Numerical treatment of contact and friction in FE simulation of forming processes

The problem of contact between a part and a tool or between two deforming bodies is analysed in view of metal forming processes. For simplicity, only the case of viscoplastic materials is considered. The velocity formulation is presented, with different time integration schemes. The contact with a rigid tool is considered first and various forms of contact formulations are described: nodal contact, integral formulation with a penalty or with a Lagrange multiplier method. Time integration is considered which results in various explicit or implicit contact formulations. Special attention is paid to the contact between two deforming bodies or to the self contact when a fold is generated in the workpiece.