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research-article

A Helmholtz Potential Approach to the Analysis of Guided Wave Generation during Acoustic Emission Events

[+] Author and Article Information
Mohammad Faisal Haider

Department of Mechanical Engineering University of South Carolina 300 Main Street, Room A237, Columbia, SC 29208
haiderm@email.sc.edu

Victor Giurgiutiu

Department of Mechanical Engineering University of South Carolina 300 Main Street, Room A222, Columbia, SC 29208
victorg@sc.edu

1Corresponding author.

ASME doi:10.1115/1.4038116 History: Received May 04, 2017; Revised September 28, 2017

Abstract

This article addresses the predictive simulation of acoustic emission (AE) guided waves that appear due to sudden energy release during incremental crack propagation. The Helmholtz decomposition approach is applied to the inhomogeneous elastodynamic Navier-Lame equation for both the displacement field and body forces. For the displacement field, we use the usual decomposition in terms of unknown scalar and vector potentials, and. For the body forces, we hypothesize that they can be also expressed in terms of excitation scalar and vector potentials, and. It is shown that these excitation potentials can be traced to the energy released during an incremental crack propagation. Thus, the inhomogeneous Navier-Lame equation has been transformed into a system of inhomogeneous wave equations in terms of known excitation potentials , and unknown potentials , . The solution is readily obtained through direct and inverse Fourier transforms and application of the residue theorem. A numerical study of the AE guided wave propagation (1D) in a 6 mm thick 304-stainless steel plate is conducted. A Gaussian pulse is used to model the growth of the excitation potentials during the AE event; as a result, the actual excitation potential follows the error function variation in the time domain. The numerical studies show that peak amplitude of A0 is higher than the peak amplitude of S0 signal and the peak amplitude of bulk wave is not significant compared to S0 and A0 peak amplitudes. In addition, the effect of the source depth and propagating distance on guided waves are also investigated.

Copyright (c) 2017 by ASME
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