发动机连杆断裂失效分析

Failure Analysis of Engine Connecting Rod

连杆作为发动机动力输出的关键零部件之一,直接影响和决定了发动机的可靠性和耐久性。本文基于某型号发动机台架试验时出现连杆断裂,从宏观和微观的角度进行失效分析,最终找到连杆断裂的原因,并针对性提出改进措施。分析结果表明:连杆分模面角部存在折叠缺陷,与表面存在一定倾角,缺陷左侧脱碳,右侧无脱碳,且缺陷右侧存在明显的组织变形;连杆锻造过程中在分模面存在折叠和凹坑等锻造缺陷,在汽车发动机台架可靠性试验中产生疲劳断裂,最终导致连杆整体断裂。另外,连杆螺栓盲孔位置距表面不足3 mm,强度可能不足,也为连杆疲劳断裂的原因之一。

As one of the key components of engine power output, connecting rod directly influences and decides the reliability and durability of engines. Based on the fracture of connecting rod in the engine bench test,this paper analyzes the failure of connecting rod from the macroscopic and microscopic perspectives,and finally finds out the causes of connecting rod fracture,and puts forward the corresponding improvement measures. The analysis shows that there is a folding defect at the corner of the parting surface of the connecting rod, and there is a certain dip angle with the surface. The left side of the defect is decarburized,but the right side is not decarburized and there is apparent deformation on the right side of the fracture. Forging defects exist in the parting surface of connecting rod during forging process,and fatigue fracture occurs in reliability test,all of which leads to the whole connecting rod fracture. Meanwhile,the position of blind hole in connecting rod bolt less than 3 mm from the surface can cause strength insufficient,which also leads to the fracture.