Acoustic Emissions versus Pressure Stimulated Currents during bending of restored marble epistyles: Preliminary results

Abstract

The efficiency of two modern sensing techniques, namely the "Acoustic Emissions" and the "Pressure Stimulated Currents" ones, when they are used as Continuous Structural Health Monitoring tools, is assessed experimentally. The protocol includes multi-point bending of an accurate copy of a fractured marble epistyle of the Parthenon's Temple on the Acropolis of Athens, under a scale of 1:3. The integrity of the epistyle is restored with three pairs of bolted titanium bars, according to the pioneering technique developed by the scientists of the "Committee for the Conservation of the Acropolis Monuments". The data provided by the above techniques are considered in juxtaposition to each other and also in comparison to data provided by the "Digital Image Correlation" technique. It is concluded that, at least from a qualitative point of view, the data of all three techniques are in good mutual agreement. Combined exploitation of the various sets of experimental data enlightens interesting aspects concerning the succession of failure mechanisms activated during the loading procedure, revealing the critical role of the internal interfaces characterizing the restored epistyle. Moreover it is definitely indicated that both the "Acoustic Emissions" and the "Pressure Stimulated Currents" techniques provide clear signs of upcoming failure well before macroscopically visible damages are detected at the external surface of the specimen.

Modelling acoustic and electric signals emitted during structural tests in terms of log‐periodic power‐law models

“…Both electric and acoustic signals recorded are indicative of the damage process taking place within the volume of the two marble blocks. Proper elaboration of these signals provides a rough estimation of the energy released during the deformation process through the micro‐crack formation and coalescence 23,33 . By calculating the square values of the amplitude of these signals and adding each consecutive value up to the time instant of the final rupture, one obtains a measure of the cumulative energy released during (and due to) the damage process or equivalently an estimation of the internal damage level.…”

Double initial and caustic curves in diametrically compressed transparent discs - Application to the contact length

“…Finally, it should be noticed that the general formulae including double and single caustics obviously refer also to opaque materials as particular cases of the transparent ones, provided their faces are properly polished. The latter could be of crucial importance, especially for specimens made of marble [50] and natural building stones [51], the mechanical response of which is usually studied using the Brazilian-disc test (due to insuperable difficulties encountered in the implementation of direct uniaxial tension tests, caused due to the unique nature of such materials [52][53][54][55][56]) employing either traditional or innovative experimental techniques [57][58][59][60].…”

Assessing structural integrity of non-homogeneous systems by means of Acoustic Emissions and Non-Extensive Statistical Mechanics

“…The displacements developed during loading were monitored using a 3D-Digital Image Correlation (DIC) system (LIMESS, Messtechnik & Software GmbH, Germany). (c) The epistyle after it was tested [26].…”

“…Close views of failed specimens are shown in the embedded photos, highlighting the differences in the deformation mechanisms. (b) For a specimen with a partially covered "I"-shaped connector ("I"-PC) [26].…”