Développements d'outils de modélisation pour la propagation ultrasonore dans les soudures bimétalliques

This study fits into the field of ultrasonic non-destructive evaluation. It consists in the developmentof a dynamic ray tracing model to simulate the ultrasonic propagation in bimetallicwelds.The approach has been organised in three steps. First of all, an image processing techniquehas been developed and applied on the macrographs of the weld in order to obtain a smoothcartography of the cristallographic orientation. These images are used as input data for a dynamicray tracing model adapted to the study of anisotropic and inhomogeneous media such as bimetallicwelds. Based on a kinematic and a dynamic ray tracing model, usually used in geophysics, itallows the evaluation of ray trajectories between a source point and an observation point, andthe computation of the ultrasonic amplitude through the geometrical spreading of an elementaryray tube. This model has been validated in 2D by comparison of the results with a hybrid semianalytical/finite elements code, then in 3D thanks to experimental results made on the mock-upsof the studied bimetallic welds.Cette étude s’inscrit dans le domaine du contrôle non destructif par ultrasons. Elle consiste àdévelopper un modèle rayons capable de simuler la propagation ultrasonore dans des souduresbimétalliques.La démarche s’est organisée en trois temps. Tout d’abord, un travail d’obtention de cartographieslissées de l’orientation cristallographique au sein de la soudure a été réalisé. Pour cela,un traitement d’images a été mis en place et appliqué aux macrographies de soudures de typeset d’organisations internes différents. Ces cartographies sont utilisées comme données d’entréed’un modèle rayons adapté à l’étude de milieux anisotropes et inhomogènes tels que les souduresbimétalliques. Basé sur le tracé cinématique et dynamique de rayons, habituellement utilisé engéophysique, ce modèle permet d’évaluer le trajet géométrique des rayons d’un point source àun point d’observation et de quantifier l’amplitude du champ ultrasonore par l’intermédiaire ducalcul de la divergence géométrique de tubes élémentaires de rayons. Ce modèle de propagationultrasonore a été validé en 2D par comparaison avec un modèle hybride semi-analytique/élémentsfinis, puis en 3D à l’aide d’expériences réalisées sur les maquettes des soudures étudiées dans cestravaux

Développement de la méthode des rayons paraxiaux pour la simulation de l’inspection ultrasonore des soudures

National audienceL'interprétation d'inspections ultrasonores de soudures austénitiques ou bimétalliques peut s'avérer délicate du fait de l'anisotropie et de l'inhomogénéité caractéristiques de ces milieux. Des déviations et/ou divisions du faisceau ultrasonore peuvent se produire lors de sa propagation. Le modèle développé dans la plateforme CIVA permet de traiter le cas de milieux anisotropes homogènes par morceaux. Les travaux de thèse présentés dans ce papier visent à étendre le modèle à l'étude de milieux inhomogènes. Il est alors possible de simuler la propagation des ultrasons dans des soudures décrites à l'aide d'une représentation continûment variable de l'orientation cristalline des grains. Le formalisme consiste à résoudre les équations eikonale et de transport. Les trajectoires des rayons dans les milieux considérés sont d'abord obtenues via la résolution d'un système linéaire d'équations différentielles du premier ordre. Ensuite, le modèle de tracé dynamique de rayons, ou tracé de rayon paraxial, consiste à résoudre un second système différentiel le long d'un rayon de référence. Il permet de déterminer le facteur de divergence et l'amplitude le long de ce rayon ainsi qu'à son voisinage. Des résultats de simulation sont présentés et comparés à des résultats obtenus avec une méthode éléments finis ainsi qu'à des résultats expérimentaux

Application of a 3D ray tracing model to the study of ultrasonic wave propagation in Dissimilar Metal Welds

International audienceThe primary circuit of Nuclear Power Plants (NPP) is inspected using Ultrasonic NonDestructiveTesting (NDT) techniques in order to maintain the integrity of its structure and detect eventual defects such as Stress Corrosion Cracking (SCC). Nevertheless in some components as Dissimilar Metal Welds (DMW), the interpretation of inspection results is d ifficult due to the appearance of beam disturbances as well as splitting and skewing. Those physical phenomena, occurring due to the anisotropic and inhomogeneous properties of the media, affect the detection and the characterization of possible discontinu ities located inside or in the vicinity of the welds. In this context, numerical simulation tools are really useful to understand these disruptions and optimize the ultrasonic NTD methods. An analytical model, based on a ray theory, has been recently devel oped by CEA LIST and implemented in the CIVA software to evaluate the propagation of elastic waves in anisotropic and inhomogeneous media. It allows the evaluation of the ray trajectories and travel time and the computation of the amplitude along the ray t ube in a medium described thanks to a continuously varying description of its physical properties. This paper presents the work made as a part of a collaborative program between CRIEPI and CEA. The ray based model has been applied to the study of a DMW des cribed by a smooth representation of the crystallographic orientation. Comparisons of the transmitted beam and the detection of notches, located in the weld and the buttering, obtained by simulations and experiments performed on this mock up have been pres ented

Experimental visualization of ultrasonic wave propagation in dissimilar metal welds

International audienceIn nuclear power plants, a number of surface cracks attributed to stress corrosion cracking (SCC) have been detected in dissimilar metal welds (DMWs) between austenitic stainless and low alloy steels. When a crack is detected in a component of a nuclear power plant during an in-service inspection, fitness-for-service codes require that a flaw evaluation has to be conducted. Detection and sizing of such cracks with high accuracy are necessary for accurate flaw evaluation. Although ultrasonic testing (UT) is widely used in nondestructive inspection techniques for components in nuclear power plants, it is difficult to be applied to DMWs because coarse grains in DMWs scatter and attenuate ultrasonic waves severely. Moreover, anisotropic and heterogeneous properties in DMWs result in beam splitting and skewing, which reduce the detection capability and the sizing accuracy of UT. For improvement of UT capability, CEA and CRIEPI both agree to have a collaborative research program focusing on deep understanding of wave propagation within DMWs. In this program, CEA performed a simulation of wave propagation and defect response regarding DMWs by using CIVA software. And CRIEPI conducted experimental visualization of wave propagation in DMWs and ultrasonic examination by phased array technology, which is the content of this paper

Ultrasonic wave propagation in dissimilar metal welds - Application of a ray-based model and comparison with experimental results

International audienceDissimilar Metal Welds (DMW) made of nickel based alloys are widely present in some nuclear power plants at the intersection between the main pipe lines and large components such as the pressure vessel, steam generators and pressurizers. Ultrasonic NonDestructive Testing techniques (NDT) are used in order to maintain the integrity of the primary circuit and detect defects such as Stress Corrosion Cracking (SCC). Nevertheless, disturbances such as beam splitting and skewing may occur due to the anisotropic and inhomogeneous properties of the welding material. These disturbances affect the detection, localization and sizing of possible weld discontinuities. Numerical simulation tools can help to understand these physical phenomena and optimize ultrasonic NDT. A novel ray tracing algorithm has been recently developed in the CIVA platform in order to evaluate the propagation of elastic waves in anisotropic and inhomogeneous media. Based on the solving of two systems of linear ordinary differential equations of the first order, this model allows the evaluation of the ray trajectories and the travel-time, and the computation of the amplitude along a ray tube and in its vicinity. In this approach, the considered medium has to be represented by a smooth description of the elastic properties. This paper presents the work made as part of a collaborative program between CRIEPI and CEA. The ray-based model has been evaluated on a DMW mock-up described thanks to a smooth description of the crystallographic orientation of its constitutive grains. Simulated results of the transmitted beam and the detection of notches located in the weld and the buttering have been compared to experimental measurements performed on this mock-up with phased-array probes

Advanced simulation of ultrasonic inspection of welds using Dynamic Ray Tracing

13th International Symposium on Nondestructive Characterization of Materials (NDCM-XIII), 20-24 May 2013, Le Mans, France (NDCM 2013)The interpretation of on-sites inspections of austenitic or bimetallic welds is particularly difficult due to theirinternal structures. Indeed, skewing and splitting of the ultrasonic beam caused by inhomogeneity and anisotropy of the material may occur. This paper describes a ray-based model for simulating the ultrasonic wavepropagation in such structures. The formalism based on dynamic ray tracing system in Cartesian coordinatesalong a known ray consists in solving eikonal and transport equations. The ray trajectories are obtained throughthe resolution of a system of linear ordinary differential equations of the first order, whereas the computation ofray amplitude requires solving the so-called paraxial ray tracing system. This method can be applied using asmooth cartography of the weld material properties obtained thanks to image processing techniques. In this case, the orientation of grains at each point of the weld is extracted by interpolation from the cartography. We present here simulation results using this method and comparison to finite element and experimental results

Application of advanced ultrasonic testing methods to Dissimilar Metal Welds -Comparison of simulated and experimental results

International audienceWidely present in the primary circuit of Nuclear Power Plants (NPP), Dissimilar Metal Welds (DMW) are inspected using Ultrasonic nondestructive Testing (UT) techniques to ensure the integrity of the structure and detect defects such as Stress Corrosion Cracking (SCC).In a previous collaborative research, CRIEPI and CEA have worked on the understanding of the propagation of ultrasonic waves in complex materials. Indeed, the ultrasonic propagation can be disturbed due to the anisotropic and inhomogeneous properties of the medium and the interpretation of inspection results can then be difficult. An analytical model, based on a dynamic ray theory, developed by CEA-LIST and implemented in the CIVA software had been used to predict the ultrasonic propagation in a DMW. The model evaluates the ray trajectories, the travel-time and the computation of the amplitude along the ray tube in a medium described thanks to a continuously varying description of its physical properties. In this study, the weld had been described by an analytical law of the crystallographic orientation. The simulated results of the detection of calibrated notches located in the buttering and the weld had been compared with experimental data and had shown a good agreement.The new collaborative program presented in this paper aims at detecting a real SCC defect located close to the root of the DMW. Thus, simulations have been performed for a DMW described with an analytical law and a smooth cartography of the crystallographic orientation. Furthermore, advanced ultrasonic testing methods have been used to inspect the specimen and detect the real SCC defect. Experimental and simulated results of the mock-up inspection have been compared

Monitoring en ligne par fluorescence X des procédés de fabrication additive métallique

Les Journées COFREND/ COFREND DAYS, Marseille, 06 - 08 June 2023, FranceInternational audienceCette communication présente des résultats de spectrométrie par fluorescence X à dispersion d'énergie (ED-XRF) acquis durant des procédés de fabrication additive métallique. Cette technique de caractérisation sans contact et non-destructive est appliquée à deux techniques de fabrication additive métallique. Le but est de renforcer la maitrise de ces procédés et de répondre à des exigences de contrôle qualité. Deux cas d'études sont abordés, l'un concernant des mesures effectuées sur des échantillons possédant une gradation de la composition chimique de l'alliage, l'autre présentant le monitoring des fumées induites durant un procédé de fabrication additive

Implementation of non destructive testing and in-line monitoring techniques on extra-large structures printed with WAAM technology.

International audienceGrade2XL is a European project funded by the H2020 program that gathers 21 academic and industrial partners. Started in March 2020 for 4 years, the principal objective is to print extra-large structures using the WAAM (Wire Arc Additive Manufacturing) method with a complete control of the fabrication process. Since WAAM is a relatively new technology for printing large specimens, it is important to develop quality assurance methods that can be used during the fabrication and once the structure has been built, which is the focus of CEA List in the project. Regarding methods applied built structures, CEA List has investigated Resonant Ultrasound Spectroscopy (RUS) for the material characterization and more specifically the evaluation of the elastic constants or more conventional ones for the inspection with phased-array ultrasonic techniques (PAUT) or eddy current (EC) for the detection of indications are implemented and optimised them for the inspection of the final structures. Concerning the development of in-line monitoring methods, CEA List has been working on laser Doppler vibrometry (LDV) and X-ray fluorescence (XRF) spectrometry, in order to get structural information during the printing but also detect the appearance of abnormal events and correlate them to the appearance of defects generated during the WAAM process.This proceeding presents the advantages of those methods for the inspection of extra-large structures made by WAAM and discusses the first results obtained in the framework of the project

Simulation of ultrasonic inspection of dissimilar metal welds using ray-based approaches

International audienceDissimilar metal welds (DMWs) of the primary loop of French nuclear power plants exhibit complex anisotropic and inhomogeneous material properties. Ultrasonic inspections of such materials are limited due to beam attenuation, skewing and splitting. Accurate numerical simulation tools are useful to optimize Ultrasonic Non Destructive Testing, and develop new signal processing and data reconstruction techniques dedicated to inspection of DMWs. In the past years, several approaches were addressed, either relying on numerical algorithms (finite elements, finite difference-time difference) or semi-analytical techniques (ray-based approaches). This paper presents two ray-based approaches applied to the simulation of DMW inspection. Firstly, the weld material properties are described as a set of anisotropic homogeneous domains. Rays travel in straight lines between two interfaces and reflection coefficients are taken into account as the ray moves from one domain to the next. In the second approach, which is an improved version of the first approach, a smooth description of the grains orientation is considered. Such descriptions may come from a functional form which links the grains orientation to a set of parameters that must be fixed for the considered weld. Alternatively, grains orientation is obtained through an image processing technique applied to metallographic pictures of the weld. Ray propagation is then computed using a dynamic ray tracing algorithm. Here, both approaches are applied to DMWs similar to those found in French nuclear power plants. Simulation results are discussed and compared to finite elements and experimental results