【正文】 一系列特性，且因與低倍數(shù)放大時(shí)的珠母層有類同之處而被稱為珠光體。The rejected carbon forms the carbonrich cementite intermetallic with position essence, the net reaction at the eutectoid is austenite %C→ferrite %C+cementite %。To begin to understand these processes, consider a steel of the eutectoid position, % carbon, being slow cooled along line xx’ in the upper temperatures, only austenite is present, the % carbon being dissolved in solid solution with the the steel cools to 727℃(1341℉), several changes occur ，%的共析鋼，’線慢慢冷卻。Those portions of the ironcarbon diagram near the delta region and those above 2% carbon content are of little importance to the engineer and are simplified diagram, such as the one in , focuses on the eutectoid region and is quite useful in understanding the properties and processing of %的那些部分對(duì)工程師而言不重要，因此將它們刪除。由于合金鋼改善的物理性能，它們被大量使用在許多碳鋼不適用的地方。按所采用的步驟，鋼可以通過硬化來(lái)抵抗切削和磨損，也可以通過軟化來(lái)允許機(jī)加工。根據(jù)各自的結(jié)構(gòu)不同，聚合物可以是親水的或憎水的(喜歡或討厭水)、硬的或軟的、晶體狀的或非結(jié)晶質(zhì)的、易起反應(yīng)的或不易起反應(yīng)的。 can be crystalline or amorphous, but they usually have a bination of crystalline and amorphous structures(semicrystalline).結(jié)晶度：聚合物可以是晶體狀的或非結(jié)晶質(zhì)的，但它們通常是晶體狀和非結(jié)晶質(zhì)結(jié)構(gòu)的結(jié)合物(半晶體)。 point(glass transition temperature)and the melting point of a polymer will determine which it will be suitable for temperatures usually determine the upper limit for which a polymer can be ：聚合物的軟化點(diǎn)(玻璃狀轉(zhuǎn)化溫度)和熔化點(diǎn)決定了它是否適合應(yīng)用。它們的強(qiáng)度通?？刹捎眉訌?qiáng)復(fù)合結(jié)構(gòu)來(lái)改善。這種重復(fù)結(jié)構(gòu)產(chǎn)生鏈狀大分子。Particlereinforced posites Particles used for reinforcing include ceramics and glasses such as small mineral particles, metal particles such as aluminum, and amorphous materials, including polymers and carbon [番茄用戶1] [番茄用戶2] [番茄用戶3] [番茄用戶4] [番茄用戶5] [番茄用戶6] 用于加強(qiáng)的微粒包含了陶瓷和玻璃之類的礦物微粒，鋁之類的金屬微粒以及包括聚合物和碳黑的非結(jié)晶質(zhì)微粒。Fiberreinforced posites are used in some of the most advanced, and therefore most expensive sports equipment, such as a timetrial racing bicycle frame which consists of carbon fibers in a thermoset polymer ，例如計(jì)時(shí)賽競(jìng)賽用自行車骨架就是用含碳纖維的熱固塑料基材制成的。Fiberreinforced Composites Reinforcing fibers can be made of metals, ceramics, glasses, or polymers that have been turned into graphite and known as carbon increase the modulus of the matrix 加強(qiáng)纖維可以是金屬、陶瓷、玻璃或是已變成石墨的被稱為碳纖維的聚合物。例子有聚合物/陶瓷和金屬/陶瓷復(fù)合材料。In order for the core glass to have a higher refractive index than the cladding, the core glass is doped with a small, controlled amount of an impurity, or dopant, which causes light to travel slower, but does not absorb the ，在其中摻入微小的、可控?cái)?shù)量的能減緩光速而不會(huì)吸收光線的雜質(zhì)或攙雜劑。作為替代，一般采用“燒結(jié)”或“焙燒”工藝。陶瓷和玻璃都有一個(gè)主要的缺點(diǎn)：它們?nèi)菀灼扑?。Many ceramics are good electrical and thermal ceramics have special properties: some ceramics are magnetic materials。照此定義，陶瓷材料也應(yīng)包括玻璃；然而許多材料科學(xué)家添加了“陶瓷”必須同時(shí)是晶體物組成的約定。For example, adding a small amount of iron to aluminum will make it , adding some chromium to steel will slow the rusting process, but will make it more ，往鋁里加少量鐵可使其更強(qiáng)。It is impossible to see through metals, since these valence electrons absorb any photons of light which reach the photons pass ，所以透過金屬不可能看得見。汽車上壓皺的區(qū)域在它們斷裂前通過經(jīng)歷塑性變形來(lái)吸收能量。Plastic deformation is the ability of bend or deform before engineers, we usually design materials so that they don’t deform under normal don’t want your car to lean to the east after a strong west 。然而，諸如鋁和鎂之類的一些金屬則具有低密度，并被用于既需要金屬特性又要求重量輕的場(chǎng)合。Some metal alloys, such as those based on aluminum, have low densities and are used in aerospace applications for fuel alloys also have high fracture toughness, which means they can withstand impact and are ，例如鋁基合金，其密度低，可用于航空航天以節(jié)約燃料。and gold jewelry which usually contains an alloy of gold and 。在極低的溫度下，某些金屬和金屬化合物能轉(zhuǎn)變成超導(dǎo)體。Engineering materials may be further subdivided into: ①M(fèi)etal ②Ceramics ③Composite ④Polymers, ：①金屬材料②陶瓷材料③復(fù)合材料 ④聚合材料，等等。他們也把材料分為有機(jī)材料(曾經(jīng)有生命的)和無(wú)機(jī)材料(從未有生命的)。在開、閉環(huán)兩種系統(tǒng)中,閉環(huán)更精確,一般說來(lái)更昂貴。比如,一臺(tái)數(shù)控銑床的工作臺(tái)突然過載,阻力矩超過電機(jī)轉(zhuǎn)矩時(shí),將沒有響應(yīng)信號(hào)送回到控制器。環(huán)的一個(gè)分析者把真實(shí)的位置與需要的位置作比較,而且不同是考慮過的錯(cuò)誤。當(dāng)多數(shù)是索引或其他的自動(dòng)化申請(qǐng)所必備者的時(shí)候,步進(jìn)電機(jī)對(duì)運(yùn)行一個(gè)精確的有角進(jìn)步也是理想的。接受到的信號(hào)與紙帶輸入的信號(hào)相比較,它們之間的任何偏差都可得到糾正。閱讀裝置必須要能以比控制系統(tǒng)處理數(shù)據(jù)更快的速度來(lái)閱讀數(shù)據(jù)程序塊?？刂茊卧邮芎蛢?chǔ)存編碼數(shù)據(jù),直至形成一個(gè)完整的信息程序塊,然后解釋數(shù)控指令,并引導(dǎo)機(jī)床得到所需運(yùn)動(dòng)。穿孔紙帶是在帶有特制穿孔附件的打字機(jī)或直接連到計(jì)算機(jī)上的紙帶穿孔裝置上做成的。紙帶上的整個(gè)數(shù)控程序由這些連續(xù)數(shù)據(jù)單元連接而成。人工輸入需要操作者控制每個(gè)操作,這是一個(gè)既慢又單調(diào)的過程,除了簡(jiǎn)單加工場(chǎng)合或特殊情況,已很少使用。人工方法作為輸人數(shù)據(jù)唯一方法時(shí),只限于少量輸入。點(diǎn)位控制機(jī)床采用異步電動(dòng)機(jī),因此,主軸的定位只能通過完成一個(gè)運(yùn)動(dòng)或一個(gè)電動(dòng)機(jī)的轉(zhuǎn)動(dòng)來(lái)實(shí)現(xiàn)。數(shù)字、字母和符號(hào)用適當(dāng)?shù)母袷骄幋a為一個(gè)特定工件定義指令程序。only the coordinates of the end points of the motions are accurately type of control is suitable for drill presses and some boring machines, where drilling, tapping, or boring operations must be performed at various locations on the work or Linear Control StraightLine control systems are able to move the cutting tool parallel to one of the major axes of the machine tool at a controlled rate suitable for is normally only possible to move in one direction at a time, so angular cuts on the work piece are not possible, consequently, for milling machines, only rectangular configurations can be machined or for lathes only surfaces parallel or perpendicular to the spindle axis can be type of controlled motion is often referred to as linear control or a halfaxis of with this form of control are also capable of pointtopoint original N/C used the closed—loop the two systems, closed and open loop, closed loop is more accurate and, as a consequence, is generally more , open—loop systems were used almost entirely for lightduty applications because of inherent power limitations previously associated with conventional electric stepping advances in the development of electro hydraulic stepping motors have led to increasingly heavier machine load 數(shù)控技術(shù)數(shù)控是可編程自動(dòng)化技術(shù)的一種形式,通過數(shù)字、字母和其他符號(hào)來(lái)控制加工設(shè)備。數(shù)控機(jī)床有兩種基本形式：點(diǎn)位控制和連續(xù)控制(也稱為輪廓控制)。數(shù)據(jù)輸人裝置,也稱“人機(jī)聯(lián)系裝置”,可用人工或全自動(dòng)方法向機(jī)床提供數(shù)據(jù)。在大多數(shù)情況下,按鈕、開關(guān)和其他類似的旋鈕是數(shù)據(jù)輸入元件。每一個(gè)程序塊代表一種加工功能、一種操作或兩者的組合。此時(shí),操作者只是簡(jiǎn)單地上、下工件。雖然紙帶上的數(shù)據(jù)是自動(dòng)進(jìn)給的,但實(shí)際編程卻是手工完成的,在編碼紙帶做好前,編程者經(jīng)常要和一個(gè)計(jì)劃人員或工藝工程師一起工作,選擇合適的數(shù)控機(jī)床,決定加工材料,計(jì)算切削速度和進(jìn)給速度,決定所需刀具類型,仔細(xì)閱讀零件圖上尺寸,定下合適的程序開始的零參考點(diǎn),然后寫出程序清單,其上記載有描述加工順序的編碼數(shù)控指令,機(jī)床按順序加工工件到圖樣要求。有些光電裝置能以高達(dá)每秒1000個(gè)字節(jié)的速度閱讀,這對(duì)保持機(jī)床連續(xù)動(dòng)作是必須的,否則,在輪廓加工時(shí),刀具可能在工件上產(chǎn)生劃痕。位置控制通過傳感器實(shí)現(xiàn),在實(shí)際工作時(shí),記錄下滑臺(tái)的位置,并將這些信息送回控制單元。對(duì)于一件事物,它被不連續(xù)直流電壓脈沖驅(qū)使,是來(lái)自數(shù)傳計(jì)算機(jī)和其他的自動(dòng)化的非常方便的輸出控制系統(tǒng)。這些申請(qǐng)的大部分是公開環(huán) ,但是雇用回應(yīng)環(huán)