Theoretical analysis of influence of pore collapse behavior on shock compression characteristics of porous materials

Porous materials exhibit pore collapse behavior during impact compression. Based on the shock wave structure observed in experiments carried out by predecessors, a theoretical analysis of the relationship between the shock wave formation process and the pore collapse behavior of porous materials is conducted. Firstly, considering the compression curve characteristics of porous materials and the overtaking of shock waves, it is proposed that the shock wave structure of porous materials has three modes: low-pressure single wave mode, double shock wave mode, and high-pressure single wave mode. These different shock wave modes are mainly caused by the influence of elastic-plastic mechanical behavior in pore collapse on the compression curve of porous materials. Furthermore, combined with the Wu-Jing equation of state, the calculation method of shock compression characteristics compatible with different shock wave modes is developed. The relationship between the Hugoniot curve of porous material and dense material is established, and the calculation equation of impact specific volume compatible with single shock wave mode is obtained, which can directly calculate the critical specific volume without approximate conditions. In addition, the equation of pore collapse established by Carroll is modified by taking the linear approximation of the variation of porosity with pressure in the elastic stage and the elastic-plastic stage and considering the relationship between the stress of the matrix material and the macroscopic stress in the porous material. Based on the calculation model of shock compression characteristics considering pore collapse behavior, the Hugoniot data of the material are calculated, and the influence of pore collapse behavior on the shock compression characteristics of porous materials is discussed. The results show that the shock compression characteristics of the material are significantly affected by the pore collapse behavior at lower pressures, and the model in this paper can predict the shock wave parameters of porous materials more accurately.