Showing papers by "Nik Rajic published in 2012"
19 Sep 2012
TL;DR: In this article, an in-situ fibre Bragg grating (FBG) sensing capability for Lamb waves at frequencies of up to 2MHz was demonstrated, which represents an important step toward developing a more robust and versatile approach to Acousto-Ultrasonic SHM.
Abstract: Lamb waves provide arguably the best prospect for achieving a structural health monitoring (SHM) capability with broad diagnostic coverage at sensor densities that are not impractically high. The traditional approach in Lamb wave SHM is to employ a single mode, typically one of the fundamental modes, in a non-dispersive and easily excited regime, which is done largely to simplify the interpretation of the elastic wave dynamics. However, the diagnostic value of an interrogation conducted using only the fundamental modes is limited. In general, higher order modes offer potential for greater sensitivity to structural damage and greater scope for discriminating between different failure mechanisms. This paper reports on experimental work demonstrating an in-situ fibre Bragg grating (FBG) sensing capability for Lamb waves at frequencies of up to 2MHz, an achievement that represents an important step toward developing a more robust and versatile approach to Acousto-Ultrasonic SHM.Copyright © 2012 by Commonwealth of Australia
8 citations
01 Jan 2012
TL;DR: In this paper, the authors investigated the accuracy of numerical finite element simulations of elastic wave scattering from a structural defect in a metallic wing skin component, and proposed several different approximation schemes to produce simulation results with an accuracy comparable to that of a piezoelectrically coupled solution.
Abstract: This paper reports on an investigation into the accuracy of numerical finite element simulations of elastic wave scattering from a structural defect in a metallic wing skin component. The work forms part of a broader research program that seeks to develop a validated predictive modelling capability for optimal design of acousto-ultrasonic systems for health monitoring of structural hot spots. The present investigation examines the efficacy of simplified representations of the acoustic transduction process whereby piezoelectric coupling is replaced by a set of traction forces with appropriate time modulation. The motivation for the work is the prospect of a significant gain in computational efficiency. Several different approximation schemes are considered and assessed on the basis of how closely the resulting simulations match experimental observations of the scattered field. Some of the approximation schemes are shown to produce simulation results with an accuracy comparable to that of a piezoelectrically coupled solution, suggesting that improved computational efficiency can be achieved without compromising simulation accuracy.
3 citations