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ID:2090434
大小:119.00 KB
页数:23页
时间:2017-11-14
《中英文翻译(engineering tolerance)》由会员上传分享,免费在线阅读,更多相关内容在教育资源-天天文库。
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
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