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

The simulation of metal forming processes with the finite element method (FEM) in the sense of a ''numerical experiment'' is gaining more and 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 calculation. Of particular interest here is the determination of punch forces, strains and stresses in the workpiece. The calculation of residual stresses is important for process optimisation. Comparisons between calculated and experimentally determined results indicate the calculation qualities. There are many possibilities of influencing the simulation quality of residual stress calculations. In particular, the material model has to be optimally selected. Two combined isotropic-kinematic hardening models (from Axelsson/Samuelsson and McNamara/Sharma) implemented in the FE program to take the Bauschinger effect into consideration point out the influence of material models on the calculated residual stresses.