Adaptive ultrasonic imaging with the total focusing method for inspection of complex components immersed in water

Abstract

In this paper, we propose an ultrasonic adaptive imaging method based on the phased-array technology and the synthetic focusing algorithm Total Focusing Method (TFM). The general principle is to image the surface by applying the TFM algorithm in a semi-infinite water medium. Then, the reconstructed surface is taken into account to make a second TFM image inside the component. In the surface reconstruction step, the TFM algorithm has been optimized to decrease computation time and to limit noise in water. In the second step, the ultrasonic paths through the reconstructed surface are calculated by the Fermat's principle and an iterative algorithm, and the classical TFM is applied to obtain an image inside the component. This paper presents several results of TFM imaging in components of different geometries, and a result obtained with a new technology of probes equipped with a flexible wedge filled with water (manufactured by Imasonic).

Strategies for data acquisition using ultrasonic phased arrays

“…Secondly, in order to measure the FMC data N transmissions are required, which can take too long for some applications. Note, that the technological advances in the last few years have made it possible to perform ultrasonic imaging using the FMC data acquisition method in near ‘real time’, where this means frame rate of tens frames per second [16]. This is close to the fundamental physical limit, which is related to the finite speed of ultrasonic wave propagation and their decay in materials.…”

Extended Non-Stationary Phase-Shift Migration for Ultrasonic Imaging of Irregular Surface Component

“…For irregular surface components, the mainstream method is to use immersion type or specially designed wedge, and then obtain the wave propagation time of all grid pixels according to the ray tracing method, and finally use TFM for imaging. It is well known that although TFM can obtain ultrasonic images of irregular surface components, it costs a lot of computation time [8]- [11]. Other approach is to use flexible array transducers that can be closely attached to the surface, combined with optimization algorithms to obtain the best estimated surface shape, which can also solve the defect detection in complex components [12]- [14].…”

Towards an Alternative to Time of Flight Diffraction Using Instantaneous Phase Coherence Imaging for Characterization of Crack-Like Defects

“…Indeed, such techniques allow almost any type of acquisition scheme to steer, focus, or sub-aperture the ultrasonic beam that is sent to the sample. Particularly, the full matrix capture (FMC) [ 4 , 5 ] data acquisition scheme, and its total focusing post-processing method (TFM) [ 6 , 7 ] have proven to be reliable, and provide easy-to-understand images, while using conventional probing hardware [ 8 , 9 ].…”