Damage Limit Velocity and Fracture Patterns in Single Glass Plates Impacted by Steel Balls of Varying Diameters

Slingshots, traditionally viewed as children’s toys, have recently been modified for malicious purposes, including firing steel balls at building windows, causing significant damage. This misuse necessitates the development of methods to estimate impact velocity and launch point based on glass damage patterns at incident scenes. To achieve this, a comprehensive database correlating glass damage shapes with steel ball diameters is essential. This study conducted experiments to investigate the damage patterns of 5 mm thick glass upon impact with 8 mm and 10 mm steel balls. The damage limit velocities for 8 mm and 10 mm steel balls to cause damage to 5 mm glass were approximately 40 m/s and 21 m/s, respectively. Glass damage was categorized into two types: cone cracks and perforated holes. While cone crack patterns were similar for both 8 mm and 10 mm steel balls, perforation patterns exhibited distinct tendencies. Consequently, the impact velocity of each steel ball can be estimated based on the size of the perforated hole. However, determining the steel ball diameter solely from the size of the cone crack and perforated hole remains challenging.