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  • 1.
    Forsström, Dan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Larsson, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Granular flow model for large scale wear prediction2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    To predict abrasive wear in industrial bulk material, couplings between granular material flow and wear calculation have to be developed. It would also be desirable to include both sliding and impact wear in such model. The emptying of a tipper loaded with a rock mass of approximately 20 tonnes was modelled. The rock was modelled using two different numerical techniques: the discrete element method (DEM) and the finite element method (FEM). The purpose of the simulations was to study the coupling between the two numerical techniques and to compare their usefulness in wear calculation. The tipper emptying model had previously been used in calculating abrasive wear during unloading. A tipper body [1], protected with SSAB Hardox 450 steel, was modelled with FEM using and a piecewise linear plasticity model for the material behaviour. For the numerical model labelled DEMFEM, the rocks were modelled with spherical discrete elements with rolling friction and damping parameters applied to simulate non-spherical rocks. Another numerical model labelled FEM-FEM, to mimic arbitrary shape rocks used two slightly different simplified shapes, round and prism like kinds. To compare the numerical approaches the pressure on the tipper body was studied at two times during the unloading. The first measurement occasion was defined when the rock mass had been dropped into the tipper and had come to rest and the second when the tipping had started and approximately half of the load had been unloaded. When the two approaches were compared it could be seen that the calculated pressure field agreed fairly well both initially with the rock mass at rest and during emptying with the rock mass in motion.

  • 2.
    Gustafsson, Gustaf
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Larsson, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Numerical Prediction of Fracture in Iron Ore Pellets During Handling and Transportation2017Ingår i: / [ed] Barry Wills, 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Iron ore pellets are sintered, centimetre-sized spheres of ore with high iron content. Together with carbonized coal, iron ore pellets are used in the production of steel. During transportation and handling of iron ore pellets they are exposed to different loads, resulting in degradation of the strength and in some cases fragmentation. The aim of this work is to increase the knowledge of how to design the handling systems for iron ore pellets to decrease the amount of fractured materials in the flows. A numerical finite element model for iron ore pellets fracture probability analysis is presented with a stress based fracture criterion. The model is used to simulate different flows of iron ore pellets hitting guide plates and to predict the proportion of fractured iron ore pellets in the flow. The amount of fractured iron ore pellets are predicted at different flow velocities, showing good agreement with experimental measurements.

  • 3.
    Gustafsson, Gustaf
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Nishida, Msahiro
    Nagoya Institute of Technology, Gokisocho, Showa-ku, Aichi.
    Larsson, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Fracture probability modelling of impact-loaded iron ore pellets2017Ingår i: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 102, s. 180-186Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Blast furnace iron ore pellets are sintered, centimetre-sized ore spheres with a high iron content. Together with carbonized coal, iron ore pellets are used in the production of steel. In transporting pellets from pelletizing plants to customers, iron ore pellets are exposed to different static and dynamic loading situations, resulting in strength degradation and, in some cases, fragmentation. This can lead to a reduced gas flow in the blast furnace, which causes reduced quality in steel production. Reliable numerical simulations that can predict the ability of the pellets to endure their handling are important tools for optimizing the design of equipment for iron ore handling. This paper describes the experimental and numerical work performed to investigate the impact fracture behaviour of iron ore pellets at different strain rates. A number of split Hopkinson pressure bar tests with different striker velocities are carried out and analysed to investigate the strain rate dependency of the fracture strength of iron ore pellets. Fracture data for iron ore pellets are derived and expressed in terms of statistical means and standard deviations. A stress based, strain-rate dependent fracture model that takes triaxiality into account is suggested. The fracture model is used and validated with impact tests of iron ore pellets. In the validation experiment, iron ore pellets are fired against a steel plate, and the percentage of fractured pellets at different impact velocities are measured. Finite element simulations of the experiment are carried out and the probability of pellets fracturing during impact are calculated and compared with the experimental results. The agreement between the experiments and numerical simulations shows the validity of the model.

  • 4.
    Gustafsson, Gustaf
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Larsson, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Numerical modelling, simulation and validation of icing on a wind turbine blade2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    Today there is a strong development of wind power in northern Sweden, where risk for icing conditions is present. Icing of the blades leads to changing load conditions, production loss and risk of overloading the machine components. When the ice loose from the blades, the ice throw can lead to both physical damage and personal injury. Uncertainties around these issues threaten the planned expansion in the northernmost regions. Prediction of loads and production losses are of great importance for the durability and economy of wind power plants [[i]]. A thrust worthy numerical model of ice loads on wind turbines will be a valuable tool for minimizing the costs due to damage and production losses caused by icing.

    This work presents a numerical model for simulating ice accretion on a wind turbine blade in lab-scale. It is a multi-physic model with interaction of three phases: the air, the water droplets and the wind turbine blade. The air flow is modelled with incompressible fluid dynamics (ICFD), the water droplets in the air is modelled with the discrete element method (DEM) and the wind turbine blade is modelled with the finite element method (FEM). A two way coupling is used for the interaction between the air and the water droplets and between the air and the wind turbine blade. A freezing condition controls the ice accretion when the water droplets hits the wing profile. The simulation is compared with a lab-scale experiment of ice accretion of a wind turbine profile in a wind tunnel found in literature [[ii]]. The experiment is well documented with well defined parameters such as: temperature, wind velocity, water content in the air, size of the water droplets, wing profile and angle of attack. Two simulations were done for two different angles of attack and validated by comparing ice profiles on the blades numerically and experimentally for the two cases. Similar ice profiles were found numerically and experimentally.

    [[i]]             IEA Wind Recommended Practice 13: Wind Energy in Cold Climates, 2012.

     

    [[ii]]                         C. Hochart et. al., “Wind Turbine Performance under Icing Conditions”, Wind Energy, 11, 319-333 (2008)

     

  • 5.
    Hammarberg, Samuel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Larsson, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Modelling of interaction between suspension and structure in a tumbling mill2014Ingår i: 11th World Congress on Computational Mechanics (WCCM XI) 5th European Conference on Computational Mechanics (ECCM V) 6th European Conference on Computational Fluid Dynamics (ECFD VI) / [ed] Eugenio Oñate; Xavier Oliver; Antonio Huerta, Barcelona, 2014, Vol. 6, s. 7383-7393Konferensbidrag (Refereegranskat)
  • 6.
    Jonsén, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Larsson, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Hammarberg, Samuel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindkvist, Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    A Particle Based Modelling Approach for Predicting Charge Dynamics in Tumbling Ball Mills2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wet grinding of minerals in tumbling mills is a highly important process in the mining industry. During grinding in tumbling mills, lifters submerge into the charge and create motions in the ball charge, the lifters is exposed for impacts and shear loads that will wear down the lifters. Increased loading can accelerate the wear and the lining has to be replaced. Replacing the lining is an expensive and time consuming operation that is preferred to be done within planned maintenance stops. Prediction of the charge motion and wear rate for different grinding operations and linings are therefore desirable to predict the lining life.

     

    Modelling of wet grinding in tumbling mills that include pulp fluid and its interaction with both the grinding balls and the mill structure is an interesting challenge and some different approaches have been suggested, see [1-2]. For an effective and successful prediction, the numerical model has to be able to handle the pulp fluid and its simultaneous interactions with both the ball charge and the mill structure, in a computationally efficient approach. In this work, the pulp fluids are modelled with a Lagrange based method called incompressible computational fluid dynamics, (ICFD), which gives the opportunity to model free surface flow. This method gives robustness and stability to the fluid model and is efficient as it gives possibility to use larger time steps than the conventional CFD. The ICFD solver can be coupled to other solvers as in this case the finite element method, (FEM) solver for the mill structure and the discrete element method (DEM) solver for the ball charge. The combined ICFD-DEM-FEM model can predict both charge motion and responses from the mill structure, as well as the pulp liquid flow and pressure. The numerical grinding case presented here is validated against experimentally measured driving torque signatures from an instrumented small-scale batch ball mill, see [3]. This approach opens up the possible to predict the volume of the high-energy zone and optimise lifter design and operating conditions. The ICFD solver improve efficiency and robustness for studying wet grinding in tumbling mill systems and can predict the charge dynamics and the wear distribution in such systems.

     

    References

    [1]   Jonsén, P. et al., (2018). Preliminary validation of a new way to model physical interactions between pulp, charge and mill structure in tumbling mills. Minerals Enginering. Accepted for publication

    [2]   Jonsén, P., Stener, J.F., Pålsson, B.I. and Häggblad, H.-Å., (2015). Validation of a model for physical interactions between pulp, charge and mill structure in tumbling mills. Minerals Engineering, Vol. 73, 77–84.

    [3]   Jonsén, P. Stener, J. F. Pålsson, B. I. and Häggblad, H.-Å., (2013). Validation of tumbling mill charge induced torque as predicted by simulations. Minerals and Metallurgical Processing, vol. 30, No. 4, 220-225.

  • 7.
    Larsson, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Modelling and Characterisation of Granular Material Flow2017Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Granular materials are very common both in nature and in industry, and their extensive use means that there are financial incentives for increased efficiency. There are huge costs related to their use and handling, which is a major motivation for increased knowledge of the behaviour of granular materials at different loading conditions. The development of tools for numerical simulation of granular materials at diverse flow conditions gives the opportunity to study and optimise various industrial processes. In order for such tools to be trustworthy, calibration and validation against experimental results is essential. Thus, experimental methods for accurate measurement and characterisation of granular material flow are required. The objective of this thesis is to contribute to the knowledge of experimental characterisation and numerical modelling of non-cohesive, dry granular materials, at dissimilar flow conditions. In order to fulfil this objective, an experimental method, able to capture the flow behaviour of granular materials is developed. The method is based on the digital image correlation technique, and it is used for field measurements of displacement and velocity. The devised method is used to obtain field measurements for the flow of sand, tungsten carbide powder and potassium chloride. For modelling and simulation, the smoothed particle hydrodynamics (SPH) method, and a pressure-dependent, elastic-plastic constitutive model are used.

    In this thesis, experimental characterisation and numerical modelling of granular material flow is performed in a number of applications. An experimental powder filling rig is used to study the flow during filling of sand into a die. A high-speed digital camera is used to record the flow, and the digital image correlation technique is used to obtain field measurements during the filling. This method is also applied in another experimental setup, where flow during filling of spherical tungsten carbide powder into a die is studied. The filling of tungsten carbide powder is simulated using the SPH method, and the results are compared to the field measurements with good agreement. Furthermore, the flow of potassium chloride is studied experimentally in the collapse of a granular column and in the discharge from a flat bottomed silo. The material flow process in both the column collapse and silo discharge are simulated using the SPH method. The results from simulations are found to be in agreement with observations reported in literature, and with experimental measurements obtained in this work. In conclusion, an experimental method for characterising granular material flow through field measurements is presented. The method is used to support the exploration of numerical tools for modelling and simulation of granular material flow. Furthermore, the high accuracy field measurements are used for improved calibration and validation of numerical methods. Reliable numerical simulations allows for study of the mechanisms that are present during granular material flow, mechanisms that might be hard or even impossible to investigate experimentally. The work within the present thesis contributes to the knowledge of both experimental characterisation and numerical modelling of granular material flow.

  • 8.
    Larsson, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Particle Methods for Modelling Granular Material Flow2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Granular materials are very abundant in nature and are often used in industry, wherethe dynamics of granular material ow is of relevance in many processes. There arestrong economic and environmental incentives for increased eciency in handling andtransporting granular materials. Despite being common, the mechanical behaviour ofgranular materials remains challenging to predict and a unifying theory describing granularmaterial ow does not exist. If the ambition is an ecient industrial handling ofgranular materials, increased knowledge and understanding of their behaviour is of utmostimportance. In the present thesis, particle-based numerical methods are used formodelling granular material ow. In this context, particle-based methods refer to the useof particles as a discretization unit in numerical methods. Particle-based modelling canbe divided in two main approaches: discrete and continuum. In a discrete approach, eachphysical particle in the granular mass is modelled as a discrete particle. Newton's secondlaw of motion combined with a contact model governs the behaviour of the granular mass.In a continuum approach, the granular material is modelled using a constitutive law relatingstresses and strains. As a discrete approach, the discrete element method (DEM) isused and as a continuum approach the smoothed particle hydrodynamics (SPH) methodand the particle nite element method (PFEM) are used. Furthermore, an experimentalmethodology able to capture the ow behaviour of granular materials is developed. Themethodology is based on digital image correlation and it is used to obtain the in-planevelocity eld for granular material ow. This thesis covers experimental measurementsand numerical modelling of granular material ow in a number of applications. In paperA, an experimental powder lling rig is used to study the ow of sand. With thisrig, a methodology for obtaining the in-plane velocity eld of a granular material ow isdeveloped. This methodology is applied in paper B, to quantify the ow of a tungstencarbide powder. The powder is modelled using the SPH method, with good agreementto experimental results. In paper C, the ow of potassium chloride fertilizers is modelledusing the SPH method, and in Paper D the PFEM is explored for modelling of granularmaterial ow. The numerical models are validated against experimental results, suchas in-plane velocity eld measurements. In paper E, coupled nite element, DEM andPFEM models are used to model the physical interactions of grinding media, slurry andmill structure and in a stirred media mill. The ndings in the present thesis support theestablishment of particle-based numerical methods for modelling granular material owin a number of dierent applications. Furthermore, a methodology for calibration andvalidation of numerical models is developed.

  • 9.
    Larsson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Carbonell, Josep Maria
    Centre Internacional de Mètodes Numèrics en Enginyeria (CIMNE) Universitat Politècnica de Catalunya (UPC).
    Rodriguez Prieto, Juan Manuel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Celigueta, Miquel Angel
    Centre Internacional de Mètodes Numèrics en Enginyeria (CIMNE) Universitat Politècnica de Catalunya (UPC).
    Latorre, Salvador
    Centre Internacional de Mètodes Numèrics en Enginyeria (CIMNE) Universitat Politècnica de Catalunya (UPC).
    Numerical simulation and validation of powder filling using particle based methods2017Ingår i: PARTICLES 2017, 2017Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Powder pressing is a complicated process as the mechanical behaviour of the powder material changes with increasing density. Manufacturers tend to produce components with shapes of increasing complexity requiring improved pressing equipment and methods. Mechanical properties of powder materials changes dramatically from the beginning to the end of the compaction phase. Previous investigations have shown that powder transfer and large powder flow during filling affects the strength of the final component significantly. Combined experimental and numerical studies can improve the understanding of the impact the filling stage has on the final component, e.g. to explain the non-homogeneity of the density of powder pressed parts.This work covers numerical modelling and simulation of powder filling using two different approaches, the discrete element method (DEM) [1,2] which is a micro mechanical based method and the particle finite element method (PFEM) [3] which is a continuum based method. Experimental measurements with digital speckle photography (DSP) [4] from a previous study [5] are used to validate the numerical simulations. The numerical results are compared in terms of agreement with the experimental results, such as velocity- and strain field data. The numerical simulations are further compared in terms of computational efficiency.The comparison of DSP measurements and simulations gives similar flow characteristics. In conclusion, experimental measurements with DSP together with numerical simulation are powerful tools to increase the knowledge of powder filling and also to improve the numerical model prediction. Improved numerical models will facilitate future product development processes and decrease the lead time.

  • 10.
    Larsson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Experimental and numerical study of potassium chloride flow using smoothed particle hydrodynamics2018Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 116, s. 88-100Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Materials in granular form are widely used in industry and in the society as a whole. Granular materials can have various behaviours and properties. An accurate prediction of their flow behaviour is important to avoid handling and transportation issues. In this study, the flow behaviour of dry potassium chloride (KCl) in granular form was investigated experimentally and simulated numerically. The aim was to develop numerical tools to predict the flow of KCl in transportation and handling systems and granular material flow in various industrial applications. Two experimental setups were used to quantify the flow of KCl. In the first setup, the collapse of an axisymmetric granular column was investigated. In the second setup, digital image correlation was used to obtain velocity field measurements of KCl during the discharge of a flat-bottomed silo. The two experiments were represented numerically using two-dimensional computational domains. The smoothed particle hydrodynamics method was used for the simulations, and a pressure-dependent, elastic-plastic constitutive model was used to describe the granular materials. The numerical results were compared to the experimental observations, and an adequate qualitative and quantitative agreement was found for the granular column collapse and the silo discharge. Overall, the simulated flow patterns showed adequate agreement with the experimental results obtained in this study and with the observations reported in the literature. The experimental measurements, in combination with the numerical simulations, presented in this study adds to the knowledge of granular material flow prediction. The results of this study highlights the potential of numerical simulation as a powerful tool to increase the knowledge of granular material handling operations.

  • 11.
    Larsson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    DEM-CFD Simulation of the Effect of Air on Powder Flow During Die Filling2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the field of powder metallurgy (PM), complex components with complicated shapes can be manufactured. One important step in the PM process is the powder pressing process, where powder is consolidated during a forming operation into a desired shape, normally by applying pressure. During powder pressing, the mechanical properties of powder materials change dramatically. PM manufacturers tend to produce components with shapes of increasing complexity, requiring improved pressing equipment and methods. The most crucial aspect is to control the powder flow during die filling and the final powder density distribution after the filling stage, which has been shown to affect the strength of the final component significantly [1].

    To investigate the non-homogeneity of the density of PM components, experimental studies combined with numerical simulations of the die filling stage are exploited.

    This work covers the numerical modelling and simulation of die filling. The discrete element method (DEM) [2] was used to model the powder, and computational fluid dynamics (CFD) to model the air. To study the effect of air on powder flow, the DEM was coupled to the CFD using a two-way coupling approach. Experimental measurements with digital speckle photography (DSP) from a previous study [3] were used for comparison with the numerical simulations.

    The comparison of the DSP measurements and the numerical simulations showed similar macroscopic flow characteristics. Thus, the adequacy of the proposed DEM-CFD model has been demonstrated in a metal powder die filling operation. The DEM-CFD method has been shown to be an effective method for the numerical simulation of the interaction between powder and air.

     

    References

    [1]   Zenger, D. & Cai, H. (1997). Handbook of the Common Cracks in Green P/M Compacts. Metal Powder Industries Federation, MPIF. Worcester, USA.

    [2]   Cundall, P. A., & Strack, O. D. (1979). A discrete numerical model for granular assemblies. geotechnique, 29(1), 47-65.

    [3]   Larsson, S., Gustafsson, G., Jonsén, P. & Häggblad, H.-Å. (2016). Study of Powder Filling Using Experimental and Numerical Methods.  In: World PM2016 Congress & Exhibition, Hamburg, October 9-13, 2016.

  • 12.
    Larsson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Experimental and numerical study of granular flow using particle methods: application in handling of potassium chloride2017Konferensbidrag (Refereegranskat)
  • 13.
    Larsson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Study of Powder Filling Using Experimental and Numerical Methods2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    This work covers both experimental measurements and numerical modelling of powder filling. Experimental measurements with digital speckle photography (DSP) are used to study powder flow during die filling. DSP measurements are realized by recording the powder filling process with a high speed video camera. The image series are then evaluated using an image correlation technique. By this, velocity and strain field data during the filling process can be visualised. DSP measurements are also supporting the development of a numerical model of the process. In this work the smoothed particle hydrodynamics (SPH) method is used to model the powder filling process. The numerical results are similar compared to the DSP measurements when comparing velocity fields during powder filling. The SPH model is further used to evaluate the density distribution after filling. Experimental measurements combined with simulation are powerful tools to increase the knowledge of the powder filling process.

  • 14.
    Larsson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oudich, Aliae
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Experimental methodology for study of granular material flow using digital speckle photography2016Ingår i: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 155, s. 524-536Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Granular material flow occurs in many industrial applications, and the characteristics of such flow is challenging to measure. Therefore, an experimental method that captures the flow behavior at different loading situations is desired.

    In this work, experimental measurements of granular material flow with digital speckle photography (DSP) are carried out. The granular flow process is recorded with a high-speed camera; the image series are then analyzed using the DSP method. This approach enables field data such as displacement, velocity, and strain fields to be visualized during the granular material flow process. Three different scenarios were studied: free surface flow in a fill shoe, flow without a free surface in a fill shoe, and the rearrangement of material in a cavity. The results showed that it is possible to obtain field data of the motion of particles for all three scenarios with the DSP technique. The presented experimental methodology can be used to capture complex flow behavior of granular material.

  • 15.
    Larsson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Modelling of interaction between multi-phase fluid and mill structure in a tumbling mill2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Free surfaces in fluid structure interaction (FSI) with multiple fluids are difficult to numerically predict. Hydro and wind power turbines and lubrication of mechanical components are examples of engineering applications where FSI can be important to consider. This work investigates the possibility to use a node (particle) based finite element method coupled to a standard finite elementmethod (FEM) to simulate a tumbling mill partly filled with a pulp fluid and the FSI between solid mill casing and pulp fluid. Modelling of wet milling is a complex multi-physics problem; wet milling is often used in the mining industry. For better understanding of the tumbling mill process numericalmethods can be used, and the process has previously been modelled with a combination of other numerical methods, [1]. The tumbling mill has four equally spaced lifters and measures Ø300 x 450 mm, see Fig. 1. A mixture of magnetite and water was filled to 30 % of the total volume of the mill. In this work, the mixture was considered as one homogeneous fluid with a density of 2500 kg/m3 and with a dynamic viscosity of 267 mPa∙s. Air in the tumbling mill was considered as a second fluid phase. In this work the mixing of air into the pulp fluid and its impact on the dynamics of the pulp phase is investigated.Experimentally measured driving torque from the laboratory tumbling mill was compared with numerically predicted torque from the multi-phase fluid simulations. It was clear that the node (particle) based finite element method, using multiple fluid phases and coupled to the FEM solver, was capable of predicting torque from FSI. It was also concluded that the interface between fluids with large differences in viscosity and density could be modelled.The interface tracking between air and magnetite pulp and the mixture of air into the magnetite pulp phase in the form of bubbles is shown in Fig. 2. From the experiments it was concluded that the pulp fluid had a tendency of sticking to the mill structure, this was also predicted by the multi-phase model as can be seen in Fig. 2.

  • 16.
    Larsson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Nishida, Masahiro
    Nagoya Institute of Technology.
    Kurano, Shuhei
    Nagoya Institute of Technology.
    Moroe, Tomoki
    Nagoya Institute of Technology.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Modelling and characterisation of the high-rate behaviour of rock material2018Ingår i: EPJ Web of Conferences: DYMAT 2018 - 12th International Conference on the Mechanical and Physical Behaviour of Materials under Dynamic Loading, 2018, Vol. 183, artikel-id 01040Konferensbidrag (Refereegranskat)
    Abstract [en]

    For future reliable numerical simulations of impact wear on steel structures caused by rock material, knowledge about the dynamic mechanical properties of rock material is required. This paper describes the experimental and numerical work to investigate the dynamic mechanical properties of diabase (dolerite), a subvolcanic rock material. In this study, diabase from southern Sweden was used. The impact compressive strength of diabase with a density of 2.63 g/cm3 was examined by using the split-Hopkinson pressure bar (Kolsky bar) method. Cylindrical specimens were used, with a diameter of 8.9 mm and a length of 14 mm. To characterise the rock material, uniaxial compression tests were performed, at high strain rates (150 s-1). Using an inverse modelling approach, material parameters for an elastic constitutive model, with a stress-based fracture criterion were determined. The constitutive model was used in a finite element simulation of a high strain rate uniaxial compression test. Results obtained from the numerical model were in line with the experimental results.

  • 17.
    Larsson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Parian, Mehdi
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    A novel approach for modelling of physical interactions between slurry, grinding media and mill structure in stirred media millsManuskript (preprint) (Övrigt vetenskapligt)
  • 18.
    Larsson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Pålsson, Bertil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Parian, Mehdi
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Preliminary validation of a stirred media mill model2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wet fine grinding is an important process in the minerals industry. Modelling of wet grinding in stirred media mills is challenging since it requires the simultaneous modelling of grinding media consisting of a huge number of small grinding bodies, moving internal stirrer, and the pulp fluid. All of them in interaction with each other. In the present study, wet grinding in a stirred media mill is studied using coupled incompressible computational fluid dynamics (ICFD) and discrete element method (DEM) and finite element method (FEM) simulations. The DEM is used to model the grinding media, and the pulp fluid flow is modelled using the ICFD. Moreover, the FEM is used to model the structure of the mill body and is in combination with DEM used to estimate the wear rate in the system. The present implementation of the coupled ICFD-DEM-FEM preserves the robustness and efficiency of both methods, and it gives the possibility to use large time steps for the fluid with very low computation times.

  • 19.
    Larsson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Rodriguez Prieto, Juan Manuel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    The particle finite element method for transient granular material flow: modelling and validationManuskript (preprint) (Övrigt vetenskapligt)
  • 20.
    Neikter, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Pederson, Robert
    Department of Engineering Science, University West.
    Antti, Marta-Lena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Åkerfeldt, Pia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Larsson, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Puyoo, Geraldine
    GKN-Aerospace Engine Systems.
    Defect characterization of electron beam melted Ti-6Al-4V and Alloy 718 with X-ray microtomography2018Ingår i: Aeronautics and Aerospace Open Access Journal, ISSN 2576-4500, Vol. 2, nr 3, s. 139-145Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electron beam melting (EBM) is emerging as a promising manufacturing process where metallic components are manufactured from three-dimensional (3D) computer aided design models by melting layers onto layers. There are several advantages with this manufacturing process such as near net shaping, reduced lead times and the possibility to decrease weight by topology optimization, aspects that are of interest for the aerospace industry. In this work two alloys, Ti-6Al-4V and Alloy 718, widely used within the aerospace industry were investigated with X-ray microtomography (XMT), to characterize defects such as lack of fusion (LOF) and inclusions. It was furthermore possible to view the macrostructure with XMT, which was compared to macrostructure images obtained by light optical microscopy (LOM). XMT proved to be a useful tool for defect characterization and both LOF and un-melted powder could be found in the two investigated samples. In the EBM built Ti-6Al-4V sample high density inclusions, believed to be composed of tungsten, were found. One of the high-density inclusions was found to be hollow, which indicate that the inclusion stems from the powder manufacturing process and not related with the EBM process. By performing defect analyses with the XMT software it was also possible to quantify the amount of LOF and un-melted powder in vol%. From the XMT-data meshes were produced so that finite element method (FEM) simulations could be performed. From these FEM simulations the significant impact of defects on the material properties was evident, as the defects led to high stress concentrations. It could moreover, with FEM, be shown that the as-built surface roughness of EBM material is of importance as high surface roughness led to increased stress concentrations.

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