Author
Steve Mahaut
Bio: Steve Mahaut is an academic researcher from French Alternative Energies and Atomic Energy Commission. The author has contributed to research in topics: Ultrasonic testing & Nondestructive testing. The author has an hindex of 7, co-authored 17 publications receiving 208 citations.
Papers
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TL;DR: Experimental and simulation results showed that the defect detection and characterization performances were greatly enhanced using phased array techniques, whereas phased array inspections enabled to detect and locate all of these defects.
63 citations
18 Feb 2014
TL;DR: In this paper, the authors present tools based on the forward CIVA UT models which allow to analyze and to filter these artifacts, without any tuning parameters, on simulated and experimental data.
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.
38 citations
TL;DR: Experimental results show that specific reconstruction techniques have been investigated to enhance the signal-to-noise ratio as well as spatial resolution, based on beam-forming summation and multi-angle inspections, allow to reduce the speckle noise and to optimise the beam resolution.
26 citations
TL;DR: Experimental results show the ability of this new concept of phased array transducer to detect and characterize defects under irregular profiles, using longitudinal or shear waves in a fully mastered beam.
19 citations
05 Mar 2010
TL;DR: In this paper, the relative amplitudes and the shapes of specular and corner echoes for different flaws in 2D and 3D configurations were studied using the CIVA software platform.
Abstract: This communication presents the results obtained on the configurations proposed in the 2009 UT modelling benchmark with the ultrasonic models implemented in the CIVA software platform. The aim, this year, is to study the relative amplitudes and the shapes of specular and corner echoes for different flaws in “2D” and “3D” configurations. Experiments have been performed with contact probes (single element or phased array) radiating transversal or longitudinal waves at 45° incidence angle on planar mock‐ups containing flat‐bottom hole, side‐drilled holes and backwall breaking notches of different heights and widths. The echoes are simulated by applying an integral formulation for the field radiated by the probe (the pencil‐model) and different scattering models depending on the kind of defects. Comparison between simulated and experimental results are presented and discussed.
11 citations
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TL;DR: The use of ultrasonic arrays for non-destructive evaluation has been extensively studied in the literature as mentioned in this paper, where the main advantages of arrays are their increased flexibility over traditional single element transducers, and their ability to produce immediate images of the test structure.
Abstract: An ultrasonic array is a single transducer that contains a number of individually connected elements. Recent years have seen a dramatic increase in the use of ultrasonic arrays for non-destructive evaluation. Arrays offer great potential to increase inspection quality and reduce inspection time. Their main advantages are their increased flexibility over traditional single element transducer methods, meaning that one array can be used to perform a number of different inspections, and their ability to produce immediate images of the test structure. These advantages have led to the rapid uptake of arrays by the engineering industry. These industrial applications are underpinned by a wide range of published research which describes new piezoelectric materials, array geometries, modelling methods and inspection modalities. The aim of this paper is to bring together the most relevant published work on arrays for non-destructive evaluation applications, comment on the state-of the art and discuss future directions. There is also a significant body of published literature referring to use of arrays in the medical and sonar fields and the most relevant papers from these related areas are also reviewed. However, although there is much common ground, the use of arrays in non-destructive evaluation offers some distinctly different challenges to these other disciplines.
818 citations
TL;DR: In this article, a general imaging methodology, termed multi-mode total focusing method, is proposed in which any combination of modes and reflections can be used to produce an image of the test structure.
Abstract: Ultrasonic arrays allow a given scatterer to be illuminated from a wide range of angles and hence are capable of extracting significant information about the scatterer. In this paper a general imaging methodology, termed multi-mode total focusing method, is proposed in which any combination of modes and reflections can be used to produce an image of the test structure. Like the total focusing method, this approach is implemented by post-processing the full matrix of array data to achieve a synthetic focus at every pixel in the image. A hybrid model is used to predict the array data and demonstrate the performance of the multi-mode imaging concept. This hybrid model combines far field scattering coefficient matrices with a ray-based wave propagation model. This allows the inclusion of longitudinal waves, shear waves and wave mode conversions. It is shown that, with prior knowledge of likely scatterer location and orientation, the mode combination and array location can be optimised to maximise the performance of array inspections. A practically relevant weld inspection application is then described and its optimisation is discussed.
208 citations
TL;DR: It is demonstrated how measurement of the scattering coefficient matrix of a cracklike defect can be used to obtain its size, shape, and orientation.
Abstract: Ultrasonic nondestructive evaluation is used for detection, characterization, and sizing of defects. The accurate sizing of defects that are of similar or less size than the ultrasonic wavelength is of particular importance in assessing structural integrity. In this paper, we demonstrate how measurement of the scattering coefficient matrix of a cracklike defect can be used to obtain its size, shape, and orientation. The scattering coefficient matrix describes the far field amplitude of scattered signals from a scatterer as a function of incident and scattering angles. A finite element (FE) modeling procedure is described that predicts the scattering coefficient matrix of various cracklike defects. Experimental results are presented using a commercial 64-element, 5 MHz array on 2 aluminum test samples that contain several machined slots and through thickness circular holes. To minimize the interference from the reflections of neighboring defects, a subarray approach is used to focus ultrasound on each target defect in turn and extract its scattering coefficient matrices. A circular hole and a fine slot can be clearly distinguished by their different scattering coefficient matrices over a specific range of incident angles and scattering angles. The orientation angles of slots directly below the array are deduced from the measured scattering coefficient matrix to an accuracy of a few degrees, and their lengths are determined with an error of 10%.
128 citations
TL;DR: A number of array post-processing methods developed for scanning applications in non-destructive evaluation are described, one of which is to capture and process the full matrix of all transmit-receive time-domain signals from the array.
117 citations