No abstract

This study deals with the multi-objective lightweight optimization of the front end structure of an automobile body, as the main assembly to withstand impact force and protect occupants from injuries in frontal collision, based on entropy-based grey relational analysis (EGRA). First, basic noise, vibration, and harshness (NVH) models of the automobile body and crashworthiness models of the vehicle are established and then validated by corresponding actual experiments; hence the lightweight controlling quotas are extracted. Next, the contribution analysis method determines the final parts for lightweight optimization, for which both continuous thickness variables and discrete material variables are simultaneously taken into account. Subsequently, design of experiment (DoE) using the optimal Latin hypercube sampling (OLHS) method is carried out, considering the total mass and the torsional stiffness of the automobile body, the maximum intrusion deformation on the firewall, the maximum impact acceleration at lower end of the B-pillar, and the total material cost of the selected optimization parts as five competing optimization objectives. After that, the optimal combination of thickness and material parameters of the optimization parts is determined using EGRA and confirmed by technique for order preference by similarity to ideal solution (TOPSIS). Finally, a comparison between the original design and the post-lightweight design, namely the optimized design, further confirms the effectiveness of the lightweight optimization. According to the outcomes, the automobile body is lightweight optimized with a mass decrease of 4.98 kg on the basis of well guaranteeing other relevant mechanical performance. Accordingly, the EGRA could be well employed to the multi-objective lightweight optimization of the automobile body.

Lightweight optimization and design on body in white (BIW) has a significant effect on reducing emissions, fuel consumption, and protecting the environment. Much lightweight study on complete BIW and single BIW parts has been done in recent years. However, the lightweight study of sub-modules is difficult for considering the complete BIW performances. The efficiency of sub-module lightweight optimization based on complete BIW is not high. A new method is proposed to conduct frontal sub-module lightweight optimization. Firstly, the implicit parametric frontal BIW structure is constructed by SFE-CONCEPT software. Then, the coupling BIW model is constructed by combining the above frontal BIW structure and rear finite element structure. The shape and thickness variables are extracted from the frontal BIW structure, and the performance of complete BIW can be analyzed. The efficiency of constructing BIW and the complete performances are all considered by the new method. In addition, a modular method is adopted to analyze performance. It can achieve the concept of ''analysis leads design'' to conduct lightweight optimization and design for frontal structure by combining with ISIGHT software. After lightweight optimization and design of BIW frontal structure, the weight is reduced by 4.91 kg, which is as much as 5.70%. The performances have little change; the improved maximum performance is 3.32%, and the reduced maximum performance is 1.81%.

An integrated optimization method that comprehensively considers draping factors such as fiber reorientations and cutting of layers is proposed for designing CFRP B-pillar reinforcement with a variable thickness. A laminate parameterization scheme, the local shared layer parameterization scheme (LSL-PS), is developed to parameterize the physical composition of laminates with variable-thickness. Kinematic draping simulations and preform designs are introduced to evaluate fiber reorientations and eliminate manufacturing defects. The optimization design of the B-pillar reinforcement is integrated with a LSL-PS, draping-simulation and preform-design, a RBF surrogate model and GA. At the same time, a comparative optimization without the consideration of draping factors is performed in parallel. The comparison results show that considering draping not only helps designers eliminate manufacturing defects but also helps to obtain a further weight reduction of 13.33% because fiber reorientations are fully utilized to improve the structural performance.

Body panels have a direct influence on the static and dynamic stiffness of the body-in-white. With the introduction of CFRP in automotive body, these panels have ushered in the potential of being designed with variable-stiffness. However, due to the inherent complexity of variable-stiffness design and the need to integrate all panels to account for their interaction on BIW, the related design issue has not been solved. This paper reports a design method to achieve the successive optimization of the thickness distribution and stacking sequence for body panels, as well as ensure basic manufacturing and blending requirements of design results. This method was applied to the virtual design of the roof, floor, outer and inner side panels of a body-in-white. Compared with original constant-stiffness CFRP components, a 16.4% weight reduction was attained, the torsional and bending stiffness, first-order torsional and bending frequencies were enhanced by 5.0%, 10.9%, 4.7%, and 7%, respectively.