Abstract：The cylinder ramming phenomenon occurred in a diesel engine. After disassembly and inspection, it was due to the fracture of internal connecting rod. The fracture appearance was analyzed by scanning electron microscope (SEM) to analyze the fracture mode of the connecting rod. The chemical composition, tensile strength, impact strength and hardness were tested. Moreover, the microstructure and microhardness of the fracture and its vicinity area were analyzed. The results showed that the surface roughness of the internal thread of the connecting rod reduced the fatigue limit of the material. Under the action of large local working stress, the internal thread started to crack from the bottom of the transition position between the big end and the rod body, and then extended to both sides to the instantaneous fracture. The phenomenon of ramming cylinder was finally caused.
2021, Vol. 39 
