Model for ballistic fragmentation and behind-armor debris

The fracture of the target and projectile during normal penetration is desc ribed using a model of chaotic disintegration modifying the theory of chaot ic disintegration of liquids. The radius of the locally smallest fragment i s calculated equating its kinetic energy of deformation with its surface en ergy of fracture, The probability of lacunae opening in the target and proj ectile materials increases near the target/projectile interface. The percol ation threshold for this probability determines the boundary of the fractur ed zone. When this fractured zone reaches the rear surface of the target th e fragments can leave it. Mass distribution of the fragments was calculated with the help of percolation theory. Then, the shape of the debris cloud a nd the direction, velocity and range of its propagation are calculated to e stimate vulnerability behind the perforated target. The calculations were compared with results of normal impact experiments pe rformed with tungsten sinter alloy rods (D = 20 mm, L/D = 6) against 40 and 70 mm rolled homogeneous armor (RHA) at an impact velocity of 1700 m/s [1, 2]. For observation of the bulging, breakup and fragmentation of the bulge as well as debris cloud formation and expansion, flash X-ray and laser stro boscope techniques have been applied, From the X-ray photographs and soft r ecovery tests the shape of the debris cloud and velocity field of the fragm ents as well as the fragment number and mass distributions have been determ ined, respectively. The calculations predict well the experimental data. (C ) 2000 Elsevier Science Ltd. All rights reserved.