Ultrasonic phased array phase shift migration imaging of irregular surface components using attenuation compensation and anti-aliasing technique

Abstract

Extended non-stationary phase shift migration (ENPSM) is a promising imaging algorithm for ultrasonic phased array testing of components with irregular surfaces. In this paper, ENPSM is developed further by combining attenuation compensation (AC) with an anti-aliasing (AA) technique, in an approach called AC-AA-ENPSM, to address the negative effects of attenuation during ultrasonic wave propagation in metals and of jagged medium interface determined by traditional rectangular window. The attenuation term in AC-AA-ENPSM is measured by immersion testing with referenced samples. An anti-aliasing technique is used to smooth the spatial velocity distribution based on the weights of different velocities on a pixel grid. Experiments are performed on objects with irregular surfaces, varying attenuation characteristics and side-drilled hole (SDH) defects. A comparison of the results shows that the proposed AC-AA-ENPSM algorithm has the advantage of a higher signal-to-noise ratio (SNR) than traditional ENPSM. Moreover, the proposed algorithm has a computational efficiency at least 40 times higher than the total Focusing Method (TFM) algorithm, and the SNR difference of them is less than 2 dB.