Predicting failure response of spot welded joints using recent extensions to the Gurson model

The plug failure modes of resistance spot welded shear-lab and cross-tension test specimens are studied, using recent extensions to the Gurson model. A comparison of the predicted mechanical response is presented when using either: (i) the Gurson–Tvergaard–Needleman model (GTN-model), (ii) the shear-modified GTN-model by Nahshon and Hutchinson that also describes damage development at low triaxiality (NH-model) or (iii) the Gologanu–Leblond–Devaux model (GLD-model) accounting for non-spherical void growth. The failure responses predicted by the various models are discussed in relation to their approximate description of the nucleation, growth and coalescence of microvoids. Using the void shape factor of the GLD-model, a simple approach for approximating void nucleation by either particle fracture or particle–matrix decohesion is applied and a study of the subsequent void shape evolution is presented. The models are applied to predict failure of specimens containing a fully intact weld nugget as well as a partly removed weld nugget to address the problems of shrinkage voids or larger weld defects. All analysis are carried out by full 3D finite element modelling.