枪管内膛损伤对弹头外弹道过程的影响研究

为研究枪管内膛损伤对弹头气动特性及外弹道过程的影响，基于系统的12.7 mm机枪枪管寿命试验获得的内膛损伤规律，建立了损伤枪管的有限元模型并获得了枪管在4个寿命阶段所发射弹头的表面形貌状态.采用基于剪应力输运（SST）k-ω湍流模型的计算流体力学（CFD）方法对不同表面形貌的高速旋转弹头的气动参数进行了数值计算.采用均匀设计方法安排随机因素影响下的弹头内弹道计算过程，获得了各阶段弹头膛口扰动随机响应状态.建立了弹头6自由度刚体外弹道模型，结合弹头的气动参数和膛口扰动状态对弹头外弹道过程进行编程求解，获得了100 m处各寿命阶段枪管所发射弹头的散布圆半径和椭圆弹孔率，最终计算结果与试验数据吻合较好.计算结果表明:弹头初始扰动在枪管寿命末期的迅速增大，以及大攻角下弹头所受气动力压力中心的前移和马格努斯力矩的增大等，是造成枪管寿命末期弹头飞行稳定性降低及枪管迅速寿终的主要原因. 

The Influence of Bore Damage on Bullet's Exterior Ballistics Process

In order to study how the damaged bore influences bullet's aerodynamic characteristics and the exterior ballistics process, finite element models of damaged barrels at 4 life were established based on systematic life tests of 12.7 mm machine gun barrels to obtain bullets' surface morphologies at the muzzle. Simulations of the aerodynamic parameters for the high-speed spinning bullets with different surface morphologies were carried out adopting the computational fluid dynamics (CFD) method with the shear stress transport (SST) k-ω turbulent model. Uniform design method was used to arrange the interior ballistics computing process influenced by random factors, and the random response states of bullets' disturbances at the muzzle were acquired. A model of 6-D exterior ballistics of rigid bullets was set up, and the numerical calculation software was programmed combined with bullets' aerodynamic parameters and muzzle disturbances. The simulated results of the dispersion circle radius and the ratios of elliptical bullet holes of bullets shot from the barrels at 4 life fit well with the experimental data. The computed results show that the increase of bullets disturbances at muzzle, and the antedisplacement of pressure center of aerodynamic forces as well as the increase of Magnus moment coefficient are the major reasons for the decrease of bullet's flight stability and the terminal of a barrel's later life.