Experimental study on fragmentation of explosive loaded steel projectile

To study the natural fragmentation of projectiles, the effects of the fragmentation resistance characteristic, grain size, and metallographic structure of the projectile material on the characteristic masses (scale parameter μ) of the fragments were explored in this study. Thermal treatments were conducted on four types of shell steels to obtain eight materials with different macroscopic mechanical properties and microstructures for quasi-static and dynamic mechanical tests, and the grain sizes and metallographic structures of the materials were observed under a metallographic microscope. An underwater fragmentation test was performed on the explosive projectiles, and the Weibull distribution was used to fit the test data to obtain the mass distribution control parameters of the materials in the eight states. According to the classical Mott and Grady theories, the fragmentation resistance characteristics of the materials in the eight states were calculated based on the mechanical properties of the materials. By comparing and analyzing how the fragmentation resistance characteristic, metallographic structure, and grain size were correlated with the scale parameter, the classical theories were found to have limitations. This study showed that there was a strong correlation between the grain size and scale parameter, and the scale parameter increased with the increase in grain size. Given the same material type and grain size, the metallographic structure was strongly correlated with the fragmentation resistance characteristic. The fragmentation resistance characteristics of the materials with tempered troostite were larger than those of materials with tempered sorbite. Given the same material type and grain size, the classical theories were applicable, i.e., the scale parameter increased as the fragmentation resistance characteristic increased.