Finite element modelling of the fracture behaviour of brittle coatings.pdf

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1、Surface&CoatingsTechnology200(2006)5318–5327www.elsevier.com/locate/surfcoatFiniteelementmodellingofthefracturebehaviourofbrittlecoatingsP.Bansal*,P.H.Shipway,S.B.LeenSchoolofMechanical,MaterialsandManufacturingEngineering,UniversityofNottingham,UniversityPark,Nott

2、inghamNG72RD,UKReceived11April2005;acceptedinrevisedform22June2005Availableonline15August2005AbstractDuringbending,thecrackdensityinabrittlecoatingincreasesgraduallywithincreasingloadandcanbemonitoredusingtheacousticemission(AE)technique.Itisalsoknownthattheformati

3、onofcracksincoatingsresultsinstressrelaxationaroundthecrackwhichwillalsoaffectsubsequentfracturebehaviour.Uptonow,thesignificanceofstressrelaxationduetocrackingonsubsequentacousticemissionbehaviourhasnotbeenfullyanalysed.Inthiswork,theAEresponseofabrittlecoatingiss

4、tudiedintermsofitsfractureproperties.Afiniteelementmodel(FEM)ofabrittlecoatingonanelasticsubstrateinfour-pointbendingispresented.Inthemodel,crackingisassumedtooccuroncethesurfacetensilestresseshaveexceededacertaincriticalvalue.ResultsfromtheFEMshowgoodagreementwith

5、workdonebyothers.ThedevelopmentoftheFEMmakesitpossibletostudytheeffectofvariouscoatingparametersinisolationwhichisdifficulttoachieveinanexperimentalstudy.D2005ElsevierB.V.Allrightsreserved.Keywords:FEM;HVOF;WC-Co;Residualstress1.Introductionsubstratecanbepreventedb

6、yplasticdeformationaroundthecracktip(associatedwithlowstrengthsubstrates)[2]orCoatingsareusedinvariousengineeringapplicationsbythehighstiffnessortoughnessofthesubstrate[3].Atandareappliedtopreventdamagetocomponentsduringthisstagethecrackmaypropagatealongthecoating-

7、usageandconsequentlytoenhancelongevity.Coatingsubstrateinterface,oralternatively,additionalthrough-failuremayrenderthesecomponentsunusableandmaythicknesscracksmaydevelopinthecoating.Inbrittleresultinsignificanteconomicloss.Understandingofthecoatings,thereisadistrib

8、utionofflaws(andthusstrengths)fracturebehaviourofcoatingsthereforeassistsinthedesignandthusthefirstcrackinthecoatingformsatthesitewithofcoatingsw