A new approximate model for the R-ratio effect on fatigue crack growth rate

A new approximate model for predicting the crack growth rate is proposed, which can condense the stable crack propagation stage curves for non-zero stress ratios to that for R = 0 in a narrow band. By using the new approximate model, the obtained material constants corresponding to R = 0 can be further widely used for different loading amplitude ratios. Many available experimental data taken from literature are analyzed using the proposed model for prediction of the crack growth rate. The results indicate that the new approximate model is accurate and effective to consider the R-ratio effect on the crack growth rate.