No abstract

A general theory of linear viscoelasticity under complex stress is analysed by utilizing the Laplace transformation and is applied to Hertz's contact problem for measuring the creep recovery in the penetration of a steel ball. As in the similar method of uniaxial compression, the temperature dependence of characteristic relaxation times can be computed from the experimental results on (residual depth of penetration creep recovery) ∼θ (temperature) curves by using the analytical results. The temperature dependence is in good agreement with that obtained from the results in uniaxial compression. The method using the RN (Rockwell Number) ∼θ curves obtained at a constant rate of temperature rise (2°C min−1) by a conventional Rockwell testing machine, is recommended as the simplest method and may be successfully used for various polymer solids. The effect of differences in molecular structure on the temperature dependence of mechanical behavior can be demonstrated clearly by this method. The results on thermosetting laminates are also presented. Further, the merits of this creep recovery are discussed.