钢材种类和变形的基础知识.ppt

BasicKnowledgeofSteelandPlasticMechanics,基础钢和塑性变形知识,2,Contents,1.SteelMechanicalpropertiesWorldwidesteelgradesAdvancedhighstrengthsteel(AHSS)2.PlasticmechanicsSheetdeformationmodesForminglimitsYieldcriteria,3,Introductiontoelasticityandplasticity,固体材料受外力作用产生变形，从变形开始到破坏一般要经历两个阶段：弹性变形(elasticdeformation)和塑性变形(plasticdeformation)。外力卸载后，弹性变形能够完全消失，而塑性变形不能消失。弹性变形和塑性变形的机理：材料原子之间的作用力平衡。位错(dislocation)理论。强化机制(workhardeningmechanism)。,Dislocationmovement,4,Uniaxialtensiletest,GB/T228金属材料室温拉伸试验方法EN10002-1Metallicmaterials-Tensiletest-Part1:testmethod(inambienttemperature),Typicaltensiletestpiece,5,Engineeringstress-straincurve,6,Engineeringstress-straincurve,7,StrengthandDuctility,Strengthparameters,Engineeringstress,Engineeringstrain,Elongation,Reductionofarea,Ductility,8,Truestress-straincurve,Truestress,Truestrain,9,Workinghardening(strainhardening),Strainhardeningexponent(n-value),10,Influenceofstrain-hardeningexponent,n3,n2,n1,11,Anisotropy(R-value),Widthstrain:w=ln(w/w0)Thicknessstrain:t=ln(t/t0)R=w/t,Planaranisotropyratio,Normalplasticanisotropyratio,12,Strainratesensitivity,Strainrate,Strainratesensitivityexponent,Strainratesensitivityhasacrucialinfluenceontheresearchofcrashresistanceandhigh-speedstampingformability.,13,Worldwidesteelgrades,14,Worldwidesteelgrades,15,CommonsteeltypesandevolvingAHSStypes,Interstitialfree(IF)steelsMildsteelsBakehardenable(BH)steelsIsotropic(IS)steelsCarbon-manganese(CM)steelsHigh-strengthlow-alloy(HSLA)steelsDualphase(DP)steelsTransformationinducedplasticity(TRIP)steelsComplexphase(CP)steelsMartensitic(Mart)steels,16,Strengtheningmechanism,17,HSLAsteel,18,GradesofHSLAsteelinEU,19,ApplicationofHSLAsteel,20,Dualphase(DP)steel,21,EUsteelgrades,ComparisonEuropeansteelgrades(Mildsteel,HSLA,Dual-Phase),Legend:ColdRolledHotRolledDualPhasecoldrolled(valuesfromARCELOR),Notfornewproducts,!:Availibilitytobeclarified,FromClausUnruh,22,Dimensionavailability,AvailabilitycheckmaterialsEuropeversusUSupdateNov2006(onlyacc.myinformation;mustbecheckedandconfirmedbyPurchasingdepartment),Materialavailibilityofstandardmaterialsisgiven.MaterialavailibilityofS460MCisdecreasingeveninEurope.MaterialavailibilityofDualPhaseandotherspecialgradesmustcheckedforeachdimensions,FromClausUnruh,23,Dimensionavailability,AvailabilitycheckmaterialsEuropeversusChinaupdateNov2006(onlyacc.myinformation;mustbecheckedandconfirmedbyPurchasingdepartment),Materialavailibilityofstandardmaterialsisgiven.MaterialavailibilityofS460MCisdecreasingevenEurope.MaterialavailibilityofDualPhaseandotherspecialgradesmustcheckedforeachdimensions,FromClausUnruh,24,StandardthicknessChinavs.Japan,China,Japan,25,HSLAsteelgradesoverview,Overviewsteelgrades:HSLA(highstrengthlowalloyed),Steelfamily,coldrolled,hotrolled,Legend:,Existinggradesafterstandardisation,UseonlystandardHSLAsteel(worldwideavailable)H240LAandS460MCwascancelledcausedbysourcingproblemsworldwide!,FromClausUnruh,26,Mildsteelgradesoverview,Overviewsteelgrades:Mildsteel,Steelfamily,coldrolled,hotrolled,Legend:,Existinggradesbeforestandardisation,Existinggradesafterstandardisation,Only2gradesareallowed:DC01/CS:softsteelforsimplelowstrengthpresspartsDC04/DDS:softsteelwithgooddeepdrawingproperties;forcomplexlowstrengthpresspartsBrandnamesandothermaterialdesignationswillnotbeaccepted.,FromClausUnruh,27,DPsteelgradesoverview,Overviewsteelgrades:Dual-Phasesteel,Steelfamily,coldrolled,hotrolled,Legend:,(*)Japanesegradesnotexactlycomparable,DP400andDP500arenotrelevantforseatstructures.DP1400indevelopment.StandardisationofDualPhasegradesisdifficult,causedbymissingEuropeanstandard.Availabilityhastobeclarifiedforeachgradeanddimension.Purchasingdepartmentmustsupporttheprocess.,FromClausUnruh,28,ProductsfromBaoSteelforautomobilestructures,Mildsteels,29,ProductsfromBaoSteelforautomobilestructures,DPsteels,Hotrolledmild&HSLAsteels,30,ProductsfromBaoSteelforautomobilestructures,ColdrolledHSLAsteels,HotrolledHSLAsteels,31,VHSScategoryatArcelor,32,MetallurgyofVHSSatArcelor,33,ApplicationofVHSS,34,ApplicationofVHSS,35,Engineeringstress-straincurveofDPsteel,HighertensilestrengthofDPsteel(largern-value)BetterstampingformabilityandcrashresistanceperformanceofDPsteel,36,n-valueofDPsteel,37,ApplicationofDPsteel,38,FEAresultsofDPsteel,39,FEAresultsofDPsteel,40,Sheetmetalformingprocesses,blanking&piercing,bending,BendinginafoldingmachineBendinginavee-dieSectionofasetofrollsinarollformerWipingdownaflange,41,Sheetmetalformingprocesses,flanging,stretching,AshrinkflangewithbucklingAstretchflangewithcrackingFlangingacurvedsheet,Sectionbending,StretchingadomeinasheetAdomedpunchanddiesetforstretchingasheet,42,Sheetmetalformingprocesses,hole-extrusion,stamping(drawing),Typicalpartformedinastampingordrawdieshowingthediering,butnotthepunchorblankholderSectionoftoolinginadrawdieshowingthepunchandblankholder,43,Sheetmetalformingprocesses,Toolingfordeepdrawingacylindricalcup,Toolingforforwardredrawingacylindricalcup,Tubeforming,ExpandingtheendofatubewithaflaringtoolReducingthediameterofatubebypressingitthroughasinkingdie,44,Sheetmetalformingprocesses,Hydroformingashallowpart,Expandingaroundtubetoasquaresectionbyhydroforming,UsingcombinedaxialforceandfluidpressuretoformaT-joint,Thinningasheetlocallyusingacoiningtool,45,Sheetmetaldeformationmodes-stretching,stretching,塑性变形局限在某一固定区域内。成形依靠材料表面积增大实现，因此变形区域材料厚度变薄。变形区域的应力状态是双向拉伸。材料不起皱，变形区域表面质量好。,Strainstatus:biaxialtension,试验方法：杯突评估指标：IE,试验方法：极限拱顶高评估指标：LDH0,46,Sheetmetaldeformationmodes-drawing,drawing(cupdrawing),坯料外部环形区域是变形区，坯料内部圆形区域不变形。在径向的应力是拉应力，在切向的应力是压应力。因此，坯料在径向可能出现破裂（拉裂），在切向可能出现起皱（压缩）。,StrainstatusRadial:tensionTangential:compression,试验方法：圆筒拉深评估指标：LDR,47,Sheetmetaldeformationmodes-bending,bending,曲率发生变化的区域是变形区。坯料圆角和直边部分参与变形，变形过程和卸载过程很复杂。卸载后零件容易发生回弹，导致达不到尺寸精度。,试验方法：V形弯曲评估指标：Rmin/t,48,Sheetmetaldeformationmodes-flanging,ShrinkflangingStretchflanging,试验方法：扩孔评估指标：,圆锥冲头平底冲头,49,Principalstrainstatusduringdeformation,drawing,planestrain,stretching,50,Forminglimits,Testprocedureofmaterialforminglimits(forminglimitcurve,FLC),Forminglimitdiagram(FLD),51,ApplicationofFLD,AnalysisofsheetmetalformingprocessbasedonFLD,52,Yieldinginplanestress,Planestress,1,20,3=0,Maximumshearstressandmaximumshearstressplanes,Thereareonshearstressesonthefacesoftheprincipalelement.Onafaceinclinedatanyotherangle,bothnormalandshearstresseswillact.Onfacesofdifferentorientationitisfoundthattheshearstresseswilllocallyreachamaxim