@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} } @inproceedings{HartmannMachinBloembergenetal., author = {Hartmann, J{\"u}rgen and Machin, Graham and Bloembergen, P. and Anhalt, Klaus and Sadli, M. and Saunders, P. and Woolliams, E. and Yamada, Y. and Yoon, H.}, title = {Practical implementation of the mise-en-prtique for the definition of the Kelvin above the silver point}, address = {Portroz (Slowenien)}, language = {en} } @article{HartmannMachinBloembergenetal., author = {Hartmann, J{\"u}rgen and Machin, Graham and Bloembergen, P and Anhalt, Klaus and Sadli, M and Saunders, P and Wooliams, E and Yamada, Y and Yoon, H}, title = {Practical Implementation of the Mise en Pratique for the Definition of the Kelvin Above the Silver Point}, series = {International Journal of Thermophysics}, volume = {31}, journal = {International Journal of Thermophysics}, number = {8-9}, doi = {10.1007/s10765-010-0834-5}, pages = {1779 -- 1788}, abstract = {The "Mise en pratique for the definition of the kelvin" (MeP-K) was established in April 2006 to be the repository of information required to perform a "practical measurement of temperature in accordance with the International System of Units (SI)." This article describes the progress made by the MeP-K HT (High Temperature Task Group) of CCT-WG5 (radiation thermometry) in drawing together the appropriate methods for accessing thermodynamic temperature above the silver point involving direct radiometric measurements on the one hand and indirect extrapolation, interpolation, and least-squares fitting on the other. An examination of the uncertainties and a brief discussion of the advantages and disadvantages of the various approaches are given. A summary of the remaining issues to be resolved concludes the article.}, language = {en} } @article{HartmannKnoppShandyetal., author = {Hartmann, J{\"u}rgen and Knopp, Kevin and Shandy, Amir and Winterstein, Achim and Arduini, Mariacarla and Hemberger, Frank and Vidi, Stephan and Manara, Jochen and M{\"u}ller, Michael}, title = {Thermophysikalische Charakterisierung von W{\"a}rmed{\"a}mmschichten}, series = {tm - Technisches Messen}, volume = {88}, journal = {tm - Technisches Messen}, number = {12}, publisher = {Oldenbourg Wissenschaftsverlag}, doi = {10.1515/teme-2021-0074}, abstract = {Die Effizienzsteigerung moderner Gasturbinen erfordert die stetige Anhebung der Betriebstemperatur. Die derzeitigen Brenngastemperaturen liegen mit {\"u}ber 1400 °C signifikant {\"u}ber der kritischen Temperatur der verwendeten Turbinenst{\"a}hle. Zur Gew{\"a}hrleistung der Betriebssicherheit werden die Turbinenschaufeln neben Aktivk{\"u}hlung durch Beschichtung mit thermischen Schutzschichten, sogenannten thermal barrier coatings (TBC), gesch{\"u}tzt. Da es sich bei den TBC um Keramikschichten handelt, ist f{\"u}r die Erh{\"o}hung der Haftfestigkeit das Aufbringen eines Haftvermittlers (Verbindungsschicht) notwendig. Da die Eigenschaften d{\"u}nner Schichten stark von den Eigenschaften des Bulkmaterials abweichen k{\"o}nnen und zudem von der Herstellungsmethode beeinflusst werden, ist eine Untersuchung der thermischen und infrarot-optischen Eigenschaften der tats{\"a}chlichen Schichtstrukturen unumg{\"a}nglich, insbesondere im Hochtemperaturbereich. Hierf{\"u}r wurden Proben des reinen Tr{\"a}gerstahls, des Tr{\"a}gerstahls mit Haftvermittlerschicht und des kompletten Schichtsystems aus Tr{\"a}gerstahl, Haftvermittlerschicht und W{\"a}rmed{\"a}mmschicht verschiedener Dicken hergestellt und mittels Laser-Flash-Methode untersucht. Die Auswertung erfolgte dabei analytisch, ausgehend von der Tr{\"a}gerstahl-Einschichtprobe, {\"u}ber die Zweischicht- und Dreischichtsysteme. Vervollst{\"a}ndigt wurden diese Untersuchungen durch infrarot-optische Charakterisierungen, mit denen sich die W{\"a}rmeausbreitung durch die Schichtsysteme beschreiben l{\"a}sst. Zusammen mit den Laser-Flash Messungen erlaubt dies eine sp{\"a}tere Quantifizierung der einzelnen, bei Keramiken auftretenden, W{\"a}rmetransportmechanismen.}, language = {de} } @inproceedings{HartmannDzemkoEngelmannetal., author = {Hartmann, J{\"u}rgen and Dzemko, Mikita and Engelmann, Bastian and Schmitt, Jan}, title = {Toward Shifted Production Strategies Through Additive Manufacturing: A Technology and Market Review for Changing Value Chains}, series = {7th CIRP Global Web Conference (86)}, volume = {86}, booktitle = {7th CIRP Global Web Conference (86)}, doi = {10.1016/j.procir.2020.01.029}, pages = {228 -- 233}, abstract = {In the last decade many different additive manufacturing (AM) technologies for metal, plastic or ceramic processing raise from research to commercialization. As a result, AM grows into different business areas and transforms structures and processes. Hence, the contribution tends to show the change in added values though the availability of different additive manufacturing technologies based on a technology screening and market research. Regarding the named purpose, a broad market research of 83 companies and 339 printer models has been conducted to find patterns of AM technology market share and regions to structure indicators such as accuracy by processed material classes with a specified AM method. Printing materials as metal, plastic, ceramic and carbon have been considered. The categorization is done by the AM principles: power bed fusion, material extrusion, vat photopolymerization and …}, 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{OchsWehnertHartmannetal., author = {Ochs, Dennis and Wehnert, Kira-Kristin and Hartmann, J{\"u}rgen and Schiffler, Andreas and Schmitt, Jan}, title = {Sustainable Aspects of a Metal Printing Process Chain with Laser Powder Bed Fusion (LPBF)}, series = {Procedia CIRP}, volume = {98}, journal = {Procedia CIRP}, publisher = {Elsevir}, pages = {613 -- 618}, abstract = {Production companies are getting more and more aware of the relevancy of energy costs and the environmental impact of their manufactured products. Hence, the knowledge about the energy intensity of new process technologies as metal printing becomes increasingly crucial. Therefore, data about the energy intensity of entire process chains allow a detailed assessment of the life cycle costs and environmental impact of metal printed parts. As metal printing with Laser Powder Bed Fusion (LPBF) is applied from rapid prototyping to serial manufacturing processes more and more, sustainability data are useful to support a valid scale-up scenario and energetic improvements of the 3D-printing machinery as well as peripheral aggregates used in the process chain. The contribution aims to increase the transparency of the LPBF process chain in terms of its energy consumption. Therefore a generalized model to assess sustainability aspects of metal printed parts is derived. For this purpose, the LPBF process chain with the essential pre-, main- and post-processes is evaluated regarding its energy intensity. Here, the sub-processes, for example wet and dry cleaning of the printer, sieving of the metal powder or sand-blasting of the part are analyzed as well as the main printing process. Based on the derived experimental data from an installed, industry-like process chain, a model is created, which tends to generalize the experimental findings to evaluate other metal printed parts and process chain variants in terms of their energy intensity.}, language = {en} } @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} }