液压油理论——毕业设计外文文献翻译(中英文翻译、外文翻译)

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1、液压油理论一一毕业设计外文文献翻译（中英文翻译、外文翻译）夕卜文原文：TheoryoffluidpropertiesWewillconcentratemainlyonthreefluidpropertiesinthischapter:Thedensitywhichleadstomassandhencetohydraulicinertideffects.Theviscositywhichleadstothehydraulicfrictioneffects.Thecompressibilityandthusthebulkmoduluswhichleadstothehydraulics

2、ystemstiffness.Noticethatthecompressibilityeffectcanbemodifiedbyairrelease,cavitationphenomenaandbyexpansionofapipe,hoseorchambercontainingthehydraulicfluid.1DensityandcompressibilitycoefficientThedensityisthemassofasubstanceperunitvolume:Densityhasdimensionsof[M/L]andisexpressedinkilogramspe

3、rcubicmeter[kg/m].Asinentionedpreviouslythedensityisafunctionofthepressureandthetemperature:ThisfunctioncanbeapproximatedbythefirstthreetermsofaTaylorseries:Thiscanalsobeexpressedas:WithAndThisequationisthelinearizedstateequationforaliquid.Usingthedefinitionofthedensity,thetwocoefficientsQand

4、Bcanalsobeexpressedas:Bisknownastheisothermalbulkmodulusorforsimplicitythebulkmodulusandaisknownasthecubicalexpansioncoefficient.Sincefluiddensityvarieswiththeappliedpressure,thisimpliesthatagivenmassoffluidsubmittedtoapressurechangechangesitsvolume.Thisphenomenonleadstothedefinitionofthecomp

5、ressibilitycoefficientB:wherePisexpressedinunitsPa(orm/N).Consideringtherelationforaclosedhydrauliccircuitthemassisconstant,andhence:itfollowsthatUsingthedefinitionofthecompressibilitycoefficient0weobtain:MoreusuallyweusethebulkmodulusBalsoknownasthevolumetricelasticitymodulus:Therelationbetw

6、eenPandBimpliesmassconservation.ThisrelationmustbeRIGOROUSLYRESPECTEDinthecalculations.Inthemodelingandsimulationcontextoffluidenergysystems,disregardingtherelationbetweenPandBleadstoabnormalevolutionsofpressureintheclosedcircuitsubmittedtocompressionandexpansioncycles.Thisphenomenonisstrongl

7、yaccentuatedifaerationoccursinthecircuit(whendissolvedairinthefluidreappearsintheformofbubbles).Weshallapproachthispointbyexaminingthephenomenaofaerationandcavitation.Theaircanalsohaveadverseconsequencesonafluidcompressibility.Inliquidaircanb