1960 年 26 巻 8 号 p. 778-782
It is well known that from the observation of the period of torsional oscillation of a wire suspending a weight, we can determine the modulus of rigidity of the wire. This method can not be applied to the case of a netting cord, because a heavy weight hung down by a cord rotates about the axis of the cord gradually untwisting that cord. If a weight attached to a cord is light, it does not rotate, and can be set in torsional oscillation. But this oscillation is damped so rapidly that the measurement of the period is difficult.
Now, in the present experiment, the upper end of a cotton cord suspending a light weight is fixed to the lower end of a metal rod which is held vertically, and can be made to oscillate about its axis at a given amplitude. The ratio (m) of the amplitude of the lower end to that of the upper end of the cord, and the phase difference ( ?? ) between the oscillations of the lower end and the upper end were observed. From the analysis of the observed values of m and ?? depending on the frequency of oscillation, it was found that the behaviour of the cotton cord can be understood by the Voigt model. Further, the rheological constants for cotton cords of various diameters were obtained.