@article{ErtugrulEmdadiHaertel2025, 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}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2772-3690}, doi = {10.1016/j.addlet.2025.100313}, year = {2025}, 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 hightemperature 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.}, subject = {Iron aluminides (Fe-Al); Laser directed energy deposition (L-DED); Plasma ultrasonic atomization; Powder; Intermetallic phase}, language = {en} } @phdthesis{BesongBesong2024, author = {Besong Besong, Lemopi Isidore}, title = {Development of novel hole-flanging processes}, doi = {10.26127/BTUOpen-6859}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-68597}, school = {BTU Cottbus - Senftenberg}, year = {2024}, abstract = {Flanges are essential elements in sheet metal parts, where they perform important functions such as increasing structural stiffness, serve as bearing seats and positioning aids. Currently, flanges are mainly formed by the conventional hole-flanging process, which uses dedicated dies and punches. The limitations of conventional hole-flanging include the high cost involved in die design and manufacture, poor accessibility to form flanges in some complicated dies, and low formability. High-speed tool rotation is introduced in hole-flanging processes to increase the process temperature and forming limit of hard-to-form materials. This is done using paddle-shaped tools and spherical punches in existing production lines. In addition, strategies are explored to enhance the geometrical accuracy in robot-based hole-flanging by single-point incremental forming (SPIF). This thesis investigates new hole-flanging process variants by using experiments and finite element (FE) analysis. Empirical material models are used to study the effects of the process parameters on flange shape, forming limits, process temperature, and forming mechanics. The process formability is highest in hole-flanging with punch rotation and reduces for paddle forming and hole-flanging by SPIF. The least formability is observed in conventional hole-flanging. High-speed tool rotation and tool feeds form flanges with high formability. Surface strain measurements of the flanges show that low-speed tool rotation combined with high tool feeds favor crack formation. Tensile tests revealed that the material's formability increases with temperature and strain rate. From FE analyses of the process variants, the deformation in hole-flanging was determined to be mainly because of membrane stretching and bending. Some shear was present in paddle forming and SPIF. Based on FE analyses and experiments, the temperature and strain rate are determined to be the main parameters that account for the difference in process formability. Hole-flanging by SPIF is conducted on a robot manipulator to enhance geometrical accuracy. New tool paths are explored to prevent flange conicity. A parametric study is conducted to determine the process's feasibility. The stiffness of a robot is compensated to achieve the target flange geometry.}, subject = {Bohrungsflanschen; Hole-flanging; Paddle forming; Robot incremental forming; Process development; Deformation analysis; Schaufelumformung; Inkrementelle Roboterumformung; Verformungsanalyse; Prozessentwicklung; Kragenziehen; Flansch; Prozessentwicklung ; Deformation; Blechumformen; Finite-Elemente-Methode}, language = {en} } @book{Hirtler2021, author = {Hirtler, Markus}, title = {Entwicklung einer hybriden Prozesskombination aus partiellem Schmieden und additiver Fertigung zur flexiblen Herstellung von Aluminiumbauteilen}, doi = {10.26127/BTUOpen-6006}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-60064}, publisher = {BTU Cottbus - Senftenberg}, year = {2021}, abstract = {Effiziente Fertigungssysteme sind wichtiger denn je, um die steigenden Klimaauflagen und die damit verbundenen Anforderungen an die Ressourceneffizienz erf{\"u}llen zu k{\"o}nnen. Klassische Fertigungsverfahren haben dabei den Nachteil, dass diese entweder mit einem hohen Ressourcenverbrauch verbunden sind oder Produktvarianten nicht wirtschaftlich herstellen k{\"o}nnen. Zwar k{\"o}nnen additive Fertigungsverfahren wie Selective Laser Melting (SLM), Wire Arc Additive Manufacturing (WAAM) oder Laserpulverauftragschweißen (LPA) durch ihre hohe Flexibilit{\"a}t dieses Problem teilweise beheben, aber bei großvolumigen Bauteilen oder gr{\"o}ßeren St{\"u}ckzahlen sind diese Verfahren mit langen Prozesszeiten verbunden und weisen damit eine geringe Produktivit{\"a}t auf. Dahingegen k{\"o}nnen hybride Fertigungsverfahren bestehend aus einer Kombination aus einem werkzeuggebundenen Prozess (z. B. Schmieden) und einem werkzeuglosen Verfahren (z. B. Auftragschweißen) eine effiziente L{\"o}sung darstellen. Die Herausforderungen sind dabei, die Wechselwirkungen der Fertigungsverfahren zu untersuchen und die Teilprozesse aufeinander abzustimmen. Ziel war es, die negativen Auswirkungen einer W{\"a}rmeeinbringung und deren Effekte auf die Mikrostruktur sowie die daraus resultierende H{\"a}rte und Festigkeit aufzuzeigen. Des Weiteren wurde die Prozessreihenfolge untersucht, mit der eine optimale Festigkeit erreicht werden kann. Anhand von Beispielen wurden anschließend Richtlinien und Strategien f{\"u}r das Hybridverfahren abgeleitet. So konnte gezeigt werden, dass durch das Hybridverfahren der Werkstoffeinsatz mit bis zu 53,2 \% gegen{\"u}ber der reinen Zerspanung gesenkt werden kann. Die Prozesszeit liegt mit 4,4 bzw. 2,4 h deutlich unter der eines rein additiven Prozesses, was auf eine konkurrenzf{\"a}hige Wirtschaftlichkeit hindeutet.}, subject = {Prozesskombination; Hybride Fertigung; Additive Fertigung; Partielles Schmieden; Ressourceneffizienz; Process combination; Hybrid manufacturing; Additive manufacturing; Partial forging; Resource efficiency; Rapid Prototyping ; Schmieden; Selektives Laserschmelzen; Partielles Schmieden; Prozesskombination}, language = {de} } @phdthesis{Deplanque2007, author = {D{\´e}planque, Sylvain}, title = {Lifetime prediction for solder die-attach in power applications by means of primary and secondary creep}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-4275}, school = {BTU Cottbus - Senftenberg}, year = {2007}, abstract = {The objective of this thesis was to accurately check and improve the models existing for eutectic solder alloys used in simulation tools. Creep deformation,which is the most important deformation mode of solders, of two solder alloys, the widely used eutectic SnPb and the environmentally friendly alternative solder alloy SnAgCu was tested. It was shown that it is necessary to model two different stages of this high temperature induced mechanism: To improve the current material definition, primary creep must be implemented in the FE-software in addition to the existing secondary creep models. This thesis shows how it is possible to test creep behaviour under cyclic loading conditions with a test specimen of novel design. So, primary creep was observed and reoccurs cyclically under such test conditions. Furthermore, steady state creep is also always observed. A Constitutive equation combining both primary and secondary creep was given and verified. This model was implemented in FE-code Ansys, and after performing different kinds of simulation, the necessity of simulating primary creep was demonstrated. In order to achieve reliability information by FE-simulation of solder die attach, the creep-fatigue behaviour with the mean of crack propagation must be modeled. Various kinds of chips on copper substrate (power-transistors) were thermally tested, and different methods were used to investigate crack propagation. These methods were scanning acoustic microscopy and microstructure analysis by optical microscopy. The influence of damage on thermal behaviour (i.e. the thermal resistance of the device) was also assessed. These results were compared with the simulation results in order to build a lifetime prediction model based on crack propagation analysis.}, subject = {Legierung; L{\"o}ten; Kriechen; Kriechen; L{\"o}tstelle; Rissfortschritt; Lebensdauer; Leistungselektronik; Creep; Solder joint; Crack propagation; Lifetime; Power electronic}, language = {en} } @phdthesis{Gammoul2012, author = {Gammoul, Abir}, title = {Entwicklung einer Umformtechnologie zur Herstellung endkonturnaher Slicermesser}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-27228}, school = {BTU Cottbus - Senftenberg}, year = {2012}, abstract = {Slicermesser sind kreisf{\"o}rmige Scheibenmesser zum Schneiden von Lebensmittelprodukten, insbesondere Wurst, Fleisch, K{\"a}se und dergleichen. Sie werden in Hochleistungsschneidemaschinen so genannten Slicern eingesetzt und mit hoher Drehzahl von 3450 bis 5600 min-1 angetrieben. Die hohen Drehzahlen und die auftretenden Schnittkr{\"a}fte erfordern eine sehr stabile Ausf{\"u}hrung des Slicermessers. Ausgehend davon, die Messer in aufw{\"a}ndigen spanenden Herstellungsverfahren gefertigt werden m{\"u}ssen und ein relativ hohes Gewicht von 5250 g aufweisen. Der Schl{\"u}ssel zur L{\"o}sung dieser Herausforderungen hinsichtlich Stabilit{\"a}t, Steifigkeit, Gewichtseinsparung, Werkstoffeinsatz und Fertigungsaufwand k{\"o}nnte in der endkonturnahen Fertigung durch Blechumformung liegen. In dieser Arbeit wurde ein werkstoffeffizientes, aus Stahlblech herstellbares Slicermesser entwickelt. Die Umformtechnologie zur Herstellung des Slicermessers wurde realisiert. Die Funktionsf{\"a}higkeit und die technische Zuverl{\"a}ssigkeit der hergestellten Slicermesser wurden experimentell {\"u}berpr{\"u}ft und mit dem herk{\"o}mmlichen Slicermesser verglichen.}, subject = {Messer; Blechumformen; Slicermesser; Blechbearbeitung; Biegesteifheit; Gewichtseinsparung; Slicer blades; Sheet metal forming; Rigidity; Weight saving}, language = {de} } @phdthesis{Simon2006, author = {Simon, Sylvio}, title = {Werkstoffgerechtes Konstruieren und Gestalten mit metallischen Werkstoffen}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-502}, school = {BTU Cottbus - Senftenberg}, year = {2006}, abstract = {Moderne Konstruktionen im Maschinen- und Fahrzeugbau werden oft aus Umwelt- und Kostengr{\"u}nden als Leichtbaukonstruktionen ausgef{\"u}hrt. Dabei spielen metallische Werkstoffe auf Grund ihres hohen Recyclingpotential und ihrer hervorragenden Verarbeitbarkeit trotz ihrer zum Teil recht hohen Dichte nach wie vor eine bedeutende Rolle. Neue Fertigungs- und F{\"u}geverfahren erm{\"o}gliche neuartige konstruktive L{\"o}sungen. Dabei kann zum Teil auf neue, metallische Halbzeuge zur{\"u}ckgegriffen werden. Die aktuelle Entwicklung der zur Fertigung von Blechen verwendeten St{\"a}hle, Aluminium- und Magnesiumlegierungen sowie ihre spezifischen Fertigungseigenschaften werden einleitend beschrieben. Es schließt sich eine Klassifizierung von Halbzeugen und Beschreibung der Fertigung der Halbzeuge an, die auf den Leichtbau ausgerichtet ist. Dabei werden Probleme, Grenzen und typische Fehlerm{\"o}glichkeiten bei der Herstellung der Halbzeuge beleuchtet. Die vorliegende Arbeit beschreibt die Entwicklung und Untersuchung neuer Halbzeuge. Beispielhaft sind hier die leichten Stahlrohre als Leichtbauprofile, ihre Vorformung durch Gleitziehen und ihre Ausformung durch einen geringen Wirkmediendruck genannt. Es werden verschiedene Fertigungsm{\"o}glichkeiten diskutiert. Sie eignen sich f{\"u}r Tragwerke und Rahmenstrukturen und stellen eine Kombination aus Rohrprofil und Biegetr{\"a}ger dar. Ein weiterer Schwerpunkt der Arbeit ist die Entwicklung des Verfahrens zur Herstellung von blechebenen Aluminium Stahl Tailored Blanks. Sie werden durch einen Kaltpressschweißvorgang bei gleichzeitiger Umformung durch Walzen hergestellt und weisen, anders als bei schmelzgeschweißten Tailored Blanks, keine interkristallinen Phasen auf. Damit eignen sie sich prinzipiell auch f{\"u}r Karosserieaußenteile. Den gr{\"o}ßten Umfang nehmen die strukturierten Feinbleche als neuartige Halbzeuge f{\"u}r den Konstruktionsprozeß ein. Ihr Materialverhalten wird ausf{\"u}hrlich dargestellt und unter Nutzung von FEM- Simulationen erl{\"a}utert. Die dazu entwickelten angepassten Pr{\"u}fverfahren werden vorgestellt. Sie unterscheiden sich erheblich von den Pr{\"u}fverfahren f{\"u}r glatte Bleche, die nur das Materialverhalten, nicht aber die Halbzeugeigenschaften wiedergeben. Die durchgef{\"u}hrte Zug-, Biege- und Torsionversuche zeigten eine starke Struktur- und Materialabh{\"a}ngigkeit. Die Ergebnisse der Untersuchungen zur mechanischen und wirkmedienbasierten Umformung werden vorgestellt und auf ihre Praxistauglichkeit {\"u}berpr{\"u}ft. Dabei werden Kennwerte f{\"u}r Werkzeuge und Strukturen f{\"u}r die Konstruktion bereitgestellt. Die f{\"u}r die Gestaltung von Bauteilen oft so wichtigen F{\"u}geverfahren des Klebens, Punktschweißens und Schraubens werden an strukturierten Feinblechen sowohl untereinander als auch mit glatten Feinblechen untersucht und dargestellt. Zusammenfassend werden die Vor- und Nachteile der neuen Halbzeugarten sowie weiterer Forschungsbedarf beschrieben. F{\"u}r jedes Halbzeug sind Konstruktions- und Gestaltungshinweise erarbeitet worden.}, subject = {Metallischer Werkstoff; Konstruktion; Gestaltung; Leichtbau; Kaltpressschweißen; Wirkmedienbasierte Umformverfahren; F{\"u}geverfahren; Punktschweißen; Lightweight construction; Cold pressure welding; Active medium forming (hydroforming); Joining technologies; Spot welding}, language = {de} } @phdthesis{Berding2016, author = {Berding, Jens}, title = {Entwicklung eines wandlungsf{\"a}higen Pressensystems mit Servospindelantrieb}, publisher = {Winter-Industries GmbH}, address = {Berlin}, isbn = {978-3-86624-633-1}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-41227}, school = {BTU Cottbus - Senftenberg}, year = {2016}, abstract = {Unternehmen der Umformtechnik sehen sich vermehrt steigenden Anforderungen bei schwankenden Einflussfaktoren ausgesetzt. F{\"u}r eine wirtschaftliche Fertigung sind Pressen erforderlich, die sich den steigenden Anforderungen und schwankenden Einflussfaktoren anpassen und mit m{\"o}glichst hoher Produktivit{\"a}t, Qualit{\"a}t und Wirtschaftlichkeit eine breite Produktpalette fertigen k{\"o}nnen. Unter diesen Voraussetzungen bietet sich der Einsatz von kraftgebundenen Servospindelpressen an. Diese erm{\"o}glichen frei programmierbare St{\"o}ßelbewegungsprofile und stellen die Nennkraft {\"u}ber den gesamten St{\"o}ßelhub zur Verf{\"u}gung. Allerdings erf{\"u}llen die bekannten Servospindelpressen die Forderung nach wandlungsf{\"a}higen Pressen, welche an unterschiedliche Anforderungen angepasst werden, besonders die {\"A}nderung der Abfolge von Teilprozessen und der Austausch von Maschinenkomponenten, nur sehr eingeschr{\"a}nkt. Aus diesem Grund wird ein neuartiges wandelbares Pressensystem entwickelt. Dieses soll dem Anwender weitreichende Vorteile bringen: Die Nennkraft des Pressensystems wird auf mehrere, in Durchlaufrichtung der Teile frei positionierbare und miteinander koppelbare Pressenmodule mit eigenen Pressenantrieben und -st{\"o}ßeln aufgeteilt. Durch Servospindelantriebe werden prozessangepasste St{\"o}ßelbewegungsprofile f{\"u}r einzelne Teilprozesse erm{\"o}glicht. Dies erlaubt eine wandelbare Anordnung von Teilprozessen, wodurch die Prozesskette skaliert werden kann. Unterst{\"u}tzt wird die Wandlungsf{\"a}higkeit des Pressensystems, indem es durch den Anwender erweitert werden kann und sich weitere Prozesse wie Schweißen, L{\"o}ten oder Kleben integrieren lassen. Ziel der Arbeit ist die Entwicklung des beschriebenen wandlungsf{\"a}higen Pressensystems mit Servospindelantrieb f{\"u}r die Komplettbearbeitung von kleinen Bauteilen. Grundlage bildet die Untersuchung des Standes der Pressentechnik und der Methoden der Produktentwicklung. Der Entwicklungsprozess wird in die Phasen Anforderungsfindung, Konzeptfindung und Entwurfsfindung gegliedert. Zur {\"U}berpr{\"u}fung wird aus dem Entwurf ein Prototyp ausgearbeitet. Im Anschluss werden Maßnahmen zur Produktstrukturierung durchgef{\"u}hrt, aus denen die Weiterentwicklung des Entwurfes zu einer Typengruppe und einem Baukastensystem resultiert. Zum Abschluss wird das Pressensystem bewertet, sein Einsatzspektrum beschrieben und das Pressensystem innerhalb bestehender Pressen eingeordnet.}, subject = {Umformtechnik; Pressensystem; Wandlungsf{\"a}higkeit; Servopresse; Spindelpresse; Forming technology; Press system; Adaptability; Servo press; Spindle press; Presse ; Spindel ; Servomotor}, language = {de} } @phdthesis{Maqbool2021, author = {Maqbool, Fawad}, title = {Targeted generation and suppression of the deformation mechanism and residual stresses in incremental sheet forming to improve the geometric accuracy}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-55646}, school = {BTU Cottbus - Senftenberg}, year = {2021}, abstract = {The geometric accuracy of an incrementally formed part is dependent on the underlying deformation mechanism and the residual stresses induced in the material during forming. This thesis presents new insights into the deformation mechanism and residual stresses of the Single Point Incremental Forming (SPIF) variant of the ISF process. In addition, strategies to control, suppress and adjust the deformation mechanism and residual stresses to increase the geometric accuracy and improve part properties are presented. The deformation mechanism of the ISF process is investigated. A novel methodology is developed to split the plastic energy dissipation during the SPIF process as a contributions of energies from dominant deformation modes. It is found that the dominant deformation mode can be bending, shear or membrane stretching, depending on the selected values of the process parameters. By controlling the contribution of each deformation mechanism, the outcome of the SPIF process can be designed for maximum geometric accuracy within the constraints of process time and formability. The build-up of the residual stresses in the SPIF process is investigated and a relation between the geometric accuracy and the residual stresses under changing process parameters is developed. The wall angle parameter has the highest influence on residual stresses. Moreover, the intensity and the magnitude of the residual stresses can be controlled by adjusting the process parameters. A direct approach based on post-forming Stress Relief Annealing (SRA) is developed to suppress residual stresses and increase geometric accuracy. In this regard, a modular tooling set-up is designed to perform the SRA under partial constraint. For maximum efficiency, optimal SRA parameters are determined. Two parts with practical significance are incrementally formed and subsequently stress relief annealed. A considerable increase in the geometric accuracy is observed with SRA in comparison to the parts without SRA. In the last part of this thesis, the very first approach is presented to generate a target distribution of high magnitude residual stresses in the ISF process for improving the mechanical properties. The desired residual stresses are generated in the conventionally formed disc springs in the surface treatment approach. In an integrated forming approach, the forming of the disc springs and the desired residual stresses are generated in a single step. Mechanical properties of the disc springs are better for both approaches in comparison to conventional disc springs. Hence, a targeted generation and distribution of the residual stresses to improve the mechanical properties is possible.}, subject = {Incremental sheet forming; Inkrementelle Blechumformung; Deformation mechanism; Residual stress; Geometric accuracy; Annealing; Verformungsmechanismus; Eigenspannung; Geometrische Genauigkeit; Gl{\"u}hen; Blechumformen; Eigenspannung; Deformation; Genauigkeit}, language = {en} } @phdthesis{Simon1999, author = {Simon, Sylvio}, title = {M{\"o}glichkeiten der Materialflußoptimierung an Betonmischanlagen}, isbn = {3-933342-50-3}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-1515}, school = {BTU Cottbus - Senftenberg}, year = {1999}, abstract = {Station{\"a}re Betonmischanlagen sind h{\"o}chstens zu 50 \% ausgelastet. Mit zunehmender Anlagengr{\"o}ße sinkt dies Auslastung weiter, da die Zeitanteile f{\"u}r Dosieren, F{\"u}llen und Entleeren zunehmen, die Mischzeit aber konstant bleibt. Die vorliegende Arbeit beschreibt und diskutiert verschiedene M{\"o}glichkeiten, die Auslastung der Betonmischanlagen deutlich zu steigern. Je nach Anforderungen sind durch den Zweik{\"u}belaufzug, den Mischernachbeh{\"a}lter als auch durch einen neuen Mischer die gr{\"o}ßten Steigerungen m{\"o}glich. Die vorgestellten L{\"o}sungen sind sowohl f{\"u}r neue Anlagen als auch zur Rekonstruktion von Altanlagen geeignet. Als positiver Nebeneffekt kann jede Betonmischanlage nun auch effektiv als Trockenf{\"u}llstation f{\"u}r Betonmischfahrzeuge fungieren. Alle L{\"o}sungen beeinflussen nicht die in Normen, z.B. DIN 1045 festgelegte Mindestmischzeit von 30 Sekunden.}, subject = {Betonmischer; Beschicken; Dosieren; Prozessoptimierung}, language = {de} } @article{ErtugrulEmdadiJedynaketal.2025, 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}, year = {2025}, 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.}, subject = {Hybrid manufacturing; Laser-directed energy deposition (L-DED); Hot-forming; Inconel 625 (In625); Microstructure manipulation}, language = {en} } @phdthesis{Soyama2014, author = {Soyama, Juliano}, title = {Development of creep resistant titanium aluminide alloys for the Metal Injection Moulding process}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-31610}, school = {BTU Cottbus - Senftenberg}, year = {2014}, abstract = {Titanium aluminides show great technological potential due to their light weight and excellent creep resistance. Their utilisation thus offers a potential to decrease fuel consumption and simultaneously improve the performance of components subjected to stress at high temperatures. However, shaping of titanium aluminides is still a very challenging and costly task considering their brittleness and the sensitivity on chemical composition. Therefore powder metallurgy near-net shape manufacturing techniques are very attractive to decrease material waste and reduce overall processing costs. This research work was focused on the preparation, characterisation and optimisation of creep resistant titanium aluminides for the Metal Injection Moulding (MIM) process. Considering the little information available regarding processing of titanium aluminides by MIM, this work had firstly the goal of assessing the creep behaviour of a reference titanium aluminide alloy. Secondly, alloy variations with compositions based on the reference material were designed with the objective of improving the creep resistance, especially concerning primary creep. The basic strengthening mechanisms applied involved the addition of slow diffusing elements and elements that cause precipitation of hard particles. The specimens were prepared by using pre-alloyed powder and mixtures of a master alloy (pre-alloyed) and elemental powders. Consequently, a great deal of effort was spent in the characterisation of the sintering behaviour in order to achieve reliable test pieces. Even though both methods can deliver sound specimens, the pre-alloyed powder approach led to the best results in terms of residual porosity and microstructural homogeneity. The mechanical testing results indicate that processing of titanium aluminides by MIM is feasible and acceptable creep properties can be achieved with the proper sintering parameters. Even though the ductility at room temperature was considerably limited due to the residual porosity and high amounts of impurities intrinsic to the MIM process, alloys developed within this study showed improved primary creep resistance in the high stress - high temperature regime. In particular alloy variations containing additions of Mo, Si and Gd led to a considerable improvement of the primary creep resistance in comparison to the reference material at 800°C - 350 MPa loading.}, subject = {Titanium Aluminides; Creep; Metal Injection Moulding; Metallpulverspritzguss; Kriechen; Titanaluminide; Titanaluminide; Kriechen; Metallpulver; Spritzgießen}, language = {en} } @article{AlimovSviridovJenschetal.2023, author = {Alimov, Artem and Sviridov, Alexander and Jensch, Felix and Sydow, Benjamin and H{\"a}rtel, Sebastian}, title = {Additive manufacturing of hot-forming dies using laser powder bed fusion and wire arc direct energy deposition technologies}, volume = {13}, number = {11}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/met13111842}, year = {2023}, 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.}, subject = {Additive manufacturing; Hot-forming dies; L-PBF; WA-DED; WAAM; Additive Fertigung; Warmumformwerkzeuge; L-PBF; WA-DED; WAAM; Warmumformen; Rapid Prototyping (Fertigung); Selektives Laserschmelzen}, language = {en} } @article{GruegerJenschDittrichetal.2024, 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 manufac-2tured AZ91 and Ti-6Al-4V components in the context of medi-3cal applications}, series = {Materials}, volume = {17}, journal = {Materials}, number = {18}, publisher = {MDPI}, address = {Basel}, issn = {1996-1944}, doi = {10.3390/ma17184667}, year = {2024}, 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.}, subject = {AZ91; Ti-6Al-4V; Additive manufacturing; L-PBF; Implant technology}, language = {en} } @phdthesis{Nguyen2022, author = {Nguyen, Qui Lam}, title = {Tool path planning for wire-arc additive manufacturing processes}, doi = {10.26127/BTUOpen-5982}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-59827}, school = {BTU Cottbus - Senftenberg}, year = {2022}, abstract = {Among variants of AM technology, wire-arc additive manufacturing (WAAM) process suitably produces bulky metal parts with a medium complexity. Although WAAM shows a great potential, this process has not been fully explored, and it is therefore a worthwhile subject to further investigate. This monograph engages with tool path planning for the WAAM process and existing problems in WAAM are subsequently addressed, as following: The existing overlapping models yield an uneven surface due to the inner beads overlapping with two neighbor beads while the outers have only a one-sided overlap. New mathematical models are established to obtain optimal distances between adjacent weld beads and to make surfaces more even. Lightweight structures have high strength as compared to their weight. Producing these structures by WAAM results in imperfections because of uneven weld beads - an inevitable phenomenon when starting a new track. A new tool path strategy to produce lightweight structures is developed using contour patterns, which transforms any arbitrary geometry into that of a continuous path. Unfortunately, voids are formed at junctions when using contour patterns. An adaptive correction using machine learning is then developed to overcome this defect. Large overhangs and inclined features are out of reach of WAAM when operating in the x-y plane in Cartesian system. This limits the ability of the WAAM process. To overcome that, each overhang feature should be welded with a distinct direction. This approach is realized within the robot based WAAM process. Establishing the kinematics of the FANUC robot arm and the positioner helps compute the new coordinates, the angular displacements of the positioner, and the orientation of the torch. The proposed strategy is examined through the construction of an overhang part. The capabilities of the multi-axis deposition are extended by constructing curved thin-walled structures. Irregular thickness layers are deposited by controlling the travel speed, resulting in a different deposition rate. The curved thin-walled structures can be properly fabricated by combining a multi-axis deposition with non-uniform thickness layers. Bonding quality as well as geometric accuracy are also to be investigated. To ensure geometric accuracy, a compensation strategy is developed. The performance of the proposed algorithm is validated on different geometries. This monograph will conclude with a summary of this work's main achievements and contributions as well as outlooks on future research.}, subject = {Wire-arc additive manufacturing; Lightweight structures; Curve thin-walled structures; Multi-bead overlapping models; Lichtbogenadditive Fertigung; Leichte Strukturen; Gekr{\"u}mmte d{\"u}nnwandige Strukturen; {\"U}berlappende Modelle; Rapid Prototyping ; D{\"u}nne Schale; Lichtbogen; {\"U}berlappung}, language = {en} } @phdthesis{Ulbricht2022, author = {Ulbricht, Alexander}, title = {Multi-scale correlation between defects and internal stresses in additively manufactured AISI316L structures}, doi = {10.26127/BTUOpen-6374}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-63746}, school = {BTU Cottbus - Senftenberg}, year = {2022}, abstract = {Additive Manufacturing of metals has become relevant for industrial applications. The near net-shape production of components produced by Laser Powder Bed Fusion (PBF-LB/M) enables new possibilities in component design combined with a reduction of the amount of needed material. Omitting the extra material, that was part of conventionally produced components due to machining constraints, results in components which in consequence lack the inherent additional safety margins provided by the higher material consumption of conventionally produced components. Therefore, to use PBF-LB/M metals in safety critical applications an in-depth understanding of porosity and internal stresses in parts made by PBF-LB/M is needed. Only non-destructive testing methods—such as computed tomography and residual stress analysis using neutrons—enable the assessment of porosity and stresses in the whole part. In this thesis I tackled creep and tensile static deformed specimens to fill research gaps in this field in terms of analysing PBF-LB/M stainless steel AISI 316L: from structural properties to in-situ behaviour. The initial void population of AISI 316L is studied using X-ray and synchrotron micro computed tomography. Specimens produced with different process parameters were analysed to quantify the influence of process parameters on the initial void population. The possibility to close voids using the laser illumination of subsequent layers is discussed by a quantitative study of the ability of the laser to melt different multiples of the applied layer thickness. The formation of internal stress is inherent to components produced by the PBFLB/ M process. These stresses remain in the components after production as residual stresses. In this thesis a study is presented which aims to unravel the mechanisms that define the spatial distribution of the residual stresses, and their magnitude. In the end, the population of internal voids during mechanical testing is studied by X-ray micro computed tomography. The evolution of damage accumulation in creep specimens is studied at different stages of the creep test. Results are compared to a creep tested conventionally made specimen and to a PBF-LB/M specimen from a tensile test. An interconnection between the PBF-LB/M microstructure and the pattern of damage is revealed.}, subject = {Additive manufacturing; Computed tomography; Neutron diffraction; Residual stress; 316L; Additive Fertigung; Computertomographie; Neutronenbeugung; Edelstahl; Rapid Prototyping (Fertigung); Selektives Laserschmelzen; Zerst{\"o}rungsfreie Werkstoffpr{\"u}fung; Computertomografie; Neutronenbeugung}, language = {en} } @phdthesis{Sviridov2011, author = {Sviridov, Alexander}, title = {Leichtbau mit Aluminiumschaumsandwich : Prozessketten zur Herstellung von Bauteilen}, isbn = {978-3-86624-555-6}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-23664}, school = {BTU Cottbus - Senftenberg}, year = {2011}, abstract = {Die Anforderungen an Blechhalbzeuge steigen st{\"a}ndig. Dabei sucht die blechbearbeitende Industrie nach neuen Werkstoffen mit multifunktionalen Eigenschaften, da die konventionellen Werkstoffe die gestellten Anforderungen nicht bzw. nur teilweise erf{\"u}llen k{\"o}nnen. Als innovativer Werkstoff zeigte dabei der Aluminiumschaum ein großes Potential bei der Verwendung als Komponente eines Verbundes. Dieser Verbund ist Aluminiumschaumsandwich (AFS), das aus Aluminiumblechen als Decklagen und Aluminiumschaum als Kernschicht besteht. In der vorliegenden Arbeit wurden umfassende Untersuchungen an Aluminiumschaumsandwichen durchgef{\"u}hrt und Fertigungsstrategie zur Herstellung vom praxisnahen Prototyp entwickelt. Dabei wurden neben den Umform- und Aufsch{\"a}umtechnologien auch die F{\"u}getechniken (u.a. Schweißen und Blindnieten) untersucht und erprobt. Welches Verfahren in einem einzelnen Fall besser geeignet ist, h{\"a}ngt stark von der Anwendung sowie von den gestellten Anforderungen ab. Die nachgewiesene Machbarkeit von hergestellten Bauteilen verdeutlicht das Einsatzpotential dieses innovativen Werkstoffes.}, subject = {Leichtbau; Schaumaluminium; Sandwichbauteil; Aluminiumschaum; Aluminiumschaumsandwich; AFS; Leichtbau; Prozesskette; Aluminium foam; Aluminium foam sandwich; AFS; Lightweight design; Process chain}, language = {de} } @phdthesis{Imran2021, author = {Imran, Muhammad}, title = {Investigating and modeling the effect of metal forming-related measures for damage-controlled hot forming}, doi = {10.26127/BTUOpen-5710}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-57105}, school = {BTU Cottbus - Senftenberg}, year = {2021}, abstract = {Within the process chains of the semi-finished production, hot forming is used to eliminate pores and voids from the casting process under compressive stresses and to adjust the microstructure for further processing. In the case of caliber rolling process, tensile stresses occur at certain roll gap ratios which promote void formation (damage) on non-metallic inclusion. Decohesion of matrix and inclusion in void formation is determined by local flow stress. Since the process is carried out above recrystallization temperature, damage cannot only be controlled through stress state (stress triaxiality and Lode parameter) but also the softening processes like dynamic recovery (DRV) and recrystallization (DRX) which can relieve local stresses. Such processes can be used to delay or prevent the damage initiation and growth and hence the mechanical properties of components can be improved. In spite of this, the influence of DRX on damage development has not been quantified so far. This study focuses on the understanding the interaction between softening processes and damage during hot forming and to derive a model for coupled microstructure and damage evolution. For precise damage modeling, in-depth damage characterization of the specimens deformed during hot tensile tests under different stress states and deformation conditions (temperature and strain rate) is conducted. The stress states are varied by designing the specimens with different notch radii. To model the influence of local stresses on damage, continuum-based damage modeling approach is adapted where a system of matrix-inclusion-interface is considered. The influence of different parameters such as DRX, stress state, temperature, strain rate, total strain, inclusion size and type (soft/hard) is analyzed. Based on the damage quantification results, an extension to Gurson-Tvergaard-Needleman (GTN) damage model is devised where a new nucleation criterion couples the stress state and DRX to the void formation at inclusions. The extended GTN model is utilized to predict the internal damage during multi-step hot caliber rolling process and validated with experimentally observed damage at different locations of stress state and recrystallized volume fraction. Based on the model, a damage-controlled strategy is proposed by finding the solution of optimal control problem (OCP) to obtain an optimal variable deformation speed that can induce low damage as compared to constant speed while keeping the process time constant. To implement the damage-controlled strategy, an isothermal forming simulator is designed and manufactured that can replicate the real load paths during hot forming. It is suggested that damage can be controlled if material is allowed to recrystallize at low deformation speed without inducing damage and then, speed up the deformation after onset of recrystallization.}, subject = {Damage modeling; Dynamic recrystallization; Damage; Hot forming; Hot caliber rolling; Sch{\"a}digungskontrolle; Sch{\"a}digungsmodellierung; Dynamische Rekristallisation; Warmumformung; Spannungszustand; Warmumformen; Werkstoffsch{\"a}digung; Schadensanalyse}, language = {en} } @phdthesis{Zhao2014, author = {Zhao, Dapeng}, title = {Metal Injection Moulding of Titanium-Niobium alloys for biomedical applications}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-30515}, school = {BTU Cottbus - Senftenberg}, year = {2014}, abstract = {The main subject of this work was the investigation of sintering behavior, microstructure, mechanical properties and biocompatibility of metal injection moulded (MIM) Ti-Nb alloys for biomedical applications. Commercially pure titanium (CP-Ti) samples were also fabricated by MIM as a reference. The sintering behavior of MIM Ti-Nb alloys was studied at first, in order to roughly determine the sintering parameters in the following investigations. Dilatometry was applied to investigate the linear shrinkage of MIM Ti-Nb samples from room temperature to 1500 °C at a heating rate of 3 °C/min under argon atmosphere. Various sintering parameters and Nb contents were used to investigate their influences on microstructure and mechanical properties of MIM Ti-Nb alloys by means of density measurements, optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and mechanical testing. Transmission electron microscopy (TEM) and high energy X-ray diffraction (HEXRD) measurement were applied to investigate the nature and precipitation of the unexpected titanium carbide precipitates in MIM Ti-Nb alloys. Initial cell adhesion and cell proliferation assays of human umbilical cord perivascular cells (HUCPV) on MIM Ti-Nb alloys were performed for biocompatibility characterization. The results of this work show that MIM Ti-Nb and MIM CP-Ti samples have been successfully fabricated and the as-sintered samples show good shape retention without distortion compared to the green sample. The sintering process of MIM Ti-Nb alloys consists of three main steps - Ti-diffusion step, Ti-Nb-diffusion step and Matrix-diffusion step. With increasing sintering temperatures and time, MIM Ti-Nb alloys exhibit lower porosity and higher Young's modulus. A higher Nb content in MIM Ti-Nb alloys leads to an increase of carbide area fraction and porosity. The three factors - Nb content, carbide area fraction and porosity - determine the mechanical properties of MIM Ti-Nb alloys. An increase of Nb content and amount of carbides as well as a lowered porosity lead to a higher tensile strength. A decrease of Young's modulus can be expected with higher Nb content and porosity. A high amount of titanium carbides can result in very poor ductility, but annealing and quenching process can significantly improve the elongation by dissolving the carbides. MIM Ti-Nb alloys exhibit good biocompatibility, indicating their potential for implant applications.}, subject = {Metallpulver; Spritzgießen; Sintern; Titanlegierung; Nioblegierung; Ti-Nb Legierungen; Metallspritzgießen; Sintern; Titan-Karbid; Mechanische Eigenschaft; Ti-Nb alloys; Metal injection moulding; Sintering; Titanium carbide; Mechanical behaviour}, language = {en} } @phdthesis{Babel2025, author = {Babel, Christoph Josef}, title = {Virtual evaluation of car body panel surfaces}, doi = {10.26127/BTUOpen-7196}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-71960}, school = {BTU Cottbus - Senftenberg}, year = {2025}, abstract = {The progression of the automotive industry has introduced a slew of complex designs to meet the personalized style expressions of consumers. However, these intricate designs in premium automobiles present significant manufacturing challenges, especially in detecting and prioritizing the varying severities of cosmetic surface defects. Traditionally, defect identification is performed at the end of the development phase, which is a costly and time-consuming process. This thesis seeks to enhance early defect detection efficiency in the concept phase using artificial intelligence (AI). Through examination of unpainted parts, auditors' perceptual practices, and deep draw simulations, the research aims to establish a virtual prediction method to accurately classify surface defects. The findings of this thesis prove that the geometry of unpainted parts sufficiently predicts potential defects post-painting, refuting the need for physical painted part analysis. The identification process adopted by auditors, grounded in analyzing light distortions on surfaces, is replicated within a neural network. Furthermore, by incorporating physiological optical aspects, the thesis improves the virtual representation of defects, creating a visible and analyzable dataset for AI algorithms. The accuracy of the neural networks trained on such datasets is substantiated by the successful translation of auditors' classification methods into a machine learning environment. In particular, a machine learning approach using Random Forest (RF) algorithms excelled in prefiltering areas of interest based on curvature and strain values. A convolutional recurrent neural network (CRNN) is developed to classify the severity of defects, with the introduction of an annotation application to label data by experts. The CRNN demonstrated a remarkable accuracy of 86 \% in classifying defect severity based on simulation data. Moreover, the study assessed the frame-by-frame localization of defects, where the PatchCore anomaly detection algorithm proves optimal, achieving an F1 Score of 0.86. Overall, the research successfully shows the transferability of expert auditors' perception into a neural network architecture, highlighting the feasibility of implementing AI in early phases of automotive design to predict and classify defects, which has the potential to significantly reduce development costs and improve manufacturing efficiency.}, subject = {Computer vision; Neural network; Deep draw simulation; Rendering; K{\"u}nstliche Intelligenz; Maschinelles Lernen; Umformsimulation; Bildgenerierung; Kraftfahrzeugindustrie; Produktentwicklung; Tiefziehen; Fehlererkennung; Simulation; K{\"u}nstliche Intelligenz; Maschinelles Lernen}, language = {en} }