Debris dispersion analysis for the determination of impact conditions via traceback technology

A method for predicting the initial impact conditions including projectile shape and impact velocity is presented through analysis of the dispersion characteristics of debris by means of a traceback methodology. For the determination of the impact conditions, the diameter of the penetration hole in the target, and the dispersion area of the debris on the witness plate were investigated. Based on the results, the projectile configuration defined by the nose angle (NA) and the length to diameter ratio (L/D) together with the initial impact velocity was obtained. NA is associated with the penetration diameter DP and also debris dispersion diameter D50. D50 means 50% containing debris of all dispersions from the center of witness structure. Furthermore, L/D is related to DP and D95, in which D95 is the dispersion diameter containing 95% debris. The projectile diameter can be determined by the relationship between the projectile shape (NA and L/D) and debris dispersion (D50 and D95). Meanwhile, the shape factors identified from the contact surface between the projectile and the structure were designed to modify the de Marré's ballistic limit equation. From the results, it was found that DP increased linearly with increasing impact velocity, and the slopes of DP against impact velocity also increased as NA increase. The initial velocity has been then finally determined by the DP-impact velocity slope and the modified de Marré's equation. Based on the methodology, the shape and initial impact velocity of the projectile could be predicted within 5% error.