vorlesung engl

UniversitätUniversität SiegenSiegenInstitut für KonstruktionInstitut für KonstruktionDr Martina ZimmermannDr Martina Zimmermann

Machine ElementsMachine Elements

04. Rolling and slide bearings 04. Rolling and slide bearings

UniversitätUniversität SiegenSiegenInstitut für KonstruktionInstitut für Konstruktion

Machine ElementsMachine ElementsDr Martina ZimmermannDr Martina Zimmermann

04. Rolling and slide bearings04. Rolling and slide bearings 04.104.1

Rolling bearingsRolling bearings

FAG PC-Catalogue




Structure of rolling element bearingsStructure of rolling element bearings

SKF Interactive Engineering Catalogue SKF Interactive Engineering Catalogue




Different types of rolling elementsDifferent types of rolling elements

SKF Interactive Engineering Catalogue

Roloff / Mattek: Maschinenelemente




Classification of rolling bearingsClassification of rolling bearings

Spotts/Shoup: Design of Machine Elements

Spotts/Shoup: Design of Machine Elements




Radial deep groove ball bearingsRadial deep groove ball bearings•• are complete units consisting of a are complete units consisting of a

machined inner and outer ring machined inner and outer ring without filling slot and a ball and without filling slot and a ball and cage assemblycage assembly ((can can also also be said be said for the following bearing typesfor the following bearing types))

•• can support radial forces as well can support radial forces as well as low axial forces in both as low axial forces in both directions directions

•• are suitable for high to very high are suitable for high to very high speedsspeeds

•• have very low operational and have very low operational and maintenance requirements

INA-Schaeffler KG: medias®-R

maintenance requirements





Axial thrust ball bearingsAxial thrust ball bearings•• can support high axial forces in can support high axial forces in

one or two directionsone or two directions•• may not be loaded with radial may not be loaded with radial

forcesforces•• have modest speed capabilityhave modest speed capability•• are primarily used for vertical are primarily used for vertical

shaftswww.ina.de

shaftstwo directionaltwo directional

one directionalone directional

SKF Interactive Engineering Catalogue SKF Interactive Engineering Catalogue




Angular contact ball bearingsAngular contact ball bearings•• have a contact angle varying from have a contact angle varying from

15 to 40°15 to 40°•• are particularly suitable for are particularly suitable for

combined loads combined loads -- radial, axial, radial, axial, and moment loadingand moment loading

•• can support axial forces in both can support axial forces in both directions if a duplex pair is directions if a duplex pair is mountedmounted

•• are also designed in a split ring are also designed in a split ring version to support biversion to support bi--directional directional thrust loads with a single bearing

SK

F In

tera

ctiv

e E

ngin

eerin

g C

atal

ogue

SK

F In

tera

ctiv

e E

ngin

eerin

g C

atal

ogue

thrust loads with a single bearing

SK

F In

tera

ctiv

e E

ngin

eerin

g C

atal

ogue

INA

-Sch

aeffl

erK

G: m

edia

s®-R




Self aligning ball bearingsSelf aligning ball bearings•• have an outerhave an outer--race ball path race ball path

ground in a spherical shapeground in a spherical shape•• can accept high levels of can accept high levels of

misalignment

www.askubal.de

misalignment

SK

F In

tera

ctiv

e E

ngin

eerin

g C

atal

ogue




Cylindrical roller bearingsCylindrical roller bearings•• have very high dynamic and have very high dynamic and

static basic load ratings in full static basic load ratings in full complement execution due to the complement execution due to the maximum number of cylindrical maximum number of cylindrical rollersrollers

•• with either a cage or spacers are with either a cage or spacers are suitable for higher speeds due to suitable for higher speeds due to the low frictional momentthe low frictional moment

•• have high rigidityhave high rigidity•• can be relubricatedcan be relubricated•• are available as nonare available as non--, semi, semi--

locating or locating bearingslocating or locating bearings•• can be applied only where can be applied only where

misalignment is very slight



misalignment is very slight




Needle bearingsNeedle bearings•• have a particularly space saving have a particularly space saving

designdesign•• can be mounted without inner or can be mounted without inner or

also outer ring if the shaft resp. also outer ring if the shaft resp. the housing have hardened and the housing have hardened and ground surfaces as racewaysground surfaces as raceways

•• can have a machined outer ring can have a machined outer ring or a thinor a thin--walled, drawn outer cup

INA

-Sch

aeffl

erK

G: m

edia

s®-R

walled, drawn outer cupS

KF

Inte

ract

ive

Eng

inee

ring

Cat

alog

ue

SK

F In

tera

ctiv

e E

ngin

eerin

g C

atal

ogue

INA

-Sch

aeffl

erK

G: m

edia

s®-R




Tapered roller bearingsTapered roller bearings•• can support high radial and axial can support high radial and axial

forcesforces•• can be loaded by axial loading in can be loaded by axial loading in

both direction if two bearings, one both direction if two bearings, one reversed, are mountedreversed, are mounted

SKF Interactive Engineering CatalogueSKF Interactive Engineering Catalogue www.askubal.de




Spherical roller bearingsSpherical roller bearings•• are designed for very high loadsare designed for very high loads•• consist of two rowed symmetric consist of two rowed symmetric

spherical rollers rolling in spherical rollers rolling in spherical shaped outer ring spherical shaped outer ring racewaysraceways

•• can therefor accept misaligncan therefor accept misalign--ments and deflections of the ments and deflections of the shafts

SK

F In

tera

ctiv

e E

ngin

eerin

g C

atal

ogue

shafts

www.askubal.de





Cylindrical roller thrust bearingsCylindrical roller thrust bearings•• require hardened and ground require hardened and ground

surfaces or washers as racewayssurfaces or washers as raceways•• have a low axial section heighthave a low axial section height•• can support high axial forces in can support high axial forces in

one directionone direction•• act as nonact as non--locating bearings in locating bearings in

the radial directionthe radial direction•• have a high rigidity

SK

F In

tera

ctiv

e E

ngin

eerin

g C

atal

ogue

have a high rigidity INA-Schaeffler KG: medias®-R

SKF Interactive Engineering Cataloguec





Sealed bearingsSealed bearings•• Because bearings are very sensitive they have Because bearings are very sensitive they have

to be protected against contamination and to be protected against contamination and spray water.spray water.

•• Sealed bearings can be mounted to avoid Sealed bearings can be mounted to avoid using expensive seals between shafts and using expensive seals between shafts and housings.housings.

•• Sealed bearings get a whole life lubrication Sealed bearings get a whole life lubrication during assembly.during assembly.

•• They are suitable for operating temperatures They are suitable for operating temperatures from from --20 °C to 120 °C, limited by the grease 20 °C to 120 °C, limited by the grease and sealing ring and cage materials.and sealing ring and cage materials.

•• NonNon--contact seals have a low friction. Contact contact seals have a low friction. Contact seals do not loose lubricant during a stop.


gap seals (nongap seals (non--contact)contact)


lip seals (contact)lip seals (contact)seals do not loose lubricant during a stop.




Bearing classification acc. to the Bearing classification acc. to the load directionload direction




Identification structure from DIN 623Identification structure from DIN 623

S6205.2RSR.W203BS6205.2RSR.W203B

NU2314ENU2314E




Identification structure from DIN 623Identification structure from DIN 623

Roloff / Matek




Arrangement of bearingsArrangement of bearings•• A mA minimum inimum of of two bearings two bearings isis needed to support and guide a rotating needed to support and guide a rotating

shaft. Depending on the application it shaft. Depending on the application it has to has to be designed as be designed as aa locatinglocating--nonnon--locating bearing, a preloaded bearing locating bearing, a preloaded bearing oror a floating mounting.a floating mounting.

•• LocatingLocating--nonnon--locating bearing:locating bearing:–– VariationVariationss of bearing distance due to process tolerances and temperature of bearing distance due to process tolerances and temperature

differences are adjusted by the nondifferences are adjusted by the non--locating bearing.locating bearing.–– A A nnonon--locating bearing is movable within the bearing itself, in the filocating bearing is movable within the bearing itself, in the fit in the t in the

housing or at the shaft.housing or at the shaft.–– In contrastIn contrast,, a locating bearing can support a locating bearing can support thrustthrust forcesforces as it is completely as it is completely

fixedfixed in in the the axial axial directiondirection..•• Preloaded bearingPreloaded bearing

–– Two Two rreversed mounted angular contact bearings or tapered roller bearieversed mounted angular contact bearings or tapered roller bearings.ngs.–– The axial clearance of the bearing can be set.The axial clearance of the bearing can be set.

•• The floating mounting is an economical solution if a axial guideThe floating mounting is an economical solution if a axial guide is is unnecessary. The shaft can be axially moved.unnecessary. The shaft can be axially moved.




Arrangement of bearingsArrangement of bearings

Roloff/Matek: Maschinenelemente




Arrangement of bearingsArrangement of bearings





•• A tandemA tandem--arrangement can support high axial forcearrangement can support high axial forcedd, which will be , which will be distributed equally on both bearings.distributed equally on both bearings.

•• The XThe X-- and Oand O--arrangement is used for preloaded bearingarrangement is used for preloaded bearingss and/or for and/or for supporting bisupporting bi--directional axial loads.directional axial loads.

•• The XThe X--arrangement is arrangement is chosenchosen if the shaft if the shaft becomesbecomes warmer than the warmer than the housing, because thehousing, because the diametraldiametral clearance is not reduced. But it cannot clearance is not reduced. But it cannot accept misalignments.accept misalignments.

•• The OThe O--arrangement is preferred arrangement is preferred whenwhen the housing is warmer than the the housing is warmer than the shaft. It is less sensitive against misalignments.

TandemTandem--, X, X-- and Oand O--arrangementarrangement

shaft. It is less sensitive against misalignments.

tandem tandem OO XX




Fixing Fixing devices for bearingsdevices for bearings





LocatingLocating/non/non--locating bearing locating bearing IIKünne: Einführung in die Maschinenelemente

This example shows This example shows the the designdesign of a locating and nonof a locating and non--locating bearing combination which will locating bearing combination which will bebe foundfound ratherrather frequently in practice. The shaft rotates while it is subjectedfrequently in practice. The shaft rotates while it is subjected to a stationary to a stationary loadload derivingderiving from the gear wheel. The force is introduced by the mating gear.from the gear wheel. The force is introduced by the mating gear. This load This load situationsituation leads to a rotation of the inner ringleads to a rotation of the inner ring while the gear force is stationary. As the inner ring while the gear force is stationary. As the inner ring is thus subjected to a peripheral force, it isis thus subjected to a peripheral force, it is mounted on the shaft with a press fit. In contrast to mounted on the shaft with a press fit. In contrast to the inner ring, the outer ring of the bearingthe inner ring, the outer ring of the bearing is subjected to a lumped force and can therefore is subjected to a lumped force and can therefore be mounted into the housing by means of abe mounted into the housing by means of a loose fit or a press fit. The bearing on the left side loose fit or a press fit. The bearing on the left side is designed as the locating bearing. The outeris designed as the locating bearing. The outer ring is fixed by a cap which is screwed to the ring is fixed by a cap which is screwed to the housing, whereas the inner ring sits close to thehousing, whereas the inner ring sits close to the shaft shoulder on the one side and is fixed by shaft shoulder on the one side and is fixed by means of a distance bush on the other side. Onmeans of a distance bush on the other side. On the right hand side the bearing is designed as the right hand side the bearing is designed as a nona non--locating bearing. The inner ring is fixed in thlocating bearing. The inner ring is fixed in the e same way as the same way as the locating locating oneone. The outer . The outer ring can endure a certain movement as thering can endure a certain movement as the outer ring is not fixed in the axial direction. outer ring is not fixed in the axial direction.




LocatingLocating/non/non--locating bearinglocating bearing IIIIKünne: Einführung in die Maschinenelemente

Due to the eccentric wheel, the force deriving from this device Due to the eccentric wheel, the force deriving from this device is a rotary one. This kind of is a rotary one. This kind of shaftshaft could could for examplefor example be the driving device for a vibratory plate. As the external fobe the driving device for a vibratory plate. As the external force rce (coming from the(coming from the centrifugal force of the eccentric mass) rotates together with tcentrifugal force of the eccentric mass) rotates together with the shaft, the he shaft, the force on the alsoforce on the also rotating inner ring is a lumped force. As the outer ring of the rotating inner ring is a lumped force. As the outer ring of the bearings is bearings is stationary, they arestationary, they are subjected to a subjected to a periphericalperipherical force. Therefore the outer rings have to be force. Therefore the outer rings have to be mounted into the housingmounted into the housing by using a press fit, whereas the combination of inner ring and by using a press fit, whereas the combination of inner ring and shaft can optionally be realisedshaft can optionally be realised by a press or a loose fit. Because of the load situation the by a press or a loose fit. Because of the load situation the inner ring of one of the bearings isinner ring of one of the bearings is designed as the nondesigned as the non--locating part.locating part.




LocatingLocating/non/non--locating bearinglocating bearing IIIIIIKünne: Einführung in die Maschinenelemente

In this example the nonIn this example the non--locating bearing is realised by means of a cylindrical roller belocating bearing is realised by means of a cylindrical roller bearing.aring.The cylindrical roller bearing is capable of enduring higher radThe cylindrical roller bearing is capable of enduring higher radial loads than the ball bearing,ial loads than the ball bearing,but apart from this advantage this bearing arrangement can be cobut apart from this advantage this bearing arrangement can be compared with the first one.mpared with the first one.




LocatingLocating/non/non--locating bearinglocating bearing IVIVKünne: Einführung in die Maschinenelemente

In this example the load situation cannot be defined clearly witIn this example the load situation cannot be defined clearly with regard to lumped or h regard to lumped or periphericalperipherical loadloadss on the inner and outer ring. Because of the gear wheel and the on the inner and outer ring. Because of the gear wheel and the eccentric eccentric wheel both loadwheel both load cases are possible. For this reason both the outer and the innercases are possible. For this reason both the outer and the inner ring should ring should be mounted onbe mounted on the shaft respectively into the housing by a press fit. Neverthethe shaft respectively into the housing by a press fit. Nevertheless one of the less one of the bearings has to bebearings has to be designed as a nondesigned as a non--locating bearing. Therefore a cylindrical roller bearing locating bearing. Therefore a cylindrical roller bearing is introduced, where theis introduced, where the cylinder is not embedded in the inner ring and thus allows an axcylinder is not embedded in the inner ring and thus allows an axial ial movement.movement.




LocatingLocating/non/non--locating bearinglocating bearing VVKünne: Einführung in die Maschinenelemente

The design of this bearing situation is supposed to endure high The design of this bearing situation is supposed to endure high radial as well as thrust radial as well as thrust forces. The nonforces. The non--locating bearing is realised by means of a cylindrical roller belocating bearing is realised by means of a cylindrical roller bearing with a aring with a „free“ inner ring. The locating bearing is designed as a combina„free“ inner ring. The locating bearing is designed as a combination of a ball bearing to tion of a ball bearing to endure the thrust forces and a cylindrical roller bearing to endendure the thrust forces and a cylindrical roller bearing to endure the radial forces. Because ure the radial forces. Because of this separation of the forces, the outer ring of the ball beaof this separation of the forces, the outer ring of the ball bearing has a radial clearance. As ring has a radial clearance. As the cylindrical roller of the second bearing is not embedded intthe cylindrical roller of the second bearing is not embedded into the inner ring, it will definitely o the inner ring, it will definitely not not endreendre any thrust forces, thus realising a clear separation of the forany thrust forces, thus realising a clear separation of the forces.ces.




LocatingLocating/non/non--locating bearinglocating bearing VIVIKünne: Einführung in die Maschinenelemente

In this case the bearing combination is designed by a pair of spIn this case the bearing combination is designed by a pair of spherical roller bearings andherical roller bearings andplummerplummer blocks for roller bearings on both sides. With this solution blocks for roller bearings on both sides. With this solution misalignementsmisalignements can becan becompensated. As the bearings are fixed on the shaft by means of compensated. As the bearings are fixed on the shaft by means of clamping sleeves, it canclamping sleeves, it canbe manufactured from a simple blanc be manufactured from a simple blanc semifinishedsemifinished product, which must not be further product, which must not be further cuttedcutted..The driving device is also fixed on the shaft by means of a clamThe driving device is also fixed on the shaft by means of a clamping sleeve. This way of fixationping sleeve. This way of fixationshould only be realised if a precise axial should only be realised if a precise axial alignementalignement of the mounted elements is not required.of the mounted elements is not required.This would for example be the case for the design of an axle of This would for example be the case for the design of an axle of a simple railway vehicle,a simple railway vehicle,whereas this kind of fixation (by means of clamping sleeves) wouwhereas this kind of fixation (by means of clamping sleeves) would not be reasonable for a ld not be reasonable for a gear system.gear system.




Bearing of a Bearing of a slewing crane columnslewing crane column

Force: very high axial forces acc. to the lifting mass and the dead load of the crane, very high radial forces as well due to the overturning moment of the above mentioned forces

Design: A combination of a locating bearing system of a radial spherical roller bearing and a spherical roller thrust bearing. With regard to the design of this bearing combination the center point of the radius of the thrust bearing has to correspond with the one of the radial bearing. This can be adjusted by means of a distance ring.





Bearing of a Bearing of a gear shaftgear shaft

Force: as the gearing system is realised by means of a helical gear wheel, both radial as well as axial loads have to be supported

Design: simple and economical design by means of two deep groove ball bearings, both bearings are realised as a non-locating bearing in order to enable an axial clearance to compensate possible thermal expansions, this floating bearing design can only be realised when a constant sense of rotation is given





Bearing of a Bearing of a crane trolleycrane trolley


Force: very high radial loads but minor thrust loads (due to possible tilting motion, acceleration and braking forces of the crane trolley

Design: two spherical roller bearings designed as floating bearing arrangement, the axial clearance is realised by leaving the position of the inner ring non-located




Wheel bearing Wheel bearing of a of a building machinebuilding machine


Force: high radial forces and average to high axial loads due to bending manoeuvres

Design: Two tapered roller bearings which are arranged in a laterally reversed way, the axial clearance of the two bearings can be adjusted by means of a castel nut




Bearing in a Bearing in a worm gear driveworm gear driveForce: the worm brings mostly axial forces into the system and only minor radial forces, whereas the worm gear induces mostly radial forces

Design: The bearing of the worm is realised by means of a locating and a non-locating bearing, the locating one being designed by means of two angular contact ball bearing, which are arranged in a X-position so as to get a less rigid design which can also adjust to certain misalignments, the non-locating bearing is given by a cylindrical roller bearing; for the bearing system of the gear wheel a combination of a deep groove ball bearing as a locating bearing and a cylindrical roller bearing as the non-locating bearing





Designing rolling bearingsDesigning rolling bearings




Dynamically loaded rolling bearingsDynamically loaded rolling bearings

0

a0

CFf ⋅

eFF?e

FF

r

a

r

a >≤

p

U,10 PCL ⎟⎠⎞

⎜⎝⎛=

nL

L 10,Uh,10 =

P = X·Fr + Y·Fa

thrust indexthrust index

equivalent equivalent radial loadradial load

expected life in revolutionsexpected life in revolutions

= taken from manufacturers catalogue= taken from manufacturers catalogueexpected life in operating hoursexpected life in operating hours= taken from calculation of reaction forces= taken from calculation of reaction forces




Extended life time calculationExtended life time calculation

•• LLnana: life time according to extended calculation: life time according to extended calculation•• LL: life time from standard calculation in revolutions (: life time from standard calculation in revolutions (LL10,U10,U) or hours () or hours (LL10,h10,h))•• aa11::

LL22

22

0.330.33LL11

11

0.210.21

failure probability in failure probability in %%sign for life timesign for life timefactor factor aa11

LL1010

1010

11LL55

55

0.620.62LL44

44

0.530.53LL33

33

0.440.44

150 °C150 °C 11200 °C200 °C 0.730.73250 °C250 °C 0.420.42300 °C300 °C 0.220.22

operatingoperatingtemperaturetemperature

temperaturetemperaturefactor factor fftt

•• aa22::•• aa33::•• fftt::




Characteristics of angular contact Characteristics of angular contact bearingsbearings

Within angular contact bearings the radial forces create additioWithin angular contact bearings the radial forces create additional nal thrust forces. For tapered roller bearings and angular contact bthrust forces. For tapered roller bearings and angular contact ball all bearings these thrust forces have to be included into the calculbearings these thrust forces have to be included into the calculation ation of the equivalent load (in addition to the external thrust forceof the equivalent load (in addition to the external thrust forces).s).

load conditionsload conditions thrust force thrust force FFaa,calc,calc which has which has to be used for calculation of to be used for calculation of equivalent radial load equivalent radial load PP

B

rB

A

rA

YF

YF

≤

B

rB

A

rA

YF

YF

>

⎟⎠

⎞⎜⎝

⎛−⋅>

B

rB

A

rAa Y

FYF5.0F

⎟⎠

⎞⎜⎝

⎛−⋅≤

B

rB

A

rAa Y

FYF5.0F

thrust force thrust force FFaa,calc,calc which has which has to be used for calculation of to be used for calculation of equivalent radial load equivalent radial load PP

thrust force thrust force FFaa,calc,calc which has which has to be used for calculation of to be used for calculation of equivalent radial load equivalent radial load PP

oror

andand

B

rB

A

rA

YF

YF

≤ andand

B

rBacalc,a Y

F5.0FF ⋅+=

aA

rAcalc,a F

YF5.0F −⋅=

bearing Abearing A

bearing Bbearing B

definition of definition of bearing A and bearing A and

bearing Bbearing B

Künne: Einführung in dieMachinenelemente




Statically loaded rolling bearingsStatically loaded rolling bearings

P0 = X0·Fr + Y0·Fastatic equivalent radial loadstatic equivalent radial load

mins0

0s f

PCf ≥=

application application typetype

static indexstatic index

1.5 ... 2.51.5 ... 2.5 highhigh1.0 ... 1.51.0 ... 1.5 mediummedium

lowlow

static minimumstatic minimum--index index ffs s minmin

kind ofkind ofdemanddemand

machine toolmachine toolgeneral machine designgeneral machine designfarming a. building machinesfarming a. building machines0.7 ... 1.00.7 ... 1.0

example for applicationexample for application

= taken from manufacturers catalogue= taken from manufacturers catalogue

= taken from bearing loading= taken from bearing loading




Example: Design data for radial deep groove Example: Design data for radial deep groove ball bearing DIN 625ball bearing DIN 625--62086208

valid only for bearingvalid only for bearingDIN 625DIN 625--6208

valid for all deepvalid for all deepgroove ball bearings


6208 groove ball bearings

basic dynamic load rating basic dynamic load rating CC

40 mm40 mm

80 mm80 mm

18 mm18 mm

1.1 mm1.1 mm

inner diameter inner diameter ddouter diameter outer diameter DDwidth width BBradius radius rrs s minmin

1414factor factor ff00

18 18 kNkNbasic static load rating basic static load rating CC00

29 29 kNkN

speed limitspeed limit 20000 min20000 min--11

0

a0

CFf ⋅ e

FF

r

a ≤ eFF

r

a >

0.30.3 0.220.22

eeYYXX

0011YYXX

220.560.56

0.50.5 0.240.24 0011 1.81.80.560.56

0.90.9 0.280.28 0011 1.581.580.560.56

1.61.6 0.320.32 0011 1.41.40.560.56

33 0.360.36 0011 1.21.20.560.56

66 0.430.43 0011 110.560.56

valid for all bearingsvalid for all bearings

8.0FF

r

a ≤

8.0FF

r

a >

YY00XX00

0011

0.50.50.60.633

life cycle index life cycle index ppball bearingsball bearingsroller bearingsroller bearings 10/310/3




AuxiliaryAuxiliary faktorfaktor ff00 for bearing dimensioningfor bearing dimensioning

Künne – Einführung in den Maschinenbau




Slide bearingsSlide bearings





Modes of frictionModes of friction

Decker: Maschinenelemente

11 moving bodymoving body22 stationary bodystationary body33 lubricantlubricant44 movementmovement55 loadload




Comparison betweenComparison betweenrolling bearingsrolling bearings

•• Starting friction is low Starting friction is low –– a desirable a desirable feature for intermittent service or feature for intermittent service or for starting at low temperatures.for starting at low temperatures.

•• Loads can be inclined at any angle Loads can be inclined at any angle in the transverse plane.in the transverse plane.

•• Maintenance costs are low.Maintenance costs are low.•• Bearings are easily replaced when Bearings are easily replaced when

worn out.worn out.•• Less axial space is required than Less axial space is required than

for slide bearings. Shafts are thus for slide bearings. Shafts are thus shorter, and may even be smaller shorter, and may even be smaller in diameterin diameter

•• Thrust loads can be supported.Thrust loads can be supported.

•• Operation is quieter than with Operation is quieter than with rolling bearings, especially after rolling bearings, especially after first wear effects.first wear effects.

•• There is less difficulty with There is less difficulty with fatigue.fatigue.

•• First cost is usually lower.First cost is usually lower.•• They are less easily injured by They are less easily injured by

foreign particles.foreign particles.•• Less radial space is required than Less radial space is required than

for rolling bearings.for rolling bearings.

•• They are better suited to overload They are better suited to overload and shock conditions.and shock conditions.

andand slide bearingsslide bearings

Spotts / Shoup: Design of Machine Elements




Pressure distribution around a Pressure distribution around a journal bearingjournal bearing


The lubricating grooves have to be positioned outside the pressuThe lubricating grooves have to be positioned outside the pressure zone (a) of the re zone (a) of the slide bearing. Otherwise the supporting oil film will be interruslide bearing. Otherwise the supporting oil film will be interrupted (b).pted (b).




Hydrodynamic slide bearingsHydrodynamic slide bearings

Dec

ker:

Mas

chin

enel

emen

te

Because of the viscous shear stresses developed in the oil, the Because of the viscous shear stresses developed in the oil, the moving journal moving journal draws oil into the converging, wedgedraws oil into the converging, wedge--shaped area above the region of contact. shaped area above the region of contact. The resulting pumping action produces a pressure in the oil filmThe resulting pumping action produces a pressure in the oil film which lifts the which lifts the journal from the bearing. The boundary lubrication and the mixedjournal from the bearing. The boundary lubrication and the mixed--film lubrication film lubrication precede the fullprecede the full--film lubrication.film lubrication.




Radial slide bearing bushesRadial slide bearing bushes

INA-Schaeffler KG: medias®-RINA-Schaeffler KG: medias®-R




Standardised radial slide bearingsStandardised radial slide bearings





Thrust slide bearingsThrust slide bearings





FixedFixed--incline thrust slide bearingincline thrust slide bearing

Hamrock: Fundamentals of Machine Elements





PivotedPivoted--pad thrust slide bearingpad thrust slide bearing






Pivoted pads of thrust slide bearingsPivoted pads of thrust slide bearings





Bearing materialsBearing materials•• TinTin-- and leadand lead--basebase babbittsbabbitts: quickly run in, assume very smooth : quickly run in, assume very smooth

surfaces, good conformability andsurfaces, good conformability and embeddabilityembeddability•• Bronze: suitable for high loads and slow speeds, low misalignmenBronze: suitable for high loads and slow speeds, low misalignmentsts•• Copper lead: suitable for high loads, low misalignmentsCopper lead: suitable for high loads, low misalignments•• CastCast--iron: bearing can be lubricated by graphite inclusions in case oiron: bearing can be lubricated by graphite inclusions in case of f

missing lubricantmissing lubricant•• Porous bearings: “self lubricating” bearings are made of sinteriPorous bearings: “self lubricating” bearings are made of sintering ng

powdered metal and then impregnated with oil. powdered metal and then impregnated with oil. •• Carbon and plastic: for high temperature service,Carbon and plastic: for high temperature service, teflonteflon has an has an

extremely low coefficient of friction, no lubricant is required;extremely low coefficient of friction, no lubricant is required; high loadshigh loads•• LaminatedLaminated phenolicphenolic bearings: plastic bearings formed by impregnated bearings: plastic bearings formed by impregnated

paper with the paper with the phenolic phenolic resin, formed into shape and then curing by heat resin, formed into shape and then curing by heat and pressure; good resistance against corrosion, fatigue and shoand pressure; good resistance against corrosion, fatigue and shockck

•• Rubber and woodRubber and wood•• Bonded coatingsBonded coatings Spotts / Shoup: Design of Machine Elements




Hydrostatic slide bearingsHydrostatic slide bearingsIn hydrostatic (also called externally pressurised) lubricated bIn hydrostatic (also called externally pressurised) lubricated bearings the earings the bearing surfaces are separated by a fluid film maintained by a pbearing surfaces are separated by a fluid film maintained by a pressure ressure source outside the bearing. These bearings avoid the disadvantagsource outside the bearing. These bearings avoid the disadvantages of es of necessary high speeds and constant operation in order to establinecessary high speeds and constant operation in order to establish the sh the liquid friction mode. Moreover the shaft does not run eccentricaliquid friction mode. Moreover the shaft does not run eccentrically in the lly in the bearing. The characteristics of hydrostatic slide bearings are:bearing. The characteristics of hydrostatic slide bearings are:

•• extremely low frictionextremely low friction•• extremely high loadextremely high load--carrying capacity at low speedscarrying capacity at low speeds•• high positional accuracy in highhigh positional accuracy in high--speed, lightspeed, light--load applicationsload applications•• a lubrication system more complicated than that for slider bearia lubrication system more complicated than that for slider bearingsngs

Therefore hydrostatic slide bearings are only used when the requTherefore hydrostatic slide bearings are only used when the requirements irements are extreme, as in large telescopes and radar tracking units, whare extreme, as in large telescopes and radar tracking units, where ere extremely heavy loads and extremely low speeds are used; or in mextremely heavy loads and extremely low speeds are used; or in machine achine tools, where extremely high speeds, light loads and gas lubricantools, where extremely high speeds, light loads and gas lubricants are ts are used.used.




Set up of hydrostatic slide bearingsSet up of hydrostatic slide bearings
