DELAYED ELASTICITY IN RELAXATION PROCESS OF GLASSES FAR BELOW THE GLASS-TRANSITION TEMPERATURE

Deformations of pre-annealed lead-silicate glass fibers were measured by the fiber-bending method during loading and unloading below the gla ss transition temperature. Burger model consisting of Maxwell and Voig t elements was used for the evaluation of elasticity, delayed elastici ty and viscosity. In the loading process, it was found that the deform ation due to the viscosity increases with time. However, the deformati on due to the delayed elasticity increases rapidly for a short time an d decreases with further increase in time. In the temperature range of the measurement, the viscosity of Maxwell element, representing pure viscosity decreases with increasing temperature. The viscosity of Voig t element consisting of the delayed elasticity decreases with increasi ng temperature and is one magnitude order lower than that of Maxwell e lement. The elastic constant of Voigt element consisting of the delaye d elasticity decreases slightly with increasing temperature. In the un loading process, the delayed elasticity was analyzed, assuming that th e elasticity of Voigt element is the same as that in the loading proce ss.