沥青路面自上向下裂缝传播的模拟外文翻译Word下载.docx
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Top-downcrackinasphaltpavementshasbeenreportedasawidespreadmodeoffailure.Asolidunderstandingofthemechanismsofcrackgrowthisessentialtopredictpavementperformanceinthecontextofthicknessdesign,aswellasinthedesignandoptimizationofmixtures.UsingthecoupledelementfreeGalerkin(EFG)andfiniteelement(FE)method,top-downcrackpropagationinasphaltpavementsisnumericallysimulatedonthebasisoffracturemechanics.Aparametricstudyisconductedtoisolatetheeffectsofoverlaythicknessandstiffness,basethicknessandstiffnessontop-downcrackpropagationinasphaltpavements.Theresultsshowthatlongitudinalwheelloadsaredisadvantageoustotop-downcrackbecauseitincreasesthecompoundstressintensityfactor(SIF)atthetipoftop-downcrackandshortensthecrackpath,andthusthefatiguelifedescends.TheSIFexperiencesaprocess“sharplyascending—slowlydescending—slowlyascending—sharplyascendingagain”withthecrackpropagating.Thethickertheoverlayorthebase,thelowertheSIF;
thegreatertheoverlaystiffness,thehighertheSIF.Thecrackpathishardlyaffectedbystiffnessoftheoverlayandbase.
Keywords:
Roadengineering;
Top-downcrack;
CoupledelementfreeGalerkin(EFG)andfiniteelement(FE)method;
Stressintensityfactor(SIF);
Crackpropagatingpath
1Introduction
Crackingisoneofthemostinfluentialdistressesthatgoverntheservicelifeofasphaltconcretepavements.Sincecrackingleadstowaterpenetration,therebyweakeningthefoundationofthepavementstructureandcontributingtoincreasedroughness,anumberofstudieshavebeenconductedtoobtainabetterunderstandingofcrackingmechanismsinasphaltconcretepavements.Asolidunderstandingofthemechanismsofcrackgrowthisessentialtopredictpavementperformanceinthecontextofthicknessdesign,aswellasinthedesignandoptimizationofmixtures.Top-downcrackinasphaltpavementshasbeenreportedasawidespreadmodeoffailure.Recently,moststudiesontop-downcrackofasphaltpavementshavefocusedontheinitiation(Svasdisantetal.,2002;
Wangetal.,2003),butthemechanismsfortop-downcrackpropagationhavenotbeencompletelyexplained,onlylittleliteratureinvolved(Sangpetngametal.,2004;
Maoetal.,2004).Thetheoryoffracturemechanicshasbeenusedasabasisforpredictingcrackgrowthinasphaltmixtures.Butthecomplexityoftheproblemandthelackofsimple-to-useanalysistoolshavebeenobstaclestoabetterunderstandingofhot-mixasphaltfracturemechanics.Untiltoday,thewell-knownfiniteelement(FE)methodhasbeentheprimarytoolusedformodelingcracksandtheireffectsinmixturesandpavements(Songetal.,2006).Unfortunately,itisbothcomplexandnumericallyintensiveforfracturemechanicsapplications.Someresearcherspredictedcrackgrowthinasphaltmixtureswiththeboundaryelementmethod(BEM)(Sangpetngametal.,2004),buttheBEMisnotcapableofdealingwiththemulti-mediumissuesandcomplicatednonlinearproblems.TheelementfreeGalerkin(EFG)methodisadvantageousinsolvingmovingboundaryproblems,suchasmodelingofgrowingcracks.FundamentallyinEFG,astructuredmeshisnotused,sinceonlyascatteredsetofnodalpointsisrequiredinthedomainofinterest.Thisfeaturepresentssignificantimplicationsformodelingfracturepropagation,becausethedomainofinterestiscompletelydiscretizedbyasetofnodes.Sincenoelementconnectivitydataareneeded,theburdensomeremeshingrequiredbytheFEmethodcanbeavoided.AlthoughEFGisattractiveforsimulatingcrackpropagation,itcostsmorecomputationaltimethanaregularFE,andtheimpositionoftheessentialboundaryconditionsiscomplicated.Furthermore,duetothelevelofmaturityandcomprehensivecapabilitiesofFE,itisoftenadvantageoustouseEFGonlyinthesub-domainswhereitscapabilitiescanbeexploitedefficiently.Inthiswork,acombinationofcoupledEFGandFEmodelingandfracturemechanicswasselectedforphysicalrepresentationandanalysisofapavementwithagrowingtop-downcrack,andtheeffectonthecrackpropagationofstructuralparameterswasanalyzed.
2Numericaltheories
2.1ElementfreeGalerkinmethod
TheEFGmethodadoptsthemovingleast-squares(MLS)toconstructtheapproximatefunction(Belytschkoetal.,1994;
1995;
1996)
(1)
where
istheapproximatefunction,
istheparametervectoraboutnodes,andΦ(x)istheMLSshapefunctionwhichcouldbewrittenas
(x),(x)
(2)
(3)
(4)
ThematricesP(x)andW(x)aredefinedas
(5)
(6)
wherep(x)=[p1(x),p2(x),…,pm(x)]isthebasisfunction,andmistheorderofthebasisfunction;
w(x−xi)istheweightfunctionassociatedwithnodei.Inthisstudy,alinearbasicfunctionandcubicspl