火炮身管疲劳断裂试验和数值模拟研究

An Experimental and Numerical Study of Gun Barrel Fatigue Fracture

烧蚀磨损和疲劳是影响火炮身管寿命的主要因素,前者使内膛表面产生了随机的烧蚀坑或微裂纹,形成了大量的应力集中区,在疲劳作用下,微裂纹沿身管径向由内向外扩展形成宏观裂纹,一旦其深度达到临界值,继续发射则可能导致身管断裂。针对身管疲劳断裂问题,根据火炮发射过程中载荷作用特点,自主设计了液压冲击疲劳试验装置,在实验室条件下再现了身管服役条件下的疲劳断裂现象。试验结果表明:冲击载荷作用下,身管疲劳断口包括裂纹源、扩展区和瞬断区3个部分,扩展区呈现典型的“海滩条纹”特征;身管外壁面周向应变的演化规律与裂纹的扩展速率变化规律之间存在内在的映射关系,从而可为身管健康监测、发射安全性评估提供新的技术手段。数值模拟采用J-C方程描述炮钢材料的动态本构关系,将材料的应变率效应纳入仿真计算过程中,模拟结果与试验结果之间具有较好的一致性。

Erosion,wear and fatigue have great influence on gun barrel life.The former produces random erosion pits or micro-cracks on the gun bore surface during the firing,forming a large number of stress concentration zones.Under the action of fatigue,micro-cracks expand from the inner surface to the outer surface along the radial direction of the gun barrel and become macro-cracks.Once a crack reaches the critical size,the gun barrel will probably fracture after continuing firing.A hydraulic impact fatigue device was designed and fatigue fracture of gun barrel was reproduced in laboratory conditions by a series of simulated tests.The results show that the fatigue fracture under the impact includes load crack source,crack propagation zone and fast-fracture zone.The crack propagation zone presents typical beach fringes.There is an inherent mapping relationship between the evolution law of the peri-meter strain on the outer surface of the barrel and the crack propagation rate.This provides a new method for health monitoring and launch safety evaluation of gun barrel.The Johnson-Cook equation was adopted to describe the dynamic constitutive relation of the gun steel and the strain rate effect was taken into account in the simulation.The simulated results have a good agreement with the experimental results.