资源描述：
《液晶显示器外壳前面板设计-翻译原文》由会员上传分享，免费在线阅读，更多相关内容在工程资料-天天文库。
1、第25页共25页CHAPTER3HYDRAULICFLUIDSDuringthedesignofequipmentthatrequiresfluidpower,manyfactorsareconsideredinselectingthetypeofsystemtobeused—hydraulic,pneumatic,oracombinationofthetwo.Someofthefactorsarerequiredspeedandaccuracyofoperation,surroundingatmosphericconditions,economicconditions,availab
2、ilityofreplacementfluid,requiredpressurelevel,operatingtemperaturerange,contaminationpossibilities,costoftransmissionlines,limitationsoftheequipment,lubricity,safetytotheoperators,andexpectedservicelifeoftheequipment.Afterthetypeofsystemhasbeenselected,manyofthesesamefactorsmustbeconsideredinsel
3、ectingthefluidforthesystem.Thischapterisdevotedtohydraulicfluids.Includedinitaresectionsonthepropertiesandcharacteristicsdesiredofhydraulicfluids;typesofhydraulicfluids;hazardsandsafetyprecautionsforworkingwith,handling,anddisposingofhydraulicliquids;typesandcontrolofcontamination;andsampling.PR
4、OPERTIESIffluidity(thephysicalpropertyofasubstancethatenablesittoflow)andincompressibilityweretheonlypropertiesrequired,anyliquidnottoothickmightbeusedinahydraulicsystem.However,asatisfactoryliquidforaparticularsystemmustpossessanumberofotherproperties.Themostimportantpropertiesandsomecharacteri
5、sticsarediscussedinthefollowingparagraphs.VISCOSITYViscosityisoneofthemostimportantpropertiesofhydraulicfluids.Itisameasureofafluidsresistancetoflow.Aliquid,suchasgasoline,whichflowseasily,hasalowviscosity;andaliquid,suchastar,whichflowsslowly,hasahighviscosity.Theviscosityofaliquidisaffectedbyc
6、hangesintemperatureandpressure.Asthetemperatureofaliquidincreases,itsviscositydecreases.Thatis,aliquidflowsmoreeasilywhenitishotthanwhenitiscold.Theviscosityofaliquidincreasesasthepressureontheliquidincreases.Asatisfactoryliquidforahydraulicsystemmustbethickenoughtogiveagoodsealatpumps,motors,va
7、lves,andsoon.Thesecomponentsdependonclosefitsforcreatingandmaintainingpressure.Anyinternalleakagethroughtheseclearancesresultsinlossofpressure,instantaneouscontrol,andpumpefficiency.Leakagelossesaregreaterwiththinnerliquids(
