Fatigue strength assessment of HFMI-treated butt welds by the effective notch stress method

Abstract

Experimental fatigue data for high-frequency mechanical impact (HFMI)-treated butt welds with low stress concentrations have been collected and analysed using the effective notch stress (ENS) method given by the International Institute of Welding (IIW). The aim of this study is to suggest a more reliable fatigue assessment procedure for HFMI-improved butt welds with low stress concentration factors. In total, 165 published test results for butt welds subject to R = 0.1 and R = 0.5 axial loading are presented. K n, min values for the ENS approach are suggested in order to avoid computational problems due to low stress concentrations at the weld toe. Minimum notch stress concentration values are suggested based on the material yield strength (f y ). All the data is presented with respect to previously proposed and verified material f y correction method. For HFMI-treated butt welds in the ENS system, the use of the K n, min values with the f y correction representing one fatigue class (approximately 12.5 %) increase in strength for every 200-MPa increase in f y has been proposed and verified. © 2014 International Institute of Welding.