Time efficient autofocus TFM imaging for ultrasonic inspection of planar and cylindrical components.

Ultrasonic immersion testing is a widely used Non-Destructive Testing (NDT) technique that requires precise knowledge of both the geometry of the inspected component and the probe position to ensure accurate imaging. This paper presents a time-efficient autofocusing through basic geometries with unknown geometric parameters, such as flat or cylindrical structures, applicable to longitudinal-wave ultrasonic inspection at normal (0°) incidence. In the proposed approach, the interface parameters are estimated directly from pulse-echo data using a new regression-based method that employs linear and hyperbolic transformations for flat and cylindrical components, respectively. Once the interface is estimated, the standard Total Focusing Method (TFM) is applied to image the interior of the component. Experimental results validate the capability of the proposed method to accurately reconstruct flat and cylindrical surfaces, facilitating reliable imaging of the components defects, thereby demonstrating its potential for industrial applications.