材料成形力学双语课件

材料成形力学

（双语教学）MechanicsofMaterialFormingTheContentsoftheSubject1Introduction(引言)2StressAnalysis（应力分析）3StrainAnalysis（应变分析）4YieldCriteriaforDuctileMetals（塑性材料的屈服准则）5Stress-StrainRelation（应力－应变关系）6StressEvaluationApproch-SlabMethod（工程法）7PlainStrainSlip-lineFieldTheory（平面应变滑移线场理论）8ExtremumPrincipleforaRigidPerfectlyPlasticMaterial

（刚塑性材料的极限分析原理）Chapter1Introduction1)Elasticandplasticdeformation(弹性变形和塑性变形)A)ElasticdeformationForce(small)(力)StressState(应力状态)Deformation(strain)(变形或应变)Stress-Strain:linear(线性的)Deformation:recoverable（变形）

reversibleElasticdeformationTheoryofelasticity(elasticdeformedbody)(弹性理论)（弹性变形体）1.1DefinitionandscopeofthesubjectB)PlasticdeformationStress-Strain:non-linear(非线性的)Deformation:irrecoverable(不可恢复的)（变形）irreversiblePlasticdeformationTheoryofPlasticity(塑性理论)2)TheoryofPlasticity(塑性理论)Itisconcernedwiththemathematicalstudyofstressandstraininaplasticallydeformedbody.塑性理论主要考虑塑性变形体内应力－应变的数学关系。Object（研究对象）Researchmethod（研究方法）Ductilemetalmaterials(塑性金属材料)，independentoftime.ExperimentalobservationMacroscopicbehaviour.FormulizationItisdifferentfrommaterialscience.PhysicalexplanationMicroscopestructureCombineTheoryofplasticityMaterialscienceUnifiedtheoryofplasticityOurtask

3)NatureofEngineeringPlasticity(工程塑性理论的特性)Practiceandapplication（实践和应用）ToconstructrelationbetweenstressandstrainformetalsandtheiralloysTodevelopmathematicaltechnique,determinestressdistributionandpredictplasticdeformationTwoaimsFeaturesComplexstressstateNon-linearMath.difficultiesAssumptionsapproximations1864.TrescaYieldcriterion1.2BriefhistoricalaccountH.E.Trescacarriedoutexperimentsofmetalformingsuchaspunching,extrusionandcompressionusingsomemetals,andmeasuredtherelationbetweenformingloadandramdisplacement.HepresentedaseriesofpaperstotheFrenchAcademyofSciences,firstin1864.InFig.4thecross-sectionofanextrudedbilledmadeof20leadsheetsisgiven.Trescawasinterestedinthemetalflowassuggestedbythetitleofhisfirstpaper,(Ontheflowofsolidbodysubjectedtohighpressure),notyieldinginmaterialtesting.TrescaassumedthattheextrusionforcePcouldbeexpressedintermsoftheshearstressk,andestimatedthevalueofkfromthemeasuredformingloadofvariousprocesses.Becausethevaluesofshearstresskestimatedfromtheformingloadsdroppedinacertainrange,heconcludedthatthemetalflowoccurredunderaconstantmaximumshearstress.Saint-VenantandLévy1.2BriefhistoricalaccountWhenTrescapresentedhispapertotheFrenchAcademyofSciences,BarrédeSaint-Venant(1797–1886)wastheauthorityofmechanicsinFrancewhowaselectedamemberoftheAcademyin1868.AfterreadingtheexperimentalresultsofplasticflowbyTresca,hisattentionwasdrawntotheareaofplasticity.In1871,hewroteapaperonelastic-plasticanalysisofpartlyplasticproblems,suchastwistingofrod,bendingofrectangularbeamandpressurizingofhollowcylinder.Saint-Venantassumedthat(1)thevolumeofmaterialdoesnotchangeduringplasticdeformation,(2)thedirectionsofprincipalstrainscoincidewiththoseoftheprincipalstresses(nowknownastotalstraintheory),(3)themaximumshearstressateachpointisequaltoaspecificconstantinplasticregion.1.2Briefhistoricalaccount1.2BriefhistoricalaccountProgressofresearchinyieldcondition1.2Briefhistoricalaccount1.2Briefhistoricalaccount1920.PrandtlandHencky.Theoryofsliplinefield1.2BriefhistoricalaccountLudwigPrandtl（1870–1953）receivedengineeringeducationattheMunichTH.Aftergraduating,heremainedattheschoolasanassistantofA.Föppl,andcarriedoutdoctoralworkonbendingofcircularplates.Afterworkingintheindustryforawhile,hewasappointedasaprofessorofindustrialmechanicsofHannoverTHin1900.Thereheproposedmembraneanalogyoftorsionandboundarylayeroffluidflow.In1904hewasinvitedtotheInstituteofMechanicsinGöttingenUniversity.Soonhebegantostudyplasticitysuchasplasticbucklingandbending.Hewasappointedtheleaderofthelaboratoryofaerodynamics,andstudiedwingtheoremandotherimportantworksoffluiddynamics.In1922Prandtlestablishedthesocietyofappliedmathematicsandmechanics,“Gesellschaft

für

Angewandte

MathematikundMechanik”,andledtheareaofappliedmechanics.Heisalsofamousastheteacherofmanyleadersinmechanicsinthe20thcenturysuchasTh.vonKármán(CaliforniaInstituteofTechnology),S.P.Timoshenko(StanfordUniversity),A.Nádai(WestinghouseLaboratory),W.Prager(BrownUniversity)andothers.1.2Briefhistoricalaccount1.2Briefhistoricalaccount1.2Briefhistoricalaccount1.2Briefhistoricalaccount1.2Briefhistoricalaccount1925.Von-Karman.Slabmethodapplytorolling1.2Briefhistoricalaccount1.2Briefhistoricalaccount1.2BriefhistoricalaccountChapter1Introduction1)AccordingtothehomologoustemperatureTHthehomologoustemperatureTheabsolutetesttemperature(实验时的绝对温度)Theabsolutemeltingtemperature(绝对熔点温度)Hotmetalformingprocesses（热加工）Coldmetalformingprocesses（冷加工）Intermediate:Warmmetalformingprocesses（温加工）1.3Classificationofmetalformingprocesses2)AccordingtothetypeofstressstateCompressivestressstate(predominant)Squeezinggroup（压应力状态类）UpsettingClosedieforgingForging（锻造）Extrusion（挤压）ForwardBackwardPunch(冲头)Work-piece(工件)Rolling（轧制）TensilestressstateDrawinggroup（拉应力状态类）s1s2s3Drawingofsheet,tube,barandwire.Fs1s2s3Deepdrawing.s1s2s3Dendinggroup（弯曲类）Tensilestressstateononeside.Compressio