The Fatigue of Weldments Subjected to Complex Loadings

Abstract

Cruciform and double-strap lap weldments were fatigue tested under constant amplitude axial load and SAE Bracket Spectrum load conditions. For the cruciform weldments, fatigue cracks generally initiate at the root but may initiated the toe if higher bending stresses are induced by joint distortion. For double strap lap weldments, the stress ratio (R) and weld shape are the major factors influencing the fatigue crack initiation site.

The fatigue test results were compared with predictions made using an initiation-propagation model, and good agreement between experiment and theory was observed. The model for the predictions assumes that the fatigue crack initiation period, which is the number of cycles for the initiation of a fatigue crack and its early growth and coalescence into a dominant fatigue crack, is the main portion of the total fatigue life at long lives.