Crack propagation kinetics under asymmetric cyclic loading for 316LN SS in high-temperature solution

Crack propagation rates (CPRs, or da/dN) of 316LN stainless steel (SS) in high-temperature solution under asymmetric cyclic loading conditions are experimentally determined, focusing primarily on the effect of load-rise time on crack propagation. The increment in crack propagation per cyclic block mainly occurs during the load-rise period. When the stress intensity factor range (ΔK) and load ratio (R) are kept similar, a faster increase in the stress intensity factor (dK/dt) during the load-rise period results in a lower average crack propagation rate (Vave-tr) during that phase. Secondary cracks and fatigue striations are observed on the fracture surface. The CPRs show a higher environmental enhancement factor (Fen) as the load-rise time increases.