某风力发电公司的变桨轴承螺栓在使用半年后发生断裂。采用金相检验、化学成分分析、硬度测试及断口分析等方法对该螺栓断裂的原因进行了分析。结果表明:裂纹起源于螺帽与螺杆连接的犚角处,该处为应力集中部位,在螺栓松动后,垫片在交变载荷的作用下不断撞击螺栓犚角处并在螺杆表面造成损伤,当损伤达到一定程度后,再加上螺杆表面存在脱碳现象,造成表面裂纹的萌生,裂纹在交变载荷的作用下扩展,导致螺栓发生疲劳断裂。

Some pitch bearing bolts broke after using for six months in a wind power company. By means of metallographic examination, chemical composition analysis, hardness testing and fracture analysis, the fracture reason of the bolts were analyzed. The results showed that the cracks originated at the R corner between the nut and screw, where was the stress concentration position. After the bolts loosed, the gasket impacted the R corner of bolt and damaged the surface of screw under the alternating load. When the damage reached a certain level, and there was the decarburization phenomenon on the surface of screw, resulted in the initiation of surface crack, and the cracks extended under the alternating load, at last the fatigue fracture occuredin bolts.