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  • 1. Alander, E. M.
    et al.
    Uusi-Penttila, M. S.
    Rasmuson, Åke C.
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology.
    Characterization of paracetamol agglomerates by image analysis and strength measurement2003In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 130, no 1-3, p. 298-306Article in journal (Refereed)
    Abstract [en]

    Paracetamol is crystallized in different solvents and techniques are developed and used to characterize the product. The product particles from three different solvent compositions: ethylene glycol, acetone and an acetone-water mixture (30-70 wt.%) have been examined. Product properties visually observed are quantified by image analysis and evaluation of measured image descriptors with Principal Component Analysis (PCA). The agglomerate strength has been determined by crushing single agglomerates. Depending on the solvent, the content of single crystals and agglomerates differ. Agglomerates differ by the number and size of crystals grown together, as well as by the strength.

  • 2.
    Andersson, Daniel C.
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Cadario, Alessandro
    Lindskog, Per
    On the influence from punch geometry on the stress distribution at powder compaction2010In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 202, no 1-3, p. 78-88Article in journal (Refereed)
    Abstract [en]

    A numerical analysis, using the finite element method, of the mechanical behavior at powder compaction at higher densities was performed. In this investigation the material behavior is modeled using an advanced macroscopic constitutive description initially presented by Brandt and Nilsson [1]. This material model, like many other models describing powder compaction at higher densities, includes a large number of constitutive parameters and as a result, a complete material characterization is a difficult task to perform or at least requires a large number of different experiments. A remedy to this problem is to apply inverse modeling, i.e. optimization, for determination of relevant material properties from comparatively simple experiments. It is then of course important, in order to achieve high accuracy results from the optimization procedure, that the stress fields produced during the experiments involves high gradients of stress. Adhering to simple uniaxial die compaction experiments the main parameter that can be used in order to achieve such a feature is the geometry of the punch used for load application. In the present investigation a number of punch profiles are studied and it is found that a skewed punch geometry is the most appropriate one to be used for experimental die compaction aiming at a constitutive description of the powder material based on inverse modeling. The main efforts are devoted towards an analysis based on the previously mentioned material model by Brandt and Nilsson [1] but also relevant results for another type of constitutive model will be presented. (C) 2010 Elsevier B.V. All rights reserved.

  • 3. Beyhaghi, M.
    et al.
    Kiani-Rashid, A.
    Khaki, J. V.
    Kashefi, M.
    Jonsson, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Influences of mechanical activation and heating rate on reaction processes in combustion synthesis of NiAl-Al 2 O 3 composites2019In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 346, p. 237-247Article in journal (Refereed)
    Abstract [en]

    This paper investigates the combustion synthesis of NiAl-Al 2 O 3 composites by the heating of Ni, NiO and Al powder mixture from 20 °C to 1300 °C. The influence of mechanical activation (without and with 1 h) and heating rate (20 °C/min and 40 °C/min) on thermal events in combustion synthesis process are investigated. Thermal events are assessed by Differential Thermal Analysis (DTA), X-Ray Diffractometry (XRD) and Scanning Electron Microscopy (SEM). By heating the sample without mechanical activation, exothermic reaction of NiO reduction by Al and Ni-Al intermetallic phases (Al 3 Ni, Al 3 Ni 2 , AlNi and AlNi 3 ) production happened in the presence of molten Al at 870 °C as one DTA peak. Mechanical activation causes occurrence of these reactions more separately at lower temperatures (590 °C and 630 °C). By decrement in the heating rate, these reactions happened in a more dispersed way at lower temperatures (590 °C and 630 °C). The reaction temperature for nickel aluminides formation in the presence of eutectic melt of AlNi 3 -Al is constant regardless of heating rate in mechanically activated powder. A seven-stage mechanism for reactions in a mechanically activated sample at a heating rate of 40 °C/min is proposed. Initially, by heating of the powder, an exothermic reaction between nickel oxide and aluminum and also nickel and aluminum occurs at 590 °C in solid state. NiO is consumed totally and Al 2 O 3 is produced from the nickel oxide reduction by aluminum. Nickel aluminide phases are formed from reactions between aluminum and primary nickel and also from aluminum and nickel formed by aluminothermic reduction of nickel oxide. With continuation of heating process, Al-Al 3 Ni eutectic transition happens at 630 °C and results in the liquid phase formation. Presence of the molten phase accelerates the exothermic nickel aluminides formation reactions. Aluminum is consumed totally in this stage and more intermetallic phases are developed. By increasing the temperature, diffusion is enhanced. The remaining Al 3 Ni melts at 856 °C. This small amount of molten phase slightly enhances exothermic reactions between nickel aluminides and leads the system towards the equilibrium phase. After this event, reactions progresses gradually. The nickel core shrinks by the diffusion progressively and the whole nickel aluminides system undergoes a gradual evolution towards the NiAl equilibrium phase.

  • 4.
    Beyhaghi, Maryam
    et al.
    Islamic Azad Univ, Fac Engn, Dept Met & Ceram, Mashhad Branch, Mashhad, Iran..
    Khaki, Jalil Vandati
    Ferdowsi Univ Mashhad, Dept Met & Mat Engn, Mashhad 917751111, Iran..
    Manawan, Maykel
    Univ Indonesia, Dept Phys, Depok 16424, Indonesia.;Politekn Negeri Jakarta, Energy Engn, Depok 1624, Indonesia..
    Kiani-Rashid, Alireza
    Ferdowsi Univ Mashhad, Dept Met & Mat Engn, Mashhad 917751111, Iran..
    Kashefi, Mehrdad
    Ferdowsi Univ Mashhad, Dept Met & Mat Engn, Mashhad 917751111, Iran..
    Jonsson, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    In-situ synthesis and characterization of nano-structured NiAl-Al2O3 composite during high energy ball milling2018In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 329, p. 95-106Article in journal (Refereed)
    Abstract [en]

    In this work, synthesis of NiAl-Al2O3 nanocomposite powders via the mechanosynthesis route and by using Ni, NiO and Al is investigated. Ignition of the reaction inside the ball-mill vial happens after 110 min; NiO is totally finished and NiAl and Al2O3 as product phases are formed. After 10 h of ball milling, raw materials are totally used in the reaction and only product phases exist in the vial. By continuing the ball milling process to 60 h, better mixing of the synthesized phases and decrement in their crystallite sizes plus partide size are observed. Crystallite sizes of the product phases are in the nanometer range in all ball milling times. Crystallite sizes of NiAl and Al2O3 after 10 h are around 11 nm and 19 nm respectively, and these are reduced to around 8 nm for both phases after 60 h of ball milling.

  • 5. Buscaglia, V.
    et al.
    Viviani, M.
    Buscaglia, M. T.
    Nanni, P.
    Mitoseriu, L.
    Testino, A.
    Stytsenko, E.
    Daglish, M.
    Zhao, Zhe
    Department of Physical Inorganic and Structural Chemistry, Stockholm University.
    Nygren, M.
    Nanostructured barium titanate ceramics2004In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 148, no 1, p. 24-27Article in journal (Refereed)
    Abstract [en]

    Dense nanocrystalline ceramics can be obtained starting from non-agglomerated nanopowders and using low-temperature sintering processes. The preparation and the properties of Barium Titanate (BaTiO3) ceramics and thick films are reported: ceramics were prepared by Spark Plasma Sintering (SPS) at 800 degreesC of nanopowders produced by a wet chemical process, while films were fabricated by airflow deposition (AD) of mixed fine and coarse powders at room temperature followed by isothermal firing. Ferroelectric ordering was found in both the ceramics and the sintered films by a.c. impedance. The transition from ferroelectric to paraelectric state was broadened over a wide temperature range with Curie-Weiss parameters strongly depressed in comparison to coarse-grained ceramics.

  • 6. Dadbakhsh, Sasan
    et al.
    Hao, L.
    Jerrard, P. G. E.
    Zhang, D. Z.
    Experimental investigation on selective laser melting behaviour and processing windows of in situ reacted Al/Fe2O3 powder mixture2012In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 231, no 0, p. 112-121Article in journal (Refereed)
  • 7.
    Lundkvist, Axel
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics.
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Olsson, Erik
    Luleå Univ Technol, Dept Engn Sci & Math, Div Solid Mech, Luleå, Sweden..
    A discrete element analysis of the mechanical behaviour of a lithium-ion battery electrode active layer2023In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 425, article id 118574Article in journal (Refereed)
    Abstract [en]

    Lithium-ion batteries experience charge capacity loss during their lifecycle caused by mechanical phenomena. In this study, a discrete element method (DEM) simulation model, to link the local mechanical behaviour in the positive electrode active layer to its global mechanical properties, was developed. DEM is a suitable method to use as the electrode active layer has a granular structure and the model includes contact formulations for the active particles and the binder domain. Simulations of the calendering process and the measurement of the active layer's global mechanical properties is possible with the framework. The model developed can capture the pressure sensitivity of the active layer, which has been observed in experiments.

  • 8. Mangalaraja, R.V.
    et al.
    Mouzon, J.
    Hedström, Peter
    Division of Engineering Materials, Luleå University of Technology, Luleå, Sweden.
    Camurri, C.P.
    Ananthakumar, S.
    Odén, M.
    Microwave assisted combustion synthesis of nanocrystalline yttria and its powder characteristics2009In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 191, no 3, p. 309-314Article in journal (Refereed)
    Abstract [en]

    Microwave assisted combustion synthesis is used for fast and controlled processing of advanced ceramics. Single phase and sinter active nanocrystalline cubic yttria powders were successfully synthesized by microwave assisted combustion using the organic fuels urea, citric acid and glycine as reducing agents. The precursor powders were investigated by thermogravimetry (TG) and differential scanning colorimetry (DSC) analyses. The as-prepared precursors and the resulting oxide powders calcined at 1100 degrees C in oxygen atmosphere were characterized for their structure, particle size and morphology, The thermal analyses (TG/DSC). X-ray diffraction (XRD) and Fourier transform infra red (FT-IR) results demonstrate the effectiveness of the microwave assisted combustion synthesis. The scanning electron microscopy (SEM) observations show the different morphologies of as-prepared powders and transmission electron microscopy (TEM) shows the particle sizes in the range of 30-100 nm for calcined powders for different fuels. The results confirm that the homogeneous, nano scale yttria powders derived by microwave assisted combustion have high crystalline quality and the morphology of the as-prepared precursor powders depends on the nature of organic fuel used.

  • 9.
    Marchetti, Lorenzo
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.
    Hulme-Smith, Christopher
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.
    Flowability of steel and tool steel powders: A comparison between testing methods2021In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 384, p. 402-413Article in journal (Refereed)
    Abstract [en]

    Theflow behaviour of a powder is critical to its performance in many industrial applications and manufacturing processes. Operations such as powder transfer, die filling and powder spreading all rely on powder flowability. Multiple testing methods can help in assessing flowability, but it is not always clear which may better represent specific flow conditions or how different metrics correlate. This study compares 8 different flowability testing methods using 11 steel powders varying in chemistries and size fractions. Regression analysis was used to test the relationship between each flowability metric obtained. Some metrics, such as the conditioned bulk density,relate to many flowability indicators. Others, such as the basic flowability energy, show poor correlations to othervariables, likely describing different aspects of the powder flow behaviour. When two metrics show a strong correlation, as between conditioned bulk density and Hausner ratio, a numerical relationship is derived: CBD =−(5.65 ± 0.86)HR g cm−3.

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  • 10.
    Olsson, Erik
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.). KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    A contact model for the normal force between viscoelastic particles in discrete element simulations2019In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 342, p. 985-991Article in journal (Refereed)
    Abstract [en]

    DEM modeling of granular materials composed of viscoelastic particles can provide valuable insights into the mechanical behavior of a wide range of engineering materials. In this paper, a new model for calculating the normal contact force between visoelastic spheres is presented based on contact mechanics that takes the mechanical behavior of the DEM particles into account. The model relies on an application of the viscoelastic correspondence principle to elastic Hertz contact. A viscoelastic relaxation function for the contact is defined and a generalized Maxwell material is used for describing this function. An analytical expression for the increment in contact force given an increment in overlap is derived leading to a computationally efficient model. The proposed model provides the analytical small deformation solution upon loading but provides an approximate solution at unloading. Comparisons are made with FEM simulations of contact between spheres of different sizes of equal and dissimilar materials. An excellent agreement is found between the model and the FEM simulations for almost all cases except at cyclic loading where the characteristic times of the viscoelastic behavior and the loading are similar.

  • 11.
    Olsson, Erik
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Larsson, Per Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    A numerical analysis of cold powder compaction based on micromechanical experiments2013In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 243, p. 71-78Article in journal (Refereed)
    Abstract [en]

    The discrete element method (DEM) is used for predicting the compaction behavior of two types of spray dried cemented carbide granules. The material model of the granules is determined by micromechanical experiments. First, compression tests are performed on single granules giving information of the deformation behavior at relatively small deformations. For larger deformations, nanoindentation tests are performed to give further information of the constitutive behavior indicating a strong hardening behavior at high strains. The material model is implemented in an FE model of two particles in contact and the relation between contact force and indentation depth is exported to a DEM program. The DEM program is used to simulate presently performed uniaxial die compaction experiments where the geometry of the die is taken into account. Excellent agreement is found between the experiments and the numerical predictions in the range where results from DEM simulations are valid.

  • 12.
    Olsson, Erik
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Micromechanical Investigation of the Fracture Behavior of Powder Materials2015In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 286, p. 31article id 11185Article in journal (Refereed)
    Abstract [en]

    Fracture of compacted powder has been studied experimentally and numerically using a micromechanicalapproach. In the experimental investigation, the compacts are crushed in two dierent directions to accountfor general stress states and a microscopy study shows that fracture of the powder granules plays asignicant role in the fracture process. The numerical analysis is based on the Discrete Element Method(DEM) and a novel approach is presented to account for the fracture of the particles in the numericalmodel. The force-displacement relations for two particles in contact, which are needed in DEM, are derivedusing micomechanical experiments together with nite element analyses of the contact problem. The contactmodel accounts for plastic compression, elastic unloading and adhesive bonding together with frictionand tangential bonding. The model shows a very good agreement with the experimental data both for theelastic behavior during unloading and, if failure of the particles is accounted for, the fracture of the compacts.

  • 13.
    Persson, Fredrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.
    Hulme-Smith, Christopher
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Process.
    Particle morphology of water atomised iron-carbon powders2022In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 397, p. 116993-, article id 116993Article in journal (Other academic)
    Abstract [en]

    Water atomisation can produce metal powders faster and at lower cost than gas atomisation, but it is well known that the powder particles are irregular and may contain a large number of pores. The current study analyses three iron-carbon alloys with different superheats, produced as powder by water atomisation and compares the particle shapes and porosity in each. The alloy with the most carbon (4.2 wt%) showed the highest circularity (0.72) for 20-40 µm particles, but the lowest (0.59) for 180-210µm particles. This is consistent with collisions between droplets affecting particle shape. The lowest-carbon melt (0.22 wt%) solidified fastest, so underwent fewest collisions and showed similar circularity for all particle sizes. The breakdown of water to form hydrogen and the formation of hydrogen bubbles was the most likely cause of porosity. The findings of this study may be used to inform future water atomisation process design to control particle shape and minimise porosity.

  • 14.
    Rosenblad, Louise
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Staf, Hjalmar
    Sandvik Coromant AB, R&D, SE-12680 Stockholm, Sweden..
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Parametric dependency of a constitutive model describing solid state sintering of cemented carbides2022In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 403, p. 117407-, article id 117407Article in journal (Refereed)
    Abstract [en]

    This study focuses on an inverse modelling approach, using FEM to simulate the sintering of WC-Co powder using a continuum model. From a previously developed constitutive model of cemented carbide, the dependency of the material parameters is investigated in a sensitivity study. A value of sensitivity is assigned to all the material parameters and calculated at different steps in the sintering process, which represent its importance for capturing the shrinkage during sintering. The approach is that only the more sensitive parameters should be fitted when changing experimental setup or material composition, leaving the less important parameters constant, resulting in fewer tests and iterations. This approach is tested in an optimization of WC-Co powder sintering cycle, where the shrinkage curve is experimentally determined. It is concluded that some of the material parameters play a minor role in the modelling and could be set as constants in an optimization. The constitutive material model alone is unable to capture all features that appeared in the shrinkage curve during the experiment. Improvements of the model are discussed. An additional investigation, performed without heating rate dependency, shows that the remaining material parameters could compensate for the omitted heating rate for a known sintering cycle without losing accuracy.

  • 15.
    Shoaib, Muhammad
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Kari, Leif
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Azhdar, Bruska
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Simulation of high-velocity compaction process with relaxation assists using the discrete element method2012In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 217, p. 394-400Article in journal (Refereed)
    Abstract [en]

    The discrete element method is used to investigate the high-velocity compaction process with additional piston supports known as relaxation assists. It is shown that by incorporating the relaxation assists in the piston-die assembly, particles can be better locked during the compaction process. The simulation results reveal that relaxation assists offer; smooth compaction during loading stage, prevention of the particle separation during unloading stage and conversion of higher kinetic energy of hammer into particle deformation. Finally, the influences of various loading elements on compaction process and effects of presence of adhesion during unloading stage are investigated. The results support the findings of experimental work.

  • 16.
    Staf, Hjalmar
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.). Sandvik Coromant, Stockholm, SE-126 80, Sweden.
    Kis, Z.
    Szentmiklósi, L.
    Kaplan, B.
    Olsson, Erik
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Determining the density distribution in cemented carbide powder compacts using 3D neutron imaging2019In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 354, p. 584-590Article in journal (Refereed)
    Abstract [en]

    Spray-dried refractory carbide and metal powder mixtures, containing tungsten carbide, is compacted and sintered during the production of conventional cutting tool inserts. Since friction between the pressing tool and the powder gives rise to density gradients in the powder compact, shrinkage during sintering is uneven. The shape of the sintered blank is important and can be predicted with finite element (FE) simulations. To validate the simulation of the pressing procedure, the density gradients in the powder compacts must be measured with a high spatial resolution. Since tungsten has a high atomic number, it is hard to penetrate with X-rays and even cold neutrons. We show here that by using a polychromatic beam of thermal neutrons, along with beam-hardening correction, such measurements can be successfully realized. The obtained results show good agreement with corresponding FE-simulations. Also, deliberate differences in the compaction process could be verified with the neutron measurements.

  • 17.
    Staf, Hjalmar
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Evaluation of an advanced powder-die frictional model2020In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 363, p. 569-574Article in journal (Refereed)
    Abstract [en]

    It is known that the shape of a cutting insert blank, after pressing and sintering, can be predicted with finite element (FE) simulations. It is also known that such simulations have the potential to save costs and time when used for press tool compensation. However, in such simulations (and in a real situation), the frictional behaviour has a great influence on the results. Therefore, in this study, two frictional models are discussed and implemented into a commercial FE-program. The results from the different frictional descriptions, when for instance analysing density after compaction, shows a clear difference. It can be concluded that the frictional behaviour at powder pressing has to be modelled in detail, also at low forces.

  • 18.
    Staf, Hjalmar
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics. Sandvik Coromant, SE-126 80 Stockholm, Sweden.
    Olsson, Erik
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Mechanical Characterization of PowderMaterials: A General Approach Detailedfor Cemented Carbides2020In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 364, p. 531-537Article in journal (Refereed)
    Abstract [en]

    Material parameter curves in an advanced material model describing compaction of spraydried cemented carbide powder are determined successfully based on a general approach formaterial characterization of powder materials. Pressing forces from a production machineand equivalent finite element (FE) calculations are used in inverse modelling. A pressingmethod that includes multiple unloading steps is used. The material model is of DruckerPrager CAP kind and friction between powder and pressing tool is modelled as a function ofnormal pressure. The results are verified with density gradient measurements using aneutron source. The method is proven to be robust and the results show good agreementbetween experiment and simulation. Effects that have not been captured numericallypreviously are captured due to the high accuracy of material characterization. The presentapproach is detailed for tungsten carbide powders but is valid for other powder materialswhen properly calibrated for constitutive and frictional effects in the same manner asoutlined here.

  • 19.
    Strömgren, Tobias
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Brethouwer, Geert
    KTH, School of Engineering Sciences (SCI), Mechanics, Turbulence. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Amberg, Gustav
    KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Johansson, Arne V.
    KTH, School of Engineering Sciences (SCI), Mechanics, Turbulence. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Modelling of turbulent gas-particle flows with focus on two-way coupling effects on turbophoresis2012In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 224, p. 36-45Article in journal (Refereed)
    Abstract [en]

    An Eulerian model was developed for turbulent gas-particle flow that takes into account the influence of particles on the gas-phase turbulence. For the description of the particle-phase stress the kinetic theory of granular flow and the simpler Hinze model were adopted. A K-ω model was used as the gas phase turbulence model. The difference between one- and two-way coupling was investigated for different particle volume fractions and particle diameters. It was found that particles with a much higher density than the fluid substantially affect the gas-phase in turbulent channel flow for particle volume fractions as low as 10 -4. The models with the particle-phase stress described by the kinetic theory of granular flow and the simpler Hinze model produce similar results for particles with small response times but deviate for larger response times. The study shows that two-way coupling and the turbophoretic effect must be taken into account in models even at relatively low particle volume fractions.

  • 20.
    Suo, Si
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'’an Jiaotong University, Xi'’an, China; Institute for Applied Materials, Karlsruhe Institute of Technology (KIT), Germany.
    Zhai, Chongpu
    State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'’an Jiaotong University, Xi'’an, China.
    Kamlah, Marc
    Institute for Applied Materials, Karlsruhe Institute of Technology (KIT), Germany.
    Gan, Yixiang
    School of Civil Engineering, The University of Sydney, Sydney, NSW 2006, Australia; The University of Sydney Nano Institute (Sydney Nano), The University of Sydney, Sydney, NSW 2006, Australia.
    An unexplored regime of binary packing under extreme mixture conditions2023In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 428, article id 118802Article in journal (Refereed)
    Abstract [en]

    We present an unexplored regime, where the binary random close packing fraction ϕRCPb is smaller than that of the mono-sized one ϕRCPm. This is against previous observations and common perceptions that binary packing tends to be denser than mono-sized packing. We numerically confirm the critical condition for reaching this exceptional regime in the size ratio (Rr) and mole fraction (Xs) space, where Rr is close to 1, and the mole fraction of the smaller sphere Xs close to 0. Under the same loading condition, the stiffness of the packing at this exceptional regime is found to be significantly higher than that of the mono-sized packing. The formation and transition of this regime for varying Rr and Xs are theoretically modelled based on the hard-sphere fluid theory. This exceptional regime remains unreported in existing literature, yet significant for our fundamental understanding of binary packing systems.

  • 21. Zhang, Z. Y.
    et al.
    Sandström, Rolf
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Frisk, K.
    Salwen, A.
    Characterization of intermetallic Fe-Mn-Si powders produced by casting and mechanical ball milling2003In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 137, no 3, p. 139-147Article in journal (Refereed)
    Abstract [en]

    Mechanical milling is a common method used to produce different powders. Milling time is one of the most important factors in the process, which affects characteristics such as particle size distribution and morphology. Four compositions of mechanically milled Fe-Mn-Si master alloy powders were investigated in the present paper. Milling times from 10 to 120 min were used. Particle size distribution and milling kinetics of Fe-Mn-Si powders were studied, and the parameters in breakage function have been determined. The results show that powder characteristics vary with the contents of silicon and manganese. During milling, the particle size initially decreases. At longer milling times, however, small particles agglomerate to larger particles (overmilling). The optimum milling time to get powders with very fine particle sizes is alloy-dependent. Apart from the agglomeration, the milling process of Fe-Mn-Si powders can be described by a classic batch-grinding equation based on the population balance model.

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