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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.

  • 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 (Refereegranskat)
    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.
    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.

  • 8.
    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. 

  • 9.
    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.

  • 10.
    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.

  • 11.
    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.

  • 12.
    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.

1 - 12 av 12
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