Strain-rate dependence of residual strength and ductility of AISI 316 stainless steel after creep, fatigue and irradiation

The mechanical response against impact loading of reactor structures during their life is predicted by computer codes which need constitutive equations describing the effects of damage processes like creep, low cycle fatigue and irradiation on material properties. In this context a method is proposed which is based on the measurement of the residual tensile properties at low and high strain-rate after interrupted creep, low cycle fatigue and irradiation tests of the material. The determination of the damage parameters follows by comparing the flow curves of damaged and as-received materials. This method has been applied to AISI 316 stainless steel obtaining a qualitatively common mechanical response of the material damaged by creep, low cycle fatigue and irradiation characterized by strength increase, reduction of ductility and instabilities along the flow curve before the onset of necking. The phenomena observed may be described by constitutive equations based on the thermal activation theory. (author)