Strain Rate Sensitivity, Strain Hardening, and Yield Behavior of 304L Stainless Steel

Abstract

Sheet and rod stock of 304L stainless steel were tested in uniaxial tension and compression at strain rates between 10−4 s−1 and 104 s−1. To evaluate the yield locus behavior of the sheet material, multiaxial experiments were performed at a strain rate of 10−3 s−1. We have analyzed these results in terms of existing strain-rate sensitivity, work hardening, and yield locus models. Strain-rate sensitivity was found to follow a thermal activation law over the entire range of strain rates used in this investigation. The best description of strain hardening did depend on the strain range to which the data were fit. The Voce law was the most accurate at large strains (ε > 0.40), whereas at small strains, in the vicinity of yield, the laws of either Swift or Ludwik were the most accurate. A simple power law description of work hardening was inadequate over all levels of strain. We examined a number of yield criteria, both isotropic and anisotropic, with respect to the biaxial yield behavior. Bassani’s yield criterion gave the best fit to our experimental results. However, the simple von Mises yield function also gave an acceptable prediction of yield strength and direction of current plastic strain rate. The yield criteria of Hill, both the quadratic and nonquadratic versions, did not match the experimental data. We feel that these results have direct application to the selection of the proper constitutive laws for the finite element modeling of the deformation of 304L stainless steel.