TESTING RIG FOR STUDYING THE BEHAVIOUR OF SPHERICAL JOINTS AND SPHERICAL BEARINGS USED IN MINING INDUSTRY

003 ISSN 11-4590 161 TESTING RIG FOR STUDYING THE BEHAVIOUR OF SPHERICAL JOINTS AND SPHERICAL BEARINGS USED IN MINING INDUSTRY Fncisc Tkcs 1, Vsile Zmfi 1, Soinel Hohotă 1 Univesity of Petoşni, S.C. Gospodăie Pestcom S.A. Petoşni, Români vzmfi@upet.o ABSTRACT Tibologicl conditions existing in spheicl beings nd spheicl joints e vey complex. By this eson the ssessment of the unning time o dubility of these beings o joints espectively the ssessment of the effects of some modifiction in the field of used mteils o sufce tetments cn be elized only by expeimentl methods. In the ppe the testing methods by sttic nd dynmic lods e pesented, espectively the methods nd testing igs genelly used. KEYWORDS: spheicl beings, spheicl joints, testing methods. 3. GENERALITIES The spheicl joints e used in the cse the mchine pts which e connected must pefom oscillting movements in diffeent plnes, inside the limits of given ngle. The spheicl beings consist on n intenl ing with the extenl woking fce convex nd n extenl ing with intenl woking fce spheicl nd concve. Due to thei constuction they e dequte in the situtions when the self djusting being of the shfts eltive to the fme o in cse when the being must pefom oscillting sptil movements with educed speeds. Due to mchining o ssembling eos, o the defomtion of the entie ensemble s defomtion duing the functioning, n inclintion of the shft end elted to the being ppes. As esult, in the conventionl constuctions the contct pessue t the spindle will incese poducing heting, we nd gipping of the being. Due to the spheicl shpe of the sliding sufces, incse of sliding spheicl beings, the lod will be unifomly distibuted on the woking sufce, nd due to the self djusting cpcity, the bove mentioned negtive effects will be voided. The extension of spheicl sliding beings is connected to the development of hydo-pneumtic ctutos. In cse of cylindicl joints, due to the noncolineity, o non-pependiculity, the whole hydulic o pneumtic cylinde will be submitted to flexion stesses. Using spheicl sliding beings, the flexionl chge will be lmost completely eliminted. The flexionl toque in the cylinde s ig will be limited to the fiction fom the spheicl being. Evidently, the beings with spheicl sliding sufces e moe expensive thn the cylindicl jcks, but the supplementy expenses elted to the totl cost of the cylindes e eltively low, so the incese of elibility nd sfety of the cylindes e el dvntges. In pctice, mny situtions ppe when the spheicl beings e submitted to dil-xil lods o even puely xil ones. In ode to ensue the optiml behvio of the sliding spheicl beings in such situtions dil-xil nd xil spheicl sliding beings wee developed.. TYPES OF SLIDING SPHERICAL BEARINGS AND ROD ENDS WITH SPHERICAL BEARINGS Due to vey vious woking conditions diffeent kind of sliding spheicl beings wee developed, with diffeent dimensions nd mteil couples. Tking ccount the lods which cn be suppoted, these beings e divided into thee goups: 1. dil spheicl sliding beings;. dil-xil spheicl sliding beings; 3. xil spheicl sliding beings. The dil spheicl sliding beings (fig. 1 nd fig. ) e ppopite specilly fo suppoting high dil lods nd smll xil lods. Fig. 1 Rdil spheicl sliding being Fig. Lge dimension spheicl sliding being

16 THE ANNALS OF UNIVERSITY DUNĂREA DE JOS OF GALAŢI 003 ISSN 11-4590 The dil-xil spheicl sliding beings (fig. 3) e ppopite fo suppoting mixed, dil-xil lods. This kind of being cn be dismntled, so the mounting of the intenl ing cn be pefomed independently fom the extenl one. The xil spheicl sliding beings (fig. 4) e devoted fo the suppot of high xil lods. They llow, in cetin limit, suppoting mixed lods, only if the xil lod is t lest the double of the dil one. Regding the couple of mteils used in thei constuction, the spheicl sliding beings e clssified in: - steel on steel sliding spheicl beings; - sliding spheicl beings which do not need mintennce. The steel on steel sliding spheicl beings e mde on high qulity being steel. In this cse the extenl ings nd the intenl ones e tempeed, the sliding sufces e polished nd submitted to mngno-phosphting tetment, fte tht e teted wit molybdenum disulphide. This supeficil tetment ensues high esistnce to we nd optiml opeting chcteistics in cse of limit nd mix fictionl woking conditions. tempeed nd polished sufce of the intenl ing (fig. ). The od ends with spheicl sliding beings e elized fom sliding spheicl beings mounted in fmes which e ttched to the od of the espective pneumtic o hydulic cylindes. As function of the possibilities of mounting of the od ends t the end of the cylinde s ods, they e with extenl coil, with intenl coil nd welded od ends (fig. 5). Fig. 5 Rod end with spheicl sliding being with intenl coil 3. CALCULATION OF SLIDING SPHERICAL JOINTS AND BEARINGS Fig. 3 Rdil-xil spheicl sliding being Fig. 4 xil spheicl sliding being The spheicl sliding beings which do not need mintennce e used minly in the fields whee the equiements egding the elibility nd sfety e vey sevee, espectively whee the poblems of lubiction difficulties mke the use of steel on steel beings itionl. These cses e minly, hevy sttic o dynmic lods nd smll velocity eltive movement. The couples of mteils used to the poduction of these beings e: steel on compound mteil, DU; steel on plstic moed with glss fibe +PTFE; steel on tissue with PTFE; steel on sheet on PTFE; steel on specil bonze. Fo the constuction of hevy mchines, t which the loding cpcities nd the dimensions of odiny xil spheicl sliding beings e not sufficient, dil spheicl lge size beings e used. The mteil couple on which the sliding is pefomed t these beings e pesented in the shpe of mny ound plstic tblets contining PTFE nd moed with glss fibes, intoduced into steel cge welded to the extenl ing, sliding on the spheicl When we design the spheicl beings (fig. 6) the necessy D dimete of the joints e deived fom considetions egding the contct pessue, using the eltion (1) D F F + A A = (1) π ϕ p whee: F dil lod cting on the joint, F xil lod cting on the joint, A = 4 A / π D, A -= 4 A / π D, ϕ - the tio between the effective nd the nominl e, p mximum contct pessue. Fig. 6 Spheicl joint loding scheme.

003 ISSN 11-4590 163 Then the stess in the dngeous section of the spindle, using the eltion: 4 F 3 F σ mx = + σ 3 () π d0 π d0 whee d 0 is the dimete of the spindle in the dngeous section, - the dil foce s m. The clculus of veifying of the spheicl joints is pefomed t contct pessue. In this espect we use the following eltion: p m F F 4 + A A = p (3) π ϕ D The clcultion of dil-xil spheicl beings (fig. 7), ccoding to the domestic litetue is pefomed t sttic nd dynmicl lods. Fig. 7 Loding scheme of the spheicl sliding being. Fo the clcultion t dynmic lod the equivlent contct pessue p e is deived using the eltion (4), in which B is width of the extenl ing of the spheicl being, D - nominl dimete of spheicl sufces. F + 6 F pe = (4) F B D Knowing the equivlent contct pessue we cn clculte the dubility expessed in numbe of oscilltions: 3 p0 5 0 f0 10 p e L = (5) whee f 0 is coection fctos tking ccount the elubiction of the being, p 0 dynmic dmissible contct pessue fo L 0 = 10 5 oscilltions. Fo the sttic clcultion we veify if it is fulfilled the condition: pe p s (6) whee p s is dmissible sttic contct pessue. By the clcultion of the spheicl beings, ccoding to the compnies poduct ctlogues it mens the detemintion of the necessy size of the beings, bsed on the lods which must be suppoted nd the needs of dubility. When we pefom clcultion we tke into ccount if they must pefom oscillting movements unde lod continuously o only to compenste the mchining nd ssembly position eos. In the fist cse the clculus fo dynmic loding is pefomed, in the second one, t sttic lods. Equtions fo the clcultion of dubility of sliding spheicl beings wee estblished on the bsis of endunce tests. Fo the constucto, these equtions epesent vluble help t the ight dimensioning of the beings. It is obvious tht between the sliding sufces tht e woking in high lod conditions, in the domin of mix nd even dy fiction, the tibologicl conditions e vey complex. These, togethe with the impotnt numbe of woking fctos, which cn be putted difficulty in mthemticl equtions, led to the fct tht these dubility clcultions be ccepted only s n djuvnt element in the dimensioning nd not s eltions giving the el woking dution of the beings. So, using the given eltions we cn deive only efeence vlues fo the dubility of spheicl beings. Mny beings will ech the vlue of dubility given by these equtions, nd n impotnt enough mount of beings will be ove the clculted dubility. The clculus of the spheicl dubility beings dynmiclly loded is bsed on the dynmic loding cpcity C. It give us the llowed lod of the being, when the lod is in single sense in conditions of noml tempetue nd sliding speed, which llows to ech nominl dution of wok of 100,000 oscilltions in conditions of non-mintennce opetion. When the spheicl being is stticlly loded o pefoms insignificnt movements unde lod, the sttic loding cpcity C 0 is tken into ccount. It is lso t the bsis of the clcultion of the spheicl beings dynmiclly loded, when on them e cting sevee shocks. The sttic loding cpcity give us the llowble lod which cn be suppoted by spheicl being, without being dmged, espectively, without pemnent defomtions on the sliding sufces which poduces functionl distubnces. The dubility of sliding spheicl being is given by the numbe of oscilltions which cn be pefomed, without the we of the sliding sufces, without the incese of dil clence in the being nd without the incese of fiction coefficient in the being. The detemintion of the nominl dubility stts fom the dynmic loding cpcity. The vlue of the loding cpcity is vluble only if the lod hs constnt vlue nd diection, espectively if the dil nd dil xil beings e submitted to puely dil o puely xil lods, cting though the cente. The nominl dubility of spheicl sliding beings is clculted using the fomul:

164 THE ANNALS OF UNIVERSITY DUNĂREA DE JOS OF GALAŢI 003 ISSN 11-4590 3 C 5 L = 1 ( 3 ) 10 (7) P whee C is dynmic loding cpcity, P equivlent lod, 1 the coefficient of the diection of cting of the lod, hving vlues 1 = 0.015 5, s function of the kind of lod nd kind of mteil pi, coefficient of mintennce hving vlues =1 o =15, s function of the existence o non existence of lubiction nd the kind of mteil pi, 3 - coefficient of tempetue of the being hving vlues 3 =0.3 1, s function of the woking tempetue nd the ntue of the mteil pi. If the lod in being is not confoming to the conditions of defining the loding cpcity, the equivlent dynmic lod is deived. In pctice in mny cses the dil, dil xil nd xil spheicl sliding beings e submitted to combined lods, which cn be decomposed in dil nd xil components. In these situtions the equivlent dynmic lod is clculted using the eltion: P = X F + Y F (8) whee: X the coefficient of dil lod (fo dil beings X=1, fo dil xil ones X=1 if F /F 0.8 nd X = 0.6 if F / F >0.8, fo xil ones X=1.); - Y the coefficient of xil lod (fo dil beings Y=1 6 s function of the tio F /F =0. 1.6 nd the ntue of the mteil pi, fo the dil xil beings Y=0 if F /F 0.8 nd Y=0.7 if F /F >0.8, fo xil ones Y=1); - F the dil lod cting on the being; - F - the xil lod cting on the being. In the cse of spheicl sliding beings, which e submitted to lods in stte of stnd by of which pefom only positioning movements, the llowble lod is limited not due to the ppition of weing, but the mechnicl esistnce of the ings nd the plstic defomtion of the contct sufce. The esultnt lods cting on the beings, composed fom the dil nd xil components, e tnsfomed in this cse in equivlent sttic lod. By equivlent sttic lod, we men, in the cse of dil nd dil xil beings, tht dil o xil lod, which poduces in the being the sme emining defomtion s the el lod. The equivlent sttic lod is given by the eltion: P0 = X F + Y F (9) The coefficients of the dil lod X nd the coefficients of the xil lod Y fom the eltion (9) hve the sme vlues s in eltion (8). The necessy sttic loding cpcity C 0 is deived s function of the sttic equivlent lod nd of the woking tempetue of the being using the eltion: P0 C 0 = (10) 3 The tempetue coefficient of the being 3 hs the sme vlue s in eltion (7). The eltive llowble sliding speed fo the spheicl being is function of the lod cting on the being, the mteil pi in which the being is mde on, the possibilities of lubiction nd chilling. Fom these considetions, fte selecting the being, the vlue of the poduct (p.v) must be veified by comping it with the llowble vlues (p.v) dm which depends on the pi of mteils used. The vege sliding speed of the being is detemined using the eltion: 4 vm = 5.8 10 D β f (11) whee:β - oscilltion ngle, f the fequency of the being s oscilltion. The contct pessue between the spheicl sufces is clculted with the expession: P p = (1) D B Knowing the vege sliding speed v m nd the contct pessue between the contct sufces, p, we cn veify the heting of the spheicl being: ( p v ) ( p v ) dm (13) The vlues (p v) dm e pesented in tble 1. These vlues e vluble in the cse of constnt lod nd continuous functioning. In cse of intemittent functioning s function of the dution of puses nd the theml conductivity of the being nd the fme, the het developed in the being cn be bette nd fo this eson we cn llow fo shot peiods moe lge vlues of (p v) dm. Tble 1. Vlues of (p v) dm Mteil pi (p v) dm [N/mm.mm/s] Steel on steel 400 Steel on PTFE sheet 600 Steel on compound mteil DU 400 Steel on plstic moed with glss fibe + PTFE 400 Steel on specil bonze 1000 Steel on tissue with PTFE 800 4. STATES OF FRICTION AND LUBRICATION IN SPHERICAL SLIDING JOINTS AND BEARINGS Confom to the clssifictions fom the tibology we cn meet dy fiction, mixt fiction, limit fiction nd fluid fiction. The mix fiction epesents the stte of fiction, which is mnifested in mny cses of use of spheicl sliding beings. This sttement cn be suppoted by the following guments: - due to the oscillting movement the speed of the eltive sliding movement e pssing though zeo. A film of lubicnt eventully fomed duing the movement will be pemnently destoyed t this moment;

003 ISSN 11-4590 165 - in mny cses t the spheicl beings, the contct pessue vlue is so high tht the lubicnt is pushed out fom the contct sufce; - due to the high vlues of the contct pessue, the film of lubicnt cn exist only in thin lye; - fom constuctive esons, the quntity of lubicnt, which exists inside the being, is vey estined. In the cse of spheicl sliding beings, loclly cn be instlled the limit stte of fiction, little befoe the gipping, which mens tht the eseve of lubicnt dsobed on he sufce of fiction wee consumed. If e-lubiction is not pefomed, the dution of opetion of the beings consumed. 5. TESTING THE SPHERICAL SLIDING JOINTS AND BEARINGS 5.1. Sttic testing of the spheicl sliding joints nd being Allowble lods fo the sttic loding of spheicl sliding beings e detemined fo contct pessue of 500 N/mm. The llowble sttic lod of spheicl sliding being must be in ny cse less thn the lod, which cn poduce filue in ny component of the being, (e.g. fissue in the extenl o intenl ing). If this so clled filue lod is known, the sttic lding cpcity of the being cn be detemined, using cetin fcto of sfety. In ode to veify the sttic llowble lod of the being, beking test cn be pefomed using the testing device pesented in the figue 8. Fig. 8 Device fo sttic testing of sliding spheicl beings. The testing is pefomed stticlly, wit pogessively incesing lod, with hydulic pess with lod nge until 100kN. It ws poved tht t the coect mounting of the beings the bolt is the wek pt. So, we cnnot ech the limit beking lod of the beings becuse of insufficient esistnce of the bolts. By this, it is poved tht, confoml with the ctul noms egding the sttic loding cpcity of spheicl sliding beings, lge enough sfety fctos ws tken into ccount. 5.. Dynmic testing of the spheicl joints nd being The vlues of the dynmic llowble lod (of the dynmic loding cpcity) e coesponding to contct pessue in the being of bout p = 50 N/mm nd e vluble fo 5,000 epeted loding cycles. Apt fom the mnufctue s pesciptions, the litetue is poo in infomtion egding the dynmic loding cpcity of the spheicl beings. By this eson it is necessy to pefom theoeticl nd expeimentl eseches in this field. The im to elize test ig which simultes the el like conditions fom pctice, which ensues comfotble test deployment nd intepettion of the esults, which e useful fo pctice leded to the conception of n oscillting testing ig. This kind of ig is used lso by the mnufctuing compnies fo testing thei poducts. In ode to pefom the dynmic tests, it is necessy to elize ig, which llows the pefomnce of oscillting movements unde lod. This testing ig (Fig. 9) consists on two sleepes in pllelogm mounting, elized with knife type suppots. The knives nd the coesponding pts e on tempeed steel. The being to be tested is mounted in the supeio sleepe nd cn be loded using smll hydulic cylinde. The infeio sleepe is fixed on the body of the ig. The tnsfe of the lod towds the tested being is elized by the tensioning of sleepes; in this scope the pllelogm system is used. The sleepes e fixed on the bse of the ig by coiled ods. The loding used to lod the tested beings, is in the nge 15 4.000dN. The oscillting movements of the pllelogm system e obtined using n eccentic mechnism, which moves the supeio slippe. The eccentic mechnism is ctuted though belt tnsmission by n electic moto with djustble speed. By djusting the speed of the electic moto we obtin the modifiction of the oscillting fequency of the mechnism. Modifying the length of the piston ods the ngle of oscilltion cn be djusted. The ig llows the obtining of ngles of oscilltion in the nge 7 0 30' 1 0 10'. The fequency of oscilltions cn tke the vlues 10, 0, 100, 300, 600, 900, nd 1000 oscilltions / min. In ode to pefom the dubility tests nd ssess the behvio in diffeent woking conditions, it becme necessy to build ou own testing ig. At the constuction of this ig we consideed the expeience of SKF Compny the most impotnt mnufctue of sliding spheicl beings, nd the ecent evolution in the constuction of such beings.

166 THE ANNALS OF UNIVERSITY DUNĂREA DE JOS OF GALAŢI 003 ISSN 11-4590 The ctuting system of the conceived ig is fomed on following elements: - synchonous electic moto wit powe P=4kW nd ottion speed n = 960pm; - educing gebox in two stges: the fis one with helicl ge, one beginning helix z 1 =1 nd toothed wheel z =0 teethes; the second stge cylindicl with stight teethes, z 3 =15 nd z 4 =3 teethes; - speed vito with fiction wheels with eduction tio i v =) 0.4. The mode of emplcement of the electic moto, the gebox nd the vito e shown in figue 10. The cinemtic scheme of the ctuting system is shown in figue 11. In ode to obtin lge nge of speeds t the exit of the vito, the moto nd the gebox cn be moved on the infeio fme. So, in cetin position the vito is coupled with the shft of the helicl wheel obtining the nge of 4 10 pm, nd in the second position the vito is coupled with the exit shft of the second stge of the gebox obtining the nge 11.5 56.5ot/min. The loding of the beings is intended to be elised wit system of scew-nut nd disk spings (Fig. 1). Fig. 9 The ig fo dynmic testing of the sliding spheicl beings, elised by SKF. Fig. 10 The ctuting system of the ig. Fig. 11 Kinemtic scheme of the ctuting system. Fig. 1 The ssembly of testing ig with the system of being testing.

003 ISSN 11-4590 167 In the photogph of figue 13 we cn see the ltel ight side of the ig in which cn be seen the dive nd the gebox. The photo in figue 14 shows the font view of the ig, with the gebox nd the vito. Fig. 13 View fom the ight side of the ig. Fig. 14 Font view of the ig. 6. CONCLUSION Becuse, in ou county until now the spheicl joints nd the spheicl beings whee not been studied, lcking the mple published ppes o books we conside being useful to pefom studies inn this field, minly expeimentl ones. Also, until now we hve not infomtion bout the mnufctuing in Romni spheicl sliding beings. The elizing of the espective studies supposes the testing of such spheicl joints nd beings nd the study of the behvio of such pts in lbotoy conditions on igs. The min scope to elize testing ig in which the el conditions being simulted, led to the conceiving of testing ig with oscillting loding. It is known tht this kind of igs is used by cetin compnies fo testing thei own poducts. Estblishing citeion fo the bekdown of spheicl beings is vey impotnt nd vey difficult. Becuse the diect obsevtion of the phenomen occuing in the contct zone of the two sufces is not possible, the mesuement of the flexionl toque in the tested beings is the most ppopite method which ensues contol egding the behvio of the beings duing the tests. At the tests pefomed by the foeign compnies with beings with tetment of sufces, fte dismntling the beings fte cetin vlue of the fictionl moment, they pesented diffeent sttes. A pt of the beings pesented tces of gipping in the solicited zone of the fiction sufce; othes pesented oxidtion zones, so these beings could function without specil poblems. Anothe cuse which poduces the bekdown of the beings cn be consideed thei we. It is known tht fte cetin dution of wok, the beings must be eplced becuse s esult of the we the cleing becme impotnt. In cse of mteil pis steel on steel t shot time tests the we could not be evidenced. At long dution tests the gipping ws putted in evidence, so mesuement of the cleing ws not possible In cse of these peliminy tests noisy functioning of the being ws obseved, indicting the beginning of gipping the fiction sufces. Fo the study of the behvio of the spheicl beings nd joints fte the study of the litetue, we conceived nd elized ig with which we hope to obtin esults in the solution of the following poblems: - veifiction of the sttic nd dynmic loding cpcity of the spheicl joints nd beings; - incese of the sttic nd dynmic loding cpcity nd the dubility of the joints nd beings; - testing the influence of the mnufctuing technologies nd the sufce tetments on the behvio of the spheicl joints nd beings. REFERENCES 1. DIN 648, Gelenklge, Gelenkköpfe Msspläne fü Anschlussmsse, gemny.. Dăghici I. et l., 1981, Îndum de poiecte în constucţi de mşini, Editu tehnică, Bucueşti. 3. Hohotă S., 00, Stdiul ctul l elizăilo pivind ticulţiile sfeice şi posibilităţi de utilize cesto l susţineile mecnizte, Refet de doctot N. 1, Petoşni. 4. Tkács F., 1975, Zu Entwicklung des Gelenklges, T.U. Clusthl, Gemny. 5. Zmfi V., Tkács F., Hohotă S.: 1999, Consideţii pivind ticulţiile şi lgăele cu lunece sfeice, Lucăile ştiinţifice le simpozionului intenţionl, vol., Univesitte din Petoşni. 6. Zmfi V., Tkcs F., Hohotă S., 001, Studiul comptiv l metodelo de clcul ticulţiilo şi lgăelo cu lunece sfeice, Lucăile ştiinţifice le simpozionului intenţionl,,univesiti Ropet 001, Petoşni. 7. SKF Kugellgefbiken GmbH Schweinfut, Ktlog Gelenklge und Gelenkköpfe, Duckschift N. Dd 5890.