Machine Elements in Mechanical Design FIFTH EDITION CHAPTER

Machine Elements in Mechanical Design FIFTH EDITION CHAPTER 14 Rolling Contact Bearings Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Types of Rolling Contact Bearings • Radial loads: act toward center of bearing along a radius • Thrust loads: act parallel to axis of the shaft • Misalignment: angular deviation of axis of the shaft at bearing from true axis of bearing itself Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Table 14 -1 Comparison of Bearing Types Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Types of Rolling Contact Bearings • • Single-row, deep-groove ball bearing Double-row, deep-groove ball bearing Angular contact ball bearing Cylindrical roller bearing Needle bearing Spherical roller bearing Tapered roller bearing Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Thrust Bearings • Thrust Bearings § Bearing that resists only thrust loads § Rolling elements: spherical balls, cylindrical rollers, tapered rollers § Can take little or no radial load Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Mounted Bearings • Mounted Bearings § Sometimes called housed bearings § Means of attaching bearing unit directly to frame of machine with bolts § Pillow block: most common configuration for mounted bearing § Flange units: mounted on vertical side frames of machines, holding horizontal shafts Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Bearing Materials • Balls, rollers, races: very hard, highstrength steel or ceramic • Metallic materials: titanium/nickel alloys and Monel metal (alloys of nickel, copper, cobalt) • Where lighter loads encountered or resistance to corrosion by specific materials needed, plastic bearings can be used. Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Table 14 -2 Comparison of Bearing Materials Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Load/Life Relationship • All bearings have finite life. • Eventually fail due to fatigue because of high contact stresses • Lighter the load, the longer the life; vice versa Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Bearing Manufacturers' Data • Selection of rolling contact bearing from a manufacturer's catalog: load-carrying capacity and geometry of bearing § Standard bearings: extra-light, medium, heavy classes § Basic static load rating; basic dynamic load rating Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Table 14 -3 Dimensions for Single Row, Deep-groove Ball Bearings Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Table 14 -3 (continued) Dimensions for Single Row, Deep-groove Ball Bearings Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Table 14 -3 (continued) Dimensions for Single Row, Deep-groove Ball Bearings Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Table 14 -3 (continued) Dimensions for Single Row, Deep-groove Ball Bearings Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Table 14 -3 (continued) Dimensions for Single Row, Deep-groove Ball Bearings Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Table 14 -3 (continued) Dimensions for Single Row, Deep-groove Ball Bearings Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Design Life • Design Life § Specified by designer, considering the application. Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Table 14 -4 Recommended Design Life for Bearings Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Bearing Selection: Radial Loads Only • Selection of a bearing: load capacity and geometry of bearing ensuring it can be installed conveniently in the machine. § See: Procedure for Selecting a Bearing— Radial Load Only Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Bearing Selection: Radial and Thrust Loads Combined • When both radial and thrust loads exerted on a bearing, the equivalent load is the constant radial load that would produce the same rated life for the bearing as the combined loading. Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Table 14 -5 Radial and Thrust Factors for Single-row, Deep-groove Ball Bearings Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Table 14 -6 Life Adjustment Factors for Reliability, CR Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Mounting of Bearings • Considerations in mounting of a bearing: § Shaft seat diameter and tolerances § Housing internal bore and tolerances § Shaft shoulder diameter against which inner race of bearing will be located Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Mounting of Bearings • Considerations in mounting of a bearing: § Housing shoulder diameter provided for locating the outer race § Radius of the fillets at base of shaft and housing shoulders § Means of retaining the bearing in position Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Tapered Roller Bearings • Radial load on one of the bearings creates a thrust on the opposing bearing. • This must be considered in analysis of bearing. Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Table 14 -7 Tapered Roller Bearing Data Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Practical Considerations in the Application of Bearings • • • Lubrication Installation Preloading Bearing stiffness Operation under varying loads Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Practical Considerations in the Application of Bearings • • Sealing Limiting speeds Standards Tolerances Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Importance of Oil Film Thickness in Bearings • Critical to maintain film of lubricating oil at surface of rolling elements § § § Bearing geometry factors Bearing material factors Lubricant factors Operational factors Recommendations for achieving long life for bearings (Miner's rule) Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved