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 (PSWT) 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 (PSWT) 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 rref = 0.05 and rref = 1.00 mm as suggested by the IIW-Recommendations.

► Three types of welded joints are assessed.
► The mean-stress damage parameter model and reference notch radius concept are employed.
► Both methods are able to evaluate the mean-stress effect.
► The uniform scatter was TP,SWT = 1:1.50.
► The slope k of PSWT–NR lines for rref = 1.00 mm is k = 3.0 as recommended by IIW.