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Introduction Types of bearings Rolling Contact Bearings Construction Classication Bearing Types Bearing Life Merits & Demerits
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Introduction toIntroduction to
bearingsbearingsObjectie of bearing is to proiderelatie positioning and rotationalfreedom !"ile transmitting a load
bet!een t!o parts#
In rolling contact bearings as t"ename implies t"e friction is of rollingtype#
It is muc" smaller t"an t"e sliding
type#
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Rolling Contact BearingsRolling Contact Bearings
load is transferred t"roug" rolling elements suc"as balls$ straig"t and tapered cylinders and sp"ericalrollers#
Journal (sleeve) BearingsJournal (sleeve) Bearings
load is transferred t"roug" a t"in lm oflubricant %oil#
Types of bearingsTypes of bearings
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Rolling Contact BearingsRolling Contact Bearings
Rolling contact bearings are also known as antifriction
bearings.
The load, speed, and operating viscosity of the lubricant
affect the friction characteristics of a rolling bearing.
These bearings provide coefficients of friction between
0.001 and 0.002.
The designer must deal with such matters as fatigue,
friction, heat, lubrication, kinematics problems, material
properties, machining tolerances, assembly, use and cost
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T"e rolling contact bearings are composed offour elements#
i#Outer raceii#Inner raceiii#Rolling elementi#Cage of retaining ring
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Roller contact bearing
With its parts
i.Outer ring (or) Outerrace
ii.Inner ring (or) inner
race
iii.Rolling elements
iv.Cage or retaining ring
Construction Diagram :
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Classifcation o rolling bearings
i.Ball BearingDeep groove (Conrad) bearing
Filling notch ball bearingAngular contact bearings (AC)
ii.Roller Bearing
Cylindrical bearingsNeedle bearings
Tapered bearings
Spherical bearings
Classified into two types
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Ball BearingsBall Bearings
Deep groove bearingDeep groove bearing
Single row of deep groove ball bearing can combinational ofradial and thrust load.Load capacity is limited by the number of ballsPrimarily designed to support radial loads, the thrust capacity
is about 70% of radial load capacity
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Filling notch ball bearings
Bearings have the same basic radial construction as
Conrad type. However, afilling notch(loading groove)
permits more balls to be used.
Radial load capacity is 20 40% higher than Conradtype.Thrust load capacity drops to 20% (2 directions) of
radial load capacity.
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Angular contact Ball bearings (AC)
The centerline of contact between the balls and the raceway is at an
angle to the plane perpendicular to the axis of rotation.
Used for high radial and thrust load applications
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RADIAL AND ANGULAR BEARINGRADIAL AND ANGULAR BEARING
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Standardization of bearings
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Roller Bearings
Roller bearings "ae "ig"er load capacity t"an ball
bearings$ load is transmitted t"roug" line contact instead
of point contact#
'elical rollers are made by !inding rectangular
material into roller# Due to in"erent (e)ibility t"ey are
capable of ta*ing considerable misalignment#
+ roller !it" lengt" muc" larger t"an diameter is
*no!n as needle roller and are used !"ere radial space is
limited# Cage nay be absent in needle roller bearings#
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ROLL,R B,+RI-./ROLL,R B,+RI-./
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If a bearing is clean$ properly lubricated and mounted and is
operating at reasonable temp#$ failure is due to fatigue causedby repeated contact stresses%'ert0ian stress
1atigue failure consists of a spalling or pitting of t"e cured surfaces
1ailure criterion 2 spalling or pitting of an area of 3#34 in5$Tim*en company %tapered bearings
/palling
crac* initiates belo! t"e cured surface at t"e location of
ma)imum s"ear stress$ propagates to t"e surface causingsurface damage#
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LI1, number of reolution or "ours of operation$ atconstant speed$ re6uired for t"e failure criterion to
deelop#
L43 7 833 %"ours ) 99#99 %rpm ) :3 7 43:7 4 million
reolutions
1or ball bearings and sp"erical bearings;
1or tapered bearings manufactured by
Tim*en;L43 7 9333 %"ours ) 833 %rpm ) :3 7
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Bearing LifeBearing Life
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Bearing lifeBearing life
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PRELOADING OF BEARINGPRELOADING OF BEARING
=reloading or Duple)ing is used toeliminate t"e play or clearance in eit"er
radial or a)ial direction of ball bearing tobe used for precision mac"ine tool#
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Lo! starting and good operating friction tor6ue#
,ast of lubrication
Re6uiring less a)ial space#
.enerally$ ta*ing bot" radial and a)ial loads#
Rapid replacement
>arning of impending failure by increasing
noisiness#
.ood lo!?temperature starting#
Merits of Rolling contact bearingsMerits of Rolling contact bearings
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.reater diametric space#
More seere alignment re6uirements#
'ig"er initial cost# -oisier normal operation#
1inite life due to eentual failure by
fatigue#
,ase of damage by foreign matter#
=oor damping ability#
Demerits of rolling element bearings;Demerits of rolling element bearings;
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