Rate-dependent constitutive models of S690 high-strength structural steel

The demand of applying high-strength structural steel (HSSS) in engineering practice is progressively increasing, while insufficient research achievements of HSSS restrict its applications, especially for those under dynamic loadings. Therefore, to meet the increasingly demand of studies for HSSS at high strain rates, a grade of HSSS, S690 was experimentally investigated by quasi-static tensile tests and dynamic tests using a Split Hopkinson Pressure Bar (SHPB). The dynamic yield strength and stress-strain curves at various strain rates were obtained, which showed that S690 has obvious effects to the sensitivity of strain rate, while the existing models are not suitable for predicting its strain-rate effect. Further, the dynamic increase factor (DIF) of yield stress was determined and a new Cowper-Symonds model was fitted to predict the DIF precisely. To establish a rate-dependent constitutive model for S690, the Johnson-Cook (J-C) model was also adopted to fit true stress-strain curves and has been proved to perform acceptable prediction accuracy. By substituting the strain-rate parameter C, the standard J-C model was modified to improve its precision. These test results may provide fundamental data for its future studies, and the constitutive models may be applied to analyze the dynamical performance of S690 components. (C) 2018 Elsevier Ltd. All rights reserved.