Analysis of fracture failure mechanism of connecting rod for a diesel engine and its improvement
JIAO Mingyu
LI Chengyan
JIANG Liyuan
KONG Long
Abstract：To solve the fracture failure of a diesel engine connecting rod during fatigue testing,the macroscopic and microscopic morphologies of the fracture surface are observed,and metallographic structure analysis,energy spectrum analysis,non-metallic inclusion chemical composition and content grade inspection are carried out on the connecting rod to determine the cause of the fracture.Improvement measures are proposed,and fatigue and overall durability tests are conducted on the improved connecting rod.The results shows that there is a loose defect in the center of the steel rod used as the raw material for the connecting rod.After cutting and high-temperature forging,iron oxide is produced at the top of the small head of the connecting rod,which becomes a fatigue source under alternating loads,leading to cracks in the connecting rod;the sulfide inclusion content in the connecting rod is too high,the length exceeds the limit,and it has directionality,which causes cracks to propagate outward and accelerates the fracture process of the connecting rod.After taking improvement measures such as reducing the overheating of steel bars during continuous casting,improving the ultrasonic testing level,and reducing the content of sulfur and sulfides,the connecting rod successfully passes the fatigue test and the overall durability test,and there are no more incidents of connecting rod fracture failure.
Keywords：connecting rod fracturefatigueporosity defectnon-metallic inclusion
Publication Date：2025-07-30
Online Publishing Date：2026-05-22(First online date of this platform, not the publication date of the document)
Pages：7( 104-110 )