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  • 1.
    Cante, J.
    et al.
    E.T.S. d’Enginyeries Industrial i Aeronáutica de Terrassa, Technical University of Catalonia (UPC), Campus Terrassa UPC.
    Dávalos, C.
    International Center for Numerical Methods in Engineering (CIMNE), C/. Gran Capitan s/n, 08034 , Barcelona.
    Hernández, J.A.
    E.T.S. d’Enginyeries Industrial i Aeronáutica de Terrassa, Technical University of Catalonia (UPC), Campus Terrassa UPC.
    Oliver, J.
    E.T.S. d’Enginyers de Camins, Canals i Ports de Barcelona, Technical University of Catalonia (UPC), Campus Nord UPC.
    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.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    PFEM-based modeling of industrial granular flows2014Ingår i: Computational Particle Mechanics, ISSN 2196-4378, Vol. 1, nr 1, s. 47-70Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The potential of numerical methods for the solution and optimization of industrial granular flows problems is widely accepted by the industries of this field, the challenge being to promote effectively their industrial practice. In this paper, we attempt to make an exploratory step in this regard by using a numerical model based on continuous mechanics and on the so-called Particle Finite Element Method (PFEM). This goal is achieved by focusing two specific industrial applications in mining industry and pellet manufacturing: silo discharge and calculation of power draw in tumbling mills. Both examples are representative of variations on the granular material mechanical response—varying from a stagnant configuration to a flow condition. The silo discharge is validated using the experimental data, collected on a full-scale flat bottomed cylindrical silo. The simulation is conducted with the aim of characterizing and understanding the correlation between flow patterns and pressures for concentric discharges. In the second example, the potential of PFEM as a numerical tool to track the positions of the particles inside the drum is analyzed. Pressures and wall pressures distribution are also studied. The power draw is also computed and validated against experiments in which the power is plotted in terms of the rotational speed of the drum.

  • 2.
    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.

  • 3.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Experimental measurement and numerical modelling of powder filling2014Konferensbidrag (Refereegranskat)
  • 4.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Mechanical characterization and modelling of iron ore pellets2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Transportation and storage are important parts in the process chain for producers of iron ore pellets. Knowledge and optimization of these processes are very important for further efficiency progress and increased product quality. The existence of a numerical simulation tool with accurate material characteristics will significantly increase the possibility to predict critical forces in developing new and existing transportation and storing systems and thereby decrease the amount of damaged, fractured or crushed pellets (fines). The objective is to increase the knowledge of the mechanical stresses in iron ore pellets and its effects on the level of damaged material in the handling chain. This includes a better understanding of the iron ore pellets mechanical properties and fracture behaviour. Both experimental and numerical modelling works have been completed to increase the knowledge in these fields. Modelling and characterization of iron ore pellets are carried out at different length scales. Material parameters for an elastic plastic granular continuum material model are determined for modelling large quantities of iron ore pellets. A flow model of iron ore pellets in silos using smoothed particle (SP) method is presented. From experimental two point load tests, a finite element (FE) model of single iron ore pellets is worked out with statistical data for an elastic plastic constitutive model with a fracture criterion. In order to find the relation between the behaviour of iron ore pellets at different length scales, e.g. compare the stresses in a silo to the critical stress inside a single iron ore pellet, mechanical testing and modelling of iron ore pellets on an intermediate length scale is established. A method of instrumented confined compression tests is developed for measuring the global response on a limited amount of iron ore pellets. The same experiment is virtually reproduced with a multi particle finite element model (MPFEM) consisting of individual discretized models of the iron ore pellets. This work has given a better understanding of the mechanical behaviour and fracture of iron ore pellets. Another outcome is refined experimental methods to determine mechanical properties and fracture of iron ore pellets. Constitutive data and numerical models for iron ore pellets are also worked out.

  • 5.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Simulation of iron ore pellets and powder flow using smoothed particle method2008Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Handling of iron ore pellets is an important part in the converting process for LKAB. Knowledge about this sub process is very important for further efficiency progress and increased product quality. The existence of a simulation tool with modern modelling and simulation methods will significantly increase the possibility to predict the critical forces in product development processes and thereby decrease the amount of crushed pellets (fines). In this work, simulations of granular material flows on a global scale are performed. From the simulations, properties like flow pattern and density distribution are studied. The methodology is suitable for different applications of particle flows. The particles could be stones, ore, ore pellets, metal powder and other granular materials. Previous studies exploring flow patterns and stress fields in granular solids are analysed with experiments or with numerical methods such as discrete element (DE) method or finite element (FE) computations. In this work, the smoothed particle (SP) method is used to simulate granular material flow. It is a mesh-free continuum-based computational technique where each calculation node is associated with a specific mass, momentum and energy. Properties within the flow such as density and movements of the nodes results from summations via a kernel function of the neighbours of each node to solve the integration of the governing equations. The fact that there are no connections between the nodes in the SP method, results in a method that handles extremely large deformations and still has the advantages of a continuum-based method. This is a major advantage versus FE and DE analysis. Within the current thesis, two applications of simulating granular material with SP analysis is presented: iron ore pellets flow in a flat bottomed silo and simulation of shoe filling of metal powder into simple and stepped dies. In the first application, primarily the flow pattern, when discharging a silo with pellets, is studied and compared with experimental results. Next application focuses on the filling behaviour and density distribution in metal powder shoe filling. For trustworthy numerical simulations of iron ore pellets flow, knowledge about their mechanical properties is needed. In this work, an elastic-plastic material characterization for blast furnace pellets is evaluated from experimental data. Constitutive data in vein of two elastic parameters and a yield function for the pellets bulk material is determined. The present study is an important step towards a simulation tool to predict the critical load in different handling systems of pellets.

  • 6.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Simulering av järnmalmpelletsflöde med SPH2007Ingår i: Svenska Mekanikdagar 2007: Program och abstracts / [ed] Niklas Davidsson; Elianne Wassvik, Luleå: Luleå tekniska universitet, 2007, s. 82-Konferensbidrag (Övrigt vetenskapligt)
  • 7. Gustafsson, Gustaf
    et al.
    Cante, Juan Carlos
    Escola Tècnica Superior d'Enginyeries Industrial i Aeronàutica de Terrassa.
    Jonsén, Pär
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Weyler, Rafael
    Escola Tècnica Superior d'Enginyeries Industrial i Aeronàutica de Terrassa.
    Comparison of smoothed particle method and particle finite element method in applied granular flow problems2009Ingår i: Particle-Based Methods: Fundamentals and Applications / [ed] Eugenio Oñate; Roger Owen, Barcelona: International Center for Numerical Methods in Engineering (CIMNE), 2009, s. 204-207Konferensbidrag (Refereegranskat)
    Abstract [en]

    Traditionally, discrete element (DE) method and finite element (FE) method are used in numerical simulation of granular flow problems. A drawback with the (DE) method is the limitations in modelling the extreme large number of particles, which normally are in real granular flow problems. With a numerical method based on continuum mechanics modelling like the FE-method, the problems can be solved with less computation particles. However, the limitations of the FE-method have been pointed out to be when extremely large deformation needs to be captured. Granular flow problem motions produce large distortions of the mesh and ruin the convergence of the problem. The purpose of this paper is to compare two alternative continuum based methods, the Particle Finite Element Method (PFEM) and the Smoothed Particle (SP) method, to model two different granular flow problems.

  • 8. Gustafsson, Gustaf
    et al.
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Simulation of metal powder die filling processes using smoothed particle hydrodynamics method2007Ingår i: Proceedings: PM in Toulouse - at the forefront of european technology; 15 - 17 October 2007, Pierre Baudis Congress Centre, Toulouse, France, Shrewsbury: European powder metallurgy association , 2007, Vol. 3 : Powder pressing : sintering ; full density & alternative consolidation ; modelling ; secondary & finishing operations, s. 311-316Konferensbidrag (Refereegranskat)
    Abstract [en]

    The die filling is an important stage in the manufacturing process of powder metallurgical components as proceeding stages are influenced by the powder distribution achieved by the filling process. Numerical simulation is a powerful tool in process development and can be used to increase the knowledge about the filling behaviour. In this work smoothed particle hydrodynamics (SPH) method is used to simulate shoe filling of metal powder into simple and stepped dies. An elastic-plastic material model is used as constitutive model where the material parameters are estimated using results from filling rate experiments and loose powder shear tests. The powder flow behaviour and packing density is simulated and compared with experimental results. The results indicate that SPH simulations can capture major observed features of powder die filling.

  • 9.
    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.
    Simulation of the confined compression test of iron ore pellets using random distributed 3D multi particle finite elements2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this work, a multi particle finite element model is used to simulate the axial compression of iron ore pellets inside a steel cylinder. Each individual pellet is discretized with a 3D finite element mesh. From experiment, the load, displacement and the circumferential strain are measured. Experimental results are compared with simulation results.

  • 10.
    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.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Characterization modelling and validation of a two-point loaded iron ore pellet2013Ingår i: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 235, s. 126-135Artikel i tidskrift (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. In the transportation from the pelletizing plants to the customers, the iron ore pellets are exposed to different stresses, resulting in degradation of strength and in some cases fragmentation. For future reliable numerical simulations of the handling and transportation of iron ore pellets, knowledge about their mechanical properties is needed. This paper describes the experimental and numerical work to investigate the mechanical properties of blast furnace iron ore pellets. To study the load deformation behaviour and the fracture of iron ore pellets, a number of point load tests are carried out and analysed. Material parameters for an elastic–plastic constitutive model with linear hardening for iron ore pellets are derived and expressed in terms of statistical means and standard deviations. Two finite element models are developed for different purposes. For the material parameter determination, a perfectly spherical model is used. The constitutive model is validated with a finite element model based on a representative optically scanned iron ore pellet. The proposed constitutive model is capturing the force displacement relation for iron ore pellets in a two-point load test. A stress based fracture criterion which takes the triaxiality into account is suggested and calculated as the maximum equivalent effective stress dependent on the three principal stresses at fracture. The results of this study show that the equivalent effective stress in the vicinity of the centre of an irregular model of an iron ore pellet is very close to the results of a model of a perfectly spherical iron ore pellet. The proposed fracture criterion indicates fracture in the representative iron ore pellet model coincident with the location of the crack developed during the test of the optically scanned iron ore pellet.

  • 11.
    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.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Modelling and simulation of iron ore pellets2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Transportation and storage are important parts in the process chain for producers of iron ore pellets. Knowledge and optimization of these processes are very important for further efficiency progress and increased product quality. The existence of a numerical simulation tool with accurate material characteristics will significantly increase the possibility to predict critical forces in developing new and existing transportation and storing systems and thereby decrease the amount of damaged, fractured or crushed pellets (fines). In this work modelling and simulation of iron ore pellets are carried out at different length scales. An elastic plastic granular continuum flow model for iron ore pellets using smoothed particle (SP) method is presented [1]. The model is used to model iron ore pellets silo flow. A finite element (FE) model of single iron ore pellets is also worked out with statistical data for an elastic plastic constitutive model with a fracture criterion [2]. The model is used to simulate loading and fracture on single iron ore pellets and is validated with a two point load test. In order to find the relation between the behaviour of iron ore pellets at different length scales, e.g. compare the stresses in a silo to the critical stress inside a single iron ore pellet, modelling of iron ore pellets on an intermediate length scale is established. A multi particle finite element model (MPFEM) consisting of individual discretized models of the iron ore pellets is here presented [3]. An instrumented confined compression tests is developed for measuring the global response on a limited amount of iron ore pellets [4]. The experiment is used to validate the MPFEM model in terms of the amount of broken pellets.

  • 12.
    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.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Multi-particle finite element modelling of the compression of iron ore pellets with statistically distributed geometric and material data2013Ingår i: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 239, s. 231-238Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The multi-particle finite element method (MPFEM) is used to simulate confined compression of iron ore pellets. The confined compression test consists of a cylindrical steel tube and two compressive platens. The iron ore pellets are confined by the tools and compressed. In the MPFEM model of the test, the iron ore pellets are represented by 1680 finite element (FE) discretised particles (7-16 mm). The size, shape and material properties of the pellets are statistically distributed. The contacts are modelled using the penalty stiffness method and Coulomb friction. The compression is simulated in two steps. In the first step, the iron ore pellet models are sparsely placed in the computational model of the steel tube and a gravity-driven simulation is conducted to make the pellets arrange themselves randomly. In a second step, the compression is simulated by a prescribed motion of the upper compressive platen. From the MPFEM simulation, the stresses inside the individual pellet models are evaluated, and the fracture probability of the iron ore pellets is derived and compared with experimental data. In addition, data on the global axial and radial stresses and axial displacement are presented and compared with experimental confined compression test data. The MPFEM model can reproduce the fracture ratio of iron ore pellets in uniaxial confined compression and is a feasible method for virtual fracture experiments of iron ore pellets.

  • 13.
    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.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Simulation of stresses in iron ore pellets for confined compression-tests using the multi particle finite element method2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Numerical simulation of the compaction of granular materials is an area of active research. One approach is to use deformable discrete elements of the individual particles using a 2D finite element (FE) mesh, see e.g. [1] and [2]. In this work, the axial compression of iron ore pellets inside a steel cylinder is studied and the individual particles are discretized with a coarse FE mesh in 3D. One possibility of this model is to study the stresses and strains inside the granular particles. Experiment and simulation of iron ore pellets in a confined compression test are done. The experiment consists of an upper and lower piston of thick circular steel plates surrounded by a 2 mm steel cylinder containing the iron ore pellets. The total mass of the iron ore pellets is 46.0kg. During a test, an axial load is applied on the lower piston to a certain level and then unloaded. Measured data are the force and displacement of the lower piston. In addition, strain gauges are measuring the circumferential strain in the middle of the steel membrane. Experimental compression tests between two plates of 18 randomly chosen iron ore pellets were done in order to characterize the load displacement behaviour of the individual pellets. FE models of the experimental tested pellets were carried out and simulated. Each pellet was discretized with an eight-node FE mesh. An elasto-plastic material model with linear hardening is used. The Young’s modulus, the plastic hardening modulus, and the yield stress of the material model were found by inverse modelling. Different material parameters were tested systematically in the FE model and compared with the experimental results until the same load displacement curve was obtained. A multi particle finite element model (MPFEM) was used to simulate the confined compression test. The iron ore pellets are represented in a quarter-model of the real experimental setup by 4756 discretized particles (7-16 mm) with a normal distribution measured from size distribution in the experiment. The contacts are modelled with the penalty stiffness method. The pistons are considered rigid in the simulation and the steel cylinder is modelled with thin elastic shell elements. The compression is simulated in two steps. In the first step, the iron ore pellets models are randomly sparse placed the cylinder and a gravity driven simulation is carried out where the pellets are arranged in the cylinder. In the second step, the compression is simulated by a prescribed displacement of the upper piston. Compared data from the experiment and simulation are; fill density, force-displacement curve and circumferential strain. A relation between the global stress state from the loading of the piston and the maximum stresses inside the individual iron ore pellets was carried out from the simulation. References [1] A.T. Procopio, A. Zavaliangos. “Simulation of multi-axial compaction of granular media from loose to high relative densities”, Journal of the Mechanics and Physics of Solids, 53 pp. 1523-1551, 2005. [2] D.T. Gethin, R.S. Ransing, R.W. Lewis, M. Dutko, A.J.L. Crook, “Numerical comparison of a deformable discrete element model and an equivalent continuum analysis for the compaction of ductile porous material”, Computers and Structures, 79 pp. 1287-1294, 2001.

  • 14.
    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.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Simulation of stresses in iron ore pellets for confined compression-tests using the multi particle finite element method2011Konferensbidrag (Refereegranskat)
  • 15.
    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.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Determination of bulk properties and fracture data for iron ore pellets using instrumented confined compression experiments2013Ingår i: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 241, s. 19-27Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, an experimental method for measuring the bulk properties and fracture loading relations for iron ore pellets is presented. Knowledge on the bulk behaviour and fracture data for iron ore pellets is of great importance for improving the material transportation systems and to increase the product quality. Trustworthy numerical simulations of iron ore pellets also demand reliable materials data for the models. Here, instrumented confined compression tests are carried out at different load levels. Measurement data of the axial and radial stresses and the axial displacement are recorded for each test. Measurements of fractured iron ore pellets are carried out at different loads giving rise to crushing up to 20% of the total material. From the measured data, the Poisson´s ratio, the bulk modulus and a plastic strain hardening function are determined. In addition, friction measurements of iron ore pellets are carried out at different loads and configurations. In conclusion, the test method developed here is usable for the determination of the bulk properties and fracture characteristics of iron ore pellets.

  • 16.
    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.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Nishida, Masahiro
    Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Japan, Nagoya Institute of Technology.
    High-rate behaviour of iron ore pellet2015Ingår i: EPJ Web of Conferences, ISSN 2101-6275, E-ISSN 2100-014X, Vol. 94, artikel-id 5003Artikel i tidskrift (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. In the transportation from the pelletizing plants to the customers, the iron ore pellets are exposed to different loading situations, resulting in degradation of strength and in some cases fragmentation. For future reliable numerical simulations of the handling and transportation of iron ore pellets, knowledge about their mechanical properties is needed. This paper describes the experimental work to investigate the dynamic mechanical properties of blast furnace iron ore pellets. To study the dynamic fracture of iron ore pellets a number of split Hopkinson pressure bar tests are carried out and analysed

  • 17.
    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.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Experimental characterization of constitutive data of iron ore pellets2009Ingår i: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 194, nr 1-2, s. 67-74Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For trustworthy numerical simulations of iron ore pellets flow, knowledge about the mechanical properties of pellets is needed. In this work, an elastic-plastic continuum material model for blast furnace iron ore pellets is worked out from an experimental data. The equipment used is a Norwegian simple shear apparatus, designed for compression and shear test of granular material with a grain size less than 100 mm. It consists of a cylindrical cell filled with pellets surrounded by a rubber membrane and a rigid top and bottom. Two types of tests are performed. One test is pure compression and unloading and the second is shearing at different stress levels. Evaluation of these tests is performed and the elastic-plastic behaviour of iron ore pellets is characterized. Determined constitutive data are two elastic parameters and a yield function. The presented material model captures the major characteristics of the pellets even though it is too simple to completely capture the complex behaviour shown in the experiments.

  • 18.
    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.

  • 19.
    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.

  • 20. Gustafsson, Gustaf
    et al.
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Smoothed particle hydrodynamic simulation of iron ore pellets flow2007Ingår i: Materials Processing and Design: Modeling, Simulation and Applications: NUMIFORM 2007, Proceedings of the 9th International Conference on Numerical Methods in Industrial Forming Processes / [ed] José M. A. César de Sá; Abel D. Santos, Melville, NY: American Institute of Physics (AIP), 2007, Vol. 908, s. 1483-1488Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this work the Smoothed Particle Hydrodynamics (SPH) method is used to simulate iron ore pellets flow. A continuum material model describing the yield strength, elastic and plastic parameters for pellets as a granular material is used in the simulations. The most time consuming part in the SPH method is the contact search of neighboring nodes at each time step. In this study, a position code algorithm for the contact search is presented. The cost of contact searching for this algorithm is of the order of Nlog2N, where N is the number of nodes in the system. The SPH-model is used for simulation of iron ore pellets silo flow. A two dimensional axisymmetric model of the silo is used in the simulations. The simulation results are compared with data from an experimental cylindrical silo, where pellets are discharged from a concentric outlet. Primary the flow pattern is compared.

  • 21.
    Gustafsson, Gustaf
    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.
    Smoothed particle simulation and validation of powder filling2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Powder pressing is often a complicated process as the behaviour of the powder material changes with increasing density. Manufactures tend to produce components with more complicated shapes which demand complex 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 high powder flow during filling affects the strength of the final component significantly. Experimental studies combined with simulations is likely to improve the understanding of the filling stage, e.g. to explain the non-homogeneity of the density of powder pressed parts. This work covers both experimental measurements and umerical modelling of powder filling. Experimental measurements with digital speckle photography (DSP) is used to study the powder behaviour and for the characterisation of the die filling as part of the process in powder pressing. TheDSP measurements are carried out 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, field data during the filling process can be visualised such as velocity fields and strain fields. These measurements are also supporting the development of a numerical model of the process. In this workthe smoothed particle method (SPH) is used to model the powder filling process. The numerical results are compared with the DSP measurements. The validated model is then used to study the process in more detail, e.g. to evaluate the density distribution after filling. The comparison of DPS measurements and simulations gives similar flow characteristics. Experimental measurements with DSP together with numerical simulation with the SP method are powerful tools to increase the knowledge of powder filling and to improve the process in the future is concluded.

  • 22.
    Gustafsson, Gustaf
    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.
    Kato, Hidinori
    Nagoya Institute of Technology.
    Nishida, Masahiro
    Nagoya Institute of Technology.
    Modelling and simulation of high velocity loaded iron powder2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    High velocity compaction is a production technique with capacity to significantly improve the mechanical properties of powder metallurgy (PM) parts. The dynamic testing is performed using a modified split Hopkinson pressure bar (SHPB). A specimen is placed between two elastic bars. The impact loading is achieved by a projectile accelerating inside an air gun, which impacts the end of an input bar creating elastic wave propagation. This process is modelled and simulated by using finite element method. The stress and strain history in the specimen during impact are compared with the evaluated experimental values from the strain measured on the input and output bars. The powder material used for the experiments was a press-ready premix containing Distaloy AE, 0.5% graphite and 0.6% Kenolube. In order to model the impact process a constitutive relation describing the powder behaviour taking into account the strain-rate and density variations are proposed. In conclusion, the proposed material model captures the increase in yield stress due to higher strain rates.

  • 23.
    Gustafsson, Gustaf
    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.
    Kato, Hidinori
    Nagoya Institute of Technology.
    Ogura, Takashi
    Nagoya Institute of Technology.
    Nishida, Masahiro
    Nagoya Institute of Technology.
    Strain Rate Dependent Constitutive Model with Failure for Impact Loading of Metal Powder2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Few studies have been conducted to investigate the strain rate behavior of metal powders. To achieve better understanding of the strain rate dependency of metal powders, it's necessary to conduct dynamic experiments and numerical simulations e.g. using finite element method. High strain rate experiments of iron powder material have been conducted using the split Hopkinson pressure bar method [1]. The dynamic testing is performed using a modified split Hopkinson pressure bar (Kolsky bar). A specimen is placed between two elastic bars. The impact loading is achieved by a projectile accelerating inside an air gun, which impacts the end of an input bar creating elastic wave propagation. The powder material used for the experiments was a press-ready premix containing Distaloy AE, 0.5% graphite and 0.6% Kenolube. This process is modeled and simulated by using finite element method. In order to model the impact process a constitutive relation describing the powder behavior taking into account the strain-rate and density variations are proposed [2]. The stress and strain history in the specimen during impact is validated against the experimental measurements. To capture the global response caused by cracking during impact, a failure criterion is implemented. In conclusion, the proposed material model captures the increase in yield stress due to higher strain rates and the decrease in stress due to cracking.

  • 24.
    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)

     

  • 25.
    Gustafsson, Gustaf
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Nishida, Masahiro
    Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Japan, Nagoya Institute of Technology.
    Häggblad, Hans-åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Ito, Yoshikata
    Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Japan.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Takayama, Tetsuo
    Yamagata University.
    Todo, Mitsugu
    Kyushu University, Kyushu University, 6-1, Kasuga-koen, Kasuga, Fukuoka, Japan.
    Mechanical characterization and modelling of the temperature-dependent impact behaviour of a biocompatible poly(L-lactide)/poly(ε-caprolactone) polymer blend2015Ingår i: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 51, s. 279-290Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Poly(ε-caprolactone) (PCL) is a ductile, bioabsorbable polymer that has been employed as a blend partner for poly(L-lactic acid) (PLLA). An improvement of the material strength and impact resistance of PLLA/PCL polymer blends compared to pure PLLA has been shown previously. To use numerical simulations in the design process of new components composed of the PLLA/PCL blend, a constitutive model for the material has to be established. In this work, a constitutive model for a PLLA/PCL polymer blend is established from the results of compressive tests at high and low strain rates at three different temperatures, including the body temperature. Finite element simulations of the split Hopkinson pressure bar test using the established constitutive model are carried out under the same condition as the experiments. During the experiments, the changes in the diameter and thickness of the specimens are captured by a high-speed video camera. The accuracy of the numerical model is tested by comparing the simulation results, such as the stress, strain, thickness and diameter histories of the specimens, with those measured in the experiments. The numerical model is also validated against an impact test of non-homogenous strains and strain rates. The results of this study provide a validated numerical model for a PLLA/PCL polymer blend at strain rates of up to 1800 s−1 in the temperature range between 22 °C and 50 °C.

  • 26.
    Gustafsson, Gustaf
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Nishida, Masahiro
    Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Japan.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Kato, Hidinori
    Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Japan.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Ogura, Takashi
    Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Japan.
    Experimental studies and modelling of high-velocity loaded iron-powder compacts2014Ingår i: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 268, s. 293-305Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A production technique with the capacity to significantly improve the mechanical properties of powder metallurgy (PM) parts is high-velocity compaction (HVC). To extend the usage of the HVC method, detailed knowledge of the HVC process is important. To facilitate the development of production processes, numerical simulations can be utilised. In the development of high-precision simulation models, constitutive data of HVC specimens at high strain rates are required. In this study, the dynamic compressive properties of cylindrical specimens made by HVC were measured using a split Hopkinson pressure bar (Kolsky bar) assembly. For this technique, a specimen is placed between two elastic bars. The impact loading is achieved by a projectile accelerating inside an air gun, which impacts the end of the input bar and generates elastic-wave propagation.The powder material used for the experiments is a press-ready iron-based premix. Among specimens made by HVC and conventional compaction (CC), the effects of the specimen density and the strain rate on the compressive properties, such as failure stress, Young´s modulus and failure behaviour, are investigated. During dynamic compression, the failure behaviour of the specimens was also recorded using a high-speed video camera. The difference in the mechanical behaviour between HVC-pressed specimens and conventionally pressed specimens are also investigated. The stress–strain curves of HVC-pressed specimens are identical to those of conventionally pressed specimens, but the failure behaviour differs are concluded.A well-established numerical method for forming simulations also conducted for powder compaction is the finite element method (FEM). The impact loading of the powder is modelled and simulated using nonlinear three-dimensional FEM. To model the impact process, a constitutive relation for the powder behaviour is proposed, taking into account the strain rate and density variations. To capture the global response caused by cracking during impact, a damage model is implemented. The numerical results in terms of the stress and strain history in the specimen during impact are compared with the experimental measurements. In conclusion, the proposed material model captures the increase in the yield stress due to the higher strain rates and the decrease in stress due to cracking.

  • 27.
    Hjortsberg, Erik
    et al.
    LKAB.
    Forsberg, Fredrik
    LKAB.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Rutqvist, Elin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    X-ray microtomography for characterisation of cracks in iron ore pellets after reduction2013Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 40, nr 6, s. 399-406Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work presents a method, based on X-ray microtomography and three-dimensional (3D) image analysis, of characterising and quantifying crack distribution in iron ore pellets. The aims have been to verify the method and to determine to what extent crack propagation contributes to the decrease in compressive strength that occurs during reduction at 500°C as haematite transforms into magnetite. Raw materials known to cause disintegration problems were selected in order to promote crack propagation. Pellets displayed crack lengths of sizes roughly corresponding to half the pellet diameter already before reduction and, during reduction, a further crack propagation of ∼50% occurred. Through estimations by finite element analysis of the crack size and the pellet geometry, it has been possible to determine that this crack growth most likely is a mechanism that contributes to the decrease in compressive strength. The decrease of ∼90% that was experimentally determined to occur after 30 min of reduction is, however, too large to be explained by crack propagation alone. The study shows that the proposed techniques allow 3D imaging of iron ore pellets and characterisation of cracks. The scans are non-destructive and can be carried out repeatedly, which allows a specific sample to be studied at different stages during a process. Through future use of the proposed method, our aim is to reach a deeper understanding of the mechanisms behind low temperature disintegration of iron ore pellets and the performance of LKAB olivine pellets inside the blast furnace.

  • 28.
    Häggblad, Hans-åke
    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.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Golling, Stefan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Modelling And Simulation The Cracking Of Green Metal Powder Body2016Ingår i: Proceedings World PM2016 Congress: International Powder Metallurgy Congress & Exhibition 9-13 October 2016, Hamburg, Germany, European Powder Metallurgy Association , 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    During the ejection stage of the powder metallurgy (PM) pressing process the elastic behaviour is important. Especially, if the in the powder compact is unloaded in a non-beneficially manner crack formation can occur. Experiments show a non-linear and also stress dependent elastic behaviour of green bodies. Calibrated against experimental data, a fracture model controlling the stress versus crack-width relationship is used. The softening rate of the fracture model is obtained from the corresponding rate of the dissipated energy. The model is implemented with a smeared crack approach in a finite element code and tested in simulation of a diametral compression testing. Results from simulations correlates well with experimental results. The smeared crack method combined with a cohesive fracture model is an interesting tool for predicting fracture in powder compacts.

  • 29.
    Jonsén, Pär
    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.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Modelling the non-linear elastic behaviour and fracture of metal powder compacts2015Ingår i: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 284, s. 496-503Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the powder metallurgy (PM) pressing process the mechanical properties of the green body are highly dependent on the material density. During the ejection stage of the pressing process the elastic behaviour is important especially for the crack formation in the powder compact. Experiments show a non-linear and also stress dependent elastic behaviour of green bodies. In this study diametral compression tests have been used to study elastic deformation during crack formation in a tensile fracture process of metal powder discs compacts. The powder material used for the experiments was a press-ready premix containing Distaloy AE, 0.5% graphite (uf-4) and 0.6% Kenolube. Tensile strength is used as a failure condition and limits the stress in the fracture interface. To control the tensile fracture, a cohesive zone model is used. The softening rate of the fracture model is obtained from the corresponding rate of the dissipated energy. The deformation of the powder material is modelled with an elastic-plastic cap model where an easy-to-use model for non-linearity in the elastic state due to stress is presented. The model is implemented in a finite element code and tested in simulation of a diametral compression testing. Results from simulations correlates well with experimental results and demonstrates the importance of including the non-linear elastic effect of the powder compacts. Results also show the necessity to accurate model the elasticity in the tooling to correct capture force-displacement response and fracturing processes.

  • 30.
    Jonsén, Pär
    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.
    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 physical interactions between pulp, charge and mill structure in tumbling mills2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    To develop a tumbling mill model that includes the pulp fluid and its simultaneous interactions with both the charge and the mill structure is an interesting challenge. The interactions have previously been modelled for dry grinding with a combination of discrete element method (DEM) or smoothedparticle hydrodynamics (SPH) together with the finite element method (FEM). In such combination the DEM particles or SPH particles represent the grinding balls and FEM is used to model the mill structure. In this work, the previous model is extended to include fluids using SPH. Wet milling with water and a magnetite pulp, for graded and mono-size charges are numerically modelled and validated. The charge behaviour and its interaction with the mill structure are studied. An important part of the model is the coupling between DEM and SPH elements. Sliding and impact along the contacting interfaces are important for the response of the model. In the present work, the contact between the grinding balls and the pulp is realized using a penalty based “nodes to node” contact. The combined SPH-DEM-FEM model presented here can predict responses from the mill structure, as well as the pulp liquid flow and pressure. Validation is conducted by comparing numerical results with experimental measurements from grinding in an instrumented small-scale batch ball millequipped with an accurate torque meter. The simulated charge movement is also compared with high speed video of the charge movement for a number of cases. In conclusion, the SPH-DEM-FEM can predict the charge movement and driving torque with good agreement compared to experimental measurement for a wet tumbling mill process. In addition, the presented methodology is generic and can as well be applied to dry or wet stirred media mills of various configurations

  • 31.
    Kuroyanagi, Yuki
    et al.
    Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Japan.
    Nishida, Masahiro
    Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Japan, Nagoya Institute of Technology.
    Ogura, Takashi
    Nagoya Institute of Technology.
    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.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Effects of aspect ratio and specimen size on uniaxial failure stress of iron green bodies at high strain rates2015Ingår i: EPJ Web of Conferences, ISSN 2101-6275, E-ISSN 2100-014X, Vol. 94, artikel-id 1060Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Powder metallurgy is used for the production of a number of mechanical parts and is an essential production method. These are great advantages such as product cost effectiveness and product uniqueness. In general, however parts created by powder metallurgy have low strength because of low density. In order to increase strength as well as density, new techniques such as high-velocity-compaction (HVC) was developed and further investigation has been conducted on improvement of techniques and optimum condition using computer simulation. In this study, the effects of aspect ratio and specimen size of iron green bodies on failure strength of uniaxial compression and failure behavior were examined using a split Hopkinson pressure Bar. The diameters of specimens were 12.5 mm and 25 mm the aspect ratios (thickness/diameter) were 0.8 and 1.2.

  • 32.
    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.

  • 33.
    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.

  • 34.
    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.

  • 35.
    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)
  • 36.
    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.

  • 37.
    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.

  • 38.
    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.

  • 39.
    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.

  • 40.
    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)
  • 41.
    Nishida, Masahiro
    et al.
    Nagoya Institute of Technology.
    Ito, Yoshitaka
    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.
    Takayama, T.
    Yamagata University.
    Todo, M.
    Kyushu University.
    Determination of dynamic material properties for poly(L-lactic acid)/poly(e-caprolactone) blends: Experiments and simulation using split Hopkinson pressure bars2012Ingår i: EPJ Web of Conferences: DYMAT 2012 - 10th International Conference on the Mechanical and Physical Behaviour of Materials under Dynamic Loading / [ed] S. Hiermaier, Les Ulis: EDP Sciences, 2012, Vol. 26, s. 3001-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Coefficients of Cowper-Symonds constitutive equation for PLLA/PCL = 80/20 were determined using the results of compressive tests at high and low strain rates. The simulation of split Hopkinson pressure bar using the coefficients was carried out under the same condition as the experiments. The diameter and thickness of specimens were measured by a high-speed video camera. The stress and strain histories of specimens, the thickness and the diameter in the simulations at high strain rate were compared with those in the experiments

  • 42.
    Nishida, Masahiro
    et al.
    Nagoya Institute of Technology.
    Kato, Hidinori
    Nagoya Institute of Technology.
    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.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Strain rate effects on constitutive properties of high velocity pressed iron powder2012Konferensbidrag (Refereegranskat)
  • 43.
    Nishida, Masahiro
    et al.
    Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Japan, Nagoya Institute of Technology.
    Kuroyanagi, Yuki
    Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Japan.
    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.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Strain rate effects on tensile strength of iron green bodies2015Ingår i: EPJ Web of Conferences, ISSN 2101-6275, E-ISSN 2100-014X, Vol. 94, artikel-id 1069Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Impact tensile strength of iron green bodies with densities of 7.2 and 7.4 g/cm3 was examined by Brazilian test using the split-Hopkinson pressure bar (Kolsky bar) method. The powder material used for the experiments was a press-ready premix containing Distaloy AE, graphite, and lubricant. During dynamic compression, the failure behavior of specimens was observed using a high-speed video camera. The failure stress and failure behavior of dynamic compressive tests were compared with those of static compressive tests.

  • 44.
    Nishida, Masahiro
    et al.
    Nagoya Institute of Technology.
    Ogura, Takashi
    Nagoya Institute of Technology.
    Kato, Hidinori
    Nagoya Institute of Technology.
    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.
    Gustafsson, Gustaf
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Compressive Properties of High Velocity Pressed Iron Powder at High Strain Rates2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the field of powder metallurgy, high velocity compaction (HVC) is a production technique with capacity to improve the mechanical properties of powder metallurgy parts because high density of powder metallurgy parts can be achieved in less than 0.5 s [1, 2]. In order to extend the usage of the HVC method, detailed knowledge of the HVC process is important. To facilitate development of production processes, numerical simulations can be utilized. A common numerical method for powder compaction is the finite element method (FEM). To conduct on FEM simulation precisely, constitutive data of HVC specimens at high strain-rate are required [3, 4]. In this study, the dynamic compressive properties of cylindrical specimens made by HVC were measured using a Spit Hopkinson Pressure Bar (Kolsky bar). The powder material used for the experiments was a press-ready premix containing Distaloy AE, 0.5% graphite (uf-4) and 0.6% Kenolube. During dynamic compression, the failure behavior of specimens was also observed using a high speed video camera. The experimental results, such as failure stress, Young’s modulus and failure behavior, of dynamic compressive tests were compared with those of static compressive tests. Among specimens made by HVC and Conventional Compaction (CC), the effects of specimen density, 6.9, 7.2 and 7.4 g/cm3, on the compressive properties and failure behavior were also examined. For each density, the difference in the failure behavior between HVC-pressed specimens and conventional pressed specimens was observed, whereas stress-strain curves of HVC-pressed specimens were the same as conventional pressed specimens. Moreover, the effects of specimen size on failure behavior and stress-strain curves of specimens were examined.

  • 45.
    Ramanenka, Dmitrij
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Antti, Marta-Lena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    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.
    Characterization of high-alumina refractory bricks and modelling of hot rotary kiln behaviour2017Ingår i: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 79, s. 852-864Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rotary kilns for iron-ore pellets production are highly dependent on a well-functioning refractory brick lining. To improve the long-term capability of the lining, in-situ observations of the bricks' performance are desired, however, the high process temperatures and the size of the kiln make it difficult to study the lining during operation. By using numerical simulations as a tool, some of the problems encountered by the brick lining can be studied. Knowing material properties of the refractory bricks as input in a numerical model is therefore necessary. However, material properties are poorly documented for this type of materials, especially, at elevated temperatures. In this work three commercial aluminasilicate bricks were tested in compression until failure for a temperature range of 25–1300 °C. The purpose was to evaluate compression strength and Young's modulus in compression of the fully burned bricks at a wide range of temperatures. The data was later used for modelling of a hot rotary kiln lined with bricks by using the finite element method, whereupon load state of the lining was evaluated at steady state after the expansion of the system. The objective of the numerical modelling was to investigate trustworthiness of the model and to give insight into the stress levels that can potentially arise. It was found that for all of the investigated brick types the compression strength increased with increased temperature, having a peak in the vicinity of 1000 °C. The maximum increase was between 50 and 150 % for the different brick types. After passing 1100 °C the compression strength rapidly and considerably decreased below its as-received compression strength. Young's modulus was measured to vary between 2 and 10 GPa in the range of up to 1000 °C. The numerical results indicate that severe boundary conditions (expansion of the lining is highly restricted) can potentially lead to compression stress of up to 34 MPa in the brick lining at steady state. However, at these boundary conditions the present tensile stress was only 0.5 MPa, while tensile stresses of close to 3 MPa could be observed in the lining with mild boundary conditions. The authors conclude that the created model is trustworthy and that it has high potential for being used as a tool in further investigations of the lining in hot state.

  • 46.
    Ramanenka, Dmitrij
    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.
    Influence of heating and cooling rate on the stress state of the brick lining in a rotary kiln using finite element simulations2019Ingår i: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 105, s. 98-109Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rotary kilns for iron-ore pellets production are highly dependent on a well-functioned refractory brick lining. To improve the long-term capability of the lining, in-situ observations of the bricks' performance are desired, however, the harsh environment inside the rotary kiln makes it difficult or nearly impossible to study the lining during operation. By using numerical simulations as a tool, some of the problems encountered by the brick lining can be studied without limitation of the extreme conditions.

    In this work, stress state of the lining was studied under the influence of different heating and cooling rates, and different brick compaction cases. A finite element model was created for conducting the numerical simulations. The numerical model was calibrated for transient heat transfer. Temperature dependent material properties of the bricks and casing were used as input. The heating and cooling was controlled by temperature prescription on the boundary of the brick lining, while brick lining compaction by defining relative position of the bricks in axial and radial directions.

    The conducted numerical simulations showed that considerable tensile stress may appear in a large area of the brick during initial heating stage. The large tensile area corresponds well with the typical circumferential cracks experienced by the bricks. It was demonstrated that the compressive stresses counteract the development of tensile stresses. However, the compressive stresses may become very large in the initial stage of heating. The positive effect of lower heating rate was considerable on the tensile stresses, while influence on the compressive stresses was almost unnoticed. The hypothetical cooling rates showed that very high tensile stresses may occur on the surface of the bricks, potentially leading to surface spalling. Furthermore, it was demonstrated that axial compaction is highly important on the stress development in the lining, which, may not always be followed in practice. As a general conclusion, it is recommended to always achieve a tight compaction of the brick lining and to take measures for lowering the heating and cooling rates.

    The conducted work exemplifies behaviour of the brick lining for realistic heat transfer and material properties. The insight into the behaviour gives possibilities to make adjustments and directed investments for lowering risk of brick lining failure.

  • 47.
    Ramanenka, Dmitrij
    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.
    Modelling of Hot Rotary Kiln2017Konferensbidrag (Refereegranskat)
  • 48.
    Ramanenka, Dmitrij
    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.
    Nordin, Lars Olof
    Loussavaara-Kiirunavaara Limited, Luleå.
    Evaluation of stress state in a brick lining of a hot rotary kiln due to material and design change2017Ingår i: Proceedings of the World Congress on Mechanical, Chemical, and Material Engineering, Avestia Publishing, 2017Konferensbidrag (Refereegranskat)
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