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1. Some Observations on Rayleigh Waves and Acoustic Emission in Thick Steel Plates
Published: 12/31/2009
Author: Marvin Arnold Hamstad
Abstract: Rayleigh waves in acoustic emission (AE) applications were examined for nominal 25 mm thick steel plates. Pencil lead breaks (PLBs) were introduced on the top and bottom surfaces as well as on the plate edge. The plate had large transverse dimensions ...

2. Comparison of Wavelet Transform and Choi-Williams Distribution to Determine Group Velocities for Different Acoustic Emission Sensors
Published: 12/31/2008
Author: Marvin Arnold Hamstad
Abstract: Acoustic emission (AE) sources in a plate generate dispersive Lamb waves. In this research, pencil lead breaks (PLBs) were made on an edge of a 3.1 mm thick aluminum alloy plate to generate such AE waves. The PLBs were made near the plate midplane an ...

3. Acoustic Emission Source Location in a Thick Steel Plate Using Lamb Modes
Published: 1/1/2007
Author: Marvin Arnold Hamstad
Abstract: Using a validated finite-element modeling code, buried out-of-plane (two dimensional code (2D)) and in-plane (three dimensional code (3D)) acoustic emission (AE) dipole point sources were operated at different depths below the top surface of a 25.4 m ...

4. Small Diameter Waveguide for Wideband Acoustic Emission
Published: 1/1/2006
Author: Marvin Arnold Hamstad
Abstract: The signals obtained from two wideband conical sensors were compared in the time, frequency and the time/frequency domains. The signals were generated by pencil lead-breaks on the surface (out-of-plane) or close to the midplane of the edge (in-plane) ...

5. Effects of Noise on Lamb-Mode Acoustic-Emission Arrival Times Determined by Wavelet Transform
Published: 12/1/2005
Authors: Marvin Arnold Hamstad, Agnes O'Gallagher
Abstract: Precise AE signal arrival times of the fundamental Lamb modes can be obtained from the arrival time of the peak wavelet transform (WT) magnitude at a particular frequency of interest. Since these arrival times are not determined from a fixed threshol ...

6. Modal-based identification of acoustic emission sources in the presence of electronic noise
Published: 12/1/2004
Authors: Marvin Arnold Hamstad, Agnes O'Gallagher
Abstract: Based on the results of an earlier study, a specific scheme was demonstrated to identify acoustic emission (AE) source types using ratios of Lamb-wave modal amplitudes from two radiation directions in a 4.7 mm thick aluminum plate. The modal amplitud ...

7. Practical Aspects of Acoustic Emission Source Location by a Wavelet Transform
Published: 1/1/2003
Authors: Marvin Arnold Hamstad, K S Downs, Agnes O'Gallagher
Abstract: An algoithmic approach to improve the accuracy of AE source location was demonstrated by using a large database of wideband-acoustic-emission-(AE)-modeled signals and wavelet transform (WT) results. The AE-signal database was created by a three-dime ...

8. Wavelet Transform Signal Processing to Distinguish Different Acoustic Emisson Sources
Published: 1/1/2003
Authors: K S Downs, Marvin Arnold Hamstad, E P Baars
Abstract: A database of wideband acoustic emission (AE) modeled signals were used to continue to examine the use of wavelet transform (WT) results to accomplish identification of AE sources. The AE signals in the database were created by use of a validated thr ...

9. Finite Element and Plate Theory Methods for Modeling Acoustic Emission Waveforms
Published: 10/1/2002
Authors: W H Prosser, Marvin Arnold Hamstad, John M. Gary, Agnes O'Gallagher
Abstract: A comparison was made between two approaches to predict acoustic emission waveforms in thin plates. A normal mode solution method for Mindlin plate theory was used to predict the flexural plate mode response to a point source, step-function load, ...

10. Reflections of AE Waves in Finite Plates: Finite Element Modeling and Experimental Measurements
Published: 10/1/2002
Authors: W H Prosser, Marvin Arnold Hamstad, John M. Gary, Agnes O'Gallagher
Abstract: We investigated the capability of a three-dimentional dynamic finite element method for predicting far-field acoustic emission (AE) signals in thin plates of finite lateral extent, including their reflections from the plate edges. A lead-break (Hsu- ...

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