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Tomographic Imaging of Structural Flaws with New Adaptive Weights on Array



The ability to image a structural flaw in 3D allows to make informed decisions on followup maintenance actions. Flaw imaging can be achieved through the use of tomographic image reconstruction algorithms applied to transient mechanical or thermal waves. Tomographic ultrasonic imaging, for example, is a well-known technique in the engineering NDE/SHM field as well as the medical diagnostic field. In order to improve the contrast and resolution performance of tomographic imaging systems, apodization weights are often applied to the transducer array. One such example of weighing is the well known minimum variance distorsionless (MVD) technique that applies adaptive weights to the array based on the imaging focus point. In this paper we present new adapting weighing techniques, based on the structure of the propagating ultrasonic wave mode (whether longitudinal or shear) and based on the geometrical attenuation behavior of the propagating wave. Such weighting “forces” the array to focus to a specific point of interest within the imaging volume. Imaging results from simulations will be presented and the performance of the proposed weighting technique compared to existing tomographic imaging will be identified.

doi: 10.12783/SHM2015/328

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