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.
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.
RAMBHA-LP (Radio Anatomy of Moon Bound Hypersensitive Ionosphere and Atmosphere - Langmuir Probe) is one of the key scientific payloads onboard the Indian Space Research Organization’s (ISRO) Chandrayaan-3 mission. Its objectives were to estimate the plasma density and its variations on the near lunar surface. The probe was initially kept in a stowed condition attached to the lander. A mechanism was designed and realized to meet the functional requirement of deploying the probe at a distance of 1 meter, equivalent to the Debye length of the probe in the moon’s plasma environment. The probe deployment mechanism consists of the Titanium alloy spherical probe with a Titanium Nitride coating on its surface to achieve a constant work function, a long carbon-fiber-reinforced polymer boom, a double torsion spring, a dust-protection box, and a shape-memory alloy-based Frangibolt actuator for low-shock separation. The entire mechanism weighed less than 1.5 kilograms.
Aerospace structural components grapple with the pressing issue of high-cycle fatigue-induced micro-crack initiation, especially in high-performance alloys like Titanium and super alloys. These materials find critical use in aero-engine components, facing a challenging combination of thermo-mechanical loads and vibrations that lead to gradual dislocations and plastic strain accumulation around stress-concentrated areas. The consequential vibration or overload instances can trigger minor cracks from these plastic zones, often expanding unpredictably before detection during subsequent inspections, posing substantial risks. Effectively addressing this challenge demands the capability to anticipate the consequences of operational life and aging on these components. It necessitates assessing the likelihood of crack initiation due to observed in-flight vibration or overload events.
In the racing world, speed is everything, and the Formula Student cars are no different. As one of the key means to improve the speed of the car, lightweight plays an important role in the racing world. The weight reduction of unsprung metal parts can not only improve the driving speed, but also effectively optimize the dynamic of the car, so the lightweight design of unsprung parts has attracted much attention. In the traditional Formula Student racing car, the hub and spoke are two independent parts, they are fixed by four hub bolts or a central locking nut, the material of these fasteners is usually steel, so it brings a lot of weight burden. In order to achieve unsprung lightweight, a new type of wheel part design of Formula Student racing car is proposed in this paper. The hub and spoke are designed as integrated aluminum alloy parts, effectively eliminating the mass of hub bolts or central locking nuts.
The electrochemical pseudo-two dimensional (P2D) model is one of the most promising approaches that provide suitable physical depth at reasonable computational costs for the simulation of lithium-ion batteries. The parameterization of the P2D model plays an important role as it decides about the acceptance and application range of subsequent simulation studies. Electrical impedance spectroscopy (EIS) is commonly applied to characterize the batteries and to obtain the exchange current density and the electrode diffusion coefficient of a given electrode material. EIS measurements performed with frequencies ranging from 1 MHz down to 10mHz typically do not cover clearly isolated solid state diffusion processes of lithium-ions in positive or negative electrode materials. To extend the frequency range down to 10µHz, the distribution relaxation times (DRT) is a sound analysis method.
Mo free 1.6GPa bolt was developed for The Variable Compression Turbo (VC-Turbo) engine, which is effective for environmental friendliness and improving fuel efficiency and output. Mo contributes not only to the improvement of temper softening resistance, but also the improvement of delayed fracture resistance by precipitating fine carbides during high-temperature tempering and effecting as trap sites for hydrogen, so the main issue is to achieve both high strength and delayed fracture resistance. Therefore, developed steel is added Si to improve tempering softening resistance and achieve a microstructure superior to delayed fracture resistance to achieve both high strength and delayed fracture resistance. The delayed fracture test was done by Hc/He method. Hc means the limit of the diffusible hydrogen contents without causing delayed fracture under tightening, and He means diffusible hydrogen contents entering under the hydrogen charging condition equivalent to actual environment.
Abstract: Vehicle weight reduction is a popular research topic in automobile industry to achieve high efficiency and cost-effectiveness vehicles. Self-piercing rivets (SPR) are one of important joining approaches in light weight vehicle design. Numerical simulation of the riveting process could significantly boost design efficiency by reducing trial-and-error experiments. The traditional Finite Element Method (FEM) with element erosion cannot capture the large plastic deformation and complex failure behaviors in SPR process. Smoothed Particle Galerkin Method (SPG) is a genuine meshless method which is established basing on Galerkin weak form. SPG method uses a novel bond-based failure mechanism to keep the conservation of mass and momentum during material failure process. In this study, a combined FEM and Smoothed Particle Galerkin (SPG) approach was utilized to join sheet Aluminum 5754 and Cast aluminum Aural-2 using a full three-dimensional (3D) model in LS-DYNA/explicit.
Automotive body structures are being increasingly made in multi-material system consisting of steel, aluminum (Al) and fiber-reinforced plastics (FRP). Therefore, many joining tech-niques such as self-piercing riveting (SPR) and adhesive bonding have been developed. On the other hand, OEMs want to minimize the number of joining techniques to reduce the manufacturing complexity. Amount all joining methods, resistance Spot welding (RSW) is the most advanced and cost-effective one for body-in-white. However, RSW cannot be applied for joining dissimilar materials. Therefore, a novel Rivet Resistance Spot Welding method (RRSW) was developed in which Al or FRP Components can be directly welded to steel structures with existing welding systems. RRSW uses rivet-like steel elements as a welding adapter which are formed into Al or FRP components dur-ing their forming process. After that, they are welded to the steel components by RSW. This paper shows at first the results on Steel – Al RRSW.
The microstructure and mechanical properties of the Al-Si-Mg alloy with bulk and lattice structure produced by Laser-powder bed fusion additive manufacturing were systematically investigated. And then, the microstructure behavior of Al-Si-Mg alloys according to As-built and heat treatment was closely analyzed. Firstly, through grain size analysis, the cause of mechanical properties higher than casting materials and similar to forging materials could be analyzed. Secondly, mechanical changes according to the Mg2Si reinforced phase and cell-wall morphology after heat treatment were investigated. The Al-Si-Mg bulk and lattice structures are composed of a cell structure consisting of α-Al and eutectic Si. With heat treatment, needle-shape Mg2Si precipitates in the α-Al matrix. Simultaneously, collapse of the cell-wall morphology occurs.
Vibrations constitute a pivotal factor affecting passenger comfort and overall vehicle performance in both Conventional Internal Combustion Engine (ICE) vehicles and Electric Vehicles (EVs). These vibrations emanate from various sources, including vehicle design and construction, road conditions, and driving patterns, thereby leading to passenger discomfort and fatigue. In the pursuit of mitigating these issues, natural fibers, known for their exceptional damping properties, have emerged as innovative materials for integration into the automotive industry. Notably, these natural fiber-based materials offer a cost-effective alternative to traditional materials for vibration reduction. This research focuses on evaluating natural fibers mainly hemp, banana and cotton fibers for their damping characteristics when applied to a steel plate commonly used in the automotive sector.
Fiber-reinforced plastics (FRPs), produced through injection molding, are increasingly preferred over steel in automotive applications due to their lightweight, moldability, and excellent physical properties. However, the expanding use of FRPs in diverse automotive components presents a critical challenge: deformation stability. The occurrence of warping significantly compromises the initial product quality due to challenges in component mounting and interference with surrounding parts. Consequently, addressing warping in fiber-reinforced plastic-based injection parts is paramount for achieving high-quality parts. In this study, we present a comprehensive approach to address warpage issues in injection-molded components using FRPs. We employed a systematic Design of Experiments (DOE) methodology to optimize materials, processes, and equipment, with a focus on reducing warpage, particularly for the exterior part of a delivery EV.
Options for CNVII emission legislation are being widely investigated in a national program organized by China Vehicle Emission Control Center (VECC) since early 2020. It is foreseen that this possibly last legislation in China will have more stringent emission requirements compared to CNVI, including further reduction of nitrogen oxide (NOx), inclusion of nitrous oxide (N2O) and sub-23 nm particle number (PN) and etc. This study investigates the technical feasibility to fulfill a CNVII emission legislation scenario, based on a modified CNVI 8 L engine operating under both cold and hot World Harmonized Transient Cycle (WHTC) and Low Load Cycle (LLC). Methods to address the challenges are discussed and validated, including a twin dosing system, electric heater, hybrid concept of combining Copper (Cu-), Iron (Fe-) and Vanadium (V-) SCR technologies, high filtration DPF and optimization of engine calibration and urea dosing strategies.
Lithium-ion batteries (LIBs) serve as the main power source for contemporary electric vehicles (EVs). Safeguarding these batteries against damage is paramount, as it can trigger accelerated performance deterioration, potential fire hazards, environmental threats, and more. This study explores the damage progression of a commercial vehicle LIB module containing prismatic cells under crush loading. We employed computational simulations of mechanical loading tests to investigate this behavior. Physical tests involved subjecting modules to low-speed (0.05 m/s) indentations using a V-shaped stainless-steel wedge, under 6 unique loading conditions. During the tests, the force and voltage change with wedge displacement were monitored. Utilizing experimental insights, we constructed a finite element (FE) model, which included the key components of the battery module, such as the prismatic cells, steel frames and various plastic parts.
Hot-rolled AHSS grades are utilized in automotive parts where high formability is required. However, these grades can fail below their predicted formability limit due to edge cracking. Microstructure and sheared-edge face quality contribute to the initiation of micro-cracks that lead to edge cracking. While it is established that strain incompatibilities between phases and micro-constituents with differing hardness promote edge cracking, microstructural properties governing edge ductility are not fully understood. The edge ductility of eight hot-rolled automotive AHSS grades with tensile strengths of 600 and 800 MPa, achieved with single- or multi-phase microstructures, are being investigated. The experimental and structural single-phase grades include microstructures comprised of ferritic matrices with composite micro-alloyed nano-precipitates and cementite micro-constituents.