Ideal sheet forming with frictional constraints

The ideal forming theory, previously developed as a direct design method to guide iterative design practices based on analytic methods, does not properly account for frictional effects prevalent in real forming. A method for introducing the effects of the Coulomb friction in the ideal sheet forming theory was developed in this work by modifying the extremum work criterion. For numerical implementation, a rigid-plastic finite element method was used based on triangular membrane elements. Computational results were compared with experiments given in NUMISHEETʹ93 using a planar anisotropic strain rate potential proposed by Barlat et al. (Barlat, F., Chung, K., Richmond, O., 1993. Strain rate potential for metals and its application to minimum plastic work path calculations. Int. J. Plasticity 9, 51.) and the Coulomb friction model.