[机械综合] 机电类专业专业英语例句中英对照版

机电类专业专业英语例句中英对照版
共23页word版

Unit 1 Metals
The use of metals has always been a key factor in the development of the social systems of man. 在人类社会的发展中，金属的应用一直起着关键的因素 Of the roughly 100 basic elements of which all matter is composed, about half are classified as metals 构成物质的大约100多种元素中，大约有一半为金属元素。   
The distinction between a metal and a nonmetal is not always clear-cut.金属和非金属之间的区别并不是很明显   
The most basic definition centers around  the type of bonding existing between the atoms of the element, and around the characteristics of certain of the electrons  associated with these atoms.  最基本的定义集中在元素原子间存在的连接形式和与这些原子相关联的电子的某些特性.
In a more practical way, however, a metal can be defined as an element which has a particular package of properties. 然而，在实际应用中，金属可以定义为具有某些特性集合 的某种元素。Metals are crystalline（晶体的）   
when in the solid state and, with few exceptions  (e.g. mercury), are solid at ambient  temperatures（常温下） .      
除少数金属外如水银，金属在常温下是固态的They are good conductors of heat and electricity and are opaque（nonopaque）  to light。它们是热和电的良导体，不透光      They usually have a comparatively high density      它们往往具有较高的密度。Many metals are ductile -that is, their shape can be changed permanently  by the application of a force without breaking 。 许多金属具有延展性，也就是说，在不被破坏的前提下它们的形状在外力的作用下可以发生改变。
The forces required to cause this deformation and those required to break or fracture a metal are comparatively high, although, the fracture forces is not nearly（= far from, much less than）  as high as would be expected from simple consideration of the forces required to tear apart the atoms of the metal引起永久变形所需的力和最终使金属断裂所需的力相当大，尽管发生断裂所需的力远没有像所预期的撕开金属原子所需的力那么大One of the more significant of these characteristics from our point of view is that of crystallinity（n,结晶性）。 从我们的观点来看，在所有的特性中结晶性是最重要的。A crystalline solid is one in which the constituent atoms are located in a regular three-dimensional array as if they were located at the corners of the squares of a three-dimensional chessboard .  结晶体是这样一种结构，组成它的原子定位在规则的三维排列中，仿佛位于三维棋盘的方格的角上。The spacing of the atoms in the array is of the same order as the size of the atoms, the actual spacing being a characteristic of the particular metal.      原子间距随着原子大小呈规律性变化，原子间距是金属的一种特性.      The directions of the axes of the array define the orientation of the crystal in space. 三维排列的轴线决定了晶体在空间中的方向The metals commonly used in engineering practice are composed of a large number of such crystals, called grains .  在工程实践中应用的金属由大量的晶体组成，这些晶体称之为晶粒.      In the most general case , the crystals of the various grains are
randomly oriented in space .            在大多数情况下，晶粒在空间中是自由排列的      The grains are everywhere in intimate contact with one another and joined together on an atomic scale. 谷物的到处都是在亲密接触,彼此连接在一起在一个原子尺度。The region at which they join is known as a grain boundary. 晶粒之间连接区域被称为晶界.