Low cycle fatigue analysis of CTOD under variable amplitude loading for AH-32 steel

The present work aims to investigate the fatigue crack growth behavior of AH-32 steel with the experimental application of CTOD. A series of fatigue crack growth experiments on AH32 steel were conducted by a constant amplitude loading with a single/two tensile overload. The fatigue crack growth behavior of AH32 steel with overload was explored in a detailed manner. The retardation effect of the overload with different overload ratio and overload spacing were quantified by crack growth rate. Moreover, a different relationship between da/dN and CTOD for all tests was obtained. In a parallel study, the elastic-plastic numerical model was developed to investigate the crack closure effect expressed in the form of crack opening load and CTOD. Experimental results show that the CTOD is able to characterize and correlate the fatigue crack growth at large scale yielding. This work is intended to contribute to a better understanding of the different mechanisms driving fatigue crack growth.