資源描述：
《高輕度合金卷曲變形分析.docx》由會(huì)員上傳分享，免費(fèi)在線閱讀，更多相關(guān)內(nèi)容在教育資源-天天文庫(kù)。
1、Forminghigh-strengthmaterialsByArtHedrickJanuary31,2002Variousshapedefectscanbeencounteredinflat-rolledferrousandnonferrousstrip.Knowingtheirmechanicsandoriginsandhowtocorrectthemcanbeveryusefulintimesofneed.Figure1ObjectFabricatorsencountervariousshapedefectsinflat-rolledfer
2、rousandnonferrousstrip,somesimpleandsomecomplex.Howdothesedefectsoriginate?Whatmethodsandmachinescanfabricatorsusetocorrectthem?SimpleShapeDefectsSimpleshapedefectsarecharacterizedbylengthvariationsacrossthethicknessofthestrip.CoilSet.Coilsetisthemostbasicandcommonofallshaped
3、efects.Itiscausedbyalengthdifferentialfromthetoptobottomsurfaceofthestripinthelengthwisedirection(seeFigure1).Itcancomefromapreviousbendingoperation(forinstance,theexitpasslinerollinaslittinglineisnotoriousforputtinginreversecoilset)orjustfromcoilingthecoilinacoldmill,ahotmil
4、l,orevenonatensionlevelline.Thisconditioncanbecorrectedbyreverse-bendingthematerial,whichstretchestheshortsurfaceandcompressesthelongsurface.Forthiscorrectiontobepermanent,thematerialmustbebentpastitsyieldpoint,whichiscommonlyreferredtoasitsyielddiameter.Theyielddiameterofama
5、terialcanbecalculatedusingthefollowingformula:Dy=tE/Ywhere:Dy=yielddiameter,inchest=materialthickness,inchesE=modulusofelasticity,poundspersquareinchY=materialyieldstrength,PSIThemodulusofelasticityisabasicmaterialpropertythatdefinesitsstiffness.Ahighnumberindicatesthemateria
6、lisstiff,whilealownumberindicatesitisnot.Steelhasamodulusofelasticityofabout30,000,000PSIandisconsiderablystifferthanaluminum,whichhasamodulusofelasticityof10,000,000PSI.Figure3ObjectForexample,analuminumstripthatis1/8in.thickwitha40,000-PSIyieldstrengthmustbebenttoa31-1/4-in
7、.diametertoreachthepointatwhichanyfurtherbendingwillcausepermanentset.Ontheotherhand,a1/8-in.-thick,40,000-PSI-yield-strengthsteelstripwouldneedtobebentonlytoa93-3/4-in.diametertoreachthesameplasticpoint.Tohavethesameeffect,aluminummustbebenttoamuchtighterdiameterthansteel,wh
8、ichrequiresmoreworkandmorepower.Ifthesteelinthisexamplehada120,000-P
