弹体贯穿混凝土数值模拟的改进材料模型

Investigating the mechanical property of concrete structures subjected to impact loading has great significance on the design and evaluation of weapons and protective structures, while appropriate material models can more accurately predict the mechanical behavior and damage mode of concrete structures. In this paper, an improved damage-plasticity material model for concrete was proposed to describe its mechanical response subjected to impact loading. The equation of state, including elastic stage, transition stage and compacted stage, is employed to describe the pressure vs. volume strain relationship. The strain rate effect is considered by combining the radial enhancement method and the semi-empirical equation of dynamic increase factor. A unified hardening/softening function related to the shear damage caused by microcracking and the compacted damage caused by pore collapse are introduced to describe the nonlinear ascend and descend of compressive strain-stress curves in plastic stage, while an exponential function related to the tensile damage is employed to reflect the strain softening behavior under tension. Based on the current extent of damage, the failure strength surface of this improved material model is determined through linearly interpolation between the maximum and yield strength surfaces or the maximum and residual strength surfaces, and the influence of third deviatoric stress invariant on the failure strength surface is considered for describing the reduction of shear strength during the transition from high pressure to low pressure. The fractionally associated flow rule is employed to consider the volumetric dilatancy of concrete materials under confining pressure. Then, the availability and accuracy of this improved material model are verified by the numerical simulations of single element under different loading conditions, and its performance improvement is discussed by comparing with the HJC model, RHT model, Kong-Fang model and empirical equation. Finally, the numerical simulations of projectile perforating reinforced concrete slab are conducted to further validate the feasibility and accuracy of this improved material model under impact loading, from which numerical results indicate that the damage mode and residual velocity predicted by this improved material model are closer to experimental results than HJC model.