The length parameter for gigacycle fatigue life predictions of notched specimens made of 304L steel

Abstract

In this paper, the fatigue data of smooth and notched specimens are evaluated using the method based on the theory of critical distances. This method is suitable for predictions of the fatigue lifetime of notched specimens using the axial stress distributions, the length parameter, and experimental data measured on smooth specimens. The critical length parameter lcr is determined from the relationship between two fatigue curves (one generated by testing smooth specimens and the other generated by testing specimens with a model notch). Experimental fatigue data are obtained using an ultrasonic fatigue pulsator at a frequency of 20 kHz and a load stress ratio R = −1. The paper describes the dependence of the critical length parameter for different notch radii on the number of cycles to fracture, as well as on the applied stress amplitude. The obtained results prove the possibility of using the critical length parameter for fatigue life prediction of notched specimens.