embedded

ABAQUSAnalysisUr'sManual

20.4.1Embeddedelements

Products:ABAQUS/StandardABAQUS/ExplicitABAQUS/CAE

References

•“Kinematicconstraints:overview,”Section20.1.1

•*EMBEDDEDELEMENT

•“Definingembeddedregionconstraints,”Section15.13.6ofthe

ABAQUS/CAEUr'sManual

Overview

Theembeddedelementtechnique:

•isudtospecifyanelementoragroupofelementsthatlie

embeddedinagroupofhostelementswhoresponwillbeudto

constrainthetranslationaldegreesoffreedomoftheembeddednodes

(i.e.,nodesofembeddedelements);

•canbeudingeometricallylinearornonlinearanalysis;

•isnotavailableforhostelementswithrotationaldegreesoffreedom;

•canbeudtomodelatofrebar-reinforcedmembrane,shell,or

surfaceelementsthatlieembeddedinatofthree-dimensional

solid(continuum)elements;atoftrussorbeamelementsthatlie

embeddedinatofsolidelements;oratofsolidelementsthat

lieembeddedinanothertofsolidelements;

•willnotconstrainrotationaldegreesoffreedomoftheembedded

nodeswhenshellorbeamelementsareembeddedinsolidelements;and

•canbeimportedfromABAQUS/StandardintoABAQUS/Explicitandvice

versa.

Introduction

Theembeddedelementtechniqueisudtospecifythatanelementorgroup

ofelementsimbeddedin“host”eddedelement

archesforthe

geometricrelationshipsbetweennodesoftheembeddedelementsandthehost

eofanembeddedelementlieswithinahostelement,the

translationaldegreesoffreedomatthenodeareeliminatedandthenode

becomesan“embeddednode.”Thetranslationaldegreesoffreedomofthe

embeddednodeareconstrainedtotheinterpolatedvaluesofthe

edelementsare

allowedtohaverotationaldegreesoffreedom,buttherotationsarenot

leembeddedelementdefinitionsare

allowed.

Availableembeddedelementtypes

Differentelementtypescanbeudintheelementtcontainingembedded

r,allthe

hostelementscanhaveonlytranslationaldegreesoffreedom,andthe

numberoftranslationaldegreesoffreedomatanodeontheembedded

elementmustbeidenticaltothenumberoftranslationaldegreesoffreedom

lowinggeneraltypesof“embedded

elements-in-hostelements”areprovided:

•Two-dimensionalmodels:

•Beam-in-solid

•Solid-in-solid

•Truss-in-solid

•Axisymmetricmodels:

•Membrane-in-solid(ABAQUS/Standardonly)

•Shell-in-solid

•Solid-in-solid

•Surface-in-solid(ABAQUS/Standardonly)

•Three-dimensionalmodels:

•Beam-in-solid

•Membrane-in-solid

•Shell-in-solid

•Solid-in-solid

•Surface-in-solid

•Truss-in-solid

Specifyingthehostelements

Bydefault,theelementsinthevicinityoftheembeddedelementsare

archedforelementsthatcontainembeddednodes;theembeddednodesare

lude

certainelementsfromconstrainingtheembeddednodes,youcandefinea

hostelementt;thearchwillbelimitedtothissubtofthehost

atureisstronglyrecommendediftheembedded

nodesareclotodiscontinuitiesinthemodel(cracks,contactpairs,

etc.).

InputFileUsage:

*EMBEDDEDELEMENT,HOSTELSET=name

The*EMBEDDEDELEMENToptionmustbeincludedinthe

le*EMBEDDED

ELEMENToptionsareallowed.

ABAQUS/CAEUsage:

Interactionmodule:CreateConstraint:Embeddedregion:

chooSelectRegionfromthepromptareawhen

lectingthehostregion

Specifyingtheembeddedelements

dualelementsorelementts

canbespecified.

odes,

however,willnotbeconsideredtobeembeddednodes.

InputFileUsage:

*EMBEDDEDELEMENT

embeddedelements

ABAQUS/CAEUsage:

Interactionmodule:CreateConstraint:Embeddedregion:

lecttheembeddedregion

Defininggeometrictolerances

Ageometrictoleranceisudtodefinehowfaranembeddednodecanlie

ult,embedded

nodesmustliewithinadistancecalculatedbymultiplyingtheaveragesize

ofallnon-embeddedelementsinthemodelby0.05;however,youcanchange

thistolerance.

Youcandefinethegeometrictoleranceasafractionoftheaveragesizeof

atively,youcandefinethe

geometrictoleranceasanabsolutedistanceinthelengthunitschonfor

pecifybothexteriortolerances,ABAQUSusthetighter

eriortoleranceforembeddedelementsinhost

elementsisindicatedbytheshadedregioninFigure20.4.1–1.

Figure20.4.1–1Theexteriortoleranceforembeddedelements.

Ifanembeddednodeislocatedinsidethespecifiedtolerancezone,the

itionofthisnodewillbe

bedded

nodeislocatedoutsidethespecifiedtolerancezone,anerrormessagewill

beissued.

InputFileUsage:

Uthefollowingoptiontodefinethetoleranceasafraction:

*EMBEDDEDELEMENT,EXTERIORTOLERANCE=tolerance

Uthefollowingoptiontodefinethetoleranceasan

absolutedistance:

*EMBEDDEDELEMENT,

ABSOLUTEEXTERIORTOLERANCE=tolerance

ABAQUS/CAEUsage:

Interactionmodule:CreateConstraint:Embeddedregion:

FractionalexteriortoleranceorAbsoluteexterior

tolerance

Adjustingthepositionsofembeddednodes

Ifanembeddednodeliesclotoanelementedgeoranelementfacewithin

ahostelement,itiscomputationallyefficienttomakeasmalladjustment

tothepositionoftheembeddednodesothatthenodewilllieprecilyon

tolerance,belowwhichthe

weightfactorsofthenodesonahostelementassociatedwithanembedded

nodewillbezeroedout,llweightfactorswillbe

redistributedtotheothernodesonthehostelementinproportiontotheir

initialweights,andthepositionoftheembeddednodewillbeadjusted

justmentisperformedonlyatthe

mostufulformakingsmalladjustmentstomaketheembeddednodeslieon

genondefaultvalueofthe

roundofftoleranceisudtomakesignificantadjustmentstothepositions

oftheembeddednodes,youshouldcarefullyreviewthemeshobtainedafter

adjusting.

InputFileUsage:

*EMBEDDEDELEMENT,ROUNDOFFTOLERANCE=tolerance

ABAQUS/CAEUsage:

Interactionmodule:CreateConstraint:Embeddedregion:

Weightfactorroundofftolerance

Uwithothermultiplekinematicconstraintsin

ABAQUS/Standard

InABAQUS/Standardifanembeddednodeisalsotiedbymulti-point,

equation,kinematiccoupling,surface-badtie,orrigidbodyconstraints,

boundaryconditionisappliedtoanembeddednode,theembeddedelement

ndaryconditionwillbe

neglected,andawarningmessagewillbeissued.

Limitations

Thefollowinglimitationxistfortheembeddedelementtechnique:

•Elementswithrotationaldegreesoffreedomcannotbeudashost

elements.

•Rotational,temperature,porepressure,acousticpressure,and

electricalpotentialdegreesoffreedomatanembeddednodearenot

constrained.

•Hostelementscannotbeembeddedthemlves.

•Thematerialdefinedforthehostelementisnotreplacedbythe

materialdefinedfortheembeddedelementatthesamelocationofthe

integrationpoint.

•Additionalmassandstiffnessduetotheembeddedelementsareadded

tothemodel.

Example

ConsidertheexampleinFigure20.4.1–2.

Figure20.4.1–2Elementslieembeddedinhostelements.

Elements3(truss)and4(membrane)t1isformed

bynodesa,b,c,d,e,f,g,andh;element2isformedbynode,f,g,h,i,j,k,andl;

element3isformedbynodesAandB;andelement4isformedbynodesC,D,E,

thehostelementtincludelements1and2andtheembeddedelementtscontain

elements3and4,respectively,ABAQUSwillattempttofindifthereareanyembedded

nodes(A,B,C,D,E,andF)Aisfoundtobelying

clotothea-b-f-efaceofelement1,allthedegreesoffreedomatnodeAareconstrainedto

nodesa,b,f,ande,withappropriateweightfactorsbeingdeterminedbadonthegeometric

rly,ifnodeBisfoundtobelyinginsideelement1and

nodeEisfoundtobelyingclototheg–kedgeofelement2,respectively,allthedegreesof

freedomatnodeBareconstrainedtonodesa,b,c,d,e,f,g,andh,andallthedegreesof

freedomatnodeEareconstrainedtonodesgandk,withappropriateweightfactorsbeing

determinedbadonthegeometriclocationofnodeBinelement1andthegeometriclocation

ofnodeEontheg–kedgeofelement2,respectively.

Youshouldmakesurethatallthenodesontheembeddedelementsare

nbeverifiedby

performingadatacheckanalysis(e“Executionprocedurefor

ABAQUS/StandardandABAQUS/Explicit,”Section3.2.2).Foreachembeddednode

alistofnodesthatareudtoconstrainthisnodeandtheassociated

weightfactorsareoutputtothedatafileduringthedatacheckanalysis.

Anerrormessageisissuedifanembeddednodeisnotconstrained.

Template

*HEADING

…

*NODE

Datalinetodefinethenodalcoordinates

*ELEMENT,TYPE=C3D8,ELSET=SOLID3D

Datalinetodefinethesolidelements

*ELEMENT,TYPE=T3D2,ELSET=TRUSS

Datalinetodefinethetruslements

*ELEMENT,TYPE=M3D4,ELSET=MEMB

Datalinetodefinethemembraneelements

*EMBEDDEDELEMENT,EXTERIORTOLERANCE=tolerance,HOSTELSET=SOLID3D

TRUSS,MEMB

*STEP

*STATIC(oranyotherallowableprocedure)

Datalinetodefinesteptimeandcontrolincrementation

…

*ENDSTEP

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