Eddy Current Sensors Optimization for Defect Detection in Parts Fabricated by Laser Powder Bed Fusion

The production of parts by additive manufacturing is an important issue for the reduction in manufacturing costs and the creation of complex geometries. Optical inspection is often implemented in the machines during the manufacturing process in order to monitor the possible generated defects. However, it is also crucial to test the quality of the manufactured parts after their fabrication and monitor their health throughout their industrial lifetime. Therefore structural health monitoring (SHM) methods need to be studied or designed. In this paper, the eddy current method is used to control fabricated parts, as this technique is adapted to detect surface and shallow defects in conductive materials. Using simulations with the CIVA non-destructive testing software package, several sensors and their parameters were tested in order to determine the most optimal ones: a separate transmitter/receiver sensor and an isotropic sensor were finally designed. The comparison of these sensors’ efficiency was made on the detection of notches and engraved letters based on simulation and experimental tests on parts fabricated by laser powder bed fusion (L-PBF) in order to determine the optimal sensor. The various tests showed that the isotropic sensor is the optimal one for the detection and characterization of defects

Development of instrumentation for eddy current in situ monitoring of laser powder bed fusion

International audienceThe laser power bed fusion (L-PBF) additive manufacturing process is commonly used for fabrication of complex metal parts. To ensure the parts’ quality, monitoring of the manufacturing process by an instrument operating continuously during the manufacturing process should be carried out. The existing industrial solutions are limited in the sense that they are restricted to the detection of anomalies within machine state parameters or in the surface layers of the part under construction. Eddy current testing is a promising non-destructive testing method that could be applied for the layer-by-layer inspection of fused material during part fabrication. This inspection enables to follow the defects evaluation not only on the surface of the last fused layer but at the scale of the several fused layers. An eddy current sensor has been developed and adapted to perform measurements in a L-PBF machine during the manufacturing phase (in situ). The performance and potential of the technique in terms of robust integration in the machine and defects evaluation have been studied. The obtained results allowed to evaluate the detection limits according to the width and the height of the defects during the manufacturing of the part. The influence of the powder presence around the fused area has also been studied

Développement de l’outil de contrôle in-situ par Courants de Foucault de pièces en cours de Fabrication pour la technique L-PBF

Les Journées COFREND/ COFREND Days, France, Marseille, 06 - 08 June 2023International audienceLe procédé de fabrication additive par fusion laser sur lit de poudre (L-PBF) est couramment utilisé pour lafabrication de pièces métalliques complexes. Pour garantir la qualité des pièces, une surveillance continue pendant le processus de fabrication par un instrument est nécessaire.Les solutions industrielles existantes sont limitées dans la mesure où elles se limitent à la détection d'anomalies dans les paramètres de l'état de la machine ou dans les couches superficielles de la pièce en cours de fabrication. Le contrôle par courants de Foucault est une méthode prometteuse de contrôle non destructif qui pourrait êtreappliquée pour l'inspection couche par couche du matériau fusionné pendant la fabrication de la pièce. Cetteinspection permet de suivre l'évaluation des défauts non seulement à la surface de la dernière couche fusionnée,mais aussi à l'échelle de plusieurs couches fusionnées. Un capteur à courants de Foucault a été développé et adapté pour effectuer des mesures dans une machine L-PBF pendant la phase de fabrication (in-situ). Les performances et le potentiel de la technique en termes d'intégration et d’évaluation des défauts dans la machine ont été étudiés.Les résultats obtenus ont permis d'évaluer les limites de détection en fonction de la largeur et de la hauteur desdéfauts pendant la fabrication de la pièce. L'influence de la présence de poudre autour de la zone fusionnée aégalement été étudiée

Development of flexible array eddy current probes for complex geometries and inspection of magnetic parts using magnetic sensors

39th Annual Review of Progress in Quantative Nondestructive Evaluation (QNDE), Denver, CO, JUL 15-20, 2012International audienceEddy Current Technique is a powerful method of inspection of metal parts. When size of flaws decreases, inspection areas become hardly accessible or material is magnetic, traditional winding coil probes are less efficient. Thanks to new CIVA simulation tools, we have designed and optimized advanced EC probes: flexible EC probe based on micro-coil arrays and EC probe with magnetic sensors, including specific electronics

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

3D magnetic imaging with GMR sensors

International audienceThis paper reports on the development of spin electronics based probes for 3D magnetic imaging. We have demonstrated the feasibility of using four orientations of magnetoresistive sensors (GMR) for the reconstruction of three dimensional components of magnetic field at the same measurement point. The use of different GMR sensor structures makes it possible to adapt the sensitivity and field range to the signal to detect for a specific application. Their characteristics and field reconstruction steps are also shown. Different examples of magnetic imaging are presented

Development of eddy current probes based on magnetoresistive sensors arrays

Conference of 40th Annual Review of Progress in Quantitative Nondestructive Evaluation, QNDE 2013, Incorporating the 10th International Conference on Barkhausen and Micro-Magnetics, ICBM 2013 ; Conference Date: 21 July 2013 Through 26 July 2013; Conference Code:105840International audienceEddy Current Technique is a powerful method for detection of surface notches and of buried flaws during inspection of metallic parts. Recent EC array probes have demonstrated a fast and efficient control of large surfaces. Nevertheless, when the size of flaws decreases or the defect is rather deep, traditional winding coil probes turn out to be useless. Magnetoresistive sensors present the advantages of flat frequency response and micron size. These sensors are hence very attractive for the detection of buried defects that require low frequencies because of skin depth effect. An optimization of the probe with magnetoresistive sensors as receivers has been made by simulations using CIVA software and finite elements methods with OPERA. EC probes for buried flaw detection have been designed. Experimental results have been compared with simulations

Magnetocardiography with sensors based on giant magnetoresistance

International audienceBiomagnetic signals, mostly due to the electrical activity in the body, are very weak and they canonly be detected by the most sensitive magnetometers, such as Superconducting QuantumInterference Devices SQUIDs. We report here biomagnetic recordings with hybrid sensors basedon Giant MagnetoResistance GMR.We recorded magnetic signatures of the electric activity of thehuman heart magnetocardiography in healthy volunteers. The P-wave and QRS complex, knownfrom the corresponding electric recordings, are clearly visible in the recordings after an averagingtime of about 1 min. Multiple recordings at different locations over the chest yielded a dipolarmagnetic field map and allowed localizing the underlying current sources. The sensitivity of theGMR-based sensors is now approaching that of SQUIDs and paves way for spin electronics devicesfor functional imaging of the body

Optimizing magnetoresistive sensor signal-to-noise via pinning field tuning

International audienceThe presence of magnetic noise in magnetoresistive-based magnetic sensors degrades their detection limit at low frequencies. In this paper, different ways of stabilizing the magnetic sensing layer to suppress magnetic noise are investigated by applying a pinning field, either by an external field, internally in the stack, or by shape anisotropy. We show that these three methods are equivalent, could be combined, and that there is a competition between noise suppression and sensitivity reduction, which results in an optimum total pinning field for which the detection limit of the sensor is improved up to a factor of 10.We acknowledge the following organisms for funding: The CEA for the internal funded projects MIMOSA and CALM and the Ph.D. Grant “Phare Amont-Aval,” the Swiss National Science Foundation for a mobility fellowship (Nos. 165238 and 177732) to A. Doll, ANR funding through Grant Nos. ANR-17-CE19-0021-01 (NeuroTMR) and ANR-18-CE42-0001 (CARAMEL). This work was supported by the EMPIR JRP 15SIB06 NanoMag through EU and EMPIR participating countries within EURAMET

Eddy Current Probes Based on Magnetoresistive Array Sensors as Receivers

International audienceEddy Current (EC) Technique is a powerful method for detection of surface notches and of buried flaws during inspection of metallic parts. This technique is used for inspection at different industrial domains like aeronautics and nuclear one. Classical winding coils are the most commonly used EC sensors. Nevertheless, when the size of flaws decreases or the defect is rather buried deep inside the material, traditional winding coil probes turn out to reach their limits. For this reason, other technologies are investigated to improve this technique. Magnetoresistive sensors present the advantages of flat frequency response and dimensions at the micron size. These sensors are hence very attractive for the detection of buried defects that require low frequencies because of skin depth effect. Also, they are suitable for small surface defects due to high spatial resolution because of their manufacturing down to one hundred µm without losing their field sensitivity. An optimization of such probes based on magnetoresistive sensors (GMR - giant magnetoresistive and MTJ – magnetic tunnel juntions) specially designed to be integrated into an eddy current probe has been experimentally studied. Measurements using MR array probes consisting of 32 GMR- and MTJ-elements, an ASIC, subsequent readout components, and emitters for EC generating inside the material under test are shown. These probes have been developed in the IMAGIC-project1 for detection and imaging of surface breaking defects and buried flaws. The performances of developed probes have been investigated for several mock-ups