Plane Wave Imaging of Concrete Using Phased Array Ultrasonic Technique - A Numerical Study

A numerical simulation-based study is undertaken in order to assess the performance of plane wave imaging in the concrete medium for damage detection. The random scattering of ultrasonic field by the aggregates in the concrete medium incorporates higher background noise in the reconstructed subsurface images using conventional imaging algorithms. This noise can at times mask the imaged defects either partially or completely and hence reducing the capability of damage detection of subsurface images. Also defects located closer to the top surface fail to appear in the reconstructed images. Plane wave imaging technique proposed in this study, on the other hand is able to significantly reduce the incoherent noise as well as other undesired imaging artefacts. This improves the damage detection capability since the image contrast gets improved significantly. The proposed technique is able to image the cracks located at the shallow depth of the medium and at the same time mapping the aperture facing geometry of the defects present in the simulated concrete medium. The reconstruction of subsurface images using plane wave imaging is done by post-processing the full matrix data and hence does not require the phased arrays which can be practically difficult to use on concrete structures.