Investigations On Output Shaft Failure In The Gearbox And Forging Process Simulation And Analisys

The output shaft is the one of most important parts of marine gearbox，it is used totransfer the output torque. During practical condition, the output shaft appeared failureafter one year service, which not only led to the marine gearbox unable to run normally,but also caused tremendous production and economic losses. Therefore, the failureanalysis was done to the fracture of output shaft in this paper.In addition, the forgingprocess of output shaft was simulated with Deform-3D software and Based on thesimulation results, the forging process have been investigated to explore the failurecause of the output shaft.The failure reanson of the shaft was studied in this paper.At frist, the fracturesurface of shaft was done macroscopic observation, it appeared brittle broken surface,and the fracture origin was in the center area of the borken surface. Secondly,Microscopic analysis of experiment have been taken to the the test samples of thebroken surface, mettallogrophic analysis showed that lots of inclusions was found in thefracture origin, the practical metallurgical microstructure and dendritic segregationexisted observed indicates that the heat treatment of the output shaft is not qualified.Intercrystalline fracture, cleavage fracture and inclusions have been found out by SEMobservation，the spectrogram analysis result shows that the inclusions in sample1canbe deduced as silicate inclusions. And, take a series of performance experiment onmaterial of fracture shaft, such as chemical compenent analysis, mechanical propertytest. The result of chemical compenent analysis shows that Si element is out of thestandard, other elements are all normal，on the basis of the analysis before,the reasonshould be caused by inclusions inside of output shaft.The results of tension and blowtest show that mechanical proprety of shaft material is up to standard. At last,comprehensive analysis of all before, the failture reason should be that the presence ofsilicate inclusions and unreasonable metallurgical microstructure caused by unqualifiedheat treatment made a dangerous section, crack fountainhead, and led to brittle fractureof shaft under the effect of loads during work.The transmission system model have been established by Kisssys software in thisarticle, and a strength calculation has been carried out on the output shaft by Kisssoftsoftware. The results shows that the output shaft was designed properly and it should beable to withstand the loads applied. Reasonable forging process parameters is very meaningful to the production ofhigh quality of shaft and improving the service life of shaft. In this paper, the forgingprocess of output shaft was simulated with Deform-3D software. Based on thesimulation results, the void closure, inclusion cracks and grain evolution in the existingforging process have been investigated to explore the failure cause of the output shaft.The analysis results indicate that the inclusion and coarse grain in the shaft center areamay contribute to the output shaft failure.