Analyses of Mechanisms and Fatigue Life in a High-Speed Ball Bearing

• Main Authors: Neng-Tung Liao, 廖能通
• Other Authors: Jen-Fin Lin
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/27bw5k

博士 === 國立成功大學 === 機械工程學系碩博士班 === 90 === Abstract The major purpose of this thesis is to provide a new, simple, rapid and effective method to study the mechanism and fatigue life in a ball bearing. The main difference between present and past studies is the method of solving the parameters of a ball bearing. Parameters not solved in past studies such as the contact angles can be solved by the present method of constructing a three dimensional geometry of a ball bearing based on known total deformations of the ball bearing. The contact angle is one of the most important parameters in analyzing the mechanism of the normal force between the ball and the inner or outer raceways. Nevertheless, in past studies on ball bearings, the various contact angles between the balls and the raceways have never been calculated, respective of the operating angular speed of a ball bearing. All parameters and contact angles are on a non-axial symmetry, hence it is very difficult to solve using the past methods of bearing applied radial loads. This thesis will provide a simple geometry relationship of a ball bearing, to construct the algebraic equations between the total deformations and the raceways, the relationship of the normal forces and the deformations in ball bearing, and the resultant force balance equations. Through the geometric analysis of a ball bearing and the force balance, several parameters can be easily obtained, like: the normal forces acting on the contact points; the contact angle at either the inner or the outer raceways that vary with the bearing position angles; bearing stiffness in the axial and radial directions that vary with the cage’s angular velocity, etc. Using Hirano’s criterion, the conditions for the proper choice of the total deformations in two directions can be identified in order to avoid bearing skidding. The slip is analyzed under the circumstances of outer raceway control and oil lubrication. The results indicate that the sliding behavior cannot be avoided at the inner raceway so long as a radial load is applied. Under the condition of controlling the outer raceway temperature, the thermal deformations of all components of a ball bearing are taken into account in the calculations of bearing performances. Finally, to apply the L-P model, Weibull’s model, and the present model for computation of the bearing fatigue life, the effect of variable contact angles on the fatigue life of a ball bearing is thus investigated. The influence on the fatigue life due to the inclusion of ball life can be evaluated at various operating conditions.