FINITE-ELEMENT ANALYSIS OF 2-D THERMOVISCOELASTIC RESPONSES BASED ON THE FREE-VOLUME THEORY AND A RECURSIVE FORMULATION

A two-dimensional thermoviscoelastic problem is analyzed by the finite element method based an free volume theory and thermoviscoelasticity. The stresses are computed according to a shift factor: the shift fact or is in turn calculated from the free volume ratio, defined as the fr ee volume divided by the total volume, The free volume ratio depends o n normal stress as well as hydrostatic pressure, in addition to temper ature. The effect of hydrostatic pressure on the free volume ratio can be approached by an equivalent temperature effect. A finite element a nalysis is developed, in which the constitutive equations are formulat ed in recursive form. As a nonlinear analysis, the procedure finds the solution iteratively, using a shift factor as the convergence paramet er. For paly(vinyl acetate) stress-strain curves under several loading conditions ape discussed with respect to temperature and pressure.