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Larsson, S. (2019). Particle Methods for Modelling Granular Material Flow. (Doctoral dissertation). Luleå: Luleå University of Technology
Open this publication in new window or tab >>Particle Methods for Modelling Granular Material Flow
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Partikelmetoder för modelleringav granulära flöden
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.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2019
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-73199 (URN)978-91-7790-332-1 (ISBN)978-91-7790-333-8 (ISBN)
Public defence
2019-05-16, E231, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2019-03-15 Created: 2019-03-14 Last updated: 2019-04-26Bibliographically approved
Larsson, S., Pålsson, B., Parian, M. & Jonsén, P. (2019). Preliminary validation of a stirred media mill model. In: : . Paper presented at Conference in Minerals Engineering 2019.
Open this publication in new window or tab >>Preliminary validation of a stirred media mill model
2019 (English)Conference paper, Published paper (Refereed)
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.

National Category
Applied Mechanics Metallurgy and Metallic Materials
Research subject
Solid Mechanics; Mineral Processing
Identifiers
urn:nbn:se:ltu:diva-72951 (URN)
Conference
Conference in Minerals Engineering 2019
Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-02-22
Neikter, M., Forsberg, F., Pederson, R., Antti, M.-L., Åkerfeldt, P., Larsson, S., . . . Puyoo, G. (2018). Defect characterization of electron beam melted Ti-6Al-4V and Alloy 718 with X-ray microtomography. Aeronautics and Aerospace Open Access Journal, 2(3), 139-145
Open this publication in new window or tab >>Defect characterization of electron beam melted Ti-6Al-4V and Alloy 718 with X-ray microtomography
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2018 (English)In: Aeronautics and Aerospace Open Access Journal, ISSN 2576-4500, Vol. 2, no 3, p. 139-145Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
MedCrave Group, 2018
Keywords
X-ray tomography, Ti-6Al-4V, Alloy 718, defects and electron beam melting
National Category
Metallurgy and Metallic Materials Other Materials Engineering Fluid Mechanics and Acoustics Applied Mechanics
Research subject
Engineering Materials; Solid Mechanics; Experimental Mechanics
Identifiers
urn:nbn:se:ltu:diva-68924 (URN)10.15406/aaoaj.2018.02.00044 (DOI)
Available from: 2018-05-28 Created: 2018-05-28 Last updated: 2018-11-08Bibliographically approved
Larsson, S., Gustafsson, G., Jonsén, P. & Häggblad, H.-Å. (2018). DEM-CFD Simulation of the Effect of Air on Powder Flow During Die Filling. In: : . Paper presented at 13th World Congress in Computational Mechanics.
Open this publication in new window or tab >>DEM-CFD Simulation of the Effect of Air on Powder Flow During Die Filling
2018 (English)Conference paper, Oral presentation with published abstract (Refereed)
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.

National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-71547 (URN)
Conference
13th World Congress in Computational Mechanics
Available from: 2018-11-12 Created: 2018-11-12 Last updated: 2018-11-27
Larsson, S., Gustafsson, G., Häggblad, H.-å. & Jonsén, P. (2018). Experimental and numerical study of potassium chloride flow using smoothed particle hydrodynamics. Minerals Engineering, 116, 88-100
Open this publication in new window or tab >>Experimental and numerical study of potassium chloride flow using smoothed particle hydrodynamics
2018 (English)In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 116, p. 88-100Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-62669 (URN)10.1016/j.mineng.2017.11.003 (DOI)000424172900012 ()
Note

Validerad;2018;Nivå 2;2018-01-25 (andbra)

Available from: 2017-03-24 Created: 2017-03-24 Last updated: 2019-03-14Bibliographically approved
Larsson, S., Nishida, M., Kurano, S., Moroe, T., Gustafsson, G., Häggblad, H.-Å. & Jonsén, P. (2018). Modelling and characterisation of the high-rate behaviour of rock material. In: EPJ Web of Conferences: DYMAT 2018 - 12th International Conference on the Mechanical and Physical Behaviour of Materials under Dynamic Loading. Paper presented at DYMAT 2018 - 12th International Conference on the Mechanical and Physical Behaviour of Materials under Dynamic Loading, September 9-14, 2018, Arcachon, France. , 183, Article ID 01040.
Open this publication in new window or tab >>Modelling and characterisation of the high-rate behaviour of rock material
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2018 (English)In: EPJ Web of Conferences: DYMAT 2018 - 12th International Conference on the Mechanical and Physical Behaviour of Materials under Dynamic Loading, 2018, Vol. 183, article id 01040Conference paper, Published paper (Refereed)
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.

National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-71544 (URN)10.1051/epjconf/201818301040 (DOI)
Conference
DYMAT 2018 - 12th International Conference on the Mechanical and Physical Behaviour of Materials under Dynamic Loading, September 9-14, 2018, Arcachon, France
Available from: 2018-11-12 Created: 2018-11-12 Last updated: 2019-01-21Bibliographically approved
Gustafsson, G. & Larsson, S. (2018). Numerical modelling, simulation and validation of icing on a wind turbine blade. In: : . Paper presented at 13th World Congress in Computational Mechanics.
Open this publication in new window or tab >>Numerical modelling, simulation and validation of icing on a wind turbine blade
2018 (English)Conference paper, Oral presentation with published abstract (Refereed)
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)

 

National Category
Applied Mechanics
Identifiers
urn:nbn:se:ltu:diva-71528 (URN)
Conference
13th World Congress in Computational Mechanics
Available from: 2018-11-09 Created: 2018-11-09 Last updated: 2018-11-09
Gustafsson, G., Häggblad, H.-å., Nishida, M., Larsson, S. & Jonsén, P. (2017). Fracture probability modelling of impact-loaded iron ore pellets. International Journal of Impact Engineering, 102, 180-186
Open this publication in new window or tab >>Fracture probability modelling of impact-loaded iron ore pellets
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2017 (English)In: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 102, p. 180-186Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-61326 (URN)10.1016/j.ijimpeng.2016.12.014 (DOI)000393001400017 ()2-s2.0-85008350828 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-01-09 (andbra)

Available from: 2017-01-09 Created: 2017-01-09 Last updated: 2018-09-13Bibliographically approved
Larsson, S. (2017). Modelling and Characterisation of Granular Material Flow. (Licentiate dissertation). Luleå: Luleå University of Technology
Open this publication in new window or tab >>Modelling and Characterisation of Granular Material Flow
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
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.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2017
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-62670 (URN)978-91-7583-853-3 (ISBN)978-91-7583-854-0 (ISBN)
Presentation
2017-06-16, E231, Luleå, 10:00
Available from: 2017-03-28 Created: 2017-03-24 Last updated: 2018-04-12Bibliographically approved
Gustafsson, G., Häggblad, H.-å., Larsson, S. & Jonsén, P. (2017). Numerical Prediction of Fracture in Iron Ore Pellets During Handling and Transportation. In: Barry Wills (Ed.), : . Paper presented at Computational Modelling ‘17, Falmouth, Cornwall, UK June 13-14, 2017.
Open this publication in new window or tab >>Numerical Prediction of Fracture in Iron Ore Pellets During Handling and Transportation
2017 (English)In: / [ed] Barry Wills, 2017Conference paper, Published paper (Refereed)
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.

Keywords
Modelling, Iron ore pellets, fracture
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-65337 (URN)
Conference
Computational Modelling ‘17, Falmouth, Cornwall, UK June 13-14, 2017
Available from: 2017-08-25 Created: 2017-08-25 Last updated: 2018-04-12Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5206-6894

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