The effects of loading parameters on Fatigue Crack Propagation (FCP) in a heat treated 12NC6 steel

This work concerns the study of fatigue crack propagation with constant amplitude loading. The LogC vs rn representation is a straight line. This induces a 'pivot point' defined by the coordinates (Delta K)(p) and (da/dN)(p). The existence of this point means that the characterisation of the FCP depends on only one parameter: C or m. According to Elber, the closure rate U is only a function of load ratio R. In this study, when it occurs, the closure stress intensity factor K(cl) is approximately constant. This work indicates that the closure ratio U is not only R-dependent as stipulated by Elber but is also a function of the maximum stress intensity factor K(max).