High-cycle rotating bending fatigue test of notched specimens to support the application of N-SIF-based fatigue assessment approaches

This paper presents the results of a relatively wide experimental campaign, which was conducted with the aim of complementing test data already available in the open literature. A few years ago, several fatigue tension tests were conducted on notched square-section specimens. The purpose of these tests was to provide support for the validation of fatigue assessment approaches based on the notch stress intensity factor (N-SIF) concept, e.g. the strain energy density approach and the peak stress method. However, it should be noted that the run-out was limited to 2·106 cycles. With ships and offshore structures as the primary focus of this study, which undergo 108 cycles during their operational lifespan, a few series of rotating bending fatigue tests were conducted on variously notched specimens made of different structural steels. These tests were carried out up to 5·107 cycles as the run-out target. A total of approximately 100 specimens were prepared and tested, which resulted in a comprehensive data set that also included measurements of local notch geometries. The findings revealed that the notch geometry, specifically the notch opening angle and the radius at the tip, exerted a substantial influence on the fatigue strength. The analysis of the experimental data is further enhanced by the useful comparisons with numerical finite element simulations of specimens by applying the strain energy density approach.