Probing of laser-induced crack closure by pulsed laser-generated acoustic waves

C. Ni (1) , Nikolay Chigarev (1) , V. Tournat (1) , N. Delorme (2) , Z. Shen (3) , Vitali Goussev (2)

1 LAUM - Laboratoire d'Acoustique de l'Université du Mans
2 IMMM - Institut des Molécules et Matériaux du Mans
3 NJUST - Nanjing University of Science and Technology

The monitoring and characterization of laser-heated crack by the laser ultrasonics technique are reported. In comparison with existing studies, where the Rayleigh and bulk skimming waves were generated by laser-induced line source, the point source is used here. Crack closure by thermoelastic stresses modifies the propagation paths of the acoustic rays from a point source to a point receiver. Thus, the arrival times of the acoustic waves contain useful information on the state of crack closure induced by a particular level of laser heating. An important dependence of the detected signals on the initial width/state of the crack and a presence of local necks/narrowings in the crack are revealed. It is demonstrated that the mode conversion of the incident skimming longitudinal bulk waves into the transmitted Rayleigh waves is very sensitive to imperfectness of cracks closure. The proposed interpretation of the laser-ultrasonics experimental observations is supported by atomic force microscopy measurements.

Domaines: Acoustique [physics.class-ph]

C. Ni, Nikolay Chigarev, V. Tournat, N. Delorme, Z. Shen, et al.. Probing of laser-induced crack closure by pulsed laser-generated acoustic waves. Journal of Applied Physics, 2013, 113 (1), pp.014906. ⟨10.1063/1.4772644⟩. ⟨hal-02354063⟩