TRANSITIONAL BEHAVIOR OF RESIDUAL FATIGUE LIFE AFTER APPLYING OVERLOAD DURING FATIGUE CRACK GROWTH WITH CONSTANT STRESS AMPLITUDE

摘要

It is well known that crack propagation is retarded after applying a tensile overload, and accelerated after applying a compressive overload. However, at a negative value of the baseline stress ratio, the fatigue crack propagation rate can accelerate after applying a tensile overload. To evaluate such creek propagation behavior, the effective stress intensity factor range has been employed. In the present study, the effects of a tensile overload followed by a compressive overload on crack propagation were investigated. The transition of residual fatigue life after applying these loads was observed and this behavior was dependent on the loading conditions. When the applied overload level was lower man a critical level, retardation of crack propagation was observed. However, when the applied overload level was higher than a critical level, the crack growth rate got higher. These phenomena are related to not only residual stress, but also crack opening behavior.