Fatigue assessment of welded very thin steel sheets made from 1.4404 using notch and structural stresses: IIW document XIII-3166-2025, German delegation

Abstract

This paper examines the fatigue behaviour and assessment of welded very thin joints, with thicknesses ranging from 0.1 to 2.0 mm, fabricated from austenitic stainless steel 1.4404 (AISI 316 L). Fatigue tests were conducted to derive S-N curves, providing insights into the fatigue strength characteristics, i.e. endurable nominal stresses, slope, and knee point. Two distinct approaches were employed for fatigue strength assessment: the structural stress approach and the notch stress approach. Notably, when thickness effects are integrated into the structural stress approach, the resulting S-N curves converge into a single curve with low scatter, indicating a reliable fatigue strength assessment. In contrast, the assessment of the welded joints using the notch stress approach, with a reference radius of rref=0.01mm, resulted in significant scatter.