Research On Formability Test And Application Of High-Strength Laser Welded Blanks

Laser-welding and high-strength steel, hydro-forming are recommended as the three important technologies for ultra-light steel auto body(ULSAB) project, which have many advantages, such as reduction of weight, improvement of safety, saving material. They are one of the development trends on automotive material technology. The formability of High-strength laser tailor welded blanks (TWBs) gradually become the hot issue of research. So it is critical to investigate the formability of high-strength laser TWBs. Currently it is no standard for the laser TWBs formability tests, so it is necessary to investigate high-strength laser TWBs formability.There are lots of factors of identifying sheet metal forming performance and test methods, while both basically forming test and forming simulation test are the most basic and commonly employed. In this paper, the tensile test and cupping test of high-strength laser TWBs were investigated, which are used to evaluate the formability of high-strength laser TWBs.In tensile test, tensile properties of tailor-welded blanks with transversal weld and longitudinal weld were investigated. The stress-strain relationship between TWBs combined by two various thickness ratios specimens with the transversal weld and the base material, and the deformation of TWBs were studied. By varying the width of TWBs with longitude weld, the effects of different sizes of TWBs on the mechanical properties and the mechanical properties of weld were acquired.In the cupping test, through reforming the structure of blank holder and adjusting shim to meet the various thickness ratios blanks in the test, buckling value was accurately acquired. Compared with the base metal and TWBs of two thickness ratios, the effects of various thickness ratios on bulging formability of TWBs were studied.High-strength laser TWBs formability was investigated, combining the research results above. By using finite element analysis software DYNAFORM, plain steel and high-strength steel box were numerically simulated. Compared the various properties of two materials, it provide an important reference to optimize formability of the high-strength TWBs.Tests above evaluated well formability of high-strength laser TWBs and its application are researched. Meanwhile, basic mechanical properties and cupping test value were measured, and it provide the important standard for material selection, weld layout and numerical simulation of TWBs.