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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

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

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

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

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

Variable axial composite light weight automotive parts using anisotropic topology optimization and tailored fiber placement

2022-03-29
2022-01-0344
Continuous fiber composites are an important material for realization of lightweight structures. In the last decade, there has been great progress in fabricating continuous fiber composite parts in terms of local fiber orientation control by robotics and the additive manufacturing technologies. These technologies include continuous fiber printing (CFP), tailored fiber placement (TFP) and automated fiber placement (AFP). One common challenge of these technologies resides in the design method. These methods can fabricate local orientation-controlled composites, so called variable axial composites (VACs), which show great performance improvement when appropriately designed for given loading conditions; however, they may not be as robust as conventional quasi-isotopic composites due to misalignment of load path and fiber path. Therefore, design of both structure and fiber orientation considering load conditions is highly critical and demands high engineering skills.
Technical Paper

An Alternative Approach to Determine Johnson-Cook Material and Failure Model Parameters with Minimal Experimental Data

2022-03-29
2022-01-0279
Complex events such as a ballistic impact are influenced by number of parameters. Simulation of such events need a number of material parameters to be defined. These parameters are difficult to be quantified and considered in finite element 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, a method is depicted to determine Johnson-Cook material and failure model parameters. An example of a projectile hitting the armor plate is used to depict this method and to determine these material parameters for the target armor plate by performing a DOE study with minimal experimental test data.
Technical Paper

Effect of geometric parameters on folding of thin-walled steel tube under axial compression

2022-03-29
2022-01-0264
This study investigated the plastic deformation behavior of 304 stainless steel thin-walled tubes under axial compression by means of numerical calculation and theoretical analysis. It was found that the plastic deformation length of thin-walled tube determined the formability of folds and the work done in the whole axial compression process. To reveal the relation between the range of plastic deformation length and tube geometry parameters, regression equations were established using the quadratic regression orthogonal design method. Experiments were conducted to validate the equations. The process windows for forming a single fold and tube joining at ends had been printed ultimately. The results showed that the regression equations can accurately predict the range of plastic deformation length for forming a single fold.
Technical Paper

Thermomechanical behavior of an automotive exhaust aftertreatment application

2022-03-29
2022-01-0277
An aftertreatment system is the back-end component of an automotive exhaust system, used mainly to reduce pollutant emissions. This system is exposed to high thermal loads which can exceed temperatures of 900 oC , usually they operate at temperatures under 600 oC - 700 oC, depending of the engine application. The durability assessment of a system under thermomechanical loads can be challenging due to the complexity of the technical problem, which involves complex material behavior at high temperatures and results in high thermomechanical strains and stresses. This study presents a computational approach for the lifetime assessment of an exhaust aftertreatment system subjected to thermomechanical loading. The method is composed of a fluid flow analysis to compute the temperature fields which are mapped to a mechanical analysis combined with a nonlinear elastoviscoplastic material behavior. Lastly, the lifetime of the overall assembly is assessed through a fatigue analysis.
Technical Paper

Electrical insulation property of an alumina coating on a bearing steel SAE 52100

2022-03-29
2022-01-0726
In recent years, bearing electrical failures have been a significant concern in electric cars, restricting electric engine life. The most frequent material used to make bearings is 52100 alloy steel. This work aims to introduce a coating approach for preventing electrical erosion on 52100 alloy steel samples. This paper summarizes the causes of shaft voltage and bearing currents. Meanwhile, the paper discusses standard electrical bearing failure mechanisms, such as morphological damages and lubrication failures. Alumina coatings are suitable for insulating the 52100 alloy steel samples because alumina coatings provide excellent insulation, hardness, and corrosion resistance, among other characteristics. Based on the research, this article briefly discusses employing plasma electrolytic aluminating to coat 52100 alloy steel samples, an eco-friendly and high-efficiency coating process.
Technical Paper

Polyetherimide for magnet wire application

2022-03-29
2022-01-0334
Magnet wire is composed of conducting core and thin layer of electrical insulation. Cupper (Cu) is typically used as conducting core, and various polymers such as polyamideimide, polyimide, and polyesterimide are used for electrical insulation. The role of magnet wire is involved in interchanging between electrical energy and mechanical energy for energy transformation application such as transformer, motor, generator, and many other equipment. Currently, electric vehicles (EV) industry is rapidly growing and consequential demands on related components are increasing as well. Compared to combustion engine, EV needs more electrical power with higher voltages or higher currents, which can increase probability of electrical discharge. The degradation of insulation layer can happen with the polymer bond breakage under the partial discharge electric stresses.
Technical Paper

Ultra High Pressure sensor with MEMS sensor element mounted on the measurement membrane manufactured by MIM

2022-03-29
2022-01-0417
This paper presents a ultra high pressure sensor composed the measurement membrane manufactured by MIM(Metal Powder Injection Molding). The membrane should be sufficiently deformed within the measuring pressure range and not be broken at the burst pressure. Therefore, in general, the high pressure sensor membrane made of metal using machining methods such as milling and drilling [1]. However, it requires additional process to assembly with other parts and is difficult to make complex structure such as screw. Thus, in this paper, we propose the product and design of the measurement membrane using the MIM method. We have developed the ultra-high pressure sensor capable of measuring to 900 bar.gauge. Figure 1 shows the ultra-high pressure and measurement part. The measurement membrane thickness is 900 ㎛ and diameter is 3.2 mm. The MEMS sensor element mounted on the measuring membrane surface outputs an electrical signal according to the pressure.
Technical Paper

Simultaneous Free-Size, Gauge, and Composite Optimization for Automotive Chassis Design

2022-03-29
2022-01-0792
Rising gas prices and increasingly stringent vehicle emissions standards have pushed automakers to increase fuel economy. Mass reduction is the most practical method to increase fuel economy of a vehicle. New materials and CAE technology allow for lightweight automotive components to be designed and manufactured, which outperform traditional component designs. Topology optimization and other design optimization techniques are widely used by designers to create lightweight structural automotive parts. Other design optimization techniques include free-size, gauge, and size optimization. These optimization techniques are typically used in sequence or independently during the design process. Performing various types of design optimization simultaneously is only practical in certain cases, where different parts of the structure have different manufacturing constraints.
Technical Paper

Parts Consolidation of Automotive Front Subframe: From Two-Piece CFRP Design to One-Piece Design

2022-03-29
2022-01-0342
As demand for fuel efficiency rises, an increasing number of automotive companies are replacing their existing metal designs with carbon-fiber-reinforced polymer (CFRP) redesigns. Due to the handling and manufacturing processes associated with CFRP materials, engineers have more design freedom to create complex, light-weight designs, which would be infeasible to manufacture using metal. Additionally, it is likely that by redesigning with CFRP, many steel assemblies can be consolidated to significantly fewer parts, simplifying or potentially eliminating the assembly process. When designing a subframe using CFRP materials, designers often aim for a two-piece design (top and bottom), while utilizing reinforcement material where needed. The joining of these two pieces is typically accomplished with many mechanical fasteners and adhesives, significantly increasing the part count and the manufacturing complexity.
Technical Paper

Investigation of the Drag Losses of Wet Clutches at Dip Lubrication

2022-03-29
2022-01-0650
Wet running multi-plate clutches and brakes are important components of modern automotive and industrial powertrains. In the open stage, drag losses occur due to fluid shearing. This subsequently can lead to a perceptible reduction in the overall drivetrain efficiency. Depending on the application and requirements, injection or dip lubrication is used. For the first one there is already a deep fundamental understanding existing, whereas the latter was not extensively investigated so far. This contribution gives a detailed insight in the experimental research of the drag losses of wet running multi-plate clutches at dip lubrication. In a base study the flow conditions and origins of the drag torque generation were investigated. Built on this, the effects of operating and geometry parameters such as oil viscosity and level, clearance, groove design, disk size and number of gaps on the drag loss characteristic were determined based on a full-factorial testing.
Technical Paper

Efficient Processing of Material Property Definition to Predict Fracture of AHSS in Crash Analysis

2022-03-29
2022-01-0236
Advanced High Strength Steel (AHSS) with high strength and deformation resistance is applied to automotive components and plays an important role in protecting passengers in the event of a crash, as well as contributing to fuel economy improvement by reducing the weight of the car body. However, due to the low ductility of the AHSS, there is an issue about the occurrence of fracture during a vehicle crash. In order to cope with these problems from the early design stage, preliminary verification is made through crash CAE analysis, but a high level of material property definition is required for fracture prediction. To predict fracture, many tests are required to secure the base data for parameter calculation of a complex fracture model, and a lot of physical time is required to verify the model. This paper aimed to semi-automate the material parameter calculation and verification process for efficient and reliable fracture prediction of AHSS.
Technical Paper

Polypropylene composite material for light weight fuel tank protection shield

2022-03-29
2022-01-0336
The fuel tank shield provides a protective boundary between the fuel tank and vehicle driveline in the event of a high-speed crash. Hence, it is important from the safety standpoint. The part must be carefully engineered to meet the challenging requirements in terms of stiffness, deflection, toughness, dimensional stability and thermal stability. In this paper, long glass fibre filled polypropylene material compound was selected and developed to meet the mentioned requirements for this part with significant mass reduction over other materials. The combination of material, optimized part and tool design led to weight savings and considerable cost reduction. This is a ready to mold material used in injection molding process.
Technical Paper

Non-destructive Evaluation of the Magnetic Quality of Electrical Steel Sheets by Magnetic Barkhausen Noise (MBN) Analysis

2022-03-29
2022-01-0235
Soft magnetic lamination core is a major component of all electric motors, and the magnetic quality of the lamination has a significant effect on the energy efficiency of the motor. The magnetic properties of electrical steel sheets, which are important design parameters for the manufacturing of electric motors, are normally measured on cut steel strips by standard Epstein frame method, which is destructive and is not suitable for the evaluation of magnetic anisotropy. This paper presents a relatively new technology, i.e., magnetic Barkhausen noise (MBN) analysis, to evaluate the magnetic quality of electrical steel sheets. This method is featured by non-destructive, simple measurement, short measuring time, and online/offline measurements, etc. In addition, it can be readily used to estimate the magnetic anisotropy of electrical steel sheets.
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