Ultrasonic imaging of irregularly shaped notches based on elastic reverse time migration

摘要

Ultrasonic techniques have been proved to be useful for detection and characterization of flaws in solid structures. However, it remains challenging to characterize flaws that do not have regular shapes. In this paper, an ultrasonic imaging technique based on elastic reverse time migration (ERTM) is developed for imaging notches with irregular shapes. In this method, the image is generated by cross-correlating the forward propagated wavefield from the source with the time-reversed backward propagated wavefield from the scatterer. Comparing to traditional ultrasonic imaging methods based on the travel time of ultrasonic signals, this method considers full waveforms which contain the information of mode conversions and multiple scattering, and therefore enables the possibility to image flaws with complex shapes. In this paper, the ERTM algorithm is applied to image a branched surface-breaking notch and an embedded stepped notch, showing excellent reconstruction results in both simulations and experiments.