ENGINEERING MATERIALS??工程材料【中英文对照】
TYPES OF MATERIALS
Materials may be grouped in veral ways. Scientists often classify materials by their state: solid, liquid, or gas. They also parate them into organic once living and inorganic never living materials.
幸福生活是奋斗出来的For industrial purpos, materials are divided into engineering materials or nonengineering materials. Engineering materials are tho ud in manufacture and become parts of products. Nonengineering materials are the chemicals, fuels, lubricants, and other material ud in the manufacturing process which do not become part of the product.
This grouping is not exact. Engineering materials may be further subdivided into: 1. Metals. 2. Polymers 3. Ceramics. A fourth type of material 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 polymer advanced composites.
COMMON METALS
Pure metals are ldom ud in common industrial products. Pure
copper is ud in electrical applications, in automotive radiators, and gaskets. Pure aluminum has application in the chemical and electrical industries. However, most metals are alloyscombinations of two or more elements. There are over 25,000 different iron-carbon alloyssteel and over 200 standard copper alloys including a number of brass, bronzes, and nickel silvers. Each of the alloys are identified by a code number.
Steel is an alloy of iron and carbon with other elements added to produce specific properties. 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 type and is often called mild steel. It is relatively inexpensive, ductile, soft, and is easily machined and forged. Mild steel cannot be heat-treatedhardened. Low carbon steel is
看的最远的地方a general purpo steel.
b.?Medium carbon steel. This steel has a carbon content between
0.30 percent and 0.80. Harder and stronger than mild steel, it can be hardened by heat treating. Medium carbon steel is most commonly ud 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, tough part. The material has a carbon content above 0.80 percent. It finds wide u in hand tools, cutting tools, springs, and piano wire.
2?High alloy steel. The steels contain significant amounts of other elements in addition to carbon. The common high alloy steel are:
a.?Stainless steel which is produced 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 ud for a wide range of cutting tools and forming dies.特拉法尔加广场
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c.?Mangane steel which is an alloy containing 21 percent mangane and one percent carbon. This metal is ud in mining, railroad, and construction equipment becau of its high tensile strength.
PROPERTIES OF MATERIALS
All material have their own properties or characteristics. The properties may be arranged into major groups which include: Physical properties.
Mechanical properties.
Chemical properties.南非国家简介
Thermal properties.
Electrical and Magnetic properties.
Optical properties.
Acoustical properties.
余数和除数的关系1.Physical Properties50度灰在线播放
Physical properties, for this discussion, are restricted to tho which describe the basic features of the material. The features are measured or obrved without the u of extensive scientific experiments. The common physical properties are size, shape, density, and porosity.
Size is the overall dimensions of the object. The dimensions, for most materials, 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 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 voidsopen pores in the material. It is generally described as a ratio of open pore volume to total volume of material. This ratio expresd as a percentage. Porosity will provide a measure of liquid-holding power, or the ability of air or gas to move through the material.
2.Mechanical Properties
Mechanical properties mean a material’s ability to carry or resist the application of mechanical forces and loads. The material’s reaction to the forces is usually either deformation shape change or fracture.
Mechanical properties are probably the most important, to manufacturing processing. They determine the extent to which a material may be formed, sheared, or machined.
Typical forces which are applied to a material are tension, compression, shear, and torsion, the forces are ud to form and form and shape materials. Furthermore, materials must withstand excess amounts of the forces in product applications. Since screws are ud to asmble 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.
寻向所志1?Stress-strain
The stress-strain relationship is often ud to study many mechanical properties. Stress is force applied to material. It is usually measured in either pounds per square inch or kilograms per square c
entimeter. 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 incread length of the material per unit of length. Strain is given in
