本文通过应力分析及材料性能试验,查明了活塞套过桥圆角处开裂的原因,并提出柴油机变工况所引起的交变应力是导致裂纹扩展的主要原因。综合断裂分析和运用统计的结果,给出了裂纹活塞运用的临界尺寸,从而为延长柴油机的使用寿命提供了理论依据。 In this paper, through the stress analysis and material property test, the cause of the crack in the fillet of the piston sleeve is found. It is also pointed out that the alternating stress caused by the variable working condition of diesel engine is the main cause of crack propagation. Comprehensive fracture analysis and the use of statistical results, given the critical size of the cracked piston, thus providing a theoretical basis for extending the service life of diesel engine.