The influence of dynamic strain ageing on stress response and strain-life relationship in low cycle fatigue of 316L(N) stainless steel

Abstract

It has been recognized that the essential prerequisite for accurate prediction of low cycle fatigue life (LCF) at elevated temperatures is the determination of rate controlling time dependent damage process that influences the cyclic deformation and fracture behavior of alloys. At intermediate temperatures (0.25 < T/T{sub m} < 0.55, where T{sub m} is melting point in Kelvin), where the effects of time dependent processes such as creep and oxidation are found to be minimal, the drastic reduction in low cycle fatigue life observed with increasing temperature and decreasing strain rate in alloys such as type 04 stainless steel, Nimonic PE 16 superalloy and Haynes 188 superalloy has been ascribed primarily to the deleterious effects of dynamic strain ageing (DSA). These alloys displayed anomalous cyclic hardening and an increase of maximum cyclic stress with increasing temperature or decreasing strain rate due to DSA. The nitrogen alloyed 316L stainless steel is currently used for a variety of components in the liquid metal cooled fast breeder reactor (LMFBR). Although the temperature range of application of 316L(N) in LMFBRs encompass the domain in which DSA is active, to-date there has been little information available on the effects of DSA on cyclic behavior of 316L(N)more » stainless steel (SS). The present investigation is therefore focused on assessing the effects of DSA on LCF life and cyclic stress response of 316L(N) SS. The influence of DSA on cyclic strain-life relationship has also been examined in the regime where other time dependent mechanisms such as creep and oxidation are virtually absent.« less