Viscoelasticity and viscoplasticity of glassy polymers in the vicinity of the yield point (Q5947061)

The paper aims to present the constitutive equations describing the viscoelastic and viscoplastic behaviour of amorphous glassy polymers under isothermal loading in the sub-\(T_g\) region, where \(T_g\) is the glass transition temperature. The response of this polymeric glass in relaxation tests and in tests with constant rates which account for changes in relaxation spectra, is studied in the vicinity of yield point. The author derives a constitutive model for viscoelastic and viscoplastic behaviour of glassy polymer under uniaxial loading at small strain. The model contains only few constants to be found by fitting data in standard mechanical tests. It is proved that there exists a fair agreement between results of numerical simulation and experimental data for polymetyl methacrylate in the sub-\(T_g\) region.