@incollection{GruegerFischerKorbetal., author = {Gr{\"u}ger, Lennart and Fischer, Tim Sebastian and Korb, Elisa and H{\"a}rtel, Sebastian}, title = {Vergleichende Prozesskettenuntersuchung der konventionellen und additiven Fertigung eines Demonstratorbauteils unter umwelttechnischen Aspekten}, series = {Rethinking Quality - Wandel des Qualit{\"a}tsmanagements durch Digitalisierung und K{\"u}nstliche Intelligenz : Bericht zur GQW-Jahrestagung 2024 in Berlin}, booktitle = {Rethinking Quality - Wandel des Qualit{\"a}tsmanagements durch Digitalisierung und K{\"u}nstliche Intelligenz : Bericht zur GQW-Jahrestagung 2024 in Berlin}, editor = {Jochem, Roland and Maurice, Meyer}, publisher = {Springer Fachmedien Wiesbaden}, address = {Wiesbaden}, isbn = {978-3-658-47212-2}, doi = {https://doi.org/10.1007/978-3-658-47213-9_7}, pages = {123 -- 142}, abstract = {Nachhaltigkeit ist branchen{\"u}bergreifend ein relevantes Thema. H{\"a}ufig werden zu umwelttechnischen Untersuchungen jedoch nur einzelne Schritte der Fertigung eines Produktes und nicht die gesamte Prozesskette betrachtet. Der vorliegende Artikel liefert einen Vergleich von konventionellen und additiven Fertigungsverfahren anhand eines Demonstratorbauteils unter umwelttechnischen Gesichtspunkten. Zu diesem Zweck werden die Wertsch{\"o}pfungsketten der additiven Fertigungsverfahren des Laser Powder Bed Fusion und der Wire Arc Direct Energy Deposition mit einer konventionellen Fertigungsprozesskette verglichen. Hierbei kommen Energieverbrauch, CO2-Ausstoß und Abfallaufkommen als wesentliche Vergleichskriterien zur Anwendung. Im Ergebnis sind die additiven Fertigungsverfahren f{\"u}r das Demonstratorbauteil, in Bezug auf die genannten Kriterien als nachhaltiger zu bewerten. Der Artikel erhebt keinen Anspruch auf vollst{\"a}ndige {\"U}bertragbarkeit, pr{\"a}sentiert jedoch einen Ansatz zur Analyse der Bauteilnachhaltigkeit {\"u}ber die gesamte Wertsch{\"o}pfungskette.}, language = {de} } @inproceedings{BambachImranBuhletal., author = {Bambach, Markus and Imran, Muhammad and Buhl, Johannes and H{\"a}rtel, Sebastian and Awiszus, Birgit}, title = {Towards intelligent materials testing with reduced experimental effort for hot forming}, series = {KomPlasTech 2017 : XXIV International Conference on Computer Methods in Materials Technology, January 15-18, 2017, Zakopane, Poland : book of abstracts}, booktitle = {KomPlasTech 2017 : XXIV International Conference on Computer Methods in Materials Technology, January 15-18, 2017, Zakopane, Poland : book of abstracts}, editor = {Szeliga, Danuta and Rauch, Łukasz}, publisher = {AKNET-PRess}, address = {Krakow}, isbn = {978-83-947091-0-5}, pages = {72 -- 73}, language = {en} } @misc{IsrarBuhlHaerteletal., author = {Israr, Rameez and Buhl, Johannes and H{\"a}rtel, Sebastian and Bambach, Markus}, title = {Reinforcement of Tooling Using Residual Stresses Generated by Cladding by Arc Welding}, series = {Metals}, volume = {12}, journal = {Metals}, number = {6}, issn = {2075-4701}, doi = {10.3390/met12060984}, pages = {30}, abstract = {Cladding is typically used to protect components from wear and corrosion while also improving the aesthetic value and reliability of the substrate. The cladding process induces significant residual stresses due to the temperature difference between the substrate and the clad layer. However, these residual stresses could be effectively utilized by modifying processes and geometrical parameters. This paper introduces a novel methodology for using the weld-cladding process as a cost-effective alternative to various existing reinforcement techniques. The numerical analyses are performed to maximize the reinforcement of a cylindrical tool. The investigation of how the weld cladding develops compressive stresses on the specimen in response to a change in the weld beads and the welding sequence is presented. For the benchmark shape, experimental verification of the numerical model is performed. The influence of the distance between the weld beads and the effect of the tool diameter is numerically investigated. Furthermore, the variation in compressive stresses due to temperature fluctuations during the extrusion process has been evaluated. The results showed that adequate compressive stresses are generated on the welded parts through the cladding process after cooling. More compressive stresses are induced in the tool as the cross-section of the weld bead is increased. Furthermore, keeping a gap between the adjacent beads improves tool reinforcement. Hence, the targeted reinforcement of the substrate can be achieved by optimizing the welding sequence and process parameters.}, language = {en} } @misc{HaaseWernerKraeuseletal., author = {Haase, R. and Werner, M. and Kr{\"a}usel, V. and Alimov, Artem and Sviridov, Alexander and H{\"a}rtel, Sebastian}, title = {Improved formability of HMGF components by preforming in an upset bulging process}, series = {IOP Conference Series}, volume = {1238}, journal = {IOP Conference Series}, publisher = {IOP Publishing Ltd.}, address = {Bristol}, doi = {10.1088/1757-899X/1238/1/012018}, pages = {8}, language = {en} } @misc{SydowJhanjiHaelsigetal., author = {Sydow, Benjamin and Jhanji, Avantika and H{\"a}lsig, Andr{\´e} and Buhl, Johannes and H{\"a}rtel, Sebastian}, title = {The Benefit of the Process Combination of Wire Arc Additive Manufacturing (WAAM) and Forming—A Numerical and Experimental Study}, series = {Metals}, volume = {12}, journal = {Metals}, number = {6}, issn = {2075-4701}, doi = {10.3390/met12060988}, pages = {13}, language = {en} } @misc{ErtugrulHaelsigHenseletal., author = {Ertugrul, G{\"o}khan and H{\"a}lsig, Andre and Hensel, Jonas and Buhl, Johannes and H{\"a}rtel, Sebastian}, title = {Efficient Multi-Material and High Deposition Coating including Additive Manufacturing by Tandem Plasma Transferred Arc Welding for Functionally Graded Structures}, series = {Metals}, volume = {12}, journal = {Metals}, number = {8}, issn = {2075-4701}, doi = {10.3390/met12081336}, pages = {1 -- 17}, language = {en} } @misc{ScharfWildenhainHaelsigHaerteletal., author = {Scharf-Wildenhain, Ronny and H{\"a}lsig, Andr{\´e} and H{\"a}rtel, Sebastian and Wandtke, Karsten and Schr{\"o}pfer, Dirk and Kromm, Arne and Kannengießer, Thomas}, title = {Einfluss der W{\"a}rmef{\"u}hrung auf die Eigenschaften und fertigungsbedingten Beanspruchungen additiv geschweißter hochfester Feinkornbaust{\"a}hle}, series = {42. Assistentenseminar F{\"u}getechnik}, journal = {42. Assistentenseminar F{\"u}getechnik}, publisher = {DVS Media GmbH}, address = {D{\"u}sseldorf}, isbn = {978-3-96144-210-2}, pages = {94 -- 101}, language = {de} } @misc{ColditzHaertelDrehmann, author = {Colditz, Pascal and H{\"a}rtel, Sebastian and Drehmann, Rico}, title = {Numerical and Experimental Modeling of an Inline Forming Process for the Mechanical Property Optimization of Cold Gas Sprayed Material Composites}, series = {Production at the Leading Edge of Technology : Proceedings of the 11th Congress of the German Academic Association for Production Technology (WGP), Dresden, September 2021}, journal = {Production at the Leading Edge of Technology : Proceedings of the 11th Congress of the German Academic Association for Production Technology (WGP), Dresden, September 2021}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-78423-2}, issn = {2194-0533}, doi = {10.1007/978-3-030-78424-9_41}, pages = {366 -- 374}, language = {en} } @misc{HartRawungBuhlHaerteletal., author = {Hart-Rawung, Thawin and Buhl, Johannes and H{\"a}rtel, Sebastian and Bambach, Markus}, title = {Intelligent Iterative Experimental Design to Achieve Maximum Model Quality for Phase Change of 22MnB5}, series = {Key Engineering Materials}, volume = {926}, journal = {Key Engineering Materials}, publisher = {Verlag Trans Tech Publications Ltd}, doi = {https://doi.org/10.4028/p-0cnty5}, pages = {2031 -- 2039}, language = {en} } @misc{BesongBuhlHaerteletal., author = {Besong, Lemopi Isidore and Buhl, Johannes and H{\"a}rtel, Sebastian and Bambach, Markus}, title = {Increasing the Forming Limits in Hole Flanging of Dual-Phase (DP) 1000 Steel Using Punch Rotation}, series = {Key Engineering Materials}, volume = {Vol. 926}, journal = {Key Engineering Materials}, issn = {1662-9795}, doi = {10.4028/p-06y8un}, pages = {717 -- 723}, language = {en} } @misc{ErtugrulAlimovSviridovetal., author = {Ertugrul, G{\"o}khan and Alimov, Artem and Sviridov, Alexander and H{\"a}rtel, Sebastian}, title = {Machine learning application for optimization of laser directed energy deposition process for aerospace component rapid prototyping in additive manufacturing}, series = {Materials Research Proceedings}, volume = {41}, journal = {Materials Research Proceedings}, publisher = {Taylor\&Francis}, issn = {2474-395X}, doi = {10.21741/9781644903131-31}, pages = {271 -- 282}, abstract = {Abstract. The paper proposes a methodology for determining the optimal L-DED parameters based on the minimum number planned of L-DED trials. A dataset compiled from planned L-DED experiments was used to train a machine learning model. The algorithm demonstrated a robust ability to predict the output metrics with notable accuracy and proposed a theoretical framework that modeled the complex relationships between the input variables and the resulting critical welding properties for AM. The application of the developed model and its comparison with conventional methods thus offers a methodical approach to determining the optimum process parameters in advance. This is a step towards the development and production of additively manufactured components for future digital twin application in the aerospace industry.}, language = {en} } @misc{SchmidtEmdadiHaertel, author = {Schmidt, Alexander and Emdadi, Aliakbar and H{\"a}rtel, Sebastian}, title = {A holistic approach for near-net-shape processing of iron aluminides by means of Laser Directed Energy Deposition with cored wires}, series = {77th IIW Annual assembly and international conference on welding and joining, 7-12 July 2024, Rhodes}, volume = {2024}, journal = {77th IIW Annual assembly and international conference on welding and joining, 7-12 July 2024, Rhodes}, pages = {6}, abstract = {Iron aluminides are characterized by high corrosion resistance, excellent mechanical properties and dimensional stability at high temperatures. With a low density this material offers technological and economic advantages over Ni-based alloys in the aerospace sector. Because of the excellent mechanical properties machining is the current challenge in processing Fe-Al. Due to the possibility of near-net-shape manufacturing along with high material efficiency additive manufacturing processes such as L-DED with wires seem to be predestined for the processing of Fe-Al. In this paper, a holistic approach for processing Fe-Al including manufacturing of wires and the actual processing of the wires is described. Since the wire drawing of iron aluminides is not possible due to low forming characteristics, a rotary swaging process was applied for manufacturing cored wires with a steel shell and aluminum core. On the one hand, the usage of unalloyed raw materials with suitable forming properties are advantageous. On the other hand, cored wires require in-situ alloying of the steel shell and aluminum core during the application process. Thus, the weldability of such cored wires was investigated in preliminary tests, initially using a tungsten inert gas welding process. The wires and the welding results were characterized by scanning electron microscopy, hardness measurement, and X-ray analyses.}, language = {en} } @misc{JenschEissingRichardetal., author = {Jensch, Felix and Eissing, Katharina and Richard, Williams and Trautmann, Marcus and Yang, Yitong and Dubinin, Sergej and H{\"a}rtel, Sebastian}, title = {Improving the structural integrity of challenging to manufacture LPBF components with toolpath correction}, series = {Materials Research Proceedings}, volume = {41}, journal = {Materials Research Proceedings}, publisher = {Materials Research Forum LLC}, issn = {2474-395X}, doi = {10.21741/9781644903131-12}, pages = {110 -- 119}, abstract = {This work deals with the influence of optimised exposure strategies on the distortion and microstructure of components susceptible to overheating and warpage. Therefore, different distortion-prone specimen geometries of 316L were fabricated with the standard parameters, as well as with exposure strategies optimised by machine learning, which were generated using the AMAIZE software package. The manufactured samples were analysed with regard to distortion. The results of the distortion analysis were then linked with the results of the digital tomography from AMAIZE. Furthermore, components were manufactured that tend to overheat due to their geometry and orientation on the substrate plate. The influence of overheating during the LPBF process on the microstructure and porosity was investigated along the build-up direction by means of an EBSD analysis and a porosity analysis. With the presented approach for optimising the exposure strategy with AMAIZE, it could be shown that a successful production of distortion- prone components with a porosity of less than 1 \% is possible in the first trial.}, language = {en} } @misc{GruegerJenschDittrichetal., author = {Gr{\"u}ger, Lennart and Jensch, Felix and Dittrich, Fabian and H{\"a}rtel, Sebastian}, title = {On the creation of a material bond between L-PBF-manufactured AZ91 and Ti-6Al-4V components in the context of medical applications}, series = {Materials}, volume = {17}, journal = {Materials}, number = {18}, publisher = {MDPI AG}, issn = {1996-1944}, doi = {10.3390/ma17184667}, abstract = {Within the scope of these investigations, the feasibility of a material bond between Ti-6Al-4V and the magnesium alloy AZ91 is analyzed. Ti-6Al-4V is frequently used for implants due to its biocompatibility, corrosion resistance, and specific strength. However, depending on the surface quality, the attachment behavior of the bone to the implant varies. Magnesium implants promote the regeneration of bone tissue and biodegrade as the bone tissue heals. Combining the properties of both materials in one implant enables a reduced implant volume and increased stability. For this reason, this study aims to demonstrate the feasibility of creating a material bond between the materials Ti-6Al-4V and AZ91. For this purpose, Ti-6Al-4V truncated cones and AZ91 sleeves were produced using the additive manufacturing process of laser powder bed fusion (L-PBF). The as-built sleeves were then pressed onto machined truncated cones. Since zinc serves as a lubricant and has good diffusion properties with the materials used as a result of heat treatment, a comparison was made between zinc-coated and the as-built Ti-6Al-4V samples. This showed that a bond was created after hot isostatic pressing and that the push-out force could be increased by more than 4.5 times. Consequently, a proof of feasibility was demonstrated, and a high potential for applications in medical technology was shown.}, language = {en} } @misc{ApelHaertelSzyndler, author = {Apel, Markus and H{\"a}rtel, Sebastian and Szyndler, Joanna}, title = {Prediction of the microstructure morphology after the WAAM process based on the FEM simulation results}, series = {Materials Research Proceedings}, volume = {41}, journal = {Materials Research Proceedings}, doi = {10.21741/9781644903131-3}, pages = {22 -- 31}, abstract = {To improve understanding of the material behavior of additive-produced components, this paper focuses on the development of a numerical model that reproduces a Wire Arc Additive Manufacturing (WAAM) process, with particular attention given to the evolution of the microstructure. In this study, a finite element model in Simufact Welding software is developed, that replicates a real wire arc welding process of building a multilayer straight wall. Microscopy analysis of the weld wall cut in the middle of its length gave information about the expected microstructure morphology at different levels of the build wall. The whole experimental setup is reproduced in the software Simufact Welding. Simulation results in the form of temperature-time and temperature gradient-time history are then used as superimposed thermal conditions to simulate the microstructure evolution at different areas of the welded part by using MICRESS software.}, language = {en} } @misc{HaertelSzyndlerPakdelSefidietal., author = {H{\"a}rtel, Sebastian and Szyndler, Joanna and Pakdel Sefidi, Moein and J{\"a}ger, Reyk}, title = {Prediction of the evolution of material properties during the AM process based on the FEM simulation and experimental results}, series = {Materials Research Proceedings}, volume = {41}, journal = {Materials Research Proceedings}, doi = {10.21741/9781644903131-5}, pages = {40 -- 49}, abstract = {To deepen the understanding of material behavior after additive manufacturing, this article focuses on the prediction of material properties after the Wire Arc Additive Manufacturing (WAAM) process. Particular attention is put on the temperature curves in the various phases of the welding process, which influence the final material properties, especially the hardness of the resulting part. A total of nine components in the form of walls were produced using the WAAM process, with the number of layers varying from 1 to 9. By experimentally analyzing the welded parts, which were cut in the middle of their length, it was possible to gain insights into the development of hardness at selected points. The entire test setup was simulated in the Simufact Welding FE-software. The simulation results in the form of temperature-time diagrams were then correlated with the real hardness measurements at the corresponding points. In this way, a model was developed that for the first time considers the development of hardness as a result of cooling after the welding process as well as the change in hardness as a result of reheating due to the application of additional layers.}, language = {en} } @misc{GruegerHaertelSahin, author = {Gr{\"u}ger, Lennart and H{\"a}rtel, Sebastian and Sahin, Emre}, title = {Simulierte Produktionsumgebung heute - Evaluation der numerischen Prozesssimulation des selektiven Laserschmelzens}, series = {Industry 4.0 Science}, volume = {2024}, journal = {Industry 4.0 Science}, number = {4}, publisher = {GITO mbH Verlag}, issn = {2942-6154}, doi = {10.30844/I4SD.24.4.70}, pages = {70 -- 77}, language = {de} } @misc{JenschBuhlLaueetal., author = {Jensch, Felix and Buhl, Johannes and Laue, Robert and H{\"a}rtel, Sebastian}, title = {Application of the plane-strain-compression-test to determine the local mechanical properties of LPBF-manufactured 316l components}, series = {Material Forming: The 26th International ESAFORM Conference on Material Forming, Krak{\´o}w, Poland, April 19-21, 2023}, volume = {28}, journal = {Material Forming: The 26th International ESAFORM Conference on Material Forming, Krak{\´o}w, Poland, April 19-21, 2023}, doi = {10.21741/9781644902479-17}, pages = {149 -- 149}, language = {en} } @misc{JedynakErtugrulNeumannetal., author = {Jedynak, Angelika and Ertugrul, G{\"o}khan and Neumann, Andreas and Pippig, Robert and H{\"a}rtel, Sebastian}, title = {Semi-finished powder of aluminum matrix composite for a direct energy deposition additive manufacturing}, series = {Material Forming: The 26th International ESAFORM Conference on Material Forming, Krak{\´o}w, Poland, April 19-21, 2023}, volume = {28}, journal = {Material Forming: The 26th International ESAFORM Conference on Material Forming, Krak{\´o}w, Poland, April 19-21, 2023}, doi = {10.21741/9781644902479-22}, pages = {199 -- 206}, language = {en} } @misc{SzyndlerSchmidtHaertel, author = {Szyndler, Joanna and Schmidt, Alexander and H{\"a}rtel, Sebastian}, title = {Determination of welding heat source parameters for fem simulation based on temperature history and real bead shape}, series = {Material Forming : The 26th International ESAFORM Conference on Material Forming, Krak{\´o}w, Poland, April 19-21, 2023}, journal = {Material Forming : The 26th International ESAFORM Conference on Material Forming, Krak{\´o}w, Poland, April 19-21, 2023}, edition = {28}, doi = {10.21741/9781644902479-18}, pages = {159 -- 168}, language = {en} } @misc{AlimovHaertelBuhletal., author = {Alimov, Artem and H{\"a}rtel, Sebastian and Buhl, Johannes and Gardill, Markus and Knaack, Marcus}, title = {Erfassung von Pressen­ver­formungen mit Radarsensoren}, series = {wt Werkstattstechnik}, volume = {113}, journal = {wt Werkstattstechnik}, number = {10}, issn = {1436-4980}, doi = {10.37544/1436-4980-2023-10-47}, pages = {425 -- 431}, language = {de} } @misc{SydowHaertel, author = {Sydow, Benjamin and H{\"a}rtel, Sebastian}, title = {Temperature Control During the Process Combination Welding and Rolling for Enabling Full Recrystallization with Homogenized Grain Size Distribution}, series = {Proceedings of the 14th International Conference on the Technology of Plasticity : current trends in the technology of plasticity, ICTP 2023, volume 1}, journal = {Proceedings of the 14th International Conference on the Technology of Plasticity : current trends in the technology of plasticity, ICTP 2023, volume 1}, editor = {Mocellin, Katia and Bouchard, Pierre-Olivier and Bigot, R{\´e}gis and Balan, Tudor}, publisher = {Springer}, address = {Cham}, isbn = {978-3-031-41022-2}, doi = {10.1007/978-3-031-41023-9_20}, pages = {192 -- 202}, abstract = {Welding with an electric arc is mainly used as a joining technology, where a high energy input is required locally for the joining process. Due to the heat input, the welded bead is characterized by a heat affected zone, that consists of an inhomogeneous microstructure of different phases and grain sizes. This leads to non-optimal mechanical properties. One way to improve the microstructure is to induce plastic deformation (e.g. by rolling), which can enable recrystallization mechanisms, that homogenize the microstructure and therefore can optimize the material properties. Yet, the recrystallization mechanisms require a minimum temperature to be activated. On one hand, the in-situ heat input during welding can be used for this in a process combination of welding and rolling but might not be enough, to reach or hold this recrystallization temperature during rolling. An excessive heat input on the other hand leads to too high temperatures, causing significant grain growth, that also negatively affect the mechanical properties. In any case, a certain temperature range over time has to be maintained. The temperature can be controlled by burners for pre-heating and post-heating, and the heating power can be controlled separately. In this numerical study, burner heat models are used to simulate the temperature-controlled process combination of welding one single bead with a subsequent rolling step for the mild steel St37/S235JR. The influence of the pre- and post-heating could be numerically proven and suitable heating combinations were found, that allow a full recrystallization with a nearly homogenous grain size distribution.}, language = {en} } @techreport{BehrensKrimmFriesetal., author = {Behrens, Bernd-Arno and Krimm, Richard and Fries, Stefan and H{\"a}rtel, Sebastian and Schmidt, Alexander}, title = {Eigenschaften individuell gefertigter Bauteile f{\"u}r Umformanlagen}, address = {Hannover}, isbn = {978-3-86776-660-9}, pages = {103, XXI}, abstract = {Die Dauerschwingfestigkeit ist eine wichtige sowie f{\"u}r die Auslegung von zyklisch belasteten Bauteilen in Umformmaschinen notwendige Materialkenngr{\"o}ße. Diese Kenngr{\"o}ße ist nicht nur material- sondern auch fertigungsprozessabh{\"a}ngig. Aufgrund der rapiden Entwicklung von additiven Fertigungsanlagen und Werkstoffen mangelt es an hinreichenden Erfahrungswerten zu den Betriebseigenschaften von additiv gefertigten Bauteilen. Daher ist es wichtig, die Eignung von additiv gefertigten Bauteilen f{\"u}r Umformmaschinen im Vorfeld technologisch und wissenschaftlich zu untersuchen. Die Ermittlung der Dauerschwingfestigkeit von additiv gefertigten Komponenten f{\"u}r Umformmaschinen liefert außerdem einen Mehrwert f{\"u}r die konstruktive Auslegung anderer AM-Bauteile mit einem vergleichbaren Belastungskollektiv und erm{\"o}glicht eine Topologieoptimierung von Komponenten von Umformmaschinen. Im Rahmen dieses Forschungsvorhabens wurde die Dauerschwingfestigkeit additiv gefertigter Bauteile in Abh{\"a}ngigkeit von der Gesamtheit der Herstellungsparameter eines WAAM-Prozesses sowie diverser Nachbehandlungsmethoden erfolgreich anhand des Fallbeispiels Pleuel ermittelt. Außerdem wurde die Anwendbarkeit von WAAM-Prozessen zur Herstellung von individuellen Anlagenbauteilen f{\"u}r den Bereich Umformmaschinen erfolgreich belegt. Mit den ermittelten Dauerschwingfestigkeitswerten konnte eine Grundlage zur Auslegung weiterer AM-Bauteile mit vergleichbaren Belastungskollektiv sowie Topologieoptimierung genannter Bauteile geschaffen werden. Die Untersuchungen erfolgten an Laborproben geeigneter Geometrie in Bezug auf das Realbauteil und unter Gew{\"a}hrleistung der thermischen {\"U}bertragbarkeit auf Realbauteile. Abschließend ist mittels eines skalierten Demonstratorbauteils die Machbarkeit nachgewiesen worden.}, language = {de} } @misc{SchmidtJenschHaertel, author = {Schmidt, Alexander and Jensch, Felix and H{\"a}rtel, Sebastian}, title = {Multi-material additive manufacturing-functionally graded materials by means of laser remelting during laser powder bed fusion}, series = {Frontiers of Mechanical Engineering}, volume = {18}, journal = {Frontiers of Mechanical Engineering}, number = {4}, issn = {2095-0233}, doi = {10.1007/s11465-023-0765-z}, pages = {1 -- 11}, abstract = {Many processes may be used for manufacturing functionally graded materials. Among them, additive manufacturing seems to be predestined due to near-net shape manufacturing of complex geometries combined with the possibility of applying different materials in one component. By adjusting the powder composition of the starting material layer by layer, a macroscopic and step-like gradient can be achieved. To further improve the step-like gradient, an enhancement of the in-situ mixing degree, which is limited according to the state of the art, is necessary. In this paper, a novel technique for an enhancement of the in-situ material mixing degree in the melt pool by applying laser remelting (LR) is described. The effect of layer-wise LR on the formation of the interface was investigated using pure copper and low-alloy steel in a laser powder bed fusion process. Subsequent cross-sectional selective electron microscopic analyses were carried out. By applying LR, the mixing degree was enhanced, and the reaction zone thickness between the materials was increased. Moreover, an additional copper and iron-based phase was formed in the interface, resulting in a smoother gradient of the chemical composition than the case without LR. The Marangoni convection flow and thermal diffusion are the driving forces for the observed effect.}, language = {en} } @misc{AlimovSviridovSydowetal., author = {Alimov, Artem and Sviridov, Alexander and Sydow, Benjamin and Jensch, Felix and H{\"a}rtel, Sebastian}, title = {Additive Manufacturing of Hot-Forming Dies Using Laser Powder Bed Fusion and Wire Arc Direct Energy Deposition Technologies}, series = {Metals}, volume = {13}, journal = {Metals}, number = {11}, issn = {2075-4701}, doi = {10.3390/met13111842}, abstract = {Additive technologies are now widely used for the production of complex precise parts and have high potential for the production of forming dies. In this work, hot-forming dies optimized for additive manufacturing were developed and produced with wire arc direct energy deposition (WA-DED) and laser powder bed fusion (L-PBF) technologies. The concept of lightweight hot-forming dies with a 2D-lattice structure was developed, which reduced the weight of each die by 56\%, from 14.2 kg to 6.1 kg, in production using L-PBF. Maraging/precipitation-hardened steel 17-4PH was used as an alternative to traditional hot-working steels with slightly lower mechanical properties and a much higher processability in the additive manufacturing process. The workability of the manufactured dies was confirmed by forging tests on an industrial screw press.}, language = {en} } @misc{JaegerSydowSchmidtetal., author = {J{\"a}ger, Reyk and Sydow, Benjamin and Schmidt, Alexander and Witt, Susanne and H{\"a}rtel, Sebastian}, title = {Design and Manufacturing of a Lightweight Press-Hardening Forming Tool by Wire Arc Additive Manufacturing}, series = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, Volume 3}, journal = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, Volume 3}, editor = {Mocellin, Katia}, publisher = {Springer}, isbn = {978-3-031-41340-7}, issn = {2195-4364}, doi = {10.1007/978-3-031-41341-4_25}, pages = {235 -- 246}, abstract = {Press-hardening is an important metal sheet manufacturing process to improve the metal sheet properties during forming with an inline quenching process. This requires higher cooling rates often obtained by cooling channels within the tools, that enable the formation of martensite for a high strength. The manufacturing of those forming tools with internal cooling channels is quite complex, time and material consuming and therefore expensive. Optimal cooling channel geometry cannot be realized by conventional machining operations, that limits cooling efficiency too. Wire Arc Additive Manufacturing (WAAM) is a layer-wise welding process, that allows the manufacturing of near net shapes and internal cooling channels. In contrast to conventional machining, manufacturing of a complex lightweight design forming tool can be realized by WAAM. This will further reduce the WAAM process time and material consumption. However, the lightweight design reduces on one hand the thermal mass and thus the capability of heat transfer, making cooling via the cooling channels more crucial. On the other hand, elastic tool deformation has to be as low as possible. In this study, a press-hardening forming tool made of S235JR is designed and manufactured by means of WAAM. FEM analysis are performed to optimize the design of the forming tool regarding lightweight aspects. Simple near net shapes of cooling channels are considered for a simplification of the WAAM process. The forming tool is mechanically tested to compare and evaluate the stiffness with the FEM analysis.}, language = {en} } @misc{NeumannHaertel, author = {Neumann, Andreas and H{\"a}rtel, Sebastian}, title = {Limitations of a new forming process for vault structured recuperator tubes}, series = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity ICTP 2023 - Volume 1}, journal = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity ICTP 2023 - Volume 1}, editor = {Mocellin, Katia}, edition = {1}, publisher = {Springer Nature}, address = {Cham, Schweiz}, isbn = {978-3-031-41022-2}, issn = {2195-4356}, doi = {10.1007/978-3-031-41023-9_58}, pages = {577 -- 583}, abstract = {Classic forming technologies can make a difference to a climate-neutral economy. This also applies to the production of innovative hydrogen coolers (recuperators). To improve the efficiency of hydrogen coolers, heat transfer and heat flux can be increased by tube structures made by pressing spherical elements on their surface. Hydrogen is passed through the tubes of the recuperators and the cooling medium flows across it (Figure 1a). The tube serves as an atmosphere separator. Structured tubes can increase the power den-sity with the same dimensions. Figure 1b shows a process for introducing the structure into the pipe using radially and symmetrically arranged tools. Sheet metal forming usually involves pressing with structural tools, bending into a tube, and longitudinally welding. However, producing small tube diameters in the range of one inch presents a technical challenge. The challenge considered in this paper is to develop a new structuring process while maintaining the structural integrity and wall thickness of the tubes. This study aims to determine the feasibility of a multi-stage vault structuring process for recuperator tubes us-ing heat-resistant semi-finished products.}, language = {en} } @misc{JhanjiSydowAdamsetal., author = {Jhanji, Avantika and Sydow, Benjamin and Adams, Tom-Eric and Habisch, Stefan and H{\"a}rtel, Sebastian}, title = {Influence of the Initial Microstructure on the Mechanical Behavior During Forming for Inline Manufacturing Process Routes}, series = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, ICTP 2023 - Volume 2}, journal = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, ICTP 2023 - Volume 2}, publisher = {Springer Nature Switzerland}, address = {Cham}, isbn = {978-3-031-40919-6}, issn = {2195-4356}, doi = {10.1007/978-3-031-40920-2_53}, pages = {513 -- 524}, abstract = {With a view of sustainability and the rising energy costs currently, manufacturing processes of metals are becoming increasingly focused on optimizing process parameters such as energy and time consumption. A conventional hot-forming process route currently involves casting an ingot, letting it cool down, and heating it up again for the hot-forming process (see Fig. 1a). In order to implement the combination of casting and forging, avoiding the reheating cycle and using less energy, by utilizing the casting heat (see Fig. 1b), a methodology was developed within the present work to quantify the influence of the resulting microstructure as a function of the cooling rate on the forming and recrystallization behavior (see Fig. 1c). For this purpose, AISI 301 austenitic stainless-steel cast samples with different cast cooling rates were generated. An in-situ high-temperature microscope is used to determine the holding time and the heating rate. Dilatometer tests are performed to characterize the interaction between initial microstructure and the flow curves to verify the determination method (see Fig. 1d). The aim was to demonstrate whether the microstructure evolution and mechanical behavior is affected by the initial microstructure. The flow curves and the post-forming microstructure show a higher degree of recrystallization in fast-cooled microstructure than slow-cooled microstructure. Hence, it was found that the initial microstructure and the associated temperature history does have an impact on the mechanical properties.}, language = {en} } @misc{GrafPippigLehnertetal., author = {Graf, Marcel and Pippig, Robert and Lehnert, Tim and Jedynak, Angelika and H{\"a}rtel, Sebastian}, title = {Aluminium-Matrix-Composites (AMC) for Hot Forged Components}, series = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, ICTP 2023 - Volume 1}, journal = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, ICTP 2023 - Volume 1}, editor = {Mocellin, Katia}, publisher = {Springer Nature Switzerland}, address = {Cham}, isbn = {978-3-031-41022-2}, issn = {2195-4356}, doi = {10.1007/978-3-031-41023-9_4}, pages = {36 -- 47}, abstract = {The development of new materials or material systems is always accompanied by the development of processing technologies suitable for the material. The reduction of process steps, the saving of material and the optimization of material properties are aims of forming processes. The basis for this is the comprehensive characterisation of the thermos-physical and thermos-mechanical technologically relevant material behaviour, taking into account the real process conditions. In the present work, the material-specific process limits were determined by means of experimental simulation and used in the numerical simulation in order, on the one hand, to identify the forming steps for optimizing the manufacturing conditions and, on the other hand, to be able to set the final material properties. It was essential to homogenize the casting microstructure for the forming processes and to adjust it to globulitical grains by solution annealing. The previously limited forming behaviour of the cast AlSi9Mg alloy with 20 vol.-\% SiC could be increased thus to forging-relevant plastic strains without occurring damages. Based on the comprehensive temperature-dependent material data, a one-step and resource-efficient manufacturing process for AMC materials by hot forming could be developed with the help of the FE software Simufact Forming and validated in reality under near-industrial conditions.}, language = {en} } @misc{BuhlHaertelBesong, author = {Buhl, Johannes and H{\"a}rtel, Sebastian and Besong, Lemopi Isidore}, title = {Temperature Control of the Two-Point Incremental Forming Process to Achieve Homogeneous Martensite Content Based on Finite Element Simulations}, series = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, ICTP 2023 - Volume 1}, journal = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, ICTP 2023 - Volume 1}, editor = {Mocellin, Katia}, publisher = {Springer}, address = {Cham}, isbn = {978-3-031-41022-2}, issn = {2195-4356}, doi = {10.1007/978-3-031-41023-9_74}, pages = {739 -- 747}, abstract = {Deformation-induced martensite has been observed in the incremental sheet forming of metastable austenitic stainless steels (MASS). The presence of martensite improves the characteristics of the springs. Martensite transformation usually occurs at low temperatures (<70 ℃). Depending on the tool speed, incremental forming of disk springs requires between 3 to 5 min. The forming time needs to be short to increase the process output in industrial settings. However, accelerating the process leads to high temperatures above the martensite transformation temperature that suppress martensite formation, necessitating temperature control during forming. It is suggested to enhance the martensite content of the blank by cooling during the forming operation. In this contribution, two-point incremental sheet forming is conducted to determine the influence of process temperature on the phase content of MASS disk springs. A temperature-dependent phase change material model that includes the strain rate effect is implemented in finite element (FE) simulations to predict the martensite content. FE simulations are performed to investigate the convection coefficients and cooling time leading to process temperatures below 70 ℃. The framework can be used to control and speed up the incremental forming of disk springs while maintaining a high martensite content.}, language = {en} } @misc{SzyndlerHaertelBambach, author = {Szyndler, Joanna and H{\"a}rtel, Sebastian and Bambach, Markus}, title = {Machine learning of the dynamics of strain hardening based on contact transformations}, series = {Journal of Intelligent Manufacturing}, volume = {2025}, journal = {Journal of Intelligent Manufacturing}, publisher = {Springer}, doi = {10.1007/s10845-025-02577-6}, pages = {22}, abstract = {Dislocation density-based models offer a physically grounded approach to modeling strain hardening in metal forming. Since these models are typically defined by Ordinary Differential Equations (ODEs), their accuracy is constrained by both, the model formulation and the parameter identification process. Machine Learning (ML) provides an alternative by allowing models to be constructed directly from experimental data, bypassing the accuracy limitations of explicitly defined models. However, applying ML to ODEs introduces the need for novel training techniques. This work presents a new approach for developing neural ODE models for flow curve description, utilizing a contact transformation to simplify the problem of learning an ODE into a learning a multivariate function.}, language = {en} } @misc{GruegerSzyndlerJenschetal., author = {Gr{\"u}ger, Lennart and Szyndler, Joanna and Jensch, Felix and H{\"a}rtel, Sebastian}, title = {Porosity analysis of L-PBF manufactured AZ91D components}, series = {Materials research proceedings}, volume = {54}, journal = {Materials research proceedings}, publisher = {Materials Research Forum LLC}, address = {Millersville, PA}, isbn = {978-1-64490-359-9}, issn = {2474-395X}, doi = {10.21741/9781644903599-22}, pages = {199 -- 208}, abstract = {Several materials for joint replacement parts approved in medical technology are being investigated. Magnesium alloys are very suitable for implants due to the similar strength properties between magnesium alloys and human bone. Therefore, the present work aims to examine the parameters for producing the magnesium alloy AZ91D. For this purpose, 16 samples were manufactured with varying laser power and exposure speed and examined using µCT analyses. As a result, densities between 99.56 and 95.21 percent were achieved. The samples with the lowest density were subjected to a HIP process to increase the relative density. However, a further µCT analysis revealed only minor positive effects of the HIP process. An analysis of the number and size of the pores indicates that the pores bonded together instead of being closed.}, language = {en} } @misc{SviridovAlimovJenschetal., author = {Sviridov, Alexander and Alimov, Artem and Jensch, Felix and Dubinin, Sergej and H{\"a}rtel, Sebastian}, title = {Influence of surface quality on performance of forging dies produced by additive manufacturing the role of post-processing in LPBF-manufactured X55 steel}, series = {Materials research proceedings}, volume = {54}, journal = {Materials research proceedings}, publisher = {Materials Research Forum LLC}, address = {Millersville, PA}, isbn = {978-1-64490-359-9}, issn = {2474-395X}, doi = {10.21741/9781644903599-27}, pages = {245 -- 253}, abstract = {Laser Powder Bed Fusion (LPBF) has become a key technology in additive manufacturing (AM), enabling the production of highly complex geometries and is increasingly applied in serial production. With the continuous expansion of processable materials, LPBF is now also being considered for the manufacturing of forging dies. However, LPBF application for tool steels such as H11 is limited by their susceptibility to hot cracking. Maraging steels like X55 present a promising alternative due to their superior resistance to such defects. A major advantage of this technology for forging dies lies in the potential elimination of extensive machining required to refine rough as-built surfaces, thereby streamlining and accelerating the production process. Achieving this goal requires systematic investigations into non-machining post-processing techniques for targeted surface modifications, along with a comprehensive evaluation of mechanical properties and surface integrity after post-processing. This study examines the influence of different post-processing methods on the surface quality, mechanical properties, and tribological behavior of LPBF-manufactured X55 (1.2709) specimens. To evaluate surface roughness and mechanical performance, slope specimens and tensile specimens were analyzed in different conditions: as-built, mechanically machined, sandblasted, and treated via Hirtisition®. Additionally, flat dies were produced and subjected to ring compression tests to determine friction factors under varying surface and lubrication conditions. The findings emphasize the crucial role of post-processing in optimizing the surface quality and functional performance of LPBF-manufactured forging tools, offering valuable insights for their further development.}, language = {en} } @misc{OkoloEissingWilliamsetal., author = {Okolo, Chukwuemeka and Eissing, Katharina and Williams, Richard and Jensch, Felix and Fergani, Omar and H{\"a}rtel, Sebastian}, title = {Investigation of the influence of AI-controlled process parameter adjustment on the mechanical properties of LBPF-manufactured parts}, series = {Materials research proceedings}, volume = {54}, journal = {Materials research proceedings}, publisher = {Materials Research Forum LLC}, address = {Millersville, PA}, isbn = {978-1-64490-359-9}, issn = {2474-395X}, doi = {10.21741/9781644903599-24}, pages = {218 -- 227}, abstract = {This study investigates the influence of machine learning (ML) based process parameter adjustments on the microstructure, relative density, and mechanical properties of laser powder bed fusion (LPBF)-manufactured components, focusing on AlSi10Mg and Ti6Al4V. The ML algorithm optimizes the thermal history by adjusting laser power and exposure time at the vector level, ensuring consistent cooling and solidification dynamics. Microscopy revealed a refined and homogeneous microstructure in the optimized AlSi10Mg samples, with reduced grain size (4.92 µm compared to 6.37 µm in non-optimized samples). Relative density analysis showed a significant improvement for optimized samples, achieving consistent values across top, middle, and bottom sections of the specimen. Hardness measurements confirmed the homogenized mechanical properties, with more uniform and elevated hardness values observed in optimized samples. This study demonstrates that ML-based process optimization minimizes defects like porosity and microcracks, enabling improved mechanical performance and efficient process qualification for LPBF-manufactured parts. The findings underline the potential of AI-driven solutions for addressing complex geometrical and thermal challenges in LPBF process.}, language = {en} } @misc{EmdadiJenschSzyndleretal., author = {Emdadi, Aliakbar and Jensch, Felix and Szyndler, Joanna and Huang, Hsuan-Po and H{\"a}rtel, Sebastian and Weiß, Sabine}, title = {Void closure behavior during hot forming of an Fe-Al alloy}, series = {Materials research proceedings}, volume = {54}, journal = {Materials research proceedings}, publisher = {IWA Publishing}, address = {Millersville, PA}, isbn = {978-1-64490-359-9}, issn = {2474-395X}, doi = {10.21741/9781644903599-99}, pages = {927 -- 935}, abstract = {Hot forging is a forming process that can be used as a post-processing treatment to close residual porosity and refine the microstructure of additively manufactured materials, resulting in improved mechanical properties. During hot forging, void closure occurs through plastic deformation resulting from a predominantly compressive stress state at elevated temperatures. In the present work, Fe-25Al-1.5Ta (at. \%) samples have been produced by laser powder bed fusion (LPBF) using a larger layer thickness and scan speed than commonly used to achieve a target porosity fraction of approximately 10\%. Full densification is attempted in the subsequent hot compression step at various height reduction ratios. The as-built LPBF samples contained 8-10\% voids. After deformation to true strains of 0.2, 0.4, and 0.6, the void fraction decreased significantly to approximately 4\%, 2.3\%, and 1.1\%, respectively. Hot compression resulted in the complete closure of large pores with a size range of 200-300 µm and a significant reduction in the size of small to medium pores. These results show potential for improving the productivity of the LPBF by speeding up the process by increasing layer thickness and scanning speed while maintaining a reasonable density. Full densification should be achieved by subsequent hot forging.}, language = {en} } @misc{ErtugrulEmdadiJedynaketal., author = {Ertugrul, G{\"o}khan and Emdadi, Aliakbar and Jedynak, Angelika and Weiß, Sabine and H{\"a}rtel, Sebastian}, title = {Hot forming behavior of tungsten carbide reinforced Ni-based superalloy 625 additively manufactured by laser directed energy deposition}, series = {Additive manufacturing letters}, volume = {13}, journal = {Additive manufacturing letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2772-3690}, doi = {10.1016/j.addlet.2025.100267}, pages = {1 -- 12}, abstract = {The demands of high-performance industries such as aerospace, automotive, tool manufacturing, oil, and gas industries are driving the innovation in high-performance materials and their production methods. This study explores the impact of hybrid manufacturing, specifically the effect of the addition of tungsten carbide (WC/W2C) via Laser-Directed Energy Deposition (L-DED), on the hot workability, hardness, and microstructure of nickel-based superalloy Inconel 625 (IN625). IN625 is known for its high temperature and high corrosion resistance, and tungsten carbide for its high wear resistance and grain refinement effect. The integration of WC/W2C particles into the IN625 matrix, in addition to the use of the hybrid approach of additive manufacturing followed by a hot-forming process, significantly influences the microstructure and mechanical behavior of the material. Thus, while incorporation of the WC/W2C can strengthen the material and extend the mechanical limitations, its full impact, including any potential usages, should be thoroughly evaluated for the intended application of the materials. To understand the effect of WC/W2C, additive manufacturing of IN625 both with and without WC/W2C and isothermal hot compression was carried out. The objective is to analyze the differences in microstructure and properties between L-DED manufactured IN625, and WC-reinforced IN625, and their hot-forming behavior, focusing on the effects of WC addition and post-deformation on microstructure and mechanical properties. This work represents the first investigation into the effect of WC/W2C hard particles on the hot-forming process of additively manufactured Ni-based metal matrix composites.}, language = {en} } @misc{ErtugrulEmdadiHaertel, author = {Ertugrul, G{\"o}khan and Emdadi, Aliakbar and H{\"a}rtel, Sebastian}, title = {Powder production and additive manufacturing of iron aluminide alloys using plasma ultrasonic atomization and laser-directed energy deposition}, series = {Additive manufacturing letters}, volume = {14}, journal = {Additive manufacturing letters}, editor = {MacDonald, Eric W.}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {2772-3690}, doi = {10.1016/j.addlet.2025.100313}, pages = {1 -- 9}, abstract = {With a combination of desirable properties such as low density, high specific yield strength, low material cost, and excellent oxidation and corrosion resistance, iron aluminide (Fe-Al) has shown considerable potential to be an alternative to high-alloy chromium steels, and in some cases even nickel-based superalloys, in high-temperature applications. Due to these features, it is especially suitable for the aerospace and automotive industries. Recent advancements indicate an increasing interest in Fe-Al within the additive manufacturing industry, particularly in directed energy deposition (DED) processes. Despite this progress, processing of Fe-Al materials using the laser directed energy deposition (L-DED) has not been sufficiently investigated. In this study, Fe-Al powder material was produced from a commercial Al rod encased in a commercial low alloy-steel tube by a plasma-based ultrasonic atomization eliminating the need to cast an alloy ingot in advance. Subsequently, the produced powder was used in a l-DED process to fabricate an additively manufactured sample. The sample was investigated in terms of mechanical property, microstructure, chemical composition, and phase structure by scanning electron microscope (SEM) / energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and microhardness analyses.}, language = {en} } @misc{ErtugrulEmdadiHaertel, author = {Ertugrul, G{\"o}khan and Emdadi, Aliakbar and H{\"a}rtel, Sebastian}, title = {Advancements in iron aluminide alloy processing : a comparative study with DED alternatives}, series = {Materials research proceedings}, volume = {54}, journal = {Materials research proceedings}, publisher = {Materials Research Forum LLC}, address = {Millersville, PA}, issn = {2474-395X}, doi = {10.21741/9781644903599-28}, pages = {254 -- 263}, abstract = {This article investigates the processing and characterization of iron aluminide lightweight alloy by plasma ultrasonic atomization and laser powder based directed energy deposition (DED-LB/p) and its comparison with other additive manufacturing alternatives. DED-LB/p provides precisely controllable process parameters, a wide range of feed materials supplied in powder form, a relatively high deposition rate and low heat input. These features favor the DED - LB/p process for novel materials such as iron aluminide. Thanks to a combination of desirable properties such as low density, high specific strength, low material cost, excellent oxidation resistance, and corrosion resistance, Fe-Al has established considerable potential to replace high-alloy chromium steels and, in some cases, even superalloys in high-temperature applications. In this study, Fe-Al alloy was first atomized into powder form from a commercial rod with core of aluminum and sleeve of a commercial low alloy-steel by plasma ultrasonic atomization. The resulting powder was then used for additive manufacturing with DED-LB/p in order to reduce cost and analyze the process chain. The results show that the use of powder produced by plasma ultrasonic atomization from commercial raw materials in the DED-LB/p process provides an effective combination for additive manufacturing of Fe-Al alloy and has some advantages over the alternative WAAM method.}, language = {en} } @misc{ErtugrulHaelsigRimpletal., author = {Ertugrul, G{\"o}khan and H{\"a}lsig, Andre and Rimpl, Robert and Hensel, Jonas and H{\"a}rtel, Sebastian}, title = {Artificial neural network based calibration of Goldak heat source parameters in tandem plasma transferred arc process using finite element analysis}, series = {The international journal of advanced manufacturing technology}, volume = {139}, journal = {The international journal of advanced manufacturing technology}, publisher = {Springer Nature}, address = {London}, issn = {0268-3768}, doi = {10.1007/s00170-025-15843-x}, pages = {2349 -- 2363}, abstract = {The paper proposes a novel approach for determining multiple heat source parameters to achieve the necessary accuracy in the numerical prediction for a parallel tandem plasma transferred arc process. An artificial neural network (ANN) approach as a supervised learning-based artificial intelligence (AI) was used to model the complex relationship between heat distribution and tandem/dual heat source parameters based on finite element analysis (FEA). This study presents the first ANN-assisted numerical simulation for multiple heat source optimization of the tandem plasma transferred arc process. The model demonstrated high accuracy in predicting and calibrating the tandem heat source parameters, based on systematic simulation trials of the tandem plasma transferred arc welding. The results of the tandem heat source determined by ANN-assisted FEA were verified using experimental data on melt pool size and substrate distortion. This verification considered metrics such as penetration width, penetration depth, melt pool length, melt pool half-width, and the absolute distortion (measured as the difference between minimum and maximum displacement), with relative errors of 7.0\%, 7.6\%, 0.4\%, 1.9\%, and 9.7\%, respectively.}, language = {en} } @misc{JiangKnaackMartinetal., author = {Jiang, Yuyao and Knaack, Marcus and Martin, Clas Aljoscha and Tost, Frank and Alimov, Artem and H{\"a}rtel, Sebastian and Gardill, Markus}, title = {A 120 GHz industrial radar sensor network for condition monitoring of a forging process}, series = {IEEE sensors journal}, journal = {IEEE sensors journal}, publisher = {IEEE}, address = {Piscataway, NJ}, issn = {1558-1748}, doi = {10.1109/JSEN.2025.3636060}, pages = {1 -- 10}, abstract = {Current trends in forging technology emphasize increased automation and a rising demand for high-precision components. Among the key factors influencing the forging quality are process parameters, which also serve as indispensable inputs for data-driven modeling. This necessitates the establishment of a stable and robust sensor network to enable high-quality process monitoring. This study investigates the implementation of a heterogeneous sensor network within an energy-bound forging press, integrating industrial 120 GHz radar sensors for comprehensive data collection. A complete radar signal processing chain is developed, encompassing signal acquisition, pre-processing, and state estimation of the press ram. The validation against conventional reference sensors confirms the reliability and accuracy of the radar-based measurements. The results demonstrate the feasibility of the radar employment in the complex forging environment.}, language = {en} } @misc{EmdadiYangSzyndleretal., author = {Emdadi, Aliakbar and Yang, Yitong and Szyndler, Joanna and Jensch, Felix and Ertugrul, G{\"o}khan and Tovar, Michael and H{\"a}rtel, Sebastian and Weiß, Sabine}, title = {Highly printable Fe₃Al intermetallic alloy}, series = {Metals : open access journal}, volume = {16}, journal = {Metals : open access journal}, number = {5}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/met16010005}, pages = {1 -- 15}, abstract = {Intermetallic Fe₃Al-based alloys reinforced with Laves-phase precipitates are emerging as potential replacements for conventional high-alloy steels and possibly polycrystalline Ni-based superalloys in structural applications up to 700 °C. Their impressive mechanical properties, however, are offset by limited fabricability and poor machinability due to their severe brittleness. High tool wear during finish-machining, which is still required for components such as turbine blades, remains a key barrier to their broader adoption. In contrast to conventional manufacturing routes, additive manufacturing offers a viable solution by enabling near-net-shape manufacturing of difficult-to-machine iron aluminides. In the present study, laser powder bed fusion was used to produce an Fe-25Al-1.5Ta intermetallic containing strengthening Laves-phase precipitates, and the porosity, microstructure and phase composition were characterized as a function of the process parameters. The results showed that preheating the build plate to 650 °C effectively suppressed delamination and macrocrack formation, even though noticeable cracking still occurred at the high scan speed of 1000 mm/s. X-ray tomography revealed that samples fabricated with a lower scan speed (500 mm/s) and a higher layer thickness (0.1 mm) contained larger, irregularly shaped pores, whereas specimens printed at the same volumetric energy density (40 J/mm3) but with different parameter sets exhibited smaller fractions of predominantly spherical pores. All samples contained mostly elongated grains that were either oriented close to <001> relative to the build direction or largely texture-free. X-ray diffraction confirmed the presence of Fe₃Al and C14-type (Fe, Al)₂Ta Laves phase in all samples. Hardness values fell within a narrow range (378-398 HV10), with only a slight reduction in the specimen exhibiting higher porosity.}, language = {en} } @misc{JenschSviridovDubininetal., author = {Jensch, Felix and Sviridov, Alexander and Dubinin, Sergej and Karabulut, Fatih and Weiß, Sabine and H{\"a}rtel, Sebastian}, title = {Parameter optimization for low-porosity Ti-6Al-4V parts produced using accelerated PBF-LB process}, series = {Progress in additive manufacturing}, journal = {Progress in additive manufacturing}, publisher = {Springer}, address = {Cham}, issn = {2363-9520}, doi = {10.1007/s40964-025-01510-w}, pages = {1 -- 17}, abstract = {In this study, the influence of various process parameters on the porosity of Ti-6Al-4V parts fabricated via Powder Bed Fusion - Laser Based (PBF-LB) is investigated. Three different layer thicknesses (30 μm, 60 μm, and 120 μm) were analyzed to define process windows enabling a build-rate acceleration while keeping the porosity below 0.1\%. Through iterative parameter refinement, the effects of laser power, scan speed and hatch distance were examined in terms of linear energy density (LED), energy transmission density (ETD) and volumetric energy density (VED), and their influence on the formation of process-related defects such as pores. Correlations between these energy metrics and pore formation types (keyhole vs. lack-of-fusion) are discussed. The results demonstrate that process acceleration by a factor of more than 3 is possible while maintaining high quality of the components in terms of internal porosity. In addition, an accelerated method for manufacturing components using the PBF-LB process is presented, in which components are manufactured at very high build-rates but with increased porosity and then brought to the target porosity of 0.1\% using the HIP process. This has made it possible to accelerate the build-rate in PBF-LB production by a further 32\%. Accounting for the additional time required for HIP, the HIP route is faster than using the accelerated, which achieves the target porosity in as-built condition, for parts larger than 1421 cm3.}, language = {en} }