M. Darmon

Bio: M. Darmon is an academic researcher. The author has contributed to research in topics: Ultrasonic testing. The author has an hindex of 3, co-authored 3 publications receiving 21 citations.

Results of the 2009 ut modeling benchmark obtained with civa: responses of notches, side‐drilled holes and flat‐bottom holes of various sizes

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.

Results of the 2005 UT Modelling Benchmark Obtained with the CIVA Software Developed at the CEA

Abstract: The CIVA software developed at the French Atomic Energy Commission for processing and simulating NDT data includes tools for modelling the whole ultrasonic inspection of a component in which virtual defects are positioned. In this paper, Kirchhoff’s approximation and reciprocity principle were applied to predict the reception by the transducer of waves scattered by the defect. Results given and discussed are those obtained for the various problems of the 2005 UT benchmark modelling session. These results concern the echographic responses of side drilled holes and cracks using immersed inspection techniques.

Results of the 2010 ut modeling benchmark obtained with civa: responses of backwall and surface breaking notches

Abstract: This communication presents the results obtained on the configurations proposed in the 2010 UT modelling benchmark with the ultrasonic models implemented in the CIVA software. Experiments have been performed upon a planar block containing vertical planar backwall and surface breaking notches of different heights and extensions. The aim is to study the relative amplitudes of the notches echoes obtained after one bound on the backwall or after two bounds, on the backwall and then on the surface of the block. Side drilled holes and flat bottom holes were also present in the block for calibration. Two immersion probes of 5 MHz central frequency, for two different apertures, were used. The echoes are simulated by applying an integral formulation for the field radiated by the probe (the pencil‐model) and a scattering model based on the Kirchhoff approximation. Comparison between simulated and experimental results are presented and discussed.

An overview of ultrasonic beam propagation and flaw scattering models in the civa software

Abstract: This paper aims at presenting an overview of the current capabilities of the ultrasonic models of the CIVA software platform (for ultrasonics, eddy current and radiography techniques), developed by CEA‐LIST and partners. Those models are based on semi‐analytical approaches and numerical integration (integral methods upon the surface of probe or the flaw) in order to address fairly complex configurations while keeping reduced computation times. Such skills are obviously reached within the range of validity of the semi‐analytical models, which have to be carefully studied. In this context, benchmarks organized by the World Federation of NDE Centers (WFNDEC) from 2004 have largely contributed, thanks to experimental data and comparison with other codes of the community, to the validation of simulation codes. Those benchmarks were mostly dealing with canonical problems (in terms of probes, component geometry and flaw shapes). This paper aims at summing up the various problems addressed in the benchmarks and their contribution to the extension of UT models in CIVA.

Recent advances in semi-analytical scattering models for NDT simulation

Abstract: For several years, CEA-LIST and partners have been developing ultrasonic simulation tools with the aim of modelling non-destructive evaluation. The existing ultrasonic modules allow us to simulate fully real ultrasonic inspection scenarios in a range of applications which requires the computation of the propagated beam, as well as its interaction with flaws. To fulfil requirements of an intensive use (for parametric studies), the choice has been made to adopt mainly analytical approximate or exact methods to model the scattering of ultrasound by flaws. The applied analytical theories (Kirchhoff and Born approximations, GTD, SOV...) were already described in previous GDR communication. Over the years, this "semi-analytical" approach has been enriched by adaptations and improvements of the existing models or by new models, in order to extend the applicability of the simulation tools. This paper is devoted to the following recent advances performed in the framework of this approach: The SOV method based on the exact analytical model for the scattering from a cylindrical cavity has been extended in 3D to account for field variations along the cylinder. This new 3D model leads to an improvement in simulation of small side-drilled holes. Concerning the geometrical theories of diffraction (GTD), subroutines for calculation of the 2D wedge diffraction coefficients (for bulk or Rayleigh incident waves) have been developed by the Waves and Fields Group and uniform corrections (UAT and UTD) are under investigation. Modelling of the contribution of the head wave and creeping wave to the echoes arising from a wedge. Numerous experimental validations of the developed models are provided. New possibilities offered by these new developments are emphasized.

Acoustic Scattering Models from Rough Surfaces: A Brief Review and Recent Advances

Abstract: This paper proposes a brief review of acoustic wave scattering models from rough surfaces. This review is intended to provide an up-to-date survey of the analytical approximate or semi-analytical methods that are encountered in acoustic scattering from random rough surfaces. Thus, this review focuses only on the scattering of acoustic waves and does not deal with the transmission through a rough interface of waves within a solid material. The main used approximations are classified here into two types: the two historical approximations (Kirchhoff approximation and the perturbation theory) and some sound propagation models more suitable for grazing observation angles on rough surfaces, such as the small slope approximation, the integral equation method and the parabolic equation. The use of the existing approximations in the scientific literature and their validity are highlighted. Rough surfaces with Gaussian height distribution are usually considered in the models hypotheses. Rather few comparisons between models and measurements have been found in the literature. Some new criteria have been recently determined for the validity of the Kirchhoff approximation, which is one of the most used models, owing to its implementation simplicity.