TY - JOUR A1 - Hartmann, Jürgen T1 - New Developments in High-Temperature Measurement Techniques JF - International Journal of Electrical and Computer Engineering Systems Y1 - 2014 VL - 5 IS - 2 SP - 63 EP - 67 ER - TY - JOUR A1 - Hartmann, Jürgen A1 - Edler, F. A1 - Anhalt, Klaus T1 - Neuartige eutektische Metall-Kohlenstoff-Hochtemperaturfixpunkte für die Thermometrie JF - PTB Mitteilungen Y1 - 2007 UR - http://permalink.bibkatalog.de/BV035078972 VL - 117 IS - 3 SP - 256 EP - 260 ER - TY - JOUR A1 - Hartmann, Jürgen A1 - Taubert, Dieter Richard A1 - Monte, C. A1 - Gutschwager, B. A1 - Baltruschat, C. A1 - Hollandt, Jörg A1 - Kochems, D. A1 - Küchel, C. T1 - The Spectral Photon Flux of the Radiometric Calibration Spectral Source for the NIRSpec Instrument of the James Webb Space Telescope JF - Metrologia Y1 - 2009 UR - http://permalink.bibkatalog.de/BV012573233 IS - 46 SP - 207 EP - 212 ER - TY - JOUR A1 - Hartmann, Jürgen A1 - Thomas, R. A1 - Hill, K.D. A1 - Steele, A.G. A1 - Ma, C.K. T1 - Bilateral comparison of the NRC and PTB local realizations of the ITS-90 between the silver point and 1700 °C using vacuum tungsten strip lamps as transfer standards JF - Metrologia Y1 - 2006 UR - http://permalink.bibkatalog.de/BV012573233 VL - 43 IS - 03003 ER - TY - JOUR A1 - Hartmann, Jürgen A1 - Friedrich, R. A1 - Taubert, Dieter Richard A1 - Hollandt, Jörg T1 - Improved calibration of the spectral responsivity of interference filter radiometers in the visible and near infrared spectral range at PTB JF - Metrologia Y1 - 2003 UR - http://permalink.bibkatalog.de/BV012573233 IS - 40 SP - 35 EP - 38 ER - TY - JOUR A1 - Hartmann, Jürgen A1 - Anhalt, Klaus A1 - Zelenjuk, A. A1 - Taubert, Dieter Richard T1 - New PTB Set-up for the absolute calibration of the spectral responsivity of radiation thermometers JF - International Journal of Thermophysics Y1 - 2009 UR - http://permalink.bibkatalog.de/BV013298193 IS - 30 SP - 192 EP - 202 ER - TY - JOUR A1 - Hartmann, Jürgen A1 - Ma, C.K. A1 - Gibson, C. T1 - Decreasing dependence of the calibration of the tungsten strip lamp on the temperature of the lamp base with increasing filament length JF - Metrologia Y1 - 2005 UR - http://permalink.bibkatalog.de/BV012573233 IS - 42 SP - 383 EP - 388 ER - TY - JOUR A1 - Hartmann, Jürgen A1 - Anhalt, Klaus A1 - Wang, Y. A1 - Yamada, Y. T1 - Large and small aperture Fixed-point cells of Cu, Pt-C, and Re-C JF - International Journal of Thermophysics Y1 - 2008 UR - http://permalink.bibkatalog.de/BV013298193 IS - 29 SP - 969 EP - 983 ER - TY - JOUR A1 - Hartmann, Jürgen A1 - Werner, L. T1 - Radiation thermometry towards the triple point of water? JF - International Journal of Thermophysics Y1 - 2008 UR - http://permalink.bibkatalog.de/BV013298193 IS - 29 SP - 1052 EP - 1065 ER - TY - JOUR A1 - Hartmann, Jürgen T1 - Correct consideration of the index of refraction using blackbody radiation JF - Optics Express Y1 - 2006 UR - http://permalink.bibkatalog.de/BV013253264 VL - 14 IS - 18 SP - 8121 EP - 8126 ER - TY - JOUR A1 - Hartmann, Jürgen T1 - Advanced comparator method for measuring ultra small aperture areas JF - Meas.Sci.Techn. Y1 - 2001 IS - 12 SP - 1678 EP - 1682 ER - TY - JOUR A1 - Hartmann, Jürgen A1 - Lowe, D. A1 - Anhalt, Klaus T1 - Construction and validation of a platinum-carbon eutectic fixed-point JF - Metrologia Y1 - 2008 UR - http://permalink.bibkatalog.de/BV012573233 IS - 45 SP - 325 EP - 329 ER - TY - JOUR A1 - Wehnert, Kira-Kristin A1 - Ochs, Dennis A1 - Schmitt, Jan A1 - Hartmann, Jürgen A1 - Schiffler, Andreas T1 - Reducing Lifecycle Costs due to Profile Scanning of the Powder Bed in Metal Printing JF - Procedia CIRP 98 N2 - First time right is one major goal in powder based 3D metal printing. Reaching this goal is driven by reducing life cycle costs for quality measures, to minimize scrap rate and to increase productivity under optimal resource efficiency. Therefore, monitoring the state of the powder bed for each printed layer is state of the art in selective laser melting. In the most modern approaches the quality monitoring is done by computer vision systems working with an interference on trained neural networks with images taken after exposure and after recoating. There are two drawbacks of this monitoring method: First, the sensor signals - the image of the powder bed - give no direct height information. Second, the application of this method needs to be trained and labeled with reference images for several cases. The novel approach presented in this paper uses a laser line scanner attached to the recoating machine. With this new concept, a direct threshold measure can be applied during the recoating process to detect deviations in height level without prior knowledge. The evaluation can be done online during recoating and feedback to the controller to monitor each individual layer. Hence, in case of deviations the location in the printing plane is an inherent measurement and will be used to decide which severity of error is reported. The signal is used to control the process, either by starting the recoating process again or stopping the printing process. With this approach, the sources of error for each layer can be evaluated with deep information to evaluate the cause of the error. This allows a reduction of failure in the future, which saves material costs, reduces running time of the machine life cycle phase in serial production and results in less rework for manufactured parts. Also a shorter throughput time per print job results, which means that the employee can spent more time to other print jobs and making efficient use of the employee’s work force. In summary, this novel approach will not only reduce material costs but also operating costs and thus optimize the entire life cycle cost structure. The paper presents a first feasibility and application of the described approach for test workpieces in comparison to conventional monitoring systems on an EOS M290 machine. Y1 - 2021 UR - 10.1016/j.procir.2021.01.175 VL - 98 SP - 684 EP - 689 PB - Elsevir ER - TY - JOUR A1 - Hay, Bruno A1 - Beaumont, Oliver A1 - Lambeng, Nora A1 - Cataldi, Michel A1 - Lorrette, Christophe A1 - Knopp, Kevin A1 - Hartmann, Jürgen A1 - Beckstein, Fabia A1 - Stobitzer, Dorothea A1 - Milošević, Nenad A1 - Stepanic, Nenad A1 - Wu, Jiyu A1 - Mildeova, Petra T1 - Inter‑laboratory Comparison on Thermal Diffusivity Measurements by the Laser Flash Method at Ultra‑high Temperature JF - International Journal of Thermophysics N2 - thermal diffusivity measurements by the laser flash method in the temperature range from 23 °C to 3000 °C. The main objective was to assess the variability and coherency of thermal diffusivity measurements performed at ultra-high temperatures at the European level. Three refractory materials (molybdenum, tungsten and isotropic graphite IG210) were selected for this inter-laboratory comparison, due to their high melting point. The disk-shaped specimens needed were machined from the same blocks of materials in order to reduce any potential scattering of results between participants due to inhomogeneity effects. The homogeneity of the sets of specimens was studied by the pilot laboratory (LNE) before launching the comparison process. Thermal diffusivity measurements were then carried out by the seven participants on the three materials during two successive thermal cycles up to the maximum temperatures that can be reached by the devices used. The analysis of results showed a good agreement between the participants for temperatures above 400 °C, with relative deviations within the uncertainties of measurement and lower than ± 4 % for molybdenum, ± 5 % for isotropic graphite and ± 9 % for tungsten. Y1 - 2023 UR - https://doi.org/10.1007/s10765-023-03159-5 VL - 2023 SP - 44 EP - 48 ER -