Engineering知識資料material知識資料and知識資料performance知識資料工程材料及其性能（Mechanical知識資料engineering知識資料material）

朽木易折，金石可鏤。千里之行，始于足下。第頁/共頁EngineeringmaterialandperformanceisacourseactuallynamedMechanicalengineeringmaterial.Inthiscourse,ittellsabouttheseveralmechanicalmaterialsuchascarbonsteel,ferrousmetalsandalloys,nonferrousmetalsandalloys,compositematerial,andceramic(陶瓷).Andalsotellsaboutthefailureanalysisofmechanicalparts,heattreatmentofthesteel.Thefailureanalysisofmechanicalpartsincludesthefailureformandthedamageofthesurface.Failureformincludesbrittle（脆性）fracture,toughness（韌性）fractureandfatiguefracture.Toughnessfracturemeansbeforethefracturethereisaobviouslyplasticdeformationbutthebrittlehavenot.Thedamageofthesurfaceincludescorrosion（腐蝕）,wear（磨損）andcontactfatigue.1．SeveralbasicconceptFailuremeansthemechanicalpartslostitsefficiencyofdesignrequirements失效：機械零件失去它的尺寸要求Deformationmeansundertheexternalforce,materialhavechanged,indimensionandshape.變形：在外力作用下材料在尺寸和形狀上的改變Stiffness(剛度)isaindextoresistancetheelasticdeformationwhenthematerialisundertheforce.剛度：材料受力時抵御塑性變形的能力。剛度系數(shù)：Strengthisaindextoresistancethedeformationandfracture.強度：材料抵御變形和斷裂的能力Hardnessisaindextotestwhetherthematerialishardorsoft.(HBWNRC)硬度：是測試材料軟硬的指標(biāo)。布氏（Brinellhardnesstest），洛氏（Rockwellhardnesstest）P:appliedforceD:diameterofindentationd:diameterofball布氏硬度實驗：Brinellhardnesstestfirstselectedtheballandtheloadthatsuitforthematerialandusedthesteelballwhichpressedintothesurfaceofthespecimenmaterial.Forhardermaterialtheloadcanbeashighasnearly30000N,forsoftercanbereducedto15000P:appliedforceD:diameterofindentationd:diameterofball洛氏硬度測試實驗：RockwellhardnesstestFirstuseainitialtestforceF0presstheindentationtothespecimen(wesetthedepthh1),andthenaddinganmaintestforceF1ontheF0andkeepitforawhile.ThenunloadtheF1,keeptheF0(wesetthedepthh3).Becausetheresultthath3minush1havethelinearrelationshipwiththeRockwellhardnessnumber.計算公式calculatednumberoftheHRis：HR=K-(h3-h1)/c=K-e/cK=100isaconstantc=0.002isaconstant應(yīng)力計算公式：三種載荷方式（Threekindsofloading）：a)compression,b)tension,c)shear2.severalfailurewaysWear，corrosion，fractureWear：Adhesivewear,abrasivewearandcorrosionweararethreeusualkindsofwear.ForexampleIusuallyputmylaptopandmobilephoneinmybags,whentheycontact,thereisfrictionhappened.Andtherehavesomeverysmallplasticparticlesbetweenthem,andthen,inthesurfaceofbothmylaptopandhandytherewillbesomeslightlyscratch,thisiscalledadhesivewear.Andabrasivewearissimilar,justtheparticlesarenotdropfromthelaptoporhandy,theycomefromtheoutside,forexamplethedustormycookies.Therearealwaysmanywaystoprotectthemechanicalpartsfromthewear.ForexampledecreasethecontactstressasIputaprotectivecaseonmyhandy,becausethecaseissoft,socanitabsorbthepowercomesfromthecontact.Corrosion：Hightemperatureoxidationcorrosion,electrochemicalcorrosionandstresscorrosionisthreeusualkindsofcorrosionfailure.Inhightemperatureoxidationcorrosionhavethechemicalreaction:themetallostitselectron…Inelectrochemicalcorrosion:（anodic…cathodic(HevolutionandOinhalation)…）Stresscorrosionisaphenomenonthatwhenthematerialunderthecombinationeffectofthedrawingstressandthespecificmediumitwillhavebrittlefracture.Thereisseveralwaystoprotectthematerialfromthecorrosion,forexampleelectrochemicalprotect(intheship,Zincsheet).Fracture：Ifthereissmalldustbetweenthetwogears,afteralongtime,therewouldbesomestarchinboththesurfaceofthegears,andthenafteralongertimethestarchwilldevelopedmoreseriouslyattheanditdevelopedtodeepcrackandintheenditmakethefractureofthegears.HeattreatmentAndanotherpartofthiscourseistalkingabouttheheattreatmentofthesteel.Thepurposeoftheheattreatmentis:1）improvethetoughness.2)improvethehardness.3)improvethewearresistance.4)refinethegrainstructure.5)removetheresidualstresses.Anneal：Means:makehardensteelsoftandremovebrittleness.Purpose:makethematerialeasiertocutorimprovedthemachinability.TemperingMeans：removedthebrittleness.hardeningMeans:makethesteelharderwithmediacooling.Forexample:inancienttimestheoldersalwaysusedthiswaytomaketheswordmore