Consideration of mean-stress effects on fatigue life of welded magnesium joints by the application of the Smith-Watson-Topper and reference radius concepts

Three types of welded joints have been assessed with regard to their fatigue strength based on the mean-stress damage parameter model according to Smith, Watson, and Topper (P-SWT) and on the reference notch radius concept. These analyses were performed with three different stress ratios, R = -1, R = 0 and R = 0.5, under axial loading. For each stress level, the corresponding Neuber-Hyperbolas, Masing-loops and their maximum stress and maximum strain values were determined in order to calculate damage parameter (P-SWT) values. For a given weld geometry, this damage parameter is able to unify the fatigue results for different R-values within at a tight scatter band and therefore to consider the mean-stress effect. The unification of the results for different weld geometries is performed by applying the reference radii r(ref) = 0.05 and r(ref) = 1.00 mm as suggested by the IIW-Recommendations. (C) 2012 Elsevier Ltd. All rights reserved.