Precision measurements of the propagation velocity for longitudinal ultrasonic waves in solids by the resonance method
摘要
We study the possibility of extension of the frequency range and functional capabilities of the GÉT 189-2014 State Primary Standard of the units of propagation velocity and damping coefficient for ultrasonic waves in solids in reproducing and transmitting the unit of propagation velocity of longitudinal ultrasonic waves in solids with the help of the resonance measurement method. This characteristic of solids is used for the thickness measurements, for the purposes of flaw detection, and in other scientific and practical fields. We present the results of investigations of the resonance method of measuring the velocity of propagation of longitudinal ultrasonic waves in solids. In the experiments, we used velocity measures made of optical glasses and leucosapphire and allowing one to measure velocities within the range 4000–11,200 m/sec with its frequency dispersion smaller than 10−4. For the excitation and recording of the longitudinal ultrasonic waves within the frequency range 1–100 MHz, we apply contactless broadband capacitive transducers. The accuracy of the measurement data obtained by the resonance method is analyzed and compared with the data of the impulsive laser method applied in the GÉT 189-2014. It is shown that the absolute error of measurements of the propagation velocity of longitudinal ultrasonic waves in solids defined as the deviation from conventional true value of the analyzed quantity and obtained by the resonance method does not exceed 1 m/sec depending on the material of the measure, while the relative error is smaller than 10−4. In the low-frequency range, we observe a monotonic increase in the measured velocity of longitudinal ultrasonic waves in the case of applying a velocity measure made of leucosapphire, which may be explained by the physical properties of this material. The obtained results confirm the possibility of extension of the frequency range and functional capabilities of the GÉT 189-2014 in the case of application of the resonance method for measuring the propagation velocity of longitudinal ultrasonic waves and contactless broadband capacitive transducers that do not require high (optical) quality of the surfaces of certified measures.