吉大材料考研课件全英语版chapter

Chapter7

MechanicalProperties

第七章力学性质吉林大学材料科学与工程学院曹占义2023/2/21Chapter7MechanicalProperties2Mechanicalproperties:Themechanicalbehaviorofamaterialreflectstherelationshipbetweenitsresponseordeformationtoanappliedloadorforce.Importantmechanicalproperties:strength,hardness,ductility,stiffness.7.1INTRODUCTION力学性质强度硬度延性韧性2023/2/21Chapter7MechanicalProperties3Waysthatloadapplied:Tension,CompressionSheartorsion7.2CONCEPTSOFSTRESSANDSTRAIN拉伸载荷压缩载荷剪切载荷扭转载荷2023/2/21Chapter7MechanicalProperties4TENSIONTESTS:7.2CONCEPTSOFSTRESSANDSTRAIN2023/2/21Chapter7MechanicalProperties5COMPRESSIONTESTS:SHEARANDTORSIONALTESTS:7.2CONCEPTSOFSTRESSANDSTRAIN2023/2/21Chapter7MechanicalProperties6GEOMETRICCONSIDERATIONSOFTHESTRESSSTATE:7.2CONCEPTSOFSTRESSANDSTRAIN2023/2/21Chapter7MechanicalProperties7Stress–straindiagramandmodulusofelasticity:7.3STRESS–STRAINBEHAVIOR2023/2/21Chapter7MechanicalProperties8Forceversusinteratomicseparationtoexplaintheelasticdeformation:7.3STRESS–STRAINBEHAVIOR2023/2/21Chapter7MechanicalProperties9Elasticmodulusdependsonatomicbonding:7.3STRESS–STRAINBEHAVIOR2023/2/21Chapter7MechanicalProperties10Shearstressandstrain7.3STRESS–STRAINBEHAVIORAND7.4ANELASTICITY7.4ANELASTICITYAnelasticdeformation:

Time-dependentelastic(nonpermanent)deformation.滞弹性2023/2/21Chapter7MechanicalProperties11Poisson’sratio7.5ELASTICPROPERTIESOFMATERIALS2023/2/21Chapter7MechanicalProperties127.6TENSILEPROPERTIESYIELDINGANDYIELDSTRENGTH2023/2/21Chapter7MechanicalProperties137.6TENSILEPROPERTIESTENSILESTRENGTH2023/2/21Chapter7MechanicalProperties147.6TENSILEPROPERTIESDUCTILITY塑性,延展性2023/2/21Chapter7MechanicalProperties157.6TENSILEPROPERTIESMechanicalbehaviorforironatthreetemperatures.2023/2/21Chapter7MechanicalProperties167.6TENSILEPROPERTIESRESILIENCE塑性,延展性弹性能,应变能2023/2/21Chapter7MechanicalProperties177.6TENSILEPROPERTIESTOUGHNESS韧性Forstaticsituation:theareabelowthecurveof-Fordynamic(highstrainrate)situation:notchtoughnessfracturetoughnessFordynamic(highstrainrate)situation:notchtoughness缺口冲击韧性fracturetoughnessFordynamic(highstrainrate)situation:notchtoughness缺口冲击韧性fracturetoughness断裂韧性2023/2/21Chapter7MechanicalProperties187.7TRUESTRESSANDSTRAINTrueStressT真实应力TrueStrainT真实应力和工程应力的关系真实应变和工程应变的关系2023/2/21Chapter7MechanicalProperties197.7TRUESTRESSANDSTRAINTrueStressT真实应力2023/2/21Chapter7MechanicalProperties207.7TRUESTRESSANDSTRAINTrueStressT真实应力2023/2/21Chapter7MechanicalProperties217.8ELASTICRECOVERYDURINGPLASTICDEFORMATIONUnloadingcycles2023/2/21Chapter7MechanicalProperties227.9COMPRESSIVE,SHEAR,ANDTORSIONALDEFORMATIONCOMPRESSIVEDEFORMATION,SHEARDEFORMATION,TORSIONALDEFORMATION压缩变形剪切变形扭转变形2023/2/21Chapter7MechanicalProperties23MECHANICALBEHAVIOR—CERAMICS

7.10FLEXURALSTRENGTH(陶瓷材料的)抗弯强度2023/2/21Chapter7MechanicalProperties24MECHANICALBEHAVIOR—CERAMICS

7.11ELASTICBEHAVIOR(陶瓷材料的)弹性行为2023/2/21Chapter7MechanicalProperties25MECHANICALBEHAVIOR—POLYMERS7.13STRESS–STRAINBEHAVIOR(高分子材料的)应力_应变行为脆性高分子材料塑性高分子材料完全弹性高分子材料完全弹性体,人造橡胶2023/2/21Chapter7MechanicalProperties26MECHANICALBEHAVIOR—POLYMERS7.13STRESS–STRAINBEHAVIORThemechanicalcharacteristicsofpolymers,forthemostpart,arehighlysensitivetotherateofdeformation(strainrate),thetemperature,andthechemicalnatureoftheenvironment(thepresenceofwater,oxygen,organicsolvents,etc.).2023/2/21Chapter7MechanicalProperties27MECHANICALBEHAVIOR—POLYMERS7.13STRESS–STRAINBEHAVIOR(高分子材料的)应力_应变行为屈服强度抗张强度2023/2/21Chapter7MechanicalProperties28MECHANICALBEHAVIOR—POLYMERS7.13STRESS–STRAINBEHAVIORThemechanicalcharacteristicsofpolymers,forthemostpart,arehighlysensitivetotherateofdeformation(strainrate),thetemperature,andthechemicalnatureoftheenvironment(thepresenceofwater,oxygen,organicsolvents,etc.).材料:polymethylmethacrylate聚甲基丙烯酸甲酯Ingeneral,decreasingtherateofdeformationhasthesameinfluenceonthestress–straincharacteristicsasincreasingthetemperature;thatis,thematerialessofterandmoreductile.2023/2/21Chapter7MechanicalProperties29MECHANICALBEHAVIOR—POLYMERS7.14MACROSCOPICDEFORMATION(高分子材料的)宏观变形7.15VISCOELASTICITY粘弹性(高分子材料的特性)2023/2/21Chapter7MechanicalProperties30HARDNESSANDOTHERMECHANICAL

PROPERTYCONSIDERATIONS7.16HARDNESSHardness.Themeasureofamaterial’sresistancetodeformationbysurfaceindentationorbyabrasion.硬度Mohsscale,whichrangedfrom1onthesoftendfortalcto10(onthehardend)fordiamond.Measuredhardnessesareonlyrelative!ThereasonsthatHardnesstestsareperformed:1.Theyaresimpleandinexpensive.2.Thetestisnondestructive.3.Othermechanicalpropertiesoftenmaybeestimatedfromhardnessdata.2023/2/21Chapter7MechanicalProperties31HARDNESSANDOTHERMECHANICAL

PROPERTYCONSIDERATIONS硬度测量技术Measuredhardnessesareonlyrelative!2023/2/21Chapter7MechanicalProperties32HARDNESSANDOTHERMECHANICAL

PROPERTYCONSIDERATIONS硬度换算Measuredhardnessesareonlyrelative!2023/2/21Chapter7MechanicalProperties33HARDNESSANDOTHERMECHANICAL

PROPERTYCONSIDERATIONS硬度与强度的关系Measuredhardnessesareonlyrelative!CORRELATIONBETWEENHARDNESSANDTENSILESTRENGTH2023/2/21Chapter7MechanicalProperties34HARDNESSANDOTHERMECHANICAL

PROPERTYCONSIDERATIONS硬度与抗拉强度的关系Measuredhardnessesareonlyrelative!CORRELATIONBETWEENHARDNESSANDTENSILESTRENGTH2023/2/21Chapter7MechanicalProperties35HARDNESSANDOTHERMECHANICAL

PROPERTYCONSIDERATIONS陶瓷材料的硬度Measuredhardnessesareonlyrelative!7.17HARDNESSOFCERAMICMATERIALS2023/2/21Chapter7MechanicalProperties36HARDNESSANDOTHERMECHANICAL

PROPERTYCONSIDERATIONS高分子材料的撕裂强度和硬度Tearstrength,themechanicalparameterthatismeasured,istheenergyrequiredtotearapartacutspecimenthathasastandardgeometry.7.18TEARSTRENGTHANDHARDNESSOFPOLYMERSPolymersaresofterthanmetalsandceramics,andmosthardnesstestsareconductedbypenetrationtechniquessimilartothosedescribedformetalsintheprevioussection.Rockwelltestsarefrequentlyusedforpolymers.2023/2/21Chapter7MechanicalProperties37PROPERTYVARIABILITYAND

DESIGN/SAFETYFACTORS材料性能的可变性(数据分散性)ScatterandVariabilityofmaterialspropertiesareinevitableandmustbedealtwithappropriately.7.19VARIABILITYOFMATERIALPROPERTIESQuestion1:‘‘Whatisthefracturestrengthofthisalloy?’’Question2:‘‘Whatistheprobabilityoffailureofthisalloyunderthesegivencircumstances?’’COMPUTATIONOFAVERAGEANDSTANDARDD