A model for post-yield plastic flow of glassy polymers

2 A model for post-yield plastic flow of glassy polymers 

We start by relabeling that the Helmholtz free energy, Fq of an ST in shear flow in a glassy polymer as given by eq. (8.7) is now its self-energy  

This gives the self-operational Helmholtz free energy of an ST in a typical glassy polymer as 

However, for uniaxial compression or tension, where a significant interaction energy must also be considered to be part of an ST, the overall transformation Helmholtz free energy becomes, with the addition of an interaction energy Bint, 

These additional considerations give the threshold plastic resistance Tc in compression as V3ts in shear, and, with the interaction energy present, the normalized compression threshold resistance becomes, where is a negative quantity, 

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