© 2023 Elsevier LtdThe study aims to evaluate the microstructural sensitive aspects of contact fatigue crack initiation and its evolution during the gear lifetime. Tests were performed to evaluate different stages in the evolution curve of gear contact fatigue. The magnetic Barkhausen noise (MBN) technique was used to characterize variations in the magnetic response in gears during the incipient gear contact fatigue mechanisms initiation. For a complete comprehension of the surface degradation, residual stresses, microstructure, and microhardness were explored. A substantial increase in the MBN signal is identified before the fatigue failure occurs, indicating the occurrence of microstructural alterations that change the magnetic properties. The early stages of contact fatigue are accompanied by a surface softening in the near-surface region, up to approximately 40 µm depth. These phenomena were also followed by a less compressive residual stress region at 20 µm depth. A lower influence of microstrains on the diffractogram can be observed by the full width at half maximum parameter (FWHM), indicating a higher amount of dislocation annihilation during the appearance of the initial stages of the contact fatigue mechanism. The study concludes by proposing a comprehensive approach to understand the mechanisms behind the early stages of gear contact fatigue and how the MBN signal can be used to detect fatigue damage.

© FTM 2024.All rights reserved.This study addresses the Magnetic Barkhausen Noise (MBN) technique as a non-destructive testing method for detecting contact fatigue in gears within an industrial context. The primary objective is to evaluate the MBN signal evolution during the lifetime of gears, specifically aiming to detect contact fatigue failures in their early stages, before any visible damage appears at the flank surface. Fatigue testing was conducted on five gear samples, inducing a natural evolution of gear contact fatigue. Monitoring MBN signals at regular intervals during testing cycles allowed for correlation with surface integrity degradation. Furthermore, the study delves into microstructural aspects related to contact fatigue, exploring various stages in the MBN evolution curve. The MBN technique was employed to characterize magnetic response variations during the initiation of contact fatigue mechanisms. In-depth analyses of residual stresses, microstructure, and microhardness provided a comprehensive understanding of surface degradation. A substantial increase in the MBN signal was identified before fatigue failure, indicating microstructural alterations affecting magnetic properties. Early contact fatigue stages were characterized by surface softening in the near-surface region, up to approximately 40 µm depth, accompanied by a less compressive residual stress region at 20 µm depth. The study also observed a lower influence of microstrains on the diffractogram, suggesting higher dislocation annihilation during the initial stages of contact fatigue. Results revealed a significant variation in MBN signals influenced by operational loads during tests, with a noteworthy increase observed just before gear failure. Using a scale from 0% (manufactured condition) to 100% (failure), the study successfully detected failures at 17% of the gear's lifespan, providing valuable insights for early failure detection in industrial applications. The findings conclude by proposing a comprehensive approach to understanding early gear contact fatigue mechanisms and highlighting the MBN signal's utility in detecting fatigue damage.

© FTM 2024.All rights reserved.The knowledge of the residual stress state is of interest to the gear industry due to its critical role in avoiding fatigue failure mode. Since fatigue cracks are always nucleated and propagated under tensile actuating stresses, a suitable compressive residual stress state is desirable to decrease the total stress profile, by the superposing principle. Usually applied as the last process of the gear manufacturing chain, grinding provides both thermal and mechanical loads, from which residual stresses are induced. The intensity of such loads is associated with the material removal rate (MRR); however, it is not constant along the tooth profile, due to the complex kinematics of gear grinding process. The objective of this study is then the comprehension of how the variation of material removal rate along the tooth profile influences the grinding-induced residual stresses. Case-hardened steel discs were manufactured with different material removal rates, induced by varying grinding parameters. The ground surface integrity of such simplified samples was characterized in terms of residual stress distribution on the surface and in-depth profile. ITA Geometry gear samples were manufactured with profile gear grinding. The characterization of the surface integrity state of the ground teeth was similar to the disc assessment and showed a good correlation regarding the material removal rate and the residual stress state along the tooth profile. Such results highlight that a strategic definition of grinding parameters by material removal rate can improve the residual stress state, leading to more reliable gear fatigue prediction.

© 2024 The Authors. Published by Elsevier B.V.Additive Manufacturing (AM) is vital for industrial innovation, offering high potential for groundbreaking solutions. However, its successful implementation still depends on overcoming several challenges. Particularly, the assessment of surface integrity in AM-generated components, and its degradation when subjected to contact stresses presents an ongoing endeavor. Within this context, the current work delves into the study of the surface integrity of 20MnCr5 case-hardened samples manufactured through laser powder bed fusion (L-PBF), as well as delves into the investigation of surface failure progression when the samples are subjected to cyclic contact stresses. This study encompasses the analysis of residual stresses, hardness, and roughness of specimens manufactured through both additive and conventional production routes. The study's findings show that it is feasible to attain analogous surface quality when proper finishing is applied to L-PBF samples. Although, despite the comparable surface quality, the contact fatigue performance was significative lower on the AM sample when compared to the conventionally manufactured. Additionally, additive manufacturing brings up new challenges to performance by presenting a heterogeneous stress distribution and sub-superficial porosity. In conclusion, to attain a desirable surface integrity for additive manufactured parts, further research should not only focus on improving the process parametrization but should also developing finishing routes especially oriented to additive manufacturing, considering therefore how the interaction between the manufacturing processes will evolve into a desirable surface integrity state.

© 2024, The Author(s), under exclusive license to Springer Nature Switzerland AG.Mobility electrification advent has affected the vehicle systems’ design requirements, especially for the powertrain components. Αmong the critical fields affecting the functional performance of future powertrain components is their geometrical accuracy. For gears, the necessity of tighter manufacturing tolerances is related to the much higher rotational speeds involved in the electric motor operation than the internal combustion engine. Although the gear flank tolerance classification establishes the limits of tolerable deviations, there is no treatment regarding how different deviation factors can differently influence the dynamic behavior of gears. Therefore, when standards suggest that high-speed gears require improved tolerance classes, all deviation factors are considered a group. In the case of mobility industries like the automotive, tightening tolerance classes represent a challenge. So, the objective of the present study was the assessment of the influence of different gear deviation factors in tooth contact patterns to identify possible different effects among them. So, tooth contact analyses were performed by computational simulations for a gear sample. The influence of manufacturing profile and helix slope deviations of different tolerance classes in the contact pattern was investigated. The results have demonstrated that a class modification in helix slope deviation has a higher impact on the maximum contact pressure than a class modification in profile slope deviation. When assembly deviations are also considered, the distinct influences are intensified. Identifying the most influential deviation parameters allows the gear manufacturing sector not to have to tighter all tolerances to guarantee an adequate e-mobility gear operation.

© 2023 Elsevier B.V.The current study proposes a shot peening model which enables the residual stress interaction with grinding, a typical combination for gear finishing. The effect of the interaction on the stress state development was addressed by comparing the residual stress state from a standalone shot peening procedure, against the residual stress state arising from a manufacturing route where the interaction of shot peening and grinding takes place. In the interaction model, the grinding procedure generates a pre-loaded condition on the material, modifying the internal strain system of the gear tooth. This pre-loaded system, when disturbed by shot peening, reaches a new internal strain equilibrium. In the interaction model, a 24% less compressive stress state was attained when compared with the standalone shot peening process. A significant shift in the depth and magnitude of the peak compressive stress was also observed. On account of the numerical study of the processes’ interaction, the developed model substantially contributed to understanding the residual stress formation during manufacturing chains.

© 2023 the authors.In recent years, the automotive sector has shown a trend toward electrification in all segments. The introduction of the electric motor brings with it a set of new challenging requirements for the transmission system, which can potentially be addressed by coatings technology. Doping MoS2 coatings with transition metals have recently received great attention in many engineering areas due to their unique optical, electrical, and excellent lubricating properties. These novel composite coatings are acclaimed for improving tribology performance under sliding-rolling conditions, especially with Ti doping. The focus of this research will be the replacement of Ti as dopant element by Nb, which presents similar physical properties and promising results in terms of its application as self-lubricant coating, according to few previously reported studies. In this work, investigations of MoS2-based coatings innovative doped with Nb obtained via PVD magnetron sputtering process considering different deposition parameters and substrate surface integrity were studied for gear applications. A deposition system with independent high-purity targets was used to obtain coatings with tailored microstructural, mechanical, and tribological properties. Some tests were performed to determine the coating microstructural and mechanical properties, the adhesion on carburized SAE 8620 steel samples, commonly used for gear applications, and also the influence of the substrate residual stress state on coating behavior. Preliminary results suggest a significant influence of the metal doping content on the mechanical and tribological properties of the coatings. The obtained coatings showed lower coefficient of friction and proper adhesion on carburized SAE 8620 steels, also influenced by the substrate surface integrity. Moreover, the results suggest that further studies on Nb:MoS2 coatings for transmission systems applications are promissory to enhance the durability and efficiency of gears.

© 2023 The Authors.Market movement towards sustainability and electromobility impose new demands on the gear Industry in terms of materials, design and manufacturing. In this context, laser powder bed fusion (L-PBF) has been under the spotlight for being one of the most promising technologies in additive manufacturing (AM), allowing the designer to think beyond traditional constraints. On the other hand, anisotropic properties, distortions, and heterogeneous residual stress may lead to excessive stress states during finishing processes. For carburizing materials, such as 20MnCr5, the mechanisms leading to residual stress and distortions go beyond the temperature gradient mechanism (TGM) and incorporate significant microstructural changes due to phase transformation. The combination of these phenomena with the gear manufacturing chain places a significant challenge to the gear industry. Therefore, this study investigates the potential and challenges of manufacturing 20MnCr5 gears through L-PBF with focus on the surface integrity evolution along the manufacturing chain. The study addresses the processability of the material and investigates the surface integrity of the gears through the manufacturing chain. The composition of thermal and microstructural phenomena simultaneously occurring during print generates heterogeneous residual stress along the gear orientation. Contrary to the literature, the stress relief did not equalize the residual stress entirely. Therefore, the heterogeneous residual stress distribution observed in the as-built condition propagated through the entire chain. Even after three manufacturing operations, the pattern of residual stress after printing directly influenced the final residual stress state.

© 2023 The Authors.Indirect Selective Laser Sintering (iSLS) has shown disruptive potential to meet electromobility requirements for gears in terms of materials and product design. iSLS manufacturing allows for solutions in mass production mainly due to the speed of printing, when compared to direct additive manufacturing. However, there are still challenges regarding the processability of iSLS with carburizing alloy steels. Low densities arising from the intrinsic characteristics of the coated powder influence the mechanical strength. Shot peening appears as a potential solution to densify surfaces by inducing localized plastic deformation, but its implications are still poorly addressed in the literature. The objective of the study is an experimental investigation of the densification process by shot peening with parameter variations on the surface properties produced by iSLS. Both the decision of the peening parameters and the explanation to the densification phenomena were based on a numerical approach of the shot peening process. The density of the samples and the surface integrity features induced from printing to peening, such as topography and the residual stress state, were evaluated. The result provides insights, in the perspective of automotive applications, into the density of iSLS processing with carburized steels densification achieved by shot peening.

© 2022 John Wiley & Sons, Ltd.Advancements seeking structural components' strength and weight reduction necessarily pass through fatigue testing. Understanding failure phenomena and crack evolution is a way of methodologically achieving such a goal. An own-designed resonant fatigue test rig was used to study the behavior of three distinctly manufactured crankshaft batches. A control system and a resonant frequency estimator were developed to follow the overall stiffness reduction with crack advancement. The control algorithm followed the frequency decay to compensate for the input load. The control strategies were validated by finding the system's natural frequency at the beginning of the test and maintaining a constant nominal load. Fractographies made with failed and non-failed specimens revealed the connection between the expected physical results and the natural frequency shift evolution. The implemented logic enables crack advancement tracking and failure determination. The developments here can be overflown to different resonance fatigue systems to characterize their endurance performance.

© 2021, Korean Society for Precision Engineering.Powder metallurgy represents an alternative to increase sustainability in the manufacturing of automotive gears, but its potential is hindered by a certain lack of knowledge on surface integrity properties that can impair the gear performance. This study explores the effects of the microstructural differences induced by this chain on the residual stress heterogeneity state of gears. X-ray diffraction methods of macro residual stress mapping and line profile analysis were applied for measurements of gear teeth after subsequent steps of the powder metallurgy and the conventional wrought steel chains. The powder metallurgy chain induced more pronounced heterogeneities than the conventional manufacturing, characterized by non-uniform residual stress distributions along the lead and the involute profiles of gear flanks. These non-uniformities observed after carburizing were traced back to the previous steps, surface densification, sintering and compaction. The residual stress distribution patterns of these steps were compatible with the plasticity dynamics of each manufacturing process. Such surface integrity heterogeneities result in a residual stress gradient along the gears functional surface, exposing particular regions to be more susceptible to fatigue effects.

© 2022 The Authors.The evolution of residual stress (RS) induced by laser powder bed fusion (L-PBF) along post-processing steps of automotive carburizing steels is a topic still underexplored by the scientific community. In this study, L-PBF specimens of 20MnCr5 steel produced with different build orientations were subjected to the same stress relief, milling and carburizing steps. RS and the diffractogram full width of half maximum (FWHM) depth profiles obtained through X-ray diffraction were compared along the manufacturing chains. It was shown that the previous manufacturing steps influence the final RS state, from L-PBF to carburizing.

© 2021 Elsevier LtdThe increasing demand for high performance gears requires in-depth investigations of alternative materials to those commonly used. In this respect, microalloyed steels may appear as an alternative with technical and economic potential. Microalloyed steels may exhibit a more refined grain structure than conventional steels, which is commonly induced by the precipitation of highly stable and dispersed second-phase particles. This investigation aimed at understanding how the steel grain structure obtained by the addition of niobium (Nb) and titanium (Ti) as microalloying elements correlates to the material surface integrity promoted by a conventional gear manufacturing chain. The results indicated that the addition of microalloying elements leads to a refined and homogeneous grain structure. The residual stress state also proved to be both more compressive and homogeneous and the roughness exhibited greater stability. Such characteristics place the microalloyed steels in a prominent position regarding their application in the gear manufacturing, indicating the possibility of fatigue lifetime improvement.

© 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0)Triply periodic minimal surfaces such as Gyroid structures have been widely used in additive manufacturing as a strategy to reduce material usage, printing time, and part weight, which are of high interest by the automotive industry. Most Software dedicated to additive manufacturing have lattice tools for infill available, but they usually do not consider the influence of the infill strategy on the part`s mechanical properties. Therefore, this study analyzed numerically and experimentally the influence of lattices on the compressive behavior of samples manufactured by selective laser melting and developed a procedure to use the finite element method as a tool for mechanical properties evaluation. The procedure employed the software nTopology to generate gyroid structures and Ansys for the structural analyses. Different gyroid densities were numerically analyzed and samples with the best weight/stress ratio were selected for experimental validation with compression tests according to the ASTM E9 standard. The material considered was a carburizing steel DIN 5120 suitable for industrial applications. The results showed that the infill percentage is not associated with a linear relationship between weight and stress. It was observed that besides the infill ratio, the material distribution has a significant effect on the sample performance, which was affected by the stress concentration phenomena. A good representativity was found between the numerical model and experiments, enabling it as a reliable method to evaluate how the infill affects mechanical behavior

© 2021, Springer Nature Switzerland AG.A gap between basic research and production characterizes a technology colony. An open innovation alliance gives low-wage countries the chance to stand for technological leadership using the improved efficiency of resources. This chapter explores the “Engrena ITA” case study, an open innovation alliance created in Brazil for the gear technology sector. By sharing benefits and responsibilities, the initiative aims to enhance research prospections and knowledge dissemination. Along 2 years, the metrics of project prospection have become twice higher than the ones summed in the 6 years before its creation. Collective contribution in intellectual and financial aspects, as well as a systematic exchange between university and industry, shows to be the conversion motor from ideas to innovation. Organization proved to overcome the importance of resources available for innovation, indicating a feasible roadmap to unlink low-wage countries to technology colonies.

© Springer Nature Switzerland AG 2021.Over a hundred million gears are annually produced in Brazil. They are applied to automobiles, wind turbines, aircraft and sugar and alcohol energy systems, among others. Despite the variety of applications, these segments share similar demands for technological solutions within the same economic challenges to investing in innovation. This context engendered the launch of “Engrena ITA”, in 2017, as an alliance among organizations with the aim of enhancing research prospections about gears and power transmission systems. Sharing benefits and responsibilities among its members, Engrena ITA assumes the integrative role established by the Open Innovation concept. The operational essence is the systematic interaction among members, who receive the right of defining guidelines of the gear-dedicated research group of ITA. The fundamental interaction occurs in workshops twice a year. Deep technical discussions precede the definition of a priority list of research topics to be prospected. The top priority is taken to further discussions on the scope content, and its generated project proposal is submitted either to government calls or to a pool of companies. The first year of operation, executed as a pilot plan, joined 24 companies of the segment, from tooling developers to OEM’s. In one year, 15 projects were prospected, involving 29 organizations worldwide. Projects were prospected on a partnership basis, involving Brazilian and foreign research institutes. The systematic integration which drove new ideas creation is now the basis for the initiative’s continuity and for multiplying the model to further technologies.

© 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.

© 2019 Elsevier B.V.The authors regret that Fig. 4 is the same as Fig. 5 in the original publication, and that the correct Fig. 4 is missing. Please see below for the correct Fig. 4: [Figure presented] The authors would like to apologise for any inconvenience caused.

© 2019 Elsevier B.V.The limitations of the usual techniques applied for gear grinding burn detection are extended by the increasing demands on quality control within industrial feasibility. Although widely used, nital etching technique has a subjective character. Alternative techniques such as magnetic Barkhausen noise and X-ray diffractometry also present drawbacks such as variability of output based on external energy input that depends on parameter settings, high cost and destruction of tests parts. Due to this technical gap, an alternative method is suggested, where the remanent induction of a workpiece is measured by means of a Hall probe. The objective of this concept is to reduce external inputs on the workpiece, measuring its natural signal and correlating it to the material property induced by the damage. In this study, three different degrees of damage were investigated with the Hall method, covering damages with phase transformation as well as with modifications on the residual stress state. According to the results obtained, an alteration in the remanent induction which is directly correlated to the burn degree, was detected. The micro-magnetic theory establishes a correlation between the remanent magnetic induction and material hardness as well as residual stress state. The signal alteration detected by the Hall method is in accordance with the micro-magnetic theory for all three degrees of burn analyzed.

© 2018 Elsevier B.V.TWIP steel weld spots were produced by varying the following welding parameters: welding current, welding time and electrode clamping force. Hardness distributions along the weld spots cross section were obtained by Vickers microindentations. The mechanical strength and failure modes of the weld spots were assessed by tensile-shear tests. Weibull statistics was applied to statistically analyse the data from tensile-shear loading. The results highlighted the influence of welding parameters variations on the Vickers hardness and residual stress state. These properties have a positive correlation to the failure modes and so the mechanical reliability of the weld spots. Welds that failed in pullout mode and partial-interfacial failure mode have statistically higher load bearing capacity than those in interfacial failure mode. The combination of a welding current of 8 kA with a welding time of 16 cycles and an electrode clamping force of 2 kN showed to be the optimum parameters for the investigated TWIP steel weld spots. By using this optimum setup, it was possible to supress interfacial failure mode and to obtain pullout as the predominant failure mode, considerably increasing the mechanical reliability of the weld spots.

© 2017 Elsevier B.V.The contribution of the entire manufacturing chain to the final residual stress state cannot be neglected. In-between processes, the stress redistribution has to satisfy the equilibrium principle. An investigation was conducted on the manufacturing processes of gears. A convergent approach isolated the effects of the final production step. The processes’ interaction is understood by a model of springs, into a self-equilibrated potential energy concept. The influence of early production stages is revealed as the residual stress integral along the depth range mostly subjected to relaxation. Named as Unstable Area of Residual Stress (UARS), it was verified between machining and heat treatment, and between shot peening and grinding. The interaction is relevant to the gear fatigue behavior. Failure mode and lifetime correspond to the depth where the interaction effects were mainly observed.

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

© Institution of Mechanical Engineers.The residual stress analysis is a well-established method for predicting fatigue failures of mechanical components. Within industrial constraints, the X-ray diffraction is a technique usually applied to measuring a small spot of the workpiece surface. This punctual and averaged outcome does not allow the proper representation of the residual stress. The objective of this study is to define a feasible method for assessing the heterogeneity of the surface residual stress state. The proposal is based on the theoretical relationship between the deviation of the residual macrostress and the intensity of the microstress. Steel shot peened gears were produced and their microstresses were assessed by means of the diffraction profiles broadening. The reference database was composed of topography measurements, metallographic analyses and residual macrostress maps. The stress heterogeneity was reasonably correlated to the intensity of the Gauss integral breadth. Applied to ground parts, the correlation's parameter filled a comprehension gap between the measured residual stress intensity and observed contact fatigue failures. Using the same data from the macro residual stress measurement, the method proved to be feasibly applied. Moreover, by providing a deviation perspective to the residual stress state, the heterogeneity assessment enhances the analysis of a fatigue failure.

Copyright © 2015 SAE International.This work is developed under the context of determining a suitable power-recirculation gear test design. Its operation parameters are determined by the usual speed values to what the Brazilian automotive transmission systems are submitted. The operating parameters generate forces that act as a frequency source, inducing mechanical vibrations to the structure. The level of the vibrations must be supervised so it does not reach values which correspond to the structure natural frequency. In such cases, resonance zones and noise at the measurement devices occur, causing wrong measurement data and, even further, structural failures. This paper analyzes the application of a method to investigate operational conditions and, eventually, redesign the rig's main elements, to escape from resonance and noise zones. The modal analysis appears as a suitable tool for this purpose, giving as an output the description of structure natural vibration response. Because of the rig's recirculating characteristics, separated components of the bench influence the natural frequency of the entire structure. Therefore, the method developed must be applied at each of these components. The study starts with a modal analysis of the rig's rotary components, within the recirculating power concept. Additionally, the analysis is performed on two main bench's components: the gearboxes and the supporting structure. By means of a FEM analysis, the natural frequencies are determined and compared to the rig's operating frequencies. The study is concluded with the recommendations over the boundary conditions of different gear test procedures.

Copyright © 2014 SAE International.In the concept of a power recirculation gear test rig, two gear sets and the other machine elements are assembled in closed loop. The torque and the rotational motion are supplied independently, at distinct places of the system. This allows an optimization for the selection of the components responsible for power functions. However, this setup causes the analytical solution for the dynamic matricial equations to be rather complex. This project proposes the development of a computational method for the analysis of torque and rotation fluctuations in each shaft line of the test rig. Additionally, various operational conditions can be quickly simulated in order to assess the system response. The tool used is the software LMS Imagine.Lab AMESim®, a 1D multidomain simulation platform. The simulation inputs are the inertia, the stiffness and the friction data of the modeled components. Together with the torque and acceleration curves, it is possible to evaluate the actuating peak torques in the shafts and in the other parts. The most important output is the power that must be supplied by the motor. Thus it is possible to systematically define and select this component, avoiding arbitrary selection of a high cost item. Results show agreement with that indicated by the literature.

New technologies developed for automotive engines also have highlighted the transmission torque capacity as restriction factor in the development of enhanced vehicle dynamics performance. Generally, the restriction is defined by the lifetime of the first speed gear. At the end of the gear manufacturing process, shot peening is used to induce compressive residual stresses and further increase fatigue life. This research verified the influence of introducing a bimodal media size distribution into the shot peening process. The proposal is supported by the independent effects of each media class. A higher compressive residual stress can be obtained from larger spheres. And the use of a lower diameter media class improves the surface homogeneity. The bimodal distribution was defined with a probabilistic approach over plasticity and contact stress theories. The experimental validation scope includes a topography analysis and residual stress profile measurements. The results showed mixtures combining up to an increase of 30.9% in the compressive residual stresses without jeopardising the surface quality. The collected data supported the expectation for improving the gear lifetime. It also represented the validation of a new peening process. An improvement in the product properties can be achieved in comparison to the parts produced using conventional shot peening; additionally, a lower process lead time is required in comparison to that for dual peening. © 2013 Elsevier B.V. All rights reserved.

Hybrid peening is proposed to be applied with objective of improving gears fatigue life with low impact on part manufacturing time. This process consists of an alternative of a conventional dual peening, but with mixing two different media classes in only one stage. A procedure to define media classes' selection as well as mix distribution is proposed considering the objective of enhancing part lifetime, background of gear failure modes and residual stress theory, by using known residual stress profile prediction models. Results showed that it was possible to reach maximum compressive residual stress target, without being far from its depth desired. Copyright © 2009 SAE International.