Comparative analysis of ductile and brittle fracture modes in high-hardness steel projectiles during impact

This study investigated the impact fragmentation behavior of projectiles with different yield strengths using 45 steel, 35CrMnSiA steel, and T12A steel as core materials. Through experimental and simulation analyses, the fracture mechanisms and damage characteristics of these materials under high strain rate impacts were examined. The results indicated that 45 steel and 35CrMnSiA steel exhibited noticeable ductility, with fracture surfaces showing prominent dimples and shear lips, experiencing significant plastic deformation and necking during impact. In contrast, T12A steel demonstrated brittle behavior, with fracture surfaces characterized by smooth, bright areas and fine radial streaks. In ballistic tests, T12A steel projectiles displayed distinct damage patterns compared to the other two materials due to their brittleness, resulting in shorter residual lengths. The force-time curves obtained from experiments and simulations showed that higher core strength shortened the time to reach peak force and reduced the overall contact duration. However, the high strength of T12A steel was not always associated with higher peak stresses, as its brittle fracture mode led to early instability. Fragment analysis revealed that smaller fragments ( primarily originated from the projectile head, while larger fragments came from the tail. Microscopic examination of the fragments revealed a mix of ductile and brittle fracture modes, with different particle sizes exhibiting distinct fracture surface features. Overall, the study provides insights into the impact performance and failure mechanisms of different core materials, highlighting the importance of material properties in determining projectile behavior under high strain rate conditions.