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Sökning: WFRF:(Gustafsson Hans Åke) > Konferensbidrag

  • Resultat 1-10 av 27
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1.
  • Aamodt, K., et al. (författare)
  • Alignment of the ALICE Inner Tracking System with cosmic-ray tracks
  • 2010
  • Ingår i: Journal of Instrumentation. - 1748-0221. ; 5
  • Konferensbidrag (refereegranskat)abstract
    • ALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 mu m in some cases (pixels). The sources of alignment information include survey measurements, and the reconstructed tracks from cosmic rays and from proton-proton collisions. The main track-based alignment method uses the Millepede global approach. An iterative local method was developed and used as well. We present the results obtained for the ITS alignment using about 10(5) charged tracks from cosmic rays that have been collected during summer 2008, with the ALICE solenoidal magnet switched off.
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2.
  • Adare, A., et al. (författare)
  • PHENIX Collaboration
  • 2019
  • Ingår i: XXVIIth International Conference on Ultrarelativistic Nucleus–Nucleus Collisions (Quark Matter 2018). - 0375-9474. ; 982, s. 1053-1059
  • Konferensbidrag (refereegranskat)
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3.
  • Adare, A., et al. (författare)
  • PHENIX Collaboration
  • 2016
  • Ingår i: ; , s. 964-970
  • Konferensbidrag (refereegranskat)
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4.
  • Gustafsson, Gustaf, et al. (författare)
  • Comparison of smoothed particle method and particle finite element method in applied granular flow problems
  • 2009
  • Ingår i: Particle-Based Methods. - Barcelona : International Center for Numerical Methods in Engineering (CIMNE). - 9788496736825 ; , s. 204-207
  • Konferensbidrag (refereegranskat)abstract
    • 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.
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5.
  • Gustafsson, Gustaf, et al. (författare)
  • Modelling and simulation of high velocity loaded iron powder
  • 2012
  • Konferensbidrag (refereegranskat)abstract
    • 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.
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6.
  • Gustafsson, Gustaf, et al. (författare)
  • Modelling and simulation of iron ore pellets
  • 2013
  • Konferensbidrag (refereegranskat)abstract
    • 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.
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7.
  • Gustafsson, Gustaf, et al. (författare)
  • Numerical Prediction of Fracture in Iron Ore Pellets During Handling and Transportation
  • 2017
  • Konferensbidrag (refereegranskat)abstract
    • 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.
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8.
  • Gustafsson, Gustaf, et al. (författare)
  • Simulation of metal powder die filling processes using smoothed particle hydrodynamics method
  • 2007
  • Ingår i: Proceedings. - Shrewsbury : European powder metallurgy association. - 9781899072316 ; , s. 311-316
  • Konferensbidrag (refereegranskat)abstract
    • 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.
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9.
  • Gustafsson, Gustaf, et al. (författare)
  • Simulation of stresses in iron ore pellets for confined compression-tests using the multi particle finite element method
  • 2011
  • Konferensbidrag (refereegranskat)abstract
    • 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.
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  • Resultat 1-10 av 27

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