Abstract
Writers pointed out that, in the long time creep test of Hevea gum stock, the large part of the creep strain remained when the stress has been removed, and this permanent set arised only by the pure viscous characteristic or such a material. In order to find the value of η which is a coefficient of the pure viscous term, we must carry out the creep experiment and do successively the creep recovery experiment. The writers added the pure viscous term to the fundamental formula proposed in the previous paper, and derived the equations of the first creep strain, the first creep recovery strain, the second creep strain and the second creep recovery strain. Based upon the theoretical discussion, we caluculated the characteristic values of the Hevea gum stocks from the experimentally observed quantities at the temperature 20°C., 60°C. and 80°C., and discussed the relations of these values.
