Research On Crashworthiness And Structural Optimization Design Of Double-hat High Strength Steel Thin-walled Structures

In recent years,with the continuous growth of car ownership,safety,environmental protection and energy saving have become the focus of attention of the automotive industry.In order to realize the lightweight of automobile and improve the crash safety of automobile,high strength steel has become one of the main materials for automobile body parts selection,and it is a very competitive lightweight material.At present,the research on high strength steel thin-walled structure mainly focuses on structural optimization,mainly in order to improve the crashworthiness and lightweight of the structure,while the cost-performance analysis of the structure is relatively less.How to develop cost-effective products has been the primary goal of enterprises in different ways.Because of its lightweight and efficient energy absorption properties,aluminum foam has become a new lightweight material for automobiles.The hybrid structure of metal thin-walled structure and aluminum foam is widely used in the automotive industry due to its excellent crashworthiness and light weight.Therefore,the crashworthiness optimization design of foam filled thin-walled structures has become an important part of vehicle crashworthiness research.In view of the above problems,the double-hat high-strength steel thin-walled structure and aluminum foam filled double hat high strength steel thin-walled structure are studied in this paper.(1)Crashworthiness analysis of thin-walled double-hat high-strength steel structures.Firstly,a series of drop hammer tests were carried out on the double-hat high-strength steel thin-walled structure under axial and three-point bending impact.The test results show that the yield strength of the material has a significant effect on the crashworthiness of the structure.Secondly,the impact of three factors(wall thickness,material grade and impact velocity)on the crashworthiness of high strength steel double hat structure was investigated by using the finite element model.(2)Performance-price ratio analysis of double-hat high-strength steel thin-walled structure.Based on the results of finite element analysis,a proxy model of performance index and cost index(SEA,M_b,SEA/Cost and M_b/Cost)was established for the three design variables of yield strength,wall thickness and impact velocity.Through the analysis and comparison of the three-dimensional and two-dimensional isolines of crashworthiness and cost performance,the design method of balancing lightweight,crashworthiness and manufacturing cost is proposed,which has guiding significance for the engineering application of high strength steel materials.(3)Crashworthiness analysis of foam filled double hat high strength steel thin-walled structure.First,the establishment and verification of the finite element model of foam filling structure is carried out,and then the parameter analysis of Crashworthiness of two different foam filling structures is carried out.The results show that tube wall parameters and foam parameters will have a certain impact on Crashworthiness of structures in terms of Crashworthiness index and deformation mode.(4)Multi-objective optimization design of double hat thin-walled structure filled with aluminum foam.On the basis of parametric analysis,multi-objective optimization design of gradient density foam filled structure and uniform density foam filling structure with equal mass field was carried out based on tube wall parameters and foam parameters as design variables.The optimization results show that t he crashworthiness of gradient density foam filled structure under various conditions is improved compared with that of uniform density foam filled structure,which can also guide the engineering design of foam filled structure.