Monitoring of the Damage in Stone Blocks by Means of Non-Destructive Methods

This paper deals with the damage assessment in stone blocks dismantled from a historic bridge construction. Nonlinear ultrasonic spectroscopy and impact echo methods were used for evaluating the stone block integrity structure. Harmonic analysis of the sample response on well defined ultrasonic excitation was used in the case of nonlinear ultrasonic method application. The amplitude dependent spectral changes of the probing signals were measured in the damaged blocks. Measurement results showed that the analysis of amplitude dependent spectral changes is a promising method for the damage assessment in structures. The Impact-Echo method is a technique for detecting defects in material structure such as stone blocks. It is based on monitoring the propagation of elastic waves from a short-duration mechanical impact. The aim of this paper is to provide an overview of the technique and to discuss the important parameters involved in this type of testing. The impact echo method is used to generate low-frequency stress waves from 500 Hz to 50 kHz that propagate into the structure and are reflected by defects and external surfaces.