第一单元
That branch of scientific analysis which motions, times and forces is called mechanics and is made up of two parts, statics and dynamics.研究位移、时间和力运动乘力是科学分析法的一个分歧，被称作力学，力学由两大部分组成，静力学和动力学。
1. For example, if the force operating on a sleeve bearing becomes too high, it will squeeze out the oil film and cause metal-to-metal contact, overheating and rapid failure of the bearing.例如：如果止推轴承上的作用力过大的话，会挤出油膜，引起金属和金属之间的相互接触，轴承将过热而迅速失效。
2. Our intuitive concept of force includes such ideas as place of application, direction, and magnitude, and these are called the characteristics of a force.力的直观概念包括力的作用点、大小、方向，这些被称为力的三要素。
3. All bodies are either elastic or plastic and will be deformed if acted upon by forces. When the deformation of such bodies is small, they are frequently assumed to be rigid, i.e., incapab
le of deformation, in order to simplify the analysis.所有的物体既可以是弹性的也可以是塑性的，如果受到力的作用就产生变形。当变形很小的时候它们被假设成刚体，也就是不产生变形。
4. The rigid-body assumption cannot be used in internal stresses and strains due to the applied forces to be analyzed. Thus we consider the body to be capable of deforming.刚体假设不能应用于内应力和内应变的分析，所以在实际力的分析时，要考虑物体的形变。
5. If all the forces acting on a particle are balanced, the particle will either remain at rest or will continue to move in a straight line at a uniform velocity.如果作用在质点上所有的力是平衡的，质点将会保持静止或做做匀速直线运动。
6. 第二单元
7. 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.reaction in the shaft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。
8. The usual manner of conducting the test is to deform the specimen at a constant speed. For example, in the universal testing machines, the motion between the fixed and moving crossheads can be controlled at a constant speed. 通常进行试验的方法就是使试件以恒定速度发生变形。例如，在万能拉伸试验机上，固定端和移动的十字滑块之间的变形是以恒定速度进行的。
9. The load that must be applied to enforce this displacement rate varies as the test proceeds. This load F may be divided by the cross-sectional area A to obtain the stress in the specimen at any time during the test.随着实验的进行，用来产生位移的载荷是随位移的变化而变化。在实验中，载荷F除以横截面积A可以得到任意时刻点的应力。
10. However actual measurement of ΔL is preferable where this is feasible. Stress and strain based on the initial (undeformed) dimensions, Ai and Li, are called engineering stress and strain.然而，在可行的位置上ΔL的实际测量是更可取的，基于原始尺寸Ai和Li的应力和应变称为工程应力和工程应变。
11. Ductile    and brittle materials behave differently in compression test as well. The compr
ession test is conducted on short cylindrical specimens placed between parallel plates.塑性和脆性材料在压缩试验中表现的特性是不相同的。压缩试验是把短圆柱形试件放在两平行平板之间进行的。
12. The compression test diagram for these materials retains the qualitative features of the tension test diagram. The ultimate compressive strength of a brittle of a brittle material is determined in the same way as in tension.材料压缩试验图保持了拉伸试验图性能上的特征。脆性材料的最大压缩强度与最大拉伸强度得到的方法相同。
13. 第三单元
14. Virtually all machines contain shafts. The most common shape for shafts is circular and the cross section can be either solid or hollow (hollow shafts can result in weight savings).几乎所有的机器都有轴，最常用的外形是圆形的，横截面是空心的或实心的圆形截面（空心轴可以减少重量）。
15. A shaft must have adequate torsional strength to transmit torque and not be overstress
ed. It must also be torsionally still enough so that one mounted component does not deviate excessively from its original angular position relative to a second component mounted on the same shaft.一个轴必须有足够的扭转强度来传递扭矩而不会破坏，同样也必须有足够的扭转刚度，这样安装轴就不能过度偏离相对于安装在同一轴上第二个零件的原始位置。
16. Shafts are mounted on bearings and transmit power through such devices as gears, pulleys, cams and clutches. These devices introduce forces which attempt to bend the shaft; hence, the shaft must be rigid enough to prevent overloading of the supporting bearings.轴安装在轴承上通过齿轮，滑轮，凸轮和离合器这些装置传递力。这些装置可以产生使轴弯曲的力，所以轴必修有足够的刚性防止支撑轴承的过载。
17. In addition, the shaft must be able to sustain a combination of bending and torsion and bending.另外，轴必须能承载弯扭组合的载荷，因此，这样就必须考虑弯扭组合的等效载荷。
18. Components such as gears and pulleys are mounted on shafts by means of key. The d
esign of the key and the corresponding keyway in the shaft must be properly evaluated.齿轮和滑轮构件是用键的方式连接在轴上的，键和对应的键槽的设计必须进行估算。
19. Another important aspect of shaft design is the method of directly connecting one shaft to another. This is accomplished by devices such as rigid and flexible couplings.轴设计的另一个重要方面是直接连接两轴，通过刚性和柔性的联轴器装置来实现。
20. 第四单元
21. Pressure angles for spur gears are usually 14.5 or 20 degrees, although other values can be used. Meshing gears must have the same pressure angles.直齿轮的压力角通常为14.5°或20°，另外也使用其它的角度，啮合齿轮必须具有相同的压力角。
22. The shape of the space between gear teeth on the gear as well as tooth module, so most gear manufacturing methods generate the tooth flank instead of forming.齿轮轮齿之间齿槽的形状是复杂的，并且随着齿的数目和模数变化而变化，因此大多数齿轮的加工方法是展成齿腹齿廓而不是齿形成形加工。

版权声明：本站内容均来自互联网，仅供演示用，请勿用于商业和其他非法用途。如果侵犯了您的权益请与我们联系QQ:729038198，我们将在24小时内删除。