Vertical cracks characterization and resolution from lock-in vibrothermography

Abstract

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.

Crack-Depth Prediction in Steel Based on Cooling Rate

“…The most extended modality of thermography used to evaluate materials is the one denominated as active thermography, which is based on the study of the thermal reaction of the material when external signal stimulation is applied. The signal can be applied in different ways, such as heat pulses [15], one-frequency modulated signal, also known as lock-in method [16], mechanical vibrations [17], ultrasounds [18], and microwaves [19]. In this paper, authors apply a new approach to establish a protocol for the prediction of crack depth from cooling rate data.…”