Numerical analysis for bifurcation fracture of sheet metal forming

A new simulation code for finite element (FE) analysis is proposed for sheet metal forming with bifurcation fracture. Dynamic solution of the FE method is used instead of static solution, because the computational time using dynamic code increases linearly, whereas the time for using static code increases as self-multiplication according to increasing numbers of node. The dynamic code is also applied to a deformation of elasto-viscoplastic material because plastic deformation of real metal can be explained by dislocation theory and expressed by a mechanical model with viscosity. Moreover, this code can simulate bifurcation fracture in a process of plastic working, because the fracture is treated as a separation along a connected surface between two elements instead of disappearance of element stiffness.