Journal of Theoretical
and Applied Mechanics

56, 2, pp. 523-547, Warsaw 2018
DOI: 10.15632/jtam-pl.56.2.523

Mechanical response of notched marble beams under bending versus acoustic emissions and electric activity

Stavros K. Kourkoulis, Ermioni D. Pasiou, Ioanna Dakanali, Ilias Stavrakas, Dimos Triantis
An experimental protocol, including the combined application of both innovative and traditional
sensing techniques, is described aiming to explore the mechanical response of marble
and also to check the possibilities of detecting precursor phenomena designating upcoming
catastrophic fracture. The protocol consisted of three-point bending tests with notched prismatic
beams made of Dionysos marble, the material extensively used for restoration of
the Acropolis of Athens monuments. The sensing system improvised included techniques
relying on completely different physical foundations, which permit simultaneous detection
and recording of the Pressure Stimulated Currents, Acoustic Emissions, three dimensional
displacement fields and Notch Mouth Opening Displacements. Analysis of the results revealed
interesting features of the mechanical response of Dionysos marble and indicated,
also, that classical Continuum Fracture Mechanics fails to describe accurately the response
of marble, at least in the presence of notches. In addition, strong correlations between the
Pressure Stimulated Currents, the rate of acoustic hits and the rate of change of the opening
of the pre-existing notch have been enlightened. Moreover, the onset of catastrophic crack
propagation appears following distinguishable changes of the Pressure Stimulated Currents
recorded. Therefore (and taking into account the very small size of the respective sensors
as well as the simple complementary equipment needed), it is concluded that the specific
technique could be considered as a simple and reliable tool for an alternative approach to
the in-situ Structural Health Monitoring of classical stone monuments.
Keywords: marble, monuments, notch mouth opening displacement, three-point bending, pressure stimulated currents, acoustic emissions, 3D-digital image correlation