In analyzing the results of tension tests, and in certain other situations, it is useful to work with true stresses and strains. Note that engineering stress and strain are most appropriate for small strains where the changes in specimen dimensions are small. True stresses and strains differ in that finite changes in area and length […]
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A wide variety of tensile behaviors occur for different materials. Even for a given chemical composition of a material, the prior processing of the material may have substantial effects on the tensile properties, as may the temperature and strain rate of the test. Trends for Different Materials Engineering metals vary widely as to their strength
Elastic Constants Initial portions of stress–strain curves from tension tests exhibit a variety of different behaviors for different materials as shown in Fig. 1. There may be a well-defined initial straight line, as for many engineering metals, where the deformation is predominantly elastic. The elastic modulus, E, also called Young’s modulus, may then be obtained
An engineering component, such as a beam, shaft, tension member, column, or machine part, must not deform excessively or fail by fracture or collapse. At the same time, the cost and often the weight must not be excessive. The most basic consideration in avoiding excessive deformation is to limit the deflection due to elastic strain.
Mechanical Testing of Materials Samples of engineering materials are subjected to a wide variety of mechanical tests to measure their strength or other properties of interest. Such samples, called specimens, are often broken or grossly deformed in testing. Some of the common forms of test specimen and loading situation are shown in Fig. 1. The
A composite material is made by combining two or more materials that are mutually insoluble by mixing or bonding them in such a way that each maintains its integrity. Some composites, plastics modified by adding rubber particles, plastics reinforced by chopped glass fibers, cemented carbides, and concrete. These and many other composite materials consist of
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Ceramics and glasses are solids that are neither metallic nor organic (carbon-chain based) materials. Ceramics thus include clay products, such as porcelain, china, and brick, and also natural stone and concrete. Ceramics used in high-stress applications, called engineering ceramics, are often relatively simple compounds of metals, or the metalloids silicon or boron, with nonmetals such
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Properties of Polymers Polymers are materials consisting of long-chain molecules formed primarily by carbon-to-carbon bonds. Examples include all materials commonly referred to as plastics, most familiar natural and synthetic fibers, rubbers, and cellulose and lignin in wood. Polymers that are produced or modified by man for use as engineering materials can be classified into three
Properties of Nonferrous Metals Quenching and tempering to produce a martensitic structure is the most effective means of strengthening steels. In the common nonferrous metals, martensite may not occur; and where it does occur, the effect is not as large as in steels. Hence, the other methods of strengthening, which are generally less effective, must
Iron-based alloys, also called ferrous alloys, include cast irons and steels and are the most widely used structural metals. Steels consist primarily of iron and contain some carbon and manganese, and often additional alloying elements. They are distinguished from nearly pure iron, which is called ingot iron, and also from cast irons, which contain carbon