Abstract: A surface pressure model is presented to study the translational and tumbling motions of rifle bullets penetrating into ballistic gelatin. In the model, it is assumed that each area element is under the action of normal dynamic pressure and material resistance. The resultant force and moment on a projectile are obtained through numerical integration of surface pressure. The trace of a projectile is calculated by solving spatial motion equations deduced from the mass center motion equations and Euler equations of motion with Runge-Kutta method when the initial conditions are given. A 7.62 caliber bullet is tested to verify the surface pressure model. The agreements between the theoretical results and experimental data including displacements and projection angles show that the model is applicable in predicting the translational and tumbling motions of rifle bullets.

Key words: ordnance science and technology, surface pressure model, rigid projectile, gelatin