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-Neilsen) source to simulate AE was modeled and used in the experimental measurments. For the thin plate studied, the signals were primarily composed of the lowest order symmetric (So) and antisymmetric (Ao) Lamb modes. Experimental waveforms were detected with an absolutely calibrated, wideband, conical element transducer. The conditions of both lead fractures on the surface of the plate as well as on the edge of the plate were investigated. Surface lead breaks preferentially generate the A0 mode while edge lead breaks generate the So mode. Reflections of developed plate waves from both normal and oblique incidence angles were evaluated. Particularly interesting for the case of the lead break on the plate edge were So waves produced by the interaction of a Rayleigh wave with the plate corner and by a bulk shear wave mode converting at the side edge. The Rayleigh wave, in this case, propagated along the specimen edge. For all cases considered, the experimental measurements were in good agreement with the predictions of lateral plate boundaries.
Citation: Journal of Acoustic Emission
Issue: No. 1-2
Pub Type: Journals
acoustic emission, finite element models, Lamb modes