Showing papers by "Subhendu K. Datta published in 2000"

On ultrasonic guided waves in a thin anisotropic layer lying between two isotropic layers

Abstract: In this paper, dispersion of guided waves in a three-layered sandwich plate is considered. The focus here is on a configuration consisting of a thin anisotropic layer sandwiched between two identical isotropic layers. This configuration could model, for example, a superconducting tape where the middle layer is a brittle superconductor and the surrounding layers are isotropic and ductile. An approximate dispersion relation correct to O(h) governing the guided waves is obtained by expanding the field inside the thin middle layer in powers of the small thickness h of the layer. Numerical examples are given for two specific systems with superconducting middle layers. Some characteristic features, particularly at low frequencies, are investigated. Comparison between the exact and approximate dispersion relations are made to show that the approximation works well in the frequency interval of interest. The characteristic features may be useful for ultrasonic measurements of the anisotropic elastic constants of the thin layer.

On the modeling of guided waves in plates with thin superconducting layers

Abstract: Investigation of in-situ mechanical behavior and properties of thin superconducting layers and tapes has been very limited However, it is well known that the properties are highly dependent on the manufacturing processes, external and internal stress fields, interface properties and porosity, to name a few In order to accurately model these different effects, it is necesary to understand the basic problem of guided wave propagation in three-layered tapes The tapes may consist of either an elastic isotropic metallic core coated with thin anisotropic oxide layers or a thin oxide layer sandwiched between two metallic layers In this paper, a model study of the two three-layered systems is presented Exact and approximate dispersion relations for guided waves in the plates are calculated The approximate dispersion relations are obtained by replacing the thin oxide layers by effective boundary conditions Since the metallic layers are isotropic, the approximate dispersion relations can be obtained analytic

Ultrasonic Imaging and Theoretical Prediction of Orthotropic Plate Stiffness in all Planar Directions

Abstract: Exact and approximate theoretical analysis of the wavelengths of plate wave mode propagation in all planar directions for the dispersive antisymmetric Lamb wave mode are compared with measurements from a laser ultrasonic imaging approach that records the out of plane ultrasonic motion over a large area in a single frame without scanning. Good agreement is demonstrated, based on independent determination of the elastic constants, for two different types of paper.