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  • 1.
    Ahmadzadeh, Farzaneh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Lundberg, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Strömberg, Thomas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Multivariate process parameter change identification by neural network2013Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 69, nr 9-12, s. 2261-2268Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Whenever there is an out-of-control signal in process parameter control charts, maintenance engineers try to diagnose the cause near the time of the signal which is not always lead to prompt identification of the source(s) of the out-of-control condition and this in some cases yields to extremely high monetary loses for manufacture owner. This paper applies multivariate exponentially weighted moving average (MEWMA) control charts and neural networks to make the signal identification more effective. The simulation of this procedure shows that this new control chart can be very effective in detecting the actual change point for all process dimension and all shift magnitudes considered. This methodology can be used in manufacturing and process industries to predict change points and expedite the search for failure causing parameters, resulting in improved quality at reduced overall cost. This research shows development of MEWMA by usage of neural network for identifying the step change point and the variable responsible for the change in the process mean vector.

  • 2.
    Bektas, Oguz
    et al.
    Warwick Manufacturing Group, University of Warwick, Coventry, UK.
    Jones, Jeffrey A.
    Warwick Manufacturing Group, University of Warwick, Coventry, UK.
    Sankararaman, Shankar
    Data Science and Analytics Manager,Pricewaterhouse Cooper, San Jose, USA.
    Roychoudhury, Indranil
    Stinger Ghaffarian Technologies, Inc.NASA Ames Research Center, Moffett Field, USA.
    Goebel, Kai
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik. NASA Ames Research Center, Moffett Field, USA.
    A neural network filtering approach for similarity-based remaining useful life estimation2019Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 101, nr 1-4, s. 87-103Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The role of prognostics and health management is ever more prevalent with advanced techniques of estimation methods. However, data processing and remaining useful life prediction algorithms are often very different. Some difficulties in accurate prediction can be tackled by redefining raw data parameters into more meaningful and comprehensive health level indicators that will then provide performance information. Proper data processing has a significant importance on remaining useful life predictions, for example, to deal with data limitations or/and multi-regime operating conditions. The framework proposed in this paper considers a similarity-based prognostic algorithm that is fed by the use of data normalisation and filtering methods for operational trajectories of complex systems. This is combined with a data-driven prognostic technique based on feed-forward neural networks with multi-regime normalisation. In particular, the paper takes a close look at how pre-processing methods affect algorithm performance. The work presented herein shows a conceptual prognostic framework that overcomes challenges presented by short-term test datasets and that increases the prediction performance with regards to prognostic metrics.

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  • 3.
    Bergström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Edlund, Ove
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Söderkvist, Inge
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Repeated surface registration for on-line use2011Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 54, nr 5-8, s. 677-689Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We consider the problem of matching sets of 3D points from a measured surface to the surface of a corresponding computer-aided design (CAD) object. The problem arises in the production line where the shape of the produced items is to be compared on-line with its pre-described shape. The involved registration problem is solved using the iterative closest point (ICP) method. In order to make it suitable for on-line use, i.e., make it fast, we pre-process the surface representation of the CAD object. A data structure for this purpose is proposed and named Distance Varying Grid tree. It is based on a regular grid that encloses points sampled from the CAD surfaces. Additional finer grids are added to the vertices in the grid that are close to the sampled points. The structure is efficient since it utilizes that the sampled points are distributed on surfaces, and it provides fast identification of the sampled point that is closest to a measured point. A local linear approximation of the surface is used for improving the accuracy. Experiments are done on items produced for the body of a car. The experiments show that it is possible to reach good accuracy in the registration and decreasing the computational time by a factor 700 compared with using the common kd-tree structure.

  • 4.
    Bunaziv, I.
    et al.
    Norwegian University of Science and Technology, Trondheim, Norway.
    Akselsen, O.M.
    Norwegian University of Science and Technology, Trondheim, Norway; SINTEF Industry, Trondheim, Norway.
    Frostevarg, Jan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Application of laser-arc hybrid welding of steel for low-temperature service2019Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 102, nr 5-8, s. 2601-2613Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Laser-arc hybrid welding (LAHW) is more often used in shipbuilding and oil and gas industries in recent years. Its popularity arises due to many advantages compared to conventional arc welding processes. The laser beam source is used to achieve much higher penetration depths. By adding filler wire to the process area, by means of an arc source, the mechanical properties can be improved, e.g. higher toughness at low temperatures. Therefore, LAHW is a perspective process for low-temperature service. Applicability of LAHW is under concern due to process stability and mechanical properties related to heterogeneous filler wire distribution through the whole weld metal in deep and narrow joints. This can cause reduced mechanical properties in the weld root as well as problems with solidification cracking. The fast cooling rate in the root provides hard and brittle microconstituents lowering toughness at low temperatures. Numerical simulations and experimental observations showed that an increase in heat input from the laser beam is an effective way to reduce the cooling rate, which is also possible by applying preheating.

  • 5.
    Bunaziv, Ivan
    et al.
    Norwegian University of Science and Technology, Trondheim, Norway.
    Akselsen, Odd M.
    Norwegian University of Science and Technology, Trondheim, Norway; SINTEF Industry, Trondheim, Norway.
    Frostevarg, Jan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Correction to: Application of laser-arc hybrid welding of steel for low-temperature service2019Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 102, nr 5-8, s. 2615-2615Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    The original version of this article contained several mistakes. Due to technical problems at the typesetter, author corrections were not carried out. The original article has been corrected.

  • 6.
    Bunaziv, Ivan
    et al.
    Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology, Trondheim.
    Frostevarg, Jan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Akselsen, Odd M.
    Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology, Trondheim.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    The penetration efficiency of thick plate laser-arc hybrid welding2018Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 97, nr 5-8, s. 2907-2919Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Double-sided fiber laser-arc hybrid welding was used to join 45 mm thick high strength steel over a wide range of parameters in order to investigate the efficiency of the process. Air gap size, I- and Y-groove type preparation, pulsed and cold metal transfer pulsed arc modes, arc-laser setup, and travel speeds were compared, and in all cases, sufficient filler material was provided to fully fill the gap. The welds were investigated using high speed imaging and cross-sectional analysis to identify penetration depths, morphology, and imperfections. Larger joint air gaps were found to contribute most to weld penetration depth. Surprisingly, increased line energy decreased penetration efficiency in most cases. The laser-arc interdistance was also investigated, revealing an arc size and melt flow dependency for achieving higher penetration depth for a leading arc. It was found that, although penetration can be optimized, solidification cracking can be a limiting factor in the application of deep penetration hybrid welding for thick steel section joining.

  • 7.
    Moritz, Juliane
    et al.
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    Seidel, André
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    Kopper, Michael
    Westsächsische Hochschule Zwickau, Dr.-Friedrichs-Ring 2A, 08056, Zwickau, Germany.
    Bretschneider, Jörg
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    Gumpinger, Johannes
    ESA/ESTEC, European Space Research and Technology Center, 2201, Noordwijk, AZ, Netherlands.
    Finaske, Thomas
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    Riede, Mirko
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    Schneeweiß, Michael
    Westsächsische Hochschule Zwickau, Dr.-Friedrichs-Ring 2A, 08056, Zwickau, Germany.
    López, Elena
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    Brückner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany.
    Leyens, Christoph
    Fraunhofer Institute for Material and Beam Technology, Winterbergstraße 28, Dresden, Germany. Technische Universität Dresden, Helmholtzstr. 7, 01069, Dresden, Germany.
    Rohr, Thomas
    ESA/ESTEC, European Space Research and Technology Center, 2201, Noordwijk, AZ, Netherlands.
    Ghidini, Tommaso
    ESA/ESTEC, European Space Research and Technology Center, 2201, Noordwijk, AZ, Netherlands.
    Hybrid manufacturing of titanium Ti-6Al-4V combining laser metal deposition and cryogenic milling2020Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 107, nr 7-8, s. 2995-3009Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hybrid manufacturing, which, e.g., combines additive manufacturing with conventional machining processes, can be a way of overcoming limitations currently encountered in additive manufacturing. Cryogenic milling might be a viable option for hard-to-cut materials, as it leaves a contamination-free surface and can increase surface quality and tool life compared to conventional cooling concepts. In this study, the influence of cryogenic milling with carbon dioxide on titanium Ti-6Al-4V specimens manufactured with laser metal deposition (LMD) was investigated regarding tool wear and surface integrity in comparison to dry machining and machining with cooling lubricants. Moreover, additional layers of material were deposited on top of conventionally and cryogenically machined surfaces by means of LMD. The interface zone was then examined for defects. The milling process was closely monitored by means of thermal and high-speed imaging. Optical and tactile surface analysis provided evidence that lower roughness values and improved surface qualities could be obtained with cryogenic machining in comparison to dry machining. Moreover, significantly less tool wear was observed when a cryogenic cooling medium was applied. Although the utilization of conventional cooling lubricants resulted in satisfying surface qualities, substantial residual contamination on the milled surface was detected by means of fluorescence analysis. These contaminants are suspected to cause defects when the next layer of material is deposited. This is supported by the fact that pores were found in the weld bead applied on top of the milled specimens by means of LMD. Conversely, cryogenic machining resulted in very clean surfaces due to the residue-free evaporation of the coolant. Hence, a good metallurgical bonding between the weld bead and the milled substrate could be achieved. The results indicate the great potential of cryogenic milling in hybrid manufacturing, especially in terms of intermediate machining, as it provides residue-free surfaces for subsequent material deposition without an additional cleaning step and can significantly prolongate tool life.

  • 8.
    Neikter, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Huang, A.
    Monash Centre for Additive Manufacturing, Monash University, Melbourne, Australia. School of Materials Science and Engineering, University of Shanghai for Science and Technology, Shanghai, China.
    Wu, X.
    Monash Centre for Additive Manufacturing, Monash University, Melbourne, Australia.
    Microstructural characterization of binary microstructure pattern in selective laser-melted Ti-6Al-4V2019Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 104, nr 1-4, s. 1381-1391Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Selective laser melting (SLM) is an additive manufacturing process that offers efficient manufacturing of complex parts with good mechanical properties. For SLM, process parameters and post-processing are of importance as they affect the microstructure and consequently the mechanical properties. A feature in the microstructure, which is formed in SLM due to the fast cooling rate, is a binary microstructure pattern (BMP). The BMP is found in the horizontal plane and is formed with various laser scan angles between adjacent layers. The easiest distinguishable strategy is 90°, which renders a shape similar to a chessboard. In this work, the BMP phenomenon was investigated in detail and a microstructural characterization was performed on the fine microstructure zone (FMZ) that separates the coarse microstructure zones (CMZ), by using light optical and scanning electron microscopes (SEM) that were equipped with electron backscattered (EBSD) and energy dispersive x-ray spectroscopy (EDS) detectors. Moreover, the effect of the process parameter hatch distance on the BMP was investigated and the overlapping between neighboring scan tracks in SLM was found to influence the size of the BMP, while the thickness of the FMZ remained constant. Different post-SLM heat treatments were performed and it was shown that the BMP retained unless the heat treatment temperature reached above the β transus temperature. EBSD and β grain reconstruction were performed as well to reveal the columnar β grain orientations. The result showed that each CMZ and FMZ originates from a respective parent β grains.

  • 9.
    Odenberger, Eva-Lis
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik. Division Materials and Production, RISE IVF ABRISE Research Institutes of Sweden, Olofström.
    Pederson, Robert
    Division of Subtractive and Additive Manufacturing, University West, Trollhättan.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Finite element modeling and validation of springback and stress relaxation in the thermo-mechanical forming of thin Ti-6Al-4V sheets2019Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 104, nr 9-12, s. 3439-3455Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, a hot forming procedure is developed using computer-aided engineering (CAE) to produce thin Ti-6Al-4V sheet components in an effective way. Traditional forming methods involve time- and cost-consuming furnace heating and subsequent hot sizing steps. A material model for finite element (FE) analyses of sheet metal forming and springback at elevated temperatures in Ti-6Al-4V is calibrated and evaluated. The anisotropic yield criterion proposed by Barlat et al. 2003 is applied, and the time- and temperature-dependent stress relaxation behavior for elastic and inelastic straining are modeled using a Zener–Wert–Avrami formulation. Thermo-mechanical uniaxial tensile tests, a biaxial test, and uniaxial stress relaxation tests are performed and used as experimental reference to identify material model parameters at temperatures up to 700 °C. The hot forming tool setup is manufactured and used to produce double-curved aero engine components at 700 °C with different cycle times for validation purposes. Correlations between the predicted and measured responses such as springback and shape deviation show promising agreement, also when the forming and subsequent holding time was as low as 150 s. The short cycle time resulted in elimination of a detectable alpha case layer. Also, the tool surface coating extends the tool life in combination with a suitable lubricant. 

  • 10.
    Olaogun, O
    et al.
    Department of Mechanical Engineering Science University of Johannesburg, Johannesburg, South Africa;Department of Mechanical Engineering, Kwara State University, Malete, Nigeria.
    Edberg, Jonas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oluwole, O. O.
    Department of Mechanical Engineering, University of Ibadan, Ibadan, Nigeria.
    Akinlabi, E.T
    Department of Mechanical Engineering Science, University of Johannesburg, Johannesburg, South Africa.
    Heat transfer in cold rolling process of AA8015 alloy: a case study of 2-D FE simulation of coupled thermo-mechanical modeling2019Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 100, nr 9-12, s. 2617-2627Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The finite element method (FEM) is one of the most applicable mathematical analytic methods of rolling processes and is also an efficient method for analyzing coupled heat transfer. Thermal analysis of cold rolling process is not frequently used due to the widespread assumption of insignificant impact during rolling process. This research focuses on the development of coupled thermo-mechanical 2-D FE model analysis approach to study the thermal influence and varying coefficient of friction during the industrial cold rolling process of AA8015 aluminum alloy. Both deformable-rigid and deformable-deformable rigid contact algorithms were examined in the 2-D FE model. Findings revealed that temperature distribution in the roll bite rises steadily in a stepwise manner. The deformable-deformable contact algorithm is the best investigations of thermal behavior of the rolled metal and work rolls necessary for typical application in work roll design. The predicted roll separating force is validated with industrial measurements.

  • 11.
    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 1433-3015, Vol. 107, nr 3-4, s. 1559-1568Artikel 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.

  • 12.
    Pérez Caro, Lluís
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik. Division of Materials and Production, RISE IVF AB, Vällaregatan 30, SE-293 38, Olofström, Sweden.
    Odenberger, Eva-Lis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik. Division of Materials and Production, RISE IVF AB, Vällaregatan 30, SE-293 38, Olofström, Sweden.
    Schill, Mikael
    DYNAmore Nordic AB, Brigadgatan 5, SE-587 58, Linköping, Sweden.
    Steffenburg-Nordenström, Joachim
    GKN Aerospace Engine Systems Sweden, SE-461 38, Trollhättan, Sweden.
    Niklasson, Fredrik
    GKN Aerospace Engine Systems Sweden, SE-461 38, Trollhättan, Sweden.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Correction to: Prediction of shape distortions during forming and welding of a double-curved strip geometry in alloy 7182020Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 107, nr 7-8, s. 2983-2983Artikel i tidskrift (Övrigt vetenskapligt)
  • 13.
    Pérez Caro, Lluís
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik. Division of Materials and Production, RISE IVF AB, Vällaregatan 30, SE-293 38, Olofström, Sweden.
    Odenberger, Eva-Lis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik. Division of Materials and Production, RISE IVF AB, Vällaregatan 30, SE-293 38, Olofström, Sweden.
    Schill, Mikael
    DYNAmore Nordic AB, Brigadgatan 5, SE-587 58, Linköping, Sweden.
    Steffenburg-Nordenström, Joachim
    GKN Aerospace Engine Systems Sweden, SE-461 38, Trollhättan, Sweden.
    Niklasson, Fredrik
    GKN Aerospace Engine Systems Sweden, SE-461 38, Trollhättan, Sweden.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Prediction of shape distortions during forming and welding of a double-curved strip geometry in alloy 7182020Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 107, nr 7-8, s. 2967-2981Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The finite-element method (FEM) has considerably contributed to the development of more advanced manufacturing methods for metal structures. The prediction of the final shape of a component is of great interest to the manufacturing industry. In addition to its inherent difficulties, the presence of various types of processes in the manufacturing chain may dramatically increase the level of demand. Therefore, including all steps of the manufacturing process in the simulations is key to being successful. This has been done for a long time in the stamping industry, which involves sequences of forming, trimming, and springback. However, more complex manufacturing procedures, that include assembling of formed parts with forgings and castings via welding, have been modeled with simplifications, resulting in a reduced prediction accuracy. This hinders the compensation of accumulated shape distortions based on the simulation results. One such example is the fabrication of aero-engine structures, in which the history from the forming procedure has not been considered in subsequent welding and heat treatment analyses. In the present study, a double-shaped part manufactured from alloy 718 is formed at 20 °C and laser-welded using the bead-on-plate procedure. The coupling of different manufacturing analyses, including cold forming, trimming, result mapping, welding, cooling, and springback, is achieved using LS-DYNA. Additionally, the effect of adding the GISSMO damage model in the forming simulation is studied. The results of the forming analysis are used as inputs for the material model *MAT_CWM in the welding simulation. The anisotropic thermomechanical properties of alloy 718 are determined at temperatures up to 1000 °C. Encouraging agreement is found between the model predictions and the results of forming and welding tests. The findings underscore the importance of including the material history and accurate process conditions along the manufacturing chain to both the prediction accuracy of shape distortions, and to the potential of the industry.

  • 14.
    Volpp, Joerg
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Behavior of powder particles on melt pool surfaces2019Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 102, nr 5-8, s. 2201-2210Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Additive Manufacturing is in progress to change the production and manufacturing environments and possibilities; however, thecomplex processes taking place are not completely understood yet. A better understanding of the incorporation mechanism of theparticles into the melt pool during blown powder processes could lead to methods to increase the powder and energy efficiency.Therefore, the incorporation mechanism was investigated in experiments and simulation. High-speed images made it possible toobserve the behavior of single particles on the melt pool. A model based on the temperature-dependent surface tension/energydifference between the particle and the melt pool calculated the time until particle incorporation. It was shown that the surfacetension characteristics during particle heating can even lift the particle from the melt pool. The calculated wetting behavior incombination with high kinetic energies should lead to an immediate immersion of the particle into the melt pool. Since observationsdo not show this behavior, it is concluded that the surface tension plays a role in the incorporation mechanism, but othereffects like the occurrence of oxide layers or additional particle heating by the laser beam seem to lead to different mechanismsand heat conductions to support an earlier incorporation.

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  • 15.
    Volpp, Joerg
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Dewi, Handika Sandra
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Fischer, Andreas
    Institute of Materials Engineering, Metallic Materials, University of Kassel, 34125, Kassel, Germany.
    Niendorf, Thomas
    Institute of Materials Engineering, Metallic Materials, University of Kassel, 34125, Kassel, Germany.
    Influence of complex geometries on the properties of laser-hardened surfaces2020Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 107, nr 9-10, s. 4255-4260Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Laser surface hardening provides for many advantages in terms of flexible production due to very localized and controlled energy input into the material. Laser processing offers the possibility to treat surfaces in order to locally strengthen the areas that are prone to fatigue cracking. It is well known that laser energy absorption depends on many parameters, e.g., the surface structure and the surface orientation. The incident angle of the laser beam plays a key role in this regard. When complex geometries like crankshaft fillets are treated, the surface cannot be considered a series of flat surfaces. Obviously, this leads to locally varying degrees of energy absorption. In the present work, curved surface structures were chosen in order to analyze the impact of the geometrical characteristics on surface and subsurface material properties after laser treatment. Microstructure evolution generally was found to be similar for flat and curved geometries. However, even if higher absorption in the groove due to the illumination at larger incident angles was expected, the outer parts of the curved geometry were not fully hardened. Thus, the increased effective length of the complex geometry-treated and the larger heat-affected volume are expected to have a more dominant influence on the final appearance of the subsurface microstructure. Eventually, for austenitization of the complete illuminated surface volume, the energy density needs to be increased.

  • 16.
    Xi, Yinhu
    et al.
    Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi’an Jiaotong University, Xi’an, .
    Zhao, Yang
    Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi’an Jiaotong University, Xi’an, .
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Mao, Junhong
    Theory of Lubrication and Bearing Institute, Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi'an Jiaotong University.
    Time-dependent hysteresis friction behaviors of linear rolling bearings2018Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 94, nr 9-12, s. 3109-3116Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hysteresis friction behaviors of linear rolling bearings (LRBs) are important for precision positioning applications, which are related to the displacement and the traversed trajectory history within pre-rolling friction region. Although these behaviors have been pointed out in literature, the time dependence of transient hysteresis friction behaviors has not been reported before. In this work, the effects of initial conditions induced by the applied forces prior to commencement of the hysteresis motion are considered, which are denoted by the differences between the magnitudes of positive endpoints and the magnitudes of negative endpoints of virgin curves for the obtained asymmetrical hysteresis loops. The evolution of the time dependence is denoted by the decaying of the differences with the increasing dwell time. The effects of the damping and the junction growth during the dwell time are used to explain the time-dependent hysteresis friction behaviors of the LRB. The experiments of higher preload and lubrication-free conditions have been implemented as well, and the results indicate that the conditions are positive to diminish the time-dependent hysteresis friction behaviors.

  • 17.
    Zhu, Zhaolong
    et al.
    Nanjing Forestry University.
    Guo, Xiaolei
    Nanjing Forestry University.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Cao, Pingxiang
    Nanjing Forestry University.
    Na, Bin
    Nanjing Forestry University.
    Zhu, Nanfeng
    Nanjing Forestry University.
    The Effects of Cutting Parameters and Tool Geometry on Cutting Forces and Tool Wear in Milling High-density Fiberboard with Ceramic Tools2017Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 91, nr 9-12, s. 4033-4041Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, the effects of cutting parametersand tool geometry on cutting forces and tool wear whenup-milling high-density fiberboard with alumina ceramiccutting tools were investigated. Under the condition ofthe same feed per tooth, average chip thickness, andclearance angle, the results shown are as follows: first,the tangential forces Ft and normal forces Fr at lowspeedcutting were higher than those at high-speed cutting,but increased slowly with the increase of cuttinglength and rake angle decrease. Second, increased cuttingspeed and decreased rake angle had a great effecton rake face wear. Third, the wear patterns of tool wearwere rake wear and flank wear, which included pull-outof grain, flaking, and chipping. The wear mechanismswere adhesive wear and abrasive wear. Finally, at lowspeedcutting, the cutting tools with bigger rake anglecan be selected to reduce the energy consumption ofmachine tools. The tools with smaller rake angle canbe used for high-speed cutting to improve tool lifeand productivity of processing.

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