机械工程专业英语课件L01.ppt

1、课件1English for Mechanical Engineering机械工程专业英语常州工学院机电工程学院徐红丽课件2机械工程专业英语机械工程专业英语预备知识预备知识 一、一、Background InformationCHAPTER 1 MATERIALS AND HOT WORKLesson 1 Basic Concepts in MechanicsIn rational mechanics,mechanical work is the amount of energy transferred by a force acting through a distance.Like ene

2、rgy,it is a scalar quantity,with SI units of joules.The term work was first coined in the 1830s by the French mathematician Gaspard-Gustave Coriolis.The mechanical work applied to an object can be calculated from the dot product of the applied force(F)and the displacement(d)of the object.n Work：Inte

3、rnational System of Units(SI)课件3机械工程专业英语机械工程专业英语 一、一、Background InformationLesson 1 Basic Concepts in MechanicsA baseball pitcher does positive work on the ball by transferring energy into it.预备知识预备知识课件4机械工程专业英语机械工程专业英语 一、一、Background InformationLesson 1 Basic Concepts in MechanicsnEfficiencyMechani

4、cal Efficiency is the ratio of work input to work output.It is often expressed as a percentage.The efficiency of an ideal machine is 100%but an actual machines efficiency will always be less than 100%because of the Second law of thermodynamics which states that the quality of energy will decay,event

5、ually becoming heat.This means that some of the work put into the system is transformed(lost)into thermal energy(heat).In a mechanical system,friction is the most common cause of the work lost to heat.预备知识预备知识课件5机械工程专业英语机械工程专业英语 一、一、Background InformationLesson 1 Basic Concepts in MechanicsnMechanic

6、al AdvantageIn physics and engineering,mechanical advantage(MA)is the factor by which a mechanism multiplies the force or torque put into it.Generally,the mechanical advantage is calculated as follows:or more simply:预备知识预备知识课件6nMechanical Advantage：机械工程专业英语机械工程专业英语Lesson 1 Basic Concepts in Mechanic

7、s预备知识预备知识课件7nMechanical Advantage：机械工程专业英语机械工程专业英语Lesson 1 Basic Concepts in Mechanics预备知识预备知识课件8机械工程专业英语机械工程专业英语词词 汇汇Lesson 1 Basic Concepts in Mechanics 二、二、Words and Expressionsmechanics mikniks n.机械学，力学机械学，力学.abbr.mech.modify mCdifai v.修改，调解，变更修改，调解，变更manageable 5mAnidVEbl adj.可控制的、易处理的、便于可控制的、易

8、处理的、便于管理的管理的incline in5klain vt.（使）倾斜（使）倾斜 vi.倾斜，倾向倾斜，倾向 n.倾斜，倾斜，斜坡，斜面斜坡，斜面ramp rAmp n.斜板斜板,斜坡斜坡,敲诈敲诈vi.狂跳乱撞狂跳乱撞,敲诈敲诈,蔓延蔓延 vt.使有斜面使有斜面,敲诈敲诈slope slEup n.斜坡斜坡,斜面斜面,倾斜倾斜 v.(使使)顺斜顺斜 ramp slope 斜坡坡度斜坡坡度课件9机械工程专业英语机械工程专业英语Lesson 1 Basic Concepts in Mechanics 二、二、words and Expressionsfriction 5frikFEn n.摩

9、擦摩擦,摩擦力摩擦力roll 5rEul vt.滚动滚动,滚转滚转,(使使)摇摆摇摆,(使使)摇晃摇晃,卷起卷起,卷拢卷拢,辗辗,轧轧 n.卷卷,卷形物卷形物,摇晃摇晃,摆动摆动,名单名单multiplier 5mQltiplaiE n.放大器，乘法放大器，乘法broom bru:m n.扫帚扫帚 植植金雀花金雀花 vt.扫除扫除 broomcorn 高粱高粱 broomrape 肉苁蓉肉苁蓉 A new broom sweeps clean 新官上任三把火新官上任三把火convert kn5vE:t n.皈依者皈依者 vt.使转变使转变,转换转换.,使使.改变信改变信仰仰handle 5hA

10、ndl n.手柄手柄 vt.触摸触摸,运用运用,买卖买卖,处理处理,操作操作 n.计计句柄句柄 词词 汇汇课件10机械工程专业英语机械工程专业英语Lesson 1 Basic Concepts in Mechanics 二、二、words and Expressionssweep swi:p v.清扫清扫,席卷席卷,掠过，斜坡，斜面掠过，斜坡，斜面efficiency i5fiFEnsi n.效率，功效效率，功效 efficient adj.efficiently adv.gauge geIdV v.测量，校验测量，校验 n.标准尺标准尺,规格规格,量规量规,量表量表bearing 5bZEr

11、iN n.轴承轴承,关系关系,方面方面,意义意义,方向方向ideal mechanical advantage d5va:ntidV 理想的机械理想的机械效益效益 neglect ni5glekt vt.忽略，忽视忽略，忽视 n.neglect of duty 疏于职疏于职守守 negligible 5neglidVEbl adj.可以忽略的，不予重视可以忽略的，不予重视的的词词 汇汇课件11 Work is defined as force multiplied by the distance over which the force acts.Work is measured in met

12、re-kilograms.A metre-kilogram equals the work done by a force of one kilogram acting through a distance of one metre.For example,if a work task involves lifting a 300 kilogram machine two and one half metres into a truck,then 750 metre kilograms of work is required.Since no humans can lift 300 kilog

13、rams directly,a device must be employed to modify the required effort into something manageable.机械工程专业英语机械工程专业英语Lesson 1 Basic Concepts in Mechanics课文分析课文分析课件12机械工程专业英语机械工程专业英语Work is defined as force multiplied by the distance over which the force acts.Work is measured in metre-kilograms.功的定义是力乘以沿力

14、的作用方向物体移动的距离。功的定义是力乘以沿力的作用方向物体移动的距离。功的单位用公斤功的单位用公斤米来表示。米来表示。Lesson 1 Basic Concepts in Mechanics A metre-kilogram equals the work done by a force of one kilogram acting through a distance of one metre.l l公斤公斤米等于米等于1 1公斤力作用于物体上使物体移动公斤力作用于物体上使物体移动l l米的距离所作的功。米的距离所作的功。课文分析课文分析课件13机械工程专业英语机械工程专业英语For ex

15、ample,if a work task involves lifting a 300 kilogram machine two and one half metres into a truck,then 750 metre kilograms of work is required.例如，一项任务需要将一台例如，一项任务需要将一台300公斤重的设备提升到公斤重的设备提升到2.5米高的卡车上，那么就需要做米高的卡车上，那么就需要做750公斤公斤米的功米的功。Since no humans can lift 300 kilograms directly,a device must be empl

16、oyed to modify the required effort into something manageable.Lesson 1 Basic Concepts in Mechanics课文分析课文分析由于没有人能直接举起由于没有人能直接举起300公斤的重物，因此必须公斤的重物，因此必须使用一种设备将所需的作用力转变成人力所能及的。使用一种设备将所需的作用力转变成人力所能及的。课件14机械工程专业英语机械工程专业英语One common device is an inclined plane-in this case,a loading ramp that slopes from th

17、e ground to the truck,If the ramp were 10 metres long and friction forces were negligibly small,then 75 kilograms of force would be required to roll the machine up the ramp.The total work is still 750 metre-kilograms(10 metres multiplied by 75 kilograms),but the effort has been modified so that the

18、maximum force required is only 75 kilograms.Lesson 1 Basic Concepts in Mechanics课文分析课文分析课件15机械工程专业英语机械工程专业英语One common device is an inclined plane-in this case,a loading ramp that slopes from the ground to the truck,If the ramp were 10 metres long and friction forces were negligibly small,then 75 ki

19、lograms of force would be required to roll the machine up the ramp.Lesson 1 Basic Concepts in Mechanicsneglidbladj.可以忽略的可以忽略的;无足轻重的无足轻重的;课文分析课文分析常用的装置是一个斜面常用的装置是一个斜面-在这个例在这个例子中，一个倾斜在地面和卡车之间的子中，一个倾斜在地面和卡车之间的承载斜板，如果斜板有承载斜板，如果斜板有1010米长，摩擦米长，摩擦力很小可忽略不计的话力很小可忽略不计的话 ，那么就只，那么就只需要需要7575公斤的力将机器滚上斜板。公斤的力将机器滚上

20、斜板。课件16机械工程专业英语机械工程专业英语The total work is still 750 metre-kilograms(10 metres multiplied by 75 kilograms),but the effort has been modified so that the maximum force required is only 75 kilograms.Lesson 1 Basic Concepts in Mechanics总功仍然是总功仍然是750750公斤公斤米米(用用7575公斤乘以公斤乘以1010米米)，但，但作用力已经被改变，于是其所需的最大外力仅仅作

21、用力已经被改变，于是其所需的最大外力仅仅是是7575公斤。公斤。课文分析课文分析课件17 A device that decreases the necessary applied force while increasing the distance over which the smaller force acts is called a force multiplier.Machines can also multiply speed and distance.A broom is an example of a speed and distance multiplier because

22、 it converts input force and distance at the handle into a lower force and larger distance at the sweeping end.Since the larger distance at the sweeping end is covered in the same time as the input distance,then the speed is also increased.In addition to modifying forces and distances,machines can a

23、lso change the direction of motion.机械工程专业英语机械工程专业英语Lesson 1 Basic Concepts in Mechanics课文分析课文分析课件18机械工程专业英语机械工程专业英语A device that decreases the necessary applied force while increasing the distance over which the smaller force acts is called a force multiplier.使所需的作用力减少，同时这个较小的作用力使所需的作用力减少，同时这个较小的作用力

24、使所通过的距离增加，这样的装置被称为力放使所通过的距离增加，这样的装置被称为力放大器（省力器）。大器（省力器）。Machines can also multiply speed and distance.机器装置也可放大速度和距离。机器装置也可放大速度和距离。Lesson 1 Basic Concepts in Mechanics课文分析课文分析课件19机械工程专业英语机械工程专业英语A broom is an example of a speed and distance multiplier because it converts input force and distance at t

25、he handle into a lower force and larger distance at the sweeping end.扫帚就是一个速度和距离放大器的扫帚就是一个速度和距离放大器的例子。因为它把在手柄上输入的力例子。因为它把在手柄上输入的力和距离，在扫帚的尾部转变成较小和距离，在扫帚的尾部转变成较小的力和较长的距离。的力和较长的距离。Lesson 1 Basic Concepts in Mechanics课文分析课文分析课件20机械工程专业英语机械工程专业英语Since the larger distance at the sweeping end is covered in

26、 the same time as the input distance,then the speed is also increased.由于在相同的时间里扫帚的尾部比输入端走过距离由于在相同的时间里扫帚的尾部比输入端走过距离大，因此尾部的速度也就增加了。大，因此尾部的速度也就增加了。In addition to modifying forces and distances,machines can also change the direction of motion.机械装置除了能放大力和距离之外，也能改变运机械装置除了能放大力和距离之外，也能改变运动的方向。动的方向。Lesson 1

27、Basic Concepts in Mechanics课文分析课文分析课件21 Efficiency and mechanical advantage are used to gauge the performance of mechanical machines.Efficiency is defined as the useful mechanical output work,expressed as a percentage of the input work.Efficiency is always less than 100 percent because of friction b

28、etween moving parts.If someone actually wheeled the machine of the initial example up the ramp,they might discover that it required 84 kilograms.The nine kilograms difference is the force required to overcome the resistance of the wheels and bearings.Under these conditions the machine would have an

29、efficiency of 89 percent.机械工程专业英语机械工程专业英语Lesson 1 Basic Concepts in Mechanics课文分析课文分析课件22机械工程专业英语机械工程专业英语Efficiency and mechanical advantage are used to gauge the performance of mechanical machines.效率和机械效益是用来衡量机械装置性能的。效率和机械效益是用来衡量机械装置性能的。Efficiency is defined as the useful mechanical output work,exp

30、ressed as a percentage of the input work.效率定义为输出的有用的机械功占输入功的百分效率定义为输出的有用的机械功占输入功的百分率来表示。率来表示。Lesson 1 Basic Concepts in Mechanics课文分析课文分析课件23机械工程专业英语机械工程专业英语Efficiency is always less than 100 percent because of friction between moving parts.效率总是要低于效率总是要低于100，因为相对运动零件之间存在摩，因为相对运动零件之间存在摩擦。擦。If someone

31、 actually wheeled the machine of the initial example up the ramp,they might discover that it required 84 kilograms.像开始所举的那部机器的例子那样，如果有人真的把该像开始所举的那部机器的例子那样，如果有人真的把该机器滚上斜板，他们可能发现那要花机器滚上斜板，他们可能发现那要花84公斤的力。公斤的力。Lesson 1 Basic Concepts in Mechanics课文分析课文分析课件24机械工程专业英语机械工程专业英语The nine kilograms difference

32、 is the force required to overcome the resistance of the wheels and bearings.这这9公斤力的差额就是用于克服滚轮和轴承之间阻公斤力的差额就是用于克服滚轮和轴承之间阻力。力。Lesson 1 Basic Concepts in MechanicsUnder these conditions the machine would have an efficiency of 89 percent.在这种情况下该机械装置将只有在这种情况下该机械装置将只有89的效率。的效率。课文分析课文分析课件25 If they slid th

33、e refrigerator up the ramp without wheels,the required force could be 215 kilograms or more,which corresponds to an efficiency of less than 35 percent.Ideal mechanical advantage neglects friction and is equal to the distance the input force travels divided by the useful distance the load travels.For

34、 force multiplying machines,the input distance is greater than the load distance and the ideal mechanical advantage is greater than 1.In the loading ramp example,the ideal mechanical advantage is 4,since the input distance is 10 metres(the length of the ramp)and the useful load distance is two and o

35、ne-half metres(the vertical distance the load travels).机械工程专业英语机械工程专业英语Lesson 1 Basic Concepts in Mechanics课文分析课文分析课件26机械工程专业英语机械工程专业英语If they slid the refrigerator up the ramp without wheels,the required force could be 215 kilograms or more,which corresponds to an efficiency of less than 35 percent

36、.如果在没有滚轮情况下，把冰箱滑上斜板，所需的如果在没有滚轮情况下，把冰箱滑上斜板，所需的力可能是力可能是215公斤或更大，那么相应的机械效率就公斤或更大，那么相应的机械效率就小于小于35。Lesson 1 Basic Concepts in Mechanics课文分析课文分析课件27机械工程专业英语机械工程专业英语Ideal mechanical advantage neglects friction and is equal to the distance the input force travels divided by the useful distance the load tra

37、vels.理想的机械效益是忽略摩擦损失，等于输入力移理想的机械效益是忽略摩擦损失，等于输入力移动的距离除以负载移动的有效距离。动的距离除以负载移动的有效距离。Lesson 1 Basic Concepts in Mechanics For force multiplying machines,the input distance is greater than the load distance and the ideal mechanical advantage is greater than 1.对于力放大装置，输入的距离要比负载的距离大，因对于力放大装置，输入的距离要比负载的距离大，因而

38、理想的机械效益是比而理想的机械效益是比1要大的。要大的。课文分析课文分析课件28机械工程专业英语机械工程专业英语In the loading ramp example,the ideal mechanical advantage is 4,since the input distance is 10 metres(the length of the ramp)and the useful load distance is two and one-half metres(the vertical distance the load travels).在承载斜板例子中，该理想机械效益是在承载斜板例

39、子中，该理想机械效益是4，因为该输，因为该输入距离是入距离是10米米(斜板长度斜板长度)，而有效负载移距是，而有效负载移距是25米米(该负载移动的垂直距离该负载移动的垂直距离)。Lesson 1 Basic Concepts in Mechanics课文分析课文分析课件29 An inclined plane is always a force multiplying machine.For speed-multiplying machines the input distance is less than the load distance and the ideal mechanical

40、advantage is less than 1.Machines that simply change the direction of motion have an ideal mechanical advantage equal to 1.The actual mechanical advantage includes friction and is equal to the actual output force divided by the actual input force.The actual mechanical advantage in the loading ramp e

41、xample is about 3.6 with wheels and about 1.4 without wheels.机械工程专业英语机械工程专业英语Lesson 1 Basic Concepts in Mechanics课文分析课文分析课件30机械工程专业英语机械工程专业英语An inclined plane is always a force multiplying machine.斜面就是一个力放大装置。斜面就是一个力放大装置。Lesson 1 Basic Concepts in Mechanics For speed-multiplying machines the input d

42、istance is less than the load distance and the ideal mechanical advantage is less than 1.对于速度放大装置，输入距离要比负载距离小，对于速度放大装置，输入距离要比负载距离小，而理想的机械效益亦比而理想的机械效益亦比1要小。要小。课文分析课文分析课件31机械工程专业英语机械工程专业英语Machines that simply change the direction of motion have an ideal mechanical advantage equal to 1.仅仅改变运动方向的机器装置具有一

43、个等于仅仅改变运动方向的机器装置具有一个等于l的理想的理想机械效益。机械效益。Lesson 1 Basic Concepts in Mechanics The actual mechanical advantage includes friction and is equal to the actual output force divided by the actual input force.实际机械效益包括了摩擦损失并等于实际输出实际机械效益包括了摩擦损失并等于实际输出力除以实际输入力。力除以实际输入力。课文分析课文分析课件32机械工程专业英语机械工程专业英语The actual mechanical advantage in the loading ramp example is about 3.6 with wheels and about 1.4 without wheels.在承载斜板例子中的实际机械效益在有滚子条件在承载斜板例子中的实际机械效益在有滚子条件下，大约是下，大约是3.63.6，无滚子条件下，大约是，无滚子条件下，大约是1.41.4。Lesson 1 Basic Concepts in Mechanics课文分析课文分析