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MVDR-Integrated TFM for Defect Detection in Geometrically Shadowed Regions
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DOI:10.1109/JSEN.2026.3692201.png)
Abstract
En 中文
Detecting defects in geometrically shadowed regions remains an unavoidable challenge for ultrasonic array imaging using the total focusing method (TFM). To address this limitation, the MVDR-TFM method is proposed in this work, in which minimum variance distortionless response (MVDR) beamforming is integrated into the TFM framework. By minimizing the output power under a distortionless constraint, interference from strong near-field scatterers is suppressed, and sidelobe leakage is reduced, thereby enhancing defect visibility in shadowed areas. In an L-shaped specimen, slot-type defects under the structural barrier are successfully identified by the proposed method, whereas conventional TFM cannot identify these. In terms of contrast ratio (CR) and contrast-to-noise ratio (CNR), the proposed method achieves an improvement of 40.44% and 80.34% over the conventional method, respectively. For super-resolution imaging of two side-drilled holes of 1 mm diameter with a 1 mm spacing below the Rayleigh limit, the peak-to-valley amplitude difference of the resulting lateral cross-sectional profile is increased by 10.53 dB with the proposed method compared to TFM. These results demonstrate improved defect detectability and resolvability of the MVDR-TFM method, enabling more reliable ultrasonic array inspections.
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