有关挤压的英文ppt

Lecture12DifferenttypesofextrusionandtheircharacteristicsCourseHour:2Basicrequirements:Acquaintingwiththeprinciplesofdirectextrusion,indirectextrusion,hydrostaticextrusionandImpactExtrusionEmphasis:DirectextrusionDifficulties:PrinciplesofextrusionProductsbyextrusionTypesofExtrusionDirectorforwardextrusion

–Billetpushedthroughdiefrombehind–Theprocessissimilartoforcingthepastethroughtheopeningofatoothpastetube–Billetslidesrelativetothecontainerwall–ThewallfrictionincreasetheextrusionforceExtrusionsExtrusions,andexamplesofproductsmadebysectioningoffextrusions.TypesofExtrusionIndirect–Diepushedintobillet–Exceptatthedie,thereisnofrictionatthebillet-containerinterface

HydrostaticEvenmorerecentdevelopment(1950's)Advantages–Nofrictionatwalls–Cansuccessfulextrudebrittlematerials–Yieldstressreducedbyhydrostaticpressure–RoomtemperatureoperationDisadvantages–Limitedindustrialapplications–Complextooling–HighpressureexperiencerequiredTypesofExtrusionTypesofExtrusionImpactExtrusion–Similartoindirectextrusion–Canbeconsideredasubsetofcoldextrusion–Tendstolookverysimilartoforging,UsedtomakeshortpartswiththinwallsLateral–Likedirect,butmaterialcomesoutofthedieatrightanglestothedirectioninwhichthebilletispushedTypesofExtrusionConformContinuousextrusionformingFrictionisjustusefultoprocess.TypesofExtrusionLecture13ProcessvariablesandmetalflowinDirectExtrusionCourseHour:2Basicrequirements:Acquaintingwiththedependentandindependentvariablesinextrusion;graspingthefourtypesofmetalflowinextrusionEmphasis:VariablesandmetalflowtypesinextrusionDifficulties:TheeffectfactorsofthemetalflowinextrusionProcessVariablesinDirectExtrusion

Processvariablesindirectextrusion.Thedieangle,reductionincross-section,extrusionspeed,billettemperature,andlubricationallaffecttheextrusionpressureExtrusionIndependentVariablesDieangleExtrusionratio(ratioofinputtooutputcrosssectionalareasCircumscribingcirclediameterShapefactor–Ratioofperimeterofshapetocross-sectionalarea

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acircularshapehastheminimum

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AmeasureofthecomplexityoftheextrusionTemperatureofbilletRamspeedLubricantProductdesignMaterialFlowEasytoextrudemetalsandalloys–Aluminum–Copper–Magnesium–Steels–StainlesssteelsDifficulttoextrudemetalsandalloys–Titanium–RefractorymetalsMaterialFlowFourpatternsofmaterialflowinextrusionThemosthomogeneousflowpattern–Nofrictionatthebillet-container/dieinterface–Thistypeoccurswhenlubricantisveryeffective,orwithindirectextrusionAsecondpatternisobtainedwhenthereislitterornofrictionatthecontainerwall,butsomefrictionatthediesurface,Dead-metalzoneformedInthethirdpattern,thefrictionalongallinterfaceishigh,thedeadzoneincrease,billetsurfacematerialmayflowintothehighshearzoneInthefourthpattern,duetohighfrictionorhightemperaturedifferencebetweenthesurfaceandcentreofthebillet,thehighshearzoneextendsfurtherback.PipeorextrusiondefectmayoccurThemosthomogeneousflowpatternAsecondpatternthethirdpatternLecture14ExtrusionforceandhotextrusionpracticeCourseHour:2Basicrequirements:Graspingthecalculationsofextrusionforce;acquaintingwithhotextrusionpractice,advantages,disadvantages,temperatureandlubricationEmphasis:HotextrusionpracticeDifficulties:ExtrusionforcecalculationExtrusionForceInidealdeformation,Forperfectlyplasticmaterial,withayieldstressY,theenergydissipatedindeformationperunitvolumeis,Workdoneis,Theextrusionpressureattherampis,ExtrusionPractice—HotExtrusionAdvantages–Lowerstresses–Sometimestheonlywaytoextrudecertainmetals•e.g.Titanium,refractoryalloys,highstrengthalloysDisadvantages–Higherdiewear–Oxidefilmbuildupresultsinnon-uniformflow,inclusionsandpoorsurfacefinish–Coolingofbilletincontainerresultsinnon-uniform

flow