Vertical cracks characterization and resolution from lock-in vibrothermography

This work combines lock-in vibrothermography experiments and a stabilized inversion algorithm to characterize vertical cracks. The ability of the method to retrieve square cracks at increasing depths is analyzed by inverting synthetic data with different levels of white noise. Moreover, the minimum distance between square defects in order to be resolved is determined as a function of depth. Inversions of experimental data obtained at low intensity ultrasound excitation in samples containing calibrated defects confirm the predictions of inversions performed with synthetic data.