Abstract

Nonlinear Properties of Damaged Objects: Application to Crack Detection

A.Moussatov, B.Castagnede (Laboratoire d'Acoustique (UMR CNRS 6613), Universite du Maine, Le Mans, France)

e-mail: alexei.moussatov@univ-lemans.fr

Nonlinear properties have been experimentally evaluated for a number of thick glass plates being damaged by a thermal shock. A direct correlation between the degree of damage and the nonlinear parameter value has been demonstrated (using ratio between second and fundamental harmonics amplitudes). More damage leads to higher nonlinearity. Nonlinearity of strongly damaged plates increased by the factor 300 compared to the intact ones. High nonlinearity in cracked samples has been confirmed by a strong manifestation of frequency-up and frequency-down conversion phenomena. Conversion spectrograms have been analyzed and discussed. For the first time, in cracked solid material, a parametric emitting antenna has been successfully implemented. The non classical anomalous nonlinearity of damaged materials can be effectively used for detection of structural defects, however the nature of this phenomenon still needs understanding.

Section : 3