In this article we will discuss about the relationship between structure and property of electrical engineering materials.
It is customary to say that every known type of material must be considered for use by the engineer. Admittedly, some materials are not used widely because of poor availability, initial properties, service performance or high cost. Others, such as iron, steel, paper, concrete, water and plastics find extensive uses.
This is because of the fact that different materials possess different properties, e.g., opacity is a property of metals, transparency is a property of many minerals, elasticity is a property of solids, and viscosity is a property of liquids and so on. We can define a material property quite generally by saying that it is a factor which affects quantitatively the response of a given material to imposed conditions.
That is, in engineering applications it is not enough to know how a material responds to imposed constraints but at the same time we must also learn how much it responds and it depends only on the internal structure of the material itself. The internal structure of a material is altered when that material is deformed and hence there is a change in properties. The internal structure of materials comprises atoms associated with their neighbours, molecules and microstructures.
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A material in a product possesses a set of properties—strength, hardness, conductivity, density, colour and so on—chosen to meet the design requirements. It will retain these properties indefinitely provided there is no change in the internal structure of the material.
If the product encounters a service condition that alters the internal structure, however, we must expect the properties and behaviour of the material to change accordingly. For example, rubber gradually hardens when exposed to light and the air, aluminium cannot be used in many locations of a supersonic planes, a metal can fatigue under cyclic loadings, a drill of steel cannot cut as fast as a drill of high speed steel and a semiconductor can be damaged by nuclear radiation and so on.
Therefore, the engineer must consider not only the initial demand but also those service condition that will alter the internal structure and hence the properties of the material. In turn, the properties influence the performance of a material both during manufacturing and during service. Therefore, to change the performance we must modify its internal structure.
The structure property relationship (Table 1.2) gives the material engineer a basis for understanding the nature and behaviour of a wide variety of materials. With such a basic background, the engineer should have the potential to anticipate the properties of material not yet studied, or for that matter not yet developed.
