Calculation of the total force acting upon a rigid wall by projectiles

Abstract A numerical method is presented which allows for the calculation of the total force acting upon a building during impact of a projectile. The structural part to be hit by the projectile is assumed to be rigid; its surface is perpendicular to the direction of impact. Flight trajectory and projectile axes coincide. Variations of geometric and material properties across the projectile axis are replaced by proper average values. The computation algorithm is based on a difference method. The projectile model has to be divided into elements along the flight trajectory. Except for the elements at the beginning and end of the projectile each element is in equilibrium with its neigbour elements. Different elastic and plastic material properties for each element can be taken into account. Strongly deformed elements are assumed to become separated from the projectile. The impact of all debris is calculated as a part of the total force acting on the wall. The method is tailored to safety considerations. A parametric study of the force resulting from impact of a turbine of a military aircraft is discussed. It is shown that for safety considerations a simplified function between force and time can be established.