Abstract: “In this paper, seven fatigue crack growth models, namely Priddle, McEvily, Weertman, Collipriest, Broek, Walker and Forman have been examined. The mean stress effect on fatigue crack growth rate is commonly introduced into fatigue crack growth (FCG) relation through the stress ratio, R. Therefore, the ability to correlate and predict the fatigue crack growth rate, FCGr, for different R values is of significant importance for damage tolerant design. Performance of the crack driving force of these models in accounting stress ratio effects in fatigue crack growth rate is evaluated by fitting a lowess curve on transformed FCG data. Experimental fatigue crack growth data of a typical Al 2024 T351 obtained under constant amplitude loading tests for six load ratios has been used in the present work. From the studies carried out, it is observed that Walker and Collipriest models are found to be in good agreement with the experimental FCG data”

Keywords: Fatigue crack growth; Stress ratio effects; Crack driving force; Lowess Curve.