New approach to fatigue life prediction of notched specimen under non-proportional loading

Abstract

Neuber’s rule and Peterson’s formula are used to calculate the local strain and stress at the notch root based on the fatigue test results of notched specimens of Mod.9Cr-1Mo steel. The critical plane approach, Smith-Watson-Topper (SWT) approach, is used for the fatigue life prediction. It is shown that the prediction results to the notched specimens with smaller notch radius are conservative according to Neuber’s rule but non-conservative when using Peterson’s formula. A new approach to the fatigue strength reduction factor is proposed based on Peterson’s formula by considering the non-proportionality of strain path. With few exceptions, the predictions agree well with the experimental results, and most predictions are in a factor-2 scatter band.