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In this study, we experimentally evaluated the application of multiple scattering theory for measuring ultrasonic attenuation. Based on the independent approximation theory, the method adopted for calculating the attenuation of coherent waves through air with fine dust is discussed. To obtain a scattering wavefield, a unique ultrasonic scattering hardware was developed, and signal processing schemes were suggested. Four cases of standard particle doses (0, 0.004, 0.008, and 0.012 g) were investigated inside a chamber. The results obtained from the experiments demonstrate that the proposed signal processing approach successfully calculates the scattering attenuation, which correlates well with the applied doses of fine dust. In addition, we discuss the irregular shape and composition of fine dust relative to the scattering cross-section. [ABSTRACT FROM AUTHOR]

In this study, a method is presented for estimating the number density of fine dust particles (the number of particles per unit area) through numerical simulations of multiply scattered ultrasonic wavefields. The theoretical background of the multiple scattering of ultrasonic waves under different regimes is introduced. A series of numerical simulations were performed to generate multiply scattered ultrasonic wavefield data. The generated datasets are subsequently processed using an ultrasound data processing approach to estimate the number density of fine dust particles in the air based on the independent scattering approximation theory. The data processing results demonstrate that the proposed approach can estimate the number density of fine dust particles with an average error of 43.4% in the frequency band 1–10 MHz (wavenumber × particle radius ≤ 1) at a particle volume fraction of 1%. Several other factors that affect the accuracy of the number density estimation are also presented. [ABSTRACT FROM AUTHOR]

This paper presents an air-coupled ultrasonic nondestructive evaluation approach based on the attenuation characteristics of guided waves to characterize interface bonding conditions of steel-clad concrete structures. Analytical guided wave modal solutions for various interface bonding conditions are obtained using the global matrix technique. The analytical results indicate that attenuation behavior of the fundamental symmetric (S0) guided wave mode is sensitive to interface bonding condition. A signal processing scheme is proposed to extract a dimensionless damage index, the normalized S0 mode magnitude, which reflects the attenuation behavior of the S0 mode. A series of numerical simulations are performed to verify the utility of the parameter to characterize interface bond condition. The feasibility of the testing approach is then established by experiments on steel-clad concrete specimens with different interface bonding conditions. The numerical simulation and experimental results demonstrate that interface bonding conditions of steel-clad concrete structures can be quantitatively evaluated using the proposed approach. [ABSTRACT FROM AUTHOR]