A modified Holmquist‒Johnson‒Cook (HJC) constitutive model and its application to numerical simulations of explosions and impacts in rock materials

The Holmquist‒Johnson‒Cook (HJC) model is a commonly used constitutive model for simulations of the dynamic response and damage characteristics of geotechnical materials under explosions and impacts. However, certain deficiencies in its strength, strain rate, and damage models limit its computational effectiveness. Therefore, this paper first introduced the constitutive relation of the HJC. Then, the single-strength equation of the original HJC was improved by adopting three limiting surfaces and considering the impact of the Lode-angle on the yield surface. The hyperbolic tangent function was employed to model the rate effect, and the recommended strain rate parameters for rock materials were provided. Furthermore, an exponential strain softening function-based tensile damage equation was introduced to address tensile damage under negative pressure. On this basis, a method for determining parameters for the modified HJC in rock materials was proposed. Finally, the modified model was incorporated into the LS-DYNA material library using secondary development techniques, and multiple types of impact and explosion experiments on different types of rock materials were simulated using both the original and modified HJC. Additionally, the modified HJC was compared with several other modified HJC versions from various perspectives. It has been found that the simulation results of the modified HJC are in closer agreement with the experimental results than those of the original HJC. Compared to other modified HJC models, the modified HJC proposed in this paper offers a broader range of applications and a better compromise between computational efficiency and the number of parameters.