Tensile Behaviour of S690QL and S960QL under High Strain Rate

Abstract

Despite offering significant strength-to-weight advantages, high-strength structural steels, such as S690QL and S960QL, are used only in limited offshore applications. This is due to the lack of material characterisation in regard to their tensile behaviour, with little data available on loading rates other than those typically experienced offshore. The concern is that high strength structural steels with high yield-to-tensile ratio >0.90 are obtained at the expense of ductility and strain-hardening capacity. In this paper the tensile properties from two high strength structural steels were studied and characterised over a range of strain rates and, the results are compared against the performance of mild steel. High strength structural steels with yield-to-tensile ratios in excess of 0.90 were significantly less sensitive to the effect of strain rate than mild steel with yield-to-tensile < 0.85 at ambient temperature. The yield stress of S690QL and S960QL moderately increase to about 9% and 6% respectively from quasi-static to 100 s-1 strain rate, which is within typical strain rates encountered in primary offshore structural applications.