Multi-objective Optimization Of Bumper Beam Section Based On SiPESC Software

In recent years, with the rapid development of economy, the number of vehicles increases greatly, traffic accidents in China have presented a rising trend. Hence, automotive security has attracted more attentions than ever before. The improvement of automotive passive safety performance during crash has become significant in automotive safety design. At the same time, efforts should be made to achieve the lightweight of body in white (BIW), then the energy crisis may be relieved. And in this respect, the extensive use of high strength steel sheet, makes it show great advantages to improve automobile safety performance and achieve lightweight body.For vehicle lightweight, the original roll formed double bumper beams with conventional steel sheet are replaced by the new hot stamped single bumper beam with high strength steel sheet. On the premise of the blank formability, several geometric surfaces of the bumper single beam are carried out in the design process and a suitable geometric surface of the bumper beam with good formability is selected. While maintaining the crashworthiness, the wall thickness of the new single bumper beam is compared and analyzed and a suitable wall thickness is selected, which makes crashworthiness of the single beam better than the crashworthiness of the original double beams. In order to reduce the computation time and obtain a higher optimization efficiency, maximum energy absorption, peak acceleration and material cost are used as integration objective, seven factors of the bumper beam section are studied. Some factors that impact the effect of the integration objective are analyzed through the use of derivation method of minimum subordinative degree and extreme difference analysis, four factors which have great influence on the integration objective are selected out in order to reduce the complexity of the test and improve computational efficiency.The selected four factors of the bumper beam section are considered as design variables. The maximum energy absorption, peak acceleration of the crash simulation and material cost are used as optimization objective. The maximum thinning rate and maximum principal strain of dangerous point of the hot forming simulation are set as constraints. The multi-objective optimization of the beam section is performed by the orthogonal design method, radial basis function and NSGA-Ⅱ genetic algorithm of the SiPESC software. And an appropriate group of solution which has better performance than the model of before optimization is selected from the Pareto-optimal solutions for hot forming simulation and crash simulation analysis. The results show that the optimized single bumper beam with high strength steel sheet not only meet the requirements of blank formability, but also improve its crashworthiness and reduce the material cost distinctively.Multi-objective optimization problem of bumper beam section is resolved by the SiPESC software successfully. The predicted values of the radial basis function are in good agreed with the hot forming simulation values, which indicate the validity of the results of the radial basis function. The performance comparison of the original model and models of before and after optimization illustrative MQ-based radial basis function and NSGA-Ⅱ genetic algorithm of the SiPESC software can effectively solve such multi-objective optimization problem. The multi-objective optimization methods and conclusions of this study have important guiding significance on the design and improvement of automotive bumper beam.