The investigation of the yield loci of sheet metals

In order to evaluate the accuracy of the existing yield criteria, biaxial tensile tests of 5754O aluminum alloy sheet and B170P1 steel sheet were performed with cruciform specimens and a biaxial loading testing machine under linear loading paths. The biaxial stress-strain curves in the rolling direction and the transverse direction under different loading paths were obtained. The experimental yield loci were determined from the experimental stress-strain curves according to the plastic work equivalent theorem. The experimental yield loci were compared with the theoretical yield loci calculated from several existing yield criteria (Hill'90, Hill'93, Barlat'89 and Yld2000-2d yield criterion). The errors between the experimental results and those based on the existing theoretical yield criteria were investigated. It is found that the experimental yield loci of both 5754O aluminum alloy sheet and B170P1 steel sheet can be described well with Yld2000-2d yield criterion. For both 5754O aluminum alloy sheet and B170P1 steel sheet, the results based on Yld2000-2d yield criterion are in better agreement with the experimental results than those based on the other three yield criteria.