MaterialsScience：involvesinvestigatingtherelationshipsthatexistbetweenthestructuresandpropertiesofmaterials(研究結(jié)構(gòu)與MaterialsEngineering:designingthestructureofamaterialtoproduceapredeterminedsetofproperties,basedonthesestructure-propertycorrelations.(根據(jù)性能要求來,設(shè)計(jì)材料結(jié)構(gòu))2.材料的四部分重要組成元素1).Structure(結(jié)構(gòu))：relatestothearrangementofitsinternal2).Property(性質(zhì))：amaterialtraitintermsofthekindandmagnitudeofresponsetoaspecificimposedstimulus.(對于外界施特別外力，材料所表現(xiàn)出的特征反應(yīng))cessingperformance四元素的關(guān)系：Thestructureofamaterialwilldependonhowitisprocessed.Amaterial’sperformancewillbeafunctionofitsproperties.3.材料的分類(按結(jié)構(gòu)分)(1)Metals(金屬)：Metallicmaterialarenormallyextremelygoodconductorsofelectricityandheatandarenottransparenttovisiblelight。csCeramicsarecompoundsbetween (3)Polymers(聚合物)：polymerareorganiccompoundsthatarechemicallybasedoncarbon,hydrogen,andothernonmetallicle (4)Composites(復(fù)合材料)：AnumberofcompositematerialsnsistofmorethanonematerialtypemechanicalProperties(機(jī)械性能)：relatedeformationtoanappliedloadorforce;examplesincludeelasticmodulusandstrength.electrical(電性能)：thestimulusisanelectricfield;electricalconductivity(電導(dǎo)率)anddielectricthermal(熱性能)：Thethermalbehaviorofsolidscanberepresentedintermsofheatcapacity(熱容)andermalconductivityofamaterialtotheapplicationofamagneticfield.optical(光學(xué)性)Thestimulusiselectromagneticorlightradiation;indexofrefraction(折射)andreflectivityures(1)晶體(crystal)：Itissolidandthearrangementofatomsinthecrystalisperiodic(周期性).(2)Threecrystalstructuresare:(FCC)Face-centeredcubic例如Cu,Al,Au,Ag(面心立方);ForFCCstructure,assignedtoagivenunitinationnumberatotaloffouratomsareAPF=volumeofatomsinaunitAPF=totalunitcellvolume33===0.74162R332UnitcelllengthaandatomicradiusRarerelatedas:EachBCCunithasatomsThecoordinationnumberis8.Atomicpackingfactoris0.68.EachHCPunithasatoms;Atomicedgelengthc=1.633aThecoordinationnumberis12.AtomicpackingfactorisSodiumChloridestructure(Rocksaltstructure)(氯化鈉結(jié)構(gòu)，食鹽結(jié)構(gòu))：coordinationnumber=6CesiumChlorideStructure(氯化銫結(jié)構(gòu))：Coordinationnumber=8ZincBlendeStructure(ZnS)(硫化鋅結(jié)構(gòu))：coordinationnumber=4n(xAc+xAA)p=pAGeneraldensityEquation：VNAdfacepositionsofthecubiccellarealloccupiedbyCarbonatoms.butthegraphitestructure石墨結(jié)構(gòu)isposedoflayersofhexagonallyarrangedcarbonatomsPolymerStructure(1)聚合物的定義：Polymerwasacompoundconsistingoflong-chainmolecules,eachmoleculemadeupofrepeatingunitsconnectedtogether.(2)聚合物的種類(按主鏈上的原子種類分)：碳鏈聚合物，機(jī)聚合物 (3)平均相對分子量umberaveragedegreeofpolymerizationgedegreeofpolymerizationMn=xxiMiMw=xwiMiMnn=nwmtDistribution Condensationpolymerizationproduct(縮聚產(chǎn)物d＝nRadicalproduct(自由基產(chǎn)物d＝3~5Side-branchd＝25~30(PE)d.03~1.05能上的特點(diǎn)softenhardensasitcools.Sowhentheparticlesstrongmaterialinsoftstatebymoldingorextrusionmolding.這種聚合物當(dāng)加熱時(shí)變軟冷卻時(shí)變硬。所以當(dāng)這heatingwillnotbesoftenedormeltedEngineeringstrain應(yīng)變):l0:originallengthbeforeanyloadappliedlitheinstantaneouslengthandl=li-l0.Engineeringstress(工程應(yīng)力)：F:theinstantaneousloadappliedperpendiculartothespecimencrosssection(N);A0:theginalcrossectionalareabeforeanyloadisappliedTruestrain表達(dá)式：trueandengineeringstressandstrainarerelatedaccordingto(真實(shí)應(yīng)力-應(yīng)變與4.ElasticDeformation(彈性變形)的概念：Whenthestressisremoved,thematerialreturnstothedimensionithadbeforetheloadwasappliedremoved,thematerialdoesnotreturntoitspreviousdimensionbutthereisapermanent,irreversibledeformation(不可回復(fù)的變形)6.Tensilestrength(拉伸強(qiáng)度)基本概念：1)thestressatthe2)correspondstothemaximumstressthatcanbesustainedbyastructureintension;ifthisstressisappliedandmaintained,fracturewillresult.tisuniformthroughoutthenarrowregionofthetensilespecimen.Yieldstrength(屈服強(qiáng)度)基本概念:thestresscorrespondingtotheintersectionoftheline,whichparallelstotheelasticportionofthestress-straincurveatsomespecifiedstrainoffset,andthestressstraincurveasitbendsoverintheplasticregion.8.Ductility(延展性)：Itisameasureofthedegreeofplasticdeformationthathasbeensustainedatfracture.Amaterialthatexperiencesverylittleornoplasticdeformationuponfractureistermedbrittle延展性可用percentelongation(延伸率)和percentreduction表示。1.金屬的(formingtechniques)成型方法：Castingandwelding鑄(1)Theductilitypropertiesofthemetal例如plasticdeformation--formingtechniquessolowinductility--cast(2)thesizeandshapeofthefinishedpiece例如solargeorcomplicatedCastingtwoormoremetalpartswelding(3)cost——Casting--mosteconomicaltiallythesurfacecoolsmorerapidlyandoncehavingdroppedtoatemperaturebelowthestrainpoint，rapidlyisatahighertemperatureabovethestrainpointandgreaterdegreethanthenowrigidexteriorwillallow.Thus，theinsidetendstodrawintheoutside，ortoimposeinwardradialstresses.Aftertheglasspiecehascooledtoroomtemperature，itsustainscompressivestressesonthesurface，withtensilestressesatregionsAcompositeisamultiphase(多相)materialthatisartificially 然地).Inaddition,theconstituent(連續(xù))phasesmustbechemicallydissimilar(不同的)andseparatedbyadistinct(明顯)interface.1.CuhasaFCCcrystalstructure,anatomicradiusof0.128nm,andanatomicweightof63.5g/mol.Compute(1)thevolumeofaunitSolution：1Thelengthofafacediagonal4R,ThecelledgelengthForFCCitisacube.So,therehasarighttriangleontheface:(2)l(2)2.Aspecimen(E=90GPa)havingarectangularcrosssection15mmnwithNforcesproducingonlyelasticdeformation.CalculatetheresultingstrainandSoeasy3.Forabronzealloy,thestressatwhichplasticdeformationbeginsis300MPa,tensilestrengthis355MPaandthemodulusofelasticityis165GPa.(a)Whatisthemaximumloadthatmaybeappliedtoaspecimenwithacross-sectionalareaof125mm2withoutplasticdeformation?(b)Iftheoriginalspecimenlengthis215mm,whatisthemaximumlengthtowhichitmaybestretchedwithoutcausingplastic Mg Mg==0.501.Apieceofcopperoriginally305mm(12in.)longispulledintensionwithastressof276MPa(40,000psi).Ifthedeformationisentirelyelasticwhatwillbetheresultantelongation?SOLUTION：Sincethedeformationiselastic,strainisdependentsaccordingto2.AssumethatthemolecularweightdistributionsshowninfigureareforPVC.Forthismaterial,compute(a)thenumber-averagemolecularweight;(b)thenumber-averagedegreeofpolymerization;and(c)theweightaveragemolecularweight.(P86)2.Onthebasisofcrystalstructure,computethetheoreticaldensitydiumchlorideP3.ItShowsthatMgOhasthesodiumchloridecrystalstructureandcalculatethedensityofMgO.olsince0.414<0.50<0.732,thecoordinationnumberforeachis,andedgeofthecu0.396nm=3.96×thesodiumchloridestr2uctureisposedgeofthecu0.396nm=3.96×5.acylindricalbrassrodthathasadiameterof10mm(0.4in.)ispulledintensionwith5600Nforce,producingonlyelasticdeformation.Calculatetheresultingstrain.SOLUTION