Post-Impact Hardness Characterization and Strain Hardening Behaviorof Astm A36 Steel Subjected to High-Speed Impact Loading

Abstract

ASTM A36 steel is widely used in structural and industrial applications due to its favorable combination of strength, ductility, weldability, machinability, and low cost. Understanding the behavior of A36 steel under high-speed impact loading is important for applications involving dynamic loading, penetration resistance, and structural integrity. This study investigates the post-impact hardness characteristics of ASTM A36 steel specimens subjected to ballistic and forced entry loading conditions. Impacted steel plates were recovered following controlled penetration testing and subsequently prepared for microhardness evaluation using the Vickers hardness method.

The results revealed substantial hardness variations throughout the impacted regions, indicating localized plastic deformation and strain hardening. Measured hardness values ranged from approximately 120 HV0.5 in minimally affected regions to over 200 HV0.5 near penetration and severe deformation zones. The increase in hardness is attributed to localized work hardening caused by high strain rates and concentrated plastic flow during impact. Areas immediately adjacent to penetration sites exhibited the highest hardness values, while regions farther from the impact locations retained hardness values closer to the original material condition.

The findings demonstrate that ASTM A36 steel responds to dynamic loading primarily through plastic deformation and strain hardening rather than brittle fracture. Post-impact hardness mapping provides valuable insight into deformation mechanisms, energy absorption behavior, and localized material response under extreme loading conditions.