This work considers a rubber cylinder under zero axial force that elongates in response to the normal stresses produced during torsion (the Poynting effect). The combined elongation and twisting deformation occurs at an elevated temperature at which the rubber undergoes time-dependent scission and re-crosslinking of its macromolecular network junctions. A constitutive theory accounting for this microstructural change is used in an analytical and numerical study of the interaction of the deformation and the scission or re-crosslinking process. Examples show the time-dependence of elongation for several twist histories.
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