Abstract :
In this work, the yield phenomenon and its
related features have been investigated under the concept
of strain inhomogeneity, emerged inside the material during
deformation processes. This strain non-uniformity in
glassy polymers is either a direct consequence of the local
microstructural density fluctuations existing in such materials
or is the result of the manner by which the free volume
is frozen in the glassy state. Assuming a simple strain
density distribution function, the rate of plastic deformation
can be extracted without any further assumption on a
molecular conformational base or any other thermal activated
process. The two model parameters required have a
physical base related with the magnitude of the free volume
and its fluctuation in glassy polymers. Appling this theory
on the experimental results for three representative amorphous
glassy polymers (PMMA, PS, and PC), all features
of yield process, including strain softening effect, are easily
described.
