A REVISIT TO THE EFFECTIVE NOTCH STRESS S-N CURVE FOR WELDED CIRCULAR HOLLOW SECTION JOINTS

This paper examines the reliability of the effective notch stress (ENS) approach and the FAT 225 curve for welded circular hollow section (CHS) joints. This study extracts and converts numerous CHS joints fatigue data from the literature (183 tests) into the ENS system according to IIW guideline. Under the ENS system, the FAT 225 provides conservative assessment for all data points within the range of 10(4) to 10(8) cycles. The comparison with the hotspot stress approach proves that the ENS concept produces smaller scatter since it directly takes into account the geometrical thickness effect. Moreover, the safety margin in the FAT 225 curve addresses sufficiently the source of scatter not reflected in the ENS range, such as the presence of residual stress and the load ratio. The findings in this paper suggest that the recommended FAT 225 curve is applicable for fatigue assessment of welded CHS joints using the ENS approach.