Beyond Elastic Behavior
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Polymers are normally ductile in nature and have the capability to yield under high enough stress. Yielding, without which the material would break in a brittle manner, is helpful in structures to smooth out peak stresses and convert them into strain concentrations. Also, yielding allows sizing of a part to be done on the basis of strength of materials formulas without worrying about stress concentrations, at least initially. In plastics the distinction between yield and ultimate strength was considered unnecessary. However, the trend has changed, especially after the thermo-forming process became commercially viable. Hence, there is a clear need to understand the stress-strain relationship while yielding is in progress. In this chapter, we discuss the phenomenological aspects of yielding and another similar mode of failure called “crazing”.
KeywordsPrincipal Stress Stress Component Deviatoric Stress Elastic Behavior Hoop Stress
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