1958 年 27 巻 2 号 p. 98-103
A new simple method has been developed for the determination of visco-elastic property of a liquid at ultrasonic frequencies. A composite resonator is made by comenting a brass reed to the lower end of a longitudinal quartz resonator. The dynamic viscosity and rigidity of a liquid are calculated from the decrease of both the resonant frequency and mechanidal Q-value of the composite resonator when the lower half of the brass reed is immersed in the liquid. This method is less sensitive compared with the torsional crystal method, but is very simple in construction and can successfully be applied to high loss materials.
Some liquids and gels have been investigated in a preliminary evaluation of the behaviors of the apparatus. The gel of aqueous solutions of gelatin shows appreciable rigidity at 100 kc/s, the modulus of rigidity being proportional to the square of concentration. The dynamic rigidity of silicone oil at 100 kc/s increases with increasing molecular weight, but above a critical molecular weight the increase is very slow and becomes asymptotic to a value of 16.5×105dyn/cm2 at 20°C. This asymptotic value decreases with increasing temperature. The viscosity of molten cetyl alcohol shows an abrupt increase at solidification point and it is suggested that this apparatus can be used for precise determination of solidification point of such a waxy material.