机械工程力学专业英语翻译

4 Overview of Engineering Mechanics（工程力学概况）

(1) Ideally, however, every such item has been designed according to some set of “functional requirements” as perceived by the designers-that is, it has been designed so as to answer the question, “E xactly what function should it perform?” In the world of engineering, the major function frequently is to support some type of loading due to weight, inertia, pressure, etc. From the beams in our homes to the wings of an airplane, there must be an appropriate melding of materials, dimensions, and fastenings to produce structures that will perform their functions reliably for a reasonable cost over a reasonable lifetime.

然而，在理想的情况下，每一件产品都是设计人员根据对某些“功能要求”的理解而设计出来的，也就是说，在设计过程中，应该回答这样的问题，即“它应该具有哪种确切的功能？”在工程领域，主要功能通常是承受由于重力，惯性力，压力等作用的一些类型的载荷。从我们居住房屋的梁到飞机机翼，都必须有一个适当的材料，尺寸，在较合理地寿命基础上具有较合理地成本，并能可靠地完成其功能的产品结构连接的组合。

(2) In any" real" problem there is never sufficient good,useful information;we seldom know the actual loads and operating conditions with any precision, and the analysis are seldom exact.While our mathematics may be precise,the overall analysis is generally only approximate,and different skilled people can obtain different solutions.In the study of engineering mechanics,most of the problems will be sufficiently "idealized“ to permit unique solutions ,but is should be clear that the ”real word " is far less idealized ,and that you usually will have to preform some idealization in order to obtain a solution.

对于任何实际的问题，总是缺乏足够完整和有用的信息。我们很少准确的知道实际载荷和工作状态，因此，所做的分析工作也很少是精确地。虽然我们的数学可以准确，全面的分析一般只能近似，而且不同技术水平的人能得到不同的解。在工程力学研究领域，大多数问题要想得到唯一解就要充分的理想化，但应该清楚，“现实世界”远非理想化程度，因此为了得到问题的解决方案不得不进行一些理想化假设。

(3) In engineering mechanics, we will appreciate the various type of approximations that are inherent in any real problem: 在工程力学中，我们在处理现实问题会采用各种各样的近似法。

(4)Primarily, we will be discussing things which are in “equilibrium”, i. e., not accelerating. However, if we look closely enough, everything is accelerating. We will consider many structural members to be “weightless”–but they never are. We will deal with forces that act at a “point”, but all forces act over an area. We will consider some parts to be “rigid”–but all bodies will deform under load.

首先，我们将要讨论处于“均衡”的事情，也就是说，不是加速的事情。但是，如果我们仔细观察，一切事情都是加速的。我们会认为许多结构单元是无质量的，但情况从来不是这样的。我们会处理作用在某个点上的力，但所有力都作用在某个区域上。我们将考虑某些零件是“刚性的”，但是所有机构都将在负载下变形。

6 Shaft Design（轴设计）

(5)If a shaft carries several gears or pulleys, different sections of the shaft will be subjected to different torques, because the total power delivered to the shaft is taken off piecemeal at various points. Figure 6.1 shows a shaft with an