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《機(jī)電工程專業(yè)英語（第2版）》共有27篇課文，主要內(nèi)容包括機(jī)械設(shè)計制造技術(shù)、機(jī)械工程材料、公差與配合、數(shù)控技術(shù)、機(jī)電一體化技術(shù)、材料成形、模具設(shè)計與制造、汽車工程和科技寫作等方面的專業(yè)英語知識。同時，為了反應(yīng)本學(xué)科的發(fā)展趨勢，又增添了微機(jī)械（MEMS）設(shè)計技術(shù)和熱管工程應(yīng)用技術(shù)方面的內(nèi)容。書后附有科技英語翻譯及寫作的簡單介紹，還附有課文參考譯文。
《機(jī)電工程專業(yè)英語（第2版）》適合作為機(jī)械設(shè)計制造及自動化、機(jī)械工程及自動化、機(jī)電工程等專業(yè)的專業(yè)英語教材，也可以供從事機(jī)械工程各專業(yè)工作的工程技術(shù)人員參考使用。

    本書第2版是在第1版的基礎(chǔ)上，吸取多所大學(xué)教師在使用本書過程中提出的諸多寶貴意見，對全書進(jìn)行修訂和補(bǔ)充。本書的主要目的是使讀者掌握機(jī)械工程專業(yè)英語術(shù)語及用法，培養(yǎng)和提高讀者閱讀和翻譯專業(yè)英語文獻(xiàn)資料的能力。
    本書的主要內(nèi)容包括機(jī)械設(shè)計制造技術(shù)、機(jī)械工程材料、公差與配合、數(shù)控技術(shù)、機(jī)電一體化技術(shù)、材料成形、模具設(shè)計與制造、汽車工程和科技寫作等方面的專業(yè)英語知識。同時，為了反映本學(xué)科的發(fā)展趨勢，我們又增添了微機(jī)械（MEMS）設(shè)計技術(shù)和熱管工程應(yīng)用技術(shù)方面的內(nèi)容。書后附有科技英語翻譯及寫作的簡單介紹，還附有課文參考譯文。
    本書第2版共有27篇課文，每篇課文分為四個部分：Text部分是與本章主題密切相關(guān)的精讀部分，是課程中講解和學(xué)習(xí)的主體，在論述完整的同時保證一定的難度；Words and Prases部分是重點(diǎn)難點(diǎn)詞匯和短語解析；Complex Sentence Analysis部分是重點(diǎn)難點(diǎn)句子分析和相關(guān)內(nèi)容的背景分析；Exercise部分是與主題課文相關(guān)的泛讀部分和練習(xí)題，供讀者課余時間拓展知識面，鞏固所學(xué)習(xí)的內(nèi)容。
    本書第2版具有一定的專業(yè)性和難度，通過對本書的深入學(xué)習(xí)，讀者可以迅速提高專業(yè)英語閱讀和寫作能力。本書適合作為機(jī)械設(shè)計制造及自動化、機(jī)械工程及自動化、機(jī)電工程等專業(yè)的專業(yè)英語教材，也可以供從事機(jī)械工程各專業(yè)工作的工程技術(shù)人員參考使用。
    本書第2版由朱林、楊春杰任主編，鐘利萍、何法江、王麗君任副主編；參加編寫的還有趙運(yùn)才、方曉麗、田宏宇、么永強(qiáng)、匡江紅和石玉祥。
    由于編者時間和水平有限，書中疏漏及不妥之處定然存在，敬請廣大讀者批評指正。

    Lesson 4  Machine Parts （II）
    Fastener
    Fasteners are devices which permit one part to be joined to a second part and， hence， theyare involved in almost all designs.
    There are three main classifications of fasteners， which are described as follows：
    （1）Removable. This type permits the parts to be readily disconnected without damagingthe fastener. An example is the ordinary nut-and-bolt fastener.
    （2）Semi permanent. For this type， the parts can be disconnected， but some damage usuallyoccurs to the fastener. One such example is a corer pin.
    （3）Permanent. When this type of fastener is used， it is intended that the parts will never bedisassembled. Examples are riveted joints and welded joints.
    The importance of fasteners can be realized when referring to any complex product. In the case of the automobile， there are literally thousands of parts which are fastened together top roduce the total product. The failure or loosening of a single fastener could result in a simple nuisance such as a door rattle or in a serious situation such as a wheel coming off. Suchpossibilities must be taken into account in the selection of the type of fastener for the specific application.
    Nuts， bolts， and screws are undoubtedly the most common means of joining materials. Since they are so widely used， it is essential that these fasteners attain maximum effectiveness at the lowest possible cost.
    An ordinary nut loosens when the forces of vibration overcome those of friction. In a nut and lock washer combination， the lock washer supplies an independent locking feature preventing the nut from. loosening. The lock washer is useful only when the bolt might loos enbecause of a relative change between the length of the bolt and the parts assembled by it. [2]This change in the length of the bolt can be caused by a number of factors-creep in the bolt， loss of resilience， difference in thermal expansion between the bolt and the bolted members， or wear. In the above static cases， the expanding lock washer holds the nut under axial load and keeps the assembly tight. When relative changes are caused by vibration forces， the lock washer is not nearly as effective.
    Rivets are permanent fasteners.

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