Structure Dynamic Improvement Of Body In White Based On Auto Component Mode Synthesis

The dynamic improvement of vehicle body structure is an important link inautomobile design. Efficient numerical method is helpful to reduce the computationtime and design cost in the process of structure improvement. In this paper, AutoComponent Mode Synthesis method was applied to structure dynamic improvement ofwhite body based on a domestic car. The main research contents are as follows:Based on the interpretation of source program of ACMS module in Nastran, theformula of ACMS was derived, and the concrete method of ACMS was mastered. Thedirect computation of the higher order matrix was avoided by using internal modaltruncation for reduced-order system matrix. The multi-level substructure was used, andthe dimension of final system matrix was reduced through the interface mode truncationin the process of various layers of sub-structure assembly step by step, and solvingefficiency was greatly improved.The finite element model of body in white was built, and static stiffness and modalanalysis were used to verify the correctness of the structural model. The accuracy andefficiency between the ACMS method and traditional FEA methods were comparedbased on the body model, the results show that the ACMS method has higher solutionefficiency than the traditional FEA method under the premise of ensuring the accuracy.NVH performance was calculated by using the ACMS method, and the results show thatvibration and noise performance of body structure need to be improved.Structure of body in white was dynamically improved based on ACMS. Thethickness of body structure was taken as the research object, and the sensitivity ofvibration response was analyzed to determine the design variables. The optimizationobjective and state variables were determined according to vibration response analysisof body structure, then, the optimization model was established. Optimization methodcombined with approximate model of first-order response surface was used to optimizethe vibration response of body in white.The improved body in white was verified, and the efficiency between the ACMSmethod and the traditional FEA method was compared based on the optimizationprocess. The results showed that the vibration response of objective function measuringpoint decreased1.2dB, interior noise improved, and the first order torsional mode andstatic stiffness increased. Computational efficiency was improved by7.9times using ACMS than the traditional FEA method for body structural optimization. Finally, noisereduction measures were used to improve the response of interior low frequency noise,and the results showed that paved damping material at the firewall have a good noisereduction effect.