Research On Front Sub-frame Of The SUV Vehicle

Sub-frame is an important component in chassis assembly which plays a role in vehicle's axle supporting and vibration isolation.The use of sub-frame improved the comfort and handling of a vehicle,simplified the model design and benefit vehicle modular.In this paper,the static analysis,modal analysis and size optimization design were operated by HyperMesh,OptiStruct,HyperStudy respectively based on finite element theory,the linear static analysis theory,theory of nonlinear static analysis,modal analysis theory and the theory of multi-objective optimization which has some practical value in engineering.This paper takes the front sub-frame of a SUV to study.The 3D model of the front sub-frame is established in CATIA,then use HyperMesh to create the sub-frame's finite element model.The static analysis of front sub-frame contains linear static analysis under ordinary conditions and non-linear static analysis under limit conditions.The result showed that the maximum stress of sub-frame under ordinary conditions is less than the yield limit and the maximum stress of sub-frame under limit conditions is less than tensile strength limit,so that is could meet the requirements.The former 4 modes of the front sub-frame was calculated in the modal analysis,the result shows that front sub-frame is impossible to cause dynamic interference with road and engine and the former 4 modes are better than standard car's former 4 modes.In this paper,the static and modal analyzing result shows that it is necessary to optimize the size of sub-frame in order to develop the potential of materials.At the last of the paper,size optimization based on multi-objective genetic algorithm for front sub-frame's lightweight has been proposed by HyperStudy.Six size variables with high effects have been screen out from nine size variables through main effect analysis.Constraint conditions been set to the maximum stress of sub-frame under two ordinary conditions is less than the yield limit.Optimization's objective been set to the minimum of mass and the maximum of free mode's first mode.With size optimization of finite element software,8.47 percent weight was decreases compared to the current front sub-frame.The result of static analysis and modal analysis after optimization shows that all parameters meet the specification.