EVALUATION OF THE DYNAMIC EXPLICIT ELASTOVISCOPLASTIC FINITE-ELEMENT METHOD IN SHEET-FORMING SIMULATION

The application of the dynamic explicit time integration method has been proven to be efficient and robust for sheet-metal forming simulation. However, the sheet stamping operation in the automobile industry is usually a quasi-static process. Therefore, there remain some subjects to investigate, such as the estimation of dynamic effects and the evaluation of numerical schemes of so-called mass scaling, damping scaling and material viscosity scaling. In this paper, these problems are investigated by the approaches of the theoretical formulation and numerical verification. Firstly the principle of virtual power is proposed to interpret the quasi-static deformation process, adopting the Lagrange multiplier method to introduce quasi-static conditions. Next, a discussion is focused on the comparison between the real forming process and the virtual simulation process. The latter employs a high forming speed to reduce the consumptions of computation time. Finally the hemispherical-punch deep-drawing of a square sheet is analyzed using a new dynamic explicit/elasto viscoplastic finite-element program developed by the authors. The numerical results are compared with either the experiments or static explicit/elasloplastic analyses. The suitability of the newly developed program for the quasi-static deformation process is confirmed.