Assessment of tensile properties of spot welds using shear punch test

Standard test procedures are difficult to employ for determining tensile properties of spot welds due to their small volume. In order to overcome this limitation, attempts have been directed here to assess tensile properties of spot welds made on interstitial free (IF) steel sheets using shear punch tests. These experiments have been supplemented with microstructural examinations using optical, SEM and TEM, standard tensile tests, microhardness tests, and fractographic studies in order to understand in-depth tensile behavior of spot welds. The obtained results assist to infer that strength values obtained from tensile tests of varyingly pre-strained IF steel sheets are linearly correlated with their corresponding shear strength values obtained from shear punch tests. Based on the above linear correlation, the tensile and yield strength of the weld nuggets have been estimated for the first time using shear punch test. The estimated strength values of the weld nugget region are found to be higher compared to that of the base metal; this has been explained by considering the microstructural constituents formed at the fusion zone during the welding process.