Ultrasonic reverse time migration for imaging based defects detection for layered structures with complex geometry

Layered structures with complex geometries produce fatigue defects under long-term cyclic loadings. It is difficult to fully image the topography of defects using the current mainstream ultrasound imaging technology. The reverse time migration (RTM), which has extensive application in geophysical exploration, can be used to image complex geological structures. This research introduces RTM in the field of ultrasonic non-destructive testing for layered structures with complex geometries. Through numerical simulation of RTM, it is concluded that defects inside layered structures with complex geometries can be identified clearly and that the location, size, and shape of both defects can be determined accurately. Furthermore, this study discusses the influence of the Laplacian filter, absorption boundary, and cross correlation condition on the RTM. It was concluded that whether a filter is set, different absorption boundaries, and different imaging conditions will all affect the imaging quality of complex structures.