@article{KnoppShandyManaraetal., author = {Knopp, Kevin and Shandy, Amir and Manara, Jochen and Vidi, Stephan and Hartmann, J{\"u}rgen}, title = {Metrologische Apparaturen zur Messung thermophysikalischer Materialeigenschaften bei sehr hohen Temperaturen im EU-Projekt Hi-TRACE}, series = {FHWS Science Journal}, volume = {5}, journal = {FHWS Science Journal}, number = {2}, issn = {2196-6095}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:863-opus-20046}, pages = {83 -- 92}, abstract = {Industriezweige wie die Glas-Industrie, die Kraftwerkstechnik sowie die Luft- und Raumfahrttechnik m{\"u}ssen kontinuierlich neue Methoden entwickeln, sowie bestehende Verfahren optimieren, um in ihren Bereichen wettbewerbsf{\"a}hig zu sein bzw. neue Anforderungen an Umwelt- und Klimaschutz zu erf{\"u}llen. Dies beinhaltet oft die Entwicklung neuer Materialien, die leichter zu fabrizieren sind und sowohl mechanisch als auch thermisch h{\"o}heren Belastungen standhalten. F{\"u}r die genannten Industriezweige sind Prozesse mit hohen Betriebstemperaturen bis zu 3.000 °C kennzeichnend und damit ist die Kenntnis von Materialeigenschaften bei diesen extremen Temperaturen von großer Bedeutung. Auch wenn es bereits einige Messapparaturen f{\"u}r die Bestimmung von thermophysikalischen Materialdaten bei hohen Temperaturen gibt, muss die R{\"u}ckf{\"u}hrung dieser auf die SI Basiseinheiten gew{\"a}hrleistet werden, um die Zuverl{\"a}ssigkeit der gemessenen Daten f{\"u}r die Anforderung der genannten Branchen sicherzustellen. Diese Aufgabe ist das Ziel des EMPIR-(European Metrology Programme for Innovation and Research) Projektes Hi-TRACE [1]. Hi-TRACE zielt darauf ab, Referenzapparaturen und neue Methoden f{\"u}r die Messung von thermophysikalischen Materialeigenschaften, (thermische Diffusivit{\"a}t, spezifische W{\"a}rme, Emissionsgrad und Schmelztemperatur) sowie der Haftung von Schichten {\"u}ber 1.000 °C zu bestimmen.}, language = {de} } @article{OchsWehnertKnoppetal., author = {Ochs, Dennis and Wehnert, Kira-Kristin and Knopp, Kevin and Hartmann, J{\"u}rgen and Versch, Alexander and Schiffler, Andreas}, title = {Untersuchungen zur Temperaturleitf{\"a}higkeit additiv gefertigter Stahlproben in Abh{\"a}ngigkeit der relativen Dichte}, series = {FHWS Science Journal}, volume = {5}, journal = {FHWS Science Journal}, number = {2}, issn = {2196-6095}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:863-opus-19986}, pages = {75 -- 82}, abstract = {Das direkte Metall-Laser-Schmelzen (DMLS) aus der Familie der Additiven Fertigungsverfahren (AM) erm{\"o}glicht die schichtweise Erzeugung komplexer dreidimensionaler Geometrien mit hoher relativer Dichte unter Verwendung von Metallpulver als Ausgangsmaterial [1]. Die Technologie wird zunehmend eingesetzt, um innovative Bauteile material- und gewichtssparend herzustellen oder komplexe Produkte ohne zus{\"a}tzliche Werkzeuge oder Spannvorrichtungen zu fertigen. Dar{\"u}ber hinaus sind Funktionsintegrationen, zum Beispiel Gussformen mit eingepr{\"a}gten K{\"u}hlkan{\"a}len, m{\"o}glich. Da einzelne Metallpulverschichten auf vorhergehende Schichten aufgeschmolzen werden, entstehen w{\"a}hrend der Herstellung des Bauteils komplexe, zeitabh{\"a}ngige Temperaturprofile [2]. Durch den Einsatz hoher Laserintensit{\"a}ten und Scangeschwindigkeiten, bei denen die Belichtungszeit der Laserbestrahlung im Bereich von Millisekunden liegt, werden zudem extrem hohe Aufheiz- und Abk{\"u}hlraten induziert, die zu einzigartigen Mikrostrukturen und Materialeigenschaften f{\"u}hren [3]. Diese extremen Prozessbedingungen k{\"o}nnen sich jedoch auch negativ auf den Fertigungsprozess auswirken. Bei komplexen Bauteilen bleibt die Prozessstabilit{\"a}t und Qualit{\"a}tssicherung Umfragen zufolge weiterhin die wichtigste technologische Barriere f{\"u}r den Einsatz additiv gefertigter Bauteile in hochbelasteten oder sicherheitsrelevanten Bereichen [4]. Daher verspricht der Zusammenhang zwischen Temperaturprofil w{\"a}hrend der Fertigung, relativer Dichte der Bauteile, sowie thermophysikalischer Eigenschaften additiv gefertigter Proben wichtige Erkenntnisse, insbesondere im Hinblick auf eine zerst{\"o}rungsfreie Qualit{\"a}tssicherung, sowie neue Anwendungsm{\"o}glichkeiten.}, language = {de} } @article{HoefflinSauerSchiffleretal., author = {H{\"o}fflin, Dennis and Sauer, Christian and Schiffler, Andreas and Hartmann, J{\"u}rgen}, title = {Process Monitoring Using Synchronized Path Infrared Thermography in PBF-LB/M}, series = {Sensors}, volume = {22}, journal = {Sensors}, number = {16}, publisher = {MDPI}, doi = {10.3390/s22165943}, pages = {5943}, abstract = {Additive manufacturing processes, particularly Laser-Based Powder Bed Fusion of Metals (PBF-LB/M), enable the development of new application possibilities due to their manufacturing-specific freedom of design. These new fields of application require a high degree of component quality, especially in safety-relevant areas. This is currently ensured primarily via a considerable amount of downstream quality control. Suitable process monitoring systems promise to reduce this effort drastically. This paper introduces a novel monitoring method in order to gain process-specific thermal information during the manufacturing process. The Synchronized Path Infrared Thermography (SPIT) method is based on two synchronized galvanometer scanners allowing high-speed and high-resolution observations of the melt pool in the SWIR range. One scanner is used to steer the laser over the building platform, while the second scanner guides the field of view of an IR camera. With this setup, the melting process is observed at different laser powers, scan speeds and at different locations with respect to the laser position, in order to demonstrate the positioning accuracy of the system and to initially gain thermal process data of the melt pool and the heat-affected zone. Therefore, the SPIT system shows a speed independent overall accuracy of ±2 Pixel within the evaluated range. The system further allows detailed thermal observation of the melt pool and the surrounding heat-affected zone.}, 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} } @inproceedings{HartmannLenskiOchsetal., author = {Hartmann, J{\"u}rgen and Lenski, Philipp and Ochs, Dennis and Shandy, Amir and Winterstein, A. and Versch, Alexander and Schiffler, Andreas}, title = {Thermische Prozess{\"u}berwachung f{\"u}r additive Fertigungsverfahren}, address = {Berlin}, language = {de} } @inproceedings{HartmannOchsLenskietal., author = {Hartmann, J{\"u}rgen and Ochs, Dennis and Lenski, Philipp and Schiffler, Andreas and Versch, Alexander and Manara, Jochen}, title = {Thermal process monitoring for additive manufacturing}, address = {Darmstadt}, language = {en} } @inproceedings{BlotevogelEgermannGoldlueckeetal., author = {Blotevogel, Thomas and Egermann, Jan and Goldl{\"u}cke, J{\"u}rgen and Leipertz, Alfred and Hartmann, Matthias and Schenk, Martin and Berckm{\"u}ller, Martin}, title = {Untersuchungen zur Gemsichbildung in Wasserstoffmotoren}, editor = {Leipertz, Alfred}, publisher = {Esytec}, address = {Erlangen}, isbn = {3-931901-27-0}, pages = {12}, abstract = {Mittels der planaren laserinduzierten Fluoreszenz (PLIF) k{\"o}nnen im Brennraum eines Transparentmotors Messungen durchgef{\"u}hrt werden, die den Gemischbildungsprozess beim Wasserstoffmotor zweidimensional qualitativ darstellen. Auch quantitative Messungen und damit Aussagen {\"u}ber das Kraftstoff-Luft-Verh{\"a}ltnis im Brennraum sind m{\"o}glich. F{\"u}r diese Messungen wird ein Gasgemisch ans Helium und einer Tracersubstanz verwendet, und der Motor wird geschleppt. Bei Betrieb des Motors in der Teillast sind auch Messungen im gefeuerten Betrieb, d.h. mit Wasserstoff und zugesetzter Tracersubstanz, m{\"o}glich. Durch direkte Messung des Kraftstoff-Luft-Verh{\"a}ltnisses und der Wasserstoffkonzentration am befeuerten Aggregat mit Hilfe der Raman-Spektroskopie konnte nachgewiesen werden, daß mittels PLIF der Einstr{\"o}mvorgang qualitativ und das Kraftstoff-Luft-Verh{\"a}ltnis quantitativ grunds{\"a}tzlich richtig erfaßt werden. Qualitative und quantitative PLIF-Messungen sind prinzipiell nicht nur bei Wasserstoffmotoren, sondern auch bei Gasmotoren mit anderen Brenngasen denkbar. Allerdings sind noch weitere Arbeiten erforderlich, um den Quantifizierungsfehler deutlich abzusenken. Zuk{\"u}nftiges Verbesserungspotential f{\"u}r diese Meßtechnik besteht in verschiedenen Punkten. Dazu geh{\"o}rt die Optimierung und Anpassung der Mischstrecke zur Erzeugung des Gas-Luft-Gemisches mit definiertem Kraftstoff-Luft-Verh{\"a}ltnis an die jeweiligen Meßaufgaben, um den relativen Fehler des Lambda-Wertes noch weiter zu reduzieren. Eine Verringerung der Tracerkonzentration erscheint problemlos m{\"o}glich. Um das Problem der Hintergrundfluoreszenz zu l{\"o}sen, sind verschiedene M{\"o}glichkeiten denkbar, die noch genauer zu untersuchen sind.}, language = {de} } @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} } @inproceedings{HartmannDobhanEngelmannetal., author = {Hartmann, J{\"u}rgen and Dobhan, Alexander and Engelmann, Bastian and Eberhardt, Lars and Heusinger, Moritz and Raab, C and Schleif, Frank-Michael and T{\"u}rk, M.}, title = {Optimierung von Prozessen und Werkzeugmaschinen durch Bereitstellung, Analyse und Soll-Ist-Vergleich von Produktionsdaten: Digitalkonferenz}, language = {en} } @inproceedings{HartmannHarrerDotterweichetal., author = {Hartmann, J{\"u}rgen and Harrer, S. and Dotterweich, C. and Zink, Markus H. and Hemberger, Frank and Ebert, Hans-Peter and Schnitzler, Tim}, title = {Phase change materials for use in thermally and electrically stressed insulation for high voltage applications}, series = {2016 IEEE Electrical Insulation Conference}, booktitle = {2016 IEEE Electrical Insulation Conference}, publisher = {IEEE}, isbn = {978-1-4673-8706-4}, pages = {605 -- 608}, abstract = {The temperature of high voltage equipment is often the limiting factor when transmitting electrical energy because the electrical insulation can get severely aged when the temperature is exceeding a certain limit. Hence, cooling has to be improved or heat generation must be reduced to avoid damage of the insulation. In this paper a new method was examined by investigating electrically insulating phase change materials which are able to store latent heat during a phase change from the solid to liquid state in times of high energy demand. To verify the electrically insulating properties of paraffins, one class of phase change materials, a special test cell was designed allowing the determination of breakdown voltage of phase change materials. The measurements on one paraffin sample proved the promising electrical insulating properties and it was shown that the breakdown voltage in the liquid state is comparable …}, language = {en} } @inproceedings{ZinkDotterweichHartmannetal., author = {Zink, Markus H. and Dotterweich, C. and Hartmann, J{\"u}rgen and Harrer, S. and Hemberger, F. and Ebert, Hans-Peter and Schnitzler, Tim}, title = {Phase Change Materials for Use in Thermally and Electrically Stressed Insulation for High Voltage Applications}, series = {IEEE Electrical Insulation Conference}, volume = {2016}, booktitle = {IEEE Electrical Insulation Conference}, pages = {605 -- 608}, language = {en} } @inproceedings{HarrerDotterweichHartmannetal., author = {Harrer, S. and Dotterweich, C. and Hartmann, J{\"u}rgen and Zink, M. and Schnitzler, Tim and Ebert, Hans-Peter and Hemberger, Frank}, title = {Paraffine als Phasenwechselmaterialen in der elektrischen Isolierung von Hochspannungsbauteilen}, language = {de} } @inproceedings{HartmannHarrerDotterweichetal., author = {Hartmann, J{\"u}rgen and Harrer, S. and Dotterweich, C. and Zink, Markus H.}, title = {On the conduction process of dielectric liquids based on mineral oil}, address = {Buenos Aires (Argentinien)}, language = {en} } @article{HoefflinSauerSchiffleretal., author = {H{\"o}fflin, Dennis and Sauer, Christian and Schiffler, Andreas and Manara, Jochen and Hartmann, J{\"u}rgen}, title = {Pixelwise high-temperature calibration for in-situ temperature measuring in powder bed fusion of metal with laser beam}, series = {Heliyon}, volume = {10}, journal = {Heliyon}, number = {7}, publisher = {Elsevier BV}, issn = {2405-8440}, doi = {10.1016/j.heliyon.2024.e28989}, abstract = {High-temperature calibration methods in additive manufacturing involve the use of advanced techniques to accurately measure and control the temperature of the build material during the additive manufacturing process. Infrared cameras, blackbody radiation sources and non-linear optimization algorithms are used to correlate the temperature of the material with its emitted thermal radiation. This is essential for ensuring the quality and repeatability of the final product. This paper presents the calibration procedure of an imaging system for in-situ measurement of absolute temperatures and temperature gradients during powder bed fusion of metal with laser beam (PBF-LB/M) in the temperature range of 500 K-1500 K. It describes the design of the optical setup to meet specific requirements in this application area as well as the procedure for accounting the various factors influencing the temperature measurement. These include camera-specific effects such as varying spectral sensitivities of the individual pixels of the sensor as well as influences of the exposure time and the exposed sensor area. Furthermore, influences caused by the complex optical path, such as inhomogeneous transmission properties of the galvanometer scanner as well as angle-dependent transmission properties of the f-theta lens were considered. A two-step fitting algorithm based on Planck's law of radiation was applied to best represent the correlation. With the presented procedure the calibrated thermography system provides the ability to measure absolute temperatures under real process conditions with high accuracy.}, language = {en} }