Bai Yunshan, Liu Yuanxue, Gao Guangjian, Cui Dandan, Chen Han «Estimating the Azimuth of Acoustic Emission Source in Concrete Plate-Like Structures using a Non-Contact Sensor Unit» Acoustical Physics, 70, № 1, с. 130-142 (2024)

Location of damage sources is an important aspect of structural health monitoring research. Acoustic emission (AE) technology is broadly concerned due to its potential advantages in damage monitoring and source localization. However, the traditional positioning method is based on the arrival of P wave, and the non-uniformity of concrete materials is not considered, resulting in poor accuracy at large distances. This paper describes a non-contact AE localization method using leaky Rayleigh waves via a new air-coupled MEMS microphones array unit. Compared with traditional contact detection, this method is convenient for rapid setup and monitoring in a wider range. The feasibility of the non-contact AE localization method was verified by numerical simulation and experiments. Azimuth (direction of arrival) of AE source is a key source parameter for damage location. The research shows that this method can determine the azimuth of AE source at different positions, the results are close to the actual coordinates. Non-contact monitoring method proposed in this paper is the basis for further research on the failure prediction of concrete plate-like structures such as tunnel lining and bridge deck.

Gladkov S.O. «On the Sound Speed in Multiphase Systems» Acoustical Physics, 70, № 1, с. 29-34 (2024)

The general dependence of the sound speed has been calculated c_s in a two-phase system, such as liquid+gas and gas+liquid, as a function of the concentration x of an additional phase and thermodynamic parameters of the mixture. It is shown that in limiting cases, when the concentration tends to zero or unity, formulas are obtained whose numerical values agree well with the known values for the sound speed in water and air. This formula is generalized to multicomponent systems. The found functional relationship is illustrated graphically c_s(x) for the case of a two-phase medium, and its qualitative and quantitative agreement with the results of other authors is shown demonstrated.

Kurashkin K.V., Kirillov A.G., Gonchar A.V. «Use of Longitudinal Critically Refracted Waves to Determine Residual and Temperature Stresses in Rails» Acoustical Physics, 70, № 1, с. 51-57 (2024)

The possibility of using longitudinal critically refracted waves for acoustic strain gauging of longitudinal residual and temperature stresses in rails is studied. The influence of stress and temperature on the propagation velocity of elastic waves in rail steel is analyzed theoretically. An algorithm is presented for determining longitudinal stress in a rail by measuring the propagation time of longitudinal critically refracted waves. The operational principle is described, and the main parameters of an acoustic strain gauge device are presented, in which a differential scheme for measuring the propagation time of longitudinal critically refracted waves is implemented. Longitudinal critically refracted waves that propagate along a rail are emitted and received from the rolling surface of a rail head using contact piezoelectric transducers fixed on the polymethylmethacrylate wedges. The results of acoustomechanical and temperature tests are presented. The measurement errors are calculated. The results of determining the level of residual welding stresses in the head of a new rail are presented. The experimental results are compared with theoretical estimates of the stresses that arise in a rail under the influence of temperature, as well as with available data in the literature on residual stresses in rails.

Anosov A., Granovsky N.V., Belyaev R.V., Erofeev A.V., Sanin A.G., Mansfeld A.D. «Correlation Measurements of Thermal Acoustic Radiation Using a Sensor Array» Acoustical Physics, 70, № 1, с. 21-28 (2024)

An array consisting of three sensors was used for correlation measurements of thermal acoustic radiation. For the first time, all cross-correlation functions were obtained for each pair of sensors. The measurements were carried out at two positions of the source (a heated narrow Teflon cylinder), the distance between which was equal to half the spatial period of the cross-correlation function of adjacent sensors. The measured correlation functions were in antiphase, which corresponds to the calculated correlation functions of thermal acoustic radiation. To pass from correlation functions to temperature distribution, spatial cross-correlation functions for adjacent and the outermost sensors in the array are summed. The correlation methodology makes it possible to significantly increase the spatial resolution of the method.