Strain‐Rate Sensitivity of Mild Steel Grade St52‐3N

A study is made of the effect of strain rate on the strength of St 52‐3N mild steel, commonly used as deck plating in offshore structures. Stress‐strain curves are obtained in both tension and torsional shear at room temperature at strain rates from ${10}^{-4}{s}^{-1}$ to ${10}^3{s}^{-1}$ and compared with previous work on mild steel. The tensile data show that the lower yield stress is approximately twice as strain rate sensitive as stresses in the hardening region and that the ultimate tensile strain is approximately unaffected by strain rate effects up to a strain rate of $20s^{-1}\text{.}$ The torsion data extends to large strains (300%) and shows adiabatic thermal softening at the higher strain rates. The tension and torsion data show that the von Mises yield criterion overestimates the flow stress in pure shear. The material data have been used in determining the penetration resistance of deck structure to dropped objects such as drill collars and it has been found that strain rate effects are of minor importance for the structural response and can be neglected in design.