Study On Strength Analysis And Optimization Of Minivan-Body Structure Shanghai Jiao Tong University

With the development of modern industry of China, there are more ways of becoming rich in rural areas. The minivan has entered into more and more families to help them build a fortune. On the one hand, users of the minivan often overload their vehicles and drive them in poor roads; on the other hand, customers of the minivan are basically more sensitive to its price. To meet both of cost and reliability targets, it is critical to design the structure of the minivan scientifically. The enough strength of the body is the most important to make a minivan reliable and safe. At present, it has become a consensus to make full use of CAE to predict the performance of the car and find the structure defects in the stage of design.The current studies about the minivan are concentrated on key part and subsystem rather than the body. In order to research and optimize the body structure of the minivan further, this paper makes the modal, stiffness and strength analysis based on FEA combined with multi-body dynamics simulation and experimental method of load spectrum acquisition.The main contents are as following:1. Building the FEA model of the BIW by using batchmesh function in Hypermesh software. To get an accurate FEA model quickly, we need to study the simplified means of the 3D model, make use of the mature and certified meshing parameters, and adopt the block modeling methods. Then the model and stiffness analysis are performed to study the structure of the BIW. The results show that the 1st modal frequency of BIW and its stiffness can not meet the requirement.2. Performing the static strength analysis under five extreme conditions by using inertia relief calculation. The rigid-flexible coupling model of the whole car is established in MSC.Adams to take account of the influences of the chassis and the body. The structure of the chassis effects the force transmission to BIW. The model with a flexible body can get the stress distribution more accuracy than with a rigid body. The peak forces and moments of the body installation points are calculated by simulating five extreme conditions in ADAMS and then are imported into MSC.Nastran. The stress distribution of the BIW is obtained in Nastran and shows that there are some risk areas with high stress.3. Predicting the fatigue life of the BIW by taking the local strain analysis. The load spectrum of the user roads, the stress distribution of BIW under unit load and the material properties are three major inputs to predict the fatigue life in MSC.FATIGUE. The parts with short life in prediction are basically consistent to the actual cracking site.4. Optimizing the body structure for every risk area in the fatigue life prediction. The structure improvements are introduced on the basis of FEA methods and the specific analysis about the structures. And the effectiveness of the optimization program is validated by the FEA.In this paper, FEA methods and the related software are used to systematically study the structure of a minivan-body, identify and optimize the areas with insufficient structural strength. The comparison between the simulation results and the actual statements shows that the analysis is reasonable. The process used and the data obtained in this paper has provided theoretical support and practical reference for the design and optimization of such minivans.