Research on Total Focusing Method Based on Ultrasonic Annular Phased Array

Zhou, Zhenggan; Beihang University; China

Zhou, Z.; Beihang University; China
Li, S.; Beihang University; China
Li, Y.; Beihang University; China
Li, W.; Beihang University; China

ID: ECNDT-0281-2018
Download: PDF
Session: PAUT & TFM 2
Room: G2
Date: 2018-06-11
Time: 16:20 - 16:40

The total focusing method (TFM) is an effective post-processing imaging technique mainly applied to linear phased arrays and planar phased arrays where the transducer can realize the beam transition or beam deflection. To maintain an optimal conventional ultrasonic testing performance, this paper puts forward a new TFM algorithm applied to annular phased arrays. In this method, the data reconstruction zone is no longer the section region in traditional TFM but the linear region along the axis of the transducer. The zone is meshed, and for each point along the line, the focal-laws are calculated for the entire set of elements of the transducer. Annular phased array can generate better penetration depth and lateral resolution with fewer elements which enable to mesh the whole test specimen with higher density and less calculation, to maintain the infinite focusing of the test specimen. Each virtually focused point can be covered by the focal spot with smaller size to increase the imaging resolution. Besides, this algorithm can be adapted to anisotropic materials by taking into account the anisotropy when calculating the focal-laws. This paper presents a comparative analysis between different testing methods. Experimental results show that the total focusing method based on ultrasonic annular phased array improved the recognition ability for small defects in high-thickness isotropic materials and has a broad application prospect in anisotropic inhomogeneous materials.