Abstract: The influence of bore damage on interior ballistic performance and muzzle-leaving state of bullet is studied, and the mechanism of how bore damage leads to the end of barrel's life is explored. The accurate thermo-mechanical coupling finite element analysis (FEA) models of barrels with bore damage at different life periods are established based on the distribution and evolution rule of bore damage obtained through systematic life tests. The changing rules of interior ballistics performances and muzzle-leaving states of 12.7 mm bullet with the evelopment in bore damage are obtained through numerical simulation which combines the interior ballistics process and the explicit finite element method through Fortran subroutines. The coupling model of bullet and gun barrel is proved to be effective by comparing the calculated results of interior ballistic parameters with experimental results. The simulated results show that the initial disturbances of bullet at muzzle, the reduction in rotational velocity and the variation in bullet's surface topography increase as the firing cycle increases, especially in barrel's later lifetime. Variation in muzzle-leaving state of bullet is the key factor for barrel's life end. Research results have important significance on further studying how bore damage degrades bullet's exterior ballistics performance and the end-of-life mechanism of barrel. Key

Key words: barrellifetest, boredamage, interiorballisticsperformance, muzzle-leavingstate, finiteelementmethod