FATIGUE-CRACK PROPAGATION UNDER CYCLIC THERMAL-STRESS

Structures used at elevated temperature subject to severe cyclic therm al stress. Therefore, accurate prediction procedures for thermal fatig ue crack growth should be applied to rationalise component flaw assess ment. Fatigue crack propagation tests under thermal stress were carrie d out using an modified type 316 stainless steel (316FR), which is a c andidate material for the fast reactor in Japan. Thermal stress of the tests was generated by cyclically changed temperature distribution th rough thickness in a plate by induction heating and air-cooling Numeri cal analysis was also carried out to examine the applicability of the J integral under cyclic thermal stress. The J integral under elasto-pl astic condition under thermal stress is close to the elastically calcu lated J integral. Prediction by J integral tends to be conservative fo r deeper cracks, and modification of the J integral value using crack opening ratio gives good agreement with the experimental crack growth.