Research on CpDAS ultrasonic imaging method for concrete structure defects

Concrete is extensively utilized in infrastructure construction owing to its durability, structural stability, and moldability. However, concrete structures are prone to internal concealed damage during long-term service. Failure to promptly identify such damage may result in catastrophic safety incidents. Therefore, accurate ultrasonic detection of internal defects in concrete structures is critical for ensuring the structural safety of major infrastructure projects. However, existing ultrasonic imaging methods for concrete defect detection remain challenged by signal attenuation and distortion due to the material's inherent heterogeneity and high acoustic-wave attenuation. To address these challenges, this study proposes a composite p-th root delay-and-sum (CpDAS) method that employs p-th root compression of raw echo signals followed by mean-standard deviation weighted processing in the compressed domain. This approach effectively enhances defect signals while suppressing background noise and sidelobe artifacts, ultimately improving ultrasonic imaging quality in concrete structures. Experimental and simulation results confirm the superior performance of CpDAS over conventional DAS for concrete defect detection, delivering significant improvements in key metrics. For single-hole defects, CR, CNR and pSNR showed improvements of 30.80 dB, 18.68 dB and 26.96 dB respectively, while double-hole defects demonstrated corresponding improvements of 26.50 dB, 14.23 dB and 24.80 dB.