抄録
The creep behavior of Lincoln wool fiber in water is studied by varying temperature (from 10°C to 97°C.), stress (from 9 to 55×107 dyne/cm2) and initial extension rate (from 70 to 300%/min.). There are two difficulties in the creep experiment. The first is that constant static stress could not be applied instantaneously, and the second is that the creep strain within a few seconds may not be measured accurately. In this experiment, the creep strain can be magnified by optical lever technique (Fig. 1) and 0.001mm, deformation is detected by the cinematograph which projects the scale. The instantaneous strain at 0.1 second can be measured.
The results of this experiment are as follows:
(1) The instantaneous strain depends upon the rate of loading. The higher the speed of extension under the same load, the lower the instantaneous strain.
(2) According to the successive creep and its recovery tests, the creep curves nearly coincide with each other after several repeated tests.
(3) The length of the fiber is well reversible from creep test under 2% extension (in Hookean region) in water. The specimen is more completely recovered at a temperature higher than that of the creeping temperature. The fiber, although, contracts after creep test under low extension above 60°C. It is suggested that supercontraction and permanent set depend upon the amount of broken and re-formed hydrogen or polar bonds. The creep recovery from high extension is not sufficient during short time (15min.) below 60°C.
(4) Beyond the yield point, the instantaneous strain increases remarkably with rising of the temperature, whereas a little decrease of Young's modulus is obtained in Hookean region.
