机械工程专业英语课件--L05

EnglishechanicalEngineering 机械工程专业英语 机械工程专业英语 预备知识 一 BackgroundInation MetalMaterials 金属材料 Therearemanydifferentmaterialtypestochoosefromwhenundertakingaproject Inmatierialscience thematerialsaregroupedroughlyintotwocategories thesebeing Non metallic andMetallic 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 BackgroundInation 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 BackgroundInation CarbonSteel Typicalcarbonsteelmaterialsareverycheap excellinginweldability andtheycanbesubjectedtovariousheattreatments Sincemanymachinetoolsaredesignedtocutmildsteelmaterial itisveryraretoencounterproblemswhilemachining Generally mildsteelhasablacksurfaceandthissurfaceisveryhard ifpossible thissurfaceshouldbeleftintactasitoffersadditionalprotection Lesson5MetallicandNonmetallicMaterials 机械工程专业英语 预备知识 一 BackgroundInation CommonShapes Materialisusuallysuppliedascommonshapesandtheseare a Billets columns b flatbar boards c Angle L shaped d C channel C shaped and e pipe Thecorrectselectionofmaterialassistsinsimplifyingaproject Lesson5MetallicandNonmetallicMaterials 机械工程专业英语 预备知识 一 BackgroundInation Non metal Lesson5MetallicandNonmetallicMaterials Thereisnorigorousdefinitionfortheterm nonmetal itcoversageneralspectrumofbehaviour Commonpropertiesconsideredcharacteristicofanonmetalinclude poorconductorsofheatandelectricitywhencomparedtometalstheyacidicoxides whereasmetalsgenerallybasicoxides insolid theyaredullandbrittle ratherthanmetalswhicharelustrous ductileormalleableusuallyhavelowerdensitiesthanmetalstheyhavesignificantlylowermetalingpointandboilingpointsthanmetalsnon metalshavehighelectronegativity m li bl adj 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deationn 变形metalingprocessn 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 m ni zj m n 镁 tai teini m n 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 totalcostbecomest