Blank Design Of Sheet Metal Parts Based On Inverse Approach

Blank design is important in sheet metal stamping forming process. It is the premise to obtain the blank shape of forming parts to analyze forming distortion degree, design technology as well as draft process specifications. Reasonable blank shape and size can obviously improve the inhomogeneous deformation of blank and fully exploit the metal forming performance. Among the methods of blank design, the finite elements Inverse Approach (IA) based on total strain theory, only considering the initial and final stages of the parts, makes IA method very fast and high-effective .Under some specific conditions, IA method can quickly calculate blank shape,final stress,strain,thickness change rate etc.In the paper, the basic theory of sheet forming is fully studied. The basic theory of IA and how to operate it are briefly introduced. Then the anisotropic constitutive relation under proportional loading condition and flat triangular membrane elements of constant thickness having three nodes are adapted. Assumptions are made regarding the actions of the tools (punch and die) on the sheet at the end of forming process, and then equivalent computation model of external nodal force is put forward and the related computer program is implemented.Typical rectangular and L-shape boxes are simulated by IA program. Then the results are compared with those simulated by incremental soft wares DYNAFORM and PAMSTAMP. The comparisons show that inverse approach, which can be used to evaluate the sheet metal forming process quickly and optimize the stamping technological parameters, is an effective approach for blank design. So it is a good choice to use this method in the initial stage of die design.Finally, the finite elements Inverse Approach based on the four-node isoparametric element is discussed and the finite element control equation is established in this paper. The design of the pre-process system based on four-node element and programs are finished.