Research On Body-in-white Lightweight Based On Multidisciplinary Design Optimization

Vehicle lightweight is a well-known strategy to address growing concerns aboutgreenhouse gas emissions, improve fuel economy and save energy. Since the body structurepossesses about40%weight of full vehicle, the body structure s lightweight plays a quiteimportant role in weight reduction of full vehilce. Body structure lightweight design is asystematical project which is involved with crashworthiness, stiffness, eigenmode and noise,vibration, harshness (NVH) performance. The surrogate based design optimization isconsidered as one of the efficient approaches to dealing with complicated engineeringproblems. Based on one of the homemade car s body in white, the dissertation systematicallyand thoroughly studies on the method of multi-disciplinary, multi-objective opimization onbody-in-white by considering the parameters of thickness, mechanical performance ofmaterial which have influence on body in white stiffness, eigenmode and vehicle scrashworthiness. The main research work are listed as follows:1. Research on modelling a full vehicle finite element model. It is very important andindispensable to have a finite element model for the full vehicle in conept design phase ofdeveloping a car, which not only can simulate vehicle s mechanical performance accuratelybut also its computational time is acceptable. Based on module modelling regulation, thedissertation systematically expatiates on how to build a full vehicle finite element model bylooking into details. As a consequence, this approach has its engineering practicability.2. The body-in-white and full vehicle crash finite element model have been created.And the calculation of static bending, torsion stiffness, eigenmode for body-in-white andside impact calculation for full vehicle have been performed. Meanwhile, test of staticstiffness and eigenmode, test of side impact have been conducted. Through the validationbetween simulation and test, the accurateness of finite element model has been validated.3. Taking the product feasibility into account, twenty one parts thickness and elevenkinds of material from body-in-white are selected as design variables and the Design of Experiments matrix has been created. Samples of stiffness, eigenmode and side impact ofbody-in-white are taken by simulation. The relativity and contributive ratio of designvariables to stiffness, eigenmode and side impact of body-in-white is analyzed in order toprovide technical information for later optimization of body-in-white.4. By using of RSM, RBF, Kriging approaches, the approximate model for stiffness,eigenmode and side impact are created respectively. And error of all approximate model hasbeen analyzed by analyzing the parameters of body-in-white stiffness, intrusion velocity anddisplacement of side impact. Considering the accurateness from the engineering point ofview, the RBF approximate model for stiffness and the RSM approximate model for sideimpact are finally confirmed.5. Research on body-in-white lightweight on multidisciplinary design optimization.Based on the approximate model of stiffness and side impact, the dissertation takes thebody-in-white lightweight as objective, and performs the multi-disciplinary andmulti-objective optimization on body-in-white including stiffness, eigenmode andcrashworthiness. The target of weight reduction by15.7kilogramms has been achieved. Atthe same time, one piece of vehicle prototype after optimization has been produced in orderto validate the approach which is studied in this dissertation.