The effect of bullet yaw on the threat level : a numerical investigation

It is well known that yaw can affect the penetrative power of armour piercing rounds. To investigate this effect purely experimentally is difficult because the typical ballistic set up does not allow control over the yaw angle of the projectile. In this study, a numerical model is used complementing ballistic experiments for a range of yaw angles. For the projectile, a validated computer model of the 30-06 7.62 x 63mm AP M2 round was selected. Surrogate targets were used for a qualitative assessment of the phenomenon. The utilized target is a flat rectangular tile. To encourage yaw in the experimental tests, targets were positioned at relatively close distance to the breach and impact velocity was chosen lower than typical for the projectile. Both ensure that the bullet does not reach stable flight therefore yaw is present. From the experiments, a range of impact velocities and yaw angles was chosen and each of the test conditions simulated. The decrease in bullet velocity ΔV was calculated from high speed video footage captured during tests and compared to bullet ΔV in simulation. Strain condition, predicted damage and negative pressure output from simulation were investigated in pursue of yaw effects on threat level. The results of this study can help in the interpretation of physical test results and ultimately can contribute to making the performance of armour systems more robust