Effect of multiaxial stress and strain on low cycle fatigue, creep and creep-fatigue lifetimes for type 304 steel cruciform and cubic specimens

摘要

This paper discusses low cycle fatigue, creep and creep-fatigue life evaluation methods for a SUS 304 austenitic stainless steel in a full range of strain and stress multiaxiality using a cruciform and cubic specimen. Five multiaxial strain parameters are investigated whether or not they appropriately express the trend of low cycle fatigue lives in the full range of biaxial stress state. Then, the effects of the stress biaxiality and triaxiality on creep void formation are discussed. The stress biaxiality and triaxiality raise the creep void formation and the void formation is confirmed even in an equi-triaxial tension creep test in which the value of von Mises equivalent stress is zero. However, the stress biaxiality slightly shortens creep rupture lifetimes but the stress triaxiality drastically reduces creep rupture lifetimes. Finally, the effect of strain biaxiality on creep-fatigue life is discussed based on the experimental results using a cruciform specimen by applying the linear damage rule. The predicted results of creep-fatigue lives under biaxial strain states are slightly dependent on the applied multiaxial strain and stress parameters but there is no significant difference in the predicted lives depending on the multiaxial strain and stress parameters.