Study Of Formability Of Talor-Welded Blanks Used In Cars

Considering the requirements of future automotive in environmental protection and safety, structure optimizing and weight reducing of body-in-white, besides to the improvement of engine capability and aerodynamics character, has become an important goal of automotive manufacturing industry nowadays.The technique of laser welding blank is to use laser to weld up the tailors with different thickness or strength or surface coating and then press the tailor-welded blank (TWB) to the form as designed. The technique could provide the best combination of formability and strength to the blanks used in complex body of cars. In the last 20 years and in American and European automotive industry such as Volkswagen and General Motors, TWB has been widely used and the related techniques such as laser welding and forming have also been researched and developed. However, the product application and technique research of TWB in China is not enough. Facing the violent competing environment of international automotive industry, It is very significant for us do in-depth research to the formability of localized TWB.The test method for both parent tailor and welding of TWB mainly include cupping test, tensile test and forming limit test. Cupping test is the main testing method for TWB suppliers and OEMs to control the quality of welding seam. Tensile test is the basic method to test mechanical property such as yield stress, tensile limit and yield ratio, etc. Through the tensile test to parent tailors and different welding positions, basic mechanical property of total TWB could be acquired. As to the complex body part that is hard to form, forming limit diagram (FLD) is often used to describe the part formability. FLD is the most simple and straight way to evaluate the formability of metal sheet, a quantitative description of sheet formability, an effective tool to solve the problems of pressing and a criterion of forming technics. With the development of FEA technique recently, FLD has been used more and more widely as the criterion for wrinkle and crack in simulation.