Bearing friction

The lubrication of rolling bearings – similar to that of sliding bearings – mainly serves one purpose: to avoid or at least reduce metal-to-metal contact between the rolling and sliding contact surfaces, i.e. to reduce friction and wear in the bearing. Oil, adhering to the surfaces of the parts in rolling contact, is fed between the contact areas. The oil film separates the contact surfaces preventing metal-to-metal contact (»physical lubrication«).

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BEARING DESIGN AND SELECTION Determining Stresses, Loading, Bending Moments, and Spring Rate in Spoked Bearing Supports 22.1 Hydrodynamic Equations for Bearing Design Calculations 22.6 Graphic Computation of Bearing Loads on Geared Shafts 22.13 Shaft Bearing Load Analysis Using Polar Diagrams 22.17 Journal Bearing Frictional Horsepower Loss During Operation 22.21 Journal Bearing Operation Analysis

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Source: HANDBOOK OF MECHANICAL ENGINEERING CALCULATIONS SECTION 22 BEARING DESIGN AND SELECTION Determining Stresses, Loading, Bending Moments, and Spring Rate in Spoked Bearing Supports 22.1 Hydrodynamic Equations for Bearing Design Calculations 22.6 Graphic Computation of Bearing Loads on Geared Shafts 22.13 Shaft Bearing Load Analysis Using Polar Diagrams 22.17 Journal Bearing Frictional Horsepower Loss During Operation 22.21 Journal Bearing Operation Analysis 22.22 Roller-Bearing Operating-Life Analysis 22.31 Roller-Bearing Capacity Requirements 22.

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Since the dawn of history, human activities have always been closely related to friction, the resistance to sliding. It is thanks to friction that one can stand and walk on the ground, one can wear clothes, one can make fire by rubbing two sticks together, or one can even start and stop a car. In these cases friction is very useful for human beings. In many other cases, however, human activities have been very much hampered by friction since ancient times. How to diminish friction is one of the most basic technological problems. For example, when a heavy...

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Records show the use of wheels from 3500 BC, which illustrates our ancestors’ concern with reducing friction in translationary motion. The transportation of large stone building blocks and monuments required the know-how of frictional devices and lubricants, such as water-lubricated sleds. Figure 1.1 illustrates the use of a sledge to transport a heavy statue by Egyptians circa 1880 BC...

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Moving parts in machinery involve relative sliding or rolling motion. Examples of relative motion are linear sliding motion, such as in machine tools, and rotation motion, such as in motor vehicle wheels. Most bearings are used to support rotating shafts in machines. Rubbing of two bodies that are loaded by a normal force (in the direction normal to the contact area) generates energy losses by friction and wear.

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LIST OF SYMBOLS a af A b C C* D e / FJ h /Z0 H / k L M MJ Axial-flow land width Pad load coefficient Area Circumferential-flow land width Clearance Specific heat Diameter Eccentricity Coefficient of friction Friction on journal Film thickness Minimum film thickness Dimensionless film thickness Mechanical equivalent of heat Permeability Bearing width Rotor mass at bearing Frictional torque on journal

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Tower reported the results of a series of experiments intended to determine the best methods to lubricate a railroad journal bearing. Working with a partial journal bearing in an oil bath, he noticed and later measured the pressure generated in the oil film. Tower pointed out that without sufficient lubrication, the bearing operates in the boundary lubrication regime, whereas with adequate lubrication the two surfaces are completely separated by an oil film. Petrov [5] also conducted experiments to measure the frictional losses in bearings.

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Moving parts in machinery involve relative sliding or rolling motion. Examples of relative motion are linear sliding motion, such as in machine tools, and rotation motion, such as in motor vehicle wheels. Most bearings are used to support rotating shafts in machines. Rubbing of two bodies that are loaded by a normal force (in the direction normal to the contact area) generates energy losses by friction and wear. Appropriate bearing design can minimize friction and wear as well as early failure of machinery...

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Rolling-element bearings, such as ball, cylindrical, or conical rolling bearings, are the bearings most widely used in machinery. Rolling bearings are often referred to as antifriction bearings. The most important advantage of rolling-element bearings is the low friction and wear of rolling relative to that of sliding.

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Access for checking air gap Air-deflecting baffle Coil bracing ring Fan Rotor end ring Rotor bars Stator core Fully-formed coils of the two layer stator winding Core duct separator Preformed coil in section End winding connections Bearing endshield Terminal box with bolted on cable sealing end Shaft Grease ejector handle Grease collector Anti-friction bearing with grease regulator Grease impeller

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Volume II of the Handbook of Lubrication (Tribology) provides coverage of basic theory involved in friction, wear, and lubrication; characteristics and application practices for lubricants; and design principles for lubricated machine elements such as bearings, gears, couplings, and seals.

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Gyroscopic precession is a key factor involved in the concept of operation for the north-seeking gyrocompass, as will be discussed later. Friction in the support bearings, external influences, and small imbalances inherent in the construction of the rotor cause even the best mechanical gyros to drift with time. Typical systems employed in inertial navigation packages by the commercial airline industry may drift about 0.1 during a 6-hour flight [Martin, 1986]. 2.1.

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CONTENTS CONTENTS 962 C H A P T E R n A Textbook of Machine Design Sliding Contact Bearings 1. Introduction. 2. Classification of Bearings. 3. Types of Sliding Contact Bearings. 4. Hydrodynamic Lubricated Bearings. 5. Assumptions in Hydrodynamic Lubricated Bearings. 6. Important Factors for the Formation of Thick Oil Film. 7. Wedge Film Journal Bearings. 8. Squeeze Film Journal Bearings. 9. Properties of Sliding Contact Bearing Materials. 10. Materials used for Sliding Contact Bearings. 11. Lubricants. 12. Properties of Lubricants. 13. Terms used in Hydrodynamic Journal Bearings. 14.

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The most important function of lubricants is the reduction of friction and wear and in some cases, the relative movement of two bearing surfaces is only possible if a lubricant is present. In times when saving energy and resources and cutting emission have become central environmental matters, lubricants are increasingly attracting public awareness. Scientific research has shown that 0.4% of gross domestic product could be saved in terms of energy in Western industrialized countries if current tribological knowledge, i.e.

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The operating principle of this type of brake is the following. A flexible band of leather or rope or steel with friction lining is wound round a drum. Frictional torque is generated when tension is applied to the band. It is known (see any text book on engineering mechanics) that the tensions in the two ends of the band are unequal because of friction and bear the following relationship:

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Active Control in Bridge Engineering 59.1 59.2 Introduction Typical Control Configurations and Systems Active Bracing Control • Active Tendon Control • Active Mass Damper • Base Isolated Bridge with Control Actuator • Base Isolated Bridge with Active Mass Damper • Friction-Controllable Sliding Bearing • Controllable Fluid Damper • Controllable Friction Damper 59 59.

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Tribology in a traditional form has been in existence since the beginning of recorded history. There are many well documented examples of how early civilizations developed bearings and low friction surfaces [1]. The scientific study of tribology also has a long history, and many of the basic laws of friction, such as the proportionality between normal force and limiting friction force, are thought to have been developed by Leonardo da Vinci in the late 15th century

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Rolling contact bearings are also called anti-friction bearing due to its low friction characteristics. These bearings are used for radial load, thrust load and combination of thrust and radial load. These bearings are extensively used due to its relatively lower price, being almost maintenance free and for its operational ease.

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Sliding Contact Bearings 1. Introduction. 2. Classification of Bearings. 3. Types of Sliding Contact Bearings. 4. Hydrodynamic Lubricated Bearings. 5. Assumptions in Hydrodynamic Lubricated Bearings. 6. Important Factors for the Formation of Thick Oil Film. 7. Wedge Film Journal Bearings. 8. Squeeze Film Journal Bearings. 9. Properties of Sliding Contact Bearing Materials. 10. Materials used for Sliding Contact Bearings. 11. Lubricants. 12. Properties of Lubricants. 13. Terms used in Hydrodynamic Journal Bearings. 14. Bearing Characteristic Number and Bearing Modulus for Journal Bearings.

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