Chp 01 - Chapter 1 The structure and bonding of atoms 1.1...

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1.1 The realm of materials science In everyday life we encounter a remarkable range of engineering materials: metals, plastics and ceramics are some of the generic terms that we use to describe them. The size of the artefact may be extremely small, as in the silicon microchip, or large, as in the welded steel plate construction of a suspension bridge. We acknowledge that these diverse materials are quite lit- erally the stuff of our civilization and have a deter- mining effect upon its character, just as cast iron did during the Industrial Revolution. The ways in which we use, or misuse, materials will obviously also influ- ence its future. We should recognize that the pressing and interrelated global problems of energy utilization and environmental control each has a substantial and inescapable 'materials dimension'. The engineer is primarily concerned with the func- tion of the component or structure, frequently with its capacity to transmit working stresses without risk of failure. The secondary task, the actual choice of a suitable material, requires that the materials scientist should provide the necessary design data, synthesize and develop new materials, analyse fail- ures and ultimately produce material with the desired shape, form and properties at acceptable cost. This essential collaboration between practitioners of the two disciplines is sometimes expressed in the phrase 'Materials Science and Engineering (MSE)'. So far as the main classes of available materials are con- cerned, it is initially useful to refer to the type of diagram shown in Figure 1.1. The principal sectors represent metals, ceramics and polymers. All these materials can now be produced in non-crystalline forms, hence a glassy 'core' is shown in the diagram. Combining two or more materials of very different properties, a centuries-old device, produces important composite materials: carbon-fibre-reinforced polymers (CFRP) and metal-matrix composites (MMC) are mod- ern examples. Figure 1.1 The principal classes of materials (after Rice, 1983). Adjectives describing the macroscopic behaviour of materials naturally feature prominently in any lan- guage. We write and speak of materials being hard, strong, brittle, malleable, magnetic, wear-resistant, etc. Despite their apparent simplicity, such terms have depths of complexity when subjected to scientific scrutiny, particularly when attempts are made to relate a given property to the internal structure of a material. In practice, the search for bridges of understanding between macroscopic and microscopic behaviour is a central and recurrent theme of materials science. Thus Sorby's metallurgical studies of the structure/property relations for commercial irons and steel in the late nineteenth century are often regarded as the beginning of modern materials science. In more recent times, the enhancement of analytical techniques for characteriz- ing structures in fine detail has led to the development and acceptance of polymers and ceramics as trustwor-
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This note was uploaded on 12/05/2011 for the course MSE 4100 taught by Professor Hennig during the Fall '11 term at Cornell.

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Chp 01 - Chapter 1 The structure and bonding of atoms 1.1...

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