Absfmcf-A uniform geometrical theory of diffraction (UTD) solution is obtained for the field exterior to a two-dimensional circular cylinder with a thin lossy dielectric coating. The solution is convenient for engineering applications due to its simple ray format. In the lit region, the geometrical optics (GO) solution consists of the direct incident ray and the reflected ray. In the shadow region, the geometrical theory of diffraction (GTD) employs the usual creeping-wave format to calculate the diffracted field. In the transition regions adjacent to the shadow boundaries where the pure ray optical solution fails, a "universal" transition integral is employed for the UTD solution to calculate the field. Numerical values for the essential transition integral is deduced, via a heuristic approach, from alternative representations of the Green's function for a circular cylinder with coating. Numerical results obtained from the UTD solution show excellent agreement with the eigenfunction results for cylinders with thin dielectric coating.

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ABSTRACT. 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.

The scattering from three-dimensional cracks has been analyzed and measured. The crack geometry is a rectangular groove in a perfectly conducting surface. The groove forming the crack may he terminated with an open aperture creating a slit in the conducting surface or with an impedance boundary creating a trough. The scattered fields from a crack were analyzed with two types of scattering mechanisms, a component directly related to the scattered fields from a two-dimensional crack and a traveling wave component. scr'cc' condvc'or /

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