Influence of impact velocity and impact attack angle of bullets on damage of human tissue surrogate —— ballistic gelatin

PURPOSE: Terminal performance of a bullet in human body is critical for the treatment of gunshot injury and optimization of bullet design. The effects of the impact velocity (v(0)) and the impact attack angle (δ(0)) of the bullet on its terminal performance was investigated, using a new evaluation method (called expansion method) based on the expansion of cracks and the permanent cavity wall in ballistic gelatin. METHODS: Ballistic gelatin was used to simulate human body. The 7.62 mm × 39 mm rifle bullets with different v(0) (600–760 m/s) and δ(0) (0°–6°) were fired into the gelatin blocks. The gelatin block was cut into slices of about 20 mm thickness. The cracks and the permanent cavity on each slice were obtained manually. The damaged gelatin was determined using two methods: expanding the permanent cavity but ignoring the cracks, and expanding both the permanent cavity and the cracks. The relations between the damaged gelatin and v(0) and δ(0) were obtained using linear fitting method. RESULTS: According to the distribution of the damaged gelatin along the penetration depth, the damaged gelatin block could be divided into two parts: the less damaged part and the severely damaged part. The length of the less damaged part depends mostly on δ(0); while the average damaged area of this part depends on both δ(0) as well as v(0). The cracks contributed significantly to the total volume of damaged gelatin, particularly when the expansion was larger than 1.9 mm. The total damaged gelatin increases with v(0), δ(0) and the expansion extent. The average length of equivalent cracks grew with v(0) and δ(0) when considering the cracks, and decreased with v(0) when ignoring the cracks. CONCLUSION: The expansion method is suitable to investigate the influence of different factors of bullets on their terminal performance. The characteristics of the damaged gelatin have a linear relationship with the initial attack angle (δ(0)) and the initial velocity (v(0)) of the bullet.