Basic for ultrasonic measurement of elasticity constants in anisotropic materials
Andrzej P. Wilczyński Politechnika Warszawska, Instytut Mechaniki i Konstrukcji, ul. Narbutta 85, 02-524 Warszawa
Quarterly No. 2, 2006 pages 21-26
DOI:
keywords: ultrasonic measurements, elastic waves, elastic constants, immersion method, anisotropy, automatic measurements
abstract This paper presents the physical basis of the process of elastic waves motion in solids exhibiting anisotropic properties. As the presentation is supposed to serve in applications of wave theory to practical, possibly automated measurements, the description is purposefully destined for this aim. The selection of the so called immersion method is chosen, with separate transmitter and receiver gauges, as the possibly one which enables automated measurements. This evolves from the way of measuring only time differences between a free ultrasonic pulse run and the one going through the measured specimen, as proposed by Musgrave. Contact methods of measurements require firstly much more special equipment and also checking the actual contact of the specimen and the sensor, up to now done only manually. Furthermore the possible best accuracy of measurements, the zero-crossing method could not be easily applied. For pure research, when only a small number of specimens is tested and the testing is performed by highly qualified persons, the method of measurement is more arbitrary and use of other types of waves is possible, such as Love’s surface waves, which in some cases lead to simple results. In such cases however automated measurements, preferable for industrial purposes are out of the question. The presented relations are sufficient for the measurement purposes but vital problems are the necessary accuracy of measurements of the order of 0.1 ns and the problem of weakly mathematically conditioned at least some of the elastic constants. The necessary accuracy with some difficulty can be finally obtained, but the method of calculation exceeds classical means and requires some special know-how and for industrial reasons will not be presented here.