電大液壓氣動技術基礎期末復習題及答案參考電大考試

電大液壓氣動技術基礎期末復習題及答案參考小抄一、填空1．液壓系統中的兩個重要參數是(流量)和(壓力)，液壓傳動是以液體的(壓力)能傳遞動力的。2．根據度量基準的不同，液體的壓力分為(相對壓力)和(絕對壓力)兩種，大多數表測得的壓力是(相對壓力)。3．調速閥是由(定差減壓)閥和節(jié)流閥(串聯)連接而組成。4．容積調速基本回路有三種，它們是(變量泵-定量馬達)、(變量泵-變量馬達)及(復合調速)。5．差動回路可以實現油缸的(快速)運動，但差動連接時，油缸的推力卻明顯的(降低)。二、選擇題1．運動速度（B）時宜采用粘度較低的液壓油減少摩擦損失：工作壓力（）時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.在用一個泵驅動一個執(zhí)行元件的液壓系統中，采用三位四通換向閥使泵卸荷，應選用（D）型中位機能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)存在困油現象(B)流量脈動(C)泄漏(D)徑向力不平衡溢流閥的控制油壓來自閥的(A)(A)進口端(B)出口端(C)設有單獨的泄油油路(D)沒有單獨的泄油油路5調速閥是用（B）而成的A.節(jié)流閥和順序閥串聯B.節(jié)流閥和定差減壓閥串聯C.節(jié)流閥和順序閥并聯D.節(jié)流閥和定差減壓閥并聯三、簡答題1.液壓傳動系統由哪幾部分組成部分?各組成部分的作用是什么?（答：液壓傳動系統主要有以下五部分組成：動力元件：液壓泵，其功能是將原動機輸入的機械能轉換成液體的壓力能，為系統提供動力。執(zhí)行元件：液壓缸、液壓馬達，它們的功能是將流體的壓力能轉換成機械能，輸出力和速度（或轉矩和轉速），以帶動負載進行直線運動或旋轉運動。控制元件：壓力、流量和方向控制閥，它們的作用是控制和調節(jié)系統中液體的壓力、流量和流動方向，以保證執(zhí)行元件達到所要求的輸出力（或力矩）、運動速度和運動方向。輔助元件：保證系統正常工作所需要的輔助裝置，包括管道、管接頭、油箱、過濾器和壓力計等。工作介質：用以傳遞動力并起潤滑作用。2．簡述液壓沖擊產生的原因。在液壓系統中，由于某種原因，液體壓力在一瞬間會突然升高，產生很高的壓力峰值，這種現象稱為液壓沖擊。液壓沖擊產生的原因：（1）液流通道迅速關閉或液流迅速換向使液流速度的大小或方向突然變化時，由于液流的慣力引起的液壓沖擊。（2）運動著的工作部件突然制動或換向時，因工作部件的慣性引起的液壓沖擊。（3）某些液壓元件動作失靈或不靈敏，使系統壓力升高而引起的液壓沖擊。3．何謂氣穴現象？它有哪些危害？通常采取哪些措施防止氣穴及氣蝕？在液壓系統中（或液壓元件中）因局部壓力降低而有氣泡形成的現象稱為氣穴現象。危害：引起氣蝕，產生振動噪聲；形成氣塞破壞系統正常工作。措施：盡力減少油液中空氣的含量，防止氣體混入系統；防止系統局部壓力過低；在易發(fā)生氣穴部位采用耐蝕材料及保護鍍層。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的調定壓力關系？（1）快速時：低壓大流量泵2、高壓小流量泵1同時向系統供油；慢速時：高壓小流量1向系統供油，低壓大流量泵2卸荷（2）閥3的調定壓力大于閥4的調定壓力四、分析題1.若把先導式溢流閥的遠控制口當成泄漏口接油箱，試分析液壓系統會產生什么問題產生卸荷現象，系統壓力近乎零。2．夾緊回路如下圖所示，若溢流閥的調整壓力p1＝3Mpa、減壓閥的調整壓力p2＝2Mpa。（1）試分析活塞空載運動時A、B兩點的壓力各為多少？減壓閥的閥芯處于什么狀態(tài)？（2）工件夾緊，活塞停止運動后，A、B兩點的壓力又各為多少？此時，減壓閥芯又處于什么狀態(tài)？答：（1）活塞空載運動，由于沒有負載力作用，系統工作壓力為0，不考慮沿程阻力損失，A、B兩點壓力相等，都是0MPa，此時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A點壓力為溢流閥調定壓力，3MPa，減壓閥也開始工作，B點壓力為2MPa，減壓閥閥芯處于半開狀態(tài)，保證出口壓力恒定在2MPa。五、計算題1．圖示的簡化回路中，溢流閥的調定壓力是2.5×106Pa,系統工作時溢流閥始終有油流回油箱，活塞有效工作面積為0.1m2,求當負載分別為：F=2×104N；F=0；F=-5×103N時，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，油缸進油腔壓力等于溢流閥的調定壓力，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F＝2×104N時，P2＝2.7×106Pa當F＝0時，P2＝2.5×106Pa當F＝5×104N時，P2＝2.55×106Pa2．已知液壓泵轉速為1000r/min，排量為160ml/r，額定壓力為30Mpa，實際輸出流量為150L/min，泵的總效率為0.87，求：⑴泵的理論流量；⑵泵的容積效率和機械效率；⑶驅動液壓泵所需的電動機功率。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％機械效率：ηm=η/ηv=0.87/0.9375=0.928=92.8%3)驅動液壓泵所需的電動機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行“快進——工進――快退――原位停止和液壓泵卸荷”的工作循環(huán)，完成電磁鐵動作順序表（通電“＋”，斷電“－”）1YA2YA3YA4YA快進+--+工進+-++快退-+-+原位停止，泵卸荷--__七、綜合題某機床進給回路如圖所示，它可以實現快進→工進→快退的工作循環(huán)。根據此回路工作原理，填寫電磁鐵動作表。（電磁鐵通電時，在空格中記“＋”號；反之，斷電記“－”號）電磁鐵工作環(huán)節(jié)1YA2YA3YA快進+-+工進+--快退-+-

請您刪除一下內容，O(∩_∩)O謝謝?。?！20XX年中央電大期末復習考試小抄大全，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