ABSTRACT
A good knowledge of some of the constants used in the study of the properties of materials is vital in most branches of engineering, especially in mechanical, manufacturing, aeronautical and civil and structural engineering. For example, most steels look the same, but steels used for the pressure hull of a submarine are about 5 times stronger than those used in the construction of a small building, and it is very important for the professional and chartered engineer to know what steel to use for what construction; this is because the cost of the high-tensile steel used to construct a submarine pressure hull is considerably higher than the cost of the mild steel, or similar material, used to construct a small building. The engineer must not only take into consideration the ability of the chosen material of construction to do the job, but also its cost. Similar arguments lie in manufacturing engineering, where the engineer must be able to estimate the ability of his/her machines to bend, cut or shape the artefact s/he is trying to produce, and at a competitive price! This chapter provides explanations of the different terms that are used in determining the properties of various materials and a description is given of the standard tensile test used to obtain the strength of various materials, especially the strength and material stiffness of metals. This is aided by a standard tensile test, where the relationship of axial load on a specimen and its axial deflection are described. The engineer can tell a lot from the results of this experiment. For example, the relationship between load and deflection is very different for steel and aluminium alloy and most other materials, including copper, zinc, brass, titanium, composites, and so on. By carrying out this test, the engineer can determine the required properties of different materials, and this method, together with its interpretation, is discussed in this chapter. Proof stress, ductility, shear stress and shear strain, Poisson’s ratio, hydrostatic stress, composite materials, thermal strain, compound bars, failure by fatigue and failure due to creep are all considered in this chapter.
