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Proceedings Paper

Mechanical characterization of natural building stones: observation of the fracture process zone by ESPI
Author(s): Francesco Calvetti; Giuliana Cardani; Alberto Meda
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Paper Abstract

The cultural heritage of many nations consist of a great variety of structures of high intrinsic value, which are often composed of natural building stones (NBS), as granite, limestone, marble and sandstone. The use of accurate inspection devices, such as laser interferometry, allows us to acquire information regarding the mechanical properties and damage (tensile cracks) of NBS, which represents the first step in the restoration process. In this paper, the potential application of an electronic speckle pattern interferometry (ESPI) is shown, with particular attention to the observed displacement field and the crack penetration during laboratory testing. In ESPI, by superimposing a reflected light to a reference digitized image, an interference phenomenon is produced. By comparing two recorded interference patterns (before and after loading), the corresponding deformation can be evaluated. The application of ESPI in several laboratory tests on NBS is presented in this paper. In particular, during bending tests performed on geometrically similar NBS specimens, it was observed that the size and shape of the localized damage zone do not depend on the specimen size. These results allow for an interpretation of the 'size- effect,' which consists of a reduction of nominal strength as the specimen size increases.

Paper Details

Date Published: 9 September 1999
PDF: 8 pages
Proc. SPIE 3823, Laser Metrology and Inspection, (9 September 1999); doi: 10.1117/12.360999
Show Author Affiliations
Francesco Calvetti, Politecnico di Milano (Italy)
Giuliana Cardani, Politecnico di Milano (Italy)
Alberto Meda, Politecnico di Milano (Italy)

Published in SPIE Proceedings Vol. 3823:
Laser Metrology and Inspection
Hans J. Tiziani; Pramod Kumar Rastogi, Editor(s)

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