Retardation mechanisms and modeling of fatigue crack growth of a high-strength steel after single overload

This study investigated the retardation mechanisms and modeling methodology for the fatigue crack growth (FCG) of a high-strength Q500qE steel after a single overload. Different stress ratios (R = 0.1, 0.3, and 0.5) and overload ratios (OLR = 1.5, 2.0, and 2.5) were considered as key parameters. The digital image correlation (DIC) testing technique was used to capture the deformation at the crack tip during the tests. The crack closure response in the crack wake region was investigated using a virtual extensometer. The results show that, under an identical stress ratio, the fatigue life was increased as the OLR increased. The FCG was completely arrested when OLR reached 2.5 when R ≥0.3. Under an identical stress ratio, the residual strain before the crack tip and the residual deformation in the crack wake region increased with the rise of the overload ratio after a single overload. It's found that the FCG was retarded or completely arrested due to the constraint of the crack tip plastic zone caused by single overload. Finally, a modified Wheeler model was proposed to predict the FCG rate based on the measured plastic zone size at the crack tip, and the predicted results agree well with the experimental findings.