Tribomechanical Systems in Mechanical Power Transmitters

7/28/2019 Tribomechanical Systems in Mechanical Power Transmitters

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* For correspondence.

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Journal of the Balkan Tribological Association Vol. 18, No 4, 497506(2012)

Mechanism of friction generation and different type at wear inuence

at tribomechanical factors

TRIBOMECHANICAL SYSTEMS IN MECHANICAL POWER

TRANSMITTERS

B. STOJANOVIc*, M. BABIc, N. MARJANOVIc, L. IVANOVIc, A. ILIc

Faculty of Engineering, University of Kragujevac, 6 Sestre Janjic Street,

34 000 Kragujevac, Serbia

E-mail: [email protected]

ABSTRAcT

In this paper, the etaile analysis of tribomehanial systems for transmission of

power an movement in mehanial transmitters is presente. The basi tribolo-

ial harateristis of tribomehanial systems are frition an wear that are the

main ases of systems strtres alterations, enery loss an losses of material.

As natral proesses, the frition an wear, epen on a lare nmber of ifferent

fators: systems strtres, exploitative onitions (spee an loa), mehanial-hemial properties of materials, harateristi of lbriation, aressiveness of

environment, temperatre, toporaphy of ontat srfaes, mehanial proess-

ing (pre-processing and nal processing), etc.

On the basis of the relevant information, the classication of basic tribome-

chanical systems is done. By the analysis of specic tribomechanical systems in

certain mechanical transmitters, the identication of common wear modes, theirs

ases an reommenations for avoiane are one.

Keywords: tribomehanial systems, frition, wear, mehanial power transmit-

ters.

AIMS ANd BAckgROuNd

The tribomehanial systems, as ynami exetors of basi fntions, at in

onitions of frition ontats an in onitions of relative movement of theirs

elements. In the zone of frition ontat, the omplex non stationary physio-hemial an mehanial proesses are ine that are followe by frition an

wear of ontat srfaes.


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The number of inuential factors and complexity of their interactions in

whih variation of one parameter ase hain alterations of ifferent parameters

complicate the quantication of theirs inuences. This is the reason for present

insufciency of systematic information about tribological characteristics of tribo-

mehanial systems.

The triboloial proesses or at basi tribomehanial systems that areompose of 2 elements in ontat in the presene of the lbriant as the thir

element. The existin environment may, bt mst not, affet the triboloial pro-

esses in basi tribomehanial systems.

The nmber of tribomehanial systems in ertain instrial systems may be

more than several tens of thosans. In orer to simplify the analysis of triboloi-

cal processes at contact surfaces, those tribomechanical systems can be classied

in 4 major rops110:

Tribomehanial systems for motion transmission: tribomehanial systems for transmission of rotation in transverse iretion, tribomehanial systems for transmission of rotation in lonitinal iretion, tribomehanial systems for transmission of linear motion , tribomehanial systems for motion brain;

Tribomehanial systems for power transmission;

Tribomehanial systems for transmission of information: tribomehanial systems for protion of information;

Tribomehanial systems for movement an proessin of material: tribomehanial systems for material movement, tribomehanial systems for material formin, tribomehanial systems for material proessin.

TRIBOMEcHANIcAL SYSTEMS AT POWER TRANSMISSIONS

Tribomehanial systems for power transmissions, whih are nown as mehani-

al transmitters, are se for transmission of mehanial motion enery on is-

tanes, so as for transformation of its parameters. Those transmitters simltane-osly transmit the rotary motions.

The eneral se of transmitters is hihly relate to exetin the elementary

fntions with major harateristi that are, amon them: enery istribtion,

retion or inreasin of spee, alternation of motion type, relation of spee,

startin, brain, iretion hanin, et.

The transmission of power an mehanial motion an be one in many if-

ferent ways an by ifferent transmission mehanisms, so the mehanial power

transmitters can be classied in 2 major groups: power transmitters with trans-mission by form, an power transmitters with transmission by frition.

The power transmitters with transmission by form act on the specic form

of triboelements an relate priniples of meshin of ontat srfaes. The fol-


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lowing transmitters are classied in this group of mechanical power transmitter:

ear transmitters, hain transmitters, timin belt transmitters, worm transmitters,

threa transmitters, planetary ear transmitters, caran transmitters, an varia-

tors with meshin.

In the proess of power an motion transmission, the molelarly-mehani-

al natre of frition is involve. The mehanial transmitters that at on the basisof this principle are: belt transmitters, at belt transmitters, friction transmitters,

planetary frition transmitters an frition variators.

Aorin to statistial ata abot proe power transmitters, the most

ommonly se, in area of ontinos transmission ratios, are the ear trans-

mitters (cylindrical, at rst). The share of friction transmitter usage at mechani-

cal power transmitter in usage is signicantly smaller than the share of usage of

power transmitters that transmit power by form onnetion.

The present sae of mehanial power transmitters is hihly relate to e-velopment of mehanial transmitters with ontinally variable transmission ra-

tio, arately, with ontinal spee relation. The share of mehanial power

transmitters in lobal protion of ontinal transmitters is the biest an, from

that aspet the proess of power transmission by frition, has briht perspetive.

Power transmitters are classied in the group of widely used tribomechanical

systems that are neessary for fntionin of mehanial systems of hiher levels.

Furthermore, the qualities of power transmitters are the major inuential factor to

qality of the whole onstrtion1,11

.

MEcHANIcAL POWER TRANSMITTERS WITH FORM TRANSMISSION

In the zone of frition ontat at mehanial transmitters an interations of sys-

tem elements, the omplex non stationary mehanial an physiohemial pro-

esses are ine, so as the proesses of frition an wear.

Processes of friction and wear in mechanical transmitters are dened by

strtre an eneral fntion of the system. As the eneral fntion of the sys-tem at all mehanial transmitters is the same (transport of enery on ertain is-

tance), it is implicated that those processes are highly dened by system structure.

At the mehanial transmitters that wor on the basis of eometrial form

onnetion of elements, the external frition is present. The frition is present at

ontat zones of elements e to relative motion: impat, rollin an sliin.

kinematial analysis of meshin at ylinrial ears impliates that om-

ponents of rrent spees at some ontat point on ommon tanent line to sie

srfae of teeth of mashin ears are not an mst not be in eqivalene. Thatmeans that sie srfae of teeth of mashin ears slies on eah other. The sliin

is not present only when ontat is at entral point an in that ase only rollin is

present (Fi. 1).


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External frition that is present at meshin of ears is resltant of sliin fri-tion an rollin frition. As the iretions an vales of sliin spee are alter-

in rin meshin perio (in interval of time from enter in ontat to exit from

ontat of teeth), it is loial that frition is also alterin rin that interval. The

current values of force and friction coefcient, that are present, are in function of

rrent ontat of meshin tooth1217.

The dening of current value of friction coefcient at every contact point

during the period of meshing is very complex. The basic parameters that inuent

on friction coefcient and sliding speed are changeable in direction and valueduring the period of meshing. From that reason, it is sufcient to use the average

values of friction coefcient that are presented in many systematic information,

at oneptal proere of onstrtion proess.

Worm transmitters, as hyperboloi ear set with axes that intersets are har-

aterise by linear ontat of triboelements (worm-worm wheel). The linear on-

tat is followe by relatively hih level of sliin at mashin elements, bt also

with forming of sufcient layer of lubricant as the third element of tribomechani-

al system. The sliin frition an be hih, so it an ine the low eree of ef-ciency, lower than 0.5 at multiplicators. In case of worm transmitter application

at reductors it is possible to increase the degree of efciency to over than 0.9 by

onstrtion soltions.

Fig. 1. gear power transmitter

pitch circle

pitch circle

base circle

base circle

gear 1

gear 2

pressure line

( = pressure angle)

1,

1,

1

2,

2,

2

C


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chain transmitters are mehanial transmitters whih transmit power an

motion by exible element chain. From the aspect of analysis of the tribologi-

al proesses, the hain transmitters belon to the tribomehanial systems with

omplex strtre18. chain onsists of several basi tribomehanial systems:

pinbshlbriant; bshrollerlbriant; sie srfae of pin lin platesie

srfae of roller lin platelbriant, et. Some tribomehanial systems at hain

power transmitter are presente in Table 1.

The frition as proess that opposes to motion is very intensive rin phase

of enterin in ontat of sproet an hain an in the phase of esent of the

hain element from the sproet.

During the entry phase of contact of chain element and sprocket, at rst, the

roller hits to the teeth of sproet, an after that, bsh an pin hit to the roller as ele-

ments of joint. Impats proe estrtion of the hain an its elements, tooth of

the sproet an proe the noise an impat-yli estrtion of hain elements.

The onstrtional shape of the sproet teeth an its interspaes, rin the

normal meshin provie the normal positionin of the joint on ative part of the

teeth prole. After the impact, the rolling with sliding of roller, at roller chains,

is ine or sliin on bsh, in ase of bsh hains is ine. By that, the pres-

ene of roller ereases intensive wear of tooth sproet e to sliin.

Table 1.Tribomehanial systems at hain transmitters

No

Tribomehanial system Element of

system Type of motiongure nomenlatre

1

1

2 pinbsh

1 pin

impat

sliin2 bsh

2 2

1

bshroller

1 bsh

impat

sliin2 roller

3

2

1

rollersproetteeth

1 roller

impat

sliin

rollin

2 sproet

teeth


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Simltaneosly, the sliin between bsh an pin is present, so as sliin

between the roller and bush with press ts to bush link plate.

Analoe proess of relative motions at tribomehanial elements is present

rin the enin phase of ontat, bt withot impats an their istration effets.

Relative motion at joint is followe by resistane to this motion, so ifferent

frition proesses at ontat srfaes are ine (impats, rollin an sliin).Those proesses are the main ase of losses of enery in transfer, so as the

ases of ifferent types of wear.

Timin belt transmitter, as relatively new onept at power transmission,

uses exible element (toothed belt) for realisation of main function. The combi-

nation of the hain, ear an belt transmission brins a variety of the motion in

tangential, radial and axial directions. This is especially signicant at the phase

of enterin at ontat of belt an plley.

The basi tribomehanial systems at timin belt transmitters are (Fi. 2): belt toothbelt plley tooth (position 1 in Fi. 2),

belt faceange (position 2 in Fi. 2),

the belt rooveapex of the belt plley tooth (position 2 in Fi. 2).

Types of motion that or in these tribomehanial systems are iven in

Table 2.

The initial ontat of timin belt teeth in the enterin phase of ontat starts

Fig. 2.Tribomehanial systems in timin belt rives

13

2

Table 2.Tribomehanial systems an types of motion in timin belt rives1921

Tribomehanial system Type of motion

Belt toothbelt plley tooth

impat

sliin

rollin

Belt faceangeimpat

sliin

The belt rooveapex of the belt plley toothsliin

rollin


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Table. 3. common wear type at mehanial transmitters

Typeof

wear

MehanialTransmitters

casegeneral reommenations for

avoi an minimisin the mainof the proess

Fatiguewear(pitting

)

ear transmitters timin belt transmitters

planetary transmitters aran transmitters frition transmitters

(lbriate) belt transmitters (belt) at belt transmitters

(at belt)

ylial loas in pro-lone perio of exploi-

tationoverloa an stressonentration

inlsions in material insufcient lubrication improper nal technolo-

y proess (tehnoloyheritae)

improper parameters ofhemial-thermial treat-ment (tehnoloy heritae)

retion of ontat stressesan freqenies of yli loa

retion of loa sin of material with improveresistane to wear e to fatie

sin of lbriant with hihervisosity an with ep aitives

sin of optimal parameters oftehnoloial proessin

sin of optimal parameters ofhemial-thermial treatment

Abrasivewear

all mehanialtransmitters

abrasive-aressiveenvironment

overloa insufcient hardness

of ontat srfaes

removal of polltants sores improve sealin (se of seal-

ants) retion of loa erease of harness of ontat

srfaes erease of thiness of lbri-

ant layer

corrosionwea

r

ear transmitters hain transmitters timin belt transmitters

(plley) planetary transmitters aran transmitters frition transmitters belt transmitters

(plley) at belt transmitters

(plley)

aressive environmentmoistre insufcient lubrication

improve sealin sin of lbriant with orro-

sion inhibitors sin of material with resist-

ane to orrosion.

Soring

ear transmitters planetary transmitters

aran transmitters frition transmitters

(lbriate)

overloabonary lbriation

inproper lbriation insufcient lubricationabsene of brea-in

perio

retion of loa, spee antemperatre

se of ompatible materials inrease of lbriant qantity oolin of lbriant sin of lbriant with hiher

visosity sin of hih pressre aitives sin of triboloy oatins

Frettingorrosion

hain transmitters(hain)

aran transmitters(telesope)

vibrations insufcient strength

of assembliesaressive environment

elimination or absorption ofvibrations

sin of absorbin materials inrease strenth of assembly protet ontat srfaes from

orrosion-fatie proesses improve sealin sin of lbriant with orro-

sion inhibitors


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with ontat of sie srfaes an with speial interferene of timin belt teeth

that interferes to sie srfae of the timin belt plley teeth. de to elastiity of

the belt an riiity of plley, the initial ontat is followe by the eformation of

the timin belt teeth. The rotation of the plley moves the ontat srfae from

the top of the plley teeth to its basis an it is followe by relative sliin of sie

srfaes of the plley an teeth, rin the enterin phase of ontat, means sli-in frition. Frther movements of the belt alon the irmferential anle are

characterised by exion of timing belt teeth, small sliding speeds of side surfaces

of teeth, but, also, with moving of the rst layer in the contact of the top surface

of the plley teeth an interspaes of teeth of timin belt. The intensity of frition

is very small in this perio till the en of ontat. The harateristi of the tim-

in belt an timin belt plley with sie rins is to ompress an to psh the air

at hih spees rin the enterin phase of ontat an by that alter the eneral

harateristi of frition of timin belt transmitters.The presene of axial fores, ase by onstrtion of the belt an by heli-

oially threa of plin element, proes rnnin of the timin belt on the sie

rin of the plley. Relative motions of fae srfae of belt an sie rin of the

pulley are the causes of sliding friction that is signicantly high at the beginning

of the ontat an at the en of ontat.

The wear types at mehanial transmitters that are ommon in exploitation

are presente at Table 3. By hoosin the exetors of elementary fntions, in

the oneptal proere of esin proess, the esiner also taes obliation tominimise the wear proesses, frther throh esin, that are navoiable in ex-

ploitation. Lare nmber of possibilities ollete in systemati information an

be se, bt also own reative experiene an be se.

cONcLuSIONS

The analysis of the tribomehanial systems for power transmission by form on-

nection implicates that realisation of the main function is inuenced by all com-ponents of the system strtre (elements, properties, interations). The iffer-

enes in eometrial shape of triboelements, omplex an ifferent inematial

motions, presents of lbriants an other fators ase ifferent mehanisms of

friction generation. Every type of transmitter has own specic functioning, but,

also, own characteristics of friction processes. This is specic for the tribome-

hanial systems with omplex strtre that onsist of several tribomehanial

systems an in whih realisation of fntion is relate to resltant in motions, an

the resistane to those motions is far more omplex.The wear is natral, proressive proess of material lost from the ontat

srfaes that an not be avoie an that follows every tribomehanial system

at power transmission in exploitation. The inuence of factors and their complex


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interations proe ifferent types of wear proesses at ontat srfaes of tri-

bomehanial systems. Those proesses are ifferent e to its ases, intensity

and due to signicances to inuence the duration of exploitation period of realised

onstrtions. Wear an not be ompletely eliminate, bt it an be minimise to

aeptable levels.

AckNOWLEdgEMENT

This paper presents the researh reslts obtaine within the framewor of a proj-

ect TR35021, nancially supported by the Ministry of Education and Science of

the Repbli of Serbia.

REFERENcES

1. S. TANASIJEVIc: Triboloially corret desin. Falty of Mehanial Enineerin of kra-

jeva, krajeva, 2004 (in Serbian).

2. g. W. STAcHOWIAk, A. W. BATcHELOR: Enineerin Triboloy. Elsevier Btter-

worth-Heinemann, Oxfor, 2006.

3. T. A. STOLARSkI: Triboloy in Mahine desin. Elsevier Btterworth-Heinemann, Oxfor,

1999.

4. H. cZIcHOS: Triboloy A Systems Approah to the Siene an Tehnoloy of Frition,

Lbriation an Wear. Elsevier, Amsteram, 1978.

5. A. RAc: Lbriants an Mahine Lbriations. Falty of Mehanial Enineerin, Bel-rae, 2007 (in Serbian).

6. B. SHARMA, O. P. gANdHI: diraph-base Reliability Assessment of a Tribo-pair. Ins-

trialLbriation an Triboloy, 60 (3), 153(2008).

7. R. SEHGAL, O. P. GANDHI, S. ANGRA: Failure Cause Identication of Tribomechanical

Systems usin Falt Tree-A diraph Approah. Triboloy International, 36 (12), 889 (2003).

8. R. k. gARg, V. k. guPTA, V. P. AgRAWAL: Reliability Moellin an Analysis of a Tribo-

mehanial System. International J. of Moellin an Simlation, 27 (3), 288 (2007).

9. S. MITROVIC: Denition of Completely Worn out Elements of Tribomechanical System on

Extrers. Triboloy in instry, 23 (3&4), 39 (2002).10. J. gLISOVIc, R. RAdONJIc, d. MILORAdOVIc: Experimental Metho for Analyzin

Frition Phenomenon Relate to drm Brae Sqeal. Triboloy in Instry, 32 (4), 28 (2010).

11. S. TANASIJEVIc, B. STOJANOVIc, N. MILORAdOVIc: Eo-triboloial corret desin:

New demans of contemporary desin. J Bal Tribol Asso, 16 (4), 608 (2010).

12. N. MARJANOVIc, B. IVkOVIc, M. BLAgOJEVIc, B.STOJANOVIc: Experimental deter-

mination of Frition coefcient at gear drives. J Bal Tribol Asso, 16 (4), 517 (2010).

13. N. MARJANOVIc, B. IVkOVIc, M. BLAgOJEVIc, B. STOJANOVIc: Experimental de-

termination of Frition coefcient at gear drives. J Bal Tribol Asso, 16 (4), 517 (2010).

14. L. IVANOVIc, d. JOSIFOVIc, A. ILIc, B. STOJANOVIc: Triboloial Aspet of the kin-

ematial Analysis at Trohoial gearin in contat. J Bal Tribol Asso, 17 (1), 37 (2011).

15. J. kLEEMOLA, A. LEHTOVAARA: Experimental Simlation of gear contat Alon the

Line of Ation. Triboloy International, 42 (10),1 453 (2009).


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506

16. J. kLEEMOLA, A. LEHTOVAARA: Experimental Evalation of Frition between contat-

in diss for Simlation of gear contat. Tribotest, 13 (1), 13 (2007).

17. R. MARTINS, R. AMARO, J. SEABRA: Inuence ofLow Frition coatins on the Scufng

Loa capaity an Efciency ofgears. Triboloy International, 41 (4), 234 (2008).

18. B. STOJANOVIc, S. TANASIJEVIc, N. MARJANOVIc, L. IVANOVIc, M. BLAgOJE-

VIc: Wear as the criterion of Mehanial Transmitters Worin Life. J Bal Tribol Asso,

17 (2), 215 (2011).19. B. STOJANOVIc, S. TANASIJEVIc, N. MILORAdOVIc: Tribomehanial Systems in

Timin Belt drives. J Bal Tribol Asso, 15 (4), 465 (2009).

20. B. STOJANOVIc, N. MILORAdOVIc, M. BLAgOJEVIc: Analysis of Triboloial Pro-

esses at Timin Belts Tooth Flan. Triboloy in instry, 31 (3&4), 53 (2009).

21. B. STOJANOVIc, L. IVANOVIc, M. BLAgOJEVIc: Frition an Wear in Timin Belt

drives. Triboloy in instry, 32 (4), 33 (2010).

Received 22 May 2012

Revised 21 July 2012

Documents

Tribomechanical Systems in Mechanical Power Transmitters