Dynamic Characters Of The Cylindrical Roller Bearing During The Start Up

Rolling bearings which support rotating parts via rolling contacts among the main elements are widely used in modern machines. The changes of loads, speeds and temperatures within a certain range don’t have an obvious effect on good performance of rolling bearings. However, some research results show that the sudden changes of speeds and loads often cause bearing failure during the start up, such as cage fracture and raceway scratch etc., so that the bearing can’t go to a stable operation state. So it is necessary to study the dynamic characters of the bearing during the start up in order to find the causes of bearing failure and prevent bearing failure. The cylindrical roller bearing is a key part of the aircraft engine whose performance improvement has a deep effect on development of a new generation aircraft engine. Therefore, there is a far significance to study the dynamic characters of the cylindrical roller bearing during the start up.Based on the mechanical system dynamic simulation software ADAMS(Automatic Dynamic Analysis of Mechanical Systems)and the dynamic theory of rolling bearing, the dynamic model and differential equations of cylindrical roller bearings during the start up are obtained considering of changes of lubrication state between rollers and rings, tribology and contact theory, and the elastic deformation of the cage. ADAMS model is linked with subroutines written with Fortran via the dynamic link library, then time varying loads and velocities are simulated factually and internal transient forces are managed perfectly. The dynamic characters of cylindrical roller bearings during the start up are analysed by the three-dimensional simulation model to provide theoretical guide for design and use of cylindrical roller bearings.Taking a type of cylindrical rolling bearing as example, the influences on the slippage of the roller and the dynamic characters of the cage during the start up have been studied at different radial loads, angular accelerations of inner ring, viscosity of lubricating oil and working temperatures, at the same time, the effect of guide style of the cage on dynamic characters of the cage has been analysed. The results show that: during the start up of the cylindrical roller bearing, rotational speed growth of the roller about its axis is not linear but stepwise, and there exits a more serious slippage in the early start; Radial loads and angular accelerations of the inner ring have an great influence on the slippage of the roller and the dynamic characters of the cage, and radial loads have a direct effect on the formation of lubricant film between rollers and rings, however, angular accelerations of the inner ring affect deeply the formation speed of lubricant film between rollers and rings; A proper increase in viscosity of lubricating oil or a appropriate decrease in working temperature can reduce the slippage of the roller to prevent the raceway scratch effectually during the start up; When the cage is guided by rotating ring, the slippage ratio of the cage is smaller, however, the lubrication states of the bearing and impact forces between the roller and the cage are very complex so that the cage stabilization is worse; The cage is easier to have a whirl motion when it is guided by inner ring. Finally, the slippage ratio of the cage is tested under specific conditions on the self-developed bearing testing machine with the bearing used for simulation, then the accuracy of the model in the paper is verified by comparisons between testing results and simulation results.