Abstract
This paper summarizes the results of an investigation for the deformation hardening behaviors of
neutron-irradiated stainless steels in terms of true stress(σ)–true strain(ε) curves. It is commonly accepted
that the σ-ε curves are more informative for describing plastic flow, but there are few papers devoted to
using the true curves for describing constitutive behaviors of materials. This study uses the true curves
obtained from stainless steel samples irradiated to doses in the range of 0–55 dpa by various means: finite
element calculation, optic extensomentry, and recalculation of engineering curves. It is shown that for the
strain range 0–0.6 the true curves can be well described by the Swift equation: σ=k×(ε-ε0)0.5. The
influence of irradiation on the parameters of the Swift equation is investigated in detail. It is found that in
most cases the k-parameter of this equation is not changed significantly by irradiation. Since large data
scattering was observed for the ε0-parameter, a modified Swift equation σ=k*(ε- σ0
2/k2)0.5 was proposed
and evaluated. This equation is based on the concept of zero stress, which is, in general, close to yield
stress. The relationships among k, σ0, and damage dose are discussed in detail, so as to more accurately
describe the true curves for irradiated stainless steels.
