TY - JOUR A1 - Mishurova, Tatiana A1 - Cabeza, Sandra A1 - Artzt, Katia A1 - Haubrich, Jan A1 - Klaus, Manuela A1 - Genzel, Christoph A1 - Requena, Guillermo A1 - Bruno, Giovanni T1 - An Assessment of Subsurface Residual Stress Analysis in SLM Ti-6Al-4V JF - Materials N2 - Ti-6Al-4V bridges were additively fabricated by selective laser melting (SLM) under different scanning speed conditions, to compare the effect of process energy density on the residual stress state. Subsurface lattice strain characterization was conducted by means of synchrotron diffraction in energy dispersive mode. High tensile strain gradients were found at the frontal surface for samples in an as-built condition. The geometry of the samples promotes increasing strains towards the pillar of the bridges. We observed that the higher the laser energy density during fabrication, the lower the lattice strains. A relief of lattice strains takes place after heat treatment. KW - selective laser melting KW - additive manufacturing KW - heat treatment KW - Ti-6Al-4V KW - synchrotron X-ray diffraction KW - residual stress Y1 - 2017 U6 - https://doi.org/10.3390/ma10040348 SN - 1996-1944 VL - 10 PB - MDPI CY - Basel ER - TY - JOUR A1 - Thiede, Tobias A1 - Cabeza, Sandra A1 - Mishurova, Tatiana A1 - Nadammal, Naresh A1 - Kromm, Arne A1 - Bode, Johannes A1 - Haberland, Christoph A1 - Bruno, Giovanni T1 - Residual Stress in Selective Laser Melted Inconel 718 BT - Influence of the Removal from Base Plate and Deposition Hatch Length JF - Materials performance and characterization N2 - The residual stress distribution in IN718 elongated prisms produced by selective laser melting was studied by means of neutron (bulk) and laboratory X-ray (surface) diffraction. Two deposition hatch lengths were considered. A horizontal plane near the top surface (perpendicular to the building direction) and a vertical plane near the lateral surface (parallel to the building direction) were investigated. Samples both in as-built (AB) condition and removed from the base plate (RE) were characterized. While surface stress fields seem constant for the AB condition, X-ray diffraction shows stress gradients along the hatch direction in the RE condition. The stress profiles correlate with the distortion maps obtained by tactile probe measurements. Neutron diffraction shows bulk stress gradients for all principal components along the main sample directions. We correlate the observed stress patterns with the hatch length, i.e., with its effect on temperature gradients and heat flow. The bulk stress gradients partially disappear after removal from the base plate. KW - residual stress KW - IN718 KW - neutron diffraction KW - laboratory x-ray diffraction KW - additive manufacturing KW - selective laser melting KW - coordinate measurement machine Y1 - 2018 U6 - https://doi.org/10.1520/MPC20170119 SN - 2379-1365 SN - 2165-3992 VL - 7 IS - 4 SP - 717 EP - 735 PB - American Society for Testing and Materials CY - West Conshohocken ER - TY - GEN A1 - Müller, Bernd Randolf A1 - Kupsch, Andreas A1 - Laquai, Rene A1 - Nellesen, Jens A1 - Tillmann, Wolfgang A1 - Kasperovich, Galina A1 - Bruno, Giovanni T1 - Microstructure Characterisation of Advanced Materials via 2D and 3D X-Ray Refraction Techniques T2 - Materials Science Forum N2 - 3D imaging techniques have an enormous potential to understand the microstructure, its evolution, and its link to mechanical, thermal, and transport properties. In this conference paper we report the use of a powerful, yet not so wide-spread, set of X-ray techniques based on refraction effects. X-ray refraction allows determining internal specific surface (surface per unit volume) in a non-destructive fashion, position and orientation sensitive, and with a nanometric detectability. We demonstrate showcases of ceramics and composite materials, where microstructural parameters could be achieved in a way unrivalled even by high-resolution techniques such as electron microscopy or computed tomography. We present in situ analysis of the damage evolution in an Al/Al2O3 metal matrix composite during tensile load and the identification of void formation (different kinds of defects, particularly unsintered powder hidden in pores, and small inhomogeneity’s like cracks) in Ti64 parts produced by selective laser melting using synchrotron X-ray refraction radiography and tomography. KW - X-ray refraction KW - radiography KW - tomography KW - synchrotron X-ray refraction radiography KW - CT KW - microscopy KW - creep KW - porosity KW - damage evolution KW - additive manufacturing KW - metal matrix composite Y1 - 2018 SN - 978-3-0357-1208-7 U6 - https://doi.org/10.4028/www.scientific.net/MSF.941.2401 SN - 0255-5476 VL - 941 SP - 2401 EP - 2406 PB - Trans Tech Publications Ltd CY - Zurich ER - TY - THES A1 - Thiede, Tobias T1 - A multiscale analysis of additively manufactured lattice structures T1 - Multiskalige Analyse von Additiv Gefertigten Gitterstrukturen N2 - Additive Manufacturing (AM) in terms of laser powder-bed fusion (L-PBF) offers new prospects regarding the design of parts and enables therefore the production of lattice structures. These lattice structures shall be implemented in various industrial applications (e.g. gas turbines) for reasons of material savings or cooling channels. However, internal defects, residual stress, and structural deviations from the nominal geometry are unavoidable. In this work, the structural integrity of lattice structures manufactured by means of L-PBF was non-destructively investigated on a multiscale approach. A workflow for quantitative 3D powder analysis in terms of particle size, particle shape, particle porosity, inter-particle distance and packing density was established. Synchrotron computed tomography (CT) was used to correlate the packing density with the particle size and particle shape. It was also observed that at least about 50% of the powder porosity was released during production of the struts. Struts are the component of lattice structures and were investigated by means of laboratory CT. The focus was on the influence of the build angle on part porosity and surface quality. The surface topography analysis was advanced by the quantitative characterisation of re-entrant surface features. This characterisation was compared with conventional surface parameters showing their complementary information, but also the need for AM specific surface parameters. The mechanical behaviour of the lattice structure was investigated with in-situ CT under compression and successive digital volume correlation (DVC). The deformation was found to be knot-dominated, and therefore the lattice folds unit cell layer wise. The residual stress was determined experimentally for the first time in such lattice structures. Neutron diffraction was used for the non-destructive 3D stress investigation. The principal stress directions and values were determined in dependence of the number of measured directions. While a significant uni-axial stress state was found in the strut, a more hydrostatic stress state was found in the knot. In both cases, strut and knot, seven directions were at least needed to find reliable principal stress directions. N2 - Das Laserstrahlschmelzen (L-PBF) als Prozess im Bereich der Additiven Fertigung (AM) ermöglicht ein neuartiges Bauteildesign und somit auch die Produktion von komplexen Gitterstrukturen, welche Materialeinsparungen und effizientere Kühlsysteme erlauben und daher für verschiedene industrielle Anwendungen (z.B. Gasturbinen) geeignet sind. Interne Defekte, Eigenspannungen und geometrische Abweichungen von der Soll-Geometrie sind jedoch unvermeidbar. Im Rahmen dieser Arbeit wird die strukturelle Integrität von L-PBF gefertigten Gitterstrukturen zerstörungsfrei auf verschiedenen Größenskalen untersucht. Eine Auswerteroutine für dreidimensionale quantitative Pulvercharakterisierung hinsichtlich der Partikelgröße, der -form, der -porosität, des Interpartikelabstands und der Packungsdichte wurde entwickelt. Synchrotron Computertomographie (CT) wurde für die Korrelation der Packungsdichte mit der Partikelgröße und -form genutzt. Darüber hinaus konnte festgestellt werden, dass mindestens 50% der Porosität aus den Pulverpartikel während der Herstellung der Streben mittels L-PBF gelöst wurde. Streben sind die Grundbausteine der Gitterstrukturen und wurden mit industrieller CT untersucht. Dabei lag der Fokus auf dem Einfluss des Bauwinkels auf die Strebenporosität und -oberflächenqualität. Die Analyse der Oberflächentopographie wurde hinsichtlich einer quantitativen Analyse von sogenannten re-entrant features erweitert. Der Vergleich dieser Auswertung mit konventionellen Oberflächenparametern offenbarte sowohl deren Komplementarität also auch den Bedarf an neuen AM-spezifischen Oberflächenparametern. In-situ CT Versuche mit anschließender digitaler Volumenkorrelation (DVC) erlaubte die Gitterstruktur bezüglich des mechanischen Verhaltens unter Druckspannung zu bewerten. Aufgrund einer schichtweisen Faltung der Einheitszellen konnte dabei das Versagensverhalten als knoten-dominiert identifiziert werden. Mittels Neutronenbeugung konnten Eigenspannungen in solchen Gitterstrukturen erstmalig experimentell bestimmt werden. Dabei wurden sowohl die Hauptspannungsrichtungen als auch die -beträge in Abhängigkeit von der Anzahl der gemessenen Spannungsrichtungen bestimmt. Während in der Strebe ein signifikanter uni-axialer Spannungszustand nachgewiesen wurde, zeigte der Knotenpunkt einen hydrostatischeren Spannungszustand. Sowohl im Falle der Strebe als auch des Knotenpunkts waren mindestens sieben gemessene Spannungsrichtungen nötig, um die Hauptspannungsrichtungen verlässlich zu ermitteln. KW - additive manufacturing KW - laser powder bed fusion KW - computed tomography KW - neutron diffraction KW - in-situ testing KW - residual stress KW - roughness KW - powder particle analysis KW - additive Fertigung KW - Laserstrahlschmelzen KW - Computertomographie KW - Neutronendiffraktion KW - In-situ Experimente KW - Eigenspannung KW - Rauheit KW - Pulverpartikelanalyse Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-470418 ER - TY - JOUR A1 - Mishurova, Tatiana A1 - Artzt, Katia A1 - Haubrich, Jan A1 - Requena, Guillermo A1 - Bruno, Giovanni T1 - Exploring the correlation between subsurface residual stresses and manufacturing parameters in laser powder bed fused Ti-6Al-4V JF - Metals N2 - Subsurface residual stresses (RS) were investigated in Ti-6Al-4V cuboid samples by means of X-ray synchrotron diffraction. The samples were manufactured by laser powder bed fusion (LPBF) applying different processing parameters, not commonly considered in open literature, in order to assess their influence on RS state. While investigating the effect of process parameters used for the calculation of volumetric energy density (such as laser velocity, laser power and hatch distance), we observed that an increase of energy density led to a decrease of RS, although not to the same extent for every parameter variation. Additionally, the effect of support structure, sample roughness and LPBF machine effects potentially coming from Ar flow were studied. We observed no influence of support structure on subsurface RS while the orientation with respect to Ar flow showed to have an impact on RS. We conclude recommending monitoring such parameters to improve part reliability and reproducibility. KW - residual stress KW - synchrotron X-ray diffraction KW - additive manufacturing KW - Ti-6Al-4V Y1 - 2019 U6 - https://doi.org/10.3390/met9020261 SN - 2075-4701 VL - 9 IS - 2 PB - MDPI CY - Basel ER - TY - JOUR A1 - Mishurova, Tatiana A1 - Sydow, Benjamin A1 - Thiede, Tobias A1 - Sizova, Irina A1 - Ulbricht, Alexander A1 - Bambach, Markus A1 - Bruno, Giovanni T1 - Residual stress and microstructure of a Ti-6Al-4V Wire Arc Additive Manufacturing hybrid demonstrator JF - Metals N2 - Wire Arc Additive Manufacturing (WAAM) features high deposition rates and, thus, allows production of large components that are relevant for aerospace applications. However, a lot of aerospace parts are currently produced by forging or machining alone to ensure fast production and to obtain good mechanical properties; the use of these conventional process routes causes high tooling and material costs. A hybrid approach (a combination of forging and WAAM) allows making production more efficient. In this fashion, further structural or functional features can be built in any direction without using additional tools for every part. By using a combination of forging basic geometries with one tool set and adding the functional features by means of WAAM, the tool costs and material waste can be reduced compared to either completely forged or machined parts. One of the factors influencing the structural integrity of additively manufactured parts are (high) residual stresses, generated during the build process. In this study, the triaxial residual stress profiles in a hybrid WAAM part are reported, as determined by neutron diffraction. The analysis is complemented by microstructural investigations, showing a gradient of microstructure (shape and size of grains) along the part height. The highest residual stresses were found in the transition zone (between WAAM and forged part). The total stress range showed to be lower than expected for WAAM components. This could be explained by the thermal history of the component. KW - residual stress KW - WAAM KW - Ti-6Al-4V KW - additive manufacturing KW - neutron KW - diffraction KW - hybrid manufacturing Y1 - 2020 U6 - https://doi.org/10.3390/met10060701 SN - 2075-4701 VL - 10 IS - 6 PB - MDPI CY - Basel ER - TY - THES A1 - Bäckemo, Johan Dag Valentin T1 - Digital tools and bioinspiration for the implementation in science and medicine T1 - Digitale Werkzeuge und Bioinspiration für die Umsetzung in der Wissenschaft und der Medizin N2 - Diese Doktorarbeit untersucht anhand dreier Beispiele, wie digitale Werkzeuge wie Programmierung, Modellierung, 3D-Konstruktions-Werkzeuge und additive Fertigung in Verbindung mit einer auf Biomimetik basierenden Design\-strategie zu neuen Analysemethoden und Produkten führen können, die in Wissenschaft und Medizin Anwendung finden. Das Verfahren der Funkenerosion (EDM) wird häufig angewandt, um harte Metalle zu verformen oder zu formen, die mit normalen Maschinen nur schwer zu bearbeiten sind. In dieser Arbeit wird eine neuartige Krümmungsanalysemethode als Alternative zur Rauheitsanalyse vorgestellt. Um besser zu verstehen, wie sich die Oberfläche während der Bearbeitungszeit des EDM-Prozesses verändert, wurde außerdem ein digitales Schlagmodell erstellt, das auf einem ursprünglich flachen Substrat Krater auf Erhebungen erzeugte. Es wurde festgestellt, dass ein Substrat bei etwa 10.000 Stößen ein Gleichgewicht erreicht. Die vorgeschlagene Krümmungsanalysemethode hat das Potenzial, bei der Entwicklung neuer Zellkultursubstrate für die Stammzellenforschung eingesetzt zu werden. Zwei Arten, die in dieser Arbeit aufgrund ihrer interessanten Mechanismen analysiert wurden, sind die Venusfliegenfalle und der Bandwurm. Die Venusfliegenfalle kann ihr Maul mit einer erstaunlichen Geschwindigkeit schließen. Der Schließmechanismus kann für die Wissenschaft interessant sein und ist ein Beispiel für ein so genanntes mechanisch bi-stabiles System - es gibt zwei stabile Zustände. Der Bandwurm ist bei Säugetieren meist im unteren Darm zu finden und heftet sich mit seinen Saugnäpfen an die Darmwände. Wenn der Bandwurm eine geeignete Stelle gefunden hat, stößt er seine Haken aus und heftet sich dauerhaft an die Wand. Diese Funktion könnte in der minimalinvasiven Medizin genutzt werden, um eine bessere Kontrolle der Implantate während des Implantationsprozesses zu ermöglichen. Für beide Projekte wurde ein mathematisches Modell, das so genannte Chained Beam Constraint Model (CBCM), verwendet, um das nichtlineare Biegeverhalten zu modellieren und somit vorherzusagen, welche Strukturen ein mechanisch bi-stabiles Verhalten aufweisen könnten. Daraufhin konnten zwei Prototypen mit einem 3D-Drucker gedruckt und durch Experimente veranschaulicht werden, dass sie beide ein bi-stabiles Verhalten aufweisen. Diese Arbeit verdeutlicht das hohe Anwendungspotenzial für neue Analysenmethoden in der Wissenschaft und für neue Medizinprodukte in der minimalinvasiven Medizin. N2 - Biomimicry is the art of mimicking nature to overcome a particular technical or scientific challenge. The approach studies how evolution has found solutions to the most complex problems in nature. This makes it a powerful method for science. In combination with the rapid development of manufacturing and information technologies into the digital age, structures and material that were before thought to be unrealizable can now be created with simple sketch and the touch of a button. This doctoral thesis had as its primary goal to investigate how digital tools, such as programming, modelling, 3D-Design tools and 3D-Printing, with the help from biomimicry, could lead to new analysis methods in science and new medical devices in medicine. The Electrical Discharge Machining (EDM) process is applied commonly to deform or mold hard metals that are difficult to work using normal machinery. A workpiece submerged in an electrolyte is deformed while being in close vicinity to an electrode. When high voltage is put between the workpiece and the electrode it will cause sparks that create cavitations on the substrate which in turn removes material and is flushed away by the electrolyte. Usually, such surfaces are analysed based on roughness, in this work another method using a novel curvature analysis method is presented as an alternative. In addition, to better understand how the surface changes during process time of the EDM process, a digital impact model was created which created craters on ridges on an originally flat substrate. These substrates were then analysed using the curvature analysis method at different processing times of the modelling. It was found that a substrate reaches an equilibrium at around 10000 impacts. The proposed curvature analysis method has potential to be used in the design of new cell culture substrates for stem cell. The Venus flytrap can shut its jaws at an amazing speed. The shutting mechanism may be interesting to use in science and is an example of a so-called mechanical bi-stable system – there are two stable states. In this work two truncated pyramid structures were modelled using a non-linear mechanical model called the Chained Beam Constraint Model (CBCM). The structure with a slope angle of 30 degrees is not bi-stable and the structure with a slope angle of 45 degrees is bi-stable. Developing this idea further by using PEVA, which has a shape-memory effect, the structure which is not bi-stable could be programmed to be bi-stable and then turned off again. This could be used as an energy storage system. Another species which has interesting mechanism is the tapeworm. Some species of this animal has a crown of hooks and suckers located on its side. The parasite commonly is found in mammals in the lower intestine and attaches to the walls by using its suckers. When the tapeworm has found a suitable spot, it ejects its hooks and permanently attaches to the wall. This function could be used in minimally invasive medicine to have better control of implants during the implantation process. By using the CBCM model and a 3D-printer capable of tuning how hard or soft a printed part is, a design strategy was developed to investigate how one could create a device that mimics the tapeworm. In the end a prototype was created which was able attach to a pork loin at an under pressure of 20 kPa and to ejects its hooks at an under pressure of 50 kPa or above. These three projects is an exhibit of how digital tools and biomimicry can be used together to come up with applicable solutions in science and in medicine. KW - bioinspiration KW - non-linear mechanics KW - modelling KW - shape-memory KW - additive manufacturing KW - Bioinspiration KW - nichtlineare Mechanik KW - Modellierung KW - Formgedächtnis KW - additive Fertigung Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-571458 ER - TY - JOUR A1 - Loges, Klara A1 - Tiberius, Victor T1 - Implementation Challenges of 3D Printing in Prosthodontics BT - A Ranking-Type Delphi JF - Materials N2 - The reduction in cost and increasing benefits of 3D printing technologies suggest the potential for printing dental prosthetics. However, although 3D printing technologies seem to be promising, their implementation in practice is complicated. To identify and rank the greatest implementation challenges of 3D printing in dental practices, the present study surveys dentists, dental technicians, and 3D printing companies using a ranking-type Delphi study. Our findings imply that a lack of knowledge is the most crucial obstacle to the implementation of 3D printing technologies. The high training effort of staff and the favoring of conventional methods, such as milling, are ranked as the second and third most relevant factors. Investment costs ranked in seventh place, whereas the lack of manufacturing facilities and the obstacle of print duration ranked below average. An inclusive implementation of additive manufacturing could be achieved primarily through the education of dentists and other staff in dental practices. In this manner, production may be managed internally, and the implementation speed may be increased. KW - 3D printing KW - prosthodontics KW - ranking type Delphi study KW - additive manufacturing KW - dentistry Y1 - 2021 U6 - https://doi.org/10.3390/ma15020431 SN - 1996-1944 VL - 15 PB - MDPI CY - Basel ER - TY - GEN A1 - Loges, Klara A1 - Tiberius, Victor T1 - Implementation Challenges of 3D Printing in Prosthodontics BT - A Ranking-Type Delphi T2 - Postprints der Universität Potsdam Wirtschafts- und Sozialwissenschaftliche Reihe N2 - The reduction in cost and increasing benefits of 3D printing technologies suggest the potential for printing dental prosthetics. However, although 3D printing technologies seem to be promising, their implementation in practice is complicated. To identify and rank the greatest implementation challenges of 3D printing in dental practices, the present study surveys dentists, dental technicians, and 3D printing companies using a ranking-type Delphi study. Our findings imply that a lack of knowledge is the most crucial obstacle to the implementation of 3D printing technologies. The high training effort of staff and the favoring of conventional methods, such as milling, are ranked as the second and third most relevant factors. Investment costs ranked in seventh place, whereas the lack of manufacturing facilities and the obstacle of print duration ranked below average. An inclusive implementation of additive manufacturing could be achieved primarily through the education of dentists and other staff in dental practices. In this manner, production may be managed internally, and the implementation speed may be increased. T3 - Zweitveröffentlichungen der Universität Potsdam : Wirtschafts- und Sozialwissenschaftliche Reihe - 147 KW - 3D printing KW - prosthodontics KW - ranking type Delphi study KW - additive manufacturing KW - dentistry Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-544024 ER - TY - THES A1 - Schröder, Jakob T1 - Fundamentals of diffraction-based residual stress and texture analysis of laser powder bed fused Inconel 718 T1 - Grundlagen der beugungsbasierten Eigenspannungs- und Texturanalyse von laserstrahlgeschmolzenem Inconel 718 N2 - Additive manufacturing (AM) processes enable the production of metal structures with exceptional design freedom, of which laser powder bed fusion (PBF-LB) is one of the most common. In this process, a laser melts a bed of loose feedstock powder particles layer-by-layer to build a structure with the desired geometry. During fabrication, the repeated melting and rapid, directional solidification create large temperature gradients that generate large thermal stress. This thermal stress can itself lead to cracking or delamination during fabrication. More often, large residual stresses remain in the final part as a footprint of the thermal stress. This residual stress can cause premature distortion or even failure of the part in service. Hence, knowledge of the residual stress field is critical for both process optimization and structural integrity. Diffraction-based techniques allow the non-destructive characterization of the residual stress fields. However, such methods require a good knowledge of the material of interest, as certain assumptions must be made to accurately determine residual stress. First, the measured lattice plane spacings must be converted to lattice strains with the knowledge of a strain-free material state. Second, the measured lattice strains must be related to the macroscopic stress using Hooke's law, which requires knowledge of the stiffness of the material. Since most crystal structures exhibit anisotropic material behavior, the elastic behavior is specific to each lattice plane of the single crystal. Thus, the use of individual lattice planes in monochromatic diffraction residual stress analysis requires knowledge of the lattice plane-specific elastic properties. In addition, knowledge of the microstructure of the material is required for a reliable assessment of residual stress. This work presents a toolbox for reliable diffraction-based residual stress analysis. This is presented for a nickel-based superalloy produced by PBF-LB. First, this work reviews the existing literature in the field of residual stress analysis of laser-based AM using diffraction-based techniques. Second, the elastic and plastic anisotropy of the nickel-based superalloy Inconel 718 produced by PBF-LB is studied using in situ energy dispersive synchrotron X-ray and neutron diffraction techniques. These experiments are complemented by ex situ material characterization techniques. These methods establish the relationship between the microstructure and texture of the material and its elastic and plastic anisotropy. Finally, surface, sub-surface, and bulk residual stress are determined using a texture-based approach. Uncertainties of different methods for obtaining stress-free reference values are discussed. The tensile behavior in the as-built condition is shown to be controlled by texture and cellular sub-grain structure, while in the heat-treated condition the precipitation of strengthening phases and grain morphology dictate the behavior. In fact, the results of this thesis show that the diffraction elastic constants depend on the underlying microstructure, including texture and grain morphology. For columnar microstructures in both as-built and heat-treated conditions, the diffraction elastic constants are best described by the Reuss iso-stress model. Furthermore, the low accumulation of intergranular strains during deformation demonstrates the robustness of using the 311 reflection for the diffraction-based residual stress analysis with columnar textured microstructures. The differences between texture-based and quasi-isotropic approaches for the residual stress analysis are shown to be insignificant in the observed case. However, the analysis of the sub-surface residual stress distributions show, that different scanning strategies result in a change in the orientation of the residual stress tensor. Furthermore, the location of the critical sub-surface tensile residual stress is related to the surface roughness and the microstructure. Finally, recommendations are given for the diffraction-based determination and evaluation of residual stress in textured additively manufactured alloys. N2 - Additive Fertigungsverfahren (AM) ermöglichen die Herstellung von Metallstrukturen mit außergewöhnlicher Gestaltungsfreiheit, wobei das pulverbettbasierte Laserstrahlschmelzen (PBF-LB) eines der gängigsten dieser Verfahren darstellt. In diesem Verfahren schmilzt ein Laser ein Pulverbett schichtweise auf, um ein Bauteil mit der gewünschten Geometrie zu erzeugen. Während der Fertigung kommt es aufgrund des wiederholten Aufschmelzens und der schnellen, gerichteten Erstarrung zu hohen Temperaturgradienten, die hohe thermische Spannungen erzeugen. Einerseits können diese thermischen Spannungen während des Fertigungsprozesses zur Rissbildung oder zur Ablösung des Bauteils führen. Häufiger jedoch verbleiben große Eigenspannungen im gefertigten Bauteil als Folge der thermischen Spannungen. Diese Eigenspannungen begünstigen die Verzerrung der Bauteile und können sogar ihr vorzeitiges Versagen im Betrieb verursachen. Daher ist die Kenntnis der Eigenspannungsverteilung im Bauteil sowohl für die Prozessoptimierung als auch die strukturelle Integrität bedeutend. Beugungsbasierte Verfahren ermöglichen die zerstörungsfreie Bestimmung des Eigenspannungsfeldes. Diese Verfahren erfordern jedoch eine vorhergehende Kenntnis der Materialeigenschaften, da gewisse Annahmen getroffen werden müssen, um die Eigenspannungen genau bestimmen zu können. Zunächst müssen aus den gemessenen Abständen der Gitterebenen Gitterdehnungen berechnet werden, wozu der dehnungsfreie Referenzzustand bekannt sein muss. Weiterhin müssen die Gitterdehnungen über das Hookesche Gesetz, unter Bezugnahme der elastischen Eigenschaften, in Spannungen überführt werden. Da die meisten Kristallstrukturen durch ein anisotropes Verhalten gekennzeichnet sind, ist ihr elastisches Verhalten für jede Gitterebene spezifisch. Deshalb bedarf es bei der Nutzung monochromatischer Strahlung zur beugungsbasierten Eigenspannungsbestimmung der Kenntnis der gitterebenenspezifischen elastischen Eigenschaften. Zusätzlich ist das Wissen über die Mikrostruktur des Materials unabdingbar für eine zuverlässige Bestimmung der Eigenspannungen. Die vorliegende Arbeit präsentiert eine Reihe von Bedingungen, die für eine zuverlässige beugungsbasierte Eigenspannungsanalyse notwendig sind. Dies wird exemplarisch an einer mittels PBF-LB gefertigten Nickelbasis Superlegierung gezeigt. Einleitend wird ein Überblick der Literatur im Bereich der beugungsbasierten Eigenspannungsanalyse mit Bezug zur additiven Fertigung gegeben. Anschließend wird die elastische und plastische Anisotropie der mittels PBF-LB gefertigten Nickelbasis Superlegierung Inconel 718 durch in situ energiedispersive Synchrotron Röntgen- und Neutronenbeugung charakterisiert. Diese Methoden werden durch ex situ Untersuchungsverfahren ergänzt. So wird die Beziehung zwischen der Mikrostruktur und der Textur zur elastischen und plastischen Anisotropie hergestellt. Abschließend werden die Oberflächen-, oberflächennahen-, sowie Volumeneigenspannungen in einem texturbasierten Ansatz bestimmt. Dabei werden Unsicherheiten verschiedener Methoden zur Bestimmung der spannungsfreien Referenz diskutiert. Das mechanische Verhalten unter Zugbelastung des as-built Zustandes ist dabei durch die Textur und die zelluläre Substruktur bedingt, während es im wärmebehandelten Zustand vom Ausscheidungszustand und der geänderten Kornmorphologie bestimmt wird. Die Ergebnisse dieser Arbeit zeigen, dass die diffraktionselastischen Konstanten von der zugrundeliegenden Mikrostruktur abhängen. Für die kolumnaren Mikrostrukturen, egal ob im as-built oder wärmebehandeltem Zustand, werden die diffraktionselastischen Konstanten am besten durch die Reuss Annahme homogener Spannung beschrieben. Darüber hinaus zeigt die geringe Akkumulation intergranularer Dehnung des 311 Reflexes seine Robustheit für die beugungsbasierte Eigenspannungsanalyse. Im vorhandenen Fall ist der Unterschied zwischen texturbasierten und quasiisotropen Ansätzen zur Eigenspannungsanalyse unbedeutend. Oberflächennahe Eigenspannungsanalysen zeigen jedoch, dass verschiedene Scanstrategien zu einer Änderung in der Ausrichtung des Eigenspannungstensors führen. Weiterhin zeigt die Lage der kritischen oberflächennahen Zugeigenspannungen eine Abhängigkeit zur Oberflächenrauheit und dem Gefüge. Abschließend werden Empfehlungen zur beugungsbasierten Ermittlung und Bewertung von Eigenspannungen in texturierten additiv gefertigten Legierungen gegeben. KW - residual stress KW - diffraction KW - texture KW - mechanical behavior KW - in-situ testing KW - laser powder bed fusion KW - additive manufacturing KW - electron backscatter diffraction KW - diffraction elastic constants KW - Inconel 718 KW - Inconel 718 KW - additive Fertigung KW - Diffraktion KW - diffraktionselastische Konstanten KW - Elektronenrückstreubeugung KW - In-situ Experimente KW - Laserstrahlschmelzen KW - mechanisches Verhalten KW - Eigenspannung KW - Textur Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-621972 ER -