Optimization of the method for determining the velocity of surface acoustic waves

Abstract

The methodological aspects of measuring the velocity of Rayleigh surface waves are considered. The main attention is paid to the method for determining the change in surface wave velocity under the influence of certain factors on the object of study. The main sources of error in determining the change in surface acoustic wave velocity are discussed. The use of a transducer with rigidly connected elements for exciting and recording surface acoustic waves to determine the change in velocity is examined. A distinctive feature of such a transducer is the stable measurement base length, which eliminates the need for its determination during the measurement process. It is shown that the main sources of decreased surface acoustic wave measurement accuracy are the temperature instability of the measuring equipment and the transducer, as well as the instability of the acoustic contact layer between the transducer ele-ments and the object of study. The instability of the acoustic contact is caused by the uncertainty in the distribution of the coupling fluid between the transducer and the specimen during the bonding process, leading to changes in the acoustic signal propagation time. The source of temperature instability is random changes in the ambient temperature. Another source of such instability is the heating of equipment elements due to the release of heat when electrical and acoustic energy pass through them. This is particularly important for the transducer, where electrical energy is converted into acoustic energy, as a significant portion of it is transformed into heat. The magnitude of temperature instability arising from prolonged system operation, as well as the instability caused by the installation of the transducer on the object of study, is experimentally evaluated. The use of a reference sample to compensate for the temperature instability of the measurement system is considered. The possibility of using a measurement scheme with a reference sample to reduce temperature instability and the error caused by the instability of the acoustic contact between the transducer and the object of study is analyzed.