【正文】 ill have important applications when machining cast iron, hardened steels and high melting point socalled ceramic group of cutting tools represents the most recent development in cutting tool consist mainly of sintered oxides, usually aluminum oxide, and are almost invariably in the form of clamped of the parative cheapness of ceramic tips and the difficulty of grinding them without causing thermal cracking, they are made as throwaway tools are a postwar introduction and are mot yet in general factory most likely application is in cutting metal at very high speeds, beyond the limits possible with carbide resist the formation of a builtup edge and in consequence produce good surface the present generation of machine tools is designed with only sufficient power to exploit carbide tooling, it is likely that, for the time being, ceramics will be restricted to highspeed finish machining where is sufficient power available for the light cuts extreme brittleness of ceramic tools has largely limited their use to continuous cuts, although their use in milling is now they are poorer conductors of heat than carbides, temperatures at the rake face are higher than in carbide tools, although the friction force is usually strengthen the cutting edge, and consequently improve the life of the ceramic tool, a small chamfer or radius is often stoned on the cutting edge, although this increases the power producing very fine finishes of （23um)on nonferrous metals such as copper and aluminum, diamond tools are often diamond is brazed to a steel turning and boring are essentially finishing operations, as the forces imposed by any but the smallest cuts cause the diamond to fracture or be torn from its 共 14 頁 第 7 頁┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ 裝 ┊ ┊ ┊ ┊ ┊ 訂 ┊ ┊ ┊ ┊ ┊ 線 ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊畢業(yè)設(shè)計(jì)（論文）報(bào)告紙suitable conditions diamonds have exceptionally long cutting polycrystalline diamonds are now available as mechanically clamped cutting to their high cost they have very limited applications, but are sometimes used for machining abrasive aluminumsilicon alloys, fused silica and reinforced random orientation of their crystals gives them improved impact resistance, making them suitable for interrupted 14 頁 第 8 頁┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ 裝 ┊ ┊ ┊ ┊ ┊ 訂 ┊ ┊ ┊ ┊ ┊ 線 ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊畢業(yè)設(shè)計(jì)（論文）報(bào)告紙車床用于車外圓、端面和鏜孔等加工的機(jī)床稱作車床。由于車床除了用于車外圓還能用于鏜孔、車端面、鉆孔和鉸孔，車床的多功能性可以是共建在一次定位安裝中完成多種加工。兩千多年前就已經(jīng)有了車床。莫德斯利發(fā)明了一種具有絲杠的車床。這位聰明的英國人還發(fā)明了一種把主軸和絲杠相連的變速裝置，這樣就可以切削螺紋。床身是車床的基礎(chǔ)件。通常在床身上那個面有內(nèi)外另組平行的導(dǎo)軌。由于其他的部件要安置在導(dǎo)軌上并（或）在導(dǎo)軌上移動，導(dǎo)軌要經(jīng)過精密加工，以保證其裝配精度。導(dǎo)軌上的任何誤差，常常會使整個機(jī)床的精度遭到破壞。主軸箱安裝在車身一端內(nèi)導(dǎo)軌的固定位置上。它基本上有一個安裝在精密軸承中的空心主軸和一系列變速齒輪——類似于卡車變速箱所組成，通過變速齒輪，主軸可以在許多種轉(zhuǎn)速下旋轉(zhuǎn)。在現(xiàn)代車床上只需扳動2～4個手柄，就能得到全部檔位的轉(zhuǎn)速。由于車床的精度在很大程度上取決于主軸，因此主軸的結(jié)構(gòu)尺寸較大，通常安裝在緊密配合的重型圓錐滾子軸承或球軸承中。主軸孔的大小是車床的一個重要尺寸，因?yàn)楫?dāng)工件必須通過主軸孔供料時，它確定了能夠加工棒料毛坯的最大外徑尺寸。而小型的車共 14 頁 第 9 頁┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ 裝 ┊ ┊ ┊ ┊ ┊ 訂 ┊ ┊ ┊ ┊ ┊ 線 ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊畢業(yè)設(shè)計(jì)（論文）報(bào)告紙床常有螺紋截面供安裝卡盤之用。這些附件組成了一個大直徑的圓錐體，以保證對卡盤進(jìn)行精確地裝配，并且不用旋轉(zhuǎn)這些笨重的附件就可以鎖定或松開卡盤或花盤。大多數(shù)現(xiàn)代車床都裝置有5～15馬力的電動機(jī)，為硬質(zhì)合金和金屬陶瓷合金刀具提供足夠的動力，進(jìn)行高速切削。底座與床身的內(nèi)側(cè)導(dǎo)軌配合，并可以子導(dǎo)軌上做縱向移動，底座上有一個可以使整個尾座組件加緊在任意位置上的裝置。尾座組件的第三部分是尾座套筒，它是一個直徑通常在2～3英寸之間的鋼制空心圓柱軸?；顒犹淄驳拈_口一端具有莫氏錐度，可以用于安裝頂尖或諸如鉆頭之類的各種刀具。鎖定裝置可以使套筒在所需的位置上夾緊。拖板是一個相對平滑的H形鑄件，安裝在床身外側(cè)導(dǎo)軌上，并可以在上面移動。橫拖板可以帶動刀具垂直于工件的旋轉(zhuǎn)軸線切削。上刀架安裝在底座上，可用手輪和刻度盤控制一個短絲杠使其前后移動。通過轉(zhuǎn)動溜板箱前的手輪，可以手動操作拖板沿床身移動。利用光桿可以將動力傳遞給大拖板和橫拖板。通過溜板箱前的換向手柄可使嚙合齒輪與其中的一個錐齒輪嚙合，為大拖板提供“向前”或“向后”的動力。共 14 頁 第 10 頁┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ 裝 ┊ ┊ ┊ ┊ ┊ 訂 ┊ ┊ ┊ ┊ ┊ 線 ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊畢業(yè)設(shè)計(jì)（論文）報(bào)告紙對于螺紋加工，絲杠提供了第二種縱向移動的方法。而絲杠產(chǎn)生的運(yùn)動是通過滑板箱與絲杠之間的直接機(jī)械連接來實(shí)現(xiàn)的，對于螺母可以實(shí)現(xiàn)這種連接。當(dāng)對開螺母閉合時，可以沿絲杠直接驅(qū)動拖板，而不會出現(xiàn)打滑的可能性。齒輪箱的輸出端與光杠和絲杠連接。一臺典型的車床的主軸每旋轉(zhuǎn)一圈，；。金屬切削刀具刀具的形狀（特別是其角度）和材料是刀具的兩個非常重要的因素。刀具幾何參數(shù)刀具的角度不僅在很大程度決定了刀具的壽命，而且也決定加工的表面質(zhì)量。車刀、銑刀、鉆頭甚至是砂輪的設(shè)計(jì)，所要考慮的因素基本相同。刀具特征參數(shù)名目繁多，技術(shù)文獻(xiàn)中術(shù)語使用也很混亂。單尖刀具是指只有一個前刀面和一條連續(xù)切削刃的刀具。如該角后傾，則為正角，否則為負(fù)角。角度2為側(cè)前角，它是刀具前刀面在垂直于刀具基面的橫向剖面內(nèi)的傾斜角。端后角是刀具基面的垂線與緊靠端切削刃下的斷后刀面之間的夾角，即圖中角度3。為了節(jié)省磨刀時間，刀具段后刀面的一部分有時可以直接鍛造成形，而不需要進(jìn)行磨削。通常端切削刃與端后刀面是斜交的，因此，端后角最好是在于端切削刃相垂直的平面內(nèi)進(jìn)行測量。角度5表示側(cè)后角，它是端切削刃下面的側(cè)后刀面與通過切削刃并垂直于刀具基面的直線之間的夾角。角度6為端切削刃角，它是端切削刃和垂直于刀具柄側(cè)面的直線之間的夾角。角度7為側(cè)切削刃角，它是測切削刃和刀柄側(cè)面之間的夾角。該角度越大，刀具壽命越長，但顫振的可能性也隨之增加。角度8為刀尖角，它是兩條切削刃之間的夾角。刀尖圓弧半徑的尺寸對表面光潔度及顫振有影響。下面討論最重要的幾種材料和它們對刀具設(shè)計(jì)的影響。C左右開始回火，而且這種軟化過程隨著溫度的升高而繼續(xù)。：為克服普通碳素鋼切削速度較低的特點(diǎn)，本世紀(jì)初，幾種稱為高速鋼的合金鋼開始用于金屬切削。它們在高達(dá)600176。實(shí)驗(yàn)表明：高速鋼切削低碳鋼時，(350ft/min),就會很快失效，(150ft/min)時，就不能成功切削低碳鋼。因?yàn)檩^高成本和較低的斷裂強(qiáng)度，它們通常以刀片形式銅焊在鋼質(zhì)刀柄上或機(jī)械夾持在特質(zhì)夾具撒上。硬質(zhì)合金刀具在高溫時具有高硬度，故它們的切削速度比高速鋼高得多，切削低碳鋼時為3～4m/s(600800ft/min),它們有幾種牌號專用于大多數(shù)加工場合。最近，已經(jīng)出現(xiàn)碳化鈦或氮化鈦涂層碳化鎢刀具（）。因此，不降低刀具壽命就可得到較高的金屬切削率，或不改變金屬切削率而延長刀具壽命。：所謂的陶瓷刀具代表了刀具材料的最新進(jìn)展，它們主要由燒結(jié)氧化物（通常是氧化鋁）組成，而且?guī)缀醪蛔兊刈龀蓨A持刀片。陶瓷刀具是戰(zhàn)后出現(xiàn)的，還沒有在工廠里得到普遍應(yīng)用。陶瓷刀具能抑制積屑瘤的形成，能形成好的表面光潔度。陶瓷刀具特別脆，盡管目前已能進(jìn)行銑削，陶瓷刀具主要還是限于連續(xù)切削。為了強(qiáng)化切削刃，進(jìn)而改進(jìn)刀具的壽命，經(jīng)常在切削刃上做成一個小倒棱或圓弧，雖然這樣做會增加功率消耗。金剛石用銅焊焊接在碳鋼刀柄上。在適合的條件下，金剛石切削壽命最長。共 14 頁 第 14 頁第二篇：計(jì)算機(jī)英語論文翻譯畢業(yè)設(shè)計(jì)DATA WAREHOUSEData warehousing provides architectures and tools for business executives to systematically organize, understand, and use their data to make strategic large number of organizations have found that data warehouse systems are valuable tools in today39。s operational warehouse systems allow for the integration of a variety of application support information processing by providing a solid platform of consolidated, historical data for to , a leading architect in the construction of data warehouse systems, “a data warehouse is a subjectoriented, integrated, timevariant, and nonvolatile collection of data in support of management39。s take a closer look at each of these key features.(1)Subjectoriented: A data warehouse is organized around major subjects, such as customer, vendor, product, and than concentrating on the daytoday operations and transaction processing of an organization, a data warehouse focuses on the modeling and analysis of data for decision , data warehouses typically provide a simple and concise view around particular subject issues by excluding data that are not useful in the decision support process.(2)Integrated: A data warehouse is usually constructed by integra