Study On Structure Analysis And Multi-objective Optimization Of BIW

The development cycle of automobile is shrinking constantly with the advancement of technology. Now, it is the renewal of automotive body that brings the renewal of automotive product. Therefore, the competitive position of auto-corporations is directly subject to the capability of developing auto-body. As the stressed member of the whole, BIW must be designed with sufficient and favorable performance to meet the pertinent requirements. The problems coming out in the structural design phase is subtle and undetectable, and the problems might adversely affect the upcoming manufacture or testing phase. Thus, in order to save more resources, it is an efficient way to analyze and optimize the structure of auto-boy early in the design period. The application of finite element method(FEM) could evaluate the performance of auto-body before making the real prototype and modify the structure in advance before greater loss.The main content of this thesis is as follows:⑴Finite element method and the basic theory of its application on BIW have been illustrated, providing the general process of building a FEM model, and an entire BIW FEM model for a particular car was built. Static load and constraint conditions were simulated to analyse the BIW to make sure that the performance of BIW for assembly and use requirement is qualified.⑵Fatigue load spectrum and common fatigue damage methods have been illustrated. B-level road model was created by Matlab/Simulink. BIW combined with wheels and suspension model were simulated drive on B-level road with 60 km/h speed. Fatigue life prediction of the car is carded out based on transient analysis result.The BIW fatigue reliability was confirmed.⑶FEM analysis combined with Multi-objective Optimization method was used to improve the first order frequency of BIW. Mathematic model was built by response surface method to replace FEM model and NSGA-II was used to get non-dominated solutions. During the optimization plates with high relative sensitivity was used as design variables. The first natural frequency was optimized and the mass of BIW was under control.BIW was optimizad with appropriate variables based on analysis by Finite-element Method. This thesis is the application of CAE study, the result provided a valuable consult for further study on BIW design and optimization.