An Ultrasound Based Technique for the Detection and Classification of Flaws inside Large sizes Marble or Stone Structural elements
Mauro Bramanti , CNR-IEI, Italy
Edoardo Bozzi , CNR-IEI, Italy

Short Paper: Short Paper 1: Restoration and Preservation

Non-destructive diagnostic techniques (NDT) of materials and devices have been studied sine many years. The procedures are based on various physical phenomena, but most of them involve the use of ultrasonic radiation (US). Such procedures allow faulty parts to be detected, located and mapped. The exploring signal frequency generally ranges from tens of KHz to tens of MHz. US techniques are not so currently used for the diagnostic of devices made up of natural stone as they are used for other types of materials. This is quite surprising since the presence of faults, such as fissures and cracks, inside structural elements of stone or marble, is a real risk factor, and most current NDT techniques are quite suitable for these types of materials as well. Here we propose a procedure which uses ultrasound bursts within 50 KHz - 500 KHz frequency range for NDT of marble structural elements with the sizes up to one or two meters The procedure is based on propagation attenuation measurements and allows the detection of internal flaws and also the estimation of the type of flaw itself by comparing measurements at different frequencies. An experimental set-up was implemented for in-field measurements. It is based on commercially available components and a dedicated watery matching system. The experimental results obtained on isolated marble blocks, where an intrusive inspection was allowed, confirmed the validity of the proposed method.

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