AbstractContinuous design and improvements in performance of roller bearings have resulted in an increased power transmission whilst size and spatial requirements have been reduced. Radial cylindrical roller bearings have followed this trend and due to their high performance characteristics (such as high loading capacity and high rotational speed capabilities), they have obtained a firm place as high performance machine elements. An essential characteristic of a radial cylindrical roller bearing is the minimisation of frictional torque for particular operating conditions.
In spite of these improvements in design and operation the bearing frictional torque is still usually calculated according to the Palmgren method first published in 1957. However, as a result of the increased performance of radial cylindrical roller bearings and a corresponding wider range of application this Palmgren method is insufficiently accurate for the prediction of frictional torques in modern bearings. Whilst the literature review in this thesis identified a variety of bearing frictional torque calculation methods, most of these methods are based on various ball bearing designs and are not necessarily applicable to cylindrical roller bearings types. As a result an accurate frictional torque prediction method is required for radial cylindrical roller bearings because of customer's demands.
Consequently, the current project is combined with the development of a method of frictional torque prediction (FTP - Method), which enables the frictional torque of purely radially and radially and axially loaded radial cylindrical roller bearings to be calculated accurately. The FTP - Method is based on the physical effects producing the frictional torque in a bearing, such as the EHL - theory and a contact analysis to determine raceway rolling resistance, and in addition takes into account the frictional forces of the rib / rolling element end face rolling and sliding contact. Comprehensive experimental tests have been undertaken on different radial cylindrical roller bearing designs (including cage guided and full complement types) for a minimum of three different sizes to validate the derived equations.
Good agreement was obtained between the predictions according to the FTP - Method and the measured test data for the frictional torqye of both radially and combined loaded bearings. Moreover, the thermal reference speed and the thermal limiting speed of a radial cylindrical roller bearing can be readily calculated for any operating condition using an explicit equation in the radial part of the FTP - Method.
The thesis also presents a calculation program to illustrate a method of bearing design based on the thermal balance within a bearing. The bearing is initially pre-selected according to its life time requirements using a life time calculation. After the lubrication method has been defined a thermal balance can be used to design the bearing.
|Date of Award
- Radial cylindrical roller bearings
- minimisation of frictional torque
- frictional torque prediction