针对某起重机液压缸中的活塞杆在运行过程中发生的疲劳断裂失效,从活塞杆的成分、断口的形貌和实际工况确定裂纹源的位置和形成机理,并对断裂的原因进行分析。结果表明:材料在冶炼过程中留下的夹杂物粒子、第二相粒子及设计不合理造成的过度台阶处的过渡圆角较小,是导致活塞杆应力集中的主要原因,在交变载荷的作用下,最终使活塞杆发生疲劳断裂。 Aiming at the failure failure of the piston rod in a crane hydraulic cylinder during operation, the position and formation mechanism of the crack source were determined from the composition of the piston rod, the morphology of the fracture and the actual working conditions, and the cause of the fracture was analyzed. The results show that the main reason for the stress concentration on the piston rod is the small fillet angle of the inclusions, the second phase particles and the over-step caused by the unreasonable design of the material left in the smelting process. Under alternating load Under the action of the piston rod eventually fatigue fracture occurs.