Wideband Acoustic Emission Displacement Signals as a Function of Source Rise-Time and Plate Thickness

Published

August 1, 1998

Author(s)

Marvin A. Hamstad, John M. Gary, Agnes O'Gallagher

Abstract

Using a dynamic finite element model, we studied the interrelationships between acoustic source rise-time and plate thickness in steel plates. The source was typically a midplane vertical dipole, and the out-of-plane displacement was obtained in the far-field, typically at a distance of 15 times the plate thickness. Results with the finite element approach were first obtained without considering practical experimental factors such as the bandwidth limitations of acoustic emission (AE) sensors. In addition, signal processing was applied to the displacement signals to more accurately simulate typical wideband experimental conditions. Analysis of the results indicates that practical measurement realities (bandwidth of contemporary wideband sensors) have a significant effect on the observed displacement signals when the same AE source (temporal characteristics) operates in plates of different thicknesses. The question of scaling of results with plate thickness was also addressed for typical AE rise-times. It was demonstrated that nearly correct results for thinner plates (with the same source rise-time) could be obtained by simple signal processing of results from a thicker plate. Experimental realities, which currently limit the full characterization of AE sources with fast rise-times, were pointed out. Also, the relationships between the multi-mode group velocity curves and the observed displacements were examined. The perspective taken in the examination of the modeled AE results was that of using the AE data in order to characterize particular AE sources.

Proceedings Title

Proceedings of the 11th International Acoustic Emission Symposium and the 5th Acoustic Emission World Meeting

Volume

9

Issue

Chap. 4

Conference Dates

August 1, 1998

Conference Title

Progress in Acoustic Emission

Pub Type

Conferences

Keywords

acousic emission, displacement waveforms, finite element modeling, Lamb waves

Citation

Hamstad, M. , Gary, J. and O'Gallagher, A. (1998), Wideband Acoustic Emission Displacement Signals as a Function of Source Rise-Time and Plate Thickness, Proceedings of the 11th International Acoustic Emission Symposium and the 5th Acoustic Emission World Meeting (Accessed April 19, 2024)