S03: Fracto-Emissions in Structural and Seismic Monitoring

Description

The reliability assessment of damaging structures is a complex problem that can be solved only by the use of innovative technologies. Among the most innovative, the most suitable for interpreting damage evolution is that of Acoustic Emission (AE). It is a nondestructive assessment technique based on the spontaneous emission of ultrasonic pressure waves from evolving cracks. Having identified the cracked portion of the structure, it is possible to evaluate its stability and durability from the damage evolution, which may either gradually come to an arrest or propagate at an increasing rate. If the position of the cracks is not known, it can be determined by making use of a multiplicity of sensors and by triangulation.

More generally, fracto-emission signals (Acoustic Emission AE, Electromagnetic Emission EME, and Neutron Emission NE) are triggered by mechanical instabilities at the different scales: AE from macro-cracks, EME from meso-cracks, and NE from micro-cracks. Also the frequency spectrum is extremely wide: from one Hz, typical for seismic events, to TeraHz, typical for nano-scale instabilities (fracture or cavitation).

Fracto-emissions can be used as a promising tool for environmental protection against seismicity. The experimental observations suggest that the “earthquake preparation zone” would depend not only on the magnitude, but also on the crack size development over the Earth’s crust: small cracks form, propagate, and coalesce to form larger ones. Approaching the earthquake occurrence, this area would shrink until coinciding with the quake epicentre. AE regularly anticipates the earthquake by about one day, EME by 3-4 days, and NE by approximately one week.

Organizers

Alberto Carpinteri (email: alberto.carpinteri@polito.it)

Giuseppe Lacidogna

Oscar Borla

Contact

Alberto Carpinteri (email: alberto.carpinteri@polito.it)