Dynamic mechanical behavior and the constitutive model of concrete subjected to impact loadings

Based on the theory of consecutive damage mechanics, micro-mechanics, statistics and the visco-plastic constitutive equation of Perzyna, a coupled model of damage and plasticity is developed to describe the complex behavior of concrete subjected to impact loadings. In this model, some suppositions about deformation of the material and evolution of the damage are made. First, concrete is macroscopically assumed to be homogeneous and consecutive, while it is microscopically filled with large amounts of micro-crack and micro-void defects. Second, the damage evolution of the micro-cracks is caused by the nucleation, growth and coalescence of the micro-cracks due to the interior tensile stress in concrete, which leads to a degradation in the strength and stiffness of concrete. Third, compaction of concrete is physically a collapse of the material micro-void. It produces irreversible plastic strains in the material and, at the same time, an increase in the bulk modulus. Fourth, there is no interaction between the micro-crack and the micro-void. Last, when the damage reaches a critical value, the concrete may fail totally. The model parameters for concrete are determined by plate impact experiments. The model predictions fit the experimental results well. So the model can be used to simulate the dynamic mechanical behavior of concrete under impact loadings.