The influence of negative and positive stress ratios on crack growth rate in AM60B magnesium alloy

In this paper, the effect of stress ratio on fatigue crack growth rate (FCGR) of AM60B magnesium alloy plates at room temperature is studied. The plates are loaded under a wide range of stress ratios (−1, −0.8, −0.6, −0.3, 0, 0.25, 0.5 and 0.75) and the behavior of the center crack is investigated. Most FCGR data available in the literature have been presented using various FCGR models that are mainly based on a positive stress intensity range as well as the entire stress intensity range. In this paper, a modified model, developed based on the Walker model, is proposed. The model condenses and presents the data obtained under the wide stress ratio range into a single line on a logarithmic scale. Finally, the variances in the FCGR data that were presented with different models from the best-fitted line to the zero stress ratio were calculated and compared to each other to clarify the efficiency of the model.