船体结构的焊接工艺外文文献.docx

船体结构的焊接工艺外文文献.docx

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船体结构的焊接工艺外文文献

AnewalgorithmonweldingprocessofT-shapedplatesinshiphullstructuretominimizedistortionbasedonthermalsimulation

MehdiIranmanesha,NavidAzadaandMahmoodZabihpoorb,∗

aMarineEngineeringDepartment,AmirkabirUniversityofTechnology,Tehran,Iran;bSpaceTechnologyCenter,

Tehran,Iran

（Received28April2013;accepted28January2014）

Inthispaper

TheinfluenceofweldingsequenceonthedistributionofdistortiononaT-shapedplatebarisinvestigated.Thesimulationconsistsofsequentiallycoupledthermalandmechanicalanalysesusinganelementbirthanddeathtechniquetomodeltheadditionofweldingmetaltotheworkpiece.ThermaldistributioninsteelT-shapedplatesubjectedtogasmetalarcweldingisdeterminedthroughfiniteelementmethod（FEM）innumericalsimulations.Three-dimensional（3D）thermalmodelissimulatedinANSYSFEMcommercialcode.AmacrocodeprogrammebasedonGoldakmodelisdevelopedtoapplythermalloadinggeneratedbytheheatsources.Theanalysesareplannedtobeperformedfor3D,transientandnon-linearconditions.Temperaturedistributionduringwelding,welding-induceddistortionfieldsandthermalgraphsarepredicted.Theresultsarecomparedwiththepredictionsfrommechanicalanalyses.Theresultsoffourweldingsequencesonthemagnitudeofdistortionintheplatearediscussedandtheireffectsonthethermalsmoothdistributionforspecialpointsintheplatearestudied.Evaluationoftheresultswithminimumdistortionrepresentsproperpredictionsandprovesapplicabilityandsimplicityofthenewintroducedalgorithminthispaper.

Keywords:

weldingsequence,thermalsimulation，minimumdistortion,finiteelementmodeling

1.Introduction

Hightemperatureconcentrationisgeneratedinjointsectionsduetomeltstateoccurringinweldingprocess.Increasingtemperature,non-uniformtemperaturedistributionandcoolingratecausedistortioninweldingpieces.Ontheotherhand,occurrenceofdistortioncouldinducedeformationinthestructurecomponentsthroughwhichthetolerancesconsideredmaybeunsatisfied（Brustetal.2010）.Hence,inordertominimisedistortionontheplatesunderwelding,asuitableweldingsequenceisdevelopedthroughgeneratinguniformthermaldistribution.Asuitableweldingsequencecouldresultinuniformdistributionofresidualstresses（Feng2005）.Indeed,inapplyingprocessofthesuggestedalgorithm,nospecialequipmentandexpertpersonnelisneeded.Meanwhileitcouldacceleratetheprocessandreducethecosts（Messler1999）.

WatanabeandSatoh（1958）studiedbucklingbehaviorinsteelplatesthroughexperiments.Masubuchi（1959）continuedtheirworksandinvestigatedtherelationsbetweenlength,thicknessoftheplateandcorrespondingbucklingloadsfortheelementssubjectedtoweldingprocess.Taniguchi（1972）haveconductedsomeexperimentsandalsonumericalsimulationsonangularbendingofT-shapedplates.Intheconsequenceofhiswork,arelationbetweenangularvariationsversusthicknessoftheplateshasbeendevelopedfordifferentsizesofweldingpaths.Tsaietal.（1999）havestudiedtheeffectsofweldingsequencesondistortionofreinforcedpanel.Astheyconcluded,thedistortionwillbereducedwheninnerpathsaresubjectedtoweldingfirst.

MichalerisandDeBiccari（1997）evaluatednumericalandanalyticaltechniquesinpredictingdistortionduetoweldinginhugeandcomplexstructures,extensively.However,theycouldnotobtainexactresults.DengandMurakawa（2004）havedevelopedthemethodstocontroldistortionofshipstructurethinreinforcedpanel.Theyconcludedthatselectingasuitableweldingsequencecouldreducedistortioninmarinestructuressignificantly.Voutchkovetal.（2005）haveinvestigatedtheeffectsofweldingsequencesandcorrespondingresidualstresses.Theyfoundnewresultsthroughsimulationandalsoconductingexperiments.

Rajuetal.（2009）specificallyevaluatedtheeffectsofdifferentweldingsequencesonangulardistortionofT-shapedplates.Thedistortionreducedtoarangeof5°—0.11°throughconductingasuitableweldingsequenceproposedbyhim.Ozcatalbasetal.（2009）haveperformedextensiveexperimentsonbeamstructuretoinvestigatetheeffectsofweldingsequencesonfinaldistortion.Theyfoundthatthedistortionwillbereducedsignificantlyifweldingbestartedfrommidlengthofthebeamtowardtheendsandalsoiftheweldingpathsareawayenoughfromeachother.Dengetal.（2007,2008）simulatedthedistortionsduetoweldingprocessinhugestructuresnumerically.Theyfoundthatsimulationcouldpredictthedistortionasaconsequenceoftheweldingprocessrun.Canadianshipstructurecommitteehasconductedinvestigationsonweldingeffectsthroughequivalentloadmethodbasedoninherentstrain.Themethodappliedwaslimitedtoelasticanalyses（Brianetal.2008）.

HernandezArriaga（2009）hasperformedanumberofexperimentsontheweldingsequenceeffectsandcorrespondingresidualstressanddistortion.HecomparedtheresultswiththeonesfromANSYScommercialcodeAnalyses.Gannonetal.（2010）andGannon（2011）haveinvestigatedweldingsequenceeffectsondistortionofT-shapedplatesusingANSYSsoftwareandvalidatedtheresultsincomparisonwithexperiments.Ashefound,weldingsequencehasmoreintensiveeffectondistortionthanresidualstresses.

Schenk（2011）hasperformedresearchworksonweldingeffectsontheplateswithdifferentconstraints.Theresultsofhisresearchindicatesthattheshorterwelding

pathsreducethedistortion;meanwhile,implementationofdifferentweldingsequencescouldcausere-heatingofdifferentpointsoftheplateandthiscouldhavethesimilareffectofannealingprocess.Consequently,asignificantreductionindistortioncouldberesulted.Hardikaretal.（2012）haveanalyseddifferenteffectivetechniquesaboutdistortionvalueofweldingpieces.Astheyfound,weldingsequencehasanimportantroleonthevalueofdistortion.

Asmentionedabove,anumberofresearchworkswereperformedondistortionduetoweldinginwhich,timeconsumingsolutionsandnon-exactresultsinmarinecomplexstructurewereintroducedasthemainproblem（Kennoetal.2010;Gannonetal.2013）.Thisstudydescribesanewalgorithminperformingandanalysingweldingprocesswithlesstimerequiredforsolvingtheproblemwithacceptablepredictionsandreasonableerrordifferencesintheresultsthantheothers.

2.Problemstatement

Asitispresentedinhistoryofwelding,weldingsequenceshaveanimportantroleonthermalloadsdistributionandconsequentlyontheresulteddistortion.Developmentofanewalgorithmonweldingsequencecouldproposeasuitablewaytocontrolfinaldistortion.Inthissurvey,thedistortionoccurringonaT-shapedplatewillbepredictedthroughthermalsimulationatthespecialselectedpointsontheplatefordifferentweldingsequences.TheschematicofthealgorithmdevelopedispresentedinFigure1.

Figure1.Theschematicofthealgorithmdeveloped.

Asitisshown,firstandforemost,geometryofthestructureshouldbedefinedandcharacterisedindetail.AfiniteelementmodelwillbeconstructedinANSYSFEMcommercialcode.Hence,weldingsequencesonthestructurecouldbeprogrammedconsideringpredictedfinaleffectsofweldingprocess.Weldingconditionswillbedefinedbasedonthegeometryofthemodel.Then,thermalanalyseswillbeperformedforselectedpointscenario.

Byextractingthermalgraphs,weldingsequencescorrespondingtominimumdistortionwillbeobtained.Comparisonsoftheresultsfromthermalanalyseswiththeonesfrommechanicalanalysismethodvalidatetheprocedureintroducedinnewalgorithm.

Oneofthemainadvantagesofthealgorithmisreductionindependencytothenumberofmechanicalanalysesandconsequently,shorterintimeneededforitandalsolesscomplexityintheanalysesespeciallyforreal,hugeandcomplexstructures.

3.Finiteelementmodeling

Numericaltechniquessuchasfiniteelementmodellingareconventionalmethodsinpredictingtemperaturedistribution.ByusingFEM,thetimeandcostwillbereducedsignificantly.ANSYScommercialcodeisusedinthisresearchasFEMsoftware.Selectionandsimulationthetypesofheatsourcesaremostimportantinmetalweldingprocessdefinition.Inthisresearch,Goldakheatsource（Goldaketal.1984）isimplementedtosimulateinputheatpowerinweldingzone.AspresentedinFigure2,thermaldistributioncouldbedefinedas

Figure2.Ellipseheatsourceandthermaldistortionindirectionofξ（Goldaketal.1984）.

ThermalanalysisisperformedinANSYS.Temperaturedistributioncouldbeproducedbyheatsourceonweldingpath.ThegeometryofT-shapedplatemodelisintroducedinTable1.CompositionofthematerialusedisgiveninTable2.Aftersimulation,themodelshouldbesubjectedtoasuitablemeshpatterntogettheconvergenceresults.Themeshingprocesswasdonemanually,togettheacceptableaccuracy;itwasrequiredtousedifferentmeshdensityorsmartsizelocallyinsoftware.Asanexample,forthepointsneartoweldingzone,meshsizesmustbeselectedsmallerthantheotherzones.Itisduetohighertemperatureandthermalloadgradienteffects.Todeterminedistortionatthesepoints,itisneededtoobtainthermaldistortionwithhigheraccuracy.Intotal,15,200elementsaregeneratedinthemodel.MeshingpatternispresentedinFigure3whichwasintroducedtothemodelmanually.

Table1.Geometryofthemodel.

Plate

length

（mm）

Plate

Width

（mm）

Plate

Thickness

（mm）

Stiffener

Length

（mm）

Stiffener

Width

（mm）

Stiffener

Thickness

（mm）

500

500

9

500

300

9

Table2.Materialchemicalcomposition.

Chemicalcomposition（mass%）

C

Si

Mn

P

S

0.23

-

0.56

＜0.035

＜0.035

Figure3.Meshpatternappliedto