Strength assessment of spot-welded sheets of interstitial free steels

The effects of nugget diameter, mode of loading and alloy chemistry have been studied on the strength of spot-welds in thin sheets of interstitial free steels. Spot-welds with three nugget diameters have been fabricated by alteration of the welding current while two interstitial free steels with different chemistry have been selected. The mode of loading has been varied either as sliding using tensile-shear and pure-shear specimens or as opening using cross-tension specimens. The results unambiguously infer that the strength values of spot-welds remain same in a specific mode of loading, while the load-bearing capacity increases with increasing nugget size. The strength values in different sliding mode of loading are similar but are higher than that in opening mode; these observations have been explained using Von Mises' criterion of yielding. The strength of the spot weld is found higher than that of the base metal with an interesting observation that the former bears a constant ratio with the latter. (C) 2008 Elsevier B.V. All rights reserved.