TY - JOUR A1 - Nicolicea, Alberto A1 - Oliveros-Mata, E. S. A1 - Zabila, Y. A1 - Makarov, D. A1 - Melzer, Michael A1 - Pelkner, Matthias T1 - Flexible anisotropic magnetoresistive sensors for novel magnetic flux leakage testing capabilities N2 - Rigid magnetic field sensors such as anisot Hall sensors have been used for years and have become industry standard for electromagnetic non-destructive testing (NDT). Recent technological developments in the field of flexible electronics allow for the fabrication of reshapeable magnetic field sensors on flexible substrates via thin-film deposition or printing. The magnetic properties of these sensors have comparable characteristics to industry-standard rigid magnetic field sensors, with the added ability of adapting to the surface of complex components and scanning in contact with the sample surface. This improves defect detectability and magnetic signal strength by minimizing the scanning lift-off (LO) distance. In this article flexible AMR sensors mounted on a rotative mechanical holder were used to scan a semi-circular ferromagnetic sample with 3 reference defects via magnetic flux leakage (MFL) testing, thus demonstrating the applicability of this type of sensors for the scanning of curved samples. In order to benchmark the performance of these sensors in comparison to industry standard rigid magnetic field sensors, a ferromagnetic sample with 10 reference defects of different depths was scanned employing flexible AMR and rigid GMR sensors. Defects with depths ranging from 110 μm up to 2240 μm were detected with an signal-tonoise ratio (SNR) of 2.7 up to 27.9 (for flexible AMR sensors) and 6.2 up to 72.3 (for rigid GMR sensors), respectively. A 2D magnetometer mapping of the sample with a spatial scanning step of 10 × 50 μm2 (flexible AMR) and 16 × 100 μm2 (rigid GMR) was obtained. The results show that this type of sensor can be used for high-resolution and high-detail mapping of defects on the surface of planar and non-planar ferromagnetic samples since the scanning lift-off distance is equal to the substrate thickness of 20 μm for in-contact scanning. The SNR comparison between flexible and rigid sensors shows that the performance of the flexible AMR sensors employed is not very far behind the performance of the rigid GMR sensors used. KW - Flexible magnetic field sensors KW - Non-destructive testing KW - Magnetic flux leakage KW - Thin film sensor fabrication KW - Defect detection PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-603931 DO - https://doi.org/10.1016/j.ndteint.2024.103160 SN - 0963-8695 VL - 146 SP - 1 EP - 15 PB - Elsevier CY - Amsterdam AN - OPUS4-60393 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nicolicea, Alberto A1 - Oliveros-Mata, E. S. A1 - Makarov, D. A1 - Melzer, Michael A1 - Pelkner, Matthias T1 - Flexible anisotropic magnetoresistive sensors for novel eddy current testing applications N2 - The standard method for eddy current testing (ET) of conductive materials relies on using rigid coils. In recent years magnetoresistive (MR) sensors in combination with an excitation wire have become a promising candidate for this application since it would increase the spatial resolution. New developments in flexible electronics have enabled the production of flexible sensors with the novel capability of scanning samples in conformal contact with the surface. In this article flexible anisotropic magnetoresistive (AMR) sensors were used in combination with a thin induction wire to perform eddy current testing of a curved aluminum sample with several defects imprinted on its surface. To benchmark the performance of this new method, a flat sample with reference defects of various dimensions was also scanned using flexible AMR sensors, inductive coils and rigid giant magnetoresistive (GMR) sensors. The results show that this new method of using flexible magnetic field sensors coupled with an excitation wire can easily be applied to the scanning of curved samples, while in the benchmark test employing the flat sample, the performance is not far behind more conventional techniques, with defects with depths down to 30 μm and widths down to 400 μm being detectable with an SNR of 3 (signal magnitude) and 8 (signal phase shift) at the excitation frequency of 50 kHz, and defects with depths down to 30 μm and widths down to 600 μm being detectable with an SNR of 10 (signal magnitude) and 17 (signal phase shift) at 260 kHz. KW - Magnetic field sensors KW - Flexible magnetic field sensors KW - Flexible electronics KW - Non-destructive testing KW - Eddy current testing KW - Thin film sensor fabrication KW - Defect detection KW - Magnetism PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-634325 DO - https://doi.org/10.1016/j.measurement.2025.117340 SN - 1873-412X VL - 253, Part A SP - 1 EP - 15 PB - Elsevier CY - Amsterdam AN - OPUS4-63432 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Janssen, J. A1 - Makarov, E. A1 - Hickel, Tilmann A1 - Shapeev, A.V. A1 - Neugebauer, J. T1 - Automated optimization and uncertainty quantification of convergence parameters in plane wave density functional theory calculations N2 - First principles approaches have revolutionized our ability in using computers to predict, explore, and design materials. A major advantage commonly associated with these approaches is that they are fully parameter-free. However, numerically solving the underlying equations requires to choose a set of convergence parameters. With the advent of high-throughput calculations, it becomes exceedingly important to achieve a truly parameter-free approach. Utilizing uncertainty quantification (UQ) and linear decomposition we derive a numerically highly efficient representation of the statistical and systematic error in the multidimensional space of the convergence parameters for plane wave density functional theory (DFT) calculations. Based on this formalism we implement a fully automated approach that requires as input the target precision rather than convergence parameters. The performance and robustness of the approach are shown by applying it to a large set of elements crystallizing in a cubic fcc lattice. KW - Ab initio simulations KW - High throughput KW - convergence parameter PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-618632 DO - https://doi.org/10.1038/s41524-024-01388-2 VL - 10 IS - 1 SP - 1 EP - 11 PB - Springer Science and Business Media LLC AN - OPUS4-61863 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -