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This paper concerns a boundary element method (BEM) for 2D SH-wave scattering in an elastic layer sandwiched by two half spaces. The BEM is based on the integral equation having a Green’s function for a layer as its integral kernel. Since the Green’s function satisfies the interface conditions, numerical integration in the BEM is necessary only on the surface of scattering objects, thus the computational memory can be saved greatly. On the other hand, numerical evaluation of the Green’s function is critical and burdensome. In this paper, a hybrid ray-mode representation of the Green’s function given by Kamel is employed. Numerical aspects of the representation are discussed in some detail, and the BEM code with the Green’s function is developed thereafter. As a numerical example, SH-wave scattering by a cavity in a layer is considered. Some numerical results to investigate the interaction between the cavity and layer interfaces are presented. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Non-axisymmetric guided waves including flexural longitudinal and flexural torsional modes have shown natural focusing characteristics in pipe inspection. A flexural torsional mode theory was developed in this paper based on flexural longitudinal mode theory. Flexural mode experiments were then carried out to show the natural focusing phenomena. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Inspection techniques using guided waves require an accurate prediction of the propagation properties and the physical behaviour of the waves. Properties of these guided waves can be modelled using dispersion curves, which are calculated numerically. However, any curvature along the propagation direction can change the behaviour of the modes compared to those in the straight waveguide. There are currently few studies of the curvature effect along the propagation direction of any waveguide problem. We have used a 2D circumferential waveguide problem to study the curvature effect, from which the phase velocity and the mode shapes have been examined at various curvatures. The percentage difference in velocity of the low order plate modes, as a function of frequency and curvature, has been calculated numerically. Furthermore the changes in phase velocity have been correlated with the changes in mode shapes that are due to the curvature effect. This paper also presents an experimental study to validate the analytical predictions. The experiment involved a sensitive measurement of the change of velocity as the curvature of a waveguide was increased. Reasonably good agreement was obtained between the experimental measurements and the predictions. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The sensitivity of a permanently attached guided wave array for the detection of corrosion damage in plates is studied. The thickness reduction due to corrosion is modeled as a circular part-through hole. The scattering and mode conversion of the A0 Lamb wave mode is calculated numerically employing a three-dimensional finite element model and verified in laboratory experiments. Good agreement is found and the sensitivity of the guided wave monitoring of large areas can be predicted. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

We develop measurement models and scattering models that allow us to predict the ultrasonic response from a side-drilled hole (SDH). The scattering models considered include an explicit model based on the Kirchhoff approximation, as well as an “exact” separation of variables solution. Two measurement models are also derived. One allows for the variation of the incident fields over the cross-section of the SDH while a simpler model neglects those variations. The predicted responses are compared with experimental signals. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

A hybrid three-dimensional boundary element normal mode expansion technique is developed to study the guided wave scattering from an arbitrary shape defect in a plate. Lamb wave incident into a circular through plate hole were studied as an example. The scattered wave displacement field and each normal mode component are given. Mode conversion from Lamb wave to SH wave and vice versa at the defect boundary were observed. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Guided wave calculation using a semi-analytical finite element method is described in this study. Two dimensional discretization modeling and its optimization technique by the use of the symmetry of a pipe are developed for wave propagation in a pipe with a defect. The effect of guided wave focusing, having been developed by Penn State group, is investigated for torsional waves. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Circumferential guided waves are used for the inspection of stress corrosion cracking (SCC). A simplified two dimensional model for crack sizing in pipes is presented. 2-dimensional hybrid boundary element modeling analysis was used to study defect sizing and discrimination in a pipe-like structure. The theoretical results agree with the experiments in utilizing a magnetostrictive sensor (MsS) technology for generating circumferential shear horizontal guided wave in pipe. An approximate 2-dimensional theory based on an axial scan has been developed that improves the defect depth estimate considerably. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]