过程装备与控制工程专业英语第5单元ppt课件

1、合肥工业大学过程配备与控制工程专业Words and Expressionscontenttranslationexercisesexamples书本引见作者引见Process Equipment &Control EngineeringSpecialized English XXXXXXXXXXXXXXXXXX;Words and Expressions 1. oscillatory siltri a.振荡的，摆动的 2. confront knfrnt v.面临，面对(be confronted with) 3. wearw v. ; n.磨损，损耗，耐磨(性) 4. fatigu

2、e f ti: n. v.(使)疲劳;fatigue failure疲劳破坏(失效) 5. acute kju:t a.敏锐的，锋利的;Words and Expressions 6. impair imp vt.;n.损害伤)，减少(弱) 7. symmetrical simetrikl a.对称的，匀称的 8. propeller prupel n.螺旋桨，推进器 9. compact kmpkt, kmpkt v.压实，夯实;a.压紧的 10. chaff t:f, tf n.谷壳，废物，渣滓;Words and Expressions 11. thresh(=thrash) re v.

3、猛烈摆动，颠簸 12. glider laid n滑翔机 13. panel pnl n.底板，座，仪表板 14. helical helikl n.;a.螺旋(线，面，形)(的) 15. springboard sprib:d n跳板，出发点;Words and Expressions 16. pendulum pendjulm n.摆(锤)，振动体 17. bob bb n.振子球，秤锤 18. displacement displeismnt n.位移，平移，挪动(度) 19. customary kst,mri n.通常的，(符合)习惯的 20. reciprocal risiprkl

4、 a.相互的，倒数的;，.倒数，互逆;Words and Expressions 21. amplitudemplitju:d n.振幅，摆幅，幅度 22. angularjul adj.角(形，状)的，成角度的 23. dissipative disipeitiv a.损耗的，耗费(性)的 24. damp dmp v.阻尼，减振，弄湿 25. viscous visks adj.粘性的，粘滞的;Words and Expressions 26. constrain knstrein vt.约束，束缚，强迫 27. coordinate ku:dinit, ku:dineit n坐标(系);

5、a.坐标的，同位的 28. specify spesfai vt.指定，确定，详细阐明;Unit 5 Mechanical Vibrations A mechanical vibration is an oscillatory，periodically repeated motion of a particle or body about a position of equilibrium .An engineer is frequently confronted with the problem of machinery and structures.original text;Unit 5

6、 Mechanical Vibrations 机械振动是质点或物体在其平衡位置附近所作的震荡的，周期性的往复运动。 工程师经常面临机械振动的问题，由于在某种程度上他们在几乎一切的机械和构造中遇到过这些问题translated text;Unit 5 Mechanical Vibrations Most vibrations are undesirable in machines and structures because they produce excessive stresses or repeated stresses;original text;Unit 5 Mechanical V

7、ibrations 大多数的震动在机械和构造中是不希望存在的，由于震动会产生附加应力或者交变应力。translated text;Unit 5 Mechanical Vibrations cause added wear;increase bearing loads; induce fatigue;create acute passenger discomfort in planes，ships，trains，buses，and automobiles;and absorb energy that could otherwise do useful work.original text;Uni

8、t 5 Mechanical Vibrations 引起额外磨损，增大轴承载荷，导致疲劳破坏，使飞机、船、火车及汽车上的乘客产生严重的不温馨感，并且振动会吸收本可以做有用功的能量。translated text;Unit 5 Mechanical Vibrations The collapse of the Tacoma Narrows Bridge in 1940 is an example of structural failure due to excessive stresses produced by vibrations. The accuracy of precision ins

9、truments，tools，and machines may be impaired by excessive vibrations. original text;Unit 5 Mechanical Vibrations 1940年发生的塔克马窄桥的垮塌事件就是一个由于震动产生的附加应力导致构造失效的例子。 精细仪器、工具和电脑的准确性能够被附加的震动所损坏 translated text;Unit 5 Mechanical Vibrations Rotating machine parts require careful balancing in order to prevent dama

10、ge from vibrationoriginal text;Unit 5 Mechanical Vibrations 旋转机械零件需求仔细的平衡,以防止振动的呵斥的损伤。translated text;Unit 5 Mechanical Vibrations When part of the propeller of an airplane is shot off or breaks off in flight the propeller is no longer symmetrical，and the vibrations from the engine may tear the engi

11、ne from the plane unless it can be stopped in time.original text;Unit 5 Mechanical Vibrations 当飞机的螺旋桨的某部分在飞行中被打掉或断裂，这时螺旋桨不再是对称的，来自引擎的振动会把引擎从飞机上扯下来,除非它可以被及时的停顿。translated text;Unit 5 Mechanical Vibrations The vibrations produced in an automobile by the engine or by driving on rough roads set up repea

12、ted stresses in certain parts that can eventually lead to fatigue failure of the members.original text;Unit 5 Mechanical Vibrations 由引擎产生的震动或由于在崎岖的道路上行驶产生的震动施加在某部分的交变应力最终会使其发生疲劳失效translated text;Unit 5 Mechanical Vibrations When a particle or body that is supported by a system of springs，a shaf t，a

13、beam，or any other elastic system is disturbed from its position of equilibrium by the application and sudden removal of an additional force the particle or body will vibrate. original text;Unit 5 Mechanical Vibrations 当被弹簧，杆，线或者其他弹性系统支撑的质点或物体，在被干扰或者遭到外力的作用使其偏离平衡位置，质点或物体就会发生震动。translated text;Unit 5

14、Mechanical Vibrations Some common example are the vertical vibratory motion of body A in Fig.1.19.(a) when it is displaced vertically from its equilibrium position on a helical spring and then released ; original text;Unit 5 Mechanical Vibrationstranslated text;Unit 5 Mechanical Vibrations the verti

15、cal vibratory motion of body B of Fig.1.19.(b) when it is displaced from its equilibrium position on a flexible springboard (cantilever beam) of negligible mass and released;original text;Unit 5 Mechanical Vibrationstranslated text;Unit 5 Mechanical Vibrations and the motion of the pendulum bob C in

16、 Fig.1.19.(c) as it swings in a vertical plane when supported by a cord of negligible massoriginal text;Unit 5 Mechanical Vibrationstranslated text;Unit 5 Mechanical Vibrations Fig .1 .20(a)shows a body W suspended from a support by a spring and hanging at its equilibrium position. If the body is pu

17、lled from its equilibrium position by a force F and released，it will，in the absence of any frictional forces，continue to oscillate about the equilibrium position indefinitely .original text;Unit 5 Mechanical Vibrations 图1.20 a中所示的物体W，悬挂弹簧上，处于平衡位置。当它在力F的作用下拉离平衡位置时被释放，在没有摩擦阻力时，它将在平衡位置附近做延续性不断地摆动。trans

18、lated text;Unit 5 Mechanical Vibrations Fig.1.20 (b)shows a graph of the displacement，y，of the body W from its equilibrium position as a function of time . One of the fundamental properties of mechanical vibrations is that the motion repeats itself at definite interval of time . The period ,T ,of th

19、e oscillation is the minimum amount of elapsed time before the motion starts to repeat itself . The motion completed in one period cycle . original text;Unit 5 Mechanical Vibrations 图1.20b 中所示为物体W偏离平衡位置的间隔y对时间的图像。机械振动的根本内容之一就是在一段时间内的反复运动。震动的周期，T，是它开场反复运动之前，运动时间的最小值。运动在一个周期内完成。translated text;Unit 5

20、Mechanical Vibrations The frequency，f，of the oscillation is the number of cycles which occur in a given unit of time ;the customary unit is cycles per second，cps，or hertz，Hz，It should be noted that the frequency is the reciprocal of the period，or，in equation form，f=1/Toriginal text;Unit 5 Mechanical

21、 Vibrations 震动的频率，f，是单位时间内所做的循环的次数。常用的单位是周期/秒，cps，赫兹，hz。值得留意的是，频率和周期是相互联络的或者说，用一个方程式f=1/T。translated text;Unit 5 Mechanical Vibrations The amplitude，A，of the oscillation is the maximum displacement，either linear or angular，of the body from its equilibrium position.original text;Unit 5 Mechanical Vib

22、rations 震动的振幅，A，是距其平衡位置震动的最大位移，不论是直线运动还是摆动。translated text;Unit 5 Mechanical Vibrations Mechanical vibrations which are maintained by elastic，and sometimes gravity，forces are called free vibrations. Once started，a free vibration，frequently called a natural vibration，continues to oscillate at its nat

23、ural frequency. original text;Unit 5 Mechanical Vibrations 被松紧带坚持的机械振动，有时同时在重力，及其他力的作用下被称作自在振动。一旦开场，自在振动经常被称作固有振动，延续的以它的固有频率摆动。translated text;Unit 5 Mechanical Vibrations A forced vibration is produced and maintained by a periodic exciting force external to the system，and it takes place at the freq

24、uency of the exciting force.If the system is nearly frictionless and contains no dissipative elements，the amplitude of the forced oscillation will become very large when the frequency of the exciting force is close to the natural frequency of the system.original text;Unit 5 Mechanical Vibrations 受迫振

25、动是振动系统在周期性的外力作用下产生并坚持的，并以外力的频率运动。假设系统是无摩擦的而且不包含任何能量损失，在驱动力的频率接近固有频率的时候是，受迫振动的振幅会变得越来越大。translated text;Unit 5 Mechanical Vibrations Thus, although the frequency of a forced vibration is independent of the natural frequency of the elastic system，the resulting amplitude is affected by both frequencies

26、. Vibrations are also classified as damped or undamped . When friction，air resistance，viscous damping，and all other resisting forces are negligible the vibration is undamped. original text;Unit 5 Mechanical Vibrations 因此，虽然受迫振动的频率和弹性系统的固有频率无关，但是产生的振幅却受这两个频率的影响。振动也可以分类为阻尼振荡和无阻尼振荡。当摩擦力，空气阻力，粘滞阻力，及其他阻力

27、可忽略时，这时的振动式无阻尼振动。translated text;Unit 5 Mechanical Vibrations When any of these effects is appreciable the body has damped vibrations. In practice there is always a frictional damping force which will eventually stop a free vibration，even though it may be neglected for many purposes.original text;Un

28、it 5 Mechanical Vibrations 当这些阻力中的任何一个不可忽略时，物体做阻尼振动。实践上，总有由摩擦力产生的阻尼力最终使自在振动停顿，即使这个力可以因某种目的被忽略。translated text;Unit 5 Mechanical Vibrations If the motion of a particle or body is constrained so that its position can be completely specified by one coordinate,it is said to have a single degree of freed

29、om. original text;Unit 5 Mechanical Vibrations 假设质点或物体的运动是被约束的，以致于它的位置完全可以用一个坐标表示，被称为具有单一的自在度。translated text;Unit 5 Mechanical Vibrations If the system can vibrate in two direction or is composed of two articles that can each vibrate independently in one direction, it is said to have two degrees of

30、 freedom because two coordinates are required to specify the position of the system at any instant. original text;Unit 5 Mechanical Vibrations 假设系统可以在两个方向振动，或者由可分别在一个方向上单独振动的两个运动组成的，那么被成为有两个自在度，由于恣意时辰的系统位置需求两个坐标指定。translated text;Unit 5 Mechanical Vibrations For example, a system composed by a spring as indicated in Fig.1.21(a), which vibrated in a vertical direction only, has one degree of freedom. original text;Unit 5 Mechanical Vibrations 例如，如图1.21(a)中，由一个弹簧组成的只在垂直方向上震动的系统，有一个自在度。translated text;Unit 5 Mechanical Vibrations A system composed of two part