Lesson 2 force and their effects

1、UNIT 3Lesson 2 Forces and Their Effects Terminology Text tour 2022-5-131机械工程专业英语教程Words and ExpressionsWords and ExpressionsTerminology2022-5-135机械工程专业英语教程 Compressive Serving to or able to compress 压缩的：起压缩作用或能够压缩的 Turning The shaping of metal or wood on a lathe 车削：用车床将金属或木材加工成型的过程 Lathe 车床机械工程专业英语教

2、程2022-5-13RectilinearMoving in, consisting of, bounded by, or characterized by a straight line or lines:直线的：以直线运动的，由直线组成的，以直线为边的，具有直线之特点的 micrometer 千分尺 6 2022-5-137机械工程专业英语教程Thread A helical or spiral ridge on a screw, nut, or bolt 螺纹：螺钉、螺母或螺栓上螺旋型的凸棱Shaper牛头刨床A study of any machine or mechanism sho

3、ws 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. Thus, a study of mechanics and machines deals with forces and the effects of fo

4、rces on bodies.机械研究表明，所有的机器都是由大量活动件构成的。这些构件将给定的运动转化为所需要的运动形式。换句话说，这些机器在工作。在力的作用下，机器才能进行工作。因而，力学和机械学是研究力以及其对物体作用的。 机械工程专业英语教程2022-5-13Text tour8 A force is a push or pull. The effect of a force either changes the shape or motion of a body or prevent other forces from making such changes. Every force

5、produces a stress in the part on which it is applied. Forces may be produced by an individual using muscular action or by m a c h i n e s w i t h m e c h a n i c a l m o t i o n . 力有推力和拉力之分。力或改变物体的外形或运动形式或防止诸如此类的变化。每个力都会在其作用的物体上产生应力。不论 是 人 为 的 动 作 或 是 机 器 的 机 械 运 动 都 可 能 产 生 力 。 机械工程专业英语教程2022-5-139

6、 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 s q u e e z

7、e t h e o b j e c t . S u c h a f o r c e i s a compressive force. 物理或化学反应，地心引力的吸引，或是机器运转形式的变化都会产生力。拉伸物体的力称作拉力。我们认为拉力作用的物体，承受拉应力。力也可以缩短或挤压一个物体，这样的力称作压力。 机械工程专业英语教程2022-5-1310 A third force is known as a torsional force, or a torque since it tends to twist an object. Still another kind of force, whic

8、h seems to make the layers or molecules of a material slide or slip on one another, is a shearing force. 第三种力因为它有使扭转物体的趋向，称为扭转力或是扭矩 。还有另外一种使材料截面层发生滑移的力，称为剪切力。机械工程专业英语教程2022-5-1311Each of these forces may act independently or in combination. For example, a downward force applied on a vertical steel b

9、eam 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. If the compressive and tensile forces are greater en

10、ough to make the layers of the material slide upon each other, a shearing force results. 各种力可能单独或者结合在一起对物体产生作用。 例如，对一个竖直放置的横梁施加一个向下的力会压缩横梁。如果在水平放置横梁的中间部位施加负载，那么横梁的底端拉伸，正承受拉应力。同时，横梁的顶部在压应力的作用下压缩聚集。如果压力和拉力大小能够使得使材料层截面发生滑移，则剪切力产生。The turning of a part in a lathe is another example of several forces in

11、action (as shown in Figure 1).1turning of a part 这里指“对一个零件进行车削加工”。1. 全句译为：几个力同时作用的另外的一个例子是在车床上 对 零 件 进 行 车 削 加 工 （ 如 图 1 所 示 ） 。机械工程专业英语教程2022-5-13Fig. 1 The turning of a part in a lathe 13As the work revolves and the cutting tool moves into the work, the wedging action of the cutting edge produces

12、a shear force. This force causes the metal to seem to flow off t h e w o r k i n t h e f o r m o f c h i p s . 2 2. chip 这里指“切屑”。work 这里指“工件，即 workpiece ”。全句可译为：这个力使得金属看起来像以切屑的形式从工件上流出来一样。If this workpiece is held between the centers of the lathe, the centers exert a compressive force against the wo

13、rk.33. centers of the lathe 意为“车床的两个顶尖”。全句可译为：如果一个工件被安装在车床的两个顶尖之间，顶尖对工件施加一个压力。机械工程专业英语教程2022-5-1314The 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.控制工件的车床夹头给工件一个剪切力

14、。切削工具给工件的压力产生了拉伸，压缩和剪切作用。机械工程专业英语教程2022-5-1315Considerable 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 spe

15、eds. 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.要注意砂轮的离心力作用。即砂轮上磨料粒子与粘合剂的粘合强度，一定要高于，高速旋转的砂轮对其产生的离心力。正因如此，砂轮的转速一定不能超过供应商注明的表面安全速 度 极 限 。 速 度 提 高 ， 离 心 力 增 大 。机械工程专业英语教程2022-5-1316T

16、he principles of centrifugal force are used in design of centrifuge-type machines. Some centrifuges are used to separate chemicals; others are used to remove impurities in metal by centrifugal casting processes. Centrifugal force principles are also used in common appliances such as clothes dryers a

17、nd in devices to control motor speeds and accelerate moving machines.离心机的设计利用了离心力原理。一些离心机用来分离化学物质；有些在铸造时通过离心铸造法来去除金属中的杂质。离心力原理在普通设备中也有应用，例如，衣物甩干机，通过 控 制 设 备 中 电 机 的 转 速 为 运 动 件 加 速。机械工程专业英语教程2022-5-1317Centripetal force causes an object to travel in circular path. This action is caused by the contin

18、uous application of forces which tend to pull the object to the center. In other words, the inward force which resists the centrifugal force is called the centripetal force. The centripetal force of objects spinning at a constant rate produces an acceleration toward the center which is equal a n d o

19、 p p o s i t e t o t h e c e n t r i f u g a l f o r c e .向心力使得物体作圆周运动。将物体拉向中心的力，使物体进行圆周运动。换句话说，抵抗离心力作用并指向物体内部的力称为向心力。向心力使匀速圆周运动的物体产生了一个向心加速度，离心力与向心力大小相等方向相反。机械工程专业英语教程2022-5-1318The materials used in the construction of rapidly moving machine parts and mechanisms must be structurally strong enough

20、to provide the centripetal force required to hold the parts to a circular path. At the same time, the materials must be able to withstand the centrifugal force which rends to pull the parts apart. 零件进行圆周运动必须要有向心力作用，因此高速运转的机器零件和机械装置所使用的材料的结构强度，必须能够保证该向心力。同时，材料强度也必须能够承受离心力的作用。机械工程专业英语教程2022-5-1319Moti

21、on and the basic laws which affect motion are important considerations because of the numerous applications of these principles to produce work through mechanical devices. There are two primary mechanical motions: rotary and rectilinear. These terms suggest that rotary motion is a circular movement

22、around a center line and rectilinear motion is a straight line motion. For either rotary or rectilinear motion, it is possible, with added mechanical devices, to produce other forms of motion such as intermittent motion and reciprocating motion.因为大多数机械运动原理和影响机械运动的基本规律的应用，都是通过机械设备实现生产工作的，因此这些原理要着重关注。

23、有两种基本的机械运动方式：回转运动和直线运动。这两种运动可理解为：回转运动是设备绕其中心线进行的圆周运动，直线运动是设备沿一条直线的运动。对更多的机械设备来说，不管是回转运动还是直线运动，可能会产生其他的运动形式像间歇运动和往复运动。机械工程专业英语教程2022-5-1320Rotary Motion. The motion that is commonly transmitted is rotary motion. This type of motion may be produced with hand tools or power tools. Rotary motion is requ

24、ired to drill holes, turn parts in a lathe, mill surfaces, or drive a generator or fan belt.4 4. rotary motion 意为“回转运动”。全句可译为：钻孔、在车床上车削零件、铣平面、驱动发电机或风扇的带等都需要回转运动。机械工程专业英语教程2022-5-1321Rectilinear Motion. The feed of a tool on a lathe, the cutting of steel on a power saw, or the shaping of materials ar

25、e all situations in which rectilinear or straight line motion produces work. In each of these situations a part or mechanism is used to change rotary motion to straight line motion. The screw of a micrometer and the threads in a nut are still other applications where the direction of motion is c h a

26、 n g e d f r o m r o t a r y t o r e c t i l i n e a r . 5 车床上车刀的进刀，电锯钢材的切削或者材料的刨削都是以直线或是直线运动方式加工工件。在以上的每一种方式中，零件或机械装置都将回转运动转变为直线运动。5. the screw of a micrometer 意为“千分尺中的螺杆”全句可译为：千分尺中的螺杆和螺母中的螺纹是把运动方向从转动变为直线的另外一些应用实例。机械工程专业英语教程2022-5-1322Harmonic and Intermittent Motion.6 Any simple vibration, such as the regular back-and-forth movement of the end of a pendulum, is simple harmonic motion.7 However, many manufacturing processes require intermittent or irregu