Study On Crashworthiness Of Thin-walled Beams With Tailored Welded Blanks And Foam-filled Materials

With the development of society, the car has become the most important transportation for human being. As rapid augment of car ownership and continuous increasing of vehicle speed there are more traffic accident happened thus lead to a large number of casualties. So there is a urgent need to improve vehicle safety standard, one of important way to enhance the car safety is to strengthen energy absorbing performance of automotive's front deformation region. The front longitudinal beam, which is the momentous energy absorbing structure of car's front cabin, is the key to improve the energy absorption performance of the car. The front longitudinal beam usually consist of thin-walled beam structures. Thin-walled structures have been extensively used as energy absorbers due to their ideal deformation pattern, high energy absorbing capacity, light weight and low price. So,this paper mainly study on the crashworthiness of thin-walled beams.Firstly, when study on the thin-walled beams' crash performance, we always encounter the situation that there is conflict between some evaluation indexes when assess the performance of samples thus make it is difficult to distinguish which sample should be selected. In researching the crashworthiness of Tailored-Welded Blanks(TWBs), we can't judge the quality of samples by direct observation when comes to kinds of design variables and under various loading conditions. To solve this problem, the complex proportional assessment method(COPRAS) is quoted. Generate the initial decision-making matrix, which mapping the alternatives to the selection criteria and identify the weight of each criterion according to the importance of the selection criteria, eventually obtain the comprehensive evaluation of Tailored-Welded Blanks' crashworthiness. The results show that the complex proportional assessment method can evaluate the crashworthiness of samples with kinds of design variables efficiently and objectively.Secondly, a FE model of a box beam in sled crash test have been built,the accuracy of the model is verified by a collision test under high speed use TWBs. The crash performance of TWBs with different materials and thickness under two kinds of loading conditions which name axial and oblique impact is studied, then use the complex proportional assessment method evaluate their comprehensive crash performance. The research results show that TWBs with reasonable materials and thickness can improve the crashworthiness of thin-walled beams.Finally, Studying on rushing of foam-filled thin-walled tubes. Use the thickness and cross section's size of the tubes or the density of aluminum foam as design variables, obtain pareto front of the SEA and PCF as objective functions which under axial and oblique impact loadings. The results show that aluminum foam can improve the crashworthiness of thin-walled tubes. Especially, the aluminum foam-filled structures have obvious advantages than that of the empty ones under some collision angle.For the purpose of improve the crash performance of thin-walled beams, this paper use TWBs Technology and foamed metal structure to study the crashworthiness of thin-walled beams. Through the study of this paper we known that it is a good way to improve the crashworthiness of thin-walled beams by combining TWBs technology and foamed metal structure. It is confirmed that this two methods metioned above is of great significance and engineering application value.