Some Observations on Yield Surfaces for 304 Stainless Steel at Large Prestrain

Abstract

Experiments to study the yield surface of 304 stainless steel with either 20 percent tension or 20 percent shear prestrain have been conducted. Explicit transformation equations have also been derived to convert the experimentally determined first Piola-Kirchhoff stress components into the Cauchy stresses and the second Piola-Kirchhoff stresses for combined axial-torsional experiments. It has been found that, in the phenomenological approach, the stress measure and the definition of yield have significant effect on the degree of anisotropy of strain-hardening. In particular, the strain-hardening rule is extremely complicated if the second Piola-Kirchhoff stress is used. Also, the equivalent stress-strain curves have been investigated by means of different stress measures.