title: All-optical probing of the nonlinear acoustics of a crack.
abstract: Experiments with an all-optical method for the study of the nonlinear acoustics of cracks in solids are reported. Nonlinear acoustic waves are initiated by the absorption of radiation from a pair of laser beams intensity modulated at two different frequencies. The detection of acoustic waves at mixed frequencies, absent in the frequency spectrum of the heating lasers, by optical interferometry or deflectometry provides unambiguous evidence of the elastic nonlinearity of the crack. The high contrast in crack imaging achieved by remote optical monitoring of the nonlinear acoustic processes is due to the strong dependence of the efficiency of optoacoustic conversion on the state of the crack. The highest acoustic nonlinearity is observed in the transitional state of the crack, which is intermediate between the open and the closed ones.
authors: LAUM, UMR-CNRS 6613, PRES UNAM, Université du Maine, Le Mans, France. sylvain.mezil@univ‐lemans.fr
authors: Sylvain
authors: S
authors: Mezil
authors: Nikolay
authors: N
authors: Chigarev
authors: Vincent
authors: V
authors: Tournat
authors: Vitalyi
authors: V
authors: Gusev