DESIGN, PRODUCTION, AND APPLICATION OF A STAND FOR TESTING FRICTION OF THE BEARINGS

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Tome V (year 7), Fascicole, (ISSN 1584 665) DESIGN, PRODUCTION, AND APPLICATION OF A STAND FOR TESTING FRICTION OF THE BEARINGS Pavlia KATSAROVA, Stilia NIKOLOV, Miltso TASHEV TECHNICAL UNIVERSITY

of the dyig oscillatios. The stad gives possibilities to carry out frictio tests of slidig ad atifrictio bearigs.

The received results were show i tables ad graphs that prove the work capacity of the created stad.

1 Tome V (year 7), Fascicole, (ISSN ) DESIGN, PRODUCTION, AND APPLICATION OF A STAND FOR TESTING FRICTION OF THE BEARINGS Pavlia KATSAROVA, Stilia NIKOLOV, Miltso TASHEV TECHNICAL UNIVERSITY SOFIA,BRANCH OF PLOVDIV, JOHN ATANASSOV TECHNICAL COLLEGE, PLOVDIV, BULGARIA ABSTRACT: A pedulum-stad was desiged ad produced for the purpose of testig the frictio of the bearigs applyig the method of the dyig oscillatios. The stad gives possibilities to carry out frictio tests of slidig ad atifrictio bearigs. Experimets with two slidig bearig pairs (steel/lamiated fabric ad steel/steel) were carried out o the suggested methodic. The received results were show i tables ad graphs that prove the work capacity of the created stad. The so suggested stad ca be used for experimetal frictio studies of wide rage of slidig ad atifrictio bearigs. KEY WORDS: bearigs, slidig bearig, frictio pair, kiematical aalysis 1. INTRODUCTION The bearigs are devices that support the rotatig or oscillatig machie elemets i defiite positio, carry their load ad trasfer it to the stad permittig costraied relative motio at the same time [1,4]. The purpose of this work is to study the frictio of the bearigs usig the method of the dyig oscillatios. A stad was desiged ad produced i order to determie the frictio torque i differet bearigs by a pedulum with dyig oscillatios. The pedulum axis is suspeded o the bearig ad allowed to oscillate freely. The frictio of the bearig leads to a process of dyig oscillatios. A gradual amplitude decrease (decrease of the pedulum agle of deviatio) is characteristic for the process of the dyig oscillatios [1,3] fig.1. The potetial eergy of the pedulum which is coected with the amplitude chages durig the motio: Δ П=Gh=Gh(cosα - cosα ) (1) where: П is the potetial eergy of the pedulum; G the weight of the pedulum; h the legth of the pedulum. 41

2 ANNALS OF THE FACULTY OF ENGINEERING HUNEDOARA JOURNAL OF ENGINEERING. TOME V (7). Fascicole α Whe the deviatio agles are small (α < 8-1 ), cosα ca be replaced by 1- ad the depedece (1) acquire the followig form: ( α )( ) α α α Δ П= Gl = Gl( α α ) α ср () The work of the frictio forces of the cosidered time iterval of the pedulum from α to α ca be received by multiplyig the frictio torque Мтр by the sum of the pedulum agles of oscillatio: α + α + α + α +... α + α (3) Атр = Mтр ( ) 1 3 Takig ito cosideratio that: α + α = α ср и α1 + α + α α 1 = ( 1)α ср (4) We receive for the work of the frictio: Атр= Мтр α ср (5) The pedulum potetial eergy chage is equal to the work of the frictio forces because the frictio i the bearig is the oly eergy cosumer. After equalizatio of Δ П from () to the Атр from (3) we receive the followig depedece: α α MТР = Gl (6) or α α MТР = Gl 4N (7), where: MТР frictio torque [N m]; G weight of the pedulum [N]; l legth of the pedulum [m]; h differece of the pedulum height at iitial ad fial positio. [m]; α α agles of oscillatio of the pedulum [rad]; umber of the semi-periods [бр.]; N - umber of the oscillatio periods of the pedulum - N = [бр.]. The coectio betwee the frictio torque ad the value of the reduced frictio coefficiet is: = Ffr.. (8), where: F loadig force [N]; f - frictio coefficiet ; r bearig s radius [m]. MТР O 1 l α α -1 α α 3 α α 1 h G Fig.1. Theoretical treatmet 4

ANNALS OF THE FACULTY OF ENGINEERING HUNEDOARA JOURNAL OF ENGINEERING. TOME V (7). Fascicole. PRINCIPLES OF OPERATION OF THE STAND The stad cosists of the followig elemets Fig.

The weight positio toward the axes of rotatio ca be chaged by the cotrollig ut up to 1[mm]. The tested bearig bush (5) is fasteed i the upper part of the pedulum by a threaded joit (М8).

3 ANNALS OF THE FACULTY OF ENGINEERING HUNEDOARA JOURNAL OF ENGINEERING. TOME V (7). Fascicole. PRINCIPLES OF OPERATION OF THE STAND The stad cosists of the followig elemets Fig.: base (1) made of lamiated fabric with possibilities of immovable fixatio to a wall. Pedulum which cosists of: axis (), weight (3) ad cotrollig ut (4) all made of steel. The weight positio toward the axes of rotatio ca be chaged by the cotrollig ut up to 1[mm]. The tested bearig bush (5) is fasteed i the upper part of the pedulum by a threaded joit (М8). The shaft (6) with the bearig bush is mouted to the base by a threaded joit М18. The bearig bush is mouted o the bearig joural with clearace fit H7/h6. The bolt ad the ut М8 (7, 8) are used for axial fixatio of the bearig. The parameters of the stad area: Overall dimesios- 67,5/4/6 [mm] Mass of the weight (3, fig.) of the pedulum -,5 1 [kg]. Legth of the pedulum l -,8,38 [m]; Diameter of the tested frictio surfaces D (fig.3) [mm]. Fig. Desig of the pedulum stad The stad gives possibilities of testig slidig bearigs with differet materials takig part i the frictio pairs of the tested bearig bushes ad shafts accordig to fig.3. The diameter D of the bearig s frictio pairs determies the overall dimesios of the bush ad shaft. Fig.3 Desig of the bearig bushes ad shafts of the slidig bearigs. 1-shaft with a bearig joural; - bearig bush 43

ANNALS OF THE FACULTY OF ENGINEERING HUNEDOARA JOURNAL OF ENGINEERING. TOME V (7). Fascicole The tested bearig has to be positioed o the stad accordig to fig.4.

3 Desig of the bearig bushes ad shafts of the atifrictio bearigs. 1-shaft with a bearig joural; -bearig bush; 3- tested atifrictio bearig 3. METHODIC USED FOR THE EXPERIMENT 1.

4 ANNALS OF THE FACULTY OF ENGINEERING HUNEDOARA JOURNAL OF ENGINEERING. TOME V (7). Fascicole The tested bearig has to be positioed o the stad accordig to fig.4. The diameters D ad d of the bearig bush ad shaft deped o the dimesios of the tested bearig ad determie the overall dimesios of the bush ad the shaft accordig to fig. 3. Fig.3 Desig of the bearig bushes ad shafts of the atifrictio bearigs. 1-shaft with a bearig joural; -bearig bush; 3- tested atifrictio bearig 3. METHODIC USED FOR THE EXPERIMENT 1. Preparatio of the stad for the experimet. The preparatio is made accordig to the diagram fig.5. Fig.5 Diagram of the stad preparatio 1- shaft fasteig to the base; - bush fasteig to the pedulum axis; 3-fittig of the frictio pair; 4- axial fixatio of the frictio pair; 5-cotrol of the pedulum legth. Determiig the stad characteristic. The characteristic of the stad Gl is determied by measurig the mass ad the legth of the pedulum. 3. Carryig out the experimet. The pedulum is deviated to the ecessary agle α ad tha the fial agle α ad the umber of the periods N are give for which this agle is reached. The separate tests of the experimet are repeated several times ad the received results for α are averaged. 4. Calculatio of the frictio torque MТР. The calculatio is made accordig to (7) usig the received results. 5. Determiatio of the reduced frictio coefficiet f. It is carried out accordig to formula (8), takig ito cosideratio the radius of the tested frictio pair. 6. Aalysis of the received results. 44

5 ANNALS OF THE FACULTY OF ENGINEERING HUNEDOARA JOURNAL OF ENGINEERING. TOME V (7). Fascicole 4. RESULTS Two slidig bearigs with frictio pairs cosistig of steel/lamiated fabric ad steel/steel were studied of fictio by the suggested stad accordig to the above described methodic. The characteristics of the stad were determied after preparig it for work ad producig the bearigs: Radius of the tested bearig r -, 85 [m]. Weight of the pedulum G - 1 [N]; Legth of the pedulum l,38 [m]; The experimet was carried out at three iitial agles for each pair: α -1 =,175[rad]; =,349[rad]; 3 =,54[rad]. Some of the received results ad the calculated o this basis values are give i Tabl.1. The values of α are determied as mea value of five cosecutive tests results at costat agle α. The value of MТР is also determied as mea value. Table 1 Type of the frictio Calculated values accordig to Experimetally determied data pair i the tested formulae () ad (3) bearig α α N [бр.] МТРi [N] МТР [N] f 1 4,33 1 Steel/steel 8 6,33,33,39 3 9,5 1, , Steel/lamiated 1 8,1 fabric ,3,1,5 The experimetally determied frictio coefficiets i the two frictio pairs correspod to the data published i [] for the frictio coefficiets of such type of pairs. They are as follows: Steel/lamiated fabric - f=,15,5. Steel/steel - f=,39,41; The received results ad their graphical presetatio are show as follows: fig.6 for a frictio pair steel/ lamiated fabric ad fig.7 for a frictio pair steel/ steel. The graphs describe the pedulum movemet. The values of the pedulum oscillatio agles α i are determied as mea value of five cosecutive tests results at costat agle α. Fig.6. Results from the experimet with a frictio pair steel/lamiate fabric 45

ANNALS OF THE FACULTY OF ENGINEERING HUNEDOARA JOURNAL OF ENGINEERING. TOME V (7). Fascicole Fig.7. Results from the experimet with a frictio pair steel/steel 5.

6 ANNALS OF THE FACULTY OF ENGINEERING HUNEDOARA JOURNAL OF ENGINEERING. TOME V (7). Fascicole Fig.7. Results from the experimet with a frictio pair steel/steel 5. CONCLUSIONS The results received by the experimet correspod to the data published i differet literature sources. The so suggested stad ca be used for experimetal frictio studies of wide rage of slidig ad atifrictio bearigs. The pedulum-stad gives possibilities of studyig differet frictio pairs at defiite workig coditios. The suggested experimetal methodic is accessible for the laboratory REFERENCES [1.] Nedev,Tc.,Jivkov,P., Lilov Al.,Guidace for laboratory exercises o elemets of apparatus ad machies, Techika, Sofia, ISBN 61.81(76),1978,p.p.3-7 [.] Hristov D.,Calculatio ad costructig of machies elemets,techika,isbn (83), Sofia, 198 [3.] Nedev,Tc,Elemets of the apparatus ad machies, Techika, Sofia, ISBN 61.1(75.8), 1979,p.p [4.] Nedev Tz., Galabov V., Lilov Mechaics Softrаdе 46

Damped Vibration of a Non-prismatic Beam with a Rotational Spring

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