Abstract: This paper discusses the expressions of macroscopic mechanics for theuniaxial-compression stress-strain behaviour of glassy polymer PMMA, i.e. the constitutive relations, according to the experimental data. A non-linear viscoelastic- plastic constitutive model composed of an activation dashpot by taking into account of the strain-hardening effect coupl in series with a standard linear solid or a Maxwell body is suggested. The comprehensive constitutive equations both in differential and integral forms are p...