Effect of weld nugget size on overload failure mode of resistance spot welds

Abstract

In the present paper, effects of welding current, welding time, electrode pressure and holding time on the weld nugget size were studied. A failure mechanism was proposed to describe both interfacial and pullout failure modes. This mechanism was confirmed by SEM investigations. In the light of this mechanism, the effect of welding parameters on static weld strength and failure mode was studied. Then, an analytical model was proposed to predict failure mode and to estimate minimum nugget diameter (critical diameter) to ensure pullout failure mode in shear tensile test. On the contrary to existing industrial standards, in this model, critical nugget diameter is attributed to metallurgical characterisation of material (weld nugget hardness to failure location hardness ratio), in addition to sheet thickness. For a given sheet thickness, decreasing H WN H FL increases interfacial failure mode tendency. The results of this model were compared with experimental data and also with the literature.

Effects of Welding Parameters on Strength and Corrosion Behavior of Dissimilar Galvanized Q&P and TRIP Spot Welds

“…Coherently with the literature about resistance spot welding [5,8,9,[30][31][32][33], there is a clear relationship between the shear strength and the nugget size of the Q&P/TRIP spot welds. In particular, shear strength increases as nugget diameter widens, Figure 6.…”

“…This contrariety could be ascribable to the stronger electrode indentation in samples no. 2, which are caused by the higher clamping force employed, that could induce high stress concentrations in the sheets surface close to the spot [31,34]. On the other hand, it is presumable that metal expulsion has limited the maximum achievable shear strength.…”

Effects of Welding Schedules on Resistance Spot Welding of DP600 Steel

“…The critical nugget size suggested by Pouranvari as Dcr = 8tHFL/HWN (t, sheet thickness; HFL, failure location hardness; HWN, weld nugget hardness), however, is overestimated. 21) It is necessary to develop a new criterion considering HAZ softening and welding defects occurrence for a better prediction of failure mode. Further studies related to the failure prediction are in the plan.…”

Dissimilar spot welding of DQSK/DP600 steels: the weld-nugget growth

“…The quality and mechanical behavior of spot welds significantly affect the durability and crashworthiness of a vehicle. [1][2][3] To ensure and maintain the structural integrity of a finished component under a wide range of operating conditions, e.g., a crash situation, a remotest possibility of producing even one or two defective welds in a critical component needs to be eliminated. These requirements, coupled with the uncertainties about the weld quality due to the difficulty of applying nondestructive tests to spot welds, are responsible for the practice of making more spot welds than needed for maintaining the structural integrity.…”