Accéder directement au contenu Accéder directement à la navigation
Chapitre d'ouvrage

Nonlinear Frequency-Mixing Photoacoustic Characterisation of a Crack

Abstract : A one and two dimensional imaging of a crack by a novel nonlinear frequency-mixing photoacoustic method is presented. Acoustic waves are initiated by a pair of laser beams intensity-modulated at two different frequencies. The first laser beam, intensity modulated at a low frequency fL , generates a thermoelastic wave which modulates the local crack rigidity up to complete closing/opening of the crack, corresponding to crack breathing. The second laser beam, intensity modulated at much higher frequency fH , generates an acoustic wave incident on the breathing crack. The detection of acoustic waves at mixed frequencies fH±nfL ( n=1,2,… ), absent in the excitation frequency spectrum, provides detection of the crack, which can be achieved all-optically. The theory attributes the generation of the frequency-mixed spectral components to the modulation of the acoustic waves reflected/transmitted by the time-varying nonlinear rigidity of the crack. The crack rigidity is modified due to stationary and oscillating components from the laser-induced thermoelastic stresses. The amplitudes of the spectral sidelobes are non-monotonous functions of the increasing thermoelastic loading. Fitting such experimental evolutions with theoretical ones leads to estimating various local parameters of the crack, including its width and rigidity.
Liste complète des métadonnées
Contributeur : Vitali Goussev Connectez-vous pour contacter le contributeur
Soumis le : mercredi 8 avril 2020 - 13:34:51
Dernière modification le : lundi 21 mars 2022 - 15:10:03




Sylvain Mezil, Nikolay Chigarev, Vincent Tournat, Vitali Goussev. Nonlinear Frequency-Mixing Photoacoustic Characterisation of a Crack. Measurement of Nonlinear Ultrasonic Characteristics, pp.235-281, 2020, ⟨10.1007/978-981-15-1461-6_6⟩. ⟨hal-02536848⟩



Consultations de la notice