沥青路面自上向下裂缝传播的模拟外文翻译.docx

沥青路面自上向下裂缝传播的模拟外文翻译.docx

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沥青路面自上向下裂缝传播的模拟外文翻译

Simulationoftop-downcrackpropagationinasphaltpavements

Abstract:

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