TY - CHAP A1 - Blotevogel, Thomas A1 - Hartmann, Matthias A1 - Rottengruber, Hermann A1 - Leipertz, Alfred ED - Leipertz, Alfred T1 - Laseroptisches Messverfahren zur Untersuchung von Gemischbildung und Verbrennung in Wasserstoffmotoren KW - Wasserstoff KW - Laseroptisches Messverfahren KW - Verbrennungsmotor KW - Gemischbildung Y1 - 2009 SN - 3931901599 PB - Esytec CY - Erlangen ER - TY - JOUR A1 - Höfflin, Dennis A1 - Sauer, Christian A1 - Schiffler, Andreas A1 - Hartmann, Jürgen T1 - Process Monitoring Using Synchronized Path Infrared Thermography in PBF-LB/M JF - Sensors N2 - 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. KW - SPIT KW - PBF-LB/M KW - additive manufacturing KW - process monitoring KW - SWIR KW - melt pool KW - galvanometer scanner Y1 - 2022 U6 - https://doi.org/10.3390/s22165943 VL - 22 IS - 16 PB - MDPI ER - TY - JOUR A1 - Ochs, Dennis A1 - Wehnert, Kira-Kristin A1 - Hartmann, Jürgen A1 - Schiffler, Andreas A1 - Schmitt, Jan T1 - Sustainable Aspects of a Metal Printing Process Chain with Laser Powder Bed Fusion (LPBF) JF - Procedia CIRP N2 - 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. Y1 - 2021 UR - 10.1016/j.procir.2021.01.163 VL - 98 SP - 613 EP - 618 PB - Elsevir ER - TY - JOUR A1 - Möbus, Helge A1 - Gerlinger, P. A1 - Brüggemann, D. T1 - Scalar and Joint Scalar-Velocity-Frequency Monte Carlo PDF Simulation of Supersonic Combustion JF - Combustion and Flame Y1 - 2003 UR - http://permalink.bibkatalog.de/BV012941361 VL - 132 SP - 3 EP - 24 ER - TY - JOUR A1 - Möbus, Helge A1 - Gerlinger, P. A1 - Brüggemann, D. T1 - Comparison of Eulerian and Lagrangian Monte Carlo PDF Methods for Turbulent Diffusion Flames JF - Combustion and Flame Y1 - 2001 UR - http://permalink.bibkatalog.de/BV012941361 VL - 124 SP - 519 EP - 534 ER - TY - JOUR A1 - Möbus, Helge A1 - Kaufmann, D. T1 - Koppelung von CFD und Prozess-Simulation zur industriellen Auslegung von Spaltöfen für Olefinanlagen JF - Chemie Ingenieur Technik Y1 - 2003 UR - http://permalink.bibkatalog.de/BV013522494 VL - 75 IS - 1-2 SP - 41 EP - 51 ER - TY - JOUR A1 - Möbus, Helge A1 - Gerlinger, P. A1 - Brüggemann, D. T1 - An Implicit Multigrid Scheme for Turbulent Combustion JF - Journal of Computational Physics Y1 - 2001 UR - http://permalink.bibkatalog.de/BV012478675 VL - 167 IS - 247 SP - 276 ER - TY - BOOK A1 - Möbus, Helge T1 - Euler- und Lagrange-Monte-Carlo-PDF-Simulation turbulenter Strömungs-, Mischungs- und Verbrennungsvorgänge T3 - Fortschritt-Berichte VDI, Reihe 7 - 414 Y1 - 2001 ER - TY - CHAP A1 - Paul, Gümpel T1 - Einfluss von Schleifparametern auf die Korrosionsbeständigkeit von metastabilen Austeniten am Beispiel des Werkstoffes 1.4301 (AISI 304) T2 - DGM-Werkstoffwoche KW - Rostfreier Stahl, Oberfläche, Korrosion, Schleifen Y1 - 2015 ER - TY - CHAP A1 - Wirth, Isabell A1 - Reumann, Andreas A1 - Zink, Markus H. A1 - Küchler, Andreas A1 - Langens, Achim A1 - Schnitzler, Tim T1 - Messung elektrischer und thermischer Transienten an Hochspannungsgleichstromdurchführungen T2 - Highvolt Kolloquium, Dresden, 2015 (Poster) Y1 - 2015 ER - TY - CHAP A1 - Sturm, Sebastian A1 - Wirth, Isabell A1 - Paulus, Johannes A1 - Zink, Markus H. A1 - Küchler, Andreas A1 - Berger, Frank T1 - Transient dielectric simulation in time domain with FEM in comparison with circuit models T2 - XIX International Symposium on Theoretical Electrical Engineering, Ilmenau, 2017 Y1 - 2017 ER - TY - JOUR A1 - Höfflin, Dennis A1 - Sauer, Christian A1 - Schiffler, Andreas A1 - Manara, Jochen A1 - Hartmann, Jürgen T1 - Pixelwise high-temperature calibration for in-situ temperature measuring in powder bed fusion of metal with laser beam JF - Heliyon N2 - 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. Y1 - 2024 U6 - https://doi.org/10.1016/j.heliyon.2024.e28989 SN - 2405-8440 VL - 10 IS - 7 PB - Elsevier BV ER - TY - CHAP A1 - Küchler, Andreas A1 - Wirth, Isabell A1 - Reumann, Andreas A1 - Zink, Markus H. A1 - Schnitzler, Tim A1 - Langens, Achim A1 - Berger, Frank T1 - Steady-state and Transient Electrical Potential Distributions in HVDC Bushings Measured under Different Thermal Conditions T2 - 19th International Symposium on High Voltage Engineering N2 - High voltage DC (HVDC) applications become more and more important and the voltage level for energy transportation increases steadily. Hence the design of the DC insulation systems becomes more and more difficult. The difference between HVDC and HVAC insulation systems is that in HVAC the electrical field is distributed according to the permittivities of the materials. Permittivity is only weakly dependent on temperature, so there is no significant difference between the electrical field distribution at room temperature and operating temperature of the insulation system. In HVDC however the electrical field is distributed according to the conductivities of the insulation materials whereas the conductivity is strongly dependent on temperature. This can lead to completely different field distributions at varying temperatures. The investigations presented here show simulation results of HVDC bushing cores in comparison with measurements on those test objects. Simulations and measurements were performed both for temperature distributions and electric potentials of the grading layers in the bushing at DC voltage. For the first time, it was shown by experiment that the FEM simulation can reproduce real DC field distributions very well. It was also shown, that there is a strong influence of temperature gradients or temperature transients on transient and steady-state electrical potential distribution inside the insulation. Y1 - 2015 CY - Pilsen, Czech Repbulic ER - TY - CHAP A1 - Michaelis, Thomas A1 - Marburg, Steffen A1 - Retka, Stefanie T1 - Application of the Transfer Path Analysis to Vehicle Doors T2 - INTER-NOISE and NOISE-CON Congress and Conference Proceedings, Glasgow N2 - Transfer path analysis (TPA) is a proven method for identifying critical structure-borne and airborne sound paths. The basic idea is to divide the overall system into an exciting active component (source) and a passive component, e.g. the mechanical structure to be investigated, with their respective measurement points. By separating them, two independent systems are created, whereby on one hand, the excitation behaviour can be characterised and on the other hand, the transmission behaviour can be assessed. Finally, both systems are validated by comparing them to each other and deciding whether changes to source or structure are required or not. The advantage is the simple description of the source as a black box without complex modelling. In this contribution, this systematic is applied to window regulator systems as they are found in vehicles. The focus is on a hybrid approach between experimental and numerical transfer path analysis. For this purpose, the basic workflow of suitable TPA methods is discussed. This includes the operational measurement of different exciting electric motors variants, the determination of the transfer functions of the structure, the calculation of the contact forces and the analysis of the individual transfer paths. Y1 - 2023 U6 - https://doi.org/10.3397/IN_2022_0551 VL - 265 IS - 4 SP - 3878 EP - 3885 PB - Institute of Noise Control Engineering ER - TY - CHAP A1 - Chacko, Jain A1 - Retka, Stefanie T1 - Genetic algorithm for the optimization of damping material T2 - INTER-NOISE and NOISE-CON Congress and Conference Proceedings, Glasgow N2 - A main research topic in acoustics is the reduction of indoor noise, which has increasingly received attention in recent years. A commonly used solution to solve these problems is reducing noise using damping structures, which absorb sound. This work aims at the numerical optimization of damping structures in interior problems, following three goals. First, the optimal damping structure for the required frequency range has to be determined. Second, the optimal position of the damping material has to be found. Third, we are focusing on lightweight design, which means that the amount of damping material used, has to be kept to a minimum. We present the implementation of a genetic algorithm into our open source code, which we use to optimize the damping behaviour and in consequence, the sound propagation for interior problems. We show an example of the application of this code. Y1 - 2023 U6 - https://doi.org/10.3397/IN_2022_0492 VL - 265 IS - 4 SP - 3456 EP - 3463 PB - Institute of Noise Control Engineering ER - TY - CHAP A1 - Celik, Ertac A1 - Riess, Julia A1 - Polster, Christian A1 - Helwich, Vadim A1 - Retka, Stefanie T1 - Entwicklung eines Versuchsstandes zur Geräuschuntersuchung am Fahrradkettentrieb T2 - Fortschritte in der Akustik – Plenarvorträge und Fachbeiträge der 49. Jahrestagung für Akustik, Hamburg Y1 - 2023 UR - https://pub.dega-akustik.de/DAGA_2023/data/articles/000286.pdf SP - 809 EP - 811 ER - TY - CHAP A1 - Michaelis, Thomas A1 - Marburg, Steffen A1 - Retka, Stefanie T1 - Dämpfungsidentifikation von Leichtbaustrukturen T2 - Fortschritte in der Akustik – Plenarvorträge und Fachbeiträge der 49. Jahrestagung für Akustik, Hamburg Y1 - 2023 UR - https://pub.dega-akustik.de/DAGA_2023/data/articles/000180.pdf SP - 1338 EP - 1341 ER - TY - CHAP A1 - Michaelis, Thomas A1 - Marburg, Steffen A1 - Retka, Stefanie T1 - Transferpfadanalyse von Fensterhebersystemen T2 - Fortschritte in der Akustik – Plenarvorträge und Fachbeiträge der 48. Jahrestagung für Akustik, Stuttgart Y1 - 2022 SP - 447 EP - 450 ER - TY - CHAP A1 - Michaelis, Thomas A1 - Retka, Stefanie T1 - Anwendung der parametrischen Modellordnungsreduktion in der Vibroakustik T2 - Fortschritte in der Akustik – Plenarvorträge und Fachbeiträge der 47. Jahrestagung für Akustik, Wien Y1 - 2021 SP - 892 EP - 895 ER - TY - CHAP A1 - Retka, Stefanie A1 - Celik, Ertac T1 - Entwicklung eines Praktikumsversuchs zur Luftschallmessung nach DIN T2 - Fortschritte in der Akustik – Plenarvorträge und Fachbeiträge der 48. Jahrestagung für Akustik, Stuttgart Y1 - 2022 SP - 679 EP - 681 ER - TY - JOUR A1 - Spescha, Daniel A1 - Weikert, Sascha A1 - Retka, Stefanie A1 - Wegener, Konrad T1 - Krylov and Modal Subspace based Model Order Reduction with A-Priori Error Estimation JF - ETH Zürich – Research Collection N2 - Versatile model order reduction techniques for the reduction of dynamic systems have been presented in the last decades. Krylov subspace based methods are considered as efficient in terms of computational effort and reduction order and can be used in order to match the transfer function locally. However, they lack of a simple and efficient automatisation and error estimation. On the other hand, modal reduction is popular because it leads to exactly matching eigenfrequencies. The static behaviour and the overall accuracy of the frequency response, though, are poor. In this paper, a combination of both methods is presented and discussed. In order to characterise a method for the reduction of mechanical models for the simulation of machine tools and similar mechatronic systems, first, the requirements on the model reduction method are derived. Criteria for the relative error of the frequency response function, the transmission zeros, and the poles are defined and the idea of defining a frequency range of interest is established. Subsequently, a combination of Krylov and modal subspaces for the reduction of dynamic systems with second-order structure and proportional damping is presented. It is shown that the combination of the bases of the two methods leads to a combination of the advantages and an elimination of the drawbacks of them both. Moreover, an estimation for the upper bound of the defined error criteria is developed and verified with numerical results. The result of this paper is an a priori parametrisable and numerically efficient model reduction method, which leads to reduced systems of low order with a definable error limit within a definable frequency range. Y1 - 2018 U6 - https://doi.org/10.3929/ethz-b-000284435 ER - TY - CHAP A1 - Hahn, Pascal A1 - Fleischer, Mario A1 - Retka, Stefanie T1 - Numerische Modellierung der Schallausbreitung im menschlichen Vokaltrakt T2 - Fortschritte in der Akustik – Plenarvorträge und Fachbeiträge der 46. Jahrestagung für Akustik, Hannover Y1 - 2020 SP - 708 EP - 711 ER - TY - CHAP A1 - Hahn, Pascal A1 - Retka, Stefanie T1 - Einfluss der absorbierenden akustischen Leistung auf die Eigenschaften von Resonanzfrequenzen T2 - Fortschritte in der Akustik – Plenarvorträge und Fachbeiträge der 47. Jahrestagung für Akustik, Wien Y1 - 2021 SP - 900 EP - 903 ER - TY - JOUR A1 - Blotevogel, Thomas A1 - Egermann, Jan A1 - Goldlücke, Jürgen A1 - Leipertz, Alfred A1 - Hartmann, Matthias A1 - Schenk, Martin A1 - Berckmueller, Martin T1 - Developing Planar Laser-Induced Fluorescence for the Investigation of the Mixture Formation Process in Hydrogen Engines JF - SAE Paper Y1 - 2004 UR - http://permalink.bibkatalog.de/BV013334911 IS - 2004-01-1408 ER - TY - CHAP A1 - Blotevogel, Thomas A1 - Goldlücke, Jürgen A1 - Egermann, Jan A1 - Leipertz, Alfred A1 - Hartmann, Matthias A1 - Rottengruber, Hermann ED - Eichlseder, Helmut T1 - Untersuchung der Gemischbildung von Gasmotoren mit Hilfe laseroptischer Messverfahren T2 - Der Arbeitsprozess des Verbrennungsmotors (10. Tagung) Y1 - 2005 SP - 139 EP - 166 PB - Verlag der Technischen Universität Graz CY - Graz ER -