某机第4级压气机转子叶片榫头折断故障分析

阐明了某机第4级压气机转子叶片在榫头部位断裂的故障特点。故障分析表明：经长期使用的叶片在修理厂大修时，为满足叶片摆动量要求在榫头底面涂尼龙胶，会使叶片自振频率有较大幅度下降；为排除3级叶片折断故障而提高的慢车转速又缩小了4级叶片的共振裕度，结果造成少数4级叶片落入慢车共振。共振发生时，不规则的尼龙胶和装配过程不规范引起的非正常接触容易导致微动磨损的加剧，从而大大降低了疲劳寿命，这是引起榫头断裂故障的主要原因。

An Analysis on Break Failure at Dovetail of the 4th Stage Compressor Blades of an Engine

The failure characteristics of compressor blade break at dovetail position. are introduced in this paper.Analysis based on the failure characteristics indicates that the nylon gum on bottom of dovetail and the long term operation can significantly reduce the natural frequency of blade. Nylon gum was coated on bottom of the dovetail to satisfy blade swing limit during overhaul. Also, the increased idle speed for eliminating failure of the 3rd stage blade has reduced the resonance margin of the 4th stage blade. As a result, a few of the 4th stage blades fell into the idling resonance. While resonance arising, irregular coating of nylon gum and imperfect contact between dovetail and groove from assembling lead to intensive micro motion abrasion. Thereby, the fatigue strength of the blade decreases dramatically. This is the essential reason of dovetail break.