Study on PCA-SAFT imaging using leaky Rayleigh waves.

• Surface defect visualization is attained using leaky Rayleigh waves. • PCA-SAFT imaging method is proposed to improve resolution and reduce noise. • The SNR and CNR of the PCA-SAFT image are both increased. • The proposed method is verified on both isotropic and anisotropic specimens. Efficient and accurate nondestructive testing of surface or sub-surface flaws is essential for metal components. This study focuses on the high-quality image reconstruction of these flaws. An imaging detection method is introduced which combines the leaky Rayleigh waves testing and the synthetic aperture focusing technique (SAFT) with an immersion pulse-echo scanning. The principal component analysis (PCA) is used to reduce the noise of the leaky Rayleigh waves, and then the imaging is obtained using the SAFT algorithm. The experimental results show that the PCA-SAFT imaging method can reduce structural noise and imaging artifacts comparing with the B-scan imaging method. The lateral resolution of defects is improved and the mean error of defects sizing can be reduced by 48.81%. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the ultrasonic image are increased by 6.95 dB and 4.20 dB respectively. The proposed method can be a new choice for effective evaluating the surface quality of key components. [ABSTRACT FROM AUTHOR]