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Focusing a Flexible Ultrasonic Array Transducer Using a Time Reversal Technique for Discontinuities within Complex Geometries

Test components with complex boundaries are frequently encountered in real ultrasonic testing situations. Use of rigid array transducers can lead to beam defocusing and reduction of discontinuity image quality due to the mismatch between the planar array and the changing surface. When a flexible array is used to fit the complex surface profile, the locations of array elements should be known to compute the delay time necessary for adaptive beam focusing. An alternative technique is to employ the time reversal focusing technique, which does not require a priori knowledge about the properties and structures of the specimen and the transducer. In this paper, a time reversal technique was applied to simulate beam focusing of flexible arrays and imaging of discontinuity contained in specimens with nonplanar surface geometries. Quantitative comparisons are made for the performance of flat and flexible array techniques in terms of the ability to focus and image five point-like reflectors positioned at regular intervals. The sinusoidal profile array studied here exhibits almost the same image quality as the flat, reference case.

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