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1. There is nearly a limitless variety of materials. The method to understand them is to consider all materials as members of a big family. Materials that possess common characteristics are placed into their own group within the family. Although overlaps exist in the grouping system, it is easier to understand materials when relationships are identified.材料的种类有无限多。认识他们的办法就是把所有的材料按科来分型旦类。具有普通性能的材料分为一科,尽管这样分科会出现重复情况，但这样分类很容易了解他们盯租链的关系。2. The properties of a material are those characteristics that help modify and distinguish one material from another. All properties are observable and most can be measured quantitatively. Properties are classified into two main groups, physical and chemical properties. Physical properties involve no change in the composition of the material. Chemical properties are associated with the transformation of one material into another. Physical properties are, in turn, arbitrarily subdivided into many categories. 属性有助于人们更改和分辨各种材料。所有的属性都是可见的，大多数还可以量化。通常可以分为两大类，物理性质和化学性质。物理性质包括材料成份的不变性。而化学性质通常为从一种材料转变为另一种材料。然而，物理性质分类也很多凯孙。第 1 页3. These subdivisions bear names such as mechanical metallurgical, fabrication, general, magnetic, electrical, thermal, optical, thermonuclear, and electro-optical. Regardless of the name of the subdivision, physical properties result from the response of the materials to some environmental variable, such as a mechanical force, a temperature change, or an electro-magnetic field. It can be divided primarily into mechanical, thermal, electrical, magnetic, and optical properties. 这些分类都有相应的名称如机械冶金类，制造类，通用类，磁类，电气类，热学类，光学类，高热原子核反应类和电光类。无论其分类的名称是什么，物理性质会随着某些环境改变，如机械力，温度变化或者电磁场的改变而改变。它可以大致分为机械，热学，电气，磁和光学性质。4. Among other characteristics, we can list the following for the ideal material: endless and readily available source of supply; cheap to refine and produce; energy efficient; strong, stiff and dimensionally stable at all temperatures; lightweight; corrosion resistant; no harmful effects on the environment or people; biodegradable; numerous secondary uses.而针对其他的特性，我们可以理想的把他们分为：可无限使用，提炼和生产便宜，能源充足，在任何温度下都保持坚硬，外形稳定，轻质，防腐，环保，无害，可分解，大量二次使用。5. Technically, forging maybe defined as the process of giving metal in creased utility by shaping it, refining it, and improving its mechanical properties through controlled plastic deformation under impact or pressure.专业地讲，锻造可以定义为通过修整成形，提炼而使金属增强其使用性，并通过在施强压的情况下控制其塑性变形来改善其机械性能的一种方法。6. Hardening is a process of heating and cool steel to increase its hardness and tensile strength, to reduce its ductility, and to obtain a fine grain structure. By tempering or “drawing”, the hardness and brittleness may be reduced to the desired point for service conditions.淬火是对钢材进行加热和冷却来增强硬度和抗拉强度，减小延展性能，以获取精炼质地结构的一种过程。7. Belts and chains are used to connect two or more shaft for the transmission of rotation and power. The shafts may be at a considerable from one another, while belts also permit a certain amount of twist. A cam and its follower together form a mechanism that converts rotary motion or oscillating motion, into a cyclical linear or angular motion.8. Electro-discharge machining is mainly used for drilling, broaching, engraving, embossing, and thread cutting and similar to turning, milling, and grinding放电机械主要用来钻，铰，刻，压花和螺纹切割以及类似于车工工艺，铣和磨的工艺。第 2 页9. From an operating standpoint, any hydraulic system can be divided into four logical segments: the power input segment, the power transmission system, the control devices and the power output portion. 从操作性观点出发，任何液压系统都能在逻辑上划分为四类：动力输入，动力转换，控制设备和动力输出。第7点不知道怎么翻译、
