactured components are submitted to thermo-mechanical loads that can blemish their surface integrity and change the inherent residual stress distribution. The discontinuous machining process is relevant to the integrity conception because of their potential application at the end of the manufacturing chain. In order to consolidate a method to predict the residual stress state with a reduced CPU effort, this paper addresses the prediction of residual stress fields resulting from the milling process. The approach is using the hybrid FEM approach combined with the analysis of the plastic flow. The results obtained point out to the validity of the combination of the hybrid method and the visualization of the equivalent stress and equivalent strain rates. Moreover, a direct correspondence between the references and experimental dataset was observed, even when the input data for the model is associated with macro-loads obtained by piezoelectric platform measurements. The determination of the stress state as residual stress in mainly associated to the mesh convergence and the time to equilibrate the plastic flow. A conclusion is drawn regarding the viability of applying the same combination for other manufacturing processes.

© 2020, The Brazilian Society of Mechanical Sciences and Engineering.This article presents a novel morphing unit cell concept which relies on the combination of shape memory alloy wires for actuation and permanent magnets to enable multistability. Two distinct applications are investigated experimentally, consisting in a morphing beam metastructure made with three unit cells and a variable camber airfoil metastructure having six unit cells in the chord-wise direction. Tests are performed to assess the influence of the permanent magnets on the morphing behavior of the two referred metastructures. It is verified that the permanent magnets are able to provide new stable equilibrium configurations to the metastructure and to reduce the time necessary for morphing. Another interesting feature, which enables the reduction in energy consumption, is that, due to the magnetic interactions, the thermal activation of the SMA wires can be ceased once an equilibrium configuration is achieved. The paper describes the design premises, evaluates its limitations and devises future improvements.

© 2020, Journal of Aerospace Technology and Management. All rights reserved.This paper studies the influence caused by a vortex generator (VG) on a wing section with NACA 0015 airfoil when this generator is located before and after a recirculation bubble caused by the boundary layer detachment. The study was numerically carried out and concentrated under conditions of flow with Rec = 2.38 × 105 and angles of attack AoA = 3 and 6, characterized by the fact that they undergo detachment of the boundary layer before and after the location of the VG, respectively. The use of the generator in AoA = 3 strongly influenced the reduction of the recirculation bubble, leading to a drag reduction of 1.43%. In AoA = 6 with a bubble recirculation, the effect was much lower, with no well-defined formation of longitudinal vortices, resulting in increased drag and lift at 0.33 and 0.35%, respectively.

© 2020 IEEE.Optimization of motion cueing algorithms is a relevant topic in flight simulation industry. To achieve this goal, a representative model of the motion platform is needed. With this intent, this work presents a black-box approach to identify a model for the SIVOR flight simulator. The model receives position/orientation inputs in Cartesian space and streams out accelerations/angular speeds measured on the pilots' head. A comprehensive experimental analysis is carried out using a dataset based on isolated positional and rotational inputs. A frequency domain analysis is performed to evaluate signal measurement noise and to determine the model structure. As a result, a combination of continuous time linear transfer functions were identified to represent each of the direct and cross relations mapped throughout the process.

© 2020 IEEE.The aim of this work is to implement a representative dynamics model of the SIVOR flight simulator. Two experiments were conducted and used to estimate and validate the model; the first one excites one robot channel at once and the second excites more than one robot channel. Based on a previous study, we established the model structure. Three distinct approaches of black-box identification model were employed: transfer function models, space-state models and ARX models. The results obtained were similar and satisfactory for inputs until 1 Hz.

© 2020, Univelt Inc. All rights reserved.In this work, an attitude determination algorithm was developed for the 6U CubeSat satellite model of the Scintillation Prediction Observation Research Task (SPORT) mission. The project is a cooperation among the US Space Agency (NASA), American universities, the National Institute for Space Research (INPE) and the Aeronautics Institute of Technology (ITA). The work includes obtaining data from star, solar, magnetometer and gyro sensors and, with them to carry out, the attitude estimation. One of the requirements of the mission is the accuracy of attitude determination, which is only satisfied by the star sensor. However, there are periods in which the star sensor does not have valid measures, therefore, there is a need to study methods to improve the attitude given by the solar sensor and magnetometer. Thus, the TRIAD algorithm, in addition to the Kalman Filter, were analyzed to achieve the most accurate result within the established requirement. It was concluded that when the star sensor does not present valid measures, the analyzed case that fulfilled the requirements was the Kalman Filter with the TRIAD algorithm.