We studied on the creep of Sugi (Cryptomeria japonica D. Don) and examined the relationship between the creep and the temperature.
The constant load within the proportional limit was applied with a balance to the end of a cantilever(0.2×1.0×12.0cm) in the distillated water. The temperatures of the water were 0.5°, 20°, 40°, 60°, 80℃ (±0.5°-1.0℃). The deflection of the cantilever was measured by comparator during 200 minutes.
Then in each specimen the ratio
ε = (y-y_0)/(y_0)
y : deflection at time t
y_0 : deflection at time
0.5 min
was nearly constant at the same temperature. These ratios at different temperatures are essentially equal except a constant η :
logε = g(ζ) + η,ζ = log t
where g(ζ) is a function of logt. The constant η is linear to temperature (cf. Fig. 7). And g(ζ) is approximately a linear function of ζ (=log t) within the range of our measurements, although this approximation is rough (cf. Fig.6). Then the time-temperature superposition principle is concluded like a generalized voigt model, of which retardation times τ are decreasing with increasing temperature and represented by τ/a_θ(a_θ＞1, suffix θ is the difference from the standard temperature).