Multi-mode TFM imaging with artifacts filtering using CIVA UT forwards models

Abstract

TFM (Total Focusing Method) is an advanced post-processing imaging algorithm of ultrasonic array data that shows great potential in defect detection and characterization. This technique can be performed using several propagation modes (direct or over skip imaging) and several types of waves (longitudinal or transverse) allowing the imaging of extended defects of complex geometry. However, non physical indications can be observed, leading to misinterpretation. These imaging artifacts are due to the coexistence of several contributions involving several mode of propagation and interactions with possible defects and / or the geometry of the part. In several configurations, a simple time of flight criterion is not sufficient for their identification. This paper presents tools based on the forward CIVA UT models which allow to analyze and to filter these artifacts, without any tuning parameters. The performances achieved are compared to those of conventional TFM on simulated and experimental data.

Plane Wave Imaging for ultrasonic non-destructive testing: Generalization to multimodal imaging

“…The impact point I in on the surface can be found thanks to Eq. (11) and, as the component back-wall depth z r is known and with the notations in Fig. 4, the impact point coordinate x r on the backwall can be written as:…”

“…In this situation, the cylindrical wave emitted by an element, radiating mainly perpendicularly to the transducer plan, is not the most fitted type. In some cases, this is highlighted by the existence of nonphysical indications, also called image artifacts, that may lead to misinterpretations [10,11]. The second drawback is the framerate limit due to the number of transmissions (N) and the storage and processing of the N Â N signals.…”

Plane wave imaging for ultrasonic inspection of irregular structures with high frame rates

“…vertical faces of the notches) with the T T T half-skip mode. The multimodal image is displayed in Fig.7b and we observe that the notches are fully characterized (height and width) without the presence of reconstruction artifacts often encountered in TFM imaging [2]. It should be noted that the the number of transmissions is reduced at each position (5 L waves and 6 T waves) and the acquisition step is large (8 mm).…”

“…In the present communication, the PWI method is generalized to immersion-testing configurations (plane or complex water/solid interface between the probe and the image area) and to different imaging modes (imaging with direct or half-skip wave paths) according to the type of defects (point-like or extended crack-types defects) [2]. The multimodal PWI method is compared with the Synthetic Transmit Aperture (STA) imaging, also known as Total Focusing Method (TFM) in NDE, which is often considered as the reference method in NDE [3].…”

A Model for Multiview Ultrasonic Array Inspection of Small Two-Dimensional Defects

“…This paper focuses on modelling the ultrasonic response of a small two-dimensional scatterer and in particular its maximum TFM intensities across different views. Various modelling techniques are suitable, including finite element method (FEM) and analytical models such as the commercial software CIVA UT [16]. The aim of the current work is to calculate the TFM intensities of a defect with an even higher computational efficiency for small defects, as it is an essential first step to develop new defect detection and characterisation techniques.…”