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1、精选优质文档-倾情为你奉上ENGINEERING MATERIALSTYPES OF MATERIALS工程材料Materials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never living) materials.For industrial purposes, materials ar
2、e divided into engineering materials or nonengineering materials. Engineering materials are those used in manufacture and become parts of products. Nonengineering materials are the chemicals, fuels, lubricants, and other material used in the manufacturing process which do not become part of the prod
3、uct.材料可以在几个方面进行划分。科学家往往分类材料往往由他们的状态：固体，液体，或气体。他们也将它们分为有机（一旦生活）和无机（从来没有生活）材料。 工业用途划分，材料分为工程材料和化学材料。工程材料，是那些用在制造，并被加工成产品。 化学材料是化学品，燃料，润滑剂，及其他材料的使用在制造过程中不被加工成产品。 This grouping is not exact. Engineering materials may be further subdivided into: 1. Metals. 2. Polymers 3. Ceramics. A fourth type of materi
4、al sometime listed is called a composite. Materials in this group are made up of two or more material from the engineering groups, Each of the materials in composite retains its original characteristics. Examples of composites include wood-, concrete-, glass-reinforced polyester, and graphite polyme
5、r advanced composites.这个分组是不是很准确的。工程材料，可进一步细分为： 1、金属 2、聚合物3、陶瓷。第四类材料的某个时候上市，是所谓的复合。材料在这个分组的成立两个或两个以上的材料，从工程组，每组的复合材料在保持其原有的特色。例如，复合材料，包括木材，混凝土，玻璃纤维增强聚酯，聚合物和石墨等复合材料。 COMMON METALSPure metals are seldom used in common industrial products. Pure copper is used in electrical applications, in automotive r
6、adiators, and gaskets. Pure aluminum has application in the chemical and electrical industries. However, most metals are alloys(combinations of two or more elements). There are over 25,000 different iron-carbon alloys(steel) and over 200 standard copper alloys including a number of brasses, bronzes,
7、 and nickel silvers. Each of these alloys are identified by a code number.常见的金属纯金属是很少使用共同的工业产品。纯铜是用来在电气应用，在汽车散热器和垫圈。纯铝已应用在化工和电器行业。然而，大多数金属是合金（组合两个或两个以上的元素） 。有超过25000不同的铁碳合金（钢铁）和超过200标准铜合金，包括一些黄铜，青铜，镍银。每个这些合金所确定的一编号。 Steel is an alloy of iron and carbon with other elements added to produce specific p
8、roperties. The various type of steel can be grouped under two major heading:(1)Carbon steel. A steel in which the main alloying element is carbon. Carbon steel are further divided into three groups.a.Low carbon steel. This steel has a carbon content of less than 0.30 percent. It is the most common t
9、ype and is often called mild steel. It is relatively inexpensive, ductile, soft, and is easily machined and forged. Mild steel cannot be heat-treated(hardened). Low carbon steel is a general purpose steel.b.Medium carbon steel. This steel has a carbon content between 0.30 percent and 0.80. Harder an
10、d stronger than mild steel, it can be hardened by heat treating. Medium carbon steel is most commonly used for forgings, castings, and machined parts for automobiles, agricultural equipment, machines, and aircraft.c.High carbon steel. This type of steel is easily heat-treated to produce a strong, to
11、ugh part. The material has a carbon content above 0.80 percent. It finds wide use in hand tools, cutting tools, springs, and piano wire.(2)High alloy steel. These steels contain significant amounts of other elements in addition to carbon. The common high alloy steel are:a.Stainless steel which is pr
12、oduced by using chromium as a significant alloying element along with nickel and other metals. The result is a tough, hard, corrosion-resistant metal.b.Tool steel which is a special group of high carbon steels produced in small quantities to high quality specifications. Tool steel are used for a wid
13、e range of cutting tools and forming dies.c.Manganese steel which is an alloy containing 21 percent manganese and one percent carbon. This metal is used in mining, railroad, and construction equipment because of its high tensile strength.钢是合金铁和碳与其他元素添加到产生特定属性。各类型的钢可以分为两大类： （ 1 ）碳素钢。在其中的主要合金元素是碳。碳钢是进
14、一步分为三类。 a.低碳钢。钢中的碳含量小于0.30 。这是最常见的类型和常被人称作是低碳钢。这是相对便宜，韧性，软，很容易加工和伪造的。低碳钢不能热处理（硬化） 。低碳钢是一个一般用途的钢。 b.中碳结构钢。钢中碳的含量之间的0.30 和0.80 。强度大，比低碳钢，可以硬化热处理。中碳结构钢是最常用的锻件，铸件，机械零件，汽车，农业设备，机器和飞机等等用钢。 c.高碳钢。这种类型的钢是很容易热处理而拥有很好的强度。该材料中的碳含量高于0.80 。它发现广泛使用加工工具，如切割工具，弹簧，和钢琴丝。 （ 2 ）高合金钢。这些钢含有大量的其他要素在除碳。高合金钢有： a.不锈钢是所产生的使用铬
15、作为一项重大合金元素，随着镍和其他金属。结果是强硬，硬，耐腐蚀的金属。 b.工具钢这是一个特殊的群体高碳钢生产的少量，以高品质规格。工具钢是用于范围广泛的刀具和成形模具。 c.锰钢这是一种合金含有21 ，锰和碳1 。这种金属是用来在采矿，铁路，和建筑设备，因为它抗拉强度高。 PROPERTIES OF MATERIALSAll material have their own properties or characteristics. These properties may be arranged into major groups which include:Physical proper
16、ties.Mechanical properties.Chemical properties.Thermal properties.Electrical and Magnetic properties.Optical properties.Acoustical properties.材料性能所有的物质都有自己的属性或特征。这些属性或特征体现在各个方面，其中包括： 物理性能；力学性能；化学性质；热性能；电器及磁学性质；光学性质；声学特性。1.Physical PropertiesPhysical properties, for this discussion, are restricted to
17、 those which describe the basic features of the material. These features are measured or observed without the use of extensive scientific experiments. The common physical properties are size, shape, density, and porosity.Size is the overall dimensions of the object. These dimensions, for most materi
18、als, are given as thickness, width, and length or as diameter and length.Shape is the contour or outline of the object., Contour is given to an object by curved, notched, sloped, or other irregular surfaces.Density or specific gravity measures the mass of an object. The measurement is by weight for
19、a unit or a certain volume. Typically, density is measured by pounds per cubic foot or kilograms per cubic meter of material. Density allows the mass of one material to be compared with that of other materials.Porosity is a measure of voids(open pores) in the material. It is generally described as a
20、 ratio of open pore volume to total volume of material. This ratio expressed as a percentage. Porosity will provide a measure of liquid-holding power, or the ability of air or gas to move through the material.1.物理性能物理性质，为这次讨论中，只限于那些描述的基本特征的物质。这些功能是衡量或观察，无需使用广泛的科学实验。共同的物理性质是大小，形状，密度，孔隙度。 尺寸是衡量物体大小的量。
21、这些方面，对于大多数材料，给出了厚度，宽度，长度或作为的直径和长度。 形状的轮廓或大纲的对象，轮廓是给一个对象，由弯曲，缺口，倾斜，或其他不规则表面。 密度是物体的属性量，物体的固有特征。测量是按重量计算是一个单位或某一个量。通常情况下，密度是衡量英镑每立方米步行或公斤每立方米的材料。密度，让各个材料加以比较，是每个材料的固有特征。 孔隙度是衡量孔洞（开放的毛孔）在物质。人们普遍形容为一的比例，开放孔隙体积总量的材料。这个比例，以百分比表示。孔隙度将提供一定程度的液体控股权，或有能力的空气或气体动议通过的材料。 2.Mechanical PropertiesMechanical propert
22、ies mean a materials ability to carry or resist the application of mechanical forces and loads. The materials reaction to these forces is usually either deformation (shape change) or fracture.Mechanical properties are probably the most important, to manufacturing processing. They determine the exten
23、t to which a material may be formed, sheared, or machined.Typical forces which are applied to a material are tension, compression, shear, and torsion, these forces are used to form and form and shape materials. Furthermore, materials must withstand excess amounts of these forces in product applicati
24、ons. Since screws are used to assemble wood parts, they must absorb torsion forces. Rods holding suspended fixtures must withstand excess tension forces. The head of a hammer must absorb compression forces.(1)Stress-strain. The stress-strain relationship is often used to study many mechanical proper
25、ties. Stress is force applied to material. It is usually measured in either pounds per square inch or kilograms per square centimeter. Strain is the change in the length of a material which is under stress. The strain measurements are given in terms of the amount of elongation (increased length) of
26、the material per unit of length. Strain is given in thousandths of an inch per inch of material of millimeters (or smaller units) per centimeter of material. For most materials, the elongation of a material under stress is quite small.A stress-strain diagram, like the one shown in Fig.1.1, is widely
27、 used to chart stress-strain relationships. The stress (force per unit area) is plotted on the vertical axis while the strain (elongation of each unit of length) is plotted on the horizontal axis.As stress is applied, the material first resists permanent deforming. This area is the materials elastic
28、 range. This is a range in which the material will return to its original length when the force is released.Applying additional stress (force) will bring the material to its yield point. At this point additional strain (elongation) occurs without additional force (stress) being applied. Strain above
29、 this point is produced with smaller amounts of force. The force also produces permanent changes in the length of the material.This elongation which is above the materials elastic limit (point at which the material will mot return to its original length) is called plastic deformation.As stress is in
30、creasingly applied above the yield point, additional strain occurs. Finally, a maximum strain is reached and the material begins to fail, Its internal structure begins to come apart This point is called the materials ultimate strength or tensile strength. Additional stress may cause a reduction in c
31、ross-sectional area (necking) and will finally cause fracture.(2) Mechanical strengths. A material can be subjected to a number of different types of forces. They may be tension , shear, torsion, compression, or a combination of these force. Each possible force causes a material to respond in a diff
32、erent way. A material, therefore, has several different mechanical strengths . The strength depends on the force applied.The most common mechanical strengths are:a.Tensile strengththe maximum tension load a material can withstand before fracturing. Tensile strength is the easiest strength to measure
33、 and, therefore, is widely used.b.Compression strengththe ability to resist forces which tend to squeeze the material into a new shape. It is basically the opposite of tensile strength. Excessive compression force will cause the material to rupture (bucking and splitting).c.Shear strengththe ability
34、 to resist fracture under shear forces. The shear forces is caused by offset forces applied in opposite. These forces cause the grains or molecules of the material to slide by one another and eventually fracture.d.Torsion strengththe ability to resist twisting forces. Forces which exceed the torsion
35、 strength (modulus of rupture) will cause the material to rupture.e.Flexure (bending) strengththe ability of a material to resist the combination of tensile and compression forces. As seen in Fig.1.2, when a material is bent, the material on the inside of the bend must compress while that on the out
36、side portion must stretch. A material must have flexure strength to undergo bending processes.f.Fatigue strengththe ability to resist forces which wary in direction and/or magnitude. Typical of forces which cause. Fatigue are constant bending back and forth(plastic hinge), applying and releasing ten
37、sion forces(coil spring), or torsion forces(coil spring), or torsion forces(automobile torsion bar).g.Impact strengththe ability to resist a rapidly applied load. This is a more specific measure of tension or compression strengths, Impact strength determines the ability to absorb a tension or compre
38、ssion load which is quickly applied. Impact strength is often called toughness. The action of a hammer on a nail applies such impacts. Forging dies must have high impact strength.(3) Plastic flow of materials. In addition to the mechanical properties involving strength, materials have characteristic
39、s that govern their behavior during the plastic defomation stage. These properties are usually called ductility and creep.Ductility is the plastic flow characteristic of a material under normal temperature. The higher the ductility of a material the greater is ability to be formed without fracturing
40、. Highly ductile materials can be easily bent. Drawn into wire, or extruded.Creep is the movement or plastic flow of material under load over an extended period of time. Creep of a material is affected by the stress level (force applied), temperature of the material, and the length of time over whic
41、h the stress is applied. Also different types of material have different creep characteristics. Wood creeps very little. Metal experiences slight amounts of creep. Glass and plastic are more likely to experience significant amounts of creep.(4) Hardness. Hardness is the resistance of a material to p
42、enetration or scratching. It accounts for abrasion resistance as well as resistance to denting. Hardness is also directly related to strength. The harder a material the stronger it is. Metallic and ceramic material are almost always harder and stronger than polymeric materials. A number of different
43、 testers have been designed to test the hardness of a variety of materials.2.力学性能力学性能是指材料的能力进行或抵制的应用机械力量和负载。物质的反应，这些势力通常是要么变形（形状变化）或骨折。 力学性能在制造业加工是最重要的。他们决定在何种程度上的物质，可能形成的，剪切，或加工。 典型的力量，这是应用到材料的张力，压缩，剪切，扭转，这些属性是用来形式和形式和形状的材料。此外，材料必须承受过多的数额，这些特征在产品应用。由于螺丝是用来组装的木材部分，他们必须吸收扭转的力量。棒控股暂停固定装置必须承受过多的紧张局势的力量
44、。头锤必须吸取压缩力量。 （ 1 ）应力应变。应力应变关系是经常被用来研究许多力学性能。强调的是不同的应用材料。这通常是衡量，无论磅每平方英寸或公斤每平方厘米。应变的变化在长度，材料是在压力下。应变测量，给出了在条款的数额伸长率（增加长度）的物质每单位长度。应变是由于在千分之一英寸每英寸的材料毫米（或规模较小的单位） ，每厘米的材料。对于大多数材料，伸长率的材料下，强调的是，相当小。 应力应变图，是广泛用于图表的应力应变关系。应力（力量每单位面积）是策划对纵轴，而应变（伸长率的每一单元的长度）是策划对横轴。 作为强调的是应用，材料的第一抗拒的永久变形。这方面的材料的弹性范围内。这是一个范围，在
45、这些材料将返回其原来的长度时，该部队是释放。 申请额外的压力（力量） ，会带来的材料，其屈服点。在这一点上额外的应变（伸长率）发生在没有额外部队（应力）目前适用的。株以上，这点是生产与规模较小的数额武力。该部队还制作永久性的变化，在长度的材料。 这伸长率是上述材料的弹性极限（点在这些材料的摩托罗拉将返回其原来的长度） ，是所谓的塑性变形。 需要强调的是，越来越多的应用以上屈服点的，额外的应变发生。最后，最大应变是达成和物质开始变化，其内部结构开始来，除了这点是所谓的材料的极限强度或拉伸强度。额外的压力可能会导致减少在截面积（缩颈） ，并将于最后导致断裂。 （ 2 ）机械的优势。物质可以受到一些
46、不同类型的变化力。他们可能会紧张，剪切，扭转，压缩，或结合这些力量。每一个可能的应变都会造成的物质不同的方式的回应。 1材料，因此，有几个不同的机械的优势。实力取决于对应变力的应用。 最常见的机械的优势是： a.拉伸强度-最大张力负荷的材料，能够经受住之前，压裂。拉伸强度是最容易的实力来衡量，因此，这是广泛使用的。 b.压缩强度-抵抗能力的力量，往往挤压的物质进入了一个新的形状。它基本上是相反的拉伸强度。过度的压缩力，会导致材料破裂（ 5.40和分裂） 。 c.抗剪强度-抵抗能力下，剪切力。剪切势力，是造成抵销力量，适用于相反。这些强度变化造成谷物或分子的物质，并最终断裂。 d.扭转强度-抵抗
47、能力扭力量。势力超过扭转强度（断裂模数） ，会导致材料破裂。 e.弯曲（弯曲）的力量-能力的物质，以对抗相结合的拉伸和压缩的力量。当材料是弯曲的时候，物质的内部弯曲必须压缩，而对外界的部分，必须舒展，所有材料必须有抗弯曲强度进行弯曲的能力。 f.疲劳强度-抵抗能力的特征量，在方向和/或严重程度。典型的力量，其中的原因。疲劳是不断弯曲背部和提出的（塑性铰） ，申请和释放紧张的势力（弹簧） ，或扭转的力量（弹簧） ，或扭转的力量（汽车扭杆） 。 g.冲击强度-抵抗能力迅速应用负载。这是一个更具体的措施，紧张或压缩的优势，冲击强度决定的能力，吸纳紧张或压缩负荷是迅速的应用。冲击强度是通常被称为韧性。
48、行动一锤就一钉适用于这种影响。锻模必须具有高冲击强度。 （ 3 ）塑性流动的材料。在除了力学性能，涉及强度，材料有特色的管治他们的行为在塑料变形的阶段。这些物业通常所谓的延性和蠕变。 延性是塑料流动特性的材料在常温下。高延性的材料更大的是能力，形成无压裂。高韧性材料可以很容易地流动，或挤压。 蠕变是运动或塑性流动的材料荷载作用下一个较长时期内的时间。蠕变的材料是受应力水平（力量的应用） ，温度的物质，以及长的时间超过该强调的是应用。此外，不同类型的材料有不同的蠕变特性。木材逐渐很小。金属的经验，轻微的金额蠕变。玻璃和塑料更有可能的经验，大量的蠕变。 （ 4 ）硬度。硬度是耐药性的物质，以渗透或
49、抓伤。它占的抗磨损性以及抗denting 。硬度也是直接相关的实力。越难的材料越强，这是。金属和陶瓷材料几乎总是难以和强大的比高分子材料。一些不同的测试已旨在检验硬度的各种材料。 3.Chemical PropertiesAll materials are used in some types of environment. All environments, except a pure vacuum, contain chemicals. These chemicals may be gases (oxygen, hydrogen, chlorine, nitrogen), liquids (water,