National Primary Standard for the Units of the Propagation Velocities of Longitudinal, Shear, and Surface Ultrasonic Waves in Solids

Improvements in the national standard for the unit of the propagation velocity of longitudinal ultrasonic waves in solids are examined. The measurement techniques and standard measures for velocity are described. The composition and metrological characteristics of the new standard are discussed. In accordance with the scientific and technical program "Standards of Russia" and the steps planned for the intro- duction of the national primary standard for the unit of the propagation velocity of longitudinal ultrasonic waves in solids, GET 189-2010 (1), work has been under way at the Far Eastern Branch of the All-Russia Research Institute of Physicotech- nical and Radio Measurements (VNIIFTRI) during 2010-2012 to improve the standard, including the development and intro- duction of two new standards facilities as part of the standard for measuring the propagation velocities of shear and surface ultrasonic waves in solids. Thus, the new national primary standard GET 189-2012 ensures the uniformity of measurements of the propagation velocities of the main types of acoustic waves in solids. This standard is at the top of the national verifi- cation scheme for means of measuring the propagation velocity of ultrasonic waves in solids, which establishes the order of transfer of reproduced units to working standards and means of measurement. The need for measurements of the propagation parameters of ultrasonic waves in solids arises from fundamental, as well as applied research. The propagation parameters of ultrasonic waves are used in fundamental research for calculating the elastic constants and moduli of elasticity - the most important characteristics of solids (2). These parameters are also need- ed for determining the physical and mechanical characteristics, as well as the endurance properties of solids, and are of the greatest importance for creating new materials, and in developing techniques for producing and using these in technology and industry. However, the demand for measurements of the propagation velocity of ultrasonic waves is primarily related to the need to ensure the uniformity of measurements in the area of nondestructive testing of the quality of materials and work pieces using acoustic methods and means of measurement. An analysis of Russian and foreign literature in this area shows that the most promising approach for the develop- ment of original standard means of measurement in solid-state acoustics is the use of contactless methods for generating and receiving ultrasonic waves: optical and capacitive (3-8). Optical methods form the basis of the standard GET 189-2012. The standard laser-interference system for measuring the propagation velocity of longitudinal ultrasonic waves in the standard GET 189-2010 (1) serves as the basis for creating the unified standard facility for reproduction of the units of the prop-