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電大液壓氣動(dòng)技術(shù)基礎(chǔ)期末復(fù)習(xí)題及答案參考小抄一、填空1.液壓系統(tǒng)中的兩個(gè)重要參數(shù)是(流量)和(壓力),液壓傳動(dòng)是以液體的(壓力)能傳遞動(dòng)力的。2.根據(jù)度量基準(zhǔn)的不同,液體的壓力分為(相對(duì)壓力)和(絕對(duì)壓力)兩種,大多數(shù)表測(cè)得的壓力是(相對(duì)壓力)。3.調(diào)速閥是由(定差減壓)閥和節(jié)流閥(串聯(lián))連接而組成。4.容積調(diào)速基本回路有三種,它們是(變量泵-定量馬達(dá))、(變量泵-變量馬達(dá))及(復(fù)合調(diào)速)。5.差動(dòng)回路可以實(shí)現(xiàn)油缸的(快速)運(yùn)動(dòng),但差動(dòng)連接時(shí),油缸的推力卻明顯的(降低)。二、選擇題1.運(yùn)動(dòng)速度(B)時(shí)宜采用粘度較低的液壓油減少摩擦損失:工作壓力()時(shí)宜采用粘度較高的液壓油以減少泄漏。A.高低B.高高C.低高D.低低2.在用一個(gè)泵驅(qū)動(dòng)一個(gè)執(zhí)行元件的液壓系統(tǒng)中,采用三位四通換向閥使泵卸荷,應(yīng)選用(D)型中位機(jī)能A.“P”型B.“O”型C.“Y”型D.“H”型3.限制齒輪泵工作壓力提高的主要因素是(C)。(A)存在困油現(xiàn)象(B)流量脈動(dòng)(C)泄漏(D)徑向力不平衡溢流閥的控制油壓來自閥的(A)(A)進(jìn)口端(B)出口端(C)設(shè)有單獨(dú)的泄油油路(D)沒有單獨(dú)的泄油油路5調(diào)速閥是用(B)而成的A.節(jié)流閥和順序閥串聯(lián)B.節(jié)流閥和定差減壓閥串聯(lián)C.節(jié)流閥和順序閥并聯(lián)D.節(jié)流閥和定差減壓閥并聯(lián)三、簡(jiǎn)答題1.液壓傳動(dòng)系統(tǒng)由哪幾部分組成部分?各組成部分的作用是什么?(答:液壓傳動(dòng)系統(tǒng)主要有以下五部分組成:動(dòng)力元件:液壓泵,其功能是將原動(dòng)機(jī)輸入的機(jī)械能轉(zhuǎn)換成液體的壓力能,為系統(tǒng)提供動(dòng)力。執(zhí)行元件:液壓缸、液壓馬達(dá),它們的功能是將流體的壓力能轉(zhuǎn)換成機(jī)械能,輸出力和速度(或轉(zhuǎn)矩和轉(zhuǎn)速),以帶動(dòng)負(fù)載進(jìn)行直線運(yùn)動(dòng)或旋轉(zhuǎn)運(yùn)動(dòng)。控制元件:壓力、流量和方向控制閥,它們的作用是控制和調(diào)節(jié)系統(tǒng)中液體的壓力、流量和流動(dòng)方向,以保證執(zhí)行元件達(dá)到所要求的輸出力(或力矩)、運(yùn)動(dòng)速度和運(yùn)動(dòng)方向。輔助元件:保證系統(tǒng)正常工作所需要的輔助裝置,包括管道、管接頭、油箱、過濾器和壓力計(jì)等。工作介質(zhì):用以傳遞動(dòng)力并起潤(rùn)滑作用。2.簡(jiǎn)述液壓沖擊產(chǎn)生的原因。在液壓系統(tǒng)中,由于某種原因,液體壓力在一瞬間會(huì)突然升高,產(chǎn)生很高的壓力峰值,這種現(xiàn)象稱為液壓沖擊。液壓沖擊產(chǎn)生的原因:(1)液流通道迅速關(guān)閉或液流迅速換向使液流速度的大小或方向突然變化時(shí),由于液流的慣力引起的液壓沖擊。(2)運(yùn)動(dòng)著的工作部件突然制動(dòng)或換向時(shí),因工作部件的慣性引起的液壓沖擊。(3)某些液壓元件動(dòng)作失靈或不靈敏,使系統(tǒng)壓力升高而引起的液壓沖擊。3.何謂氣穴現(xiàn)象?它有哪些危害?通常采取哪些措施防止氣穴及氣蝕?在液壓系統(tǒng)中(或液壓元件中)因局部壓力降低而有氣泡形成的現(xiàn)象稱為氣穴現(xiàn)象。危害:引起氣蝕,產(chǎn)生振動(dòng)噪聲;形成氣塞破壞系統(tǒng)正常工作。措施:盡力減少油液中空氣的含量,防止氣體混入系統(tǒng);防止系統(tǒng)局部壓力過低;在易發(fā)生氣穴部位采用耐蝕材料及保護(hù)鍍層。4.說明下圖所示雙泵雙速回路的工作原理,并分析確定閥3、4的調(diào)定壓力關(guān)系?(1)快速時(shí):低壓大流量泵2、高壓小流量泵1同時(shí)向系統(tǒng)供油;慢速時(shí):高壓小流量1向系統(tǒng)供油,低壓大流量泵2卸荷(2)閥3的調(diào)定壓力大于閥4的調(diào)定壓力四、分析題1.若把先導(dǎo)式溢流閥的遠(yuǎn)控制口當(dāng)成泄漏口接油箱,試分析液壓系統(tǒng)會(huì)產(chǎn)生什么問題產(chǎn)生卸荷現(xiàn)象,系統(tǒng)壓力近乎零。2.夾緊回路如下圖所示,若溢流閥的調(diào)整壓力p1=3Mpa、減壓閥的調(diào)整壓力p2=2Mpa。(1)試分析活塞空載運(yùn)動(dòng)時(shí)A、B兩點(diǎn)的壓力各為多少?減壓閥的閥芯處于什么狀態(tài)?(2)工件夾緊,活塞停止運(yùn)動(dòng)后,A、B兩點(diǎn)的壓力又各為多少?此時(shí),減壓閥芯又處于什么狀態(tài)?答:(1)活塞空載運(yùn)動(dòng),由于沒有負(fù)載力作用,系統(tǒng)工作壓力為0,不考慮沿程阻力損失,A、B兩點(diǎn)壓力相等,都是0MPa,此時(shí)減壓閥處在非工作狀態(tài),閥口常開(2)工件夾緊后,溢流閥工作,此時(shí)A點(diǎn)壓力為溢流閥調(diào)定壓力,3MPa,減壓閥也開始工作,B點(diǎn)壓力為2MPa,減壓閥閥芯處于半開狀態(tài),保證出口壓力恒定在2MPa。五、計(jì)算題1.圖示的簡(jiǎn)化回路中,溢流閥的調(diào)定壓力是2.5×106Pa,系統(tǒng)工作時(shí)溢流閥始終有油流回油箱,活塞有效工作面積為0.1m2,求當(dāng)負(fù)載分別為:F=2×104N;F=0;F=-5×103N時(shí),油缸出口壓力P2各為多少?解:由于溢流閥始終有油流回油箱,油缸進(jìn)油腔壓力等于溢流閥的調(diào)定壓力,為2.5×106Pa。油缸兩腔的作用力相等,則有:P2×0.1+F=2.5×106×0.1即有:P2=2.5×106+F/0.1當(dāng)F=2×104N時(shí),P2=2.7×106Pa當(dāng)F=0時(shí),P2=2.5×106Pa當(dāng)F=5×104N時(shí),P2=2.55×106Pa2.已知液壓泵轉(zhuǎn)速為1000r/min,排量為160ml/r,額定壓力為30Mpa,實(shí)際輸出流量為150L/min,泵的總效率為0.87,求:⑴泵的理論流量;⑵泵的容積效率和機(jī)械效率;⑶驅(qū)動(dòng)液壓泵所需的電動(dòng)機(jī)功率。解:1)泵的理論流量:q=n×V=1000×160=160000ml/min=160(L/min)2)泵的容積效率:ηv=q/qt=150/160=0.9375=93.75%機(jī)械效率:ηm=η/ηv=0.87/0.9375=0.928=92.8%3)驅(qū)動(dòng)液壓泵所需的電動(dòng)機(jī)功率等于液壓泵的輸入功率:P=p×qt=30×106×160×10-3=80×103(W)=80(kW)六、綜合題下圖所示回路可實(shí)行“快進(jìn)——工進(jìn)――快退――原位停止和液壓泵卸荷”的工作循環(huán),完成電磁鐵動(dòng)作順序表(通電“+”,斷電“-”)1YA2YA3YA4YA快進(jìn)+--+工進(jìn)+-++快退-+-+原位停止,泵卸荷--__七、綜合題某機(jī)床進(jìn)給回路如圖所示,它可以實(shí)現(xiàn)快進(jìn)→工進(jìn)→快退的工作循環(huán)。根據(jù)此回路工作原理,填寫電磁鐵動(dòng)作表。(電磁鐵通電時(shí),在空格中記“+”號(hào);反之,斷電記“-”號(hào))電磁鐵工作環(huán)節(jié)1YA2YA3YA快進(jìn)+-+工進(jìn)+--快退-+-
請(qǐng)您刪除一下內(nèi)容,O(∩_∩)O謝謝!??!20XX年中央電大期末復(fù)習(xí)考試小抄大全,電大期末考試必備小抄,電大考試必過小抄AfterearninghisspursinthekitchensofTheWestin,TheSheraton,SensontheBund,andasprinklingofothertop-notchvenues,SimpsonLufinallygotthechancetobecomehisownbossinNovember2010.Sortof.TheShanghai-bornchefmightnotactuallyownCaliforniaPizzaKitchen(CPK)butheisinsolechargeofbothkitchenandfrontof-houseatthisSinanMansions'stalwart.
"It’scertainlyaresponsibilitytobetheheadchef,andthentohavetomanagetherestoftherestaurantaswell,"the31-year-oldtellsEnjoyShanghai."Inhotels,forexample,thesejobsarestrictlydemarcated,soit’sagreatopportunitytolearnhowabusinessoperatesacrosstheboard."
ItwasataskthatmanagementbackinsunnyCaliforniaevidentlyfelthewasreadyfor,andavoteofconfidencefromacompanythat,todate,hasopened250outletsin11countries.Andforaddedpressure,theShanghaibranchwasalsoCPK’sChinadebut.
"Forsureitwasabigstep,andunlikealltheirotherAsiaoperationsthatarefranchises,theydecidedtomanageitdirectlytobeginwith,"saysSimpson.
Twoyearsagoaprivatefranchiseetookoverthelease,butthelinkstoCPKheadquartersarestillstrong,withamainland-based'brandambassador’onhandtoensurethebusinessadherestoitsethosofcreating"innovative,hearth-bakedpizzas",asliceofPRblurbthatSimpsoninsistslivesuptothehype.
"Theyareveryinnovative,"hesays."Theproblemwithmostfastfoodplacesisthattheyusethesamesauceoneverypizzaandjustchangethetoppings.Everyoneofour16pizzasaucesisauniquerecipethathasbeenformulatedtocomplementthetoppingsperfectly."
ThelargelylocalcustomerbaseevidentlyagreesandonSaturdayandSunday,atleast,theplaceisteeming.Thekids-eat-for-freepolicyatweekendsisundoubtedlyabigdraw,aswellasisthespacioussecond-floorlayoutoverlookedbyacanopyofgreenfromFuxingParkovertheroad.
ThecompanyisalsofocusingonincreasingbrandrecognitionandinrecentyearshastakenpartinoutsideeventssuchastheregularCaliforniaWeek.Still,thestaarehonestenoughtoadmitthatbusinesscouldbebetter;asgood,infact,asinCPK’ssecondoutletinthepopularKerryParksideshoppingmallinPudong.
"SinanMansionshasreallystruggledtogetthenumberofvisitorsthatwereenvisagedwhenitfirstopened,andithasn’tbeeneasyforanyofthetenantshere,"addsSimpson."We’replanningathirdoutletinthecityin2015,andwewillprobablychooseashoppingmallagainbecauseofthebetterfoottraffic."ThetearoomsoncefrequentedbyCocoChanelandMarcelProustareuppingsticksandcomingtoShanghai,XuJunqianvisitstheParisianoutpostwithsweettreats.Onethingthecentury-oldParisiantearoomAngelinahasshownisthatlegendaryfashiondesignerCocoChanelnotonlyhadstyleandglamorbutalsoboastedgreattasteinfood,pastriesinparticular.OneofthemostpopulartearoomsinParis,AngelinaisfamousforhavingoncebeenfrequentedbycelebritiessuchasChanelandwriterMarcelProust.NowAngelinahaspackedupitsFrenchambience,efficientservice,andbeautiful,comfortingdessertsandflownthemtoShanghai.Attheflagshipdine-inandtake-outspaceinShanghai,everythingmimicstheoriginaltearoomdesignedfromthebeginningofthe20thcentury,inParis,theheightof"BelleEpoque".Thepaintingsonthewall,forexample,areexactlythesameastheonethatdepictsthelandscapeofsouthernFrance,thehometownoftheowner;andthesmalltablesareintentionalimitationsoftheonesthatCocoChaneloncesatateveryafternoonforhotchocolate.Thefamoushotchocolate,knownasL’Africain,isaluxuriousmixtureoffourtypesofcocoabeansimportedfromAfrica,blendedinParisandthenshippedtoShanghai.It’ssinfullysweet,richandthickasifputtingabarofmeltingchocolatedirectlyonthetongueandthefreshwhippedcreamonthesidemakesalight,butequallygratifyingcontrast.Itisalsosoldinglassbottlesastakeaway.ThesignatureMont-Blancchestnutcakeconsistsofthreeparts:thepureedchestnutontop,thevanillacreamlikestuffing,andthemeringueasbase.Getallthreelayersinonescoop,notonlyforthedifferenttexturesbutalsovariousflavorsofsweetness.Thedesserthasmaintaineditspopularityforacentury,eveninacountrylikeFrance,perhapstheworld’smostcompetitiveplacefordesserts.Amuchoverlookedpairing,istheParis-NewYorkchouxpastryandN226chocolateflavoredtea.Thechouxpastryisamouthfulofairypecan-flavoredwhippedcream,whilethetea,ablendofblackteasfromChinaandCeylon,cocoaandrosepetals,offersamoresubtlefragranceofflowersandchocolate.Orderingthesetwoitems,featuringamutedsweetness,makesiteasierforyoutofitintoyourlittleblackdress.Breakfast,brunch,lunchandlightsupperarealsoservedatthetearoom,"ahubofmanycultures"andtakesin"amixofdifferentstylesofFrenchcuisines",accordingtothemanagementteam.Thesemi-cookedfoiegrasterrine,isseductiveanddeceptive.It’sgenerouslyservedatthesizeandshapeofatoast,whiletheactualbriochetoastisbakedintoacurvedslicedippedwithfigchutney.Theflavor,however,ishonest:strong,smoothandsublime.Andyoudon’tactuallyneedthetoastforcrunchiness.Thisistheseasonforhighteas,withdaintycupsoffinechinaandlittlepastriesthatappealtobothvisualandphysicalappetites.Butthereisonehighteawithadifference,andPaulineD.Lohfindsoutjustexactlywhyitisspecial.EarlGreyteaandmacaronsareallverywellforthecrucialrecuperativebreakin-betweenintensiveboutsofholidayseasonshopping.Andforthosewhoprefersavorytosweet,thereisstilltheselectionofclassicChinesesnackscalleddimsumtosatisfyandsatiate.Highteaisamealtoeatwitheyeandmouth,anin-betweenindulgencethatshouldbelightenoughnottospoildinner,butsufficientlyrobusttotaketheedgeoffthehungerthatstrikeshoursafterlunch.TheafternoonteaspecialatShang-XiattheFourSeasonsHotelPudonghasjusttherightelements.Itisapamperingmeal,withtouchesofluxurythatmakethehighteasessionatreatinitself.Wholebabyabalonesarebraisedandthentoppedonashortcrustpastryshell,asortofChineseversionoftheWesternvol-au-vent,butclassier.Evenclassieristhedimsumstapleshrimpdumplingorhargow,upgradedwiththeadditionofsliversofmidnightdarktruffles.Thisisamastertouch,andchefSimonChoi,whopresidesunchallengedatShang-Xi,hasscoredawinneragain.Sweetprawnsandaromatictruffles—what’snottolove?Hismasterfulcraftsmanshipisexhibitedinyetanotherpastry—asweetpastrythatisshapedtolooklikeawalnut,butwhichyoucanputstraightintothemouth.Itcrumblesimmediately,andtheslightlysweet,nuttymorselissoeasytoeatyou’llprobablyreachstraightforanother.Myfavoriteisthedessertthatgoesbythenameyangzhiganlu,orambrosiafromthegods.Thehotelcallsitchilledmangocreamwithsago,pomeloandbird’snest–madewithingredientsthatresonatewitheveryfemalesoul.Itdoestastelikeambrosia,withthesweet-sourfragranceofthemangoformingthefirstlayeroftasteandsensation,andthepomelosacsandsagopearlsprovidingthetactilecontrast.Thebi
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