Research on dynamic constitutive model of concrete material with different matrix strength under medium-high strain rates
Zhange Bi, Jun Liu, Mingsheng Zhao, Xuejiao Cui
Abstract
The Holmquist-Johnson-Cook (HJC) model is commonly employed as the constitutive model for concrete materials in numerical simulations of medium-high strain rates loading. However, the effect of varying matrix strengths on the determination of strain rate sensitivity parameters and other model coefficients within the HJC framework has not been adequately considered. Therefore, a comprehensive series of dynamic uniaxial compression tests were performed utilizing Split Hopkinson Pressure Bar (SHPB) apparatuses. on four types of concrete specimens with different matrix strengths and six types of strain rate loading. These tests involved four distinct concrete specimens with varying matrix strengths, subjected to six different strain rates, in order to investigate the influence of these variables on the material's response. Multiple regression analysis techniques were employed to curve-fit the dynamic increase factor, with the most suitable formula identified through an optimization process based on perturbation theory. Subsequently, the strain rate sensitivity parameters, along with additional coefficients of the HJC model, were recalibrated. The enhanced accuracy and advancement of the modified HJC model were validated from three aspects: stress-strain curves, failure modes, and dynamic characteristic parameters. The results showed that: (1) the conventional HJC model tends to underestimate the strain rate effects when simulating SHPB tests of concrete with different matrix strengths under medium-high strain rate loading; (2) the Dynamic Increase Factor ( DIFc ) as a function of strain rate, when accounting for matrix strength, exhibits a consistent trend with the strain rate; (3) the modified HJC model effectively simulates the failure process, ultimate failure modes, stress-strain curves, and dynamic characteristic parameters of concrete specimens with different matrix strengths.