专业英语2833Word格式文档下载.docx

专业英语2833Word格式文档下载.docx

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finish[]（表面）粗糙度

deformation[]变形

internal[]内（部）的

Text:

Machiningasashape-producingmethodisthemostuniversallyusedandthemostimportantofallmanufacturingprocesses.

Machiningisashape-producingprocessinwhichapower-drivendevicecausesmaterialtoberemovedinchipform.

Mostmachiningisdonewithequipmentthatsupportsboththeworkpieceandcuttingtoolalthoughinsomecasesportableequipmentisusedwithunsupportedworkpiece.

Lowsetupcostforsmallquantities.

Machininghastwoapplicationsinmanufacturing.

Forcasting,forging,andpressworking,eachspecificshapetobeproduced,evenonepart,nearlyalwayshasahightoolingcost.

Theshapesthatmaybeproducedbyweldingdependtoalargedegreeontheshapesofrawmaterialthatareavailable.

Bymakinguseofgenerallyhighcostequipmentbutwithoutspecialtooling,itispossible,bymachining,tostartwithnearlyanyformofrawmaterial,solongastheexteriordimensionsaregreatenough,andproduceanydesiredshapefromanymaterial.

Therefore,machiningisusuallythepreferredmethodforproducingoneorafewparts,evenwhenthedesignofthepartwouldlogicallyleadtocasting,forgingorpressworkingifahighquantityweretobeproduced.

Closeaccuracies,goodfinishes.

Thesecondapplicationformachiningisbasedonthehighaccuraciesandsurfacefinishespossible.

Manyofthepartsmachinedinlowquantitieswouldbeproducedwithlowerbutacceptabletolerancesifproducedinhighquantitiesbysomeotherprocess.

Ontheotherhand,manypartsaregiventheirgeneralshapesbysomehighquantitydeformationprocessandmachinedonlyonselectedsurfaceswherehighaccuraciesareneeded.

Internalthreads,forexample,areseldomproducedbyanymeansotherthanmachiningandsmallholesinpressworkedpartsmaybemachinedfollowingthepressworkingoperations.

29.BasicMachiningVariables

adequately[]足够地

geometry[]表面形状；

几何学

appropriate[]恰当的

tough[]坚强的,坚韧的

character[]（事物的）特性,性质

express[]表达

magnitude[]大小,数量,巨大,广大

reciprocate[]往复运动

stroke[]行程

inversely[]相反地,倒转地

otherwise[]另外的,其他方面的

similar[]相似的

rectilinear[]直线的

rough[]粗糙的,粗略的,大致的

Thebasictool-workrelationshipincuttingisadequatelydescribedbymeansoffourfactors:

toolgeometry,cuttingspeed,feed,anddepthofcut.

Thecuttingtoolmustbemadeofanappropriatematerial;

itmustbestrong,tough,hard,andwearresistant.

Thetool'

sgeometry,characterizedbyplanesandangles,mustbecorrectforeachcuttingoperation.

Cuttingspeedistherateatwhichtheworksurfacepassesbythecuttingedge.

Itmaybeexpressedinfeetperminute.

Forefficientmachiningthecuttingspeedmustbeofamagnitudeappropriatetotheparticularwork-toolcombination.

Ingeneral,thehardertheworkmaterial,theslowerthespeed.

Feedistherateatwhichthecuttingtooladvancesintotheworkpiece.

Wheretheworkpieceorthetoolrotates,feedismeasuredininchesperrevolution.

Whenthetoolortheworkreciprocates,feedismeasuredininchesperstroke.

Generally,feedvariesinverselywithcuttingspeedforotherwisesimilarconditions.

Thedepthofcut,measuredinches,isthedistancethetoolissetintothework.

Itisthewidthofthechipinturningorthethicknessofthechipinarectilinearcut.

Inroughingoperations,thedepthofcutcanbelargerthanforfinishingoperations.

30.TheEffectofChangesinCuttingParametersonCuttingTemperatures

generate[]产生

primary[]第一位的,主要的

zone[]地域，区域

distribution[]散布，分步

throughout[]遍及，贯穿

typical[]典型的

isotherm[]等温线

gradient[]梯度,倾斜度,坡度

adjacent[]邻近的,接近的

virtually[]事实上,实质上

convert[]使转变,转换

rake[]angle前角

constant[]不变的,持续的

tend[]趋向,往往是

scale[]刻度，衡量，比例

proportion[]比例,均衡

parameter[]参数,参量

consequently[]从而,因此

wear[]磨损

assess[]估定,评定

accurate[]正确的,精确的

yield[]出产,生长,生产

detail[]细节,详情

metallographic[]金相学的

measurement[]测量法,度量

range[]范围

microscopy[]显微镜方法

tempering[]回火

martensitic[]马氏体的

matrix[]结构，矩阵元素

turningtool车刀

twist[]drill麻花钻

Inmetalcuttingoperations,heatisgeneratedintheprimaryandsecondlydeformationzonesandthisresultsinacomplextemperaturedistributionthroughoutthetool,workpieceandchip.

Atypicalsetofisothermsisshowninfigurewhereitcanbeseenthat,ascouldbeexpected,thereisaverylargetemperaturegradientthroughoutthewidthofthechipastheworkpiecematerialisshearedinprimarydeformationandthereisafurtherlargetemperatureinthechipadjacenttothefacesasthechipisshearedinsecondarydeformation.

Thisleadstoamaximumcuttingtemperatureashortdistanceupthefacefromthecuttingedgeandasmalldistanceintothechip.

Sincevirtuallyalltheworkdoneinmetalcuttingisconvertedintoheat,itcouldbeexpectedthatfactorswhichincreasethepowerconsumedperunitvolumeofmetalremovedwillincreasethecuttingtemperature.

Thusanincreaseintherakeangle,allotherparametersremainingconstant,willreducethepowerperunitvolumeofmetalremovedandthecuttingtemperatureswillreduce.

Whenconsideringincreaseinundeformedchipthicknessandcuttingspeed,thesituationismorecomplex.

Anincreaseinundeformedchipthicknesstendstobeascaleeffectwheretheamountsofheatwhichpasstotheworkpiece,thetoolandchipremaininfixedproportionsandthechangesincuttingtemperaturetendtobesmall.

Increaseincuttingspeed,however,reducetheamountofheatwhichpassesintotheworkpieceandthisincreasethetemperatureriseofthechipinprimarydeformation.

Further,thesecondarydeformationzonetendstobesmallerandthishastheeffectofincreasingthetemperaturesinthiszone.

Otherchangesincuttingparametershavevirtuallynoeffectonthepowerconsumedperunitvolumeofmetalremovedandconsequentlyhavevirtuallynoeffectonthecuttingtemperatures.

Sinceithasbeenshownthatevensmallchangesincuttingtemperaturehaveasignificanteffectontoolwearrate,itisappropriatetoindicatehowcuttingtemperaturescanbeassessedfromcuttingdata.

Themostdirectandaccuratemethodformeasuringtemperaturesinhigh-speed-steelcuttingtoolsisthatofWright&

Trentwhichalsoyieldsdetailedinformationontemperaturedistributionsinhigh-speed-steelcuttingtools.

Thetechniqueisbasedonthemetallographicexaminationofsectionedhigh-speed-steeltoolswhichrelatesmicrostructuralchangestothermalhistory.

Trenthasdescribedmeasurementsofcuttingtemperaturesandtemperaturedistributionsforhigh-speed-steeltoolswhenmachiningawiderangeofworkpiecematerials.

Thistechniquehasbeenfurtherdevelopedbyusingscanningelectronmicroscopytostudyfine-scalemicrostructuralchangesarisingfromovertemperingofthetemperedmartensiticmatrixofvarioushigh-speed-steels.

Thistechniquehasalsobeenusedtostudytemperaturedistributionsinbothhigh-speed-steelsinglepointturningtoolsandtwistdrills.

31.TypesofToolWear

discount[]忽视，不考虑

brittle[]易碎的,脆弱的

fracture[]破裂

flankwear后刀面磨损

minorcuttingedge副切削刃

responsible[]有责任的,负责的

bulk[]大小,大批,大多数

oversize[]超差的

abrasive[]研磨的

seizure[]卡住，捕捉

localize[]局部化

pit[]凹陷，凹坑

crater[]wear前刀面磨损、月牙洼磨损

refer[]提交,谈及,归诸于

respect[]某方面

severe[]严重的,严峻的

criterion[]标准,准据,规范

significantly[]重大地，重要地

pronounced[]显著的,断然的,明确的

introduce[]传入,引进

previous[]在前的,早先的

scale[]薄片

occasionally[]有时候,偶而

property[]特性

relatively[]相对地

notch[]wear条纹状磨损

progressive[]渐进的，前进的

eventually[]最后,终于

dramatically[]戏剧地,引人注目地

catastrophically[]悲惨的,灾难的

capable[]有能力的,能干的

scrap[]废弃

carbide[]硬质合金

onset[]开始

non-uniform[]不一致的,不均匀的

meaningful[]有意义的

Discountingbrittlefractureandedgechipping,whichhavealreadybeendealtwith,toolwearisbasicallyofthreetypes.

Flankwear,craterwear,andnotchwear.

Flankwearoccursonboththemajorandtheminorcuttingedges.

Onthemajorcuttingedge,whichisresponsibleforbulkmetalremoval,thisresultsinincreasedcuttingforcesandhighertemperatureswhichifuncheckedcanleadtovibrationofthetoolandworkpieceandaconditionwhereefficientcuttingcannolongertakeplace.

Ontheminorcuttingedge,whichdetermineswork-piecesizeandsurfacefinish,flankwearcanresultinanoversizedproductwhichhaspoorsurfacefinish.

Undermostpracticalcuttingconditions,thetoolwillfailduetomajorflankwearbeforetheminorflankwearissufficientlylargetoresultinthemanuf