| Research Abstract |
Nowadays, miniature viscometer being capable of use in the area of endoscope surgery has not been realized. In order to discover how viscosity and elasticity of silicone rubber may be separately determined, silicone rubber known as artificial skin has been investigated experimentally using the impedance change (ΔR ) of a quartz-crystal tuning-fork tactile sensor when its base is in contact with the surface of many kinds of rectangular silicone rubber plates. Eleven silicone rubber plates (the values of the rubber hardness are JIS85, 80, 70, 65, 60, 50, 45, 40, 35, 30 and 20) are investigated in this experiment.ΔR increases linearly according to acoustic impedance ρC (ρ: density of silicone rubber, C : sound velocity of a longitudinal acoustic wave in silicone rubber). The relation between AR and ρC is compared when C is calculated in three cases : in first, C is calculated using Young's modulus of silicone rubber measured by a tensiometer ; in second, using Young's modulus which is con
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verted by the shear modulus measured by a rotating viscometer using the Poisson ratio of silicone rubber, 0.49 ; in third, using a complex Young's modulus which is converted by the complex shear modulus measured by a rotating viscometer. It turns out that the third case shows good linearity between ΔR and ρC. ΔR of the tactile sensor at resonant vibration 32.48 kHz is measured when the tactile sensor is in contact with the center of the surface of rectangular silicone rubber plate in the manner that the thickness and the length of each side of rectangular silicone rubber plate are changed separately : the thickness is 5, 10, 15, 20, 25, and 30 mm with constant length 60 mm of each side and the length of each side is 40, 50, 60, 70, and 80 mm with constant thickness 5 mm. It turns out that it is possible to determine an imaginary part of the complex Young's modulus of silicone rubber from the measurements of ΔR, against thickness of silicone rubber, including information on viscoelasticity as the damping factor α for a longitudinal plane transmitting wave in three layers (the sensor's base, silicone rubber, neoprene rubber). The relation between α and complex Young's modulus (E'+iE"), obtained by solving a longitudinal traveling wave equation for the Voigt model, is derived. A ratio of a real part and a imaginary part of complex Young's modulus ( E'/E") measured for silicone rubber (JIS60 and JIS70) by the tuning fork tactile sensor is 0.043 and 0.049 by use of α, respectively. Less
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