Research On Stamping Performance Of Variable Cross Section Thin Sheet

In this paper the stamping performance of variable cross section thin sheet (TWB and TRB) is researched by systematic.First, the base material of DC06 and DC03 and the variable cross section thin sheet are used for the tensile test, the cup testing and the cup-drawing testing and the SEM testing. In order to discover the formability of TWB in different welded line condition,FEM was used to simulate the formability of the equal thickness sheets and its TWB.①The tensile testing show that under a range of the welded line angle, the failure occurs across the weld line first. As the thickness difference increase, the failure occurs across the welded line has decreasing trend; The angle between the surface the failure and the weld line is about 90°, when the failure occurs across the weld line; The failure occurs across the thinner sheet when the angle is over certain degree. As the proportion of the thinner sheet increase, the formability of the TWB increasing. the tensile test also show that although the elongation of TRB reducing as increasing of the thickness difference, which still have better elongation, and the second rip may be happen when the thickness difference increase further.②The SEM show that the tensile fracture types of the TWB for the material of DC06 were all dimple under different angles; the size of the dimple increase as the angle increase, and the shape of dimple become from the equiaxed dimple to elliptic dimple, and become the equiaxed dimple finally.③The cup testing show: the IE increasing as the thickness increasing of the equal thickness sheets, and the IE of the TWB is less than the base material. The different thickness and the location of the welded line are the main influencing factors for the movement of the welded line.④The cup-drawing testing show: the existence of the welded line, which reduce the formability of the TWB. And the anisotropy was very clear around the welded line during the drawing of TWB. The deformation both of the base material is inhomogeneity during the forming, from the bottom center to port of the cup, the welded line first move to the thick sheet then to the thinner sheet. The cup-drawing test also show that ,as the thickness difference increase, the limited drawing ratio (LDR) of TRB first up then down, the minimum BHF has increasing trend and the Maximum Working Load has decreasing trend. The TWB and the TRB have the similar forming character, but the TRB has the better formability, the better forming quality and the wildly used.⑤The numeric simulation result show that the true welded line model based on the experiment is closer to the fact than the simple welded line model. Numeric simulation which can simulate the forming of the TWB, but the errors still exist especially in anisotropy of the main sheet and the welded line.