Fatigue design of axially-loaded high frequency mechanical impact treated welds by the effective notch stress method

Abstract

The effective notch stress method (ENS) as defined by the International Institute of Welding is widely used by design engineers to assess the fatigue strength of welded components. This paper provides a comprehensive evaluation of published data for welded joints improved by high frequency mechanical impact (HFMI) treatment. The goal is to verify already-known fatigue classes for the ENS with the available axially-loaded fatigue data. In total, 280 experimental test results obtained from longitudinal, cruciform and butt welds subject to stress ratio of R=0.1 axial loading are evaluated. Notch stress concentration factors (Kn) for each joint geometry are analysed based on the finite element method. Calculated Kn and reported nominal stress values are used to determine local stresses. Fatigue strength assessment of the all available data is performed by the previously-proposed and verified correction procedure for yield strength (fy). A formerly-defined minimum Kn values as a function of fy is used for butt welds. The already-known fatigue classes are found to be conservative with respect to available fatigue test data.