Paper 21: Use of Grease in Rolling Bearings

1967 ◽  
Vol 182 (1) ◽  
pp. 585-624 ◽  
Author(s):  
N. A. Scarlett
Keyword(s):  
Solid Lubricants ◽  
Operating Conditions ◽  
Rolling Contact ◽  
Nuclear Radiation ◽  
Grease Lubrication ◽  
Rolling Bearings ◽  
Lubricating Oils ◽  
Liquid Lubricant ◽  
Yield Value ◽  
Design Speed

Lubricating greases are semi-fluid or solid lubricants consisting of a thickening agent in a liquid lubricant. They differ from conventional lubricating oils in that they are non-Newtonian in behaviour and will not flow unless stressed under shear beyond a certain value, known as the yield value. It is this ‘non-flowing’ characteristic of greases that enables them to offer certain advantages over lubricating oils and results in their extensive use for the lubrication of rolling contact bearings. This paper outlines the uses and limitations of grease lubrication in rolling bearings. In particular, factors that can influence performance, such as bearing design, speed and temperature, are dealt with in some detail. In addition, new lubrication problems encountered in atomic reactors and aerospace equipment, involving nuclear radiation and inert atmospheres, are discussed, together with steps taken to solve the problems. In conclusion, the paper outlines observations made on the mechanism by which a grease lubricates and also suggests possible future trends in grease development which will be required to cater for the more exacting operating conditions demanded by modern machinery.

Tribology Aspects Considered When Selecting Rolling Bearings for the Automobile Industry

1983 ◽  
Vol 197 (1) ◽  
pp. 1-5
Author(s):  
H J R Glöckner
Keyword(s):  
Automobile Industry ◽  
Operating Conditions ◽  
Rolling Contact ◽  
Tribological Behaviour ◽  
Rolling Bearings ◽  
Drive Motor ◽  
Short Test ◽  
Save Energy ◽  
New Generation ◽  
Selection Of

To save energy and to reduce weight of automobiles, the tribological behaviour of the bearing positions in the torque flow between drive motor and tyre contact have been optimized to reduce losses in rolling bearings. This has resulted in a considerable increase in power density and life of rolling bearings in gearboxes and differential gears. By development of a new generation of wheel bearings it has been possible to reduce the weight of unsprung masses of the cars considerably. By selection of suitable lubricants, frictional losses in rolling bearings can also be reduced. By means of a short test it is now possible to evaluate the behaviour of lubricants in the rolling contact under operating conditions.

Applications of vibro-acoustic measurement and analysis in conjunction with tribological parameters to assess surface fatigue wear developed in the roller-bearing system

2021 ◽  
pp. 135065012098246
Author(s):  
Shashikant Pandey ◽  
Muniyappa Amarnath
Keyword(s):  
Roller Bearing ◽  
Operating Conditions ◽  
Rolling Contact ◽  
Stribeck Curve ◽  
Fatigue Wear ◽  
Surface Fatigue ◽  
Rolling Element ◽  
Measurement And Analysis ◽  
Contact Surfaces ◽  
Bearing System

Rolling-element bearings are the most commonly used components in all rotating machinery. The variations in the operating conditions such as an increase in the number of operating cycles, load, speed, service temperature, and lubricant degradation result in the development of various defects such as pitting, spalling, scuffing, scoring, etc. The defects that appeared on rolling contact surfaces cause surface deterioration and change in the vibration and sound levels of the bearing system. The present experimental investigations are aimed at assessing the surface fatigue wear that appears on the contact surfaces of roller bearings. The studies considered the estimation of specific film thickness, analysis of surface fatigue wear developed on the rolling-element surfaces, surface roughness analysis, grease degradation analysis using Fourier transform infrared radiation, and vibration and sound signal measurement and analysis. The results obtained from the experimental investigation provide a good correlation between surface wear, vibration, and sound signals with a transition in the lubrication regimes in the Stribeck curve.

Service Loading Analysis of Wind Turbine Gearbox Rolling Bearings Based on X-Ray Diffraction Residual Stress Measurements

2013 ◽  
Vol 768-769 ◽  
pp. 723-732 ◽  
Author(s):  
Jürgen Gegner ◽  
Wolfgang Nierlich
Keyword(s):  
Residual Stress ◽  
Wind Turbine ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
X Ray Diffraction ◽  
Rolling Bearings ◽  
Wind Turbine Gearbox ◽  
X Ray ◽  
Stress Measurements

Rolling bearings in wind turbine gearboxes occasionally fail prematurely by so-called white etching cracks. The appearance of the damage indicates brittle spontaneous tensile stress induced surface cracking followed by corrosion fatigue driven crack growth. An X-ray diffraction based residual stress analysis reveals vibrations in service as the root cause. The occurrence of high local friction coefficients in the rolling contact is described by a tribological model. Depth profiles of the equivalent shear and normal stresses are compared with residual stress patterns and a relevant fracture strength, respectively. White etching crack failures are reproduced on a rolling contact fatigue test rig under increased mixed friction. Causative vibration loading is evident from residual stress measurements. Cold working compressive residual stresses are an effective countermeasure.

A Spectrographic Sampling Method for Quick Assessment of Cylinder and Piston Ring Wear

1968 ◽  
Vol 90 (1) ◽  
pp. 43-48
Author(s):  
H. U. Wisniowski ◽  
D. R. Jackson
Keyword(s):  
Rapid Method ◽  
Sampling Method ◽  
Piston Ring ◽  
Cylinder Liner ◽  
Small Sample ◽  
Operating Conditions ◽  
Small Hole ◽  
Cylinder Wall ◽  
Lubricating Oils ◽  
Wear Rates

A simple, inexpensive, and rapid method of assessing cylinder and piston ring wear was developed. A small sample of the oil which lubricates the cylinder wall and piston rings was drawn off through a small hole in the cylinder wall. The sample was then analyzed spectrographically. Changes in wear resulting from changes in cylinder liner materials, fuels, lubricating oils, and other operating conditions were investigated. The method was found useful especially in cases of drastic differences in the wear rates. Selected examples of these studies are reported.

Influence of ZnDTP on Rolling Contact Fatigue Life under Grease Lubrication

2021 ◽  
Vol 2021.59 (0) ◽  
pp. 05a5
Author(s):  
Hirotomo HOSOI ◽  
Yugo KAMEI ◽  
Hirotoshi AKIYAMA ◽  
Jusei MAEDA ◽  
Masanori SEKI
Keyword(s):  
Fatigue Life ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Grease Lubrication ◽  
Contact Fatigue Life

Parametric Simulation of Rolling Contact Fatigue

2008 ◽  
Author(s):  
Scott M. Cummings ◽  
Patricia Schreiber ◽  
Harry M. Tournay
Keyword(s):  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Wear Model ◽  
Primary Methods ◽  
Vehicle Performance ◽  
Track Geometry ◽  
Advantages And Disadvantages ◽  
Defect Prevention ◽  
Design Speed

Simulations of dynamic vehicle performance were used by the Wheel Defect Prevention Research Consortium (WDPRC) to explore which track and vehicle variables affect wheel fatigue life. A NUCARS® model was used to efficiently examine the effects of a multitude of parameters including wheel/rail profiles, wheel/rail lubrication, truck type, curvature, speed, and track geometry. Results from over 1,000 simulations of a loaded 1,272 kN (286,000-pound) hopper car are summarized. Rolling contact fatigue (RCF) is one way that wheels can develop treads defects. Thermal mechanical shelling (TMS) is a subset of wheel shelling in which the heat from tread braking reduces a wheel’s fatigue resistance. RCF and TMS together are estimated to account for approximately half of the total wheel tread damage problem [1]. Other types of tread damage can result from wheel slides. The work described in this paper concerns pure RCF, without regard to temperature effects or wheel slide events. Much work has been conducted in the past decade in an attempt to model the occurrence of RCF on wheels and rails. The two primary methods that have gained popularity are shakedown theory and wear model. The choice of which model to use is somewhat dependent on the type of data available, as each model has advantages and disadvantages. The wear model was selected for use in this analysis because it can account for the effect of wear on the contacting surfaces and is easily applied to simulation data in which the creep and creep force are available. The findings of the NUCARS simulations in relation to the wear model include the following: • Degree of curvature is the single most important factor in determining the amount of RCF damage to wheels; • The use of trucks (hereafter referred to as M-976) that have met the Association of American Railroads’ (AAR) M-976 Specification with properly maintained wheel and rail profiles should produce better wheel RCF life on typical routes than standard trucks; • In most curves, the low-rail wheel of the leading wheelset in each truck is most prone to RCF damage; • While the use of flange lubricators (with or without top of rail (TOR) friction control applied equally to both rails) can be beneficial in some scenarios, it should not be considered a cure-all for wheel RCF problems, and may in fact exacerbate RCF problems for AAR M-976 trucks in some instances; • Avoiding superelevation excess (operating slower than curve design speed) provides RCF benefits for wheels in cars with standard three-piece trucks; • Small track perturbations reduce the overall RCF damage to a wheel negotiating a curve.

Effect of substrate surface roughness on the wear of molybdenum disulphate coated rolling contact bearings

2021 ◽  
Vol 63 (9) ◽  
pp. 848-854
Author(s):  
Bahar Gokce ◽  
Necdet Geren ◽  
Mahmut Izciler
Keyword(s):  
High Temperature ◽  
Molybdenum Disulfide ◽  
Substrate Surface ◽  
Operating Conditions ◽  
Rolling Contact ◽  
Wear Testing ◽  
Wear Depth ◽  
Phosphate Coating ◽  
Depth Measurement ◽  
Friction Moment

Abstract The objective of the present experimental work is to investigate the influence of subsurface roughness on the friction and wear performance of high-temperature ball bearing. Bearings, which are used in high-temperature applications, are affected by several operating conditions. Some factors under high-temperature conditions such as short grease life, thin-film thickness at low speed, and insufficient internal clearance can drastically reduce bearing service life due to an increase in surface friction. For this reason, rolling contact bearings are coated with molybdenum disulfide. Before the molybdenum disulfide (MoS2) coating, phosphatization is applied to the bearings. Because the phosphate layer is micro-porous, it assures that molybdenum disulfide is entrapped in the interstitials between the phosphates. Also, phosphate coating provides a much larger surface area for the lubricant to attach to. In this study, several process steps, sandblasting, manganese phosphate coating, molybdenum disulfide coating, friction moment testing, wear testing, wear depth measurement, SEM, and XRD analyses were carried out. Wear tests and friction moment tests were applied to the rings of bearings of varied raceway roughness. This process ultimately provides molybdenum disulfide coated bearings optimum raceway roughness parameters for good wear resistance and optimum boundary lubrication.

Non-Linear Lubricant Behavior in Concentrated Contacts

2001 ◽  
Author(s):  
Andras Z. Szeri
Keyword(s):  
Elastic Deformation ◽  
Hydrodynamic Lubrication ◽  
Elastohydrodynamic Lubrication ◽  
Rolling Contact ◽  
Material Behavior ◽  
Solid Surfaces ◽  
Hydrodynamic Theory ◽  
Shear Rates ◽  
Liquid Lubricant ◽  
Temperature And Pressure

Abstract Elastohydrodynamic lubrication (EHL) is the name given to hydrodynamic lubrication when it is applied to solid surfaces of low geometric conformity (counterformal contacts) that are capable of, and are subject to, elastic deformation. In bearings relying on EHL principles, the residence time of the fluid is less than 1 ms, the pressures are up to 4 GP, the film is thin, down to 0.1 μm, and shear rates are up to 108 s−1 — under such conditions lubricants exhibit material behavior that is distinctly different from their behavior in bulk at normal temperature and pressure. In fact, without taking into account the viscosity-pressure characteristics of the liquid lubricant and the elastic deformation of the bounding solids, hydrodynamic theory is unable to explain the existence of continuous lubricant films in highly loaded gears and rolling contact bearings.

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