发动机自由涡轮叶片裂纹分析

发动机在持久试车例行定检孔探时发现自由涡轮叶片上有一条疑似穿透性裂纹，通过对其进行磁流、荧光检测发现，在一叶片尾缘处有一条长度为5~7 mm的裂纹。对发动机进行分解、零件荧光检测发现多片叶片均存在裂纹。采用宏观检查、断口分析、金相剖切等手段，对裂纹叶片开裂性质进行确认，并对自由涡轮叶片的开裂原因进行分析及验证。结果表明，自由涡轮叶片裂纹性质为疲劳开裂。采用有限元软件对自由涡轮叶片进行振动计算及载荷谱复查，结果表明，由于试车载荷谱发生改变，转子与叶片在工作转速范围内形成共振，造成叶身高阶弯曲疲劳裂纹。

Crack Fault Analysis for Free Turbine Blade of Certain Engine

During the long test to a routine inspection of borescope detection of engine, a suspected penetrating crack on the free turbine blade was dected by conducting magnetic flux and fluorescence fault confirmation. There was a crack with a length of 5~7 mm at the trailing edge of one blade. After returning to the plant for decomposition and fluorescence examination, cracks were found in many blades. Though the macroscopic examination, fracture analysis and metallographic dissection of the cracks, the cracking properties of free turbine blades are determined, and the cracking causes of free turbine blades are analyzed and verified. The results show that fracture of free turbine blade belongs to fatigue cracking. From the calculation and load spectrum review of free turbine blades, it shows that the rotor couplings resonance with the blades within the working speed range due to the change of load spectrum in the long test, which results in the blade height bending fatigue crack.