ABSTRACT
Yield is the onset of plastic deformation in a material under an applied load. This is an important process because it determines the practical limit of use more than does the ultimate rupture and because it is the first step in polymer processing by forming, rolling, or drawing. Although the idea of yield is a simple concept, its experimental determination is not easy. Definitions of terms are particularly important since not everyone agrees even on the operational definition of the word yield. The presentation here makes use of comparisons with results for metals and ceramics, as well as with amorphous polymers, in order to put the crystalline polymer results in perspective.
