Weight Of Car Body Research Articles

Methodic Approach for the Simulation-Based, Elastic Die Surface Compensation by Creating a FE-model of the Car Body Press Predicated on Spotting Images via Neural Networks

In recent years, the push for streamlined vehicle development and the adoption of higher-strength materials to reduce the car body weight has been prominent. However, this shift results in greater elastic deformations in press and tool components due to the elevated yield stress of these materials. The die active face is subject to the compliance of the body press and die, which influences the manufacturability and dimensional accuracy of the sheet metal part. In practice, manual die spotting is required, relying on empirical data and subjective criteria for acceptance. This paper presents a new methodological approach for the development of the car body press’s FE model in structural and forming coupled simulations. To achieve this, a series of measurements quantifies the pressure between tool and sheet metal. This information is fed into a neural network along with the die spotting images as training data. The network evaluates subsequent spotting images, assigning pressure values to distinct tool sections. Based on the die pressure distribution in the process, a virtual press model is created with the help of a newly developed objective function in topology optimization. This model aims to significantly enhance simulation-based die surface compensation, effectively reducing the die spotting process.

Evaluation of Joint Strength for CFRPs and Aluminum Alloys by Friction Stir Spot Welding Using Multi-Stage Heating

To reduce car body weight, multi-material structures with lightweight materials such as carbon-fiber-reinforced plastics (CFRPs) and aluminum alloys (Als) are used to replace parts of steel components, and joining technologies for such dissimilar materials are essential. Friction stir spot welding (FSSW) is one of the technologies used to rapidly and strongly join dissimilar materials. FSSW for carbon-fiber-reinforced thermosetting resin (CFRTS) and Als has been developed using composite laminates with integrally molded thermoplastic resin in the outermost layer. To suppress excessive heating under the tool, this study investigated whether multi-stage heating with a non-heating time during joining affects the heat distribution and strength properties of the joint. Due to heat diffusion in Al during the non-heating time, multi-stage heating can suppress excessive heating under the tool compared to continuous heating, resulting in up to 27% larger welded area, up to 37% smaller decomposed area, and up to 6% lower maximum temperature. The use of multi-stage heating results in up to 5% higher tensile shear strength and 210% longer fatigue life by reducing the thermal decomposition of CFRP matrix resin and PA12 resin.

MULTIBODY SIMULATION ANALYSIS OF A MONORAIL TRANSPORTATION SYSTEM

Multibody simulation enables engineers to examine and investigate the kinematic and dynamic motion of mechanical systems, allowing them to construct and develop virtual 3D models to simulate and illustrate motion, coupling forces and stresses. The purpose of this study is to analyse kinematic and dynamic characteristics of a monorail for urban transportation systems. The monorail will go through three simulations in Solidworks. The first simulation is motion analysis by moving along a straight and curved track under low-speed (10 m/s), medium speed (15 m/s) and high speed and (20 m/s). Next, static analysis due to weight of passengers and car body and finally the last simulation is dynamic analysis due to dynamic loads occurring at the stabilizing wheel. The collected result will then be compared with past studies to validate the multibody simulation. Most dynamic and kinematic characteristics show slightly similarity and some dynamic and kinematic characteristics turn out differently. The different characteristics are due to Solidworks errors during the simulation process..

A Numerical Evaluation of Forming Failure of an Aluminum Sheet due to Splitting Damage in Hole Expansion Process

Abstract The reduction of car body weight is the principal issue of car manufacturers for reducing fuel consumption. Aluminum alloys are attractive materials for the automotive industry because they have low density and adequate strength, but they may exhibit crack formation during manufacturing processes. Generally, crack formations emerge because of tool geometry and material anisotropy. Accordingly, determination of the forming limits of aluminum alloys is essential. The hole expansion test (HET) is a significant formability process used in the automotive industry because it gives information about the stretch-flangeability limits of the material. Edge splitting (edge fracture) is a failure type seen in HET, and it limits the stretch-flangeability of the material. Therefore, the prediction of edge splitting is an essential issue for engineers in the automotive industry. In this work, HET of AA6016-O aluminum alloy was simulated with the finite element (FE) method to assess the influence of yield functions on failure prediction in HET. To this end, Hill48, Yld91, and a homogeneous fourth-order polynomial type yield criteria (HomPol4) were selected to identify the anisotropic behavior of the sheet. Analyses were carried out in Marc commercial FE software, and the Hypela2 user subroutine was incorporated into FE code. Thickness distributions in the rolling direction (RD), diagonal direction, and transverse direction (TD) of the part and around the hole edge were also predicted, and it was observed that only the HomPol4 criterion predicted excessive thinning at two locations near the RD and TD, separately. On the other hand, Yld91 and Hill48 predicted lower strain levels when compared with HomPol4. Finally, plastic work distribution around the hole edge was considered, and the predictions were compared with the experimental damaged sample. This comparison showed that HomPol4 predicted a robust plastic work localization in RD, which is consistent with the damaged sample.

Effects of Diffusible Hydrogen on Fatigue Life of Spot Welds in High-tensile-strength Steel Sheets

Spot-welded advanced high-strength steel (AHSS) sheets are used to decrease car body weight and enhance crashworthiness simultaneously. Such welds are susceptible to hydrogen embrittlement, but research in this area is limited. We have evaluated the hydrogen embrittlement properties of spot welds fabricated with AHSS sheets and clarified the dependence of diffusible hydrogen content and tensile rate on tensile shear strength. However, the performance of spot welds must be evaluated not only by static testing such as tensile shear tests but also by dynamic fatigue testing. Herein, we investigated the effects of diffusible hydrogen on their fatigue life via tensile–shear fatigue tests under cathodic hydrogen charging. The number of cycles to failure and the endurance limit decreased with diffusible hydrogen content. The number of cycles to failure decreased as the constant amplitude-loading frequency declined. The intergranular cracking is more likely to occurs as the amount of diffusible hydrogen increases and as the frequency decreases. These results are explained by hydrogen accumulation and crack growth behavior caused by mechanism for hydrogen-enhanced local plasticity and hydrogen enhancement of the strain-induced generation of vacancies mechanism. Furthermore, the correlation between static testing and dynamic fatigue testing was investigated, and the relationship between fatigue strength and the amount of diffusible hydrogen was in good agreement with the diffusible hydrogen dependence of tensile shear strength obtained from slow rate tensile shear tests under hydrogen charging.

New insights into the fracture behavior of advanced high strength steel resistance spot welds

While the automotive industry is striving for the reduction of car body weight to increase the fuel efficiency and to reduce CO2 emission without compromising the safety and crashworthiness of vehicles, a new generation of advanced high strength steels (AHSS) have emerged as excellent candidates to meet these requirements. However, their integration into the car body structure is associated with welding-related problems. This research utilizes a novel approach to establish a fundamental correlation between welding parameters, microstructure and mechanical performance of AHSS resistance spot welds. In-situ micro-cantilever bending experiments are executed and analyzed in a quantitative manner to evaluate the effect of texture and post-welding heat treatment on the local fracture toughness of spot welds. A striking finding is that, through a switch from single to double pulse weld scheme, the texture of martensite formed in the fusion zone becomes responsible for a significantly higher fracture toughness of the area in front of the pre-crack. In addition, it is found that paint baking heat treatment also results in a much enhanced fracture toughness through tempering of the martensitic microstructure. A quantitative correlation is made between the micro-scale fracture toughness and macro-scale mechanical performance of advanced high strength steel welds.

Modelling and Analysis of Power-Regenerating Potential for High-Speed Train Suspensions

Sustainable technologies in transport systems have attracted significant research efforts over the last two decades. One area of interest is self-powered devices, which reduce system integration complexity and cost with an undoubtedly great potential for improving adaptability and developing sustainability in railway transport systems. One potential solution is a regenerative suspension system, which enables the suspension movements and dissipated energy to be converted into useful electricity. This paper explores the application of hydraulic–electromagnetic regenerative dampers (HERDs) under realistic railway operating conditions for a high-speed train (HST). A vehicle-track-coupled dynamics model is employed to evaluate the regenerative power potential of an HST suspension over a range of operating conditions. The work considers typical route curvature and track irregularity of a high-speed line and speed profile. It was found that power could be regenerated at a level of up to 5–30 W and 5–45 W per generation unit when fitted to the primary and secondary dampers, respectively. Such power-regeneration levels were adequate to supply a variety of low-power-consumption onboard components such as warning lights and wireless sensors. Further analysis of the carbody loading level also was carried out. The analysis revealed that, in the case of a high-speed journey, poor track geometry, low curvature, and reduced carbody weight increased the quantity of regenerative energy harvested by the HERDs. It was concluded that a suitable HERD design could be achieved that could facilitate the development of a smart railway damper that includes both self-sensing and power-generation functions.

High-strength steel components produced by hot metal gas forming

Advanced high-strength steels are promising materials for a variety of applications. They can be used in the automotive industry to reduce the car body weight and thus the fuel consumption as well. Very good mechanical properties can be obtained in martensitic steels by the quenching and partitioning process. Making complex-shaped parts using a single forming step is now possible with hot metal gas forming. Several heat treatment sequences were designed. One involved plain hardening to a temperature below the martensite start temperature. Another sequence was intended to explore the influence of the quenching and partitioning process. In this steel with a carbon content of 0.42%, tensile strengths in excess of 1800 MPa with elongations above 15% can be achieved.

Effects of different process parameters on mechanical properties and microstructures of hot stamping boron steel

Hot stamping process has been increasingly used to produce automotive parts with ultra-high-strength property. Thus, increasing the crashworthiness of new generation vehicles and reducing car body weight could be simultaneously obtained. Taking boron steel B1500HS as the research object, this paper built a set of hot stamping experiment equipment that could monitor the temperature of sheet metal and die in real time. The initial forming temperature, contacting pressure, and pressure holding time in hot stamping process were examined under the condition of continuous hot stamping when the die temperature got into dynamic stability. The microstructures and mechanical properties including tensile strength, elongation, and hardness of stamped blank were used as quality evaluation indexes. For B1500HS boron steel sheets with the thickness of 1.2 mm, the optimal process parameter combination of hot stamping process comes true when the initial forming temperature is 800 °C, the contacting pressure is 20 MPa, and the pressure holding time is 10 s. The high-quality hot stamping parts with compact martensite phase could be finally obtained at the tensile strength of 1495 MPa, elongation of 7%, and hardness of 510 HV.

Association between Different Modes of Travelling and Adiposity in Chilean Population: Findings from the Chilean National Health Survey 2016-2017.

Background: Active travel has been suggested as a feasible way of increasing physical activity levels. Although international studies have demonstrated its effect over different health outcomes and adiposity, there is still limited evidence on this topic in developing countries, such as Chile. Aim: To investigate the associations between different types of travelling and markers of obesity in the Chilean adult population. Methods: 5411 participants from the Chilean National Health Survey 2016–2017 (CNHS) were included in this study. Active travel was assessed using a questionnaire. Car commuters, public transport (PT), walking and cycling were the four forms of travelling assessed. Bodyweight, body mass index and waist circumference were used as markers of adiposity. Results: Compared to car travellers, body weight, WC and BMI levels were lower for PT walking and cycling travellers. The odds for obesity (Odds ratio (OR): 0.41 (95% CI: 0.28; 0.61 p ≤ 0.001) were lower for walking and the odds (OR: 0.56 (95%CI: 0.35; 0.89 p = 0.014) for central obesity were significantly lower for cyclist in comparison to car travellers. Additionally, participation in any form of active travel (walking or cycling) was low, with only 20.9% of the population reporting being active travellers. Conclusion: Active travel, such as walking and cycling, was associated with lower adiposity levels in the Chilean adult population. Promoting active travel could be a feasible strategy to tackle the high prevalence of obesity and physical inactivity in the Chilean population.

Influence of electrode force on metallurgical studies and mechanical properties of resistance spot welded dual phase (DP800) steel joints

Abstract The DP steels are attractive to automotive sectors due to the improved fuel efficiency, occupant’s safety and reducing the car body weight. The resistance spot welding (RSW) most appropriate eco-friendly process for sheet metal and white body car assemblies over fusion welding. The present research work analysis the impact of electrode force on mechanical and metallurgical characteristics of dual phase steel. In this investigation similar joint of DP 800 joints (lap shear and cross shear) specimen fabricated and tensile shear test was evaluated using a universal testing machine. Micro and macrostructure were evaluated optical microscope. The hardness was taken along the weld nugget using Vickers microhardness tester machine. The electrode force was varied at five levels (3.75 MPa to 4.75 MPa). The tensile shear strength is found to be increased with an increase in electrode force up to a certain limit and then it decreases. The microhardness survey revealed that peak hardness in the nugget zone and the hardness is lower in the HAZ. The softening of HAZ is mainly attributed to inter-critical heating during welding, which leads to weld failure.

Bending Property of Multi-Material Hat Shaped Member of CFRTP and Aluminum Alloy

CFRTP (Carbon Fiber Reinforced Thermoplastics) are expected to be used in the automobile parts due to their properties such as high specific strength and high specific stiffness in order to reduce the weight of car body. However, due to the expensive carbon fiber, the cost of CFRTP is high and its application to automobiles is limited. For mass-produced automobiles, a multi-material concept using a combination of dissimilar materials has been attracting attention. While the multi-material concept is often used to joint dissimilar materials, such as composite materials, high tensile strength steel, Al alloy and so on, the method of combining dissimilar material into one part is also expected. For the development of automotive parts, CAE technology is required and in order to apply multi-material concept to mass-produced automobiles, optimization method of materials and shape is necessary to be developed in the future. In this study, multi-material hat shaped members of CFRTP and aluminum alloy were molded by using hybrid molding method and their bending properties were evaluated. Their FEM analysis was also carried out and the relationship between material cost and mechanical properties were evaluated. When the surface of Al alloy is treated by electrolytic polishing, delaminating between Al alloy and CFRTP was suppressed and high stiffness multi-material hat shaped member can be obtained. The multi-material hat shaped member of CFRTP and Al alloy has superior specific stiffness as compared with molded products using only CFRTP for surface material, although the specific maximum bending load was lower.

Influence of Different Yield Loci on Failure Prediction with Damage Models

Advanced high strength steels are widely used in the automotive industry to simultaneously improve crash performance and reduce the car body weight. A drawback of these multiphase steels is their sensitivity to damage effects and thus the reduction of ductility. For that reason the Forming Limit Curve is only partially suitable for this class of steels. An improvement in failure prediction can be obtained by using damage mechanics. The objective of this paper is to comparatively review the phenomenological damage model GISSMO and the Enhanced Lemaitre Damage Model. GISSMO is combined with three different yield loci, namely von Mises, Hill48 and Barlat2000 to investigate the influence of the choice of the plasticity description on damage modelling. The Enhanced Lemaitre Model is used with Hill48. An inverse parameter identification strategy for a DP1000 based on stress-strain curves and optical strain measurements of shear, uniaxial, notch and (equi-)biaxial tension tests is applied to calibrate the models. A strong dependency of fracture strains on the choice of yield locus can be observed. The identified models are validated on a cross-die cup showing ductile fracture with slight necking.

알루미늄 기반 Advanced Multi-Material 기술의 선진 동향

Global warming is hot issue to keep the earth everlastingly. Despite the increase of the world population and the energy demand, the world oil supply and the oil price are hold the steady state. If we are not decrease the world population and the energy consumption, unforeseeable energy crisis will come in the immediate future.AMT acronym of Advanced Materials for Transportation is a non-profitable IEA-affiliated organization to mitigate the oil consumption and the environment contamination for the transportation. In recent, Annex X Multi-materials Joining was added to enhance the car body weight reduction cause the high fuel efficiency and the low emission of exhaust gas. Multi-materials are the advanced materials application technology to optimize the weight, the performance and the cost with the combination of different materials such as Al-alloy, Mgalloy, AHSS and CFRP.In this study, the trends of AMT strategy and Al-alloy based multi-materials joining technology were review. Also several technologies for Al-alloy dissimilar joining were investigated. Key words: Car body, Weight saving, AMT, Multi-materials, Dissimilar joining

자동차 산업에서 뿌리기술의 중요성 및 최신 용접/접합 기술

The automotive vehicle is made through the following processes such as press shop, welding shop, paint shop, and general assembly. Among them, the most important process to determine the quality of the car body is the welding process. Generally, more than 400 pressed panels are welded to make BIW (Body In White) by using the RSW (Resistance Spot Welding) and GMAW (Gas Metal Arc Welding). Recently, as the needs of light-weight material due to the CO2 emission issue and fuel efficiency, new joining technologies for aluminum, CFRP (Carbon Fiber Reinforced Plastic) and etc. are needed. Aluminum parts are assembled by the spot welding, clinching, and SPR (Self Piercing Rivet) and friction stir welding process. Structural adhesive boning is another main joining method for light-weight materials. For example, one piece aluminum shock absorber housing part is made by die casting process and is assembled with conventional steel part by SPR and adhesive bond. Another way to reduce the amount of the car body weight is to use AHSS (Advanced High Strength Steel) panel including hot stamping boron alloyed steel. As the new materials are introduced to car body joining, productivity and quality have become more critical. Productivity improvement technology and adaptive welding control are essential technology for the future manufacturing environment.

Description of microstructures and mechanical properties of boron alloy steel in hot stamping process

Hot stamping process has been increasingly applied for producing automotive parts with ultra-high strength property. Hereby, reduction of car body weight and increasing crashworthiness of new generation vehicles could be simultaneously achieved. In this work, a direct hot stamping of the boron alloy steel was investigated by experiment and FE simulation. Temperature evolutions of blank and dies were gathered during the experiments and verified with FE results. Metallographic analysis, hardness measurement and tensile test were performed for different locations of formed samples. Based on time–temperature–transformation (TTT) diagram, local emerged microstructure constituents and corresponding distributed hardness values of the stamped parts were predicted. Additionally, quenching tests under various media were carried out for the examined boron steel. Determined tensile stress–strain curves from each cooling condition were described using Voce hardening equation. Relationships between hardness and Voce model parameters were established. Then, developed constitutive equations were used in combination with the obtained FE results to evaluate local mechanical properties of hot stamped samples. It was found that calculated stress–strain responses for different areas fairly agreed with those from the experiments.

预变形对汽车用Al-Mg-Si-Cu合金析出行为的影响

To reduce the weight of car body, Al- Mg- Si- Cu alloys have been widely used to produce outer body panels of automobiles due to their favorable high strength- to- weight ratio, corrosion resistance, weldability and good formability. Al- Mg- Si- Cu alloys belong to age- hardenable aluminium alloys, whose strength derives mainly from the matrix precipitation during aging treatments. However, their bake hardening response still need to be further improved to enhance their dent resistance. A novel thermo- mechanical treatment consisting of conventional pre-aging, pre-deformation and re-aging was developed to enhance the tensile properties and bake hardening increment of Al-Mg-Si-Cu alloys. In this work, the effect of pre-deformation on the precipitation behaviors of AlMg-Si-Cu alloy was studied by DSC, mechanical property measurement and TEM. The results show that, the GPzone dissolution rate decreases with increasing pre-deformation during the slow heating up process for the pre-aged alloy, the corresponding activation energies of 0, 5% and 15% pre-deformed alloy calculated by Avrami-JohnsonMehl method are 137.1, 189.5 and 141.3 k J/mol, respectively. If the pre- deformed alloys are directly bake hardened at 185 ℃ for 20 min, precipitation and bake hardening increment can be greatly improved by pre-deformation(the highest bake hardening increment is 160 MPa), but the bake hardening increment rate gradually decreases if the pre- deformation is above 10%. In addition, the GP zone dissolution rates of pre- deformed alloys after bake hardening treatment are much lower when the heat treatment temperatures are below one certain value, but if the treatment temperatures above it, the corresponding GP zone dissolution rates are higher than that of alloy without pre-deformation, finally, the activation energy changes from high value to low value even can be observed in the ln[(d Y/d T)f/f(Y)]-1/T curve. For the β″ precipitation in the alloys, with increasing pre-deformation, its activation energy gradually decreases, corresponding gradually increase of precipitation rate.

Body Structure Static-Dynamic Analysis and Optimization of a Commercial Vehicle

White body in the design process needs to meet the needs of a wide range of performance requirement. Adequate stiffness and modal are the basis to ensure the vehicle’s performance of vibration noise. Simultaneously, in order to reduce energy consumption and cost, the lightweight design of the white body has become the mainstream. In this paper, the optimization design is conducted for stiffness and modal of a commercial vehicle’s white body based on the theory of the finite element size sensitivity optimization design. Firstly, build the finite element model of a vehicle’s white body and analyze its stiffness and modal. Some changes were made to the car-body’s partial structure according to the distributing of strain energy achieved from above analysis, which improved the car-body’s dynamic and static performance initially. Secondly, choose panels needed to be optimized by reference to the density of strain energy and panels’ mass. Then, the car-body’s structure was optimized using panels’ thickness as design variables, stiffness and modal frequencies as constrains and minimizing weight of white car-body as objective. After the analysis of the result, modal separation was put forward to improve the quality of this finite element optimization design model. Finally, the car-body’s stiffness and mode nature entirely satisfied the requirements with car-body’s weight decreased.

Out of plane crushing and local stiffness determination of proposed foam filled sandwich panel for Korean Tilting Train eXpress – Numerical study

Abstract Weight saving has been the major concern of rolling stock engineers. Implementing lightweight materials makes it possible not only to save energy but also to increase allowable speed and service loads. Recently, sandwich panels have been used for structural material of the rolling stock. Korean Tilting Train eXpress (TTX) has hybrid body shell which reduced its weight by 39% in comparison with stainless steel body shell. The body shell was made of honeycomb sandwich panels with carbon fiber reinforced skins. This paper studies how great improvement one can achieve in energy absorption and impact strength from foam filling of TTX honeycomb sandwich panel. Among several types of polymeric foams, owing to its low density, stiffness, low water absorption, low heat conduction coefficient and relatively good mechanical strength, polyurethane foams (PU) are used as filler phase. Then crushing strength and local stiffness of the foam filled panel are obtained by mean of FE method. Based on analyses carried out, foam filling of honeycomb core causes many changes in structural behavior of TTX panel such as; increase its mean crushing strength and energy absorption capacity by 232%, and enhance its local stiffness up to 45%. These interesting advantages of foam filling only add about 2% to the car body weight. At the other hand, thinner body shell could be manufactures which gives more spacious car body.

Knowledge Discovery for Car-Body Weight Reduction with Multidisciplinary Design Optimization and Trade off Analysis

Multidisciplinary design optimization (MDO) using design of experiments (DoE) and response surface method (RSM) is one of the effective methods for reducing weight of car body structure. However, large amount of information obtained from the optimization makes the optimization itself not useful. This problem is caused by large number of variables of vehicle model. This paper proposes a trade-off analysis process using sensitivity analysis, multi-objective optimization, hierarchical cluster analysis and parallel coordinate plot for analyzing optimization information. As a result, it was clarified very important parts for reducing body weight. Accordingly, even the designers without the expert knowledge may easily be able to make a knowledge discovery for car-body weight reduction.