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Abstract: The present study discusses about the effect of installation torque on the surface and subsurface deformations for thin walled 7075 aluminum alloy used in Aerospace applications. A FE model was constructed to predict the effect of torque induced stresses on thin walled geometry followed with an experimentation. A detailed surface analysis was performed on 7075 aluminum in terms of superficial discontinuities, residual stresses, and grain deformations. The localized strain hardening resulting from increased dislocation density and its effect on surface microhardness was further studied using EBSD and micro indentation. The predicted surface level plastic strain of .25% was further validated with grain deformations measured using optical and scanning electron microscopy.

In applications demanding high performance under extreme conditions of pressure and temperature, a range of Mechanically Attached Fittings (MAFs) is offered by various Multinational Corporations (MNCs). These engineered fittings have been innovatively designed to meet the rigorous requirements of the aerospace industry, offering a cost-effective and lightweight alternative to traditional methods such as brazing, welding, or other mechanically attached tube joints. One prominent method employed for attaching these fittings to tubing is through Internal Swaging, a mechanical technique. This process involves the outward formation of rigid tubing into grooves within the fitting. One of the methods with which this intricate operation is achieved is by using a drawbolt - expander assembly within an elastomeric swaging machine.

The present study discusses about the determination of the Seal drag force in the application where elastomeric seal is used with metallic interface in the presence of different fluids. An analytical model was constructed to predict the seal drag force and experimental test was performed to check the fidelity of the analytical model. A Design of Experiment (DoE) was utilized to perform experimental test considering different factors affecting the Seal drag force. Statistical tools such as Test for Equal Variances and One way Analysis of Variance (ANOVA) were used to draw inferences for population based on samples tested in the DoE test. It was observed that Glycol based fluids lead to lubricant wash off resulting into increased seal drag force. Additionally, non-lubricated seals tend to show higher seal drag force as compared to lubricated seals. Keywords: Seal Drag, DoE, ANOVA

Abstract: Hydraulic systems in aircrafts largely comprise of metallic components with high strength to weight ratios which comprise of 2024 Aluminum and Titanium Ti-6AL-4V. The selection of material is based on low and high pressure applications respectively. For aircraft fluid conveyance products, hydraulic conduits are fabricated by axisymmetric turning to support flow conditions. The hydraulic conduits further carries groves within for placement of elastomeric sealing components. This article presents a systematic study carried out on common loads experienced by fluid carrying conduits and the failure modes induced. The critical failure locations on fluid carrying conduits of 2024-T351 Aluminum was identified, and the Scanning Electron Microscope (SEM) analysis was carried out to identify the characteristic footprints of failure surfaces and crack initiation. Through this analysis, a load to failure mode correlation is established.

Electromechanical actuators (EMAs) play a crucial role in aircraft electrification, offering advantages in terms of aircraft-level weight, rigging and reliability compared to hydraulic actuators. To prevent backdriving, skewed roller braking devices called "no-backs" are employed to provide braking torque. These technology components are continuing to be improved with analysis driven design innovations eg. U.S. Pat. No. 8,393,568. The no-back mechanism has the rollers skewed around their own transverse axis that allow for a combination of rolling and sliding against the stator surfaces. This friction provides the necessary braking torque that prevents the backdriving. By controlling the friction radius and analyzing the Hertzian contact stresses, the brake can be sized for the desired duty cycle. No-backs can be configured to provide braking torque for both tensile and compressive backdriving loads.

Battery Electric Vehicles (BEV) are a well-recognized de-carbonization lever that is expected to capture about 15% of road vehicle fleet by 2030 [1, 2]. A large number of organizations are committing to science-based targets (SBTi) and are following roadmap strategies towards Greenhouse Gas (GHG) reduction including all value chain players such as material suppliers, component manufacturers and OEMs [3]. In BEVs, several components are involved in energy transformation and delivery. These components themselves consume energy, and therefore are a cause of GHG emissions during their use. To quantify their contributions and help corporations progress towards decarbonization strategies there is a need for robust use phase calculation methodology. Existing global methods for calculating use phase emissions, such as Green House Gas (GHG) Protocol (version 1.0), provide a good framework, but still have uncertainties in its practical application.

Wet-sump transmissions are widely used in heavy duty and medium duty vehicles. As these transmissions do not have a dedicated forced lubrication system, it is important that the gear train, shafts, and enclosure are designed appropriately so that enough oil splashes to critical locations to ensure sufficient lubrication. The lubrication effectiveness of such transmissions can be studied through detailed tests or numerical simulations. Often, the vehicle, and therefore the transmission, encounters some severe operating conditions, such as climbing on an incline, driving downhill, etc. Studying these conditions through tests is an expensive process and this imposes the need for an analysis first approach. In this paper, the 3D multiphase Volume of Fluid (VOF) method is used to examine two such extreme cases: an 8-degree tilted installation of transmission in a vehicle, and an inclined condition of transmission during a 10-degree uphill climb.

Roots blower is a rotary positive displacement pump which operates by pumping a fluid with a pair of meshing lobes. Recent trends in automotive industry demands high power density solutions for various applications. In comparison with legacy applications, compressors for high power density applications demand continuous operation with harsher duty cycle as well as demand higher pressure ratios. Because of longer duty cycles, it will be subjected to high heat loads which will cause a rise in temperatures of timing gears, bearings, and other components within the assembly. Accurate prediction of thermal performance is critical to design a durable and efficient roots blower for high power density applications. Thermal analysis of an assembly of roots blower involves modelling of multi-physics phenomena. This paper details a coupled CFD analysis approach to predict temperatures of roots blower components and timing gear case oil. Timing gears are lubricated using wet sump lubrication.

Wear phenomenon has extensively been published in the literature and this paper presents a methodology of how the wear models were used to assess the risk of failures in a field application, through endurance testing at a system level. Correlation of the wear prediction by the model with actual measurement was performed and used to predict the field operation reliability. Results are shown for sliding wear as well as impact wear phenomenon in this paper. In the case of sliding wear, wear modeling and prediction was done for a friction material using a system level metric, and the mean wear predicted was not different from the model predicted values at 95% confidence under a field application duty cycle.

Manufacturing processes such as casting, welding and additive manufacturing (AM) are prone to internal porosity and high surface roughness on the manufactured parts. These defects are inherent in the process and cannot be completely eliminated. Handling, transportation and maintenance of manufactured parts can also lead to defects such as scratches and dents due to abusive loads. The defects can be characterized in a number of ways, assuming they resemble a U-notch or V-notch, elliptical pores, or a continuous distribution of consecutive defects in combination with surface roughness. The designer utilizes existing analytical and empirical equations to predict stress concentration due to presence of various types of defects and compute factor of safety to ensure structural integrity of design subjected to various load cases. The applicability of existing analytical and empirical equations is studied, and modifications are suggested to improve the predictions.

The use of electrical contacts in aerospace applications is crucial, particularly in connectors that transmit signal and power. Crimping is a widely preferred method for joining electrical contacts, as it provides a durable connection and can be easily formed. This process involves applying mechanical load to the contact, inducing permanent deformation in the barrel and wire to create a reliable joint with sufficient wire retention force. This study utilizes commercially available Abaqus software to simulate the crimping process using an explicit solver. The methodology developed for this study correlates FEA and testing for critical quality parameters such as structural integrity, mechanical strength, and joint filling percentage. A four-indenter crimping tool CAD model is utilized to form the permanent joint at the barrel-wire contact interfaces, with displacement boundary conditions applied to the jaws of the tool in accordance with MIL-C-22520/1C standard.

With the advent of wide band gap semiconductor devices like SiC based MOSFETs/Diodes, there is a growing demand for utilizing electrical power instead of the conventional fuel-based power generation in both automotive and aerospace industry. In automotive/aerospace industry the focus on electrification has resulted in a need for sub-systems like inverters, power distribution units, motor controllers, DC-DC converters that actively utilize SiC based power electronics devices. To address the growing power density requirements for electronics in next generation product families, more efficient & reliable thermal management solution plays a critical role. The effective thermal management of the power electronics is also critical aspect to ensure overall system reliability. The conventional thermal management system (TMS) optimization targets heat sink/ cold plate design parameters like fin spacing, thickness, height etc. or sizing of the required cooling pump/fan.

Improving fatigue resistance is a key factor to design components for advanced vehicle transmissions. The selection of materials and heat treatment plays a crucial role in controlling fatigue performance of power transmission components such as gears and shafts. Traditional, low frequency fatigue testing, used for identifying fatigue limit or generating S-N curve for multiple sets of material parameters is highly time consuming and expensive. Hence, it is necessary to develop the capability to predict fatigue performance of materials at different loading conditions with limited amount of data for instance the hardness and inclusion size. In the present work, we have evaluated behavior of the carburized steel subjected to axial and torsional cyclic loading conditions at low frequencies.

Historically manufacturing variability has been considered as a noise factor due to limited insights about manufacturing history and its influence on part performance. With improvement in computational power and enhancements in commercial simulation tools, it is now feasible to study the influence of manufacturing process on product life in addition to manufacturability. This study demonstrates the concept of as manufactured part performance prediction utilizing forming simulation software to capture deformed geometry along with residual stresses and its integration to performance simulation tool using sheet drawing operation. Simulation predictions are verified and validated with available experimental data. This approach helps to visualize the variation in part performance with respect to manufacturing process change including process sequence, process parameters and tooling design change.

The primary objective of this research was to identify the root cause of limited slip differential (LSD) NVH. The study examined the significance of different oils and additives that make up the lubrication mix in the axle. The impacts of gear marking compound type, friction modifier type, gear marking compound level, friction modifier level, reaction plate surface finish roughness, and friction material type were studied using Taguchi's Design of Experiment. Eaton's Vertical Friction Tester (VFT), a sub-system level test stand, was used to measure the performance characteristics of the clutch pack and oil mix. Sequential approximation and cumulative analysis methodologies were used to analyze test data where NVH was beyond the measurement capacity of the test stand. The DOE analysis showed that the type of gear marking compound used to set the ring gear mesh during axle build had the most significant influence on NVH levels.

Commercial vehicles require fast aftertreatment heat-up to move the SCR catalyst into the most efficient temperature range to meet upcoming NOX regulations while minimizing CO2. The focus of this paper is to identify the technology levers when used independently and also together for the purpose of NOX and CO2 reduction toward achieving 2027 emissions levels while remaining CO2 neutral or better. A series of independent levers including cylinder deactivation, LO-SCR, electric aftertreatment heating and fuel burner technologies were explored. All fell short for meeting the 2027 CARB transient emission targets when used independently. However, the combinations of two of these levers were shown to approach the goal of transient emissions with one configuration meeting the requirement. Finally, the combination of three independent levers were shown to achieve 40% margin for meeting 2027 transient NOx emissions while remaining CO2 neutral.

Cold spray (CS) is a rapidly developing solid-state repair and coating process, wherein metal deposition is produced without significant heating or melting of metal powder. Solid state bonding of powder particles is produced by impact of high-velocity powder particles on a substrate. In CS process, metal powder particles typically of Aluminum or Copper are suspended in light weight carrier gas medium. Here high pressure and high temperature carrier gas is expanded through a converging-diverging nozzle to generate supersonic gas velocity at nozzle exit. The CS process typically uses Helium as the carrier gas due to its low molecular weight, but Helium gas is quite expensive. This warrants a need to explore alternate carrier gases to make the CS repair process more economical. Researchers are exploring another viable option of using pure Nitrogen as a carrier gas due to its significant cost benefits over Helium.

Bolted joint is a popular method for assembly of mechanical systems which are typically designed by considering members to be in full contact without initial gap. However, manufacturing imperfections or part tolerances can introduce gaps between members. This initial gap is proven to have an adverse effect on the performance of bolted connection. The gap introduces additional bending moments (B.M.) during tightening operation and affects the loads shared by the threads thereby aggravating thread strip and fatigue performance. The aim of this paper is to provide a robust approach for predicting this premature failure of bolted joint due to initial gaps in assembly. VDI 2230 industry guideline for fastener assessment does not account for bending effect due to initial gap. To address this limitation, a “Coupled Analytical and FEA based” approach is developed to accurately capture initial bending moment and its effect on distribution of loads between the engaged threads.

With the future of mobility moving towards electrification, there is an ever-increasing demand in both aerospace and automotive industry for achieving higher power density in inverters, controllers, etc. This has made thermal management a challenging task and warrants a need for exploring innovative cooling techniques to manage the dissipated heat. This paper focuses on a liquid cooled thermal management system for power dense applications. The heatsink design presented here is a pin fin arrangement staggered to induce swirling flow, which has been proven to enhance heat transfer. The traditional heatsink optimization involves creating a design of experiments (DoE) with parameters like fin diameter, spacing and height and performing thermal simulations to arrive at a design with enhanced heat transfer characteristics.

It is important to allocate reliability goal of the system to its subsystems or components in the early design stage of the new product design and introduction project. Reliability allocation can be equal or weighted. For weighted reliability allocation the weighing factors are required for corresponding failure modes or subsystems or components. Currently, these weighing factors are determined using FMEA (Failure Mode and Effect Analysis) method, Engineering Judgement method or Expert Opinion method. An implementation of these methods takes longer time and efforts to converge the allocation output; because the input parameters to these tools are definitive of functional and physical domain of the system, which typically gets evolved, matured and finalized at the later stage of a product definition phase. Also, in certain cases deployment of these methods are prone to immature inputs causing rework and lack physics of failure analysis for life performance.