Axial Crushing Theoretical Research And Structural Optimization Of Hat-section Thin-walled Beam

The crashworthiness of thin-walled energy absorbing structure such as front side member largely affected the vehicle passive safety performance. Because of the complexity of the hat-section beam structure in practical engineeri ng, the material, wall thickness, circumference between components were usually different. And in order to achieve performance requirements such as security, stiffness, strength, the beam structure was usually contain several hat-section structure. It’s very hard for the traditional theory to predict the mean crushing force of these beams. Aiming at the shortcoming of the traditional methods, basing on the superfolding element, the general hat-section beam axial crushing theory had been put forward to accurately predict the mean crushing force of different material and thickness hat-section thin-walled beam.The deformation mode of thin-walled structure directly determined the energy absorption effectiveness. And the deformation mode was usually divided into two kinds, the axial crushing and bending. To get higher energy absorption efficiency, it should to ensure the structure get a stable axial crushing deformation. The article selected the most asymmetric structure, the top-hat beam, to study the structure and spot-weld a total of four factors, and analyzed the deformation characteristics of different cross-section structure. Then had a research of deformation mechanism, and summed up the range for the reasonable design to ensure the beam have a stable deformation.In axial crushing prediction theory, the beam cross-section circumference was researched as one variable. But through the experiment and simulation results, it had showed that the different geometric cross section of the same circumference beam ha s different deformation mode and energy absorption efficiency. Aiming at the problem, in order to get the best cross section design of same circumference beam, the surrogate model and multi-objective optimization method had been used to optimize the geometric parameters. Selected a car front side member as the study object, and the cross section width height ratio, flange width were chosen as design variables, and the mean crushing force and peak force were chosen as response, to get the DOE project based on Optimal Latin Hypercube Samples method, then constructed the surrogate model according to the simulation result. On the basis of surrogate model, using the multi-objective genetic algorithm to optimize the wide high ratio and flange length, finally get the best design of cross section.Applied the optimal design result to the vehicle front member, and compare the simulation result of original model and modified model. It was founded that the key performance target such as front side member crushing mode, front clapboard intrusion, body acceleration had a certain improvement, which indicated that the optimizing method using in the article has a guiding significance.