Abstract: For the affecting factors and change rules of the gap in open tail seat during the high-pressure gun launch, LS-DYNA software is used to simulate the internal ballistics of a typical extended-range ammunition with a common tail. The dynamic response at every moment in internal ballistics was obtained. The muzzle velocity and rotation speed at the muzzle are in good agreement with the test data. The axial compressions of engine support, engine shell and warhead base, and the change rule of gap between the tail fins and the warhead base under different yield strengths and preloads are analyzed. The results show that the axial compressions of the engine support, shell and warhead base increase first and then decrease, which is consistent with the bore pressure-time variation; the engine shell has a greatest effect on the gap between tail fin and warhead base, and the proportion reaches 78.2% in total compression; when the yield strength of engine shell reduces to 800 MPa, the total compression caused by the elastic deformation of common tail exceeds the gap between tail and warhead base, resulting in collision on the base. When the preloads are abnormal, the gaps between each tail and the base is not synchronized and up to 17.3% of the initial gap, causing the deep and shallow collided marks.

Key words: high-pressuregun, commontail, gapinbore, yieldstrength, preloadstate, numericalsimulation