Assessment of damage and life prediction of austenitic stainless steel under high temperature creep-fatigue interaction condition

It is understood that grain boundary cavitation is one of the detrimental processes for the degradation of austenitic stainless steels that reduces the creep-fatigue life at high temperatures. A new, damage function based on a model for the creep-fatigue life prediction in terms of nucleation and growth of grain boundary cavities is proposed for austenitic stainless steel. This damage function is a combination of the fatigue and creep terms related to the cavitational damage (cavity nucleation and growth) in the life prediction equation and is found to be generally applicable to all the materials in which failure is controlled by the grain boundary cavitational damage. The creep-fatigue data from the present and other investigations are used to check the validity of the proposed damage function, and it is shown that they satisfy the general reliability of damage function. Additionally. using this damage function. one may realize that all the Coffin-Manson plots at the various levels of tensile hold time and temperature under strain controlled creep-fatigue tests can be normalized to make the master curve. Using this master curve, one may easily calculate the expected creep-fatigue life for austenitic stainless steels under tensile hold high temperature low cycle fatigue test conditions to save much of the testing time and effort. (C) 2002 Elsevier Science B.V. All rights reserved.