Plane wave imaging has widespread applications in non-destructive testing due to its fast data acquisition speed and simple system architecture. However, traditional plane wave imaging employs an unfocused transmission scheme. This results in dispersed acoustic energy distribution, low imaging resolution, and poor image quality. Although coherent plane wave compounding (CPWC) improves imaging performance through multi-angle coherent summation, it still has shortcomings in image resolution, contrast, and artifact suppression when detecting defects far from the acoustic axis center. To break through these limitations, this paper proposes a coherent plane wave compounding with delay multiplication and sum (CPWC-DMAS) method in which multi-angle plane wave is combined with DMAS beamforming technology to enhance imaging quality and resolution capability. First, coherent summation of multi-angle plane wave signals is performed to achieve comprehensive angular information fusion, ensuring effective coverage of the detection region. Subsequently, the DMAS method is used to perform cross-multiplication and summation of signals acquired from all angles by different array elements, utilizing the spatial coherence between received signals from different array elements to effectively enhance the target echo signals, while suppressing incoherent noise and reducing artifacts. Finally, to validate the correctness and effectiveness of the proposed method, experimental verification is conducted on defects embedded in steel rail and wheel components. The results indicate that compared with the total focusing method and CPWC algorithms, the proposed CPWC-DMAS algorithm achieves significant improvements of 51.18% and 50% in array performance index, 50.8% and 46.52% in contrast ratio, and 25.14% and 21.56% in signal-to-noise ratio, respectively. In summary, the proposed CPWC-DMAS algorithm demonstrates significant advantages over traditional methods in resolution enhancement, contrast improvement, and artifact suppression, achieving high-quality imaging for multi-angle coherent plane wave compounding. This method provides a novel approach for detecting defects both near and away from the center of acoustic axis, offering new insights into defect detection in complex structures with broad engineering applications.
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