Abstract
Extensive investigations of heavily loaded journal bearings were conducted in Dr. Kingsbury’s laboratory several years ago in connection with studies of roll-neck bearings. The problem of maintaining complete fluid-film lubrication under loads of several thousand pounds per square inch of bearing area was visualized as one of bearing design and the provision of an adequate supply of the proper lubricant to suit operating conditions. Following this line of approach, it was found that the usually available lubricants are entirely satisfactory for the formation of a complete metal-separating oil film when the bearing has been constructed in such manner as to make the formation of this protecting film possible. Hence, except at the moments of starting and stopping, metallic friction and wear may be eliminated under operating conditions.
Results of the tests were found to be in good agreement with published theory when the operating conditions were reasonably close to those upon which the theory is based. For example, theory indicates that with constant speed and film viscosity the friction coefficients of fitted journal bearings and plane surfaces will continue to decrease indefinitely with increasing load. At constant speed and temperature it was observed that when the load was increased to several thousand pounds per square inch the friction-coefficient curves for fitted journal bearings reached a minimum and then started to increase with added load. In the absence of metallic contact this discrepancy between observed and theoretical frictions suggested the probability of the high pressures in the bearing oil film causing an increase in film viscosity. The present paper undertakes a mathematical explanation of this phenomenon by calculating the effect of viscosity increase under pressure on the operating characteristics of plane surfaces of infinite width. Some of the more interesting of the test results are given in the form of curves and these are compared with calculations for plane surfaces of infinite width assumed to be operating under the same conditions.
