Influence of steel strength and loading mode on fatigue properties of resistance spot welded H beam components

Abstract

The drive to downgauge steel components by substituting mild steel with thinner high strength steel means that design engineers are now working closer to the design limits with respect to fatigue performance of spot welded structures. This study was carried out on an interstitial free mild steel and two high strength interstitial free steels, in sheet thicknesses 0.8 and 1.2 mm, representative of sheet thicknesses and grades in typical body-in-white automotive structures. The results obtained indicate that steel strength had little effect on fatigue performance for the range of steels studied. In contrast, both the loading mode and the sheet thickness had a significant influence. The results for shear loading were up to ten times greater when compared to peel loading conditions. Under shear loading conditions full plug failures were widely observed, whereas with peel loaded variants partial plug failures predominated. With respect to enhancing the fatigue properties the use of larger weld sizes was shown to be beneficial.

Keywords

STEELS BEAMS RESISTANCE SPOT WELDS FATIGUE PROPERTIES

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