Rigid-plastic finite element analysis of sheet metal forming processes with initial guess generation

A method for the rigid-plastic finite element analysis of sheet metal forming with contact is proposed. A method of initial guess generation is devised by using the elastic finite element method with geometrical nonlinearity combined with the proposed contact treatment. An improved method of contact treatment is developed in which a skew boundary condition is successively used during iteration. A simple but effective contact algorithm to decide the proper contact region is also suggested. In order to verify the validity of the developed method, axisymmetric stretching is analysed and compared with the available axisymmetric FEM results. As three-dimensional applications, stretching of a square sheet and deep drawing of a square cup are analysed. The supporting experiments are also carried out. The computational results are compared with the experiments. The comparison has shown that the computed results by the proposed method are generally in good agreement with the experiments. It is shown that the present method can be used effectively in the analysis of other sheet metal working processes. However, it has been found that the membrane approach shows a limitation for the processes with deformation regions in which the bending effect is not negligible.