Evaluation of multiaxial creep and damage evolution for small punch creep test considering critical-strain criterion

摘要

Experiment and finite element analysis were performed in this study to estimate the deformation characteristics of small punch creep test. Considering the disadvantage of the traditional model owing to numerous unknown parameters, ductility exhaustion model was introduced and used to estimate the damage and multiaxial creep evolution process. The results show that the evolution trends of creep deflection and strain with three stages are similar. During deformation, apparent damage localization is observed. The maximum strain and damage also occurred in the necking region due to the stress concentration. Thus, a critical damage value is proposed for service-exposed Cr5MO in this study. In the primary creep stage, a tensile deformation is observed at the lower surface and a compression deformation is observed at the upper surface. Subsequently, the stress triaxiality tends to be constant in the second creep stage. Thus, steady creep parameters of small punch test can be used to replace traditional creep results in the creep properties analysis of in-service components. Finally, the multiaxial creep and damage evolution characteristics of the small punch creep specimen are obtained.