TY - JOUR A1 - Giuseppe, Pignatelli A1 - Anne, Strasse A1 - Gumenyuk, Andrey A1 - Gornushkin, Igor B. T1 - Online monitoring of 3D printing of steel via optical emission spectroscopy JF - Materials Testing N2 - Additive manufacturing by laser metal deposition (LMD) requires continuous online monitoring to ensure quality of printed parts. Optical emission spectroscopy (OES) is proposed for the online detection of printing defects by monitoring minute variations in the temperature of a printed spot during laser scan. A two-lens optical system is attached to a moving laser head and focused on a molten pool created on a substrate during LMD. The light emitted by the pool is collected by an ultraviolet–visible (UV–vis) spectrometer and processed. Two metrics are used to monitor variations in the surface temperature: the spectrally integrated emission intensity and correlation coefficient. The variations in the temperature are introduced by artificial defects, shallow grooves, and holes of various widths and diameters carved on a substrate surface. The metrics show sufficient sensitivity for revealing the surface defects, except for the smallest holes with an under-millimeter diameter. Additionally, numeric simulations are carried out for the detection of emission in the UV–vis and near-infrared (NIR) spectral ranges at various surface temperatures. It is concluded that both the metrics perform better in the NIR range. In general, this work demonstrates that spectrally resolved OES suits well for monitoring surface defects during 3D metal printing. KW - Process control KW - Additive manufacturing KW - Laser metal deposition KW - Optical emission spectroscopy KW - Optical sensor PY - 2022 DO - https://doi.org/10.1515/mt-2021-2082 VL - 64 IS - 1 SP - 24 EP - 32 PB - De Gruyter AN - OPUS4-54413 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gornushkin, Igor B. A1 - Pignatelli, Giuseppe A1 - Strasse, Anne T1 - Optical detection of defects during laser metal deposition: Simulations and experiment JF - Applied surface science N2 - Laser metal deposition is a rapidly evolving method for additive manufacturing that combines high performance and simplified production routine. Quality of production depends on instrumental design and operational parameters that require constant control during the process. In this work, feasibility of using optical spectroscopy as a control method is studied via modeling and experimentally. A simplified thermal model is developed based on the time-dependent diffusion-conduction heat equation and geometrical light collection into detection optics. Intense light emitted by a laser-heated spot moving across a sample surface is collected and processed to yield the temperature and other temperature-related parameters. In a presence of surface defects the temperature field is distorted in a specific manner that depends on a shape and size of the defect. Optical signals produced by such the distorted temperature fields are simulated and verified experimentally using a 3D metal printer and a sample with artificially carved defects. Three quantities are tested as possible metrics for process monitoring: temperature, integral intensity, and correlation coefficient. The shapes of the simulated signals qualitatively agree with the experimental signals; this allows a cautious inference that optical spectroscopy is capable of detecting a defect and, possibly, predicting its character, e.g. inner or protruding. KW - Additive manufacturing KW - Laser metal deposition (LMD) KW - Thermal model KW - Optical sensor KW - Process control PY - 2021 DO - https://doi.org/10.1016/j.apsusc.2021.151214 SN - 0169-4332 VL - 570 SP - 1 EP - 13 PB - Elsevier CY - Amsterdam AN - OPUS4-53292 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wang, X.-d. A1 - Meier, R.J. A1 - Schäferling, Michael A1 - Bange, S. A1 - Lupton, J.M. A1 - Sperber, M. A1 - Wegener, J. A1 - Ondrus, V. A1 - Beifuss, U. A1 - Henne, U. A1 - Klein, C. A1 - Wolfbeis, Otto S. T1 - Two-photon excitation temperature nanosensors based on a conjugated fluorescent polymer doped with an Europium probe JF - Advanced Optical Materials N2 - A strongly fluorescent organic semiconducting polymer doped with a highly temperature dependent fluorescent europium(III) complex is converted into a nanosized material that is capable of optically sensing temperature (T) in the range from 0 to 50 °C via two-photon excitation at 720 nm. The nanosensors are prepared from a blue-fluorescent polyfluorene that acts as both a lightharvesting antenna (to capture two-photon energy) and an energy donor in a fluorescence resonance energy transfer (FRET) system. The photonic energy absorbed by the polymer is transferred to the T-sensitive red-luminescent europium complex contained in the nanoparticles. The close spatial proximity of the donor and the acceptor warrants efficient FRET. A poly(ethylene glycol)- co-poly(propylene oxide) block copolymer is also added to render the particles biocompatible. It is shown that T can be calculated from a) the intensity of the luminescence of the europium complex, b) the ratio of the intensities of the red and blue luminescence, or c) the T-dependent luminescence lifetime of the Eu(III) complex. KW - Optical sensor KW - Temperature sensor KW - Nanosensor KW - FRET system PY - 2016 UR - http://onlinelibrary.wiley.com/doi/10.1002/adom.201600601/abstract DO - https://doi.org/10.1002/adom.201600601 SN - 2195-1071 VL - 4 IS - 11 SP - 1854 EP - 1859 PB - Wiley-VCH CY - Weinheim AN - OPUS4-38737 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Witt, Jens A1 - Narbonneau, F. A1 - Schukar, Marcus A1 - Krebber, Katerina A1 - De Jonckheere, J. A1 - Jeanne, M. A1 - Kinet, D. A1 - Paquet, B. A1 - Depré, A. A1 - D´Angelo, L.T. A1 - Thiel, T. A1 - Logier, R. T1 - Medical textiles with embedded fiber optic sensors for monitoring of respiratory movement JF - IEEE Sensors Journal N2 - For patients under Magnetic Resonance Imaging (MRI) spontaneous respiration is constantly at risk of being impaired by anesthetic drugs or by upper airway obstruction. Therefore, continuous monitoring of the breathing activity is needed to assess adequate ventilation or to detect specific obstruction patterns. The paper describes three MRI compatible respiration sensors based on pure optical technologies developed within the EU FP6 project OFSETH. The sensors are based on fiber Bragg gratings, optical time-domain reflectometry and macrobending effects. The developed smart medical textiles can sense elongation up to 3% while maintaining the stretching properties of the textile substrates for patient's comfort. The OFSETH harness allows a continuous measurement of abdominal and thoracic respiration movement while all vitals organs are free for medical staff actions. The sensors were tested in MRI environment and on healthy adults. KW - Fiber optic sensor KW - Polymer optical fiber (POF) sensor KW - Respiratory sensor KW - Smart medical textile KW - MRI KW - Smart textile KW - Healthcare monitoring KW - Optical sensor KW - FBG PY - 2012 DO - https://doi.org/10.1109/JSEN.2011.2158416 SN - 1530-437X SN - 1558-1748 VL - 12 IS - 1 SP - 246 EP - 254 CY - New York, NY, USA AN - OPUS4-25649 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -