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外文翻译--开采机械化及自动化 英文版.pdf

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外文翻译--开采机械化及自动化 英文版.pdf

MININGMECHANIZATIONANDAUTOMATIONGEOMETRYOFTHEWORKINGPARTOFANEXCAVATORTOOTHV.A.PolovinkoandA.I.FedulovUDC621.879.3Studiesofexcavatortoothwearkineticsconductedearlierbythepresentauthors1,2showedthatthemainfactorcontrollingwearplatformdynamicsisthephysicalmechanicalpropertyoftherock.Wearplatformsevolveintwostages.Toothwearacquiredduringthecriticalstage2hasnosignificantinfluenceonexcavatorperformanceintheminingandgeologicconditionstypicalforthenortheasternregionsofRussia.Cuttingelementscancontinuetobeuseduptothemaximumpermissiblewearlevelspecifiedbythemanufacturer.Inthisrespect,intensivewearduringinitialstagesapparentlyreflectssomedesignimperfectionratherthantheeffectsoftheworkadjustmentprocess.Investigatorshavestudiedthecausesandconsequencesofintensewearofexcavatorteeth,buttherearestillnobasiccriteriauponwhichtoformulategeneralprinciplessoastoimprovethewearresistanceofcuttingelementsasdeterminedbytheirdesign35.Anefficientwaytoraisethewearresistanceofanexcavatortoothistodevisethedesignparametersoftheworkingcomponentsoastoensureclassicalsinglestagewear,bypassingthecriticalpseudoadjustmentphase.Wedevelopedanewexcavatortoothdesignwhichfeaturesheightenedwearresistance.Theoutlineoftheworkingcomponentofthetoothanditsdimensionsweredevelopedwithdueregardforthemaincharacteristicpointsofthewearresistancecurvesofmassproducedwedgeshapedteeth.Toattainalinearbehaviorforthewearprocessofsuchteethwitharateequaltoorlessthanwhatisobservedduringthesecondstageofwearwithmassproducedteeth,wespecifiedthedesignparameterscorrespondingtothebeginningofthesecondphase,wherethespecificpressurefromthestandardforceofthethrustmechanismdropsto1012MPa.Figure1plotspressurevariationsonthewearplatformsofteethofbucketsusedincommonquarryexcavatorsaccordingtothefollowingexpressionP1whereUpisthewidthofthewearplatformP1istheratedforceofthethrustmechanismDandiarethelengthofthetoothcuttingedgeandthenumberofteethonthebucket,respectively.Thecurvesshowthattherearecertainpressureregionsonwearplatformswhererockresistancetoteethisequaltoorgreaterthantheforcedevelopedbythethrustmechanism.Thisloadingpatternforcuttingelementsisobservedonmonolithicstronge.g.,permafrostrocks.Ontheotherhand,somematerialsresistcuttingwithamuchweakerstrengththantheforcedevelopedbythisthrustmechanism.Toestimatethespecificpressuresformedwhencuttingelementsinteractwiththesematerials,weplottedcurves14bycomputingthepressureonthewearplatformsofantKG5Aexcavatortoothat0.8,0.4,0.2,and0.1oftheratedthrustforce.Onweakrocksthepressurevariationpatternonthewearplatformisthesame,butthepressuresanddimensionsforthewornportionofteethafterthebeginningofthesecondstagemaybemuchsmallersometimesbyaconsiderablefactor.ThisisclearlyseeninFig.1.ZoneI,crossingthecurves,definestheparametersoftheonsetofthesecondstageofwearforteethofdifferentexcavatorsandfordifferentrockstrengthscurves14.ForIKG5AexcavatorteeththestartingpointofthesecondwearstageobtainedexperimentallyliesinzoneIandcorrespondstoapressureofP1012MPaandawearplatformwidthofUtcr45mm.InstituteofMining,SiberianBranch,RussianAcademyofSciences,Novosibirsk.TranslatedfromFizikoTekhnicheskieProblemyRazrabotkiPoleznykhIskopaemykh,No.2,pp.1623,MarchApril,1993.OriginalarticlesubmittedNovember4,1992.10627391/93/29020115512.50©1993PlenumPublishingCorporation1150MPatl/.OEKG20EKG12,5EKGI5AUpUp,mmFig.1Fig.2Fig.1.Pressurevariationasafunctionofwearplatformsize14theoreticalpressurecurvesonan1KG5Aexcavatortoothwearplatformwhenworkingrockswithresistance0.8,0.4,0.2,and0.1ofstandardthrustforce.Fig.2.Workingpartofacuttingelementwithwedgeangle180°1cuttingedgewithareaSobedgewidthDlength2wearplatformsurfaceareaSp21,wearplatformslopeangle.Atagivensizeoftheworkingpartofthetool,thestageofcriticalwearorpseudoadjustmentisvirtuallyabsentonrocksandgroundswithlowstrength,whiletoolsexperienceintensetwostagewearonstrong/hardrocks.Indifferentminingandgeologicconditions,itisobviouslyconvenienttoworkwithinterchangeabletools.Itiscurrentlyimpossibletocontroltheforceparametersontheworkingelementofanexcavator.Theoperatorobservestheworkofthemachinevisually,watchingitsmotionandbucketfilling.Theloadsactinguponworkingelementsandteeththusdependnotonlyonrockresistancetocutting,butlargelyonoperatorskillandexperience.Artefficientandrationalapproachtodevisingworkingtoothcomponentparametersistoconsiderthepowerofexcavatordrives.Theareaofthecuttingedgeforarectangularcuttingprofilewitha180°sharpeningcanbecalculatedfromthepressureonthewearplatformseeFig.2correspondingtotheonsetofthesecondwearstagePPISp2.iwherePisthepressureonthewearplatformwhenplatformdimensionscorrespondtothebeginningofthesecondstageP1istheratedthrustforceoftheexcavatorverticalcomponentofthecuttingforceSp2isthewearplatformareaatthesecondstageonsetiisthenumberofteethontheexcavatorbucket.ThewearplatformisdefinedintermsofthecuttingedgeareaasSOSP2sinTwhere3isthewearplatformslopeanglerelativetothebackfacetofthecuttingprofileSoiscuttingedgearea.Thepressureonthewearplatformcanbeexpressedasp.PxsinSoTheareaofthecuttingedgewhichprovidesthedesiredwearpatternforthecuttingelementisdefinedfromthesameformulaSoP1sin7Pi116/27rjU,mmVez1VjIV,,1,000m3Fig.3Fig.4Fig.3.CuttingelementswithheightenedwearresistanceUcrlinearwearcorrespondingtofirstcriticalstagebbandDbbasicwidthandlengthofcuttingedgeofwedgetoothDcalculatedlengthofcuttingedge.Fig.4.Designcontrolledwearresistanceofwedgeshapedcuttingelements1,2variationoflinearwearforatoothwithanexpandedpartandastandardtooth,respectivelyUmaxmaximumpermissiblewearVincreasedoperationresourceofnewtoothdesign.Consideringthatthecuttingedgeareaislinkedtothewearplatformbytheprecedingrelation,wecanformulatesimpletechnologicalconditionsforimprovingthedesignoftheworkingcomponentofstandardwedgeshapedteethintermsofoptimallengthofthetoothcuttingedgeasDSp2.s_nibwhereDistheoptimalcuttingedgelengthwhichprovidessteadysinglestagewearofcuttingelementsbistheactualbasicwidthofthecuttingedgeofmassproducedwedgeteethSp2istheareaoftheplatformcorrespondingtotheonsetofsteadywearand3istheangleoftheslopeofthewearplatformwithrespecttotoothlongitudinalaxis.Figure3offerstechnologicalconceptsforreductionofcuttingelementweardynamicsbasedonmassproducedwedgeshapedteeth.ThelengthoftheexpandedpartofatoothDshouldbenotlessthancriticallinearwearUcr.Aftertheexpandedpartiswornoff,atoothacquiresthenaturalsizeoftheplatformcorrespondingtothesecondstageofsteadywear.ThisdesignwearsaccordingtoalinearrelationshipFig.4withanintensityequalto._hatofthesecondstageofwearofmassproducedteethparallelportionsofplots.Afterattainingmaximumwear,teethwouldhaveextendedservicelife,expressedinanincreasedvolumeofexcavatedrockAV.Weshouldpayspecialattentiontocreatingteethwithheightenedwearresistancewithoutmodifyingthebasicdimensionsorshapeoftheworkingcomponent.Thisisimportant,becausethisformiseasierandlessexpensivetomanufacture.Wedevelopedtheuniversalgeometryfortheworkingpartofanexcavatortoothbasedoncalculationsoftheoptimalwidthofthecuttingedgewhileretainingthemaindimensionsofstandardteethdesigns.ThetoothwiththenewworkingcomponentgeometryFig.5hascuttingedge1,linearsegmentofbackface2,andcurvilinearpart3.Thefrontfaceisformedoftwolinearsegments4and5.Thelinearsegmentofbackface2isparalleltotoothlongitudinalaxis6,situatedatdistanceIfromtheaxis\6\.Theplaneofthecuttingedgeissituatedatananglegreaterthan90°tothecuttingplane.ThishelpsformasteadycompactioncoreontheplaneOfthecuttingedge,whichpartlyprotectsitfromwear.ThecuttingedgewidthisfoundfromanempiricrelationshipWetookthetoothdesigndevelopedbytheInstituteofHeavyMachineryUralmashProductionAssociationforthebasicprototype.17776Fig.5.Designoftheworkingpartofatoothwithoptimalparameters1cuttingedge2linearportionofthebackfacet3curvilinearbackfacet4,5segmentsofthefrontfacet6longitudinaltoothaxis7wearplatformbcuingedgewidtha1initialcuttingangle/wedgeanglefdistancebetweenwedgeanglevertexandcuttingedgeAandBdimensionsoflinearsegmentsoffrontandbackfacets,respectivelyIdisplacementofbackfacetsegmentfromtoothaxisrwearplatformslopeangle.bPIsinP,D.wherebisanefficientwidthofthecuttingedgeP1istheexcavatorthrustforce,whichconsistsoftheweightofbucketandthestick,andtheforcedevelopedbythethrustmechanism3istheslopeangleofthewearplatformrelativetothetoothaxisorthelinearsegmentofthebackfacetDisthelengthofthecuttingedgePisthepressureonthewearplatformatthebeginningofthesecondstageandiisthenumberoftheteethonthebucket.Cuttingedge1shouldbeatdistancePIsinfromthevertexofthewedgeangle,whereisthewedgeangleoftheworkingpartofthetooth.Literarydataindicatethatachangeofthecuttinganglemoreprecisely,thebackangle,whichdependsonthecuttinganglegreatlyaffectstheintrusionforceofcuttingelements.Whenthebackangleofatoothisincreased,theenergycapacityofitsintrusionintothegroundtendstodecrease\7\.Weformulatedthenewtoothgeometrytakingthisfactorintoaccount.Accordingly,linearsegment2orbackfacet3isparalleltotoothaxis6,whichallowedustoincreasethebackanglebyafactorof2.02.5comparedwiththemassproducedmodel.Toreducethewearofthehorizontalcomponentofthecuttingparameteroftheexcavatorbucket,weshiftedsegment2ofthebackfacetandthuscuttingedge1byvalueFfromthetoothaxis.Thispositionoftheelementsofthetoothworkingcomponentrelativetothebucketcuttingedgereducestherateofwearbecausethedistancebetweenthetoothcuttingplaneandthebucketedgecuttingplaneisincreasedby7080foragivenlengthoftheworkingtoothpartprotrudingbeyondthebucket.Forthistoothdesign,wedefinedtherelationshipwhichcanbeusedtocalculatethedimensionsoftheworkingelementsTable1.ThelengthofthecuttingedgeDandthenumberofteethiarechosendependingonthedesignoftheexcavatorworkingelementandthegeneralmachinespecifications.Figure6showstheoreticalcurvesoftheformationofwearplatformdimensionsasafunctionoflinearwearforantKG5Aexcavator.Wecanseethatatzerowearthedesignwithefficientparametershasawearplatformof50ram.ThedesignproducedbytheUralmashProductionAssociationattainsthedesireddimensionsonlyaftersignificantlinearwearUcr.WithfurtherwearFig.6,zoneIIthewearplatformevolveslessrapidlyandthewearrateisapproximatelyequaltothatof118

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