叶片组轴向模态共振失效的理论与实验研究

为了找出叶片的失效机理及解决的办法，利用金相、扫描电镜等分析手段，从宏观和微观的角度对叶片及断口进行了观察和分析；用三维有限元法和实验方法对其振动特性进行了研究。分析得出：造成叶片开裂是由于叶片组第2类轴向振动模态和喷嘴叶栅出口气流不均匀引起的激振力频率发生共振，导致叶片高周疲劳造成的。叶根齿表面加工粗糙是裂纹起裂的一个重要诱发因素。采用不改变叶型，仅调整叶片组中的叶片数，成功地实现了叶片的改型设计。该研究表明：叶片组的第2类轴向振动模态同喷嘴激振力共振是危险的，应该避免。调整叶片组中的叶片数是调整叶片组轴向固有振动模态的一个有效方法。图6表3参5

Computational and Experimental Research on Blade Failure From Group Axial Model Resonance

To find out the significant cracking mechanism, one of the damaged blades is inspected by macrographic, micrographic and chemical examination method. The natural frequency and model shape are measured by the impact test and calculated by 3-D finite element method. The results of inspection and vibratory behavior analysis show the cracking of the blade finger is caused by high cycle fatigue resulting from resonance of the second type group axial vibration mode with nozzle passing frequency. Surface defect coming from rough machining induces the initiation of crack. Blades in the stage are reformed successfully by adjusting the number of blades in a group without changing the type of vane and dovetail. The study also illustrates the second type group axial mode resonance with nozzle passing frequency is dangerous and should be avoided. Changing number of blades in a blade group is an effective way for tuning the natural frequency of group blades and avoiding the resonance. Figs 6, tables 3 and refs 5.