Study on the lifetime assessment of output shaft bearings for transmissions in tracked vehicle considering its supporting structures

The transmission of tracked vehicles performs complex functions such as steering, shifting, braking, etc. and the system level life time is influenced by many sub-parts such as gear assembly, torque converter, clutches, bearings etc. In particular, the mechanical type steering system has impact shock torques in steering shift and these shock torques can affect the durability of many sub-parts in power train system. The field failure modes of gear assembly, steering assembly and the bearings of output shaft are very complex. In this study, the actual failure mode in the field operation of the transmission was investigated comprehensively. The endurance test for the resulting output shaft, bearing failure analysis and life time assessment was also performed. The life time test method, which was developed for the internal use at the Korea Institute of Machinery and Materials, was used in this study. The effects of each bearing damages with left and right output shafts of different structures were analyzed.