摘要:
航空发动机机匣包容性问题非常复杂,涉及大变形、材料粘塑性及结构非线性动态响应等。本文以某型航空发动机风扇机匣为研究对象,提出一种结合弹道冲击试验和有限元分析评估机匣包容能力的方法。采用叶片型弹体冲击半环模拟机匣以获取钛合金机匣的冲击损伤基本特性,并基于商业显式有限元软件LS-DYNA建立相应的数值仿真模型,对比弹体剩余速度、靶板径向变形量以及结构损伤形貌的数值仿真结果与试验测试结果,二者良好的一致性表明本文数值仿真方法的准确性。最后,采用验证过的数值仿真方法建立真实断裂叶片撞击风扇机匣的计算模型,研究断叶转速及断叶尺寸对机匣包容性的影响。结果表明,风扇叶片与机匣发生两次主要撞击,第二次撞击对机匣的损伤最大。随着飞断叶片转速的提高,机匣损伤区域变大,塑性变形能迅速增加,但包容能力下降。飞断叶片尺寸主要影响机匣受到的第二次撞击,尺寸越大,相互作用力越大。
Abstract:
The containment process of aero-engine casing is very complex, which involves large deformation, material viscoplasticity and nonlinear dynamic response of structural elements. In this paper, a new method combining ballistic impact test and finite element analysis is proposed to evaluate the containment capability of real aero-engine fan casing. A blade-liked projectile was used to impact the half ring simulator to obtain the impact resistance of the titanium alloy casing. The high-speed cameras were aimed perpendicular to the path to measure pre- and post-impact velocities of the projectile. Using the DIC (Digital Image Correlation) technology to determine the deformation field of the half ring simulator. Based on the commercial finite element software LS-DYNA, a corresponding numerical simulation model was established. The predicted results of the residual velocity of the projectile, radial deformation of the target, and the morphology of structural damage are compared with experimental results. The good agreement between the two indicated the accuracy of the numerical method. Under the low energy impact, the projectile was rebound, and the half ring absorbed energy with bulge. Whereas in the high energy impact, the projectile penetrated the half ring target and result in tear in the rear surface. Finally, the validated numerical simulation method was employed to simulate the real fan blade/casing containment process, and the influence of the blade rotate speed and the blade size on casing containment are studied. The results show that, there were two major impacts between the fan blade and the casing, one is the leading edge of the blade impacts on the casing to form small tear marks, the other is the blade body subjected to the casing causing tear band and bend outward. Obviously, the second impact was the most destructive to the casing. With the increase of the blade rotate speed, the damage area of the casing enlarges, and the plastic deformation energy increases rapidly, thereby diminishing the containment capability. The size of the released blade mainly affects the second impact phase on the casing, with larger sizes resulting in higher levels of interaction forces.