王厚权，李德华，柳海涛，周伟，徐志远

潍柴动力股份有限公司，山东 潍坊 261061

摘要：针对某船用中速发动机在连杆疲劳试验时连杆大头螺纹孔处发生的断裂故障，分析试验过程和连杆断口形貌及金相组织，对比有限元仿真计算过程中简化全局模型和细化子模型疲劳计算结果；优化连杆材料，改进挤压螺纹工艺，对改进后的连杆进行有限元计算和疲劳试验。结果表明：连杆螺纹孔处结构疲劳强度不足是引起断裂的主要原因，子模型仿真结果与故障模式相吻合；提高连杆材料机械性能、改进连杆加工工艺后，连杆的疲劳强度提高，最小安全疲劳系数由1.05提高到1.35，有效解决连杆疲劳断裂故障。该研究可为解决发动机中受循环负载的关键零部件在螺纹处出现相同故障模式提供参考。

关键词：连杆；疲劳断裂；疲劳安全系数；有限元仿真计算；子模型

Abstract：In the view of the fracture problem of connecting rod′s big screw hole during fatigue test of a marine medium speed engine, the test process, fracture morphology and metallographic structure of fault parts are analyzed. The difference of fatigue calculation results between simplified global model and refined sub-model in finite element simulation are compared, the material of connecting rod is optimized and the extrusion thread process is improved. Finite element calculation and fatigue test are carried out for the improvement of the connecting rod. The results show that the main cause of the fracture is the insufficient fatigue strength at the threaded hole of the connecting rod. The simulation results of the sub-model agree well with the fault mode. The fatigue strength of connecting rod can be improved by improving mechanical properties of connecting rod and connecting rod adding process, the minimum safety fatigue factor is increased from 1.05 to 1.35, and the fatigue fracture of connecting rod can be effectively solved. The improved analysis can provide a reference for solving the problem that the same fault mode occurs in the thread of the key parts of the engine under cyclic load.

Keywords:connecting rod; fatigue fracture; fatigue safety factor; finite element calculation; sub-model