Classification of engineering materials Materials are the matter of the universe. These substances have properties that make them useful in structure, machines, devices, products, and systems. The term properties describe behavior of materials when subjected to some external force or condition. Engineering materials is a term often used loosely to define most materials that go into products and systems. Engineering materials can also have a more specific meaning that refers to materials whose structure has been designed to develop specific properties for a given application. 材料是宇宙的问题。这些物质的属性，使它们在结构，机器，设备，产品有用，和系统。一词描述材料性能的行为时，受到某种外力作用或条件。工程材料通常用于定义松散的材料，最深入的产品和系统的术语。工程材料也有更具体的含义是指其结构已设计开发出面向特定应用的特定性能材料
There are 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. 有近无限的材料不同。该方法了解他们是考虑作为一个大家庭的所有材料。材料是拥有共同的特点是放置到自己在家庭组。虽然在分组重叠系统中存在，这是容易理解的材料时，关系identified.Engineering材料通常用于定义松散的材料，最深入的产品和系统的术语。工程材料也有更具体的含义是指其结构已设计开发出面向特定应用的特定性能材料
Four groups, metallics, polymers, ceramics, and composites comprise the main groups; a fifth group of other materials is used for materials that do not fit well into the four groups. Each group then divides into subgroups. Within any system such as transportation, communications, or construction, numerous materials systems exist. There systems must pull materials from the groups with the material’s family to meet their special needs. The wise materials user recognizes the many options available because of the compatibility between groups and then proceeds to develop a materials system that meets a specific need. 四组，金属，聚合物，陶瓷和复合材料构成的主要群体，其他材料的第五组的材料不适合到四组中使用。每个小组再分为分组。在任何诸如交通，通讯，或建筑，系统存在大量的材料体系。有系统必须撤出与材料的家庭团体的材料，以满足他们的特殊需要。用户明智的材料，认识到很多的选择，因为各群体之间的兼容性，然后继续发展提供的材料系统，以满足特定的需要。
The grouping system used here follows closely grouping systems common to engineering. Slight differences exist in other grouping systems. For example, one system might divide materials into metals, polymers, ceramics, glass, wood, and concrete. Some systems divide all materials into three groups: organics, metals, and ceramics. Then they distinguish between natural and synthetic materials. Others group materials are as crystalline or amorphous. Regardless of the system, some inconsistencies develop because of the nearly limitless variety of materials. Still, the advantages of grouping outweigh the limitations.
该系统采用分组这里紧随通用分组系统的工程。细微差别存在于其他分组系统。例如，一个系统可以分为金属，聚合物，陶瓷，玻璃，木材，混凝土。有些系统分为三组：有机物，金属，陶瓷的所有材料。然后，他们区分xx和合成材料。其他组物料所结晶或无定形。无论制度，一些不一致的地方发展，因为几乎无限的材料不同。尽管如此，分组超过限制的优势
Metals Metallics, or metallic marerials, include metal alloys. In a strict definition, metal refers only to an iron, gold, aluminum, and lead. The definition used for a metal will differ depending on the field of study. Chemists might use a different definition for metals than that used by physicists. 金属色，或金属marerials，包括金属合金。在一个严格的定义只是指金属铁，金，铝，铅。一个金属使用的定义会有所不同的研究领域。化学家可能比使用金属不同的定义中使用的物理学家。
Metals are elements that can be defined by their properties, such as ductility, toughness, malleability, electrical and hear conductivity, and thermal expansion. 金属可以定义自己的属性，如塑性，韧性，延展性，电气和听到导电元素和热膨胀。
Metals are also large aggregations. Metals usually have fewer than four valence electrons, as opposed to nonmetals, which generally have for to seven. The metal atom is generally much large than the atom of the nonmetal. 金属也大聚合。金属通常有少于4个价电子，而不是非金属，而一般的有7。金属原子通常非常大的比非金属原子。
Alloys consist of metal elements combined with other elements. Steel is an iron alloy made by combining iron, carbon, and some other elements. Aluminumlithium alloys provide a 10% saving in weight over conventional aluminum alloy. 合金组成与其他元素结合金属元素。钢是铁合金相结合，铁，碳，更有一些其他因素。 Aluminumlithium合金，重量提供了比传统的10％，节约铝合金
While metals comprise about three-fourths of the elements that we use, few find service in their pure form. There are several reasons for not using pure metals. Pure metals may be too hard or too soft, or they may be too costly because of their scarcity, but the key factor normally is that desired property sought in engineering requires a blending of metals and elements. Thus, the combination forms (alloys) find greatest use. Therefore, metals and metallics become interchangeable terms. Metals are broken into subgroups of ferrous and nonferrous metals. 而金属约占四分之三的元素，我们使用，但很少发现其纯粹的形式服务的四分之三。有不使用纯金属的几个原因。纯金属可能太硬或是太软，也可能是因为他们太稀缺昂贵，但关键的因素通常是在工程所需的属性要求，需要金属和元素融合。因此，组合形式（合金）发现的{zd0}的使用。因此，金属和金属色成为互换条件。金属分为黑色和有色金属群。
Ferrous Ferrous metals include iron and alloys of at least 50% iron, such as cast iron, wrought iron, steel, and stainless steel. Each of these alloys is highly dependent on possessing the element carbon. Steel is our most widely used alloy. Sheet steel forms car bodies, desk bodies, cabinets for refrigerators, stoves, and washing machines; it is used in doors, “tin” cans, shelving, and thousands of other products. Heavier steel products, such as plate, I beams, angle iron, pipe, and bar, form the structural frames of buildings, bridges, ships, automobiles, roadways, and many other structures. 黑色金属包括铁，如铸铁和至少50％的铁，合金，铸铁，钢，不锈钢。这些合金的每一个高度依赖于拥有的碳元素。钢铁是我们使用最广泛的合金。钢板车身形式，办公桌团体，冰箱，火炉柜，洗衣机，它是在室内使用，“锡”罐，架子，和其他数千种产品。较重的钢铁产品，如钢板，我梁，角钢，钢管，和酒吧，成为建筑物的结构框架，桥梁，船舶，汽车，道路，以及许多其他结构。
Nonferrous metal elements other than iron are called nonferrous metals. The nonferrous subgroup includes common lightweight metals such as titanium and beryllium and common heavier metals such as copper, lead, tin, and zinc. Among the heavier metals is a group of white metals, including tin, lead, and cadmium; they have lower melting points, about 230 to 比铁金属元素被称为其他有色金属。该小组包括有色金属，如钛，铍和共同较重的金属，如常见的铜，铅重量轻金属，锡和锌。其中较重的金属是一种白色金属，包括锡，铅组，镉，他们具有较低的熔点，约230至330℃。在高温有色金属的钼，铌，钽，钨。钨是所有金属{zg}熔点：
Powdered metals Alloying of metals involves melting the main ingredients together so that on cooling, the metal alloy is generally a nonporous solid. Powder metal is often used instead because it is undesirable or impractical to join the elements through alloying or to produce parts by casting or other forming processes. Powdered metal is sometimes called sintered metal. This process consists of producing small particles, compacting, and sintering. The squeezing pressure with added heat bonds the metal powder into a strong solid. Powdered metals can be ferrous, nonferrous or a combination of ferrous and nonferrous elements with nonmetallic elements. 涉及金属合金熔化的主要成分在一起，使冷却，金属合金通常是无孔固体。粉末金属经常被用来代替，因为这是不可取的或不切实际通过加入合金或出示的铸造成形过程或其他地方的元素。金属粉末有时也被称为烧结金属。这个过程包括生产小颗粒，压缩，和烧结。与债券增加热量的金属粉末挤压的压力成为一个强大的固体。金属粉末可铁，有色金属或非金属元素与黑色和有色金属要素的组合。
Polymerics Polymeric materials basically are materials that contain many parts. A poly mer is a chainlike molecule made up of smaller molecular units (monomers). The monomers, made up of atoms, bond together covalently to form a polymer that usually has a carbon backbone. Thousands of polymers join together to form a plastic. 高分子材料的材料基本上是包含许多部分。阿聚滨海是一个链状分子由小（单体）分子单位组成。单体，由原子组成的，共价键一起，形成聚合物，通常有一个碳骨干。成千上万的聚合物联合起来，形成一个塑料。
Plastics The term plastic is used to define human-made polymer resins containing carbon atoms covalently bonded with other elements, along with organic and inorganic substances. The word plastic also means moldable or workable, such as with dough or wet clay. Plastic materials are either liquid or moldable during the processing state, after which they turn to a solid. After processing, some plastics cannot be returned to the plastic or moldable state; they are thermosetting plastics or thermosets. Common thermosetting plastics include epoxy, phenolic, and polyurethane. Other plastics can be repeatedly reheated to return to the plastic state; they are thermoplastics. Examples of thermoplastic plastics are acrylics, nylon, and polyethylene. 塑料一词是用来定义人类制造的聚合物树脂含有共价键与其他元素碳原子，以及有机和无机物质。这个词也意味着可塑性塑料或可行的，如与面团或湿粘土。塑料材料不是液体或模压在处理状态，随后他们转向了坚实的。经过处理，有些塑料不能返回到塑料或可塑性状态，它们是热固性塑料或热固性塑料。常见的热固性塑料，包括环氧，酚醛和聚氨酯。其他塑料可以反复加热返回到塑性状态，它们是热塑性塑料。热塑性塑料的例子有腈纶，尼龙和聚乙烯。
Wood Of all the materials used in industry, wood is the most familiar and most used. Wood is a natural polymer in the same manner that polymers of ethylene are joined to form polyethylene, glucose monomers polymerize in wood to form cellulose polymers (C6H10O5). Glucose is a sugar made up of carbon (C), hydrogen (H), and oxygen (O). cellulose polymers join in layers with the glue like substance lignin, which is another polymer.
在所有的工业用材料，木材是最熟悉和最常用的。木材是一种相同的方式，乙烯聚合物的加入，形成xx高分子聚乙烯，葡萄糖单体聚合，形成木（C6H10O5）纤维素聚合物。葡萄糖是一种糖组成的碳（C），氢气（H）和氧（O）。加入纤维素聚合物层，木质素等物质，这是另一种聚合物胶。 Elastomers An elastomer is defined as any polymeric material that can be stretched at room temperature to at least twice its original length and return to its original length after the stretching force has been removed. Elastomers are able to store energy, so they can return to their original length and/or shape repeatedly. Elastomers have a molecular, amorphous structure similar or that of other polymeric materials. This amorphous, or shapeless, structure consists of long coiled-up chains of giant molecules(polymers)that are entangled with each other. Adjacent polymers are not strongly bonded together. When a tensile force is applied, these coils straighten out and snap back like springs to their original coiled condition on removal of the force. 弹性体是指任何高分子材料，可在室温下延伸到至少两倍原来的长度和拉伸力后，返回到原来的长度已被删除。弹性体能够存储能量，这样他们就可以回到原来的长度和/或形状反复。弹性体的分子，无定形结构相似或其他聚合材料。这种含糊不清的，或无形的，结构由长期盘绕组成（聚合物）是相互纠缠大分子链。相邻聚合物不强粘合在一起。当施加拉力，这些线圈整顿和类似弹簧弹回其原来的xxxx缠绕条件。
Other natural polymers A most amazing natural polymer is human skin, which has no equal substitute. Animal skin or hide in the form of fur and leather has limited industrial use because synthetic materials have been developed that offer greater advantages to the designer than those of the natural polymers have. Medical science continues to study such natural polymers as bones, nails, and tissues of human beings and animals to synthesize these materials for replacement when they are damaged due to injury or illness. Bioengineering and biomechanics are newer fields that integrate engineering and medicine to solve material problems in the treatment of humans. 阿最惊人的xx高分子，是人的皮肤，而没有平等的替代品。动物皮肤或隐藏形式的毛皮和皮革工业用途有限，因为合成材料已经开发出提供更多的优势，比xx聚合物的设计，都。医学界将继续研究，骨骼，指甲等xx聚合物，以及人类和动物组织中合成更换这些损坏时，因受伤或患病的材料。生物工程和生物力学的新领域相结合的工程和药品，解决了人类xx的重大问题。
Ceramics Ceramics are crystalline compounds combining metallic and nonmetallic elements, glass is grouped with ceramics because it has similar properties, but most glass is amorphous. Included in ceramics are porcelain such as pottery; abrasives such as emery used on sand-paper, refractories such as tantalum carbide, with a melting temperature of about 陶瓷结合的结晶化合物，金属和非金属元素，玻璃与陶瓷分组，因为它具有类似的性质，但大多数玻璃无定形。在陶瓷包括陶器，如瓷器，磨料磨具，例如用砂砂布纸，碳化钽等耐火材料，约 |
