发动机球墨铸铁连杆疲劳强度分析

Analysis on Fatigue Strength of Nodular Cast Iron Connecting Rod in Engine

发动机连杆采用高强韧性球墨铸铁制造。介绍了采用小子样升降法试验该种发动机球墨铸铁连杆疲劳强度的方法和结果，预测了不同存活率下连杆的疲劳强度，分析了疲劳断口特征，指出夹渣、气孔和疏松等铸造缺陷是造成连杆失效的主要原因，如不存在铸造缺陷，疲劳裂纹起源于工字筋中心的显微疏松处。

The engine connecting rod is made by a nodular cast iron with high strength and toughness. This paper describes the methods and results of testing the fatigue strength of engine nodular cast iron connecting rod by small sub－sample lift and drop method, predicts the fatigue strength of connecting rod under different survival rates and analyzes the character of fatigue rupture notch. It is noted that the casting defects like inclusions, gas holes, looseness and etc. are main factors to cause the failure of connecting rods. The fatigue cracks sourced in looseness location in micro－structure of I shape rib center if casting defects do not exist.