Ultrasonic Characterization of Interfaces in Composite Bonds

The inverse determination of imperfect interfaces from reflection spectra of normal and oblique incident ultrasonic waves in adhesive bonds of multidirectional composites is investigated. The oblique measurements are complicated by the highly dispersed nature of oblique wave spectra at frequencies above 3MHz. Different strategies for bond property reconstruction, including a modulation method, are discussed. The relation of measured interfacial spring density to the physico-chemical model of a composite interface described by polymer molecular bonds to emulate loss of molecular strength on an adhesive composite interface is discussed. This potentially relates the interfacial (adhesion) strength (number of bonds at the adhesive substrate interface) to the spring constant (stiffness) area density (flux), which is an ultrasonically measurable parameter

Variance of transmitted power in multichannel dissipative ergodic structures invariant under time reversal

We use random matrix theory (RMT) to study the first two moments of the wave power transmitted in time reversal invariant systems having ergodic motion. Dissipation is modeled by a number of loss channels of variable coupling strength. To make a connection with ultrasonic experiments on ergodic elastodynamic billiards, the channels injecting and collecting the waves are assumed to be negligibly coupled to the medium, and to contribute essentially no dissipation. Within the RMT model we calculate the quantities of interest exactly, employing the supersymmetry technique. This approach is found to be more accurate than another method based on simplifying naive assumptions for the statistics of the eigenfrequencies and the eigenfunctions. The results of the supersymmetric method are confirmed by Monte Carlo numerical simulation and are used to reveal a possible source of the disagreement between the predictions of the naive theory and ultrasonic measurements.Comment: 10 pages, 2 figure

Visualization of spherical objects in a reflection acoustic microscope

An expression is obtained for the output signal of a reflection acoustic microscope during the scanning of a spherical object. It is shown that the nature of the image of such an object depends significantly on the position of the focal plane relative to the centre of curvature of the sphere. The experimental results are in good agreement with theory

Visualization of spherical objects by reflection acoustic microscope

An expression for the output signal of a reflection acoustic microscope corresponding to a spherical object is presented in this paper as spherical function expansion. The character of the image is shown to depend on the focal plane position with respect to spherical objects center. The size of spherical objects image is smaller than a real particle dimension at any focal plane position. Experimental data agree with the theory

Imaging of spherical objects in a reflecting acoustic microscope

An expression is derived for the output signal of a reflecting acoustic microscope in scanning of a spherical object. It is shown that the character of the image of such an object depends significantly on the position of the focal plane relative to the center of curvature of the sphere. The experimental results are in good agreement with the theory