Dynamic tensile behavior and rate-dependent constitutive model of 304 + Q235 bimetallic steel

This paper aims to elucidate the rate-dependent behavior of 304 + Q235 bimetallic steel under intermediate strain rates. Tensile tests were conducted on 18 sets of specimens to obtain the engineering stress-strain curves at various strain rates. The experimental results demonstrate that the strain rate significantly influences both the yield strength and ultimate strength of the 304 + Q235 bimetallic steel, albeit with different trends. The yield strength exhibits an upward trend with increasing strain rates, whereas the ultimate strength demonstrates a downward trend. Additionally, the strain-hardening effect diminishes proportionally with the increase in strain rate. The parameters of the Cowper-Symonds model associated with the dynamic yield strength increase factor (DIF_y) were determined based on the experimental findings. A bilinear rate-dependent constitutive model was established to accurately predict the dynamic ultimate strength increase factor (DIF_u) of 304 + Q235 bimetallic steel. The established bilinear model was utilized to enhance the Johnson-Cook model for accurate prediction of the true stress-strain behavior of 304 + Q235 bimetallic steel under intermediate strain rates. The calculated results obtained from the modified Johnson-Cook model exhibit good agreement with the experimental results.