Fracture Analysis of Gears of a Speed Reducer

The failure of a shaft and gears of a speed reducer after serving for a year was investigated by means of microstructure observetion,scanning electron microscopy (SEM),hardness test and tension test.The results showed that the failure of the shaft and gears was fatigue fracture and the fracture of the shaft occurred firstly.The fatigue crack initiated from an overload.Incorrect assemble was responsible for the overload of the shaft.