书名：机械工程专业英语教程（第3版）pdf/doc/txt格式电子书下载

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作者：施平编

出版社：电子工业出版社

出版时间：2012-05-01

书籍编号：30466878

ISBN：9787121167416

正文语种：中文

字数：77503

版次：3

所属分类：教材教辅-大学

版权信息

书名：机械工程专业英语教程（第3版）

作者：施平

ISBN：9787121167416

版权所有 · 侵权必究

前言

专业英语是大学英语教学的一个重要组成部分，是促进学生从英语学习过渡到实际应用的有效途径。教育部颁布的《大学英语教学大纲》明确规定专业英语为必修课程，要求通过四年不间断的大学英语学习，培养学生以英语为工具交流信息的能力。编者们根据此精神编写了本书，以满足高等院校机械工程各专业学生的专业英语学习需求。

在此次再版前，编者们汲取了多所大学在使用本书过程中提出的许多宝贵意见，对全书进行了修订和补充。本书所涉及的内容包括力学、机械零件与机构、机械工程材料、润滑与摩擦、机械制图、公差与配合、机械设计、机械制造、管理、现代制造技术、科技写作等方面。通过这本教材，学生不仅可以熟悉和掌握本专业常用的及与本专业有关的单词、词组及其用法，而且可以深化本专业的知识，从而为今后的学习和工作打下良好的基础。

全书由68篇课文和10篇阅读材料组成，其中30篇课文有参考译文。本书选材广泛，内容丰富，语言规范，难度适中，便于自学。为了方便教学，本书另配有电子教案，向采纳本书作为教材的教师免费提供（获取方式：登录电子工业出版社华信教育资源网www.hxedu.com.cn或电话联系010—88254531或邮件联系qinshl＠phei.com.cn获得）。

本书由施平主编，参加编写工作的有李越、胡明、乔世坤、田锐、施晓东、侯双明、胡淼、陶文成，由贾艳敏担任主审。

由于编者水平有限，书中难免有不足和欠妥之处，恳请广大读者批评指正。

编 者

Lesson 1 Basic Concepts in Mechanics

The branch of scientific analysis which deals with motions，time，and forces is called mechanics and is made up of two parts，statics and dynamics.Statics deals with the analysis of stationary systems，i.e.，those in which time is not a factor，and dynamics deals with systems which change with time.

When a number of bodies are connected together to form a group or system，the forces of action and reaction between any two of the connecting bodies are called constraint forces.These forces constrain the bodies to behave in a specific manner.Forces external to this system of bodies are called applied forces.

Electric，magnetic，and gravitational forces are examples of forces that may be applied without actual physical contact.A great many，if not most，of the forces with which we shall be concerned occur through direct physical or mechanical contact.^［1］

Forces are transmitted into machine members through mating surfaces，e.g.，from a gear to a shaft or from one gear through meshing teeth to another gear，from a V belt to a pulley，or from a cam to a follower.It is necessary to know the magnitudes of these forces for a variety of reasons.The distribution of the forces at the boundaries or mating surfaces must be reasonable，and their intensities must be within the working limits of the materials composing the surfaces.For example，if the force operating on a journal bearing becomes too high，it will squeeze out the oil film and cause metal to metal contact，overheating，and rapid failure of the bearing.^［2］ If the forces between gear teeth are too large，the oil film may be squeezed out from between them.This could result in flaking and spalling of the metal，noise，rough motion，and eventual failure.In the study of mechanics we are principally interested in determining the magnitude，direction，and location of the forces.

Some of the terms used in mechanics are defined below.

Force Our earliest ideas concerning forces arose because of our desire to push，lift，or pull various objects.So force is the action of one body on another.Our intuitive concept of force includes such ideas as place of application，direction，and magnitude，and these are called the characteristics of a force.

Mass is a measure of the quantity of matter that a body or an object contains.The mass of the body is not dependent on gravity and therefore is different from but proportional to its weight.Thus，a moon rock has a certain constant amount of substance，even though its moon weight is different from its earth weight.This constant amount of substance is called the mass of the rock.

Inertia is the property of mass that causes it to resist any effort to change its motion.

Weight is the force with which a body is attracted to the earth or another celestial body，equal to the product of the object\'s mass and the acceleration of gravity.

Particle A particle is a body whose dimensions are so small that they may be neglected.

Rigid Body A rigid body does not change size and shape under the action of forces.Actually，all bodies are either elastic or plastic and will be deformed if acted upon by forces.When the deformation of such bodies is small，they are frequently assumed to be rigid，i.e.，incapable of deformation，in order to simplify the analysis.A rigid body is an idealization of a real body.

Deformable Body The rigid body assumption cannot be used when internal stresses and strains due to the applied forces are to be analyzed.Thus we consider the body to be capable of deforming.Such analysis is frequently called elastic body analysis，using the additional assumption that the body remains elastic within the range of the applied forces.

Newton\'s Laws of Motion Newton\'s three laws are：

Law 1 If all the forces acting on a body are balanced，the body will either remain at rest or will continue to move in a straight line at a uniform velocity.

Law 2 If the forces acting on a body are not balanced，the body will experience an acceleration.The acceleration will be in the direction of the resultant force，and the magnitude of the acceleration will be proportional to the magnitude of the resultant force and inversely proportional to the mass of the body.

Law 3 The forces of action and reaction between interacting bodies are equal in magnitude，opposite in direction，and have the same line of action.

Mechanics deals with two kinds of quantities：scalars and vectors.Scalar quantities are those with which a magnitude alone is associated.Examples of scalar quantities in mechanics are time，volume，density，speed，energy，and mass.Vector quantities，on the other hand，possess direction as well as magnitude.Examples of vectors are displacement，velocity，acceleration，force，moment，and momentum.

Words and Expressions

mechanics［miˌkæniks］n.力学

statics［ˌstætiks］n.静力学，静止状态

dynamics［daiˌnæmiks］n.动力学，原动力，动力特性

i.e.那就是，即（=that is）

gravitational［ˌgræviˌteiʃnəl］a.重力的

mating［ˌmeitiŋ］n.；a.配合（的），配套（的），相连（的）

mating surface 啮合表面，配合表面，接触表面

e.g.例如（=for example）

gear［giə］n.齿轮，齿轮传动装置

shaft［ʃa：ft］n.轴

meshing［ˌmeʃiŋ］n.啮合，咬合，钩住

bearing［ˌbεəriŋ］n.轴承，支承，承载

leverˌ[liːvə或ˌlevə]n.杠杆，操纵杆，手柄，把手

pulleyˌ[puli]n.滑轮，皮带轮，滚筒

cam［kæm］n.凸轮，偏心轮，样板，靠模，仿形板

magnitudeˌ[mægnitjuːd]n.大小，尺寸，量度，数值

compose［kəmˌpəuz］v.组成，构成

journal bearing 滑动轴承，向心滑动轴承

squeeze[skwiːz]v.挤压，压缩；n.压榨，挤压

squeeze out 挤压，压出

flakingˌ[fleikiŋ]n.薄片，表面剥落，压碎；a.易剥落的

spall[spɔːl]v.削，割，打碎，剥落，脱皮；n.裂片，碎片

noncoincident［ˌnɔnkəuˌinsidənt］a.不重合的，不一致的，不符合的

parallelˌ[pærəlel]a.并行的，平行的，相同的；n.平行线

resultant［riˌzʌltənt］a.合的，组合的，总的；n.合力，合成矢量，组合

coupleˌ[kʌpl]n.力偶，力矩

perpendicular[ˌpəːpənˌdikjulə]a.垂直的；n.垂直，正交，垂线

inertia[iˌnəːʃjə]n.惯性，惯量，惰性，不活动

celestial［siˌlestʃəl］a.天空的，天体的

incapable［inˌkeipəbl］a.无能力的，不能的，无用的，无资格的

deformation[ˌdiːfɔːˌmeiʃən]n.变形，形变，扭曲，应变

deformable[diˌfɔːməbl]a.可变形的，应变的

acceleration[ækˌseləˌreiʃən]n.加速度，加速度值，促进，加快

sense［sens］n.；v.感觉，检测，显示，方向

scalarˌ[skeilə]n.；a.数量（的），标量（的）

momentˌ[məumənt]n.力矩，弯矩

momentum［məuˌmentəm］n.动量，冲量

Notes

1.be concerned with 意为“涉及，与……有关”，physical contact意为“实际接触，直接接触”。全句可译为：与我们有关的力，即使不是大多数的话，也有很多是通过直接的实际接触或机械接触而产生的。

2.operate on 意为“对……起作用，影响”。全句可译为：如果作用在滑动轴承上的力太大，它将会把油膜挤出，造成金属与金属的直接接触，产生过热和轴承的快速失效。

Lesson 2 Forces and Their Effects

A study of any machine or mechanism shows that each is made up of a number of movable parts.These parts transform a given motion to a desired motion.In other words，these machines perform work.Work is done when motion results from the application of force.^［1］ Thus，a study of mechanics and machines deals with forces and the effects of forces on bodies.

A force is a push or pull.The effect of a force either changes the shape or motion of a body or prevents other forces from making such changes.Every force produces a stress in the part on which it is applied.Forces may be produced by an individual using muscular action or by machines with mechanical motion.

Forces are produced by physical or chemical change，gravity，or changes in motion.When a force is applied which tends to stretch an object，it is called a tensile force.A part experiencing a tensile force is said to be in tension.A force can also be applied which tends to shorten or squeeze the object.Such a force is a compressive force.

A third force is known as a torsional force，or a torque since it tends to twist an object.Still another kind of force，which seems to make the layers or molecules of a material slide or slip on one another，is a shearing force.

Each of these forces may act independently or in combination.For example，a downward force applied on a vertical steel beam tends to compress the beam.If this beam is placed in a horizontal position and a load is applied in the middle，the bottom of the beam tends to stretch and is in tension.At the same time，the top area is being pushed together in compression.

The turning of a part in a lathe is another example of several forces in action（as shown in Fig.2.1）.^［2］ As the work revolves and the cutting tool moves into the work，the wedging action of the cutting edge produces a shear force.This force causes the metal to seem to flow off the work in the form of chips.^［3］ If this workpiece is held between the two centers of the lathe，the centers exert a compressive force against the work.^［4］ The lathe dog which drives the work tends to produce a shearing force.The pressure of the cutting tool against the work produces tension and compression，as well as a shearing action.

Figure 2.1 Cylindrical turning operation in a lathe

Considerable attention is given to the action of centrifugal force in grinding wheels.That is，the bonding agent that holds the abrasive particles on the wheel must be stronger than the forces which tend to make the revolving wheel fly apart at high speeds.For this reason，the speed of a grinding wheel should not exceed the safe surface speed limit specified by the manufacturer.Centrifugal force increases with speed.

The principles of centrifugal force are used in the design of centrifuge-type machines.Some centrifuges are used to separate chemicals；others are used to remove impurities in metals by centrifugal casting processes.Centrifugal force principles are also used in common appliances such as clothes dryers and in devices to control motor speeds.

Centripetal force causes an object to travel in circular path.This action is caused by the continuous application of forces which tend to pull the object to the center.In other words，the inward force which resists the centrifugal for

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