超音波パルスエコー計測による球形固体粒子の大きさと材質の識別

抄録

When an ultrasonic pulse reflects from a solid sphere, the echo waveform is determined by the size, position, and acoustic impedance of the sphere. By analyzing the ultrasonic pulse echo, it is expected to estimate the information about solid sphere. To evaluate the feasibility of its estimation, echoes from a solid sphere fixed in a water tank were measured and analyzed while changing its relative position from the transducer. Different sized glass and steel sphere were used in the experiment. As a result, an echo comprises two parts; one is the first reflection which is reflected from the front surface of a solid sphere, and the other is complex second reflection. It seemed that the second reflection included multiple reflection inside a sphere. We extracted the peak amplitude of these first and second reflected waves. We found that the amplitude ratio between two reflected waves showed a good correspondence with the material of a sphere. By correcting the amplitude to account for the attenuation of ultrasonic pulse in water, it is also found that it was possible to estimate the size of a sphere after eliminating the effect of distance between the transducer and a sphere.