Rigid-plastic finite-element analysis of sheet-metal forming processes using a selective membrane/shell formulation

In most sheet-metal forming processes a large part of the deforming material exhibits stretch-dominant characteristics and the bending effect is found to exist only in a limited portion of the total deforming region. Thus the use of shell or continuum elements for the whole region is not economic. A selective membrane/shell (M/S) scheme is proposed which combines the layered degenerated shell elements with membrane elements. In the proposed scheme, membrane elements and layered degenerated shell elements are employed selectively according to the characteristics of the deformation, using the suggested criterion to consider the bending effect. The selective M/S scheme is introduced into rigid-plastic finite-element analysis for plane-strain, axisymmetric and three-dimensional problems. The computational results are then compared with the results of experiment, the comparison showing that with the selective M/S scheme the bending effect can be considered effectively whilst the computational time is reduced significantly.