The explicit scheme for finite element analysis of sheet metal forming problems has been widely used for providing practical solutions since it improves the convergency, memory size and computational time especially for the case of complicated geometry and large element number. Thus many problems encountered in implicit finite element analysis can be solved by using the explicit scheme. The explicit schemes in general use are based on the elastic-plastic modelling of material requiring large computation time.
In the present work, a basic formulation for rigid-plastic explicit finite element analysis of plain strain sheet metal forming problems has been proposed. The effect of some basic parameters involved in the dynamic analysis has been studied in detail. Thus, the effective range of parameters have been proposed for numerical simultion by the rigid-plastic explicit finite element method. A direct trial-and-error method is introduced to treat contact and friction. In computation, sheet material is assumed to possess normal anisotropy and rigid-plastic workhardening characteristics.
In order to show the validity and effectiveness of the proposed explicit scheme, computations are carried out for cylindrical punch stretching and the computational results are compared with those by the implicit scheme and a commercial code. It has been thus shown that the developed program is in good agreement with the implicit scheme as well as with the commercial code. The explicit scheme is in good agreement with the implicit scheme for numerical analysis of auto-body panels in which plain-strain condition can be assumed by dividing the whole piece into sections. The proposed rigid-plastic explicit finite element method can be used as a robust and efficient computational method for prediction of defects and forming severity.
