Fracture behavior of plate glasses by projectile impact

Abstract

On crime scenes, plate glass is frequently shot by bullets. The fracture of plate glass by a pachinko ball (steel ball) impact also occurs. Experiments were carried out to obtain basic data for estimating the impact velocities of projectiles from the morphology of the fracture. Projectiles 〈11mm dia. steel balls and 0.38 inch (9mm dia.) lead bullets〉 were shot onto ordinary glass plates firmly held around a circular periphery. It was assumed that projectile kinetic energy would all be converted into surface energy of fractured glass. The relationship between crack area Af and kinetic energy of projectiles was investigated. A strong experimental correlation was found between Af and the change in kinetic energy. A unique relationship was obtained between crack area and energy consumed during fracture regardless of the projectile material (steel and lead).