Abstract
A measuring method for temperature dependence of viscoelastic behavior of high polymers by means of creep strain recovery is extended to the penetration case of steel ball in this paper. A general theory of linear viscoelasticity under complex stress state is analyzed mathematically by utlizing Laplace transform and is applied to the Hertz's contact problem for computing the creep recovery in the penetration of steel ball. In the same manner as compression method, the temperature dependence of characteristic relaxation times is predicted from the experimental results on zor (the recovery amount in penetration creep)-θ (temperature) curves and is compared with Williams-Landel-Ferry's law in regard to its validity. The method by Rockwell Number (RN)-θ curves which are obtained in the constant rate of temperature rise(2°C/min) by conventional Rockwell machine, is recommended as a simple method and is successfully used for various high polymer solids so that the effect of internal molecular structure on transition and flow temperatures can be clearly demonstrated. Further, the merits of these creep recovery methods in both compression and penetration are discussed.
