IMPLICIT SCHEME FOR CONTACT ANALYSIS IN NONSTEADY STATE FORMING

The finite element analysis of deformation of viscoplastic material in volves contact between the tool and the workpiece. Here unilateral con tact condition with the possibility of nodes originally in contact, lo sing contact subsequently, is analysed in non-steady state forming pro cesses. Friction has been taken into consideration through a potential function. Node to node contact is analysed and contact forces at the node are used to decide if the node is to be released. Two different a lgorithms are presented for treating the nodal contact condition. The one step explicit method with projections on the surface of contact wa s already implemented in the FORGE2(R) software. An implicit scheme is proposed and compared with the existing scheme. The advantages of thi s scheme are numerically shown by solving some examples. It is observe d that the volume losses are reduced. This makes it possible to use la rger time steps or increase the computational accuracy.