THERMOVISCOELASTIC THEORY OF FREEZING OF STRESS AND STRAIN IN A SYMMETRICALLY COOLED INFINITE GLASS PLATE

The Gardon and Narayanaswami theory of annealing and tempering of glas s is rederived in a unifying way using the framework of the theory of thermoviscoelasticity. It is extended by including the effect of isoth ermal pressure relaxation in addition to the relaxation of shear stres s. In the new theory, relaxation of shear stress, isotropic stress (pr essure) and thermal stress, which causes thermal expansion, are treate d on the same level. The thermal expansion coefficient, a frequency-de pendent quantity like bulk and shear modulus, has high- and low-freque ncy limits identified with the thermal expansion coefficients of glass and liquid. The results of numerical calculation of stresses and stra ins in a symmetrically cooled infinite plate for the extended theory i llustrate the decisive importance of the dispersion of the thermal exp ansion coefficient.