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  • 1.
    Näsström, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    A near-vertical approach to Laser Narrow Gap Multi-Layer Welding2020Ingår i: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 121, artikel-id 105798Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel, near-vertical approach to the usually horizontal laser Narrow Gap Multi-Layer Welding process is introduced. The process is applied to join X100 pipeline steel and studied through High Speed Imaging. The produced welded joints are compared to their horizontally welded counterparts using 3D scanning, longitudinal & perpendicular cross sections and Computed Tomography analysis. The near-vertical approach is found to be robust and produce welded joints with a uniform appearance. The top surface exhibits certain reoccurring morphological features, and variations in internal track melting boundaries are observed. Any observed cavities appear similar to those produced using the horizontal process, with the difference of their orientation. A combination of the horizontal and the near-vertical process could be beneficial; the near-vertical approach offers potential for shorter inter-layer time and the horizontal method for better surface finish than that of its counterpart. Potential benefits of, and improvements to, the near-vertical process are discussed.

  • 2.
    Haack, Maximilian
    et al.
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Kuczyk, Martin
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Seidel, André
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    López, Elena
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Leyens, Christoph
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany. Dresden University of Technology, Institute of Materials Science, Dresden, Germany.
    Comprehensive study on the formation of grain boundary serrations in additively manufactured Haynes 230 alloy2020Ingår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 160, artikel-id 110092Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recently, grain boundary serrations have been introduced in conventionally processed Haynes 230 through a slow-cooling heat treatment. The aim of this work was to utilize these heat treatments to introduce serrations in additively manufactured (Laser Metal Deposition) Haynes 230. Contrary to expectations, serrations already formed during the fast-cooling of the Laser Metal Deposition process. Electron Backscatter Diffraction was used to elucidate the underlying phenomenon for the emergence of serrations during fast-cooling. As a result, a hypothesis regarding a new mechanism responsible for the formation of grain boundary serrations was formulated. Additionally, specific characteristics of the Laser Metal Deposition process have been identified. This includes a columnar-to-equiaxed transition (CET) for slower feed rates, leading to smaller grains despite lower cooling rates; the observation of an abrupt increase in grain growth for a raised solution annealing temperature; the fact that serrations hinder uncontrolled grain growth and finally that the LMD-process leads to a finer carbide morphology compared to conventional manufacturing methods, potentially leading to an increased precipitation strengthening effect.

  • 3.
    Näsström, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, IWS, Germany.
    Kaplan, Alexander F.H.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Imperfections in narrow gap multi-layer welding: Potential causes and countermeasures2020Ingår i: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 129, artikel-id 106011Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Narrow Gap Multi-Layer Welding (NGMLW) using a laser as the main heat source and metal wire for material addition has been a growing topic of interest in the last decade. This is in part due to its potential for joining much thicker sheets of steel than what is usually considered possible when using autogenous laser welding. The process has shown great potential but improvements can still be made, e.g. through increased process control to decrease welding imperfections. Using closed-loop control, where the process is continuously monitored and regulated automatically, can help to account for variations during manufacturing. However, achieving functional closed loop control can be challenging due to limitations in data gathering and processing speeds. Important initial steps include identifying what data can be useful and how frequently this data has to be recorded. Too much data takes too long to process while too little causes risks of missing important details. In this study, 20 mm thick X80 pipeline steel sheets are joined together using this multi-layer approach; the samples are examined using 3D scanning and Computed Tomography (CT) analysis and the process is observed using High-Speed Imaging (HSI). The quality of the welded joint and welding imperfections are discussed and potential points of formation are identified. Suggestions on how to mitigate imperfections to improve the quality of the welded joint are presented, including the potential to use camera imaging for closed-loop process control and additional industrial uses of the HSI footage.

  • 4.
    Prasad, Himani Siva
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer IWS, Winterbergstrasse 28, 01277, Dresden, Germany.
    Volpp, Joerg
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander F. H.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Laser metal deposition of copper on diverse metals using green laser sources2020Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Green laser sources are advantageous in the processing of copper due to the increase of absorptivity compared with more commonly available infrared lasers. Laser metal deposition of copper with a green laser onto various substrate metals namely copper, aluminium, steel and titanium alloy was carried out and observed through high-speed imaging. The effects of process parameters such as laser power, cladding speed and powder feed rate, and material attributes such as absorptivity, surface conditions and thermal conductivity are tied together to explain the size and geometry of the melt pool as well as the fraction of the power used for melting material. The copper substrate has the smallest melt pool with a high angle, followed by aluminium, steel and titanium alloy. The incorporation times for powder grains in the melt pools vary based on the substrate materials. Its dependency on material properties, including surface tension forces, melting temperatures and material density, is discussed. Oxide skins present on melt pools can affect powder incorporation, most significantly on the aluminium substrate. The lower limits of the fraction of power irradiated on the surface used purely for melting were calculated to be 0.73%, 2.94%, 5.95% and 9.78% for the copper, aluminium, steel and titanium alloy substrates, respectively, showing a strong dependence on thermal conductivity of the substrate material. For a copper wall built, the fraction was 2.66%, much higher than a single clad on a copper substrate, due to reduced workpiece heating. The results of this paper can be transferred to other metals with low absorptivity such as gold.

  • 5.
    Tkachov, Roman
    et al.
    Institute of Materials Science, Technische Universität Dresden, Dresden, Germany. Fraunhofer-Institut für Werkstoff- und Strahltechnik (IWS), Dresden, Germany.
    Stepien, Lukas
    Fraunhofer-Institut für Werkstoff- und Strahltechnik (IWS),Dresden, Germany.
    Greifzu, Moritz
    Institute of Materials Science, Technische Universität Dresden, Dresden, Germany. Fraunhofer-Institut für Werkstoff- und Strahltechnik (IWS), Dresden, Germany.
    Kiriy, Anton
    Leibniz-Institut für Polymerforschung Dresden e.V. (IPF), Dresden, Germany.
    Kiriy, Nataliya
    Leibniz-Institut für Polymerforschung Dresden e.V. (IPF), Dresden, Germany.
    Schüler, Tilman
    Institute of Aerospace Engineering, Technische Universität Dresden, Dresden, Germany.
    Schmiel, Tino
    Institute of Aerospace Engineering, Technische Universität Dresden, Dresden, Germany.
    López, Elena
    Fraunhofer-Institut für Werkstoff- und Strahltechnik (IWS), Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer-Institut für Werkstoff- und Strahltechnik (IWS),Dresden, Germany.
    Leyens, Christoph
    Institute of Materials Science, Technische Universität Dresden, Dresden, Germany. Fraunhofer-Institut für Werkstoff- und Strahltechnik (IWS), Dresden, Germany.
    A Printable Paste Based on a Stable n-Type Poly[Ni-tto] Semiconducting Polymer2019Ingår i: Coatings, ISSN 2079-6412, Vol. 9, nr 11, artikel-id 764Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polynickeltetrathiooxalate (poly[Ni-tto]) is an n-type semiconducting polymer having outstanding thermoelectric characteristics and exhibiting high stability under ambient conditions. However, its insolubility limits its use in organic electronics. This work is devoted to the production of a printable paste based on a poly[Ni-tto]/PVDF composite by thoroughly grinding the powder in a ball mill. The resulting paste has high homogeneity and is characterized by rheological properties that are well suited to the printing process. High-precision dispenser printing allows one to apply both narrow lines and films of poly[Ni-tto]-composite with a high degree of smoothness. The resulting films have slightly better thermoelectric properties compared to the original polymer powder. A flexible, fully organic double-leg thermoelectric generator with six thermocouples was printed by dispense printing using the poly[Ni-tto]-composite paste as n-type material and a commercial PEDOT-PSS paste as p-type material. A temperature gradient of 100 K produces a power output of about 20 nW

  • 6.
    Schneider, J.
    et al.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.Department of Materials Technology, Technische Universität Dresden, Dresden, Germany.
    Seidel, A.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Gumpinger, J.
    ESA/ESTEC, European Space Research and Technology Centre, Noordwijk, The Netherlands.
    Riede, M.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Lopéz, E.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Leyens, C.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.Department of Materials Technology, Technische Universität Dresden, Dresden, Germany.
    Advanced manufacturing approach via the combination of selective laser melting and laser metal deposition2019Ingår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 31, nr 2, artikel-id 022317Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Additive manufacturing processes are frequently discussed in a competitive manner instead of being considered synergetically. This is particularly unfavorable since advanced machining processes in combination with additive manufacturing can be brought to the point that the results could not be achieved with the individual constituent processes in isolation [K. Gupta, R. F. Laubscher, and N. K. Jain, Hybrid Machining Processes—Perspectives on Machining and Finishing (Springer, New York, 2016), p. 68]. On that basis, boundary conditions from selective laser melting (SLM) and laser metal deposition (LMD) are considered in mutual contemplation [A. Seidel et al., in Proceedings of 36th International Congress on Applications of Laser & Electro-Optics, Atlanta, GA, 22–26 October 2017(Fraunhofer IWS, Dresden, 2017), pp. 6–8]. The present approach interlinks the enormous geometrical freedom of powder-bed processing with the scalability of the LMD process. To demonstrate the potential of this approach, two different strategies are pursued. Firstly, a hollow structure demonstrator is manufactured layer wise via LMD with powder and subsequently joined with geometrically complex elements produced via SLM. Afterward, possibilities for a microstructural tailoring within the joining zone via the modification of process parameters are theoretically and practically discussed. Therefore, hybrid sample materials have been manufactured and interface areas are subjected to microstructural analysis and hardness tests. The feasibility of the introduced approach has been demonstrated by both fields of observation. The process combination illustrates a comprehensive way of transferring the high geometric freedom of powder-bed processing to the LMD process. The adjustment of process parameters between both techniques seems to be one promising way for an alignment on a microstructural and mechanical scale.

  • 7.
    Kledwig, Christian
    et al.
    Development Department, Sauer GmbH LASERTEC, DMG MORI AG, Pfronten, Germany.
    Perfahl, Holger
    Development Department, Sauer GmbH LASERTEC, DMG MORI AG, Pfronten, Germany.
    Reisacher, Martin
    Development Department, Sauer GmbH LASERTEC, DMG MORI AG, Pfronten, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Bliedtner, Jens
    SciTec Department, Ernst-Abbe-Hochschule Jena, Jena, Germany.
    Leyens, Christoph
    Additive Manufacturing and Printing, Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany; Institute of Materials Science, Technische Universität Dresden, Dresden, Germany.
    Analysis of Melt Pool Characteristics and Process Parameters Using a Coaxial Monitoring System during Directed Energy Deposition in Additive Manufacturing2019Ingår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 2, artikel-id 308Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The growing number of commercially available machines for laser deposition welding show the growing acceptance and importance of this technology for industrial applications. Their increasing usage in research and production requires process stability and user-friendly handling. A commercially available DMG MORI LT 65 3D hybrid machine used in combination with a CCD-based coaxial temperature measurement system was utilized in this work to investigate what information relating to the intensity distribution of melt pool surfaces could be appropriate to draw conclusions about process conditions. In this study it is shown how the minimal required specific energy for a stable process can be determined, and it is indicated that the evolution of a plasma plume depends on thermal energy within the base material. An estimated melt pool area—calculated by the number of pixels (NOP) with intensities larger than a fixed, predefined threshold—builds the main measure in analysing images from the process camera. The melt pool area and its temporal variance can also serve as an indicator for an increased working distance

  • 8.
    Moritz, J.
    et al.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Seidel, A.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Braun, B.
    Space Structures GmbH, Berlin, Germany.
    Brandao, A.
    European Space Research and Technology Centre, ESTEC, Noordwijk, Netherlands.
    Pambaguian, L.
    European Space Research and Technology Centre, ESTEC, Noordwijk, Netherlands.
    Köhler, B.
    Fraunhofer Institute for Ceramic Technologies and Systems, Dresden, Germany.
    Barth, M.
    Fraunhofer Institute for Ceramic Technologies and Systems, Dresden, Germany.
    Riede, M.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Lopéz, E.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Leyens, C.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.Institute of Materials Science IfWW, Technische Universität Dresden, Dresden, Germany.
    Functional integration approaches via laser powder bed processing2019Ingår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 31, nr 2, artikel-id 022319Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Additive manufacturing design rules are different from those of conventional fabrication techniques. These allow geometries that would not be possible to achieve otherwise. One example of application is the integration of functional parts as part of the manufacturing process. Conceivable applications range from mechanical functions like integration of moving parts or thermodynamic functions, for example, cooling channels or incorporation of electric circuits for electrical functionalization [J. Glasschroeder, E. Prager, and M. F. Zaeh, Rapid Prototyping J. 21, 207–215 (2015)]. Nevertheless, the potential of functional integration using powder-bed processes is far from being exhausted. The present approach addresses the generation of inner cavities and internal structures of titanium-based parts or components by the use of selective laser melting. This paper focusses on the investigation of voids and cavities regarding their capabilities to add new functions to the material. To this end, comprehensive characterization is performed using destructive as well as nondestructive testing methods. These include 3D scanning, computed tomography, and surface roughness measurements as well as microscopic analysis. Voids and cavities were filled with different thermoplastic materials, followed by the qualitative assessment of the mold filling and resulting material properties. Finally, applications are derived and evaluated with respect to the field of lightweight design or damping structures.

  • 9.
    Frostevarg, Jan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Volpp, Jöerg
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Thompson, Cassidy
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Prasad, Himani Siva
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Fedina, Tatiana
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Influence of the vapour channel on processing in laser powder bed fusion2019Ingår i: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 36, s. 80-87Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Additive Manufacturing provides many opportunities to design and manufacture parts that are difficult or not possible to produce with conventional methods. In Selective Laser Melting (SLM) in powder bed fusion (PBF), melt pool dynamics and stability is dependent on a large number of factors, e.g. laser power output, power density, travel speed, reflectivity of powder bed, rapid heating and vaporization. Since travel speeds are often very fast and the laser interaction zone is small, the physical events become difficult to predict but also to observe. This work aims to describe the formation and geometrical characteristics of the vaporization zone during processing. Using a combination of theoretical descriptions, resulting material structures and a comprehensive analysis of high-speed images of the processing zone for different heat inputs and travel speeds, explanations for the dynamic melt pool behaviour are derived. The melting and pressures from processing involved moves powder particles next to it, changing the conditions for neighbouring tracks due to lack of material. These findings can provide a basis for creating more efficient and stable SLM processing, with fewer imperfections.

  • 10.
    Seidel, André
    et al.
    Fraunhofer-Institute for Material and Beam Technology, Dresden, Germany.
    Saha, Shuvra
    Fraunhofer-Institute for Material and Beam Technology, Dresden, Germany.
    Maiwald, Tim
    Fraunhofer-Institute for Material and Beam Technology, Dresden, Germany;Technische Universität Dresden, Dresden, Germany.
    Moritz, Juliane
    Fraunhofer-Institute for Material and Beam Technology, Dresden, Germany.
    Polenz, Stefan
    Fraunhofer-Institute for Material and Beam Technology, Dresden, Germany.
    Marquardt, Axel
    Fraunhofer-Institute for Material and Beam Technology, Dresden, Germany;Technische Universität Dresden, Dresden, Germany.
    Kaspar, Joerg
    Fraunhofer-Institute for Material and Beam Technology, Dresden, Germany.
    Finaske, Thomas
    Fraunhofer-Institute for Material and Beam Technology, Dresden, Germany.
    Lopez, Elena
    Fraunhofer-Institute for Material and Beam Technology, Dresden, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer-Institute for Material and Beam Technology, Dresden, Germany.
    Leyens, Christoph
    Fraunhofer-Institute for Material and Beam Technology, Dresden, Germany;Technische Universität Dresden, Dresden, Germany.
    Intrinsic Heat Treatment Within Additive Manufacturing of Gamma Titanium Aluminide Space Hardware2019Ingår i: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 71, nr 4, s. 1513-1519Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A major part of laser additive manufacturing focuses on the fabrication of metallic parts for applications in the space and aerospace sectors. Especially, the processing of the very brittle titanium aluminides can be particularly challenging because of their distinct tendency to lamellar interface cracking. In the present paper, a gamma titanium aluminide (γ-TiAl) nozzle, manufactured via electron beam melting, is extended and adapted via hybrid laser metal deposition. The presented example considers a new field of application for this class of materials and approaches the process-specific manipulation of the composition and/or microstructure via the adjustment of processing temperatures, temperature gradients and solidification conditions. Furthermore, intrinsic heat treatment is investigated for electron beam melting and laser metal deposition with powder, and the resulting influence is releated to conventional processing.

  • 11.
    Näsström, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, IWS, Dresden, Germany.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Laser enhancement of wire arc additive manufacturing2019Ingår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 31, nr 2, artikel-id 022307Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Additive manufacturing (AM) can be used for the fabrication of large metal parts, e.g., aerospace/space applications. Wire arc additivemanufacturing (WAAM) can be a suitable process for this due to its high deposition rates and relatively low equipment and operationcosts. In WAAM, an electrical arc is used as a heat source and the material is supplied in the form of a metal wire. A known disadvantageof the process is the comparably low dimensional accuracy. This is usually compensated by generating larger structures than desired andmachining away excess materials. So far, using combinations of arc in atmospheric conditions with high precision laser heat sources forAM has not yet been widely researched. Properties of the comparable cheap arc-based process, such as melt pool stability and dimensionalaccuracy, can be improved with the addition of a laser source. Within this paper, impacts of adding a laser beam to the WAAMprocess are presented. Differences between having the beam in a leading or a trailing position, relative to the wire and arc, are alsorevealed. Structures generated using the arc-laser-hybrid processes are compared to ones made using only an arc as the heat source. Bothgeometrical and material aspects are studied to determine the influences of laser hybridization, applied techniques including x ray,energy-dispersive X-ray spectroscopy, and high precision 3D scanning. A trailing laser beam is found to best improve topological capabilitiesof WAAM. Having a leading laser beam, on the other hand, is shown to affect cold metal transfer synergy behavior, promotinghigher deposition rates but decreasing topological accuracy.

  • 12.
    Greifzu, Moritz
    et al.
    Additive Manufacturing and Printing, Fraunhofer-Institut für Werkstoff- und Strahltechnik, Dresden, Germany.
    Tkachov, Roman
    Additive Manufacturing and Printing, Fraunhofer-Institut für Werkstoff- und Strahltechnik, Dresden, Germany. Institute of Materials Science, Technische Universität Dresden, Dresden, Germany.
    Stepien, Lukas
    Additive Manufacturing and Printing, Fraunhofer-Institut für Werkstoff- und Strahltechnik, Dresden, Germany.
    López, Elena
    Additive Manufacturing and Printing, Fraunhofer-Institut für Werkstoff- und Strahltechnik, Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Leyens, Christoph
    Additive Manufacturing and Printing, Fraunhofer-Institut für Werkstoff- und Strahltechnik, Dresden, Germany. Institute of Materials Science, Technische Universität Dresden, Dresden, Germany.
    Laser Treatment as Sintering Process for Dispenser Printed Bismuth Telluride Based Paste2019Ingår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 20, artikel-id 3453Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Laser sintering as a thermal post treatment method for dispenser printed p- and n-type bismuth telluride based thermoelectric paste materials was investigated. A high-power fiber laser (600 W, 1064 nm) was used in combination with a scanning system to achieve high processing speed. A Design of Experiment (DoE) approach was used to identify the most relevant processing parameters. Printed layers were laser treated with different process parameters and the achieved sheet resistance, electrical conductivity, and Seebeck coefficient are compared to tube furnace processed reference specimen. For p-type material, electrical conductivity of 22 S/cm was achieved, compared to 15 S/cm in tube furnace process. For n-type material, conductivity achieved by laser process was much lower (7 S/cm) compared to 88 S/cm in furnace process. Also, Seebeck coefficient decreases during laser processing (40–70 µV/K and −110 µV/K) compared to the oven process (251 µV/K and −142 µV/K) for p- and n-type material. DoE did not yet deliver a set of optimum processing parameters, but supports doubts about the applicability of area specific laser energy density as a single parameter to optimize laser sintering process.

  • 13.
    Riede, M.
    et al.
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Knoll, M.
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Wilsnack, C.
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Gruber, S.
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany. Institute of Materials Science, Technische Universität Dresden, Dresden, Germany.
    Cubillo, A.A.
    RUAG Space Germany GmbH, Coswig,Germany.
    Melzer, C.
    RUAG Space Germany GmbH, Coswig,Germany.
    Brandão, A.
    European Space Research and Technology Centre-ESTEC, Noordwijk, Netherlands.
    Pambaguian, L.
    European Space Research and Technology Centre-ESTEC, Noordwijk, Netherlands.
    Seidel, A.
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Lopez, E.
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany.
    Leyens, C.
    Fraunhofer Institute for Material and Beam Technology IWS, Dresden, Germany. Institute of Materials Science, Technische Universität Dresden, Dresden, Germany..
    Material characterization of AISI 316L flexure pivot bearings fabricated by additive manufacturing2019Ingår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 15, artikel-id 2426Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recently, additive manufacturing (AM) by laser metal deposition (LMD) has become a key technology for fabricating highly complex parts without any support structures. Compared to the well-known powder bed fusion process, LMD enhances manufacturing possibilities to overcome AM-specific challenges such as process inherent porosity, minor build rates, and limited part size. Moreover, the advantages aforementioned combined with conventional machining enable novel manufacturing approaches in various fields of applications. Within this contribution, the additive manufacturing of filigree flexure pivots using 316L-Si by means of LMD with powder is presented. Frictionless flexure pivot bearings are used in space mechanisms that require high reliability, accuracy, and technical cleanliness. As a contribution to part qualification, the manufacturing process, powder material, and fabricated specimens were investigated in a comprehensive manner. Due to its major impact on the process, the chemical powder composition was characterized in detail by energy dispersive X-ray spectroscopy (EDX) and inductively coupled plasma optical emission spectrometry (ICP-OES). Moreover, a profound characterization of the powder morphology and flowability was carried out using scanning electron microscopy (SEM) and novel rheological investigation techniques. Furthermore, quantitative image analysis, mechanical testing, laser scanning microscopy, and 3D shape measurement of manufactured specimens were conducted. As a result, the gained knowledge was applied for the AM-specific redesign of the flexure pivot. Finally, a qualified flexure pivot has been manufactured in a hybrid manner to subsequently ensure its long-term durability in a lifetime test bench.

  • 14.
    Näsström, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, IWS, Dresden, Germany.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Measuring the effects of a laser beam on melt pool fluctuation in arc additive manufacturing2019Ingår i: Rapid prototyping journal, ISSN 1355-2546, E-ISSN 1758-7670, Vol. 25, nr 3, s. 488-495Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose

    The steadily growing popularity of additive manufacturing (AM) increases the demand for understanding fundamental behaviors of these processes. High-speed imaging (HSI) can be a useful tool to observe these behaviors, but many studies only present qualitative analysis. The purpose of this paper is to propose an algorithm-assisted method as an intermediate to rapidly quantify data from HSI. Here, the method is used to study melt pool surface profile movement in a cold metal transfer-based (CMT-based) AM process, and how it changes when the process is augmented with a laser beam.

    Design/methodology/approach

    Single-track wide walls are generated in multiple layers using only CMT, CMT with leading and with trailing laser beam while observing the processes using HSI. The studied features are manually traced in multiple HSI frames. Algorithms are then used for sorting measurement points and generating feature curves for easier comparison.

    Findings

    Using this method, it is found that the fluctuation of the melt surface in the chosen CMT AM process can be reduced by more than 35 per cent with the addition of a laser beam trailing behind the arc. This indicates that arc and laser can be a viable combination for AM.

    Originality/value

    The suggested quantification method was used successfully for the laser-arc hybrid process and can also be applied for studies of many other AM processes where HSI is implemented. This can help fortify and expand the understanding of many phenomena in AM that were previously too difficult to measure.

  • 15.
    Mueller, Michael
    et al.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany. Technische Universität Dresden, Dresden, Germany.
    Riede, Mirko
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Eberle, Sebastian
    Kampf Telescope Optics GmbH, Munich, Germany.
    Reutlinger, Arnd
    Kampf Telescope Optics GmbH, Munich, Germany.
    Brandão, Ana D.
    European Space Research and Technology Centre, ESTEC, Noordwijk, Netherlands.
    Pambaguian, Laurent
    European Space Research and Technology Centre, ESTEC, Noordwijk, Netherlands.
    Seidel, André
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Lopéz, Elena
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Beyer, Eckhard
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany. Technische Universität Dresden, Dresden, Germany.
    Leyens, Christoph
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany. Technische Universität Dresden, Dresden, Germany.
    Microstructural, mechanical, and thermo-physical characterization of hypereutectic AlSi40 fabricated by selective laser melting2019Ingår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 31, nr 2, artikel-id 02232Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The powder bed additive manufacturing process selective laser melting (SLM) enables designers and engineers to overcome restrictions of conventional manufacturing technologies. The potential of fabricating complex lightweight structures and processing advanced materials is a key feature for enhancing further development of high performance components for space applications. Due to a high specific stiffness and a thermal expansion coefficient very close to electroless nickel, which is an advantageous optical coating material, the hypereutectic aluminum-silicon alloy AlSi40 shows great potential for the manufacturing of optical mirrors for space applications. In prior investigations, Hilpert et al.showed the feasibility to process AlSi40 by SLM [E. Hilpert and S. Risse, Materials Science & Technology Conference and Exhibition MS&T'15, Columbus, Ohio, 4–8 October 2015(Association for Iron & Steel Technology, Warrendale, PA, 2015) and E. Hilpert, “Struktur und Eigenschaften von additiv gefertigten hypereutektischen Aluminum-Siliciumlegierungen,” in Werkstoffwoche 2017, Dresden, Germany28 September 2017 (Deutsche Gesellschaft für Materialkunde e.V., Berlin, 2017)]. Nevertheless, in order to qualify this material for space applications, the manufacturing process and fabricated samples need to be thoroughly investigated in terms of microstructural, mechanical, as well as thermo-physical characterization. The authors present results of the SLM process development for manufacturing dense AlSi40 samples with a relative density above 99.50%. The effect of various process parameters, such as hatch distance, preheating, and scanning strategy, on the formation of defects was investigated by destructive [e.g., optical microscopy (OM)] and nondestructive (e.g., computed tomography) testing. In addition, the effect of several thermal post-treatments on the AlSi40 microstructure was profoundly analyzed by multiple methods such as OM, scanning electron microscopy, and energy dispersive x-ray spectroscopy analysis. Moreover, mechanical and thermo-physical testing of manufactured specimens was conducted to provide material characteristics for component design. In conclusion, the determined material properties of AlSi40 samples fabricated by SLM were compared to bulk material properties. The gained knowledge and testing data were evaluated in order to identify correlations and dependencies.

  • 16.
    Siva Prasad, Himani
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer IWS, Winterbergstrasse 28, Dresden, Germany.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powder catchment in laser metal deposition2019Ingår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 31, nr 2, artikel-id 022308Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Laser metal deposition (LMD) of Inconel 718 using a coaxial nozzle is investigated by high-speed imaging. The interaction of individualpowder grains with the laser induced melt pool surface and, finally, their catchment in the LMD track is observed. Powder catchment trendsare explained by interpreting physical phenomena, such as the melt flow and surface tension. Distinct zones for powder catchment are categorizeddepending on the position of initial interaction between powder grains and the melt pool. Particles are introduced outside the meltpool ricochet and do not attach to the clad. Particles arriving outside the laser spot, onto the solidifying skin of the melt pool, are caught,and may incorporate. Some particles may remain on the clad surface as surface roughness on the built part. Particles interacting with thelaser-irradiated region of the melt pool tend to move toward its center and readily incorporate into the melt. Quantitative analyses of highspeedvideos are carried out to measure incorporation time of powder grains in the melt pool, their velocity, and distance traveled.

  • 17.
    Seidel, A.
    et al.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Davids, A.
    Technische Universität Dresden, Dresden, Germany.
    Polenz, S.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Straubel, A.
    Technische Universität Dresden, Dresden, Germany.
    Maiwald, T.
    Technische Universität Dresden, Dresden, Germany.Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Moritz, J.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Schneider, J.
    Technische Universität Dresden, Dresden, Germany.Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Marquardt, A.
    Technische Universität Dresden, Dresden, Germany.Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Saha, S.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Riede, M.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Lopéz, E.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Leyens, C.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.Technische Universität Dresden, Dresden, Germany.
    Surface modification of additively manufactured gamma titanium aluminide hardware2019Ingår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 31, nr 2, artikel-id 022517Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A major part of additive manufacturing focuses on the fabrication of metallic parts in different fields of applications. Examples include components for jet engines and turbines and also implants in the medical sector. Titanium alloys represent a material group which is used cross-sectoral in a large number of applications. The present paper addresses the titanium aluminides in particular. These materials have a low density in combination with a comparatively high-temperature resistance [G. Sauthoff, Intermetallics (Wiley-VCH Verlag, Weinheim, Germany, 2008)]. Nevertheless, the laser material processing is rather challenging because of their distinct tendency to lamellar interface cracking. This requires tailored processing strategies and equipment [C. Leyens et al., in Ti-2015: The 13th World Conference on Titanium, Symposium 5. Intermetallics and MMCs, 16–20 August 2015, San Diego, CA (The Minerals, Metals & Materials Society, Pittsburgh, PA, 2016)]. This work focusses on tailored processing of titanium aluminides with focus on the process-dependent surface characteristics. This includes the as-built status for powder bed processing and direct laser metal deposition but also the surface modification via post and/or advanced machining. Finally, comprehensive characterization is performed using destructive as well as nondestructive testing methods. The latter includes 3D scanning, computed tomography, microscopic analysis, and, in particular, surface roughness measurements.

  • 18.
    Volpp, Joerg
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer-Institute for Material and Beam Technology IWS, Dresden, German.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Track geometry variations in selective laser melting processes2019Ingår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 31, nr 2, artikel-id 022310Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Selective laser melting processes are widely used for many industrial applications using a laser beam to melt preplaced powder materiallayer by layer to create technical parts. The building process of those structures requires remelting of adjacent tracks and layers in order toavoid cavities and achieve the joining of the new track to the previous track and layer. In order to achieve a sufficient overlap and minimizecavities, usually conservative processing parameters are chosen. A higher energy and powder usage efficiency would be achieved if knowingabout the formation process of the single tracks and their geometrical dimensions depending on the available powder. In this work, it isshown that the cross-sectional track geometry significantly varies within one layer. A simple model is developed describing the influence ofthe available powder for each track within one layer. Depending on the hatch distance, different variation patterns are observed andmodeled showing that the track variations are inherent phenomena of the process. It can be concluded that the variations of powder avail-ability can cause the geometric variations of the tracks.

  • 19.
    Polenz, S.
    et al.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Seidel, A.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Moritz, J.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Kunz, W.
    Fraunhofer Institute for Ceramic Technologies and Systems IKTS, Dresden, Germany.
    Riede, M.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Lopéz, E.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Leyens, C.
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.Technische Universität Dresden, Dresden, Germany.
    Wavelength dependent laser material processing of ceramic materials2019Ingår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 31, nr 2, artikel-id 022316Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the future, ceramic materials will find even more applications in aerospace, energy, and drive technology. Reasons for this are the comparatively low density and good long-term stability at high temperatures for applications for components exposed to high temperatures, e.g., of engines. By using increasing combustion temperatures through the use of ceramics increases the efficiency of modern drive systems [Ohnabe, Masaki, Onozuka, Miyahara, and Sasa, Compos. Part A Appl. Sci. Manuf. 30, 489–496 (1999)]. Despite the high interest of the aviation industry to increase the use of ceramic materials, the time- and energy-consuming classical production of these materials and the concomitant limiting factors in terms of shape and size are still a drawback [Krenkel, Ceramic Matrix Composites Fiber Reinforced Ceramics and their Applications (WIY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2008)]. This paper follows a new approach to producing ceramic matrix composites (CMCs). The laser material deposition (LMD) and selective laser melting techniques were used to investigate the coupling of different laser wavelengths into ceramic materials. By combining different energy sources and utilizing wavelength-dependent energy coupling, the additive manufacturing application of ceramic materials to metallic substrates was tested. With the knowledge gained from wavelength-dependent energy coupling, the potential for the production of CMCs should be demonstrated by means of LMD

  • 20.
    Seidel, André
    et al.
    Fraunhofer Institute for Material and Beam Technology.
    Straubel, Ariane
    Technische Universität Dresden.
    Finaske, Thomas
    Fraunhofer Institute for Material and Beam Technology.
    Maiwald, Tim
    Fraunhofer Institute for Material and Beam Technology.
    Polenz, Stefan
    Fraunhofer Institute for Material and Beam Technology.
    Albert, Maximillian
    Fraunhofer Institute for Material and Beam Technology.
    Näsström, Jonas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Marquardt, Alex
    Fraunhofer Institute for Material and Beam Technology.
    Riede, Mirko
    Fraunhofer Institute for Material and Beam Technology.
    Lopez, Elena
    Fraunhofer Institute for Material and Beam Technology.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology.
    Beyer, Eckhard
    Fraunhofer Institute for Material and Beam Technology.
    Leyens, Christoph
    Fraunhofer Institute for Material and Beam Technology.
    Added value by hybrid additive manufacturing and advanced manufacturing approaches2018Ingår i: LIA Today, Vol. 26, nr 2, s. 6-8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to lead to a competitive advantage, there is the need to carefully consider the pros and cons of state-of-the-art manufacturing techniques. This is frequently carried out in a competitive manner, but can also be done in a complementary way. This complementary approach is often used for the processing of difficult-to-machine materials with particular regard to high-tech parts or components. Hybrid machining processes or, more general, advanced machining processes can be brought to the point that the results would not be possible with the individual constituent processes in isolation [Hybrid Machining Processes Perspectives on Machining and Finishing (Springer International Publishing AG, 2016)]. Hence, the controlled interaction of process mechanisms and/or energy sources is frequently applied for a significant increase of the process performance [Advanced Machining Processes of Metallic Materials: Theory, Modelling, and Applications, 2nd ed. (2016)] and will be addressed within the present paper. A via electron beam melting manufactured gamma titanium aluminide nozzle is extended and adapted. This is done via hybrid laser metal deposition. The presented approach considers critical impacts like processing temperatures, temperature gradients, and solidification conditions with particular regard to crucial material properties like the phenomena of lamellar interface cracking [Laser-Based Manufacturing of Components using Materials with High Cracking Susceptibility (Laser Institute of America–LIA), pp. 586–592; Ti-2015: The 13th World Conference on Titanium, Symposium 5]. Furthermore, selected destructive and non-destructive testing is performed in order to prove the material properties. Finally, the results will be evaluated. This will also be done in the perspective of other applications.

  • 21.
    Seidel, André
    et al.
    Fraunhofer Institute for Material and Beam Technology.
    Straubel, Ariane
    Technische Universität Dresden.
    Finaske, Thomas
    Fraunhofer Institute for Material and Beam Technology.
    Maiwald, Tim
    Fraunhofer Institute for Material and Beam Technology.
    Polenz, Stefan
    Fraunhofer Institute for Material and Beam Technology.
    Albert, Maximillian
    Fraunhofer Institute for Material and Beam Technology.
    Näsström, Jonas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Marquardt, Alex
    Fraunhofer Institute for Material and Beam Technology.
    Riede, Mirko
    Fraunhofer Institute for Material and Beam Technology.
    Lopez, Elena
    Fraunhofer Institute for Material and Beam Technology.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology.
    Beyer, Eckhard
    Fraunhofer Institute for Material and Beam Technology.
    Leyens, Christoph
    Fraunhofer Institute for Material and Beam Technology.
    Added value by hybrid additive manufacturing and advanced manufacturing approaches2018Ingår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 30, nr 3, artikel-id 032301Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to lead to a competitive advantage, there is the need to carefully consider the pros and cons of state-of-the-art manufacturing techniques. This is frequently carried out in a competitive manner, but can also be done in a complementary way. This complementary approach is often used for the processing of difficult-to-machine materials with particular regard to high-tech parts or components. Hybrid machining processes or, more general, advanced machining processes can be brought to the point that the results would not be possible with the individual constituent processes in isolation [Hybrid Machining Processes Perspectives on Machining and Finishing (Springer International Publishing AG, 2016)]. Hence, the controlled interaction of process mechanisms and/or energy sources is frequently applied for a significant increase of the process performance [Advanced Machining Processes of Metallic Materials: Theory, Modelling, and Applications, 2nd ed. (2016)] and will be addressed within the present paper. A via electron beam melting manufactured gamma titanium aluminide nozzle is extended and adapted. This is done via hybrid laser metal deposition. The presented approach considers critical impacts like processing temperatures, temperature gradients, and solidification conditions with particular regard to crucial material properties like the phenomena of lamellar interface cracking [Laser-Based Manufacturing of Components using Materials with High Cracking Susceptibility (Laser Institute of America–LIA), pp. 586–592; Ti-2015: The 13th World Conference on Titanium, Symposium 5]. Furthermore, selected destructive and non-destructive testing is performed in order to prove the material properties. Finally, the results will be evaluated. This will also be done in the perspective of other applications.

  • 22.
    Seidel, André
    et al.
    Fraunhofer-Institute for Material and Beam Technology, Dresden, Germany.
    Finaske, Thomas
    Fraunhofer-Institute for Material and Beam Technology, Dresden, Germany.
    Straubel, Ariane
    Technische Universität Dresden, Dresden, Germany .
    Wendrock, Horst
    Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, Dresden, Germany .
    Maiwald, Tim
    Fraunhofer-Institute for Material and Beam Technology, Dresden, Germany.
    Riede, Mirko
    Fraunhofer-Institute for Material and Beam Technology, Dresden, Germany.
    Lopez, Elena
    Fraunhofer-Institute for Material and Beam Technology, Dresden, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer-Institute for Material and Beam Technology, Dresden, Germany.
    Leyens, Christoph
    Fraunhofer-Institute for Material and Beam Technology, Dresden, Germany.
    Additive Manufacturing of Powdery Ni-Based Superalloys Mar-M-247 and CM 247 LC in Hybrid Laser Metal Deposition2018Ingår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 49, nr 9, s. 3812-3830Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present paper addresses the phenomena of hot cracking of nickel-based superalloys in the perspective of hybrid Laser Metal Deposition (combined application of induction and laser). This includes an extract of relevant theoretical considerations and the deduction of the tailored approach which interlinks material–scientific aspects with state-of-the-art manufacturing engineering. The experimental part reflects the entire process chain covering the manufacturing strategy, important process parameters, the profound analysis of the used materials, the gradual process development, and the corresponding hybrid manufacture of parts. Furthermore, hot isostatic pressing and thermal treatment are addressed as well as tensile testing at elevated temperatures. Further investigations include X-ray CT measurements, electron backscattered diffraction (EBSD), and scanning electron microscopy (SEM) as well as light optical microscope evaluation. The fundamental results prove the reliable processibility of the high-performance alloys Mar-M-247 and Alloy 247 LC and describe in detail the process inherent microstructure. This includes the grain size and orientation as well as the investigation of size, shape, and distribution of the γ′ precipitates and carbides. Based on these findings, the manufacturing of more complex demonstrator parts with representative dimensions is addressed as well. This includes the selection of a typical application, the transfer of the strategy, as well as the proof of concept.

  • 23.
    Mishra, Pragya
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Ilar, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Energy efficiency contributions and losses during selective laser melting2018Ingår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 30, nr 3, artikel-id 032304Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Selective Laser Melting technique, SLM, requires remelting of adjacent tracks to avoid cavities and other imperfections. Usually, very conservative process parameters are chosen to avoid imperfections, resulting in a low building rate. The process efficiency relates the energy required for the generation of a new track to the laser beam power. For SLM this efficiency is determined by the process parameters, specifically hatch distance, layer depth and scanning speed, independent of the resulting process mechanisms. For SLM the process efficiency often very low, typically 2‑20%. Apart from beam reflection losses of normally 50-60%, significant energy losses result from the remelting of surrounding layers. Some areas can even experience multiple remelting cycles. Further losses originate inevitably from substrate heating. A simplified mathematical model of the track cross section and the corresponding layer overlap geometry has been developed, to analyze the different loss contributions from remelting with respect to the process parameters. The model explains why increasing the hatch distance or the layer depth proportionally increases the process efficiency. However, these increases are limited by cavity formation. The cross section of the overlapping tracks generated by SLM can be regarded as an experimental fingerprint linked to the process conditions. The track cross section geometries can significantly fluctuate, in terms of area and coordinate position. The fluctuations require additional reduction of the hatch distance or layer depth, to ensure robust, cavity-free processing. Examples are presented for stainless steel where a 180 W laser beam has led to a process efficiency of 5-11%, proportional to a hatch distance that was increased from 50 to 110 µm, for 40 µm powder layer depth, at a speed of 50 m/min.

  • 24.
    Brueckner, Frank
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology.
    Riede, Mirko
    Fraunhofer Institute for Material and Beam Technology.
    Mûller, Michael
    Fraunhofer Institute for Material and Beam Technology.
    Marquardt, Alex
    Fraunhofer Institute for Material and Beam Technology.
    Willner, Robin
    Fraunhofer Institute for Material and Beam Technology.
    Seidel, André
    Fraunhofer Institute for Material and Beam Technology.
    Lopez, Elena
    Fraunhofer Institute for Material and Beam Technology.
    Leyens, Christoph
    Fraunhofer Institute for Material and Beam Technology.
    Beyer, Eckhard
    Fraunhofer Institute for Material and Beam Technology.
    Enhanced manufacturing possibilities using multi-materials in laser metal deposition2018Ingår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 30, nr 3, artikel-id 032308Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Additive manufacturing (AM) addresses various benefits as the buildup of complex shaped parts, the possibility of functional integration, reduced lead times or the use of difficult machinable materials compared to conventional manufacturing possibilities. Beside these advantages, the use of more than one material in a component would strongly increase the field of applications in typical AM branches as energy, aerospace, or medical technology. By means of multi-material buildups, cost-intensive alloys could be only used in high-loaded areas of the part, whereas the remaining part could be fabricated with cheaper compositions. The selection of combined materials strongly depends on the requested thermophysical but also mechanical properties. Within this contribution, examples (e.g., used in the turbine business) show how alloys can be arranged to fit together, e.g., in terms of a well-chosen coefficient of thermal expansion. As can be seen in nature, the multi-material usage can be characterized by sharp intersections from one material to the other (e.g., in case of a thin corrosion protection), but also by graded structures enabling a smoother material transition (e.g., in case of dissimilar materials which are joined together without defects). The latter is shown for an example from aerospace within this paper. Another possibility is the simultaneous placement of several materials, e.g., hard carbide particles placed in a more ductile matrix composition. These particles can be varied in size (e.g., TiC versus WC). Also the ratio between carbides and matrix alloy can be adjusted depending on its application. Especially, nozzle-based free form fabrication technologies, e.g., laser metal deposition, enable the utilization of more than one material. Within this contribution, possibilities to feed more than one filler material are demonstrated. In addition, results of multi-material processes are shown. Finally, this work focuses on different (potential) applications, mainly on power generation, but also for medical technology or wear resistant components.

  • 25.
    Brueckner, Frank
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology.
    Riede, Mirko
    Fraunhofer Institute for Material and Beam Technology.
    Mûller, Michael
    Fraunhofer Institute for Material and Beam Technology.
    Marquardt, Alex
    Fraunhofer Institute for Material and Beam Technology.
    Willner, Robin
    Fraunhofer Institute for Material and Beam Technology.
    Seidel, André
    Fraunhofer Institute for Material and Beam Technology.
    Lopez, Elena
    Fraunhofer Institute for Material and Beam Technology.
    Leyens, Christoph
    Fraunhofer Institute for Material and Beam Technology.
    Beyer, Eckhard
    Fraunhofer Institute for Material and Beam Technology.
    Enhanced Manufacturing Possibilities Using Multi-Materials: in Laser Metal Deposition2018Ingår i: LIA Today, Vol. 26, nr 2, s. 10-12Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Additive manufacturing (AM) addresses various benefits as the buildup of complex shaped parts, the possibility of functional integration, reduced lead times or the use of difficult machinable materials compared to conventional manufacturing possibilities. Beside these advantages, the use of more than one material in a component would strongly increase the field of applications in typical AM branches as energy, aerospace, or medical technology. By means of multi-material buildups, cost-intensive alloys could be only used in high-loaded areas of the part, whereas the remaining part could be fabricated with cheaper compositions. The selection of combined materials strongly depends on the requested thermophysical but also mechanical properties. Within this contribution, examples (e.g., used in the turbine business) show how alloys can be arranged to fit together, e.g., in terms of a well-chosen coefficient of thermal expansion. As can be seen in nature, the multi-material usage can be characterized by sharp intersections from one material to the other (e.g., in case of a thin corrosion protection), but also by graded structures enabling a smoother material transition (e.g., in case of dissimilar materials which are joined together without defects). The latter is shown for an example from aerospace within this paper. Another possibility is the simultaneous placement of several materials, e.g., hard carbide particles placed in a more ductile matrix composition. These particles can be varied in size (e.g., TiC versus WC). Also the ratio between carbides and matrix alloy can be adjusted depending on its application. Especially, nozzle-based free form fabrication technologies, e.g., laser metal deposition, enable the utilization of more than one material. Within this contribution, possibilities to feed more than one filler material are demonstrated. In addition, results of multi-material processes are shown. Finally, this work focuses on different (potential) applications, mainly on power generation, but also for medical technology or wear resistant components.

  • 26.
    Lopez, Elena
    et al.
    Fraunhofer Institute for Material and Beam Technology.
    Felgueiras, Tomás
    Fraunhofer Institute for Material and Beam Technology.
    Crunert, Christian
    Fraunhofer Institute for Material and Beam Technology.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology.
    Riede, Mirko
    Fraunhofer Institute for Material and Beam Technology.
    Seidel, André
    Fraunhofer Institute for Material and Beam Technology.
    Marquardt, Alex
    Fraunhofer Institute for Material and Beam Technology.
    Leyens, Christoph
    Fraunhofer Institute for Material and Beam Technology.
    Beyer, Eckhard
    Fraunhofer Institute for Material and Beam Technology.
    Evaluation of 3D-printed parts by means of high-performance computer tomography2018Ingår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 30, nr 3, artikel-id 032307Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Conventional tactile and optical testing methods are not capable to detect complex inner geometries or complex surface shapes. Detecting porosities in parts is also not possible with those nondestructive methods. Among other material parameters, geometrical accuracy is essential to determine part's quality. Additive manufacturing processes also have to be optimized regarding geometry deviations caused by distortion or unfavorable orientation in the build chamber. For additive manufactured parts that incorporate previously mentioned features, high-performance computer tomography is the more suitable nondestructive testing method. Components of different materials such as plastics, ceramics, composites, or metals can be completely characterized. This nondestructive testing method was used for porosity analysis regarding the shape and local distribution of pores in an additive manufactured part to find correlations concerning the most suitable process conditions. The measured part data were also compared to original CAD files to determine zones of deviation and apply specific process strategies to avoid distortion. This paper discusses the results of integrating high-performance computer tomography (power: 500 W, max. part size: Ø 300 mm, 300 × 430 mm2) in a productionlike environment of additively manufactured parts for a wide range of technologies (i.e., electron beam melting and selective laser melting). I. INTRODUCTION

  • 27.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Hybrid additive manufacturing of gamma titanium aluminide space hardware2018Konferensbidrag (Refereegranskat)
  • 28.
    Volpp, Jörg
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Prasad, Himani Siva
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Riede, M.
    Fraunhofer-Institute for Material and Beam Technology IWS, Winterbergstr. 28, 01277 Dresden, Germany.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer-Institute for Material and Beam Technology IWS, Winterbergstr. 28, 01277 Dresden, Germany.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powder particle attachment mechanisms onto liquid material2018Ingår i: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 74, s. 140-143Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to achieve high powder and energy efficiencies of Direct Metal Deposition processes knowledge about the basic effects of the interaction of the particle on the liquid surface is mandatory. Characteristic zones on the melt pool surface were identified in high-speed images. In the melt pool area around the center of the laser beam illumination, particles immediately enter into the melt pool while in its vicinity the particles float on the melt pool until they incorporate. Closer to the solidification line, particles rest on the liquid surface and remain as surface roughness on the track after solidification.

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