Development of post-yield large-strain plastic flow

1 Development of post-yield large-strain plastic flow 

A prominent feature both of the annealed and of the quenched initial structures shown in Fig. 8.1 is a strain-softening process in which the plastic resistance decreases monotonically until a strain of around 0.3 is reached at a 

12 (a) DSC scans for annealed and quenched PS using a heating rate of 10 K/min (Hasan and Boyce (1993) courtesy of Elsevier), (b) DSC scans for annealed (top) and quenched (bottom) PS specimens deformed to different levels of compressive strain (from Hasan and Boyce (1993) courtesy of Elsevier), (c) DSC scans for annealed PS specimens deformed to different levels of strain. Note the clear separation of the form of energy evolution below Tg, showing release of stored strain energies of shear transformations, from that above Tg, showing the stored free energies of molecular orientation (from Hasan and Boyce (1993) courtesy of Elsevier). 

These quite different behaviors of energy release shown in the DSC experiments provide a direct demonstration that while the molecular-orientation-induced free-energy storage occurs incrementally in the intense and chaotic segmental rearrangements occurring in the STs as they form, it is a separate and largely 

A further important effect of the plastic response of glassy polymers is a prominent strength-differential (SD) effect, which is a consequence of the usual dilatant character of an ST whereby the transformation shear strain is generally kinematically associated with a coupled transformation dilatation e, as discussed earlier. This transformation dilatation interacts strongly with a mean normal stress, (7n, when one is present, i.e., with pressure in compression flow and negative 

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