SOME OBSERVATIONS ON YIELD SURFACES FOR 304-STAINLESS-STEEL AT LARGE PRESTRAIN

Experiments to study the yield surface of 304 stainless steel with eit her 20 percent tension or 20 percent shear prestrain have been conduct ed. Explicit transformation equations have also been derived to conver t the experimentally determined first Piola-Kirchhoff stress component s 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 yi eld have significant effect on the degree of anisotropy of strain-hard ening. In particular, the strain-hardening rule is extremely complicat ed if the second Piola-Kirchhoff stress is used. Also, the equivalent stress-strain curves have been investigated by means of different stre ss measures.