SHEET BENDING AND DETERMINATION OF RESIDUAL-STRESSES BY MEANS OF FEM

The simulation of metal forming processes with the finite element meth od (FEM) in the sense of a ''numerical experiment'' is gaining more an d more importance. Bending of FePO4 (St14O3), X 5 CrNi 189 and AlMgSi1 sheets in V- and U-shaped dies prove the quality of this type of calc ulation. Of particular interest here is the determination of punch for ces, strains and stresses in the workpiece. The calculation of residua l stresses is important for process optimisation. Comparisons between calculated and experimentally determined results indicate the calculat ion qualities. There are many possibilities of influencing the simulat ion quality of residual stress calculations. In particular, the materi al model has to be optimally selected. Two combined isotropic-kinemati c hardening models (from Axelsson/Samuelsson and McNamara/Sharma) impl emented in the FE program to take the Bauschinger effect into consider ation point out the influence of material models on the calculated res idual stresses.