Possibilities of Using of Surface and Subsurface Waves’ Amplitude-Angle Characteristics for Control of Materials with Surface-Hardened Inhomogeneous Layer

Abstract

Improving the efficiency of ultrasonic control of hardened surface layers of metal products with a heterogeneous structure obtained using different technologies is a pressing problem of industrial production. The purpose of this work was to investigate the possibilities of measuring the depth of the surface inhomogeneous layer of steel objects on the basis of the use of amplitude and amplitude-angle characteristics of surface and subsurface transverse waves. The analysis of ultrasonic methods of control of physical and mechanical properties of metals by using surface and subsurface waves and experimentally investigated amplitude-angular characteristics of surface waves, the maximum angle of which increases by 3° at change of dimensionless layer depth hλ from zero to 0.82. For the first time, the ratio of normalized amplitudes of surface waves taken at certain angles on the amplitude-angle characteristic curve obtained in the echo mode was proposed to be used as correlating parameters with the depth of the hardened layer. As a result of this research, the possibility of using a phased array transducers to solve the above problems. The effect of the hardened layer depth varying from zero to five in the working frequency range of 1.8– 10 MHz on the peculiarities of the refraction effect (including interference) and dependence of the subsurface wave amplitude on the acoustic base has been studied, making it possible to establish conditions that provide for the determination of the hardened layer depth. Circuit solutions have been offered in order to increase the efficiency of control of properties of the surface layers of metal articles on the basis of utilization of small-aperture transducers and ultrasonic reflectors making it possible to form fields of surface waves of different directional pattern.