Study on the effects of gun barrel vibrations on the firing angle of a projectile

The problem of longitudinal and transverse vibrations of an artillery gun barrel during firing is considered. Unsteady stress-strain equations for the gun barrel are solved together with equations of internal ballistics. Ballistic parameters and dynamics of the projectile motion inside a gun bore are determined using a thermodynamic approach. Formulation of the vibration problem accounts for the initial gravitational deflection of the barrel, mass forces, varying distribution of the propellant gas pressure, and the effect of moving projectile mass on gun barrel vibrations. To solve the equations for longitudinal and transverse gun barrel vibrations, difference schemes are obtained by integro-interpolation method. It has been revealed that the solution to the problem in a one-dimensional formulation is almost as accurate as the results obtained in a three-dimensional formulation. Moreover, the former case is significantly less time consuming. The decay time of the barrel longitudinal vibrations after shot is shown to be much less than the time between shots in the burst. Deviations of the transverse barrel vibrations from the initial firing angle are more significant, and the vibration decay time is longer than the time between shots, which affects the accuracy of single shots and the dispersion of shells in the burst mode. Thus, when firing from a 30 mm gun at the range of 1 km, lateral vibrations lead to a change in the height of target hit point by 8.7 m.