Parameter determination method of Gotoh yield criterion based on non-associated flow rule

Yield criterion has an important influence on theoretical analysis, process optimization and finite element simulation of sheet metal forming process. By enhancing the anisotropy characterization ability of the yield criterion, the reliability of the forming process and the accuracy of the actual prediction can be ensured. In this paper, a new set of parameter solving method for the Gotoh yield criterion is given based on non-associated flow rule. On the basis of common yield criteria and different flow rules, the 5754O aluminum alloy, DP980 advanced high-strength steel and SAPH440 structural steel sheet were taken as examples, the anisotropic deformation behavior of which were predicted under different loading paths. The yield function and plastic potential function derived from Gotoh yield criterion and the theoretical functions based on associated flow rule were used to calculate the distributions trend of yield stress and r-value along different loading angle. Furthermore, the yield locus under the plane stress state is analyzed, and the prediction accuracy the anisotropic yield behavior based on different yield criteria and the flow rules is verified. By comparing the theoretical and experimental results, it is shown that different yield criteria with same flow rule have significant differences in anisotropic characterization ability for the same sheet. There are also obvious deviations in the characterization process when the yield criterion is adopted based on different flow rules. The yield criterion based on non-associated flow rule can greatly improve its own flexibility and accuracy, and the characterization ability is significantly enhanced. The final results will provide an important reference for the actual application strategy of the yield criteria in the plastic forming field. © 2018, Editorial Office of Chinese Journal of Theoretical and Applied Mechanics. All right reserved.