关键词: down- hill simplex method, pressure dependent asymmetric metal, modified Burzynski criterion, non-associated flow rule (NAFR)

Abstract: The Burzynski criterion is developed for anisotropic asymmetric metals with the non-associated flow rule (NAFR) for plane stress problems. The presented pressure depending on the yield criterion can be calibrated with ten experimental data, i.e., the tensile yield stresses at 0°, 45°, and 90°, the compressive yield stresses at 0°, 15°, 30°, 45°, 75°, and 90° from the rolling direction, and the biaxial tensile yield stress. The corresponding pressure independent plastic potential function can be calibrated with six experimental data, i.e., the tensile R-values at 0°, 15°, 45°, 75°, and 90° from the rolling direction and the tensile biaxial R-value. The downhill simplex method is used to solve these ten and six high nonlinear equations for the yield and plastic potential functions, re- spectively. The results show that the presented new criterion is appropriate for anisotropic asymmetric metals.

Key words: down- hill simplex method, modified Burzynski criterion, pressure dependent asymmetric metal, non-associated flow rule (NAFR)