Creep crack growth under small-scale creep conditions

Abstract

Two different constitutive models are employed to describe creep crack growth under small-scale creep conditions theoretically. The first model combines elastic/nonlinear viscous deformation fields (% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGafqyTduMbai% aacqGH9aqpcuaHdpWCgaGaaiaac+cacaWGfbGaey4kaSIaamyqaiab% eo8aZnaaCaaaleqabaGaamOBaaaaaaa!4077!\[\dot \varepsilon = \dot \sigma /E + A\sigma ^n \]) with a critical-strain criterion, % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeqyTduMaey% ypa0JaeqyTdu2aaSbaaSqaaiaadogaaeqaaaaa!3B55!\[\varepsilon = \varepsilon _c \], to be satisfied at a structural distance xc ahead of the crack. The deformation fields are characterized by three singular fields — the remote elastic field, the HRR field in the creep zone, if one exists, and the Hui-Riedel (HR) field near the growing crack tip. At small stress intensity factors, crack growth is found to become irregular and to tend to instabilities. This is a consequence of the properties of the HR field.