scholarly journals Effects of Ultra-Clean and Centrifugal Filtration on Rolling-Element Bearing Life

1982 ◽  
Vol 104 (3) ◽  
pp. 283-291 ◽  
Author(s):  
S. H. Loewenthal ◽  
D. W. Moyer ◽  
W. M. Needelman
Keyword(s):  
Aircraft Engine ◽  
Surface Damage ◽  
Fatigue Tests ◽  
Rolling Element Bearing ◽  
Bearing Life ◽  
Deep Groove ◽  
Rolling Element ◽  
Element Bearing ◽  
High Level ◽  
Better Than

Fatigue tests were conducted on groups of 65-millimeter bore diameter deep-groove ball bearings in a MIL-L-23699 lubricant under two levels of filtration. In one test series, the oil cleanliness was maintained at an exceptionally high level (better than a class of “00” per NAS 1638) with a 3 micron absolute barrier filter. These tests were intended to determine the “upper limit” in bearing life under the strictest possible lubricant cleanliness conditions. In the tests using a centrifugal oil filter, contaminants of the type found in aircraft engine filters were injected into the filters’ supply line at 125 milligrams per bearing-hour. “Ultra-clean” lubrication produced bearing fatigue lives that were approximately twice that obtained in previous tests with contaminated oil using 3 micron absolute filtration and approximately three times that obtained with 49 micron filtration. It was also observed that the centrifugal oil filter had approximately the same effectiveness as a 30 micron absolute filter in preventing bearing surface damage.

Rolling Element Bearing Non-Linearity Effects

2000 ◽  
Author(s):  
N. S. Feng ◽  
E. J. Hahn
Keyword(s):  
Equations Of Motion ◽  
Rolling Element Bearing ◽  
Radial Clearance ◽  
Rotor Systems ◽  
Bearing Life ◽  
Rolling Element ◽  
Bearing Load ◽  
Rolling Elements ◽  
Element Bearing ◽  
Negative Clearance

Non-linearity effects in rolling element bearings arise from two sources, viz. the Hertzian force deformation relationship and the presence of clearance between the rolling elements and the bearing races. Assuming that centrifugal effects may be neglected and that the presence of axial preload is appropriately reflected in a corresponding change in the radial clearance, this paper analyses a simple test rig to illustrate that non-linear phenomena such as synchronous multistable and nonsynchronous motions are possible in simple rigid and flexible rotor systems subjected to unbalance excitation. The equations of motion of the rotor bearing system were solved by transient analysis using fourth order Runge Kutta. Of particular interest is the effect of clearance, governed in practice by bearing specification and the amount of preload, on the vibration behaviour of rotors supported by ball bearings and on the bearing load. It is shown that in the presence of positive clearance, there exists an unbalance excitation range during which the bearing is momentarily not transmitting force owing to contact loss, resulting in rolling element raceway impact with potentially relatively high bearing forces; and indicating that for long bearing life, operation with positive clearance should be avoided in the presence of such unbalance loading. Once the unbalance excitation is high enough to avoid such contact loss, it is the bearings with zero or negative clearance which produce maximum bearing forces.

Transient Rotordynamic Modeling of Rolling Element Bearing Systems

2001 ◽  
Author(s):  
A. Liew ◽  
N. S. Feng ◽  
E. J. Hahn
Keyword(s):  
Rolling Element Bearing ◽  
Hertzian Contact ◽  
Centrifugal Load ◽  
Linear Behavior ◽  
Deep Groove ◽  
Rolling Element ◽  
Rolling Elements ◽  
Load Effects ◽  
Element Bearing ◽  
Bearing Preload

Non-linearity effects in rolling element bearings may arise from the Hertzian contact force deformation relationship, the presence of clearance between the rolling elements and the bearing races, and the bearing to housing clearance. Assuming zero bearing to housing clearance and ignoring rolling element centrifugal load effects, it has been shown in earlier work that Rotor Bearing Systems (RBSs) with deep groove ball bearings can give rise to non-linear behavior such as chaotic motion and jump. This paper extends the bearing model to include rolling element centrifugal load, angular contacts and axial dynamics. The effect of more sophisticated bearing models is illustrated in both a rigidly supported rigid RBS and a flexibly supported flexible RBS, the latter being a model of a test rig designed to simulate an aircraft mounted accessory drive unit. Results are presented on the effect of bearing preload on the unbalance response up to a speed of 18,000 rpm.

scholarly journals A New Criterion for Predicting Rolling-Element Fatigue Lives of Through-Hardened Steels

1973 ◽  
Vol 95 (3) ◽  
pp. 287-293 ◽  
Author(s):  
J. L. Chevalier ◽  
E. V. Zaretsky ◽  
R. J. Parker
Keyword(s):  
Room Temperature ◽  
Rolling Element Bearing ◽  
Tempering Temperature ◽  
Bearing Life ◽  
Material Hardness ◽  
Rolling Element ◽  
Carbide Size ◽  
Element Bearing ◽  
New Criterion ◽  
Carbide Particles

A carbide factor was derived based upon a statistical analysis which related rolling-element fatigue life to the total number of residual carbide particles per unit area, median residual carbide size, and percent residual carbide area. An equation was empirically determined which predicts material hardness as a function of temperature. The limiting temperatures of all of the materials studied were dependent on initial room temperature hardness and tempering temperature. An equation was derived combining the effects of material hardness, carbide factor, and bearing temperature to predict rolling-element bearing life.

scholarly journals Effect of Silicon Nitride Balls and Rollers on Rolling Bearing Life

2004 ◽  
Author(s):  
Erwin V. Zaretsky ◽  
Brian L. Vlcek ◽  
Robert C. Hendricks
Keyword(s):  
Silicon Nitride ◽  
Rolling Bearing ◽  
Rolling Element Bearing ◽  
Steel Rolling ◽  
Bearing Life ◽  
Deep Groove ◽  
Rolling Element ◽  
Hybrid Bearing ◽  
Conventional Rolling ◽  
Cylindrical Roller

Three decades have passed since the introduction of silicon nitride rollers and balls into conventional rolling-element bearings. For a given applied load, the contact (Hertz) stress in a hybrid bearing will be higher than an all-steel rolling-element bearing. The silicon nitride rolling-element life as well as the lives of the steel races were used to determine the resultant bearing life of both hybrid and all-steel bearings. Life factors were determined and reported for hybrid bearings. Under nominal operating speeds, the resultant calculated lives for deep-groove, angular-contact, and cylindrical-roller hybrid bearings are respectively, 3.8, 3.3, and 5.5 times that using the Lundberg-Palmgren equations. An all-steel bearing under the same load and nominal operating speeds will always have higher life than the equivalent hybrid bearing operating under the same conditions. Under these conditions, hybrid bearings are predicted to have a lower fatigue life than the all-steel bearings by 58 percent for deep-groove bearings, 41 percent for angular-contact bearings and 28 percent for cylindrical roller bearings.

Experimental and numerical investigations on rolling element bearing thermal behaviour

2020 ◽  
pp. 135065012093233
Author(s):  
P Brossier ◽  
D Niel ◽  
C Changenet ◽  
F Ville ◽  
J Belmonte
Keyword(s):  
Thermal Behaviour ◽  
Volume Fraction ◽  
Operating Conditions ◽  
Rolling Element Bearing ◽  
Test Rig ◽  
Specific Test ◽  
Deep Groove ◽  
Rolling Element ◽  
Penetration Ratio ◽  
Element Bearing

In the present study, some measurements have been conducted on a dedicated test rig to investigate rolling element bearing thermal behaviour. This test rig makes possible the determination of the tested rolling element bearing power losses through the resistive torque measurement. Some thermocouples are located on fixed parts of the system (housing, rolling element bearing outer ring) and others on rotating parts (rolling element bearing inner ring and shaft) via a telemetry system. A deep groove ball bearing, whose pitch diameter is equal to 85 mm, has been tested under oil jet lubrication for different operating conditions. Measurements of the penetration ratio, defined as the proportion of oil actually entering the rolling element bearing versus the oil injected, have also been conducted. An extended thermal network of the test rig has been established to enable a closer understanding of the rolling element bearing inner thermal behaviour. Based upon the first principle of thermodynamics for transient conditions, the studied system is divided into lumped elements at uniform temperature connected by thermal resistances which account for conduction, radiation and convection. Convection within the rolling element bearing depends on the amount of oil in the oil–air mixture known as the volume fraction. At specific test conditions, the developed model found good agreements with experiences for a given oil volume fraction of 15%. This value of volume fraction leads to an adapted formula for volume fraction in the case of jet lubrication which includes the measured penetration ratio.

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