ABSTRACT
A recent experimental study examined the quasi-static crushing and axial impact behaviour of square and spot-welded top-hat sections, which ware made from two different high-strengtlt steels and one mild steel. While no specific change in the ocollapse mode was observed, structural effectiveness differences developed for the different material classes and geometries, which hinder the weight-rcduction potential of crashworthy designs with high-strength steels. The limited strain-rate Sensitivity of the high-strength Steels under dynamic loadings is one explanation. Moreover, the different strain hardening characteristics upon strain reversal affect the weight-specific energy absorption efficiency of the high-strength steels even for quasi-static loadings. Results from peel tests on spot-weld samples suggest that the partial and complete failure of spot-welds during the axial collapse of thin-walled structural sections, further accentuates the loss in the advantage of high-strength steels over mild steels, especially for spot-welded top-hat sections. It is anticipated that these observations have implications for design purposes and theoretical and numerical analyses of joined and unjoined thin-walled structures used as energy absorption systems.
