Experimental Characterization of PCI Sensitivity for Industrial Ultrasonic Testing Applications

Phase Coherence Imaging (PCI) is a recent evolution of the Total Focusing Method (TFM) in ultrasonic Non-Destructive Testing (NDT). Unlike TFM, PCI relies exclusively on phase information and produces normalized coherence factors instead of amplitude values. As a non-amplitude technique, PCI avoids gain calibration and offers advantages for detecting specific defects. While TFM has been extensively studied and widely adopted in industrial practice, the benefits and limitations of PCI remain less well established. This article presents a set of experimental studies aimed at evaluating PCI’s performance across different reflector types and depths, with comparisons to TFM under identical Full Matrix Capture (FMC) acquisition conditions. Results highlight three main findings: (i) PCI provides more stable indication patterns with reduced influence from wedge/specimen interface echoes, (ii) sensitivity distributions differ significantly between PCI and TFM, particularly for tip diffractions and side-drilled holes, and (iii) statistical analyses reveal that coherence factor variations are reflector- and depth-dependent, in contrast to the more predictable Gaussian-like sensitivity curves observed in TFM. These findings contribute new quantitative insights into PCI behaviour and indicate that future development of numerical modelling tools will be necessary to fully characterize its sensitivity and to guide its industrial application.