Research On The Test Fixture For Simulating The Stiffness Of The Connecting Point Between A Front Subframe And Body-in-white

Sub-frame,one of the most critical parts of chassis,which has an important effect on the driving safety and comfort of the vehicle.The durability test of the parts during the automobile development process is gradually carried out from actual road test to proving ground test and indoor bench test.Compared with the actual road test and proving ground test,indoor bench test can significantly shorten the development cycle,reduce test costs,drawing more and more attention.With the development of computer technology,people gradually combine proving ground test,indoor bench test and computer-aided engineering(CAE)together to study the performance of auto parts.The development of indoor test bench has been the hotspot of people's research.Based on the project of a well-known joint venture in China,The test fixture for simulating the stiffness of the connecting point between a front subframe and Bodyin-white is studied in this paper by means of finite element simulation analysis and experiment.The main contents are as follows:(1)The establishment of finite element model of subframe and body-in-white.According to the CATIA model of sub-frame and body-in-white provided by the company,the finite element model of sub-frame and body-in-white is established,laying the foundation for the later simulation analysis and the test fixture optimization.(2)Static strength analysis of subframe finite element model.In order to compare the influence of the fixture and the rubber suspension on the stress distribution on the subframe finite element model,The static analysis of the subframe was carried out in four cases according to the actual force of the subframe in the vehicle,the simulation results show that the dangerous points on the subframe,and the accuracy of the finite element model of the subframe is verified.And provides a reference for strain gluing position of the test of simulating the stiffness of the connecting point between subframe and body-in-white.The results show that the influence of rubber suspension on the distribution of stress on the subframe under static loading is small,and the stiffness of the connecting point between subframe and body-in-white has a great influence on the stress distribution on the subframe.(3)The test of simulating the stiffness of the connecting point between subframe and body-in-white and model verification were carried out.In order to validate the impact of rubber suspension on the stress distribution of the subframe,a static loading test was carried out in four ways on the sub-frame in which the nylon bushing and the rubber bushing was respectively installed.The stress of the key points on the subframe was obtained,which providing the optimization target for the design of the test fixture,Based on the analysis of the test results,it is proved that the effect of rubber suspension on the distribution of stress on the subframe under static loading is small.The static simulation analysis of the subframe and body-in-white model is carried out according to the loading conditions of the test.The test results are basically the same as the simulation results,which verify the accuracy of the model.(4)Optimization on the test fixture for simulating the stiffness of the connecting point between a front subframe and body-in-white.The stress values of the three key points on the subframe are chosen as the optimization target,the test fixture size is used as an optimization variable,the mass of subframe and the test fixture as constraint.The multi-objective optimization of the test fixture is carried out by the two methods of adaptive surface response and global response surface method.A set of easy-to-handle test fixture sizes are selected as a final optimization result.