Evaluation of geometrical notch and quality effects in the fatigue strength assessment of ultra-high-strength steel cut edges

Experimental fatigue tests were performed for the S960 and S1100 steel grades laser cut notched geometries in this study. Fatigue test results were analyzed with the conventional nominal stress method in order to compare the fatigue performance to current standards. A finite element method -based local stress method was employed to consider the geometrical notch and surface roughness, together with a multiparametric 4R method to obtain the local cyclic behavior at the notch root, considering residual stresses, local material properties, 3D-scanned surface quality, and geometry-related notch stress. The nominal stress method with the standard S-N curves showed both unconservative and conservative results for the low-quality and high-quality cut edges, respectively, while the 4R method significantly improved the accuracy of the fatigue strength predictions.