Size characteristics of fragments from expanding cylinders subjected to internal explosive detonations

In order to study the micro-fracture mechanisms of metal cylinders and the methods for predicting fragment scale relations, the correlation between the formation of circumferential and axial cracks in explosively driven metal cylinders and the fragment scale parameter (characteristic mass) μ was analyzed. Previous classical theories and studies only focused on the circumferential scale relations of fragments, but there is no reliable theoretical model for the formation and distribution of axial cracks. Three new types of high-strength, high-fracture steel were prepared by varying the B content and made into metal cylinders for underwater explosion fragmentation tests, obtaining the mass distribution and scale parameters of the fragments. Numerical simulations were used to study the fracture process of explosively driven cylinders, establishing the relationship between strain rates and fracture modes. Based on the statistical characteristics of grain size obtained by electron backscatter diffraction (EBSD) tests, the reasons for the different size characteristics of fragment groups in axial and circumferential directions were revealed. The combined effect of the two fracture modes on fragment size characteristics, along with the differences in circumferential and axial distributions, led to the scale parameter differences of fragments in these two directions. In this study, the fragmentation scale relations based on the microstructure were explained through fracture mechanics, and the results provide support for the establishment of a more accurate fragment scale calculation model.