土木工程专业英语翻译.docx

1、土木工程专业英语翻译Ch 2 Overview of Engineering MechanicsAs we look around us we see a world full of things: machines, devices, tools; things that we have designed, 当我们环顾四周，我们可以看到充满物质的世界：机器，仪器，工具：这些被我设计、建造和使用过 built and used; things made of wood, metals, ceramics, and plastics. We know from experience that s

2、ome 的东西： 这些东西是由木头，金属，陶瓷和塑料做成。我们从经验可以知道一些东西比别的东things are better than others; they last longer, cost less, are quieter, look better, or are easier to use.比别的东西好： 他们比较耐用，低成本，安静，看起来好点，或者使用比较简单。Ideally, however, every such item has been designed according to some set of functional requirements; as 不管怎么样

3、，最理想的是这样一个东西都是被设计者所认为的那样根据某些“使用要求”设计出来的。perceived by the designersthat is, it has been designed so as to answer the question, Exactly what function 也就是说他的设计是为了回答这些问题，确切的说它应该执行怎么样的功should it perform In the world of engineering, the major function frequently is to support some type of能 在工程的领域里，最主要的功能是

4、经常支持一些由于重力，惯性，压力等作用产 loading due to weight, inertia, pressure etc. From the beams in our homes to the wings of an airplane, there 生的荷载。 从我们家里的梁柱要飞机的双翼，这些都是由材料尺寸和must be an appropriate melding of materials, dimensions, and fastenings to produce structures that will 紧固件适当的组合，从而生产的结构在合理成本和使用周期的基础上可靠的履行

5、它的职责。perform their functions reliably for a reasonably cost over a reasonable lifetime.In practice, engineering mechanics methods are used in two quite different ways:在实践中，工程力学方法用于两种完全不同的方式。1. The development of any new device requires an interactive, iterative consideration of form, size, materials

6、, 任何新设计的发展要求都在尺寸，材料，荷载，耐久度，安全性和成本等方面进行交互、反复的考虑。loads, durability, safety, and cost.。2. When a device fails (unexpectedly) it is often necessary to carry out a study to pinpoint the cause of failure 当一个设计以外的失败的时候，必须经常的展开研究去查明失败的原因和确定可能的校正措施。and to identify potential corrective measures. Our best desi

7、gns often evolve through a successive elimination of 我们最好的设计是经常通过逐渐的消除缺点来实现的。weak points.To many engineers, both of the above processes can prove to be absolutely fascinating and enjoyable, not to 对于许多工程师，上述的过程被证明它是极具吸引力和令人愉悦的，更不用说（有时）是有利可图的。mention (at times) lucrative.In any real problem there is

8、never sufficient good, useful information; we seldom know the actual loads and 在任何真正的问题当中从未有足够好的，有用的信息，我们很少知道实际的荷载和任何精确的工作条operating conditions with any precision, and the analyses are seldom exact. While our mathematics may 件。 并且分析的结构很少是精确的。虽然我们的数学可以很精确，precise, the overall analysis is generally on

9、ly approximate, and different skilled people can obtain different 所有的分析结果一般仅仅是近似的，和不同掌握技术的人可以获得不同的解决方案。solutions. In the study of engineering mechanics most of the problems will be sufficiently idealized to 在工程力学的研究当中，大多数的问题都将被足够的理想化，以便允许得到唯一的答案。permit unique solutions, but it should be clear that t

10、he real world is far less idealized, and that you usually 但是我们应该清楚意识到“真实的世界”远不是理想化的，你通常不得不执行will have to perform some idealization in order to obtain a solution.一些理想化以便获得答案。The technical areas we will consider are frequently called statics and strength of materials, statics 我们将考虑的技术领域通常叫做“静力学”和“材料力学

11、”。静力学是指力作用于静止物体上的一种referring to the study of forces acting on stationary devices, and strength of materials referring to the effects 研究， “材料力学”是指那些力作用在结构上的of those forces on the structure (deformation, loading limits, etc.).影响（变形，荷载极限等）。While a great many devices are not, in fact, static, the method

12、s developed here are perfectly applicable to 然而在实际上许多的设备并不是静力学的问题，如果额外的荷载被考虑，这里的研究方法完全适用于dynamic situations if the extra loadings associated with the dynamics are taken into account (we shall briefly 动力学情形，以至于在动力的情况下也被考虑在内（我们应该简单的提一下是怎么样被做到的）mention how this is done). Whenever the dynamic forces are

13、 small relative to the static loadings, the system 只要动力学的力相对于静力荷载来说很小，这个系统通常可以考虑为静力学is usually considered to be static.的问题。In engineering mechanics, we will begin to appreciate the various types of approximations that are inherent 在工程力学里，我们将开始正确评价各种类型在实际问题中本身就存在的近似方法。in any real problem:Primarily, w

14、e will be discussing things which are in equilibrium, ., not accelerating. However, if we look 首先，我们将会讨论处于平衡及不产生加速度的物体。然而如果我们看的够仔细，所有东西是运动的。closely enough, everything is accelerating.We will consider many structural members to weightless but they never are.我们会把一些结构构件考虑成失重，但他们从来都不是。We will deal with

15、forces that act at a pointbut all forces act over an area.我们要处理的力作用在一个点上但是所有的力作用在一个区域上。We will consider some parts to be rigidbut all bodies will deform under load.我们会认为一些结构是刚性的但是所有的构件都在何在下变形。We will make many assumptions that clearly are false. But these assumptions should always render the 我们将做很多显

16、然错误的假设。 但是这些假设应该总是使得问题更加容易处理。problem easier, more tractable. You will discover that the goal is to made as many simplifying assumptions 你将发觉目标是尽可能的做简单的假设，而没有严重降低结果。as possible without seriously degrading the result.Generally there is no clear method to determine how completely, or how precisely, to

17、treat a problem. If our 通常没有明确的方法去可以完美的确定或者精确的处理这个问题。 如果我analysis is too simple, we may not get a pertinent answer; if our analysis is too detailed, we may not be able们的分析结构太过于简单，我们可能得不到正确的答案，如果我们的分析太过于详细，我们可能不能 to obtain any answer. It is usually preferable to start with a relatively simple analysi

18、s and then add more 或者任何的答案。 通常我们更喜欢的是从相对简单的分析开始，然后增加更多的细节以便于得到detail as required to obtain a practical solution.必须的实际结果。During the past two decades, there has been a tremendous growth in the availability of computerized 在过去二十年中，在计算机解决问题方法的实用性有了相当大的发展，methods for solving problems that previously wer

19、e beyond solution because the tie required to solve them 这些问题以前是不能解决的，因为需要解决他们时间不允许。would have been prohibitive. At the same time the cost of computer capability and use has decreased by 同时计算机的内存能力和使用成本已经降下了许多个数量级。orders of magnitude. We are experiencing an influx of personal computers; on campus, i

20、n the home, and in 我们正在经历个人计算机进入校园，家庭和商场的时代。business.Ch 4 Stress Limits in DesignHow large can we permit the stresses to be Or conversely: How large must a part be to withstand a given set 我们能够允许的最大应力是多少反过来，构件必须要多少才能够承受一组给定的荷载呢 of loadswhat are the overall conditions or limits that will determine th

21、e size and material for a part 将决定构件的尺寸和材料的整体状况或限制条件是什么Design limits are based on avoiding failure of the part to perform its desired function. Because different parts 设计极限是基于构件执行设定功能避免遭受失败。 因为不同的构件must satisfy different functional requirements, the conditions which limit load-carrying ability may b

22、e quite 满足不同的功能要求， 极限承载能力的条件在不同的原理可能完全的不同。different for different elements. As an example, compare the design limits for the floor of a house with those 例如，比较房屋楼板的设计极限和那些飞机的双翼。for the wing of an airplane.If we were to determine the size of the wooden beams in a home such that they simply did not bre

23、ak, we 如果我们确定了房屋木梁的尺寸，以致他们仅仅不会断掉，我们不会因为他们这样而非常开心；would not be very happy with them; they would be too springy. Walking across the room would be like 他们太过于有弹性，穿过房间就行走在潜艇夹板上。walking out on a diving board.Obviously, we should be concerned with the maximum deflection that we, as individuals, find accept

24、able. 显然我们应该关心我们每个人所能接受的最大挠度。This level will be rather subjective, and different people will give different answers. In fact, the same people 这个标准是非常主观的，不同的人给出不同的答案。事实上，相同的人给出不同的答案取决于他们may give different answers depending on whether they are paying for the floor or not!是否会为这个楼板付钱。An airplane wing st

25、ructure is clearly different. If you look out an airplane window and watch the wing during 飞机机翼的结构式显然不同。如果你从飞机窗户往外看，你会看到机翼在强对流天气中，你将看到很turbulent weather, you will see large deflections; in fact you may wish that they were smaller. However, you 的挠度。 事实上，你会希望他们更小一点。然而你知道最重要的know that the important iss

26、ue is that of structural integrity, not deflection.是结构的整体性而不是挠度。We want to be assured that the wing will remain intact. We want to be assured that no matter what the pilot 我们想要确保机翼保持完好无缺，我们想要确保无论飞行员做了什么和无论天气是怎么样，双翼也将and the weather do, that wing will continue to act like a good and proper wing. In f

27、act, we really want to be 继续表现得良好和合适的双翼 事实上，我们真的想要assured that the wing will never fail under any conditions. Now that is a pretty tall order; who knows what 确保机翼在任何情况下没有失败。 。由于这是非常艰难的任务。谁知道最坏的条the worst conditions might be件是怎样的呢Engineers who are responsible for the design of airplane wing structure

28、s must know, with some degree of 那些负责飞机机翼结构设计的工程师一定懂得， 一定程度的把握最有certainty, what the worst conditions are likely to be. It takes great patience and dedication for many years to 可能的最坏条件是什么。 他需要花费许多年的极大耐心和贡献去收集足够assemble enough test data and failure analyses to be able to predict the worst case. The ge

29、neral procedure is 的实验数据和失败失败分析，才能够预知“最坏”的情况。 一般的程序是研究to develop statistical data which allow us to say how frequently a given condition is likely to be 统计数据让我们解释在特定情况下可能会遇到的频率每1000小时一次，或者10000小时一次，encounteredonce every 1000 hours, or once every 10000 hours, etc.等等。As we said earlier, our object is

30、to avoid failure. Suppose, however, that a part has failed in service, and we 就像我们早期所说的，我们的目标是避免失败。假设，然而一部分在使用中失败了，我们就会被问到are asked; Why Error as such can come from three distinctly different sources, any or all of which can “为什么”“误差”类似的，就会从来自三个截然不同的来源出发，部分或者全部都能导致失败。cause failure:1. Error in design

31、: We the designers or the design analysts may have been a bit too optimistic: Maybe we ignored 设计的误差：我们的设计师或者设计分析者有那么一点过于乐观了：也许我们忽视了一些荷载；some loads; maybe our equations did not apply or were not properly applied; maybe we overestimated the 也许我们的公式不适用或者利用得不当； 也许我们高估了使用者的智慧。intelligence of the user; m

32、ay we slipped a decimal point. 也许我们忽略了一个小数点。2. Error in manufacture: When a device involves heavily stressed members, the effective strength of the members 制造的误差：当设计涉及到重压力的一部分，这部分的有效应力通过不适当得制造和组装而大大减弱。can be greatly reduced through improper manufacture and assembly: May the wrong material was used; maybe 也许使用了错误的材料；也许th