中英文翻译(engineering tolerance)

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1、英文：EngineeringToleranceIntroductionAsolidisdefinedbyitssurfaceboundaries.Designerstypicallyspecifyacomponent’snominaldimensionssuchthatitfulfilsitsrequirements.Inreality,componentscannotbemaderepeatedlytonominaldimensions,duetosurfaceirregularitiesandtheintri

2、nsicsurfaceroughness.Somevariabilityindimensionsmustbeallowedtoensuremanufactureispossible.However,thevariabilitypermittedmustnotbesogreatthattheperformanceoftheassembledpartsisimpaired.Theallowedvariabilityontheindividualcomponentdimensionsiscalledthetoleran

3、ce.Thetermtoleranceappliesnotonlytotheacceptablerangeofcomponentdimensionsproducedbymanufacturingtechniques,butalsototheoutputofmachinesorprocesses.Forexample,thepowerproducedbyagiventypeofinternalcombustionenginevariesfromoneenginetoanother.Inpractice,thevar

4、iabilityisusuallyfoundtobemodeledbyafrequencydistributioncurve,forexamplethenormaldistribution(alsocalledtheGaussiandistribution).Oneofthetasksofthedesigneristospecifyadimensiononacomponentandtheallowablevariabilityonthisvaluethatwillgiveacceptableperformance

5、.ComponentTolerancesControlofdimensionsisnecessaryinordertoensureassemblyandinterchangeabilityofcomponents.Tolerancesarespecifiedoncriticaldimensionsthataffectclearancesandinterferencesfits.Onemethodofspecifyingtolerancesistostatethenominaldimensionfollowedby

6、thepermissiblevariation,soadimensioncouldbestatedas40.000mm±0.003mm.Thismeansthatthedimensionshouldbemachinedsothatitisbetween39.997mmand40.003mm.Wherethe-22-variationcanvaryeithersideofthenominaldimension,thetoleranceiscalledabilateraltolerance.Foraunilatera

7、ltolerance,onetoleranceiszero,e.g.40+0.006.0.000Mostorganizationshavegeneraltolerancesthatapplytodimensionswhenanexplicitdimensionisnotspecifiedonadrawing.Formachineddimensionsageneraltolerancemaybe±0.5mm.Soadimensionspecifiedas15.0mmmayrangebetween14.5mmand1

8、5.5mm.Othergeneraltolerancescanbeappliedtofeaturessuchasangles,drilledandpunchedholes,castings，forgings,weldbeadsandfillets.Whenspecifyingatoleranceforacomponent,referencecanbemadetoprevi