1. Metals are elements that generally have good electrical and thermal conductivity. Many metals have high
strength, high stiffness, and have good ductility.
金属就是通常具有良好导电性和导热性的元素。许多金属具有高强度、高硬度以及良好的延展性。
2. Plastic deformation is the ability of bend or deform before breaking. As engineers, we usually design
materials so that they don’t deform under normal conditions.
塑性变形就是在断裂前弯曲或变形的能力。作为工程师，设计时通常要使材料在正常条件下不变形。
3. The lathe bed is the main frame, involving a horizontal beam on two vertical supports. It is usually made of grey or nodular
cast iron to damp vibrations and is made by casting.
车床床身是包含了在两个垂直支柱上水平横梁的主骨架。为减振它一般由灰铸铁或球墨铸铁铸造而成。
4. Although small tolerances give higher quality work and a better operating mechanism, the cost of manufacture increases
rapidly as the tolerances are reduced. It is therefore important that the tolerances be specified at the largest values that the operating or functional considerations permit.
虽然较小公差能得到较高加工质量和较好操作机构，但随着公差的减小制造成本会迅速增加。因此公差被定为从操作或功能考虑允许的最大值是重要的。
5. A tensile test consists of slowly pulling a sample of material with a tensile load until it breaks. The ends of tensile
specimens are usually enlarged to provide extra area for grip-ping and to avoid having the sample break where it is being gripped.
拉伸试验包括慢慢加载拉伸载荷直到断裂。拉伸试件两端加粗为了提供装夹区域和避免试件断裂。
6. As we look around us we see a world full of “things”, machines, devices, tools, things that we have designed, built, and
used; things made of wood, metals, ceramics, and plastics. We know from experience that some things are better than others; they last longer, cost less, are quieter, or are ease to use.
当我们环顾四周，我们可以看到一个充满“物体”的世界，机器、设备、工具等一切由我们设计、建造和使用的物体；有木头、金属、水泥和塑料制成的物体。从我们的经验我们知道一些物体会比其他一些物体更好，如使用寿命更长，成本更低，更轻便或者更容易使用。
7. Interchangeability means that identical parts must be interchangeable, i.e., able to replace each other, whether during assembly or subsequent maintenance work; without the need for any fitting operations.
互换性意味着在相同的零件之间必须能够进行互换。无论是在装配时还是在其后的维修时，这些零件都可以互相取代而不需任何修配工作。
8. The term operation is defined as when one oprator(or a group of operators) works in a definite position (one machine tool
or clipping table) to achieve the continuous man.
一个或一组工人，在一个工作地（机床设备）上，对同一个或同时对几个工件所连续完成的那一部分工艺过程称为工序。
9. A gear can be gripped axially between a shoulder on the shaft and a spacer, with torque being transmitted
through a key.
一个齿轮可以用轴肩和挡圈进行轴向固定，并通过键来传递。 10.
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