@article{Hartmann, author = {Hartmann, J{\"u}rgen}, title = {New Developments in High-Temperature Measurement Techniques}, series = {International Journal of Electrical and Computer Engineering Systems}, volume = {5}, journal = {International Journal of Electrical and Computer Engineering Systems}, number = {2}, pages = {63 -- 67}, language = {en} } @article{BlotevogelEgermannGoldlueckeetal., author = {Blotevogel, Thomas and Egermann, Jan and Goldl{\"u}cke, J{\"u}rgen and Leipertz, Alfred and Hartmann, Matthias and Schenk, Martin and Berckmueller, Martin}, title = {Developing Planar Laser-Induced Fluorescence for the Investigation of the Mixture Formation Process in Hydrogen Engines}, series = {SAE Paper}, journal = {SAE Paper}, number = {2004-01-1408}, language = {en} } @incollection{BlotevogelGoldlueckeEgermannetal., author = {Blotevogel, Thomas and Goldl{\"u}cke, J{\"u}rgen and Egermann, Jan and Leipertz, Alfred and Hartmann, Matthias and Rottengruber, Hermann}, title = {Untersuchung der Gemischbildung von Gasmotoren mit Hilfe laseroptischer Messverfahren}, series = {Der Arbeitsprozess des Verbrennungsmotors (10. Tagung)}, booktitle = {Der Arbeitsprozess des Verbrennungsmotors (10. Tagung)}, editor = {Eichlseder, Helmut}, publisher = {Verlag der Technischen Universit{\"a}t Graz}, address = {Graz}, pages = {139 -- 166}, language = {de} } @article{HartmannEdlerAnhalt, author = {Hartmann, J{\"u}rgen and Edler, F. and Anhalt, Klaus}, title = {Neuartige eutektische Metall-Kohlenstoff-Hochtemperaturfixpunkte f{\"u}r die Thermometrie}, series = {PTB Mitteilungen}, volume = {117}, journal = {PTB Mitteilungen}, number = {3}, pages = {256 -- 260}, language = {de} } @article{HartmannTaubertMonteetal., author = {Hartmann, J{\"u}rgen and Taubert, Dieter Richard and Monte, C. and Gutschwager, B. and Baltruschat, C. and Hollandt, J{\"o}rg and Kochems, D. and K{\"u}chel, C.}, title = {The Spectral Photon Flux of the Radiometric Calibration Spectral Source for the NIRSpec Instrument of the James Webb Space Telescope}, series = {Metrologia}, journal = {Metrologia}, number = {46}, pages = {207 -- 212}, language = {en} } @article{HartmannThomasHilletal., author = {Hartmann, J{\"u}rgen and Thomas, R. and Hill, K.D. and Steele, A.G. and Ma, C.K.}, title = {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}, series = {Metrologia}, volume = {43}, journal = {Metrologia}, number = {03003}, language = {en} } @article{HartmannFriedrichTaubertetal., author = {Hartmann, J{\"u}rgen and Friedrich, R. and Taubert, Dieter Richard and Hollandt, J{\"o}rg}, title = {Improved calibration of the spectral responsivity of interference filter radiometers in the visible and near infrared spectral range at PTB}, series = {Metrologia}, journal = {Metrologia}, number = {40}, pages = {35 -- 38}, language = {en} } @article{HartmannAnhaltZelenjuketal., author = {Hartmann, J{\"u}rgen and Anhalt, Klaus and Zelenjuk, A. and Taubert, Dieter Richard}, title = {New PTB Set-up for the absolute calibration of the spectral responsivity of radiation thermometers}, series = {International Journal of Thermophysics}, journal = {International Journal of Thermophysics}, number = {30}, pages = {192 -- 202}, language = {en} } @article{HartmannMaGibson, author = {Hartmann, J{\"u}rgen and Ma, C.K. and Gibson, C.}, title = {Decreasing dependence of the calibration of the tungsten strip lamp on the temperature of the lamp base with increasing filament length}, series = {Metrologia}, journal = {Metrologia}, number = {42}, pages = {383 -- 388}, language = {en} } @article{HartmannAnhaltWangetal., author = {Hartmann, J{\"u}rgen and Anhalt, Klaus and Wang, Y. and Yamada, Y.}, title = {Large and small aperture Fixed-point cells of Cu, Pt-C, and Re-C}, series = {International Journal of Thermophysics}, journal = {International Journal of Thermophysics}, number = {29}, pages = {969 -- 983}, language = {en} } @article{HartmannWerner, author = {Hartmann, J{\"u}rgen and Werner, L.}, title = {Radiation thermometry towards the triple point of water?}, series = {International Journal of Thermophysics}, journal = {International Journal of Thermophysics}, number = {29}, pages = {1052 -- 1065}, language = {en} } @article{Hartmann, author = {Hartmann, J{\"u}rgen}, title = {Correct consideration of the index of refraction using blackbody radiation}, series = {Optics Express}, volume = {14}, journal = {Optics Express}, number = {18}, pages = {8121 -- 8126}, language = {en} } @article{Hartmann, author = {Hartmann, J{\"u}rgen}, title = {Advanced comparator method for measuring ultra small aperture areas}, series = {Meas.Sci.Techn.}, journal = {Meas.Sci.Techn.}, number = {12}, pages = {1678 -- 1682}, language = {en} } @article{HartmannLoweAnhalt, author = {Hartmann, J{\"u}rgen and Lowe, D. and Anhalt, Klaus}, title = {Construction and validation of a platinum-carbon eutectic fixed-point}, series = {Metrologia}, journal = {Metrologia}, number = {45}, pages = {325 -- 329}, language = {en} } @article{HoefflinHartmannRosiliusetal., author = {H{\"o}fflin, Dennis and Hartmann, J{\"u}rgen and Rosilius, Maximilian and Seitz, Philipp and Schiffler, Andreas}, title = {Opto-Thermal Investigation of Additively Manufactured Steel Samples as a Function of the Hatch Distance}, series = {Sensors}, volume = {22}, journal = {Sensors}, number = {1}, publisher = {MDPI}, issn = {1424-8220}, doi = {10.3390/s22010046}, pages = {46}, abstract = {Nowadays, additive manufacturing processes are becoming more and more appealing due to their production-oriented design guidelines, especially with regard to topology optimisation and minimal downstream production depth in contrast to conventional technologies. However, a scientific path in the areas of quality assurance, material and microstructural properties, intrinsic thermal permeability and dependent stress parameters inhibits enthusiasm for the potential degrees of freedom of the direct metal laser melting process (DMLS). Especially in quality assurance, post-processing destructive measuring methods are still predominantly necessary in order to evaluate the components adequately. The overall objective of these investigations is to gain process knowledge make reliable in situ statements about component quality and material properties based on the process parameters used and emission values measured. The knowledge will then be used to develop non-destructive tools for the quality management of additively manufactured components. To assess the effectiveness of the research design in relation to the objectives for further investigations, this pre-study evaluates the dependencies between the process parameters, process emission during manufacturing and resulting thermal diffusivity and the relative density of samples fabricated by DMLS. Therefore, the approach deals with additively built metal samples made on an EOS M290 apparatus with varying hatch distances while simultaneously detecting the process emission. Afterwards, the relative density of the samples is determined optically, and thermal diffusivity is measured using the laser flash method. As a result of this pre-study, all interactions of the within factors are presented. The process variable hatch distance indicates a strong influence on the resulting material properties, as an increase in the hatch distance from 0.11 mm to 1 mm leads to a drop in relative density of 57.4\%. The associated thermal diffusivity also reveals a sharp decrease from 5.3 mm2/s to 1.3 mm2/s with growing hatch distances. The variability of the material properties can also be observed in the measured process emissions. However, as various factors overlap in the thermal radiation signal, no clear assignment is possible within the scope of this work.}, language = {en} } @article{WehnertOchsSchmittetal., author = {Wehnert, Kira-Kristin and Ochs, Dennis and Schmitt, Jan and Hartmann, J{\"u}rgen and Schiffler, Andreas}, title = {Reducing Lifecycle Costs due to Profile Scanning of the Powder Bed in Metal Printing}, series = {Procedia CIRP 98}, volume = {98}, journal = {Procedia CIRP 98}, publisher = {Elsevir}, pages = {684 -- 689}, abstract = {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.}, language = {en} } @article{HayBeaumontLambengetal., author = {Hay, Bruno and Beaumont, Oliver and Lambeng, Nora and Cataldi, Michel and Lorrette, Christophe and Knopp, Kevin and Hartmann, J{\"u}rgen and Beckstein, Fabia and Stobitzer, Dorothea and Milošević, Nenad and Stepanic, Nenad and Wu, Jiyu and Mildeova, Petra}, title = {Inter‑laboratory Comparison on Thermal Diffusivity Measurements by the Laser Flash Method at Ultra‑high Temperature}, series = {International Journal of Thermophysics}, volume = {2023}, journal = {International Journal of Thermophysics}, pages = {44 -- 48}, abstract = {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.}, language = {en} } @article{ManaraHartmannKerwagenetal., author = {Manara, Jochen and Hartmann, J{\"u}rgen and Kerwagen, Fabian and Maak, Christoph and Muscio, Albert and Paeth, Heiko and Ebert, Hans-Peter}, title = {Passive Radiative Cooling Materials with Special Focus on the Reduction of Urban Heat Island Effect: A Current Summarized Classification of Need, Approaches and Characterization Methods}, series = {International Journal of Thermophysics}, volume = {46}, journal = {International Journal of Thermophysics}, number = {58}, doi = {10.1007/s10765-025-03529-1}, abstract = {Rapidly rising global temperatures and the intensification of the urban heat island (UHI) effect necessitate new, energy-efficient solutions to mitigate heat stress in cities. Passive radiative cooling (PRC) offers a highly promising, low-energy pathway to achieve sub-ambient temperatures by reflecting incoming solar radiation while emitting long-wave infrared radiation through the atmospheric infrared window. This review summarizes key aspects of PRC and its role in reducing UHI impacts. Furthermore the fundamental physics of heat transfer and radiative heat exchange, including the materials properties such as solar reflectance and thermal emissivity which are correlated with the figures of merit, temperature drop below ambient temperature and cooling power. A comprehensive classification of current PRC materials is presented based on both structural architectures and physical effects. Additionally an overview on measurement techniques are employed to determine the performance of PRC materials, focusing on the key performance indicators. For this purpose in-field as wells as laboratory measurement techniques are introduced and opportunities in standardizing testing protocols are highlighted. Finally, future research directions are outlined, focusing on novel material development, theoretical advancements, scalable fabrication processes, and integration strategies within urban infrastructures. These innovations are important for enhancing building energy efficiency, reducing urban heat stress, and promoting sustainable urban development in the face of climate change.}, language = {en} } @incollection{BlotevogelGoldlueckeEgermannetal., author = {Blotevogel, Thomas and Goldl{\"u}cke, J{\"u}rgen and Egermann, Jan and Leipertz, Alfred and Hartmann, Matthias and Schenk, Martin and Berckm{\"u}ller, Martin}, title = {Gemischbildungsuntersuchung in Gasmotoren mittels optischer Messverfahren, speziell in Wasserstoffmotoren}, series = {Gasfahrzeuge}, booktitle = {Gasfahrzeuge}, editor = {Dingel, Oliver}, publisher = {expert verlag}, address = {Renningen}, isbn = {3816924395}, publisher = {Hochschule f{\"u}r Angewandte Wissenschaften W{\"u}rzburg-Schweinfurt}, pages = {205 -- 229}, abstract = {Planar laser-induced fluorescence (PLIF) has been successfully used for the investigation of the mixture formation process in hydrogen engines for passenger cars. Detailed information has been obtained about process development (qualitative measurement) and on fuel/air-ratio (quantitative measurement) inside the combustion chamber. These results can be used for further optimization of mixture formation and combustion process concerning emissions and fuel consumption. The measurement technique used is not only limited to hydrogen or to passenger car engines, but can also be applied to other fuel gases like natural gas or to other engine sizes like bus engines. The main topic of this paper is the experimental verification of the procedure which was executed by simultaneous PLIF and Raman scattering measurements. By Raman scattering the fuel/air-ratio can directly be determined from direct concentration measurements of the different gas species. The fuel/air-ratios determined by PLIF and Raman measurements are in good agreement indicating that a quantitative fuel/air-ratio measurement during the mixture formation process of gas and hydrogen engines is possible by PLIF. This fact is also confirmed by other measurements, e.g., global fuel/air-ratio calculated from measured intake air and fuel gas flow.}, language = {de} } @article{StrasserMoukhinaHartmann, author = {Strasser, Claire and Moukhina, Elena and Hartmann, J{\"u}rgen}, title = {Time-Temperature-Transformation (TTT) Cure Diagram of an Epoxy-Amine System}, series = {Macromolecular Theory and Simulations}, volume = {33}, journal = {Macromolecular Theory and Simulations}, number = {6}, pages = {2400039}, language = {en} }