| Asaluminumanditsalloysarelight,goodformabilityandhavehighstrength-to-weightratio,goodmechanicalpropertiesatlowtemperatureandexcellentcorrosionresistance,theyareusedmoreandmoreintheaerospace,automotive,shipbuildingandotherfields.Laserspotweldinghashighaccuracy,highflexibilityandotheradvantages.However,cracks,collapsedandotherdefectsareoftenobservedinaluminumalloyweldsbylaserspotweldingprocess.Besides,theabilitytoresisttotensile-shearandtobridgegapispoor.Weusefillerwiretosolvetheaboveproblemsandgethighqualitywelds.UsingtheLabVIEWandNIdataacquisitioncard,sequentialpulseswereacquired,thentheopeningandclosingofthewirefeederandthelaserraster,wirefeedspeedscanbecontrolled.ByDAQAssistant,wecaneasilysetthedelaytime,wire-feedtimeandlaserspotweldingtime.Sincethelaserandthewirefeedercanbecontrolledcoordinately,thelaserspotweldingwithfillerwireiscarriedout.Theangle,heightandvolumeofthefillerwire,thedelaytimeandotherparametershaveeffectontheforminganddefectsofthewelds.Theexperimentsresultsshowthat,theangleandtheheightofthefillerwirearethekeyfactorswhichinfluencethestabilityoftheprocessofthemeltwireintothepool,whenthewirewasfeedatanangleof30°orso,height0mm-1.5mm,thefeedprocesswasmoststable;thedelaytimeisoneofthemainfactorswhichdeterminethepoolsize,whenthedelaytimeistooshort,itcaneasilyresultwireaccumulationonthesurfaceofthespecimen;Thevolumeofthewirefeedintothepoolisdirectlyrelatedtothesizeofcollapse.Theweldsthathavenocollapsewerereceived.Thusthestressconcentrationwerealleviated,thecrackproblemwaseffectivelyinhibited;X-raypicturesshowthatthenumberoftheporesintheweldsweresignificantlyreduced.Itwasalsofoundthatthetensileshearloadofweldsarenotonlywiththediameterofcriticalnugget,butalsowiththesizeofthecollapse,whenthecollapseislarge,itwillleadtochangeofthefracturepathandreducetensionshearcapacitysignificantly.Finally,thelaserspotweldingwithgapbetweentheplateswasstudied.Thestudyshowsthatthelargestgapthatcanbebridgedbythebasemetalisonly1.0mm,whilethisnumbercanreach2.5mmbyusingthefillerwiretobridgethe gap;Bycontrasttotheweldswhichhavenofiller,theweldswhichhavefillerhavegoodformation;Thethicknessofthemetaltobridgethegapismorelarger,sotheabilitytobridgethegapisimprovedgreatly,Moreover,thetensile-shearstrengthis60%higherormore,whichisalsoimprovedgreatly.Itcanbeconcludedthattheamountofmetalusedforgapbridgingdeterminestheabilityofgapjoiningandthestrengthofthewelds. |
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