Defence Technology ( IF 5.1 ) Pub Date : 2020-09-12 , DOI: 10.1016/j.dt.2020.09.005 Naveed Hussain , Faisal Qayyum , Riffat Asim Pasha , Masood Shah
In this research, a detailed multi-physics study has been carried out by numerically simulating a solid fractured gun barrel for 20 thermo-mechanical cycles. The numerical model is based on thermal effects, mechanical stress fields and fatigue crack mechanics. Elastic-plastic material data of modified AISI 4340 at temperatures ranging from 25 to 1200 °C and at strain rates of 4, 16, 32 and 48 s−1 was acquired from high-temperature compression tests. This was used as material property data in the simulation model. The boundary conditions applied are kept similar to the working gun barrel during continuous firing. A methodology has been provided to define thermo-mechanically active surface-to-surface type interface between the crack faces for a better approximation of stresses at the crack tip. Comparison of results from non-autofrettaged and autofrettaged simulation models provide useful information about the evolution of strains and stresses in the barrel at different points under combined thermo-mechanical loading cycles in both cases. The effect of thermal fatigue under already induced compressive yield due to autofrettage and the progressive degradation of the accumulated stresses due to thermo-mechanical cyclic loads on the internal surface of the gun barrel (mimicking the continuous firing scenario) has been analyzed. Comparison between energy release rate at tips of varying crack lengths due to cyclic thermo-mechanical loading in the non-autofrettaged and autofrettaged gun has been carried out.
中文翻译:
开发多物理场数值模拟模型,以研究自动加固枪管中的热机械疲劳裂纹扩展
在这项研究中,通过对固体断裂枪管进行 20 个热机械循环的数值模拟,进行了详细的多物理场研究。数值模型基于热效应、机械应力场和疲劳裂纹力学。改性 AISI 4340 的弹塑性材料数据,温度范围为 25 至 1200 °C,应变速率为 4、16、32 和 48 s -1是从高温压缩试验中获得的。这被用作模拟模型中的材料特性数据。在连续射击期间,应用的边界条件与工作枪管保持相似。已经提供了一种方法来定义裂纹面之间的热机械活性表面对表面类型的界面,以便更好地近似裂纹尖端的应力。对非自紧和自紧仿真模型的结果进行比较,可以提供有关两种情况下组合热机械载荷循环下不同点的筒体内应变和应力演变的有用信息。已经分析了热疲劳在由于自增强引起的压缩屈服和由于枪管内表面上的热机械循环载荷(模拟连续射击场景)引起的累积应力逐渐退化的影响。已经对非自紧和自紧枪中由于循环热机械载荷而导致的不同裂纹长度的尖端的能量释放率进行了比较。