Fracturing behavior of brittle solids containing 3D internal crack of different depths under ultrasonic fracturing

Ultrasonic fracturing (UF) can be used to form crack networks for oil or gas in the mining industry and hard rock excavation. In this paper, the three-dimensional internal laser-engraved crack method (3DILC) is introduced to make penny-shaped internal crack within the samples without any damage to the surfaces. Physical experiments were performed on the transparent samples with internal cracks at different depths. The macro-and micro-fracture fractography characteristics were focused on and analyzed in details. Based on fractography, the mechanisms of the UF were revealed. The propagation paths of cracks of different depths were simulated based on the Paris fatigue model and compared with experimental results. The results show that the 3D-ILC method is a powerful tool for the experimental research on the internal crack propagation in the UF. Under the action of ultrasonic field, fractography shows the characteristics of beach marks, lance-like pattern, rime-like pattern and glass powder. It can be judged that the mechanisms of UF include high cycle fatigue fracture, shear fracture, and friction. The results of the numerical simulation using the Paris fatigue model are consistent with the experimental results. (c) 2022 Published by Elsevier B.V. on behalf of China University of Mining & Technology. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).