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Condensed Matter Seminar: "Scale-Invariance and Self-Excitation in the Fracture of Porous Materials under Steady Compression Rate"

SpeakerPhD Candidate Jordi Baró, Department of Structure and Constituents of Matter, University of Barcelona
Date Nov 22, 2013
Time 1:00 pm  
Location 190 Engineering Sciences Bldg - corner Goodwin & Springfield 
Sponsor Physics
Contact Jason Maldonado
Phone 217.300.6431
Event type Seminar/Symposium
Views 7056

Acoustic Emission (AE) techniques have long been used as a non-intrusive and non-destructive method to study brittle fracture, as well as other avalanche phenomena.

In our experiments we use piezoelectric transducers(micro-80) to detect ultrasonic (100 kHz-MHz) AE signals produced during the collapsing of different porous materials (Vycor (SiO2), Goethite (FeO(OH) and Alumina (Al2O3) ) subject to different steady uniaxial compression rates. The identification of signal events related to internal microcracks allows us to study the phenomena as a point-process and identify the statistical laws that depicts the dynamics of the underlying avalanche process.

Non-surprisingly, we found profound analogies with seismological laws: from the scale-free distribution of energies, to the production of aftershocks and foreshocks, and the recent Unified Scaling Law (USL) for the distribution of waiting times. The stationarity, rate independence and  scale invariance of these laws in the case of Vycor, could be a trademark of an underlying critical phenomena.

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