2023年全國碩士研究生考試考研英語一試題真題(含答案詳解+作文范文)_第1頁
已閱讀1頁,還剩11頁未讀 繼續(xù)免費(fèi)閱讀

下載本文檔

版權(quán)說明:本文檔由用戶提供并上傳,收益歸屬內(nèi)容提供方,若內(nèi)容存在侵權(quán),請進(jìn)行舉報(bào)或認(rèn)領(lǐng)

文檔簡介

1、<p>  The Brake Bible</p><p>  Brakes - what do they do?</p><p>  The simple answer: they slow you down.The complex answer: brakes are designed to slow down your vehicle but probably not b

2、y the means that you think. The common misconception is that brakes squeeze against a drum or disc, and the pressure of the squeezing action is what slows you down. This in fact is only part of the equation. Brakes are e

3、ssentially a mechanism to change energy types. When you're travelling at speed, your vehicle has kinetic energy. When you apply the brakes, the pads or shoes</p><p>  Thermodynamics, brake fade and drill

4、ed rotors.</p><p>  If you ride a motorbike or drive a race car, you're probably familiar with the term brake fade, used to describe what happens to brakes when they get too hot. A good example is coming

5、 down a mountain pass using your brakes rather than your engine to slow you down. As you start to come down the pass, the brakes on your vehicle heat up, slowing you down. But if you keep using them, the rotors or drums

6、stay hot and get no chance to cool off. At some point they can't absorb any more heat so the brak</p><p>  Rotor technology.If a brake rotor was a single cast chunk of steel, it would have terrible heat

7、 dissipation properties and leave nowhere for the vapourised gas to go. Because of this, brake rotors are typically modified with all manner of extra design features to help them cool down as quickly as possible as well

8、as dissapate any gas from between the pads and rotors. The diagram here shows some examples of rotor types with the various modification that can be done to them to help them create mo</p><p>  1: Basic brak

9、e rotor. 2: Grooved rotor - the grooves give more bite and thus more friction as they pass between the brake pads They also allow gas to vent from between the pads and the rotor. 3: Grooved, drilled rotor - the drilled h

10、oles again give more bite, but also allow air currents (eddies) to blow through the brake disc to assist cooling and ventilating gas. 4: Dual ventilated rotors - same as before but now with two rotors instead of one, and

11、 with vanes in between them to generate a vorte</p><p>  Big rotors.How does all this apply to bigger brake rotors - a common sports car upgrade? Sports cars and race bikes typically have much bigger discs

12、or rotors than your average family car. A bigger rotor has more material in it so it can absorb more heat. More material also means a larger surface area for the pads to generate friction with, and better heat dissipatio

13、n. Larger rotors also put the point of contact with the pads further away from the axle of rotation. This provides a larger mechan</p><p>  The different types of brake.</p><p>  All brakes work

14、 by friction. Friction causes heat which is part of the kinetic energy conversion process. How they create friction is down to the various designs. </p><p>  Bicycle wheel brakes</p><p>  I thou

15、ght I'd cover these because they're about the most basic type of functioning brake that you can see, watch working, and understand. The construction is very simple and out-in-the-open. A pair of rubber blocks are

16、 attached to a pair of calipers which are pivoted on the frame. When you pull the brake cable, the pads are pressed against the side or inner edge of the bicycle wheel rim. The rubber creates friction, which creates heat

17、, which is the transfer of kinetic energy that slows you down.</p><p>  Drum brakes - single leading edge</p><p>  The next, more complicated type of brake is a drum brake. The concept here is s

18、imple. Two semicircular brake shoes sit inside a spinning drum which is attached to the wheel. When you apply the brakes, the shoes are expanded outwards to press against the inside of the drum. This creates friction, wh

19、ich creates heat, which transfers kinetic energy, which slows you down. The example below shows a simple model. The actuator in this case is the blue elliptical object. As that is twisted, it forces ag</p><p&g

20、t;  The "single leading edge" refers to the number of parts of the brake shoe which actually contact the spinning drum. Because the brake shoe pivots at one end, simple geometry means that the entire brake pad

21、cannot contact the brake drum. The leading edge is the term given to the part of the brake pad which does contact the drum, and in the case of a single leading edge system, it's the part of the pad closest to the act

22、uator. This diagram (right) shows what happens as the brakes are applied. The </p><p>  Drum brakes - double leading edge</p><p>  The drawbacks of the single leading edge style of drum brake ca

23、n be eliminated by adding a second return spring and turning the pivot point into a second actuator. Now when the brakes are applied, the shoes are pressed outwards at two points. So each brake pad now has one leading an

24、d one trailing edge. Because there are two brake shoes, there are two brake pads, which means there are two leading edges. Hence the name double leading edge. </p><p>  Disc brakes</p><p>  Some

25、 background. Disc brakes were invented in 1902 and patented by Birmingham car maker Frederick William Lanchester. His original design had two discs which pressed against each other to generate friction and slow his car d

26、own. It wasn't until 1949 that disc brakes appeared on a production car though. The obscure American car builder Crosley made a vehicle called the Hotshot which used the more familiar brake rotor and calipers that we

27、 all know and love today. His original design was a bit crap</p><p>  Disc brakes are an order of magnitude better at stopping vehicles than drum brakes, which is why you'll find disc brakes on the front

28、 of almost every car and motorbike built today. Sportier vehicles with higher speeds need better brakes to slow them down, so you'll likely see disc brakes on the rear of those too.</p><p><b>  制動(dòng)器

29、</b></p><p>  制動(dòng)器:它們的作用是什么?</p><p>  簡單說:它會(huì)使你的汽車慢下來。</p><p>  復(fù)雜說:制動(dòng)器被用來讓你的車減速,但可能不是你所想的意思。大部分人誤解為,制動(dòng)器擠壓制動(dòng)鼓或制動(dòng)片,擠壓的壓力的作用使車慢下來。但是這只是制動(dòng)的一部分。制動(dòng)系統(tǒng)本質(zhì)上是改變能量的類型。當(dāng)你在全速行駛時(shí),你的汽車獲得動(dòng)能。當(dāng)你踩

30、下剎車,墊子或鞋子對制動(dòng)鼓和轉(zhuǎn)子的作用轉(zhuǎn)化為摩擦熱能。剎車的冷卻使車的熱能消散,減慢車速。這是熱力學(xué)第一定律,有時(shí)被視為能量守恒定律。也是就說:能量不能被創(chuàng)造也不能被消滅,只能由一種形式轉(zhuǎn)換成另一種。制動(dòng)情況下,它是動(dòng)能轉(zhuǎn)化為熱能。</p><p>  角向力。 因?yàn)樵诒P式制動(dòng)器的剎車片和轉(zhuǎn)子的位置,摩擦產(chǎn)生的接觸點(diǎn)的位置也產(chǎn)生了一個(gè)機(jī)械的抵御轉(zhuǎn)子的回轉(zhuǎn)運(yùn)動(dòng)。</p><p>  熱力學(xué),

31、制動(dòng)失效,鉆孔轉(zhuǎn)子。如果你騎摩托車或駕駛一輛賽車,你或許熟悉制動(dòng)失效,描述當(dāng)制動(dòng)器太熱,他發(fā)生了什么。一個(gè)很好的例子就是從山上下來使用剎車制動(dòng),而不是你的引擎使你減速。當(dāng)汽車開始滑動(dòng)下來時(shí),剎車使汽車產(chǎn)生熱能,使你減速。但是如果你持續(xù)使用他們, 轉(zhuǎn)子或鼓留熱并沒有機(jī)會(huì)冷卻。從某種意義上說他們不能吸收更多的熱量,使剎車墊熱了起來。在每一個(gè)墊子的摩擦材料有某種共同的樹脂一旦開始變得太熱,該樹脂開始蒸發(fā),形成氣。由于氣體之間不能待在墊層及轉(zhuǎn)

32、子,而是形成薄薄的一層在兩個(gè)之間準(zhǔn)備排走。墊失去與轉(zhuǎn)子的接觸,減少摩擦和熱量。這是完全的制動(dòng)失效。典型的補(bǔ)救辦法,將車停了下來,等待幾分鐘。由于制動(dòng)部件降溫,吸收熱量的原因,下一次您使用剎車的能力,似乎會(huì)好一點(diǎn)。這種類型的制動(dòng)失效在舊車輛更常見。新的車輛往往從剎車墊中減少排氣,但他們?nèi)杂兄苿?dòng)失效。為什么呢?它仍然因?yàn)閯x車墊太熱。猶由于新的剎車墊合成,襯墊的熱傳遞到卡鉗一旦轉(zhuǎn)子太熱了,制動(dòng)液開始沸騰冒泡。因?yàn)榭諝馐强蓧嚎s的(制動(dòng)液不是)

33、當(dāng)你踩剎車,氣泡的壓縮代替了流體轉(zhuǎn)移到制動(dòng)卡鉗。這就是現(xiàn)代制動(dòng)失效。工程師們是怎樣設(shè)計(jì)減少或消除剎車制動(dòng)失效的</p><p>  轉(zhuǎn)子技術(shù)。如果制動(dòng)轉(zhuǎn)子是一個(gè)單一的鋼鐵鑄塊,這將有嚴(yán)重的散熱性能和氣化氣無法排去。因此,剎車盤通常使用各種額外的設(shè)計(jì)特點(diǎn)的方式來改進(jìn)幫助他們冷卻下來,盡快使墊和轉(zhuǎn)子之間的任何氣體排走。.這里的圖表顯示了轉(zhuǎn)子類型的各種修改,可以改進(jìn)幫助他們創(chuàng)造更多的摩擦力,更迅速地驅(qū)散更多的熱量,

34、通風(fēng)氣體的一些例子。從左至右。</p><p>  1:基本制動(dòng)轉(zhuǎn)子。2:溝槽轉(zhuǎn)子-溝槽給予更多口,他們之間產(chǎn)生更多的摩擦,還允許氣體從墊和轉(zhuǎn)子之間的排走。3:溝槽鉆孔轉(zhuǎn)子-再給多一點(diǎn)口,但也讓氣流(渦旋)通過制動(dòng)盤協(xié)助冷卻和通風(fēng)。4:雙通風(fēng)轉(zhuǎn)子-以前一樣,然而現(xiàn)在有了兩個(gè)轉(zhuǎn)子而不是一個(gè),和他們之間葉片產(chǎn)生渦流將進(jìn)一步冷卻轉(zhuǎn)子同時(shí)試圖實(shí)際上從襯墊中排掉任何氣體。</p><p>  重要的

35、一點(diǎn):鉆孔轉(zhuǎn)子通常只使用于賽車。鉆孔使得轉(zhuǎn)子變?nèi)?,通常?huì)導(dǎo)致轉(zhuǎn)子產(chǎn)生各類裂縫。在賽車中這不是一個(gè)問題——在每場比賽或者每周都會(huì)更換剎車盤。但在路上的車,最終會(huì)導(dǎo)致剎車轉(zhuǎn)子失靈的,不是你能想象的。我只提這件事,因?yàn)橛性S多供應(yīng)商將為您提供鉆孔轉(zhuǎn)子,沒有直接提到這個(gè)事實(shí)。</p><p><b>  大轉(zhuǎn)子。</b></p><p>  這是如何適用于更大的剎車轉(zhuǎn)子-一種普

36、遍的跑車升級?汽車和自行車運(yùn)動(dòng)比賽通常有比一般的家庭汽車更大的盤或轉(zhuǎn)子。一個(gè)更大的轉(zhuǎn)子有更多的材料在里面,因此它可以吸收更多的熱量。更多的物質(zhì)也意味著更大的表面積,墊片產(chǎn)生摩擦,和更好的散熱。較大的角度也將轉(zhuǎn)子接觸墊進(jìn)一步遠(yuǎn)離軸旋轉(zhuǎn)。這提供了一個(gè)更大的機(jī)械優(yōu)勢抵抗旋轉(zhuǎn)的轉(zhuǎn)子本身。這個(gè)工作最好的說明,設(shè)想一種紡紗鋼軸上的閥瓣在你的面前。如果你夾緊你的大拇指任何一方的閥瓣靠近中間,你的大拇指將熱得非???,你會(huì)需要推動(dòng)相當(dāng)大的摩擦力使閥瓣慢下

37、來?,F(xiàn)在想象做同樣的事情,但是你的大拇指夾在一起接近外緣的閥瓣。閥瓣將停止旋轉(zhuǎn)得特別快,你的大拇指也不會(huì)很熱。簡單地說解釋整個(gè)原理就是更大轉(zhuǎn)子=更好的制動(dòng)原則。</p><p><b>  不同類型的制動(dòng)器。</b></p><p>  所有制動(dòng)器都產(chǎn)生摩擦力。摩擦力是熱的一部分動(dòng)能轉(zhuǎn)換過程。他們是如何不同的設(shè)計(jì)產(chǎn)生了摩擦的。</p><p>

38、<b>  自行車車輪制動(dòng)器</b></p><p>  我想我覆蓋這些,因?yàn)樗鼈兪亲罨绢愋偷闹苿?dòng)方式,你可以看到,看工作了解。設(shè)計(jì)非常簡單,在外部。一雙橡膠塊連接到一雙卡鉗,能在機(jī)架上旋轉(zhuǎn)。When you pull the brake cable, the pads are pressed against the side or inner edge of the bicycle wh

39、eel rim.當(dāng)你拉剎車線,剎車墊壓向一側(cè)或自行車輪輞的內(nèi)側(cè)邊緣。 The rubber creates friction, which creates heat, which is the transfer of kinetic energy that slows you down.橡膠產(chǎn)生摩擦,產(chǎn)生熱量,這是動(dòng)能轉(zhuǎn)移使車慢下來。 自行車制動(dòng)實(shí)際上There's only really two types of bicycl

40、e brake - those on which each brake shoe shares the same pivot point, and those with two pivot points.只有兩個(gè)類型 - 自行車剎車</p><p><b>  鼓式制動(dòng)器-單前沿</b></p><p>  下一個(gè),更加復(fù)雜的類型的制動(dòng)是鼓式制動(dòng)器。這是簡單的概念。兩

41、個(gè)半圓形的剎車片裝在里面連接一個(gè)旋轉(zhuǎn)的車輪的鼓。當(dāng)你踩下剎車,剎車片向外擴(kuò)大擠壓內(nèi)側(cè)的鼓。這造成了摩擦,產(chǎn)生熱量,轉(zhuǎn)移動(dòng)能,這將使車減速。下面的例子顯示了一個(gè)簡單的模型。制動(dòng)器在這種情況下是藍(lán)色橢圓形的對象。因?yàn)檫@是扭曲的,它的力使剎車片迫使他們向外擴(kuò)張。當(dāng)松開剎車,The return spring is what pulls the shoes back away from the surface of the brake drum

42、 when the brakes are released.回位彈簧從制動(dòng)鼓的表面拉回剎車片??吹秸鹿?jié)后面更多信息。"單前沿"是指實(shí)際接觸的旋轉(zhuǎn)鼓輪制動(dòng)蹄部件的數(shù)量。因?yàn)橹苿?dòng)蹄片在一端,簡單的幾何意味著整個(gè)剎車片無法都接觸到制動(dòng)鼓。單前沿就是部分剎車片的術(shù)語,那些接觸制動(dòng)鼓,在單一制動(dòng)情況下的方法,在最接近制動(dòng)器的襯墊。此圖 (右側(cè)) 顯示當(dāng)剎車時(shí),會(huì)發(fā)生什么情況。這剎車片向外壓和制動(dòng)襯墊的最初接觸制動(dòng)鼓的部分剎車片

43、就是前沿。制動(dòng)鼓旋轉(zhuǎn)實(shí)際上有助于制動(dòng)片向外加壓,因?yàn)閯x車片向口子的摩擦力。后沿的</p><p><b>  鼓剎車-雙前沿</b></p><p>  可以通過添加回位彈簧和旋轉(zhuǎn)第二個(gè)制動(dòng)器中心點(diǎn)來消除鼓式制動(dòng)器的單個(gè)前沿的缺點(diǎn)。踩下剎車時(shí),剎車片在兩個(gè)點(diǎn)向外壓。所以每個(gè)剎車片現(xiàn)在有一個(gè)前沿的和一個(gè)后沿。因?yàn)橛袃蓚€(gè)剎車蹄,那里有兩個(gè)剎車片,這意味著有兩個(gè)邊沿。因此名

44、稱雙前沿。</p><p>  盤式制動(dòng)器一些背景。</p><p>  盤式制動(dòng)器在 1902 年被發(fā)明,伯明翰汽車制造商檢基威廉 · 蘭徹斯特的專利。他原先的設(shè)計(jì)了兩個(gè)光盤,緊貼彼此產(chǎn)生摩擦來使車減速。直到 1949 盤式制動(dòng)器的量產(chǎn)車上使用。在美國汽車創(chuàng)始人克羅斯利發(fā)明了我們目前熟知和喜愛的快車,就是使用了很多類似的盤動(dòng)制動(dòng)器和卡鉗。他原先的設(shè)計(jì)雖然有點(diǎn)缺陷-制動(dòng)器持續(xù)不到

溫馨提示

  • 1. 本站所有資源如無特殊說明,都需要本地電腦安裝OFFICE2007和PDF閱讀器。圖紙軟件為CAD,CAXA,PROE,UG,SolidWorks等.壓縮文件請下載最新的WinRAR軟件解壓。
  • 2. 本站的文檔不包含任何第三方提供的附件圖紙等,如果需要附件,請聯(lián)系上傳者。文件的所有權(quán)益歸上傳用戶所有。
  • 3. 本站RAR壓縮包中若帶圖紙,網(wǎng)頁內(nèi)容里面會(huì)有圖紙預(yù)覽,若沒有圖紙預(yù)覽就沒有圖紙。
  • 4. 未經(jīng)權(quán)益所有人同意不得將文件中的內(nèi)容挪作商業(yè)或盈利用途。
  • 5. 眾賞文庫僅提供信息存儲(chǔ)空間,僅對用戶上傳內(nèi)容的表現(xiàn)方式做保護(hù)處理,對用戶上傳分享的文檔內(nèi)容本身不做任何修改或編輯,并不能對任何下載內(nèi)容負(fù)責(zé)。
  • 6. 下載文件中如有侵權(quán)或不適當(dāng)內(nèi)容,請與我們聯(lián)系,我們立即糾正。
  • 7. 本站不保證下載資源的準(zhǔn)確性、安全性和完整性, 同時(shí)也不承擔(dān)用戶因使用這些下載資源對自己和他人造成任何形式的傷害或損失。

評論

0/150

提交評論