1、 第一单元 应力与应变That branch of scientific analysis which motions, times and forces is called mechanicsand 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。For example, if the force operating on a sleeve bearing becomes too high, it will squeeze out the oil fi
2、lm 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。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
3、、大小、方向，这些被称为力的三要素。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., incapable 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
4、它们被假设成刚体，也就是不产生变形,以此来简化分析。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。If all the forces acting on a particle are balanced, the particle
5、 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。第二单元 材料的强度与塑性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 prov
6、ide 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。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 a
7、nd 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。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
8、 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。However actual measurement of L 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L的实际测量是更可取
9、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。Ductile and brittle materials behave differently in compression test as well. The compression 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。The compression test diagram for these materia
10、ls retains the qualitative features of the tension test diagram. The ultimate compressive strength 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。第三单元 轴设计Virtually all machines contain shafts. The most common shape for shafts is circ
11、ular 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）。A shaft must have adequate torsional strength to transmit torque and not be overstressed. It must also be torsionally still enough so that one mounte
12、d 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。Shafts are mounted on bearings and transmit power through such devices as gears, pulleys, cams a
13、nd 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。In addition, the shaft must be able to sustain a combination of bendin
14、g 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。Components such as gears and pulleys are mounted on shafts by means of key. The design 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。Another important aspect of shaft
15、 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。第四单元 Spur Gears齿轮Pressure angles for spur gears are usually 14.5 or 20 degrees, although other values can be used. Meshing gears
16、 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。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。
17、Worm gears are used where high ratios are desired and where the shafts are nonintersecting and at right angles.蜗杆蜗轮应用于传动比大而且两轴不相交但相互垂直的情况下。It has the great advantage that the cutting tool is a simple rack with ( nearly ) straight sided teeth which can easily be ground accurately.这种方法有很大的优势，切削工具是一个简单
18、的带有直齿边的齿条Modern shapers cutting car gears can run at 2000 cutting per minute. The shape of the cutter is roughly the same as an involute gear but the tips of the teeth are rounded.现代切削汽车的成型器齿轮转速可达每分钟2000转，齿刀形状与渐开线大致相同，但齿顶是圆形的。Bevel gears are often used when two shafts are at right angles to each oth
19、er and their centerline extensions intersect; however, some bevel gears are at angles other than 90 degrees.圆锥齿轮一般应用于相互垂直的两轴或两个中心线延长线的相交轴中，也可用于不垂直的两轴中。第五单元cams 凸轮The purpose of any cam is to produce a displacement of its follower; a secondary follower is often used to produce additional displacement
20、 in another location.使用凸轮的目的是使从动件产生位移，次级从动件在另一位置产生附加运动。The relative vertical position of point A with respect to B needs to be raised if the reaction value at B is excessive.如果B点的作用力过大，A点相对B点的相对垂直位置必须被提高。In general, the follower is considered to be the part that comes in contact with the cam profile
21、. However, when a secondary follower is used, the motion of the secondary follower is dictated by that of the primary follower.总的来说，从动件是与凸轮轮廓相接触的零件，然而，当用次级从动件时，次级从动件的运动就需通过主要从动件来实现。The simplest type of follower is the reciprocating type that merely moves up and down ( or in and out ) with the rotati
22、on of the cam; the centerline can be either collinear with the cam centerline or offset form it.最简单的从动件就是随着凸轮的转动而仅做上下（或进出）运动的从动件，其中心线可与凸轮中心共线，也可与之偏离。Fasteners are devices which permit one part to be joined to a second part and, hence, they are involved in almost all designs.紧固件是一种连接一个部分和另一个部分的装置，因此，
23、它涉及到几乎所有的设计。Springs are mechanical members which are designed to give a relatively large amount of elastic deflection under the action of an externally applied load.弹簧是一种被设计于在外力作用下产生相对弹性变形较大的机械构件第七章：砂型铸造1.The first stage in the production of sand casting must be the design and manufacture of a suita
24、ble pattern. Casting pattern has to be made larger than the finished casting size to allow for the shrinkage that takes place during solidification and cooling.在型砂铸造生产中，第一阶段是必须设计和制造合适的模型，考虑到铸件在凝固和冷却期间产生的收缩铸件模型的尺寸要比铸件的尺寸大。 2.If a hollow casting is to be made the pattern will include extension pieces
25、so that spaces to accept the sand core are molded into the sand. These additional spaces in the mold are termed core prints.如果铸造空心铸件时模型上包含伸长杆便于在砂中放置砂芯的空间称为型芯座。 3.Sand molds for the production of small and medium-sized castings are made in a molding box. The mold is made in two or more parts in order
26、 that the pattern may be removed.中小型尺寸的铸件砂型是在一个砂箱中制造，砂型由两部分或更多部分组成，以利于模型的顺利取出。 4.This process of filling and ramming may be done by hand but mold production is automated in a large foundry with the mold boxes moving along a conveyor, firstly to be filled with sand from hoppers and then to pass under
27、 mechanical hammers for ramming.填充和夯实的过程可以手工完成，但在大型铸造中砂型的制造是自动完成的，砂箱随着传送带移动，首先被料斗中的砂子填满，然后通过机械锤时被打实。 5.The risers should coincide with the highest points of the mold cavity so that the displaced air can readily escape from the mold. The sizes of risers should be such that the metal in them does not
28、freeze too rapidly.冒口应该与型腔的最高点相连接，使得进入的空气可以容易的从模型中溢出，冒口的尺寸应该足够大使模型中金属不会太快凝固。 6.When the metal that has been poured into a sand mold has fully solidified, the mold is broken and the casting is removed. The casting still has the runner and risers attached to it and there will be sand adhering to porti
29、ons of the surface.当熔的金属被倾倒到砂型内并充分凝固以后，砂型将被打破取出铸件，铸件上依然带有横浇口和冒口并且依然有砂子粘在表面。造是自动完成的，砂箱随着传送带移动，首先被料斗中的砂子填满，然后通过机械锤时被打实。 第8课 锻造1. Forging means the shaping of metal by a series of hammer blows, or by slow application of pressure. The simplest example is a blacksmiths forging of a hot piece of metal by
30、hammering the work-piece on an anvil.铸造是通过一系列的锤打或是在缓慢的加载压力的场合使金属成型的一种方法，最简单的实例就是热的金属的自由锻，即通过铁砧上锤打锻件。 2. Heavy smiths forging is fundamentally similar, differing only in the scale of the operation. The work-piece may be an ingot of 100 tons and the deforming force provided by a massive forging hammer
31、, but the whole process is controlled by the master smith, who decides each time where, and with what force, the blow should take place.重型自由锻和自由锻基本相似，仅在操作的规模上有所不同，锻件可以是一个100吨的铁块，锻压力由一个巨大的锻锤提供，但是整个锻造过程由操作者控制。他来决定什么时候用多大力打到什么地方。 3. Forging operations may be carried out using either forging hammers or
32、forging presses. With a press, as opposed to a hammer, pressure is slowly applied and plastic deformation tends to occur fairly uniformly throughout the material.锻造操作者既可以用锻锤也可以用锻压力来实现操作，用锻压力和锻锤相反，在压力缓慢作用使整个均匀杆产生塑性变形的趋势。 4. Forging hammers are of two basic types with the large hammer either dropping
33、on to the work-piece accelerated by gravity alone or, as in the steam hammer, accelerated by both gravity and steam pressure.锻锤有两种基本类型，既可以用很大的锤子通过作用在工件上也可以用蒸汽压力作用在工件上或者是两者结合。 5. Smiths or open-die forging is used for making very large forgings or when the number of forgings of a particular design is
34、 small. Open-die forging is also used to preform metal prior to final shaping by means of closed-die forging.自由锻或开模锻用于制造大型的锻件或者特殊设计的小锻件，开模锻用于预成型金属，在最终金属成型之前通常使用闭模锻。 6. Closed-die forging involves the use of accurately machined die blocks. The capital cost of a pair of die blocks is high, but this is
35、 allowable when it is required to make forgings to close dimensional tolerances and in large quantity, as would be the case for, say, connecting rods for the engine of a popular car.闭模锻包括精确的机械加工的模具，一对模具的成本很高，但是只适用于大批量生产和小的公差要求的锻件，例如，汽车发动机的连杆就是一个典型的例子。 第九章 电弧焊 1.Arc welding in one form or another is
36、the most widely used form of welding .the electrical supply is low voltage but high amperage and may be either alternating or direct . 电弧焊在一种或另一种形式是应用最广泛的焊接形式。电力供应是低电压，但是大电流，并且可以是交流或直流。 2.the earliest forms of arc welding used carbon electrodes.but nowadays the arc is struck between a metal electrod
37、e and workpiece .the electrode may either be of tungsten or be a consumable metal electrode that melts ,acting as a source of filler metal . 电弧焊接的最早的形式使用碳电极，但现在的电弧触发一个金属电极与工件之间，电极可以是钨或可熔化，作为填充金属供源的消耗性金属电极。 3.an alternating-current arc is broken and re-established at each half cycle and this leads to
38、 arc instability although the use of arc-established agents in the flux coating of electrode wires can overcome this problem . 交流电弧被打破并且重新建立在每个半周期，这导致电弧不稳定虽然在电极布线焊剂涂层使用电弧建立剂可以克服这个问题。 4.uncoated welding rods can be used for arc wilding .but it is more usual to use flux-coated electrodes .when steels
39、are welded using uncoated electrodes,oxides and nitrides can form and remain in the weld with a consequent loss of toughness . 未涂覆的焊条可以用于电弧焊。但更通常使用的焊剂涂覆的电极。当钢在使用未涂覆的电极焊接，氧化物和氮化物能够形成并保持在焊缝韧性因此而丧失。 5.flux-coated electrodes are widely used .the composition of the coatings is complex and a variety of di
40、fferent coatings are used to cater for different types of welding application . 焊剂涂覆的电极被广泛使用。涂层的组成是复杂和各种不同的涂料是用于配合不同类型的焊接应用。 6.in this case the electron flow is from electrode to work-piece .A concentrated arc issues from the electrode tip and heating of the work-piece is largely confined to the ver
41、y small ares beneath the electrode . 在这种情况下电子流动是从电极到工件，从电极头和工件的加热浓缩的弧的问题在很大程度上仅限于电极下方的非常小顷。第十章：钢1.In simple terms, a plain carbon steel may be said to be an alloy of iron and carbon containing less than 1.7% carbon. In practice, however, these steels rarely contain more than 1.4% carbon and other el
42、ements are also present, either as deliberate additions (e. g. manganese) or as impurities (e. g. sulphur and phosphorus). 简单来说，普通碳素钢也被称为含碳量少于1.7%的合金钢。然而事实上，这些钢材中很少有含碳量多于1.4%，同时也含有其它元素，例如一些额外添加物（如锰）或者杂质（如硫和磷）。2.In the manufacture of this material, complete deoxidation is not carried out and it is ma
43、de as rimming steel. It is produced as hot and cold worded sheet, strip, rod, wire and tube, and is available in the hot-worked or process annealed condition. 在材料的生产加工中，不能实现脱氧还原反应的钢被称为沸腾钢。它被用来生产热处理或冷处理的薄片、带、棒、电线、和管，并且它适用热轧和退火的情况下。 3.The strength and hardness of these steel is low, but a hard surface
44、 can be obtained by carbursing in order to combine a wear-resistant surface with tough core properties. 钢的强度和硬度低，可以通过渗碳的方法获得表面硬化以达到表面耐寒内部韧性较好的特性。 4.As the carbon content is raised above 0.2%, the strength increases into the range required for constructional purposes, but the ductility decreases. The
45、 fabrication qualities (working and welding characteristics) of this material are very good. 一旦钢中含碳量上升超过0.2%，结构上的强度会发生巨大变化，但是其延展性会下降。材料的制造质量（承载和焊接特性）非常好。5.Medium carbon steels are often quenched-hardened and fully tempered to give good strength with maximum toughness, which are the properties requir
46、ed of components such as shafts, gears and connecting rods. 中碳钢常被淬火硬化和高温回火处理以便给予良好的温度和最大的韧性，这些是轴、齿轮和连杆所要求的能力特性。 6.High carbon steels are quench hardened and lightly tempered to give high hardness with only limited toughness. Material in this classification is mainly used for making fairly small, rel
47、atively inexpensive cutting tools so that the group as a whole is known as carbon tool steel. 高碳钢常被淬火硬化和低温回火处理以便给予高硬度和一定韧性。此类材料主要被用于生产相当小、可靠地、廉价的切削工具，者这就是碳素工具钢。第十一章：金属热加工1.The principal kinds of heat-treatment used in practice .which differently affect the structure and properties ,and which are ass
48、igned to meet the requirements made to the semifabricated materials (castings forgings ,rolled stock ,etc.)and finished articles :are (1)annealing (2)normalizing (3)hardening and (4)tempering . 所用的主要种类热处理的做法，以不同方式影响结构和性能，并分配给满足于半加工材料制成的要求（铸件锻件，轧材等）和必要的类型：是（1）退火（2）正火，（3）淬火和（4）回火。 2.Normalizing raises the strength and hardness of medium and high-carbon steels by 10 to 15 percent as compared to annealed steel. 正火引起较退火的钢的强度和中等和高碳钢硬度由10至15。 3.Martensite is very hard and brittle ,having a much highertensile strength than the steel with a pearlite microstructure . 马氏体是非常硬且脆的，具有高得多的抗张强度比钢
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