An Investigation of Permanent Deformation (Brinelling) of Ball and Roller Specimens

The conventional method of calculating static load allowables for rolling element bearings is based on a brinell which will not affect the rotational fatigue life of the bearing. For an oscillating bearing requiring only limited cycle life, this is a very conservative approach. Increased allowables are possible where static allowables are based on 2/3 of the fracture capacity of the bearing, provided performance of the bearing is not adversely affected by these loads. Results of tests performed on one in. dia balls and 3/8 in. dia rollers are reported. Fracture capacities were determined and permanent deformation as a function of load is listed for the five material combinations tested. Permanent deformation variation at temperatures to 1500 F is discussed. The effect of lubricants and the significance of brinell indentations on rolling friction and on endurance life is reported. Static allowables based on maximum Hertz stress values are listed for each material combination from data obtained. These allowables are much higher than those presently used. Maximum Hertz stress static allowables to 1,000,000 psi can be considered with high strength steel for both ball and roller specimens. Tests on six and one half in. dia ball and roller bearings confirmed that the bearings could withstand very high static loads and still operate at high dynamic loads for the number of cycles required in wing pivots and other similar applications.