EFFECT OF CREEP-FATIGUE LOADING CONDITION ON CRACK TIP FIELDS OF GRADE 91 STEEL AT CRACK INITIATION AND GROWTH

In this paper, the effect of creep-fatigue loading condition on crack tip deformation and stress fields of Grade 91 steel at 600oC at crack initiation and growth is studied. By using finite element debond analysis method, creep-fatigue crack growth tests using C(T) specimens under various load ratios and hold times are simulated, and the effect of creep-fatigue load ratio and hold time on the plastic zone, creep zone, crack opening profile, equivalent stress, crack-opening stress and triaxiality at crack initiation and growth is presented. It is found that the crack tip deformation and stress fields under tension-compression creep-fatigue loading are overall different from those under tension-tension creep-fatigue and pure creep loading, due to crack closure.