机械工程专业英语课件--L05.ppt

EnglishforMechanicalEngineering,机械工程专业英语,机械工程专业英语,预备知识,一、BackgroundInformation,MetalMaterials(金属材料),Therearemanydifferentmaterialtypestochoosefromwhenundertakingaproject.Inmatierialscience,thematerialsaregroupedroughlyintotwocategories,thesebeingNon-metallicandMetallic.Inrespecttometallicmaterialsthesearethensubsequentlygroupedintotwogroupsbeingferrousandnon-ferrous.Eachofthematerialshastheirowncharacteristicsandrequiresdifferentmachiningtechniques.Carefulconsiderationneedstobegiventothecorrectmaterialselectionforitsapplication.(Definition:FerrousasincontainingIron,e.gsteel-Non-ferrousasinnotcontainingIrone.galuminium,copper)Asimpletestforferrous/non-ferrousmaterialsistousemagnetasamagnetwillsicktoferrousmaterialsduetoitsironcontent.,Lesson5MetallicandNonmetallicMaterials,机械工程专业英语,预备知识,一、BackgroundInformation,AluminiumAlloy,TherearemanykindsofAlloystochoosefrombutoften,Aluminiumischosenasitislightweight(about2700kg/m3density),itiscomparativelysoftanditsprocess-abilityisgood.FromamachiningviewpointpurealuminiumgreatlydiffersfromAl-Cualloy。Purealuminiumiseasytobendbutitisdifficulttoprocessasitistoosoftandeasilyclogscuttingtools.Ontheotherhand,theAl-Cualloyiseasytohandleandcutwithseveralofthegradeshavingstrengthsimilartothatofsteel.However,oneofthedrawbacksofaluminiumisthatitisdifficulttoweld,solderandbend.,Lesson5MetallicandNonmetallicMaterials,机械工程专业英语,预备知识,一、BackgroundInformation,CarbonSteel,Typicalcarbonsteelmaterialsareverycheap,excellinginweldability,andtheycanbesubjectedtovariousheattreatments.Sincemanymachinetoolsaredesignedtocutmildsteelmaterial,itisveryraretoencounterproblemswhilemachining.Generally,mildsteelhasablacksurfaceandthissurfaceisveryhard,ifpossible,thissurfaceshouldbeleftintactasitoffersadditionalprotection.,Lesson5MetallicandNonmetallicMaterials,机械工程专业英语,预备知识,一、BackgroundInformation,CommonShapes,Materialisusuallysuppliedascommonshapesandtheseare(a)Billets(columns),(b)flatbar(boards),(c)Angle(L-shaped),(d)Cchannel(C-shaped)and(e)pipe.Thecorrectselectionofmaterialassistsinsimplifyingaproject.,Lesson5MetallicandNonmetallicMaterials,机械工程专业英语,预备知识,一、BackgroundInformation,Non-metal,Lesson5MetallicandNonmetallicMaterials,Thereisnorigorousdefinitionforthetermnonmetal-itcoversageneralspectrumofbehaviour.Commonpropertiesconsideredcharacteristicofanonmetalinclude:poorconductorsofheatandelectricitywhencomparedtometalstheyformacidicoxides(whereasmetalsgenerallyformbasicoxides)insolidform,theyaredullandbrittle,ratherthanmetalswhicharelustrous,ductileormalleableusuallyhavelowerdensitiesthanmetalstheyhavesignificantlylowermetalingpointandboilingpointsthanmetalsnon-metalshavehighelectronegativity,mlibladj.可锻造的,有延展性的，韧性的,Lesson5MetallicandNonmetallicMaterials,机械工程专业英语,stress应力strain应变density密度strength强度hardness硬度rigidity刚度elasticity弹性plasticity（ductility）塑性toughness韧性compression压缩tension拉伸bend弯曲torsion扭转shear剪切fatigue疲劳deformationn.变形metalformingprocessn.金属成型工艺（过程),词汇,机械工程专业英语,课文分析,Perhapsthemostcommonclassificationthatisencounteredinmaterialsselectioniswhetherthematerialismetallicornonmetallic.Thecommonmetallicaresuchmetalsasiron,copper,aluminum,magnesium,nickel,titanium,lead,tin,andzincandthealloysofthesemetals,suchassteel,brass,andbronze.Theypossessthemetallicpropertiesofluster,thermalconductivity,andelectricalconductivity;arerelativelyductile;andsomehavegoodmagneticproperties.Thecommonnonmetalsarewood,brick,concrete,glass,rubber,andplastics.Theirpropertiesvarywidely,buttheygenerallytendtobelessductile,andlessdensethanthemetals,andtheyhavenoelectricalconductivityandpoorthermalconductivity.,Lesson5MetallicandNonmetallicMaterials,机械工程专业英语,课文分析,Perhapsthemostcommonclassificationthatisencounteredinmaterialsselectioniswhetherthematerialismetallicornonmetallic.,Thecommonmetallicmaterialsaresuchmetalsasiron,copper,aluminum,magnesium,nickel,titanium,lead,tin,andzincandthealloysofthesemetals,suchassteel,brass,andbronze.,在材料选择时所遇到的最普通的分类问题，可能就是这种材料是金属材料还是非金属材料。,最常见的金属材料如铁，铜，铝，镁，镍，钛，铅，锡和锌以及这些金属的合金，例如钢，黄铜和青铜。,mni:zjmn.镁,taiteinimn.钛,Lesson5MetallicandNonmetallicMaterials,机械工程专业英语,课文分析,Theypossessthemetallicpropertiesofluster,thermalconductivity,andelectricalconductivity;arerelativelyductile;andsomehavegoodmagneticproperties.,他们具有金属特性：光泽，导热性和导电性，一定的延展性，而某些金属还具有良好的磁性。,Lesson5MetallicandNonmetallicMaterials,机械工程专业英语,课文分析,Thecommonnonmetalsarewood,brick,concrete,glass,rubber,andplastics.,常用非金属材料有木头，砖，混泥土，玻璃，橡胶和塑料。,Theirpropertiesvarywidely,buttheygenerallytendtobelessductile,andlessdensethanthemetals,andtheyhavenoelectricalconductivityandpoorthermalconductivity.,他们的性能变化很大，但它们通常几乎没有延展性，比金属疏松，而且它们不具有导电性以及有较差的导热性。,Lesson5MetallicandNonmetallicMaterials,机械工程专业英语,课文分析,Althoughitislikelythatmetalsalwayswillbethemoreimportantofthetwogroups,therelativeimportanceofthenonmetallicgroupisincreasingrapidly,andsincenewnonmetalsarebeingcreatedalmostcontinuously,thistrendiscertaintocontinue.Inmanycasestheselectionbetweenametalandnonmetalisdeterminedbyaconsiderationofrequiredproperties.Wheretherequiredpropertiesareavailableinboth,totalcostbecomesthedeterminingfactor.,Lesson5MetallicandNonmetallicMaterials,机械工程专业英语,课文分析,Althoughitislikelythatmetalsalwayswillbethemoreimportantofthetwogroups,therelativeimportanceofthenonmetallicgroupisincreasingrapidly,andsincenewnonmetalsarebeingcreatedalmostcontinuously,thistrendiscertaintocontinue.,虽然两大类材料中，金属材料可能总是更加重要，但非金属材料的相对重要性在迅速增强，由于新的非金属材料几乎是在不断地产生，并且这一趋势将确定无疑地继续下去。,Lesson5MetallicandNonmetallicMaterials,机械工程专业英语,课文分析,Inmanycasestheselectionbetweenametalandnonmetalisdeterminedbyaconsiderationofrequiredproperties.,许多情况下选择金属材料还是非金属，是考虑所需要材料的性能来确定的。,Wheretherequiredpropertiesareavailableinboth,totalcostbecomesthedeterminingfactor.,两种材料的性能都能满足需要的时候，总成本就成了决定性的因素。,Lesson5MetallicandNonmetallicMaterials,机械工程专业英语,课文分析,Onematerialcanoftenbedistinguishedfromanotherbymeansofphysicalproperties,suchascolor,density,specificheat,coefficientofthermalexpansion,thermalandelectricalconductivity,magneticproperties,andmeltingpoint.Someofthese,forexamplethermalconductivity,electricalconductivity,anddensity,maybeofprimeimportanceinselectingmaterialforcertainspecificuses.Thosepropertiesthatdescribehowamaterialreactstomechanicalusage,however,areoftenmoreimportanttotheengineerinselectingmaterialsinconnectionwithdesign.Thesemechanicalpropertiesrelatetohowthematerialwillreacttothevariousloadingduringservice.,Lesson5MetallicandNonmetallicMaterials,机械工程专业英语,课文分析,Onematerialcanoftenbedistinguishedfromanotherbymeansofphysicalproperties,suchascolor,density,specificheat,coefficientofthermalexpansion,thermalandelectricalconductivity,magneticproperties,andmeltingpoint.,通常借助于物理性质来区别一种材料和另一种材料，例如颜色、密度、比热、热膨胀系数、导热性、导电性、磁性和熔点。,不同于;与加以区别,kuifintn.系数,率,程度;,Lesson5MetallicandNonmetallicMaterials,机械工程专业英语,课文分析,Someofthese,forexamplethermalconductivity,electricalconductivity,anddensity,maybeofprimeimportanceinselectingmaterialforcertainspecificuses.,有些性能，象导热性、导电性和磁性，对于某些特定场合来说，在选择材料时可能是极其重要的。,Lesson5MetallicandNonmetallicMaterials,机械工程专业英语,课文分析,Thosepropertiesthatdescribehowamaterialreactstomechanicalusage,however,areoftenmoreimportanttotheengineerinselectingmaterialsinconnectionwithdesign.,Thesemechanicalpropertiesrelatetohowthematerialwillreacttothevariousloadingduringservice.,描述一种材料在机械应用中表现出的性能，对于工程师在设计中选择材料来说，往往更为重要。,这些机械性能关系到材料在实际应用中对于各种载荷的反应。,Lesson5MetallicandNonmetallicMaterials,机械工程专业英语,课文分析,Mechanicalpropertiesarethecharacteristicresponsesofamaterialtoappliedforces.,Thesepropertiesfallintofivebroadcategories:strength,hardness,elasticity,ductility,andtoughness.,机械性能是材料对所施加的作用力的特性反应。,这些性能主要分为五大类：强度、硬度、弹性、塑性和韧性。,ilstisitin.弹力,弹性,Lesson5MetallicandNonmetallicMaterials,机械工程专业英语,课文分析,1.Strengthistheabilityofamaterialtoresistappliedforces.Elevatorcablesandbuildingbeamsallmusthavethisproperty.,2.Hardnessistheabilityofamaterialtoresistpenetrationandabrasion.Cuttingtoo