Finite Element Analysis And Optimization Research Of Commercial Vehicle Subframe

With the improvement of people’s living standards, the automotive is demanded moreand more comfortable. Commercial vehicle subframe is an important component inchassis assembly, and it plays an important role in the barrier from the road, powertrainnoise and vibration. There are many parts are installed on the subframe, so its strength andstiffness is particularly important in the chassis design. In this paper, multi-body dynamicssimulation, static and dynamic finite element analysis and structural optimization designof the CAE technology are applied to a commercial vehicle subframe design, and forminga complete CAE analysis system, providing the reference and learn for the similarautomotive parts design.In this paper, based on multi-body dynamics theory and using ADAMS software toestablish the front suspension dynamics and powertrain mounting system simulationmodel, and the hard points load on the sub-frame and mounting hard points condition loadwere extracted after debugging and validating the model, these data were as the input forfinite element strength analysis and optimal design.The finite element model of thesubframe was established by Hypermesh, and ten common conditions of subframe andtwenty eight conditions of mounting bracket were analyzed by ABAQUS, the stressdistribution and displacement of the subframe and mounting bracket were got, and somemodify proposals were presented. To verify the subframe dynamic performance, itsFreedom mode and constrained mode were analyzed, the natural frequency and vibrationcharacteristics were got, combined with the engine idling frequency, the dynamic responsecharacteristics was evaluated. According to the results of static analysis, selecting thecross-section dimensions were as design variables, the stress was as the constraint, thetotal weight was the target function.After optimized, the cross-section thickness dimensionof mounting bracket and subframe were got. The strength and stiffness were analyzedagain and the results show the maximum stress conditions were significantly reduced thanbefore optimization, the stress distribution is more reasonable, and the nature frequencyalso met requirements, which it showed the optimization design were reasonable andcorrect. Finally, using fatigue software to analyze the before and after optimizationsubframe fatigue life in the lateral load, longitudinal load and vertical load conditions, andsubframe was broken and the life is102329times in the longitudinal load condition, thelife of other conditions met the requirements. According to the subframe bench fatigue testresults, the subframe was broken in12145times in the longitudinal load condition, the results with the experimental results is a difference of8.75%. At last, Again analyzed thesubframe life for three conditions and the results showed the fatigue life of subframe arebetter than before optimization, and met the test requirements, it indicated that theoptimization method is correct, feasible and effective.Through the road test, there was nofracture on the subframe, the results show the subframe met the design requirements.These study were done for an automobile subframe in this paper, using computer-aidedengineering technology, based on the finite element basic theory, a number of largegeneral-purpose software’s interactive applications, completing subframe stiffness、strength analysis and optimization design. While these researches method, thoughts andthe accumulated analysis data is very valuable.And it provides some references andguidances for analysis of the same type of vehicle or the machinery structural.