机械专业毕业论文外文翻译Word下载.docx

机械专业毕业论文外文翻译Word下载.docx

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英文原文：

Experimentalinvestigationoflasersurfacetexturedparallelthrustbearings

Performanceenhancementsbylasersurfacetexturing（LST）ofparallel-thrustbearingsisexperimentallyinvestigated.Test

resultsarecomparedwithatheoreticalmodelandgoodcorrelationisfoundovertherelevantoperatingconditions.Acompari-

sonoftheperformanceofunidirectionalandbi-directionalpartial-LSTbearingswiththatofabaseline,untexturedbearingis

presentedshowingthebenefitsofLSTintermsofincreasedclearanceandreducedfriction.

KEYWORDS:

fluidfilmbearings,sliderbearings,surfacetexturing

1.Introduction

Theclassicaltheoryofhydrodynamiclubricationyieldslinear（Couette）velocitydistributionwithzeropressuregradientsbetweensmoothparallelsurfacesundersteady-statesliding.Thisresultsinanunstablehydrodynamicfilmthatwouldcollapseunderanyexternalforceactingnormaltothesurfaces.However,experienceshowsthatstablelubricatingfilmscandevelopbetweenparallelslidingsurfaces,generally

becauseofsomemechanismthatrelaxesoneormoreoftheassumptionsoftheclassicaltheory.

Astablefluidfilmwithsufficientload-carryingcapacityinparallelslidingsurfacescanbeobtained,forexample,withmacroormicrosurfacestructureofdifferenttypes.Theseincludewaviness[1]andprotrudingmicroasperities[2–4].AgoodliteraturereviewonthesubjectcanbefoundinRef.[5].Morerecently,lasersurfacetexturing（LST）[6–8],aswellasinletrougheningbylongitudinalortransversegrooves[9]weresuggestedtoprovideloadcapacityinparallelsliding.TheinletroughnessconceptofTonder[9]isbasedon‘‘effectiveclearance’’reductioninthesliding

directionandinthisrespectitisidenticaltothepar-tial-LSTconceptdescribedinref.[10]forgeneratinghydrostaticeffectinhigh-pressuremechanicalseals.

VeryrecentlyWangetal.[11]demonstratedexperimentallyadoublingoftheload-carryingcapacityforthesurface-texturedesignbyreactiveionetchingofSiCparallel-thrustbearingsslidinginwater.Thesesimpleparallelthrustbearingsareusuallyfoundinseal-lesspumpswherethepumpedfluidisusedasthelubricantforthebearings.Duetotheparallelslidingtheirperformanceispoorerthanmoresophisticatedtaperedorsteppedbearings.Brizmeretal.[12]demon-stratedthepotentialoflasersurfacetexturingintheformofregularmicro-dimplesforprovidingload-carryingcapacitywithparallel-thrustbearings.Amodelofatexturedparallelsliderwasdevelopedandtheeffectofsurfacetexturingonload-carryingcapacity

wasanalyzed.Theoptimumparametersofthedimpleswerefoundinordertoobtainmaximumload-carryingcapacity.Amicro-dimple‘‘collectiveeffect’’wasidenti-

fiedthatiscapableofgeneratingsubstantialload-carryingcapacity,approachingthatofoptimumconventionalthrustbearings.ThepurposeofthepresentpaperistoinvestigateexperimentallythevalidityofthemodeldescribedinRef.[12]bytestingpracticalthrustbearingsandcomparingtheperformanceofLSTbearingswiththatofthetheoreticalpredictionsandwiththeperformanceofstandardnon-textured

bearings

2.Background

AcrosssectionofthebasicmodelthatwasanalyzedinRef.[12]isshowninfigure

1.AsliderhavingawidthBispartiallytexturedoveraportionBp=αBofitswidth.Thetexturedsurfaceconsistsofmultipledimpleswithadiameter，depthandareadensitySp.AsaresultofthehydrodynamicpressuregeneratedbythedimplestheslidingsurfaceswillbeseparatedbyaclearancedependingontheslidingvelocityU,thefluidviscositylandtheexternalloadItwasfoundinRef.[12]thatanoptimumratioexistsfortheparameterthatprovidesmaximumdimensionlessload-carryingcapacitywhereLis

thebearinglength,andthisoptimumvalueishp=1.25.ItwasfurtherfoundinRef.[12]thatanoptimumvalueexistsforthetexturedportionadependingonthebearingaspectratioL/B.Thisbehaviorisshowninfigure2forabearingwithL/B=0.75atvariousvaluesoftheareadensitySp.AscanbeseenintherangeofSpvaluesfrom0.18to0.72theoptimumavaluevariesfrom0.7to0.55,respectively.Itcanalsobeseenfromfigure2thatfora<

0.85nooptimumvalueexistsforSpandthemaximumloadWincreaseswithincreasingSp.Hence,thelargestareadensitythatcanbepracticallyobtainedwiththelasertexturingisdesired.Itisalsointerestingtonotefromfigure2theadvantageofpartial-LST（a<

1）overthefullLST（a=1）forbearingapplications.AtSp=0.5,forexample,theloadWata=0.6isaboutthreetimeshigherthanitsvalueata=1.AfullaccountofthisbehaviorisgiveninRef.[12].

3.Experimental

ThetestedbearingsconsistofsinteredSiCdisks10mmthick,having85mmouterdiameterand40mminnerdiameter.Eachbearing（seefigure3