Typical fracture modes of metal cylindrical shells under internal explosive loading

The competition and coupling of various fracture modes, including tensile fracture, shear fracture and spallation, exist in explosively-driven metal shells. However, the fracture mechanisms and influencing factors of different fracture modes are still unclear. In this study, three typical fracture modes of explosively-driven metal shells–tensile fracture, tensile-shear fracture and shear fracture are numerically revealed by using both the maximum principal strain and the Johnson-Cook cumulative-damage failure criterion. The selection of failure criteria is explained in detail. The fracture strain and fragment morphology are in good agreement with the experimental results. Combined with failure criterion, the numerical results are analyzed from the perspective of pressure, stress and strain. It is found that the formation of different fracture modes depends on the competition between the shear failure formed in the inner surface of the shell and the tensile micro-cracks formed in the middle of the shell. To further investigate the influencing factors of different fracture modes, three dimensionless parameters affecting the fracture modes are proposed based on dimensional analysis. In addition, by analyzing 29 sets of experimental data, we propose the dimensionless equations that can control different fracture modes. And the distribution diagrams of three typical fracture modes (tensile, tensile-shear and shear fracture) of explosively-driven metal shells are determined. Furthermore, we propose a parameter that can effectively distinguish adiabatic shear fracture from non-adiabatic shear fracture.