Ultrasonic wave testing is a classic NDT method to detect, locate, and monitor the cracks and fractures in construction materials. In this paper, a new ultrasound data interpretation technique is introduced: The reverse time migration (RTM) is a wave equation-based prestack method used in seismic exploration. Because RTM can utilize all kinds of waves, such as reflection waves, refraction waves, and diffraction waves, it has no dip limits in migration and can create an image of the inside of complicated structures. However, the large data generation and sophisticated velocity field analysis are the bottlenecks for RTM that hinder its wide applications. A hybrid boundary condition (including random boundary and absorption boundary simultaneously) is suggested in this paper to reconstruct the source wave field to address the memory storage issues. A numerical model with S-shaped internal fracture is presented to demonstrate the technique for detection of internal flaws. The results indicate that the accuracy of detecting the embedded flaw within construction material is affected by the sampling space and the range of wave frequency.
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