液体中の超音波音場における各種材料の発熱

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In the preceding paper, the authors reported the results of surface heating and absorption heating of a small solid body irradiated with ultrasonic waves in a liquid medium. We continued this research further so as to elucidate some unclarified phenomena. This report consists of two parts; one is concerned with further experiments on surface heating itself and the other is concerned with heating in general including absorption heating of various metallic and plastic materials. 1. Surface Heating (1) We attempted to find the relation between the heating and the surface roughness of the specimen. The apparatus used is shown in Fig. 1. The specimens were disks of fused quartz with a diameter of 4 mm and a thickness of 2 mm. The roughness was made by ditching as shown in Fig. 2. The number, depth and width of the ditches were changed. The results are shown in Fig. 6. The temperature rise is almost linearly proportional to the actual area of the surface. (2) We investigated how the heating of the specimen varied with incident angle of waves. The specimen used was a fused quartz plate, with an area of 20×20 mm^2 and a thickness of 2 mm. Fig. 7 illustrates the arrangement of the experiment. The temperature rise was measured at the center of the front surface by means of a very tiny thermocouple and its plate was rotated around the vertical axis as shown in the figure. The temperature rise is the solid curve of Fig. 8. In the smaller angle region (up to about 10°), we could not get steady results because of the standing wave effect, but the temperature rise increased with increasing angles between about 15°and 80°. This phenomenon was assumed also to be due to surface heating, because the velocity component of the liquid particles parallel to the surface increased with the above angles. (3) We investigated the relation of the heating and the surface materials of the specimens. On the fused quartz plate mentioned above, several kinds of metal film were prepared by vacuum deposition and also a thin plastic film was painted. The method of measurement was the same as that of (2). The authors found that the rise in temperature were almost independent of the surface materials deposited or pained, and were about the same as the result in the case of bare fused quartz plate. We assumed that the reason for this phenomenon was that the wetting between these materials tested and oil should be almost of the same order. 2. Heating of various materials We tried to investigate the relation of surface heating and absorption heating of various materials with different ultrasonic absorptions. The shape of the specimen and apparatus of measurement were the same as 1. (1). The depth and width of ditches were 0. 5 mm and 0. 2 mm respectively. The solid curves of Fig. 12 show the relation between viscosity of liquid and the saturated temperature rise of the specimen. The temperature rises of each of the materials for viscosity are expressed by equation (7), where θ is the temperature rise, η the coefficient of viscosity and A, α constants. The first term corresponds to surface heating, the second to absorption heating and the third to the heating of the liquid itself. The result is shown in Fig. 13. From these graphs, we could obtain the approximate magnitude of surface heating and absorption heating of various materials. For materials with low absorptivity, such as fused quartz, the main heating was that of surface heating. For materials with absorptivity of middle grade, such as Sn or Pb, both surface heating and absorption heating appeared together. For materials with high absorptivity, such as plastics, the heating was absorption heating.
社団法人日本音響学会の論文
1977-01-01

液体中の超音波音場における各種材料の発熱

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