某型号柴油机试验过程中止推杆在短时间内相继多次发生断裂,通过宏观分析、化学成分分析、金相检验以及断口分析等方法对止推杆的断裂原因进行了分析。结果表明:导致止推杆断裂的主要原因是止推杆退刀槽处设计为内犚,过渡圆弧半径较小且犚处加工质量较差,工作时在犚处引起较大应力集中,萌生疲劳裂纹源,随着柴油机运行裂纹不断扩展,直至断裂。

Multiple fractures in short time happened to a type of diesel engine push rods in the process of test, and means such as macroscopic analysis, chemical compositions analysis, metallographic examination and fracture analysis were used to analyze the fracture reasons of the push rods. The results show that the main cause for the fracture was that the undercut of the push rod was designed for inner R form, at the same time the transition arc radius was rather smaller and the machining quality of the R position was poor. When working, the R position would form serious stress concentration and produce fatigue cracks which continuously expanded until the push rod fractured.