Prediction of limit strains in sheet metals by using new generalized yield criteria

A new form of yield theories considering an anisotropic parameter for porous sintered powder metallurgy metals have been derived and proposed in this technical paper. In addition to these, the flow rule with anisotropic parameter for porous metal is introduced. The mathematical expression for the calculation of flow stress in the case of simple compression of tension test is deduced from the yield theories for the P/M sintered preforms of the metals. These yield theories are used for the determination of the limit strains in connection with the swift’s plastic instability condition for diffuse necking and the Hill’s plastic instability condition for localized necking.