Experimental research and constitutive modelling of LYP160 steel considering the strain rate

Monotonic and cyclic loading experiments were carried out on LYP160 steel specimens at five loading strain rates to explore the influence of different strain rates on the mechanical properties. Monotonic tensile tests indicated that the yield strength of LYP160 steel was relatively low and the stress-strain curves did not exhibit a discernible yield plateau. As the strain rate increased, both the yield strength and the ultimate strength of the specimens increased. Specifically, the yield strength of the steel at a strain rate of 0.1 s(-1) can reach 1.77 times that at a strain rate of 0.001 s(-1). The hysteresis curves of the LYP160 steel specimens were full, exhibiting mixed hardening behaviour of isotropic hardening and kinematic hardening, which differed significantly from the response to monotonic loading. With increasing strain rate, the cyclic hardening effect of the specimens increased, leading to an increase in the hysteresis curve area; consequently, the isotropic hardening behaviour was more significant. At higher strain rates, such as 0.05 s(-1) and 0.1 s(-1), the cyclic softening effect of the specimens occurred earlier and to a greater degree. Using the Cowper-Symonds model, equations were presented to calculate the influence of the loading strain rate on the yield strength and ultimate strength, and a modified Chaboche constitutive model related to the strain rate was proposed. The efficacy of the modified Chaboche model was validated by comparing finite element simulation results with experimental hysteresis curves and strain distributions measured by digital image correlation.