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Technical Paper

Influences of Martensite Morphology and Precipitation on Bendability in Press-Hardened Steels

2022-03-29
2022-01-0238
Performance evaluation of martensitic press-hardened steels by VDA 238-100 three-point bend testing has become commonplace. Significant influences on bending performance exist from both surface considerations related to both decarburization and substrate-coating interaction and base martensitic steel considerations such as structural heterogeneity, i.e., banding, prior austenite grain size, titanium nitride (TiN) dispersion, mobile hydrogen, and the extent of martensite tempering as result auto-tempering upon quenching or paint baking during vehicle manufacturing. Deconvolution of such effects is challenging in practice, but it is increasingly accepted that surface considerations play an outsized role in bending performance. For specified surface conditions, however, the base steel microstructure can greatly influence bending performance and associated crash ductility to meet safety and mass-efficiency targets.
Technical Paper

True Fracture Strain Measurement and Derivation for GISSMO Calibration

2022-03-29
2022-01-0237
The importance of true fracture strain was initially highlighted in the context of local versus global formability considerations used in material selection among advanced high strength steels (AHSSs) of similar tensile strength. Inspired by the relative studies, a precedent work had compared the discrepant fracture strain results from the digital image correlation (DIC) and the optical measurement techniques. This work further investigated various factors, such as the measurement techniques, the effective strain formula, and the fracture surface morphology, which could affect the true fracture strain measurement and derivation results, and subsequently the calibration of the Generalized Incremental Stress State dependent damage Model (GISSMO) used in crash simulations. In the meantime, explanations and discussions on the possible mechanisms behind these effects were also presented.
Technical Paper

Padded Self-Piercing Riveting (P-SPR) on magnesium high pressure die casting

2022-03-29
2022-01-0249
Padded self-piercing riveting (P-SPR) is a newly developed multi-material joining technology to enable less ductile materials to be joined by self-piercing riveting (SPR) without cracking. A deformable and disposable pad was employed to reduce the stress distribution on the bottom surface by supporting the whole bottom sheet continuously during rivet setting process. To verify the P-SPR process, 2.0mm thick 6061-T6 wrought aluminum was joined with 3.2mm thick coated AM60B magnesium high pressure die casting (HPDC) by using 1.0mm thick dual-phase 600 (DP600) steel as the pad. Regular SPR processes with 2 different die geometries were studied as a comparison. Compared to the regular SPR processes, P-SPR demonstrated advantages on coating protection, crack mitigation and joint strength.
Technical Paper

Development of FE modeling Procedures for Laser Welded Aluminum Structures in An Electric Vehicle Battery Module and Validation by Test Data

2022-03-29
2022-01-0317
High strength and thin materials are widely adopted in modern electric vehicles for lightweight design to achieve high energy efficiency. For battery modules, 5000 and 6000 aluminum are typically utilized as a structural material with a thickness range between 1 to 5 mm. Laser welding is one of the most optimum welding tools for joining such a thin material due to its unique advantages, e.g., high welding speed, high accuracy, high energy yet the smallest possible heat affect zone, etc. This paper aims to develop a simplified yet effective FE modeling procedure to simulate the laser welding effects on the aluminum structures used in electric vehicle battery modules. A sequentially-coupled thermo-mechanical analysis procedure is developed to determine the softened zone size for aluminum weldments. Then a tie-rupture weld model incorporates the softened zone to predict the weld failure strength.
Technical Paper

Developments of Composite Hybrid Automotive Suspension System Innovative Structures (CHASSIS) Project

2022-03-29
2022-01-0341
The Composite Hybrid Automotive Suspension System Innovative Structures (CHASSIS) is a project that developed structural commercial vehicle suspension components in high volume utilising hybrid materials and joining techniques to offer a viable lightweight production alternative to steel. Three components were selected for the project:- • Front Subframe • Front Lower Control Arm (FLCA) • Rear Deadbeam Axle
Technical Paper

An Investigation of the simulation of sintering distortion in a 316L Part manufactured using Bound Metal Deposition 3D printing

2022-03-29
2022-01-0346
Metal binderjetting is a high throughput additive manufacturing process that has the potential to meet the needs of automotive volume production. In many cases, this process requires a sintering post-process to meet final dimensions. Because the sintering stage is performed free standing (i.e. without the use of tooling) and can involve up to a 20% dimensional change from green part to the final part shape, part distortion can be a concern. In this study, the sintering stage of a bridge geometry was simulated under different parameter settings using a Finite Element Analysis. The sensitivity of the simulation to various process parameter inputs was examined. Parts were then produced in 316L using a bound metal deposition and sintering process and compared to prediction. The sintering simulation indicated good agreement with experiment for some dimensions but highlighted the need for additional analysis.
Technical Paper

Prediction of Crash Performance of Adhesively Bonded Vehicle Front Rails

2022-03-29
2022-01-0870
Adhesive bonding provides a versatile strategy for joining metallic as well as non-metallic substrates, and also offers the functionality for joining dissimilar materials. For problems of elastic behavior and small strains in vehicle unibody structures such as designing for NVH (Noise, Vibration and Harshness), adhesive bonding of sheet metal parts along flanges provides enhanced stiffening of body and improved acoustics due to sealing of openings between flanges. However, due to the brittle nature of adhesives, they remain susceptible to failure under impact loading conditions which can cause crumpling of sheet metal parts resulting in plasticity and large strains. The viability of structural adhesives as a sole or predominant mode of joining stamped sheet metal panels into closed hollow sections such as hat sections thus remains suspect and requires further investigation.
Technical Paper

Ultimate Breakage Load Calculation Method of Cold Gas Inflator Burst Disk

2022-03-29
2022-01-0764
For cold gas Inflator, high refinement of ultimate load forecast is one key of Inflator development. At beginning, two methods based on implicit algorithm, Zero Curvature method and RIKS method were used for burst disk hydro-burst test ultimate pressure load calculation. After considering the effect of bursting disk stamping process, comparing with results of real test, the refinement of the two methods were above 97% both. Studying the corresponding relations between displacement and stress matrix of the center point of burst disk by RISK method. It was found that under ultimate load, the third principal stress vs. displacement curve of the central node shown extreme point, and load step of the point was corresponding the one of maximum pressure load. This shown that after reaching the ultimate load, the center of the bursting disc lost stability in the direction of thickness.
Technical Paper

Nonlinear Finite Element Calculation of Cold Gas Inflator Housing Ultimate Breakage Load Based on Arc-Length Method

2022-03-29
2022-01-0766
For cold gas Inflator, high refinement of ultimate pressure load forecast of inflator housing is one key of Inflator development. For inflator housing hydro-burst test ultimate load FEA calculation, arc-length method is utilized for obtaining high precision results. At beginning, the material parameters of inflator housing for simulation is correlated. The FEA material model adopts the stress-strain data from uniaxial tensile experiments. Considering the geometrical nonlinearity resulting from large deformation as well as material nonlinearity from plastic hardening, the whole tensile process from tensile deformation to failure of the specimen is stimulated by utilizing the arc-length method. Numerical results show that the arc-length method is appropriate to predict the entire deformation process, and the obtained key deformation stages, the distribution and inclined angle of the localized necking occurs also agrees with that of theoretical analysis.
Technical Paper

Influence of Manufacturing Processes on the Structural behavior of Truck Frame Rail Sections

2022-03-29
2022-01-0754
The sequence of manufacturing processes involved in the making of ladder shaped truck frame rail assembly leave certain amount of manufacturing and assembly imperfections in the form of plastic deformation and residual stresses in some areas of frame rail ‘C’ sections. The plastic deformation and the resulting residual stress should not be allowed to cross the safer limit as it would affect the structural behaviour of the frame rail while interacting with the externally induced loading stresses from extreme road operating conditions. If the combined stress level crosses the yield limit of the frame material, it may lead to premature failure of frame rail much before it gives the expected life. One such manufacturing induced premature failure in a truck frame rail assembly during proving ground trials was studied in detail using experimental analyses and presented in this paper.
Technical Paper

A new approach to check the heath of engine mounting & suspension bolted joints

2022-03-29
2022-01-0634
The torque required to tighten any threaded joint is different from the necessary torque to untighten threaded bolt or nut, and it is not observed or widely known since this is a regular and straightforward operation. Typically the torque needed to untighten a newly tightened clamp is around 10% to 30% less than the torque to stretch it further. During tightening a threaded bolt, a significant amount of torque required to overcome friction in the threads and under the nut face. The proportion of the torque used to overcome frictional resistance depends upon the friction value. When we tighten a joint with a coefficient of friction of 0.12, only about approximately 14% of the torque required to stretch the fastener producing the clamp load with 86% of the torque is lost overcoming friction. The torque needed to pull the bolt always acts in the untightening direction, resulted in untightening torque lags behind the tightening torque.
Technical Paper

Engine combustion hardware diagnostics in an end-of-line cold test stand

2022-03-29
2022-01-0270
Internal combustion engines must be individually tested at the end of the manufacturing process. In recent years classical hot test stands, where the engine is run for several minutes, are being replaced by cold test alternatives. The latter allow fast testing cycles using an external motoring device without using any fuel. The absence of fuel and combustion lowers the health and safety requirements for the plant itself and subsequent engine transport, but this comes at the cost of additional difficulties for the verification of the correct assembly and operation of the combustion system hardware. This paper presents a cold test concept, which includes dedicated measurements and algorithms for the detection of standard failures in the manufacturing process, including those of the combustion hardware.
Technical Paper

Determination of Johnson Cook material parameters for ballistic impact simulation

2022-03-29
2022-01-0350
Armour plates made up of high strength steels is used in fabrication of protective covers of armoured vehicles. The analysis of ballistic impact events and the response of armour plates is much useful for design improvements. Ballistic impact is a very complex event as it occurs in a very short period and is influenced by number of parameters. These parameters are difficult to be quantified and considered in FE analysis. Due to this, the physics of the event is not accurately captured in numerical simulation. Considering these parameters require extensive experimentation which incurs huge costs. Due to advances in the explicit finite element codes and material models, it is possible to determine these parameters by reducing the dependence on experiments. In this study, Johnson-Cook material and failure model parameters are determined for the target armour plate by performing a DOE study with minimal test data.
Technical Paper

Research on electromagnetic shielding technology of special vehicle-mounted shelter based on material-structure co-design

2022-03-29
2022-01-0351
In order to meet the needs of modern warfare, the research on electromagnetic shielding technology of military vehicle-mounted shelters and improving the electromagnetic shielding performance of shelters will play an increasingly important role in the protection of advanced electronic equipment. At the same time, it is also the core of the development of military vehicle-mounted shelters. In this paper, by selecting and comparing different materials, using multi- layer composite materials to design the military vehicle-mounted shelter. The shelter body comprises a front wallboard, a rear wallboard, a left wallboard, a right wallboard, an upper wallboard and a lower wallboard.
Technical Paper

Exploring New Joining Techniques of CFRP Cross Member Chassis

2022-03-29
2022-01-0337
Increasing fuel prices and escalating emissions standards, are leading car manufacturers to develop vehicles with higher fuel efficiency. Reducing the mass of the vehicle is one technique to improve fuel efficiency. Shifting from metals to composite materials is a promising approach for great reductions to the vehicle mass. As more composite parts are introduced into vehicles, the approach to joining components is changing and requiring more investigation. Metallic chassis components are traditionally joined with mechanical fasteners, while composites are generally joined with adhesives. These adhesive joints require a large contacting surface between components for proper bonding. However, simply increasing surface area for adhesives joints may lead to inefficient use of the added material, increasing the overall mass of the component with little performance gain.
Technical Paper

Improving Keyhole Stability During Laser Welding of AA5xxx Alloys

2022-03-29
2022-01-0247
Laser welding of the magnesium-bearing AA5xxx aluminum alloys is often beset by keyhole instability, especially in the lap through joint configuration. This phenomenon is characterized by periodic collapse of the keyhole leaving large voids in the weld zone. In addition, the top surface can exhibit undercut and roughness. In full penetration welds, keyhole instability can also produce a spikey root and severe top surface concavity. These discontinuities could prevent a weld from achieving engineering specification compliance, pose a craftsmanship concern, or reduce the strength and fatigue performance of the weld. In the case of a full penetration weld, the spikey root could compromise part fit-up and corrosion protection, or damage adjacent sheet metal, wiring, interior components, or trim.
Technical Paper

Development & Deployment of Bolted joint integrity evaluation for Automotive suspension joints

2022-03-29
2022-01-0761
Bolted joints are the most commonly used joints in automotive suspension assemblies. They are expected to retain the strength over the course of useful life of the vehicle and contribute to durability in a big way through reduction of stress amplitudes. Any sort of loosening or slip or breakage in these joints can lead to noise or catastrophic failures. In the past, such issues were addressed through thumb rules & design guidelines. However, with the focus on first-time right Tests with reduced Validation time it has become important to upfront predict the suspension joint integrity through simulation. Toward this objective, a novel approach was developed to upfront simulate the suspension joint integrity for bolted joints. This approach considers various parameters like bolt preload, tolerance stackup of the parts in the joint, coefficients of friction of various interfaces, quality of contact & effect of deformation at the thread interface on joint integrity.
Technical Paper

Technical Keynote: Magnesium Sheet Component Development and Demonstration Project

2022-03-29
2022-01-0248
Most of the applications of magnesium in lightweighting of commercial cars and trucks are die castings rather than sheet metal, and automotive applications of magnesium sheet have typically been experimental or low-volume serial production. The overarching objective of project was to develop new low-cost magnesium alloys, and demonstrate warm-stamping of magnesium sheet inner and outer door panels from a 2013 MY Ford Fusion at a fully accounted integrated component cost increase over conventional steel stamped components of no more than $2.50/lb. saved. The project demonstrated the computational design of new Mg alloys from atomistic levels, cast new experimental alloy ingots and explored thermo-mechanical rolling processes to produce thin Mg sheet of desired texture. A new commercial Mg alloy sheet material was sourced and pretreated with protective coil coatings, and its properties fully characterized.
Technical Paper

An Integrated Approach for Simulation of the RTM Process

2022-03-29
2022-01-0326
In the preform preparation stage of the RTM process, the fabric is draped on the mold along the geometry. Before the filling and warpage analysis, the draping analysis will be performed to get the fabric orientation. Due to the anisotropy of the fabric material, the main direction of the material has a significant influence on the overall flow behavior and warpage of the product. In this study, the advanced simulation approach for the RTM process is demonstrated. The filling and warpage analysis integrate with the draping simulation result from AniForm. The influences of fabric shearing and fiber orientation on the resin flow and warpage in RTM process is studied. With more accurate fabric orientation prediction methods, the accuracy of predicting fabric ply orientation is improved and more accurate infusion and product warpage simulation results can be obtained.
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