2015年電大液壓氣動(dòng)技術(shù)基礎(chǔ)期末復(fù)習(xí)題及答案參考小抄【電大考試必備】

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 4 溢流閥的控制油壓來(lái)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(méi)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(guò)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(guò)低；在易發(fā)生氣穴部位采用耐蝕材料及保護(hù)鍍層。 4.說(shuō)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(wèn)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(méi)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(kāi) （ 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(kāi)始工作， B 點(diǎn)壓力為 2MPa，減壓閥閥芯處于半開(kāi)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 2.5106Pa,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=2104N； F=0； F=-5103N 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 2.5106Pa。油缸兩腔的作用力相等，則有： P20.1+F=2.51060.1 即有： P2 2.5106+ F/0.1 當(dāng) F 2104N 時(shí)， P2 2.7106Pa 當(dāng) F 0 時(shí)， P2 2.5106Pa 當(dāng) F 5104N 時(shí)， P2 2.55106Pa 2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： 泵的理論流量； 泵的容積效率和機(jī)械效率； 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=nV=1000160=160000ml/min=160(L/min) 2)泵的容積效率： v=q/qt=150/160=0.9375=93.75 機(jī)械效率 ： m=/v=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=pqt=3010616010-3=80103(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“”） 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(xiě)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) 1YA 2YA 3YA 快進(jìn) + - + 1YA 2YA 3YA 4YA 快 進(jìn) + - - + 工 進(jìn) + - + + 快 退 - + - + 原位停止，泵卸荷 - - _ _ 工進(jìn) + - - 快退 - + - 請(qǐng)您刪除一下內(nèi)容， O( _ )O 謝謝！ 2015 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(guò)小抄 After earning his spurs in the kitchens of The Westin, The Sheraton, Sens on the Bund, and a sprinkling of other top-notch venues, Simpson Lu fi nally got the chance to become his own boss in November 2010. Sort of. The Shanghai-born chef might not actually own California Pizza Kitchen (CPK) but he is in sole charge of both kitchen and frontof- house at this Sinan Mansionsstalwart. Its certainly a responsibility to be the head chef, and then to have to manage the rest of the restaurant as well, the 31-year-old tells Enjoy Shanghai. In hotels, for example, these jobs are strictly demarcated, so its a great opportunity to learn how a business operates across the board. It was a task that management back in sunny California evidently felt he was ready for, and a vote of confi dence from a company that, to date, has opened 250 outlets in 11 countries. And for added pressure, the Shanghai branch was also CPKs China debut. For sure it was a big step, and unlike all their other Asia operations that are franchises, they decided to manage it directly to begin with, says Simpson. Two years ago a private franchisee took over the lease, but the links to CPK headquarters are still strong, with a mainland-based brand ambassador on hand to ensure the business adheres to its ethos of creating innovative, hearth-baked pizzas, a slice of PR blurb that Simpson insists lives up to the hype. They are very innovative, he says. The problem with most fast food places is that they use the same sauce on every pizza and just change the toppings. Every one of our 16 pizza sauces is a unique recipe that has been formulated to complement the toppings perfectly. The largely local customer base evidently agrees and on Saturday and Sunday, at least, the place is teeming. The kids-eat-for-free policy at weekends is undoubtedly a big draw, as well as is the spacious second-fl oor layout overlooked by a canopy of green from Fuxing Park over the road. The company is also focusing on increasing brand recognition and in recent years has taken part in outside events such as the regular California Week. Still, the sta are honest enough to admit that business could be better； as good, in fact, as in CPKs second outlet in the popular Kerry Parkside shopping mall in Pudong. Sinan Mansions has really struggled to get the number of visitors that were envisaged when it first opened, and it hasnt been easy for any of the tenants here, adds Simpson. Were planning a third outlet in the city in 2015, and we will probably choose a shopping mall again because of the better foot traffic. The tearooms once frequented by Coco Chanel and Marcel Proust are upping sticks and coming to Shanghai, Xu Junqian visits the Parisian outpost with sweet treats. One thing the century-old Parisian tearoom Angelina has shown is that legendary fashion designer Coco Chanel not only had style and glamor but also boasted great taste in food, pastries in particular. One of the most popular tearooms in Paris, Angelina is famous for having once been frequented by celebrities such as Chanel and writer Marcel Proust. Now Angelina has packed up its French ambience, efficient service, and beautiful, comforting desserts and flown them to Shanghai. At the flagship dine-in and take-out space in Shanghai, everything mimics the original tearoom designed from the beginning of the 20th century, in Paris, the height of Belle Epoque. The paintings on the wall, for example, are exactly the same as the one that depicts the landscape of southern France, the hometown of the owner； and the small tables are intentional imitations of the ones that Coco Chanel once sat at every afternoon for hot chocolate. The famous hot chocolate, known as LAfricain, is a luxurious mixture of four types of cocoa beans imported from Africa, blended in Paris and then shipped to Shanghai. Its sinfully sweet, rich and thick as if putting a bar of melting chocolate directly on the tongue and the fresh whipped cream on the side makes a light, but equally gratifying contrast. It is also sold in glass bottles as takeaway. The signature Mont-Blanc chestnut cake consists of three parts: the pureed chestnut on top, the vanilla cream like stuffing, and the meringue as base. Get all three layers in one scoop, not only for the different textures but also various flavors of sweetness. The dessert has maintained its popularity for a century, even in a country like France, perhaps the worlds most competitive place for desserts. A much overlooked pairing, is the Paris-New York choux pastry and N226 chocolate flavored tea. The choux pastry is a mouthful of airy pecan-flavored whipped cream, while the tea, a blend of black teas from China and Ceylon, cocoa and rose petals, offers a more subtle fragrance of flowers and chocolate. Ordering these two items, featuring a muted sweetness, makes it easier for you to fit into your little black dress. Breakfast, brunch, lunch and light supper are also served at the tearoom, a hub of many cultures and takes in a mix of different styles of French cuisines, according to the management team. The semi-cooked foie gras terrine, is seductive and deceptive. Its generously served at the size and shape of a toast, while the actual brioche toast is baked into a curved slice dipped with fig chutney. The flavor, however, is honest: strong, smooth and sublime. And you dont actually need the toast for crunchiness. This is the season for high teas, with dainty cups of fine china and little pastries that appeal to both visual and physical appetites. But there is one high tea with a difference, and Pauline D. Loh finds out just exactly why it is special. Earl Grey tea and macarons are all very well for the crucial recuperative break in-between intensive bouts of holiday season shopping. And for those who prefer savory to sweet, there is still the selection of classic Chinese snacks called dim sum to satisfy and satiate. High tea is a meal to eat with eye and mouth, an in-between indulgence that should be light enough not to spoil dinner, but sufficiently robust to take the edge off the hunger that strikes hours after lunch. The afternoon tea special at Shang-Xi at the Four Seasons Hotel Pudong has just the right elements. It is a pampering meal, with touches of luxury that make the high tea session a treat in itself. Whole baby abalones are braised and then topped on a shortcrust pastry shell, a sort of Chinese version of the Western vol-au-vent, but classier. Even classier is the dim sum staple shrimp dumpling or hargow, upgraded with the addition of slivers of midnight dark truffles. This is a master touch, and chef Simon Choi, who presides unchallenged at Shang-Xi, has scored a winner again. Sweet prawns and aromatic truffles whats not to love? His masterful craftsmanship is exhibited in yet another pastry a sweet pastry that is shaped to look like a walnut, but which you can put straight into the mouth. It crumbles immediately, and the slightly sweet, nutty morsel is so easy to eat youll probably reach straight for another. My favorite is the dessert that goes by the name yangzhi ganlu, or ambrosia from the gods. The hotel calls it chilled mango cream with sago, pomelo and birds nest made with ingredients that resonate with every female soul. It does taste like ambrosia, with the sweet-sour fragrance of the mango forming the first layer of taste and sensation, and the pomelo sacs and sago pearls providing the tactile contrast. The birds