HeliusMCT v2 for Abaqus Example Problem_0.docx

《HeliusMCT v2 for Abaqus Example Problem_0.docx》由会员分享，可在线阅读，更多相关《HeliusMCT v2 for Abaqus Example Problem_0.docx（5页珍藏版）》请在优知文库上搜索。

1、HeliusMCTv2forAbaqusExampleProblemPage8of22ValueNormalizedNormalizedNormaIizedpsi(ij/11)(ij/22)(ij/12)11267,057100.0%1015.6%1575.6%2225,5409.6%100.0%150.7%333,6231.4%14.2%21.4%1216,9496.3%66.4%100.0%131,2740.5%5.0%7.5%239320.3%3.6%5.5%StressComponentFigUre5:StressstateofselectedelementPage9of22El.3.

2、2FirstFailureAnaIySiSsafirstattemptataprogressivefailureanalysis,athrough-thicknessmeshdensityof1elementperfacesheetand1elementforthecore,foratotalof3elementsthroughthethicknessofthesandwichconstructionisused.Inthiscase,theC3D8R(reducedintegrationelement)isused.Notethatitispossibletouseasingleelemen

3、tthroughthethicknessoftheentirelaminatedsandwichstructure;however,duetotherelativelyhighcomplianceofthethickfoamcore,theuseofasingleelementthroughthelaminatethicknessyieldsveryinaccurateresults.Model(三)IelemFaceIelemCore.inpElementtype:C3D8RThrough-thicknessmeshdensity:oCompositeHacesheets:1elemento

4、FoamCore:1elementResultsTable2displaystheloadlevelatwhicheachtypeoffailureeventispredicted.ThecriteriausedtopredictlocalizedmatrixfailureandlocalizedfiberfailurearedescribedindetailintheHelius:MCTTheoryManual.InTable2,itshouldbeemphasizedthatthematrixfailureandfiberfailureloadlevelsindicatetheloadat

5、whichalocalizedmatrixorfiberfailureisfirstdetected.NotethatthisfirstinstanceofmatrixfailureorfiberfailureoccursatasingleGaussianintegrationpointwithinoneofthematerialpliesofoneoftheelementsofthemodel.Inalargecompositestructurecontainingthousands(ormilions)ofGaussianintegrationpoints,averylargenumber

6、oflocalizedconstituentfailuresarenecessaryinordertodetectanyappreciablechangeintheoveral1stiffnessofthecompositestructure.Globalstructuralfailurecanbedefinedinmanydifferentways,butforthepurposeofthisexampleproblem,globalfailureisdefinedasalargediScontinuityinthecompositestructuresoveral1verticalload

7、-displacementcurve.TheoverallverticaldeformationofthecompositestructureisquantifiedbyusingtheverticaldisplacementattheloadapplicationpointlabeledOinFigure1.Becausetheloadheadandadapterareconsideredrigid,alargediscontinuityintheload-displacementcurveisindicativeofveryrapidgrowth(spreading)oflocalized

8、materialfailuresthatoccurduringaparticularloadincrement,resultinginalargedegradationoftheoveral1stiffnessofthecompositestructure.Thisdefinitionofglobalstructuralfailureischosensincemostexperimentaltestsarestoppedatthispointtopreventdamagetoexpensivetestequipment.Figure6showstheoveral1verticalload-de

9、flectioncurveforthecompositestructure.Notethattheoverallresponseofthestructureappearstobelinearuptoaloadlevelof56%,atwhichtimeaglobalstructuralfailureoccurs.AsseeninTable2,thefirstlocalizedmatrixfailureoccurredataloadof49%andthefirstlocalizedfiberfailureoccurredataloadof49%.However,allofthelocalized

10、failuresthatoccurredbetweentheloadrangeof49%and56%werenotsufficienttoproduceavisuallydetectablechangeinthecompositestructuresoverallload-deflectionresponse.Whentheloadisincreasedfrom56%to57%,averylargecascadeoflocalizedfailuresoccurs.Thisfailurecascadeissignificantenoughtodestroyapproximately92%ofth

11、everticalstiffnessofthecompositestructure(theverticaldisplacementincreasesbyafactorof12duringtheloadincrement).Thistypeofbehavior,wheretheoverallresponseofthecompositestructureremainsapproximately1inearuptoglobalstructuralfailureisfairlycommonamongstructurescomposedofbrittlecompositecapturestheentir

12、elayup(3elementsthrough-thickness).1stmodification:Increasethecoremeshdensitytoallow4elementstocapturethecoreprofile(6elementsthrough-thickness).2ndmodification:Increasethefacesheetdensitytoa11ow2elementstocapturethelayupofeachfacesheet(8elementsthrough-thickness).3rdmodification:Increasethefaceshee

13、tdensitytoallow4elementstocapturethelayupofeachfacesheet(12elementsthrough-thickness).Ideally,averyfinethrough-thicknessmeshwouldbeutilizedtoprovidethemostaccurateloadingdistributionanddeformationthroughoutthemodel,butruntimecostsoftenlimitmeshdensities.Model(三)1e1emFace_4e1emCore.inpElementtype:C3D

14、8RThrough-thicknessmeshdensity:ofacesheets:1elementocore:4elements2elemFace_4elcmCore.inpElementtype:C3D8RThrough-thicknessmeshdensity:ofacesheets:2elementsocore:4elements4e1emFace_4elemCore.inpElementtype:C3D8RThrough-thicknessmeshdensity:ofacesheets:4elementsocore:4elementsPage12of22ResultsTable3d

15、isplaystheloadlevelatwhicheachtypeoffailureeventispredictedbythefourmodels.Figure7displaystheoverallverticalload-displacementcurvesfortheresultofthistrendisthatthemagnitudeofthepeakin-plancstressestendstodecreaseasthethrough-the-thicknessmeshdensityisincreased,thuslocalizedfailureispredictedtooccura

16、thigherloadlevels.2.Globalfailureisonlyslightlyaffectedbymeshdensity.-Despitethefactthatincreasingthethrough-the-thicknessmeshdensityresultsindelayedlocalfailureinitiationforboththematrixandthefiber,thepredictedglobalstructuralfailureloadisnotsignificantlyaffectedbythethrough-the-thicknessmeshdensity.Thisobservationsuggeststhattheescalationfromlocalfailureinitiationtoglobalstructuralfailureoccursfasterasthethrough-the-thicknessmeshdensityisincreased.Itisreasonabletoexpectloc