Abstract
The study of the behaviour of material under the influence of dynamic loads has been pursued, to a large extent, for practical reasons. It has been recognized for almost one hundred years that the deformation behaviour of materials will, in general, change as the rate of loading is increased. Within the realms of the mechanics of solids. this time-dependence of the stress/strain relationship has been treated as a fundamental problem; in the context of engineering practice it has been recognized as being a significant factor controlling the design and manufacture of engineering products. There are three major areas where better understanding of the material is of immediate interest. These are fracture mechanics, metal cutting and forming, and the development of engineering metals and alloys, their heat-treatment, and the production control of their quality. Of course none of the boundaries of these areas can be delineated with any degree of exactness. For example, criteria for fracture resistance are of interest in metal fatigue work, structural dynamics, plasticity, and shortduration life-cycle applications. Also, the growing importanc of plastics in engineering has stimulated the development of new methods of testing to evaluate their suitability in applications traditionally reserved for metals. Because of the high rate-sensitivity of plastics, their deformation and strength under dynamic, loading forms a central part of such evaluations. Much of what has been learned from metals testing is also of direct or indirect interest to the plastics problem.
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