专业英语1619说课材料.docx

专业英语1619说课材料.docx

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专业英语1619说课材料

专业英语16-19

16.Couplings

Vocabulary:

coupling[]联接器

couple[]连合,连接

adjacent[]邻近的

semipermanent[]非永久性的

restore[]恢复

emergency[]紧急情况

exceptional[]异常的

plant[]工厂、车间、设备

propeller[]螺旋推进器

rigid[]刚性的

flange[]凸缘、法兰

attach[]缚上,系上

alignment[]对准、同轴

misalignment[]不对准、不同轴

rabbet[]槽口,榫头

projection[]凸出物

snugly[]紧贴地

deflect[]偏斜

interfere[]妨碍

intensity[]强度

flexibility[]挠性

shock[]冲击

spatial[]空间的

resilient[]有回弹力的

springy[]有弹性的

compensate[]补偿

Text:

Acouplingisadeviceforconnectingtheendsofadjacentshafts.Inmachineconstruction,couplingsareusedtoeffectasemipermanentconnectionbetweenadjacentrotatingshafts.Theconnectionispermanentinthesensethatitisnotmeanttobebrokenduringtheusefullifeofthemachine,butitcanbebrokenandrestoredinanemergencyorwhenwornpartsarereplaced.

Thereareseveraltypesofshaftcouplings;theircharacteristicsdependonthepurposeforwhichtheyareused.Ifanexceptionallongshaftisrequiredforalineshaftinamanufacturingplantorapropellershaftonaship,itismadeinsectionsthatarecoupledtogetherwithrigidcouplings.Acommontypeofrigidcouplingconsistsoftwomatingradialflanges（disks）thatareattachedbykey-drivenhubstotheendsofadjacentshaftsectionsandboltedtogetherthroughtheflangestoformarigidconnection.Alignmentoftheconnectedshaftsisusuallyeffectedbymeansofarabbetjointonthefaceoftheflanges,i.e.,ashortcylindricalprojectiononthefaceofoneflangefitssnuglyinacircularrecessonthefaceoftheotherflange.

Inconnectingshaftsbelongingtoseparatedevices（suchasanelectricmotorandagear-box）,precisealigningoftheshaftsisdifficultandaflexiblecouplingisused.Thiscouplingconnectstheshaftsinsuchawayastominimizetheharmfuleffectsofshaftmisalignment.Flexiblecouplingsalsopermittheshaftstodeflectundertheirseparatesystemsofloadsandtomovefreely（float）intheaxialdirectionwithoutinterferingwithoneanother.Flexiblecouplingscanalsoservetoreducetheintensityofshockloadsandvibrationstransmittedfromoneshafttoanother.

Theflexibilityprovidedbyacouplingmaybeonlyspatial,oritmaybebothspatialandresilient（springy）;inotherwordsthecouplingmaycompensateforshaftmisalignmentbutprovidenoresilience,oritmayberesilientandprovidealsoforasmallamountofmisalignment.

17.Clutches

Vocabulary:

clutch[]离合器

rotatable[]可旋转的

coaxial[]同轴的

convenient[]方便的

unload[]无负荷的

rotational[]转动的

inertia[]惯性

switch[]开关

capacity[]能力

winding[]线圈

excessive[]过多的,额外

current[]电流

intermediate[]中间的

rotor[]转子,回转轴

lineshaft[]总轴

reverse[]倒转的

Text:

Aclutchisadeviceforquicklyandeasilyconnectingordisconnectingarotatableshaftandarotatingcoaxialshaft.Clutchesareusuallyplacedbetweentheinputshafttoamachineandtheoutputshaftfromthedrivingmotor,andprovideaconvenientmeansforstartingandstoppingthemachineandpermittingthedrivermotororenginetobestartedinanunloadedstate.

Therotor（rotatingmember）inanelectricmotorhasrotationalinertia,andatorqueisrequiredtobringituptospeedwhenthemotorisstarted.Ifthemotorshaftisrigidlyconnectedtoaloadwithalargerotationalinertia,andthemotorisstartedsuddenlybyclosingaswitch,themotormaynothavesufficienttorquecapacitytobringthemotorshaftuptospeedbeforethewindingsinmotorareburnedoutbytheexcessivecurrentdemands.Aclutchbetweenthemotorandtheloadshaftswillrestrictthestartingtorqueonthemotortothatrequiredtoacceleratetherotorandpartsoftheclutchonly.

Onsomemachinetools,itisconvenienttoletthedrivingmotorruncontinuouslyandtostartandstopthemachinebyoperatingaclutch.Othermachinetoolsreceivethepowerfrombeltsdrivenbypulleysonintermediateshaftsthatarethemselvesdrivenbybeltsfromlonglineshaftsthatserveagroupofmachine.Twopulleysthatcanbeconnectedtotheintermediateshaftbyclutches,anddriveninoppositedirectionsbyopenandcrossedbeltsfromthelineshaft,canprovideforwardandreverserotationforthemachine.

Appending:

Manualtransmission

Amanualtransmissionhasagearboxfromwhichthedriverselectsspecificgearsdependingonroadspeedandengineload.Gearsareselectedwithashiftleverlocatedonthefloornexttothedriveroronthesteeringcolumn.Thedriverpressesontheclutchtodisengagethetransmissionfromtheenginetopermitachangeofgears.Theclutchdiskattachestothetransmission’sinputshaft.Itpressesagainstacircularplateattachedtotheengine’sflywheel.Whenthedriverpressesdownontheclutchpedaltoshiftgears,amechanicallevercalledaclutchforkandadevicecalledathrow-outbearingseparatethetwodisks.Releasingtheclutchpedalpressesthetwodiskstogether,transferringtorquefromtheenginetothetransmission.

18.Brakes

Vocabulary:

brake[]制动器

flow[]趋向

respect[]方面

resemble[]类似

arrest[]停止；阻止

engagement[]啮合，接合

stationary[]固定的

serve[]匹配,适合

arrest[]制动

capacity[]能力

kinetic[]（运）动的,动力（学）的

hydraulically[]液压的

electrically[]电力的

acton对...起作用,作用于

translate[]平移

dissipate[]耗尽

metallic[]金属（性）的

pneumatic[]气动的

organic[]有机的

ceramic[]陶质的

asbestos[]石棉

majority[]多数,大半

fading[]衰退

effectiveness[]效率;效能

coefficient[]系数

sinter[]烧结,熔结

lining[]衬里,内层

prefer[]首选

drum[]鼓形圆桶

thermal[]热的

conductivity[]传导性,传导率

particle[]微粒

series[]系列

plat[]片

alternate[]交替的,轮流的

pad[]衬垫

caliper[]卡钳

shoe[]闸瓦

pinch[]收缩，夹紧

Text:

Basically,brakesaredevicesforcontrollingtheflowofmotioninmachine,andinthisrespecttheyresembleclutches;clutchesstarttheflowwhilebrakesarrestit.Beforetheengagementofaclutchorabrake,oneofthetwomembersinthedeviceismovingwhiletheotherisstationary;aftertheengagementofaclutchbothmembersaremovingatthesamespeed,whileaftertheapplicationofabrakethemovingmemberiseithersloweddownorstationary.Inbothcasesthedesiredeffectsareproducedbydevicesthataresoalike,structurally,thattheycansometimesserveineithercapacity.

Inarrestingthemotionofbodies,brakesmustbecapableofabsorbingkineticenergy.Evenwhenactingontranslatingbodies（likeautomobiles）mostbrakesaredesignedtoactonrotatingmechanicalelementsandtoabsorbenergyeithermechanically,hydraulically,orelectrically.Mechanicalbrakesarethemostcommon:

theydissipatekineticenergyintheformofheatgeneratedbymechanicalfrictionbetweenarotatingmetallicelementandanonrotatingfrictionelement,whentheyarebroughtincontactbyeithermechanical,hydraulic,pneumatic,orelectricalmeans.Thematerialinthefrictionelementmaybeorganic,metallic,orceramic.Organicmaterialswithanasbestosbasesaresatisfactoryforthemajorityofapplications.Whenservicerequirementsaresevere,however,theheatgeneratedmaycause"fading"（adropinbrakingeffectivenesscausedbyareductioninthecoefficientoffriction）.Insuchcases,sinteredmetallicliningsarepreferredbecauseoftheirhighthermalconductivityandfreedomfromfading.Byaddingceramicparticlestosinteredmetalliclinings,extremelyhardandfade-resistantliningscanbeproduced.

Therotatingelementinamechanicalbrakeiseitheradrum,adisk,oraseriesofdisks.Thenonrotatingfrictionelementinadrumbrakemaybeeitherabandorapairofshoes（blocks）thatcontractaroundtheoutsideofthedrumorapairofshoesthatexpandagainsttheinsideofthedrum.Adiskbrakemaybesimilartoaplatclutch,withalternaterotatingmetallicandnonrotatingfrictionelements,oritmaybeofthecalipertype,withasinglerotatingdiskandtwoopposedfrictionpadsthatsqueezethediskbetweentheminapinchingaction.

Appending:

DiscandDrumBrakes

Discanddrumbrakescreatefrictiontoslowthewheelsofamotorvehicle.Whenadriverpressesonthebrakepedalofavehicle,brakelinesfilledwithfluidtransmittheforcetothebrakes.Inadiscbrake,thefluidpushesthebrakepadsinthecaliperagainsttherotor,slowingthewheel.Inadrumbrake,thefluidpushessmallpistonsinthebrakecylinderagainstthehingedbrakeshoes.Theshoespivotoutwardandpressagainstadrumattachedtothewheeltoslowthewheel.

19.Linkages

Vocabulary:

linkage[]联动装置

assemblage[]装配

pin[]销钉、枢轴

endless[]环形的，头尾相连的

hinge[]铰链

sliding[]滑动的

joint[]联接头

definition[]定义

vitally[]极其重要的

suitability[]恰当，适宜

relative[]相对的

specify[]具体指定

constrain[]强迫，限制

path[]轨迹，路径

determinate[]确定的

visualize[]显现

assume[]假设

compatible[]协调的

manner[]方式

Text:

Alinkagemaybedefinedasanassemblageofsolidbodies,orlinks,inwhicheachlinkisconnectedtoat