Research On Drawing Law For Cone-box Shaped Parts Of Tailor Welded Blanks

In the modern automotive industry, due to the need for environmental protection and energy-saving, lightweight has become a general trend of automobile development. As one of the key technologies to realize lightweight of automobiles, the forming technology of tailor-welded blanks(TWBs) has been widely used in the automotive industry. However, due to the presence of weld line and the strength difference between the materials on both sides of the weld line, some problems ofen arise in the deep drawing of TWBs, such as rupture, wrinkling and weld-line movement. These defects limit TWBs to a wide range of applications, further study on the deep drawing process of TWBs is required. In actual production, the shape of workpiece is generally irregular and complex, therefore, the study on deep drawing tecnology for box-shaped parts of TWBs is of great significance in improving the forming stability of TWBs.In this paper, a cone-box shaped part of TWBs is taken for example. Considering the defects such as rupture, wrinkling and weld-line movement, the effect of various factors such as blank holder force(BHF), thickness ratio, and friction coefficient on the deep drawing of TWBs is analysed by using finite element method(FEM). In addition, based on the theoretical research of deep drawing for box-shaped parts, the stress and strain distribution in main deformation area for cone-box shaped parts of TWBs is discussed by theoretical method.In order to minimize the weld-line movement under given drawing depth, an optimal control scheme of BHF is put forward based on the effect of BHF on deep drawing for cone-box shaped parts of TWBs, which is of positive significance on BHF prediction in the intelligent deep drawing. Analyzing the effect of various factors on deep drawing will be helpful to deeply understanding the forming mechanism and guiding actual production. Moreover, by studing the thin part and thick part separately, the theoretical solutions of sress and strain in main deformation area for cone-box shaped parts of TWBs have been obtained, and the analytic expression of weld-line movement is deduced. According to the error between simulation results and theoretical results, a correction method is proposed, that is, introducing BHF ratio and thickness ratio into the theoretical analysis, which will lay a foundation for further theoretical research.