热-力循环载荷下身管镀层裂纹扩展规律研究

目的研究身管镀层裂纹的扩展机理,提高身管寿命。方法针对身管镀层裂纹损伤,提出一种基于扩展有限元方法(XFEM)结合内聚力模型(CZM)的方法。建立热–力耦合的镀层身管有限元模型,通过间接耦合的方式,将温度场导入有限元模型,通过CZM本构模型来模拟其损伤失效行为。对镀层初始裂纹在热–力载荷下扩展到镀层/基体界面的情况进行仿真分析。结果在高温高压环境下,镀层初始裂纹扩展速度很快,在第1发射击完成后便扩展到基体结合面,初始裂纹扩展到镀层/基体界面时,裂纹尖端的存在使局部具有较大切应力,达到1180 MPa。在连续射击工况下,造成镀层结合面的开裂。结论在高温高压载荷下,镀层初始裂纹很快扩展到镀层/基体界面,且身管镀层承受的热应力是导致镀层开裂的重要因素。

Crack Propagation Law of Barrel Coating under Thermal Mechanical Cyclic Load

The falling off of the coating is an important factor affecting the service life of the barrel. To improve the service life of the barrel, the propagation mechanism of the coating crack of the barrel is studied. Aiming at the crack damage of barrel chromium layer, a method based on extended finite element method (XFEM) and cohesion model (CZM) is proposed. The thermal mechanical coupling finite element model of coating barrel is established. The temperature field is introduced into the finite element model in the way of indirect coupling. In addition, the strength and damage criterion of the interface between coating and substrate are simulated by CZM constitutive model. The initial crack of the coating extends to the coating/substrate interface under thermal stress load. Under the circumstance of high temperature and high pressure, the initial crack propagation speed of the coating is very fast, and it extends to the substrate joint surface after the completion of the first shot. When the initial crack extends to the coating/substrate interface, the existence of the crack tip makes the location have a large shear stress, up to 1 180 MPa, resulting in the cracking of the coating joint surface under the condition of continuous shooting. Under high temperature and high pressure load, the initial crack of the coating quickly extends to the coating/substrate interface, furthermore, the thermal stress borne by the barrel coating is an important factor leading to the cracking of the coating.