某型发动机在台架试验中活塞顶部出现开裂, 裙部磨损。对开裂活塞的断口、化学成分、显微组织和硬度等进行了分析, 结果表明: 活塞顶部的开裂为疲劳开裂; 发动机工作过程中冷却不良, 活塞顶面温度过高, 引发了热疲劳裂纹的产生, 在交变燃气爆发高压应力的作用下, 裂纹不断扩展, 最终导致活塞的开裂。

During the bench test of a certain type of engine, cracking on the top surface of piston and wearing in the position of skirt were found. The fracture, chemical composition, microstructure, hardness and so on were analyzed, the results showed that the fatigue cracking appeared on the top surface of piston; the thermal fatigue cracks was caused by insufficient cooling in working and high temperature of the top surface of piston, the cracks extended under high pressure stress of alternating gas, and led to cracking of the piston at last.