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

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

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

Ultra-low-field MRI and its combination with MEG

| openaire: EC/H2020/686865/EU//BREAKBENRecent progress in SQUID instrumentation has demonstrated the feasibility of using SQUID sensor arrays in MEG helmets to record also MRI data. Here we describe the basic principles of MRI as well as the special requirements and solutions needed to perform ultra-low-field MRI concurrently with MEG. We consider it is feasible to build practical MEG-MRI instruments for scientific experimentation and for clinical use. Acquiring an MRI with 2-mm spatial resolution and sufficient signal-to-noise ratio and contrast appears achievable without essentially lengthening the normal MEG measurement time.Peer reviewe