Research On Crashworthiness For Energy Absorbing Structures Of Car Body Based On TRB Technology And Bionic Design

In recent years,the Chinese government has issued a series of automotive industry adjustment and revitalization plans,which greatly support the research and development of independent brands and new energy vehicles.Among them,the future of new energy vehicles will be the main growth point of Chinese automotive market,and the "power battery life" and "increased weight caused by battery and motor" will be the technical difficulties.Lightweight,as a research field closely related to the above two issues,has become the key whether an independent brand can master the core technology.It is an effective way to improve the product performance and control the cost to put forward a reasonable structure optimization strategy by synergistic study of lightweight and other performance targets of automotive components(such as high stiffness,high crashworthiness,etc.).Therefore,multi-objective optimization design for lightweight and crashworthiness of structures has become one of the important basic research topics in the field of automotive industry.This paper is supported by the National Natural Science Foundation of China,Science and Technology Development Plan of Jilin Province,Science and technology Research in 13 th Five-Year of the Education Department of Jilin Province and the corporation with China FAW Group Co.,Ltd.In this paper,TRB technology,bionics and multi-objective optimization theories have been studied.Then based on the flexible rolling TRB technology and bionic theories inspired by cattail and bamboo,the optimal designs of absorbing structures for car body have been proposed,which satisfy with the impact safety requirements of a A-Class vehicle and meet the objects of lightweight and high energy absorption.The main work can be concluded as follows.(1)Based on the analysis of the characteristics,manufacturing process and basic mechanical properties of TRB,a modeling method for solving the graded thickness properties and graded mechanical properties of TRB is proposed for the structural design of the energy absorbing box based on TRB technology.The mathematical model of multi-objective optimization problem based on surrogate model is deduced by considering the distribution of thickness,weight and energy absorption of the crash box.Considering that the vehicle structure optimization problem has the characteristics of multi-objects,large scales and construction by surrogate models,an improved multi-objective optimization algorithm is proposed.The optimal design of the TRB crash box structure is obtained by this algorithm,which can replace the original equal-thickness crash box.The weight has been reduced by about 7.4% significantly.The samples are successfully trial-manufactured.Sufficient and symmetric folds appear during the quasi-static collapse of the samples.The order of folds is coincident with distribution of thickness,and the deformation process is stable.The feasibility and effectiveness of the design have been confirmed.The research results can provide a new solution for the popularization and application of TRB technology in the field of lightweight design.(2)Considering the lightweight requirement of dashboard cross beam and the rolling process requirement of TRB,plans of five segments and three segments for TRB dashboard cross beam are proposed to replace the original equal thickness structure.By comparing the performance parameters of these plans under low order mode,vertical bump,brake force and PAB expand conditions,it is verified that the TRB technology can highly reduce the weight about 8%~13% as well as meeting the performance of dashboard cross beam.Designers can select the appropriate TRB plans according to the concerned performances or lightweight target.(3)Two bionic bumper designs(B-CB&B and B-B)are proposed according to the structural forms and load transfer characteristics of cattail and bamboo,which can comprehensively measure the performance impact caused by the structural change of different components,as well as to grasp the performance change trend caused by the different structural combination.Comparing the collision performance and deformation characteristics of the two bionic structures with the original structure under the two simulation conditions of the frontal 100% overlapping rigid wall collision test and single side drop test,the results show that the two bionic designs can meet the requirements of manufacture technology and lightweight.The collision performance of the B-CB&B design is optimal.In this design,the weight is reduced by 44% and SEA is increased by 83%,as well as the deformation mode is reasonable and stable.Moreover,and the crashworthiness of B-B design is also better than the original structure,with the weight reduced by 7.4% and SEA increased by 15%.(4)For the B-CB&B bionic bumper structure proposed in this paper,the nonlinear optimization design is carried out.The optimization problem based on surrogate model is constructed,with the peak section force and SEA as evaluation targets and the thickness of components as design variables.The multi-objective cuckoo search algorithm is used to solve the problem.The optimal parameters have to be round-off.Compared with the original structure,the peak section force of the optimal structure is reduced by 57.5% and the SEA is increased by 15%,which shows that the optimization is effective.In addition,through the analysis of the crashing deformation process of the optimal structure,it can be seen that the whole energy absorption is improved,which means that the crashworthiness of frontal 100% overlapping rigid wall collision has been improved.The proposed method and theory can be applied to practical engineering fields involving nonlinear collision optimization problems.