Optimum path forming technique for sheet metal and its realization in multi-point forming

A technique to shape sheet metal along an optimum forming path is proposed in order to achieve the most even deformation distribution in the final products and to avoid failures such as wrinkling and tearing. In multi-point forming technology, by adjusting the relative position of each element in an element group, one can change the forming path so that one may implement the deformation of the sheet metal along the optimum path. On the basis of the theory of minimum plastic work, the optimum forming path is described in the paper. To establish a desired forming path, a method to generate a forming surface is developed, the method being based on the representation of an objective surface with c1 continuous by an 18 d.o.f. triangular element. Sheet forming tests are performed to evaluate the effect of the technique presented, the test results demonstrating that when deformed along an approximate optimum forming path the forming limitation of metal sheet is raised obviously, comparing with that of deformation along a common path.