Research On The Shell Breaking Of A Large-caliber 12.7mm Heavy Machine Gun

Transverse rupture of cartridge case is a big problem,as it deprives a machine gun of its combat effectiveness temporarily,which affects the equipment’s strike capability badly.Targeting on the failure of transverse rupture of cartridge case of 12.7 mm API fired by a certain type of 12.7 mm heavy machine gun,locking clearance dimension chain model of the gun is established,and the locking clearance that affects transverse rupture of the cartridge case is analyzed and calculated in this thesis.Mechanics model and strength calculation model of cartridge case in locking state are established,and the relationship between the axial deformation amount in the chamber of the projectile case and the cartridge case diameter,initial radial clearance,cartridge bottom gap,material strength of cartridge case,and deformation of locking mechanism is provided,and the concept of cartridge case deformation clearance and rupture criterion are introduced through stress analysis of projectile case during shooting.And interior ballistic theory model of 12.7 mm cartridge is established,and the acting load of cartridge case is determined through calculation.Based on elastic-plastic mechanics and finite element method,calculation model of projectile bore system is established,overall stress of 12.7 mm projectile bore system is calculated through nonlinear finite element method,and the impact of friction coefficient and locking gap change on static and dynamic responses of projectile bore is determined by calculation.Based on qualitative and quantitative analysis,four solutions againsttransverse rupture of 12.7 mm API fired by this type of machine gunis put forward and the engineering verification is then performed,and the problem is thus solved.The effect of locking clearance on the rupture of projectile case and the controlling factor are concluded based on theoretical analysis and practice of various technical schemes,which provides theoretical and practical basis for analyzing the problem of the rupture of projectile case.