外文翻译--开采机械化及自动化 英文版.pdf

MININGMECHANIZATIONANDAUTOMATIONGEOMETRYOFTHEWORKINGPARTOFANEXCAVATORTOOTHV.A.PolovinkoandA.I.FedulovUDC621.879.3Studiesofexcavatortoothwearkineticsconductedearlierbythepresentauthors1,2showedthatthemainfactorcontrollingwearplatformdynamicsisthephysical-mechanicalpropertyoftherock.Wearplatformsevolveintwostages.Toothwearacquiredduringthe"critical"stage2hasnosignificantinfluenceonexcavatorperformanceintheminingandgeologicconditionstypicalforthenortheasternregionsofRussia.Cuttingelementscancontinuetobeuseduptothemaximumpermissiblewearlevelspecifiedbythemanufacturer.Inthisrespect,intensivewearduringinitialstagesapparentlyreflectssomedesignimperfectionratherthantheeffectsoftheworkadjustmentprocess.Investigatorshavestudiedthecausesandconsequencesofintensewearofexcavatorteeth,buttherearestillnobasiccriteriauponwhichtoformulategeneralprinciplessoastoimprovethewearresistanceofcuttingelementsasdeterminedbytheirdesign3-5.Anefficientwaytoraisethewearresistanceofanexcavatortoothistodevisethedesignparametersoftheworkingcomponentsoastoensureclassicalsingle-stagewear,bypassingthe"critical"(pseudoadjustment)phase.Wedevelopedanewexcavatortoothdesignwhichfeaturesheightenedwearresistance.Theoutlineoftheworkingcomponentofthetoothanditsdimensionsweredevelopedwithdueregardforthemaincharacteristicpointsofthewearresistancecurvesofmass-producedwedge-shapedteeth.Toattainalinearbehaviorforthewearprocessofsuchteethwitharateequaltoorlessthanwhatisobservedduringthesecondstageofwearwithmass-producedteeth,wespecifiedthedesignparameterscorrespondingtothebeginningofthesecondphase,wherethespecificpressurefromthestandardforceofthethrustmechanismdropsto10-12MPa.Figure1plotspressurevariationsonthewearplatformsofteethofbucketsusedincommonquarryexcavatorsaccordingtothefollowingexpression:P1whereUpisthewidthofthewearplatform；P1istheratedforceofthethrustmechanism；Dandiarethelengthofthetoothcuttingedgeandthenumberofteethonthebucket,respectively.Thecurvesshowthattherearecertainpressureregionsonwearplatformswhererockresistancetoteethisequaltoorgreaterthantheforcedevelopedbythethrustmechanism.Thisloadingpatternforcuttingelementsisobservedonmonolithicstrong(e.g.,permafrost)rocks.Ontheotherhand,somematerialsresistcuttingwithamuchweakerstrengththantheforcedevelopedbythisthrustmechanism.Toestimatethespecificpressuresformedwhencuttingelementsinteractwiththesematerials,weplottedcurves1-4bycomputingthepressureonthewearplatformsofantKG-5Aexcavatortoothat0.8,0.4,0.2,and0.1oftheratedthrustforce.Onweakrocksthepressurevariationpatternonthewearplatformisthesame,butthepressuresanddimensionsforthewornportionofteethafterthebeginningofthesecondstagemaybemuchsmaller(sometimesbyaconsiderablefactor).ThisisclearlyseeninFig.1.ZoneI,crossingthecurves,definestheparametersoftheonsetofthesecondstageofwearforteethofdifferentexcavatorsandfordifferentrockstrengths(curves1-4).ForIKG-5AexcavatorteeththestartingpointofthesecondwearstageobtainedexperimentallyliesinzoneIandcorrespondstoapressureofP=10-12MPaandawearplatformwidthofUtcr=45mm.InstituteofMining,SiberianBranch,RussianAcademyofSciences,Novosibirsk.TranslatedfromFiziko-TekhnicheskieProblemyRazrabotkiPoleznykhIskopaemykh,No.2,pp.16-23,March-April,1993.Originalarticlesubmit-tedNovember4,1992.1062-7391/93/2902-0115512.50©1993PlenumPublishingCorporation1150MPatl/(.OEKG-20EKG-12,5EKG-$I5AUpUp,mmFig.1Fig.2Fig.1.Pressurevariationasafunctionofwearplatformsize(1-4-theoreticalpressurecurvesonan1KG-5Aexcavatortoothwearplatformwhenworkingrockswithresistance0.8,0.4,0.2,and0.1ofstandardthrustforce).Fig.2.Workingpartofacuttingelementwithwedgeangle180°(1cuttingedgewithareaSo；b-edgewidth；D-length；2-wearplatformsurfaceareaSp2；1,-wearplatformslopeangle.Atagivensizeoftheworkingpartofthetool,thestageofcriticalwearorpseudoadjustmentisvirtuallyabsentonrocksandgroundswithlowstrength,whiletoolsexperienceintensetwo-stagewearonstrong/hardrocks.Indifferentminingandgeologicconditions,itisobviouslyconvenienttoworkwithinterchangeabletools.Itiscurrentlyimpossibletocontroltheforceparametersontheworkingelementofanexcavator.Theoperatorobservestheworkofthemachinevisually,watchingitsmotionandbucketfilling.Theloadsactinguponworkingelementsandteeththusdependnotonlyonrockresistancetocutting,butlargelyonoperatorskillandexperience.Artefficientandrationalapproachtodevisingworkingtoothcomponentparametersistoconsiderthepowerofexcavatordrives.Theareaofthecuttingedgeforarectangularcuttingprofilewitha180°sharpeningcanbecalculatedfromthepressureonthewearplatform(seeFig.2)correspondingtotheonsetofthesecondwearstage:P=PISp2.iwherePisthepressureonthewearplatformwhenplatformdimensionscorrespondtothebeginningofthesecondstage；P1istheratedthrustforceoftheexcavator(verticalcomponentofthecuttingforce)；Sp2isthewearplatformareaatthesecondstageonset；iisthenumberofteethontheexcavatorbucket.ThewearplatformisdefinedintermsofthecuttingedgeareaasSOSP2=sinTwhere3isthewearplatformslopeanglerelativetothebackfacetofthecuttingprofile；Soiscuttingedgearea.Thepressureonthewearplatformcanbeexpressedasp=.Px"sin?So-Theareaofthecuttingedgewhichprovidesthedesiredwearpatternforthecuttingelementisdefinedfromthesameformula:So-P1"sin7P-i116/2?"-7r"j""U,mmVez1VjIV,×1,000m3Fig.3Fig.4Fig.3.Cuttingelementswithheightenedwearresistance(Ucr-linearwearcorrespondingtofirstcriticalstage；bbandDb-basicwidthandlengthofcuttingedgeofwedgetooth；D-calculatedlengthofcuttingedge).Fig.4.Design-controlledwearresistanceofwedge-shapedcuttingelements(1,2varia-tionoflinearwearforatoothwithanexpandedpartandastandardtooth,respectively；Umax-maximumpermissiblewear；&V-increasedoperationresourceofnewtoothdesign.Consideringthatthecuttingedgeareaislinkedtothewearplatformbytheprecedingrelation,wecanformulatesimpletechnologicalconditionsforimprovingthedesignoftheworkingcomponentofstandardwedge-shapedteethintermsofoptimallengthofthetoothcuttingedgeasD=Sp2.s_ni?bwhereDistheoptimalcuttingedgelengthwhichprovidessteadysingle-stagewearofcuttingelements；bistheactual(basic)widthofthecuttingedgeofmass-producedwedgeteeth；Sp2istheareaoftheplatformcorrespondingtotheonsetofsteadywear；and3istheangleoftheslopeofthewearplatformwithrespecttotoothlongitudinalaxis.Figure3offerstechnologicalconceptsforreductionofcuttingelementweardynamicsbasedonmass-producedwedge-shapedteeth.Thelengthoftheexpandedpartofatooth(D)shouldbenotlessthancriticallinearwearUcr.Aftertheexpandedpartiswornoff,atoothacquiresthenaturalsizeoftheplatformcorrespondingtothesecondstageofsteadywear.Thisdesignwearsaccordingtoalinearrelationship(Fig.4)withanintensityequalto*._hatofthesecondstageofwearofmass-producedteeth(parallelportionsofplots).Afterattainingmaximumwear,teethwouldhaveextendedservicelife,expressedinanincreasedvolumeofexcavatedrock(AV).Weshouldpayspecialattentiontocreatingteethwithheightenedwearresistancewithoutmodifyingthebasicdimensionsorshapeoftheworkingcomponent.Thisisimportant,becausethisformiseasierandlessexpensivetomanufac-ture.Wedevelopedtheuniversalgeometryfortheworkingpartofanexcavatortoothbasedoncalculationsoftheoptimalwidthofthecuttingedgewhileretainingthemaindimensionsofstandardteethdesigns.*Thetoothwiththenewworkingcomponentgeometry(Fig.5)hascuttingedge1,linearsegmentofbackface2,andcurvilinearpart3.Thefrontfaceisformedoftwolinearsegments4and5.Thelinearsegmentofbackface2isparalleltotoothlongitudinalaxis6,situatedatdistanceI"fromtheaxis6.Theplaneofthecuttingedgeissituatedatananglegreaterthan90°tothecuttingplane.ThishelpsformasteadycompactioncoreontheplaneOfthecuttingedge,whichpartlyprotectsitfromwear.Thecuttingedgewidthisfoundfromanempiricrelationship:*WetookthetoothdesigndevelopedbytheInstituteofHeavyMachinery(UralmashProductionAssociation)forthebasicprototype.!17776"Fig.5.Designoftheworkingpartofatoothwithoptimalparameters(1-cuttingedge；2-linearportionofthebackfacet；3-curvilinearbackfacet；4,5-segmentsofthefrontfacet；6-longitudinaltoothaxis；7-wearplatform；b=cuingedgewidth；a1=initialcuttingangle；/=wedgeangle；f=distancebetweenwedgeanglevertexandcuttingedge；AandB=dimensionsoflinearsegmentsoffrontandbackfacets,respectively；I"=displacementofbackfacetsegmentfromtoothaxis；"r=wearplatformslopeangle.bPI"sinP,D.wherebisanefficientwidthofthecuttingedge；P1istheexcavatorthrustforce,whichconsistsoftheweightofbucketandthestick,andtheforcedevelopedbythethrustmechanism；3istheslopeangleofthewearplatformrelativetothetoothaxis(orthelinearsegmentofthebackfacet)；Disthelengthofthecuttingedge；Pisthepressureonthewearplatformatthebeginningofthesecondstage；andiisthenumberoftheteethonthebucket.Cuttingedge1shouldbeatdistancePI"sin"fromthevertexofthewedgeangle,whereisthewedgeangleoftheworkingpartofthetooth.Literarydataindicatethatachangeofthecuttingangle(moreprecisely,thebackangle,whichdependsonthecuttingangle)greatlyaffectstheintrusionforceofcuttingelements.Whenthebackangleofatoothisincreased,theenergycapacityofitsintrusionintothegroundtendstodecrease7.Weformulatedthenewtoothgeometrytakingthisfactorintoaccount.Accordingly,linearsegment2orbackfacet3isparalleltotoothaxis6,whichallowedustoincreasethebackanglebyafactorof2.0-2.5comparedwiththemass-producedmodel.Toreducethewearofthehorizontalcomponentofthecuttingparameteroftheexcavatorbucket,weshiftedsegment2ofthebackfacet(andthuscuttingedge1)byvalueFfromthetoothaxis.Thispositionoftheelementsofthetoothworkingcomponentrelativetothebucketcuttingedgereducestherateofwearbecausethedistancebetweenthetoothcuttingplaneandthebucketedgecuttingplaneisincreasedby70-80%foragivenlengthoftheworkingtoothpartprotrudingbeyondthebucket.Forthistoothdesign,wedefinedtherelationshipwhichcanbeusedtocalculatethedimensionsoftheworkingelements(Table1).Thelengthofthecuttingedge(D)andthenumberofteeth(i)arechosendependingonthedesignoftheexcavatorworkingelementandthegeneralmachinespecifications.Figure6showstheoreticalcurvesoftheformationofwearplatformdimensionsasafunctionoflinearwearforantKG-5Aexcavator.Wecanseethatatzerowearthedesignwithefficientparametershasawearplatformof=50ram.ThedesignproducedbytheUralmashProductionAssociationattainsthedesireddimensionsonlyaftersignificantlinearwearUcr.Withfurtherwear(Fig.6,zoneII)thewearplatformevolveslessrapidlyandthewearrateisapproximatelyequaltothatof118