rolling contact bearings nbc jaipur

7/23/2019 rolling contact bearings nbc jaipur

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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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rolling contact bearings nbc jaipur

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