Rolling Contact Bearings Research Articles

Computer-aided Shaft Design and Selection of Rolling-contact Bearings Using an Expert System

In this study, a computer program was developed using Q-Basic programming language to analyze the strength and deformation of a rotating circular stepped shaft. These shafts have a variety of power- transmitting mechanical elements (components), such as pairs of gears, and pulleys that are modeled in 3-D. In addition, force and moment analyses of these elements running on the shafts are examined. Notch sensitivity and stress concentration factors given graphically were formulated using the finite difference method. Furthermore, to select the best rolling-contact bearings, an expert system requiring the knowledge-based technique was employed. The knowledge of the expert system and data of the roll ing bearing catalogue were input into the program. To perform the expert system, the LEONARDO software technique was used.

Rolling contact silicon nitride bearing technology: a review of recent research

The paper reviews some of the extensive research in the field of ceramic rolling element bearings that has been carried out over the past decade or so. As a result of this work hot isostatically pressed silicon nitride (HIPed Si 3N 4), has emerged as an extremely promising material for fabricating high performance all-ceramic or hybrid steel/ceramic rolling contact bearings. Compared with conventional steel bearings silicon nitride bearings have been shown to offer significant benefits in terms of rolling contact fatigue life, and the lower density of the material greatly reduces the dynamic loading at ball/raceway contacts in very high speed applications such as machine tool spindles and gas turbine engines. Investigations have shown the particular benefits of using silicon nitride bearings in severe lubrication and wear conditions such as extreme temperature, large temperature differential, high speed, ultra-high vacuum and in safety-critical applications where, for example, they can respond to the requirements of short periods of oil-off operation in an aircraft engine. Other benefits which have been demonstrated are corrosion resistance and tolerance of contaminated lubricants. As a result of their sustained development and testing it is expected that silicon nitride bearings will continue to achieve wide acceptance in all types of applications.

Fatigue Failure and Ball Bearing Friction

According to the standard method for calculation of life ratings for rolling contact bearings, failure is considered to occur at the initiation of the first spall in a rolling component surface. While this is acceptable for most bearing applications, in many applications bearing operation may effectively continue for a period of time during which spoiling progresses. As spoiling progresses, bearing friction and vibratory loading increase, eventually resulting in bearing seizure and mechanism failure. To estimate the amount of operating time available for corrective action; i.e., mechanism shutdown and bearing replacement, between initial spoiling and potential mechanism failure, an investigation into the friction occurring in a spalled-unspalled concentrated point contact was conducted using a ball/v-ring test rig to generate and progress spalls and a ball-disk rig to test traction. It was thereby determined for a spalled ball-raceway) contact, that a lubricant film of thickness sufficient to adequately “separate” the contacting surfaces can occur: With continuous ample supply of fluid lubricant, measured traction coefficients were only slightly greater than would be expected for unfailed contacts. Using the experimental results, an empirically based mathematical model was developed to estimate ball-raceway traction as a function of degree of spalling. These data will subsequently be used in ongoing studies to estimate rate of spall progression in bearing applications. Presented as a Society of Tribologists and Lubrication Engineers Paper at the STLE/ASME Tribology Conference in Orlando, Florida, October 11–13, 1999

Forensic Engineering Analysis Of Failed Roller Bearings

Failure Of Rolling Element Bearings Often Results In Damage To The Bearing Elements And Adjacent Components Such As Axles, Shafts, Gearboxes, Wheels, Etc. Forensic Analysis Of Rolling Contact Bearings Is Discussed In This Paper. A Review Of Bearing Types And Typical Operating Characteristics Is Presented. A Procedure For Systematic Examination And Analysis Of Bearing Failure Evidence Is Suggested, And Several Case Studies Are Presented Which Demonstrate The Types Of Evidence Typically Remaining And The Logic Which Leads To Engineering Conclusions Concerning The Cause Of Bearing Failures.

Standard handbook of machine design

Introductions: Standards, Codes, Regulations. Statistical Considerations. Measurement and Inference Numerical Methods. Computational Considerations. Wear. Solid Materials. The Strength of Cold-Worked and Heat-Treated Steels. Usability. Safety. Minimizing Engineering Effort. Strength Under Static Circumstances. Fundamentals of Arc Welding. Instabilities in Beams and Columns. Curved Beams and Rings. Seals. Flywheels. Limits and Fits. Power Screws. Threaded Fasteners. Unthreaded Fasteners. Bolted and Riveted Joints. Springs. Lubrication. Gaskets. Rolling-Contact Bearings. Journal Bearings. Couplings. Clutches and Brakes. Belt Drives. Chain Drives. Spur Gears. Bevel and Hypoid Gears. Helical Gears. Worm Gearing. Shafts. Vibration and Control of Vibration. A Thesaurus of Mechanisms. Cam Mechanisms. Linkages. Load-Cycle Analysis. Fluid Power Systems and Circuit Design. Corrosion. Noise and Its Control. Gear Trains. Robots and Smart Machines. Sections and Shapes-Tabular Data. Stress. Deflection.

Ceramic Hybrid Bearings in Air-Cycle Machines

Extensive research in the field of ceramic rolling contact bearings has been conducted over the past several years. The results of this research indicate that silicon nitride may offer significant improvements in rolling fatigue life and a possible increase in operating temperature. AlliedSignal Aerospace Systems & Equipment (ASE) and the Air Force Item Management Engineering Branch at Tinker Air Force Base are conducting a development program under contract to ARPA to introduce ceramic hybrid bearings into existing F-15, F-111, and C-130 aircraft fleets in a near-term program involving retrofitting mature air-cycle machines with such bearings. The air-cycle machine (ACM) is a complex bearing application, operating at very high speeds (up to 100,000 rpm) and at high temperatures. In more severe military ACM applications, mean times between failures (MTBFs) of 2000 and 3000 hours are common. The fleet would see an immediate benefit from improved bearing life. This paper describes the analytical approach to evaluating and comparing ceramic to steel bearings, describes the laboratory test program to verify performance, and discusses the life-cycle cost improvement and the flight test program.

Optimizing the Structure and Properties of Silicon Nitride for Rolling Contact Bearing Performance

The total potential for the application of ceramic materials to rolling-element bearings has yet to be defined. There seems to be no doubt, however, that a commercially important segment of technology will benefit from the unique operating capabilities of ceramic and hybrid ceramic/steel bearings. In order to assure reliability and cost effectiveness in these bearings, it is essential that bearing manufacturers have a means to discriminate among the many materials and suppliers that are competing to supply the market with “bearing-quality” silicon nitride. In this program, 11 candidate monolithic and two silicon carbide whisker-reinforced, silicon nitride materials were evaluated with respect to their rolling-contact fatigue performance. When they were tested at a maximum Hertzian contact pressure of 5.930 GPa (860 ksi), with steel loading balls and SAE-20 mineral oil lubricant, the materials exhibited life differences of several orders of magnitude. Attempts to correlate the fatigue performance with such properties as density, hardness and elastic moduli were generally unsuccessful. However, the microstructural features such as porosity, second-phase distribution and, in particular, the crystal size and morphology, showed a good qualitative relationship to the fatigue life and failure mode. Under these relatively high-stress conditions, fatigue durability increased dramatically as the microstructure tended toward finer, more equiaxed grains and a uniform, minimum distribution of second phases.

The effect of water lubrication on polymer wear under rolling contact conditions

AbstractThe results of studies into the performance of three selected engineering polymers in rolling contact are presented. Both dry and water lubrication conditions were used. The polymers were machined into a cup simulating the outer race in a rolling contact bearing. Ceramic balls were used in order to create corrosion resistant combinations of materials. Post‐test studies were carried out using a scanning electron microscope. On the basis of microscopy examinations the effect of water on the morphology of contact path surfaces was assessed and the abilities of tested polymers to operate in the presence of water in a rolling contact were ranked. © 1994 John Wiley & Sons, Inc.

Failure modes of ceramics in rolling contact

A comprehensive experimental study has been carried out to ascertain the prevailing mode of failure of concentrated rolling ceramic contacts subjected to cyclic loading conditions. The findings of the studies presented in this paper confirm that good quality silicon nitride balls in non-conforming contact do not fail in a catastrophic mode and thus can be considered for important engineering applications such as rolling contact bearings for gas turbines. The results of extensive testing carried out on perfect and artificially pre-cracked balls under high compressive cyclic stress showed that the prevailing mode of failure is delamination. Scanning electron microscope (SEM) observations enabled the delamination failures to be classified in terms of location of crack initiation and subsequent crack propagation. By using X-ray diffraction, residual stresses on delaminated surfaces were measured and results showed that under certain conditions plastic deformation of the ceramic can take place. Results of supplementary chemical analysis of failure surfaces suggest that changes in the level of silicon, nitrogen and oxygen may take place on delaminated surfaces. Experiments with artificially pre-cracked balls revealed the role played by a lubricating medium in the process of fatigue failure. All findings are illustrated with SEM micrographs and the physical aspects of failure mechanics are discussed.

The Mechanics of Crack Initiation at Hard Particles in Rolling Line Contacts

The mechanics of crack initiation in rolling contact bearings is investigated by considering the possibility of hard particle debonding from the surrounding softer matrix. The local elastoplastic stress and strain fields around a hard cylindrical particle located at the point of maximum shear stress below the Hertz contact are calculated by the finite element method. The calculations show that if the applied Hertz loading is sufficiently high, the matrix contiguous with the particle deforms plastically. Upon unloading tensile residual stresses will be set up normal to the particle-matrix interface. The particle-matrix interface debonds provided the stored elastic energy in and around the particle is larger than the work of adhesion, and the maximum residual radial stress is greater than the cohesive strength of the particle-matrix interface. The gradual softening of the martensitic matrix around non-metallic inclusions or carbides, which is known to occur after a large number of stress cycles in bearing steels, could result in a residual radial stress greater than the interfacial strength and cause particle-matrix debonding.

Transformations in hardened steel ShKh15 during heating and cooling

1. Hardened steel ShKh15 contains a comparatively large amount of residual austenite which decomposes within a fairly large temperature range. There are two regions of high stability of austenite, and between them there is an interval of its instability. 2. Formation of cementite begins at comparatively low (for chromium steels) tempering temperatures (250°C). The most intense formation of cementite begins above 350°C, and the range of carbide tranformations is larger than with carbon steels. 3. The obtained data can be used in the examination of transformations occurring in the working subsurface layers of rolling-contact bearings of steel ShHKh15 in operation, and also in the solution of problems of ensuring stability of quality, increased wear resistance, reliability, and service life of rolling-contact bearings.

Rolling contact wear of polymers: A preliminary study

The wear of three different engineering polymers under rolling contact conditions has been investigated. A subsequent analysis of the results has been carried out to assess the suitability of these polymers for their application in rolling contact bearings.

The role of materials in the design and application of rolling contact bearings

The importance of high quality steels and special high temperature treatments for rolling contact fatigue performance are discussed. Developments needed to cope with special requirements in aero-engine and adverse environments are described. The potential uses of ceramic materials are noted.

The Pitting and Cracking of SAE 52100 Steel in Rolling/Sliding Contact in the Presence of an Aqueous Lubricant

The use of aqueous lubricants is well established in applications where their fire-resistant properties are of prime importance. A major disadvantage of the use of such fluids, however, is their relatively poor performance in high-stress rolling-contact bearings where components suffer fatigue cracking and pitting at an earlier stage than with mineral oils. In this investigation, factors affecting the cracking and pitting of SAE 52100 steel in the presence of a water-glycol-based fluid have been studied using an Amsler two-disk machine. A Stribeck curve was plotted and has shown that pitting damage is dependent on the region of the curve in which the system is operated, pitting life being a minimum in mixed-elastohydrodynamic lubrication. Good correlation was found betwen pitting life and specific film thickness λ above λ = 0.05. Below this value, inverse correlation was observed. Finally, a mechanism for crack initiation, propagation, and subsequent pitting in aqueous fluids is proposed.

Recent research on tribology in Japan

Recent research on tribology in Japan is outlined. There have been many papers on the following problems. In fluid film lubrication, the effects of surface irregularities on the lubricating performance and increase in friction in high speed bearings due to turbulent flow are highlighted to date. Elastohydrodynamic lubrication and its related problems such as traction play an important role in the lubrication of cams and followers, rolling contact bearings and traction drives. The rheology of lubricants at high pressures is one of the most important properties governing lubricated concentrated contacts. Regarding basic studies on wear, the mechanism of the adhesive wear process is being studied. It is interesting to investigate the deformation behaviours of materials and structures by finite element methods. The friction and wear characteristics of plastics and their composites have been studied in basic terms. The chemical reactions of lubricating oil additives with frictional surfaces play important roles in lubricated concentrated contacts. Recently there have been many studies on the correlation between the lubricating properties and the chemical reactivity of lubricant additives. It is very interesting that there are many papers on the mutual effects between lubricant additives.

An Investigation Into the Effect of Side-Plate Clearance in an Uncentralized Squeeze Film Damper

An experimental investigation has been carried out into the influence of side-plate flow restrictors on the performance of a squeeze film damper bearing. The experimental rig used was a flexible rotor with a disk positioned midway between two squeeze film damper bearings. One of the squeeze film dampers was fitted with side plates that could be adjusted and accurately located with respect to the squeeze film damper journal. It has been found that the influence of the side-plate clearance on the ability of the squeeze film damper to reduce the amplitude of the central disk can be considerable if the side-plate clearance is less than the radial clearance. As the side-plate clearance reduces towards zero, the effectiveness of the squeeze film damper diminishes until the amplitudes obtained are the same as those measured when the rolling-contact bearing is rigidly supported. An interesting type of precessing elliptical orbit was discovered for conditions where the “jump” phenomenon was operating.

Solid lubricants in rolling-contact bearings at elevated temperatures

This article presents data from tests on the solid lubricant packing AFZ-3 at elevated temperatures in a VNIPP-100 tester and a modified TsKB-79 tester. Four Type 208 bearings were tested in the VNIPP-100 machine with an inner race speed of 3000 rpm, a radial load of 500 N on the bearing, and an outer race temperature of 250/sup 0/C. The bearing condition was monitored according to the operating noise. The tests were run to failure, with the four bearings operating for 630, 825, 831, and 931 h respectively. The solid lubricant filler retained its lubricating properties. Rolling-contact bearings packed with the AFZ-3 material were also tested under production conditions. Type 305 bearings with the AFZ-3 material operated in monorail cars in a ceramic plant under conditions of periodic exposure to temperatures of 280-300/sup 0/C for more than five years and remained serviceable. Type 312 bearings packed with the AFZ-3 material were tested in a charge loading machine designed to charge metal to thermal furnaces. The bearings remained serviceable after six months of operation. Includes a table.

Behavior of lubricating greases in rolling-contact bearings at low temperatures

This article examines the process of grease mixing in ball bearings in a simulation of the operation of a frictional component in a cold chamber down to -60/sup 0/C. The greases Solidol S, Litol-24, TsIATIM-201, and EF-507 were tested in a specially designed test stand with test sections equipped with covers with singlegroove labyrinths that do not prevent grease throwout. Two No. 407 bearings were operated simultaneously in comparative tests on the greases with a load of 1.75 kN and an inner race speed of 950 rpm. A thermal calculation showed that at the load and speed used in the tests, the temperature of the friction unit should be 10-15/sup 0/C higher than the air temperature in the chamber. It is determined that the greases TsIATIM-201, Litol-24, and EF-507 are serviceable in components with rolling-contact bearings at ambient air temperatures of -50 to -60/sup 0/C; that the Solidol S grease, for which the standard GOST 4666-76 calls for operating temperatures down to -50/sup 0/C, operates more poorly under these conditions, and the wear rate of the rolling elements is considerably greater; that the character of operation of the lubricant in rolling-contact bearings at low temperatures is similar in general form more » to an autooscillatory process; that a leveling of the oscillations corresponds to a critical temperature; and that with a further reduction of temperature, the bearing wear increases. « less

A survey of applications of ehl on machine elements

Concentrated contacts in motion are found in most mechanical machines. The elasto-hydrodynamic lubrication (ehl) theory deals with the lubrication of moving concentrated contacts. The first important successful application of ehl was to rolling contact bearings. The theory can today be used by designers for optimizing bearing design and predicting bearing life, power loss, temperature and dynamic behaviour. The application of ehl to gearing is more complicated. The simplified film thickness calculation methods for gears offer a practical way of making a rough estimation of the risk of failure. Methods for calculating the film thickness in the difficult transient contact conditions and along the gear contact have recently been developed. The application of ehl to the transient conditions in a cam and tappet contact is promising but needs more work. To achieve better methods for the design of lubricated concentrated contacts, a better understanding of microgeometry and thermal and chemical effects in the contact is required

Effects of Synthetic Industrial Fluids on Ball Bearing Performance

A series of laboratory tests was conducted using rolling contact bearings to compare the lubricating properties of a specially formulated synthetic lubricant based on diester to those of a specific mineral oil currently in service in petrochemical plant equipment. Two synthetic lubricants and two mineral oils of varying viscosities were experimentally compared. The test results indicated that the synthetic lubricant, having a viscosity of 32 m2 / s (32 cSt) at a temperature of 313K, offered longterm contact surface protection equivalent to that of the base line mineral oil which has a viscosity of 68 m2 / s, without reducing bearing service life below the theoretically predicted levels. The same good wear protection could not be achieved with a reduced viscosity mineral oil. The use of the lower viscosity synthetic lubricating fluid could provide projected energy savings of $75,000 per year when elements of a total petrochemical complex are considered.