Change search
Refine search result
45678910 301 - 350 of 5250
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 301.
    Barkar, Thomas
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ågren, John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Creep simulation of 9-12% Cr steels using the composite model with thermodynamically calculated input2005In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 395, no 1-2, p. 110-115Article in journal (Refereed)
    Abstract [en]

    Creep of 9-12% Cr steels is modeled using the composite model, developed by Blum et al. [R. Sedlacek, W. Blum, Comput. Mater. Sci. 25 (2002) 200], and thermodynamic calculations based on the Calphad approach. The composite model yields a physical description of the deformation behavior of materials that have a pronounced heterogeneous dislocation structure and is briefly surveyed. A few of the input parameters have been thermodynamically calculated using Thermo-Calc and introduced to the main program via a programming interface. This combined approach allows us to simulate the creep deformation behavior with less extensive microstructural investigations. This is a step towards enabling predictions of the creep behavior predominantly based on the nominal composition, heat treatment and mechanical load. Simulation results for two different 9-12% Cr steels are presented.

  • 302. Baroni, M. P. M. A.
    et al.
    Conceicao, M. Ventura
    Rosa, R. R.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Arwin, H.
    da Silva, E. F., Jr.
    Roman, L. S.
    Nakamura, O.
    Pepe, I.
    da Silva, A. Ferreira
    Optical and morphological properties of porous diamond-like-carbon films deposited by magnetron sputtering2006In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 352, no 32-35, p. 3734-3738Article in journal (Refereed)
    Abstract [en]

    Porous diamond-like-carbon (PDLC) thin films obtained on silicon substrate by DC low energy magnetron sputtering have been investigated by photoluminescence, transmission and reflection spectroscopy, photoacoustic and spectroscopic ellipsometry. The absorption features observed for these films show similarities with those of porous silicon (PS) as well as in the performed gradient structural pattern classification of the SFM porosity, by means of the computational GPA-flyby environment on PS and PDLC samples. The dielectric function is also calculated for the bulk diamond-like carbon using the full-potential linearized augmented plane wave method within the framework of local density approximation to density functional theory. From the measurement a low real dielectric constant of about 4.5 at 0.8 eV was found whereas the calculated e(1)(0) for the bulk diamond has a value of 5.5.

  • 303. Baron-Wiechec, A.
    et al.
    Widdowson, A.
    Alves, E.
    Ayres, C. F.
    Barradas, N. P.
    Brezinsek, S.
    Coad, J. P.
    Catarino, N.
    Heinola, K.
    Likonen, J.
    Matthews, G. F.
    Mayer, M.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    van Renterghem, W.
    Uytdenhouwen, I.
    Global erosion and deposition patterns in JET with the ITER-like wall2015In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 463, p. 157-161Article in journal (Refereed)
    Abstract [en]

    A set of Be and W tiles removed after the first ITER-like wall campaigns (JET-ILW) from 2011 to 2012 has been analysed. The results indicate that the primary erosion site is in the main chamber (Be) as in previous carbon campaigns (JET-C). In particular the limiters tiles near the mid-plane are eroded probably during the limiter phases of discharges. W is found at low concentrations on all plasma-facing surfaces of the vessel indicating deposition via plasma transport initially from the W divertor and from main chamber W-coated tiles; there are also traces of Mo (used as an interlayer for these coatings). Deposited films in the inner divertor have a layered structure, and every layer is dominated by Be with some W and O content.

  • 304.
    Barsoum, Imad
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Ductile failure and rupture mechanisms in combined tension and shear2006Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This licentiate thesis is generally concerned with the ductile failure and rupture mechanisms encountered under combined tension and torsion loading. In the first part entitled Paper A, an experimental investigation of the rupture mechanisms in a mid-strength and a high strength steel was conducted employing a novel test configuration. The specimen used was a double notched tube specimen loaded in combined tension and torsion at a fixed ratio. The effective plastic strain, the stress triaxiality and the Lode parameter was determined in the centre of the notch at failure. Scanning electron microscopy of the fractured surfaces revealed two distinctively different ductile rupture mechanisms depending on the stress state. At high stress triaxiality the fractured surfaces were covered with large and deep dimples, suggesting that growth and internal necking of voids being the governing rupture mechanism. At low triaxiality it was found that the fractured surfaces were covered with elongated small shear dimples, suggesting internal void shearing being the governing rupture mechanism. In the fractured surfaces of the high-strength steel, regions with quasi-cleavage were also observed. The transition from the internal necking mechanism to the internal shearing mechanism was accompanied by a significant drop in ductility.

    In the second part entitled Paper B, a micromechanics model based on the theoretical framework of plastic localization into a band introduced by Rice is developed. The model employed consists of a planar band with a square array of equally sized cells, with a spherical void located in the centre of each cell. The periodic arrangement of the cells allows the study of a single unit cell for which fully periodic boundary conditions are applied. The micromechanics model is applied to analyze failure by ductile rupture in experiments on double notched tube specimens subjected to combined tension and torsion carried out by the present authors. The stress state is characterized in terms of the stress triaxiality and the Lode parameter. Two rupture mechanisms can be identified, void coalescence by internal necking at high triaxiality and void coalescence by internal shearing at low triaxiality. For the internal necking mechanism, failure is assumed to occur when the deformation localizes into a planar band and is closely associated with extensive void growth. For the internal shearing mechanism, a simple criterion based on the attainment of a critical value of shear deformation is utilized. The two failure criteria capture the transition between the two rupture mechanisms successfully and are in good agreement with the experimental result.

  • 305.
    Barsoum, Imad
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Faleskog, Jonas
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Micromechanical analysis of rupture mechanisms in mixed mode ductile fracture2006In: Fracture of Nano and Engineering Materials and Structures - Proceedings of the 16th European Conference of Fracture, Kluwer Academic Publishers, 2006, p. 1169-1170Conference paper (Refereed)
  • 306.
    Barsoum, Zuheir
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    HENRY GRANJON PRIZE COMPETITION 2010 Winner Category C: "Design and Structural Integrity" FATIGUE DESIGN OF WELDED STRUCTURES - SOME ASPECTS OF WELD QUALITY AND RESIDUAL STRESSES2011In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 55, no 11-12, p. 2-11Article in journal (Refereed)
    Abstract [en]

    The research work reported in this paper aims to increase the accuracy of fatigue life prediction of welded steel structures using local analysis methods by i) establishing a link between weld quality and fatigue life ii) developing simplified engineering methods using finite element routines for prediction of welding residual stresses iii) incorporating the residual stresses into the fatigue life predictions. Acceptance criteria were developed for the weld quality by comprehensive FE-and fracture mechanical analysis and fatigue testing. The results are the foundation for the new weld class system within the Volvo group company. Simplified FE welding simulation routines and procedures for incorporating the predicted residual stresses into crack growth analysis were developed showing good agreement with residual stress measurements and fatigue testing.

  • 307.
    Barsoum, Zuheir
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Numerical Analysis and Measurement of Residual Stresses in Multi Pass Welding - Influence on Fatigue Root Crack Propagation2006In: TRENDS IN WELDING RESEARCH, PROCEEDINGS / [ed] David SA; DebRoy T; Lippold JC; Smartt HB; Vitek JM, MATERIALS PARK: ASM INTERNATIONAL , 2006, p. 589-594Conference paper (Refereed)
    Abstract [en]

    The purpose of this study is to investigate the residual stresses near the weld root and the weld toe for multi-pass welded tube-to-plates, and the influence of residual stresses on multiaxial fatigue of tubular joints. Two different tubular joint configurations were studied; a three-pass single-U weld groove for maximum weld penetration and a two-pass fillet (no groove) welded tube-to-plates for minimum weld penetration. An axi-symmetric finite element model was developed to calculate the temperature distribution, HAZ, penetration depth and the residual stress distribution for the sequentially coupled thermo-mechanical analysis. The calculated geometry and the temperature distribution of the fusion zone showed good agreement with the micro samples of the welds. The calculated residual stresses was compared with experimental results and showed qualitatively good agreement. The "design root crack" is under compressive stresses in both configuration, -230 MPa for the single-U weld groove and -120 MPa for the fillet weld, respectively. Also the weld toe, transition between weld and tube, is under compressive stresses. Multi-axial fatigue tests were performed in order to study weld root crack propagation. The tube structures were loaded with a static internal pressure in order to separate the design root crack and initiate the crack growth. The fatigue tests show that, depending on the size of the static imposed internal pressure, different crack paths are received.

  • 308.
    Barsoum, Zuheir
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Residual stress prediction and relaxation in welded tubular joints under constant cyclic loading2006In: Residual Stresses VII / [ed] Reimers, W; Quander, S, 2006, Vol. 524-525, p. 323-328Conference paper (Refereed)
    Abstract [en]

    In this paper three-dimensional welding simulations were carried out in FE software ANSYS in order to predict transient temperatures and the residual stresses in a three pass welded tubular joints. The thermal analysis and the moving heat source were verified with temperature measurements and the computed residual stresses were verified with hole drilling measurements. Then residual stress relaxation analyses were carried out on the tubular structure, with similar load cases as in earlier fatigue testing on the same tubular joint structures.

  • 309.
    Barsoum, Zuheir
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Khurshid, Mansoor
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. Cargotec Sweden AB.
    Ultimate Strength Capacity of Welded Joints in High Strength Steels2017In: 2nd International Conference on Structural Integrity, ICSI 2017 / [ed] Iacoviello, F Moreira, PMGP Tavares, PJS, Elsevier, 2017, Vol. 5, p. 1401-1408Conference paper (Refereed)
    Abstract [en]

    High strength steels are nowadays used in a wide range of weight lifting applications, e.g. spreaders and cranes, where there is a demand on lightweight design of these structures with increased structural performance where the welds become more sensitive to failure. This study focuses on investigating the influence of the mismatch in the yield strength of the weld filler material and the welds penetration depth on the ultimate strength capacity and failure modes of butt and fillet welded high strength steels of yield strength in the range of 350 960 MPa. The load carrying capacities of these mentioned joints are evaluated with experiments and compared with the estimations by finite element analysis (FEA), and design rules in Eurocode 3 and American Welding Society Code AWS D1.1. Fully penetrated joint with under-matched filler material is more ductile and the ultimate strength capacity of base plate can be achieved. It is observed that joints with under-matched filler material are more sensitive to penetration ratio. This influence is more pronounced in joints in S960 steel welded with under-matched filler material. It is also found that the design rules in Eurocode3 (valid for design of welded joints in steels of grade up to S700) can be extended to designing of welds in S960 steels using correlation factor of one.

  • 310.
    Barsoum, Zuheir
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Samuelsson, Jack
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Jonsson, B.
    Björkblad, A.
    Fatigue design of lightweight welded vehicle structures: Influence of material and production procedures2012In: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture, ISSN 0954-4054, E-ISSN 2041-2975, Vol. 226, no 10, p. 1736-1744Article in journal (Refereed)
    Abstract [en]

    Structural details and components in many types of products are continuously subjected to variable amplitude loading during operation. Fatigue loading and fatigue damage is thus the most common failure mode for the mentioned equipment in operation. The influence of the material grade, weld quality and fabrication procedure have a major impact on the structural durability of welded vehicle structures. The comprehensive research work within the Nordic research and development community have contained development of finite element modelling of complex structures, including crack growth in two- and three-dimensional fatigue testing of welded small-scale specimen and full-scale components, investigations of weld defects and flaws (e.g. cold laps) and weld roots. An important part of these projects is related to simulation and measurements of formation and relaxation of residual stresses. Within these projects three new quality systems, for welded and cast components and for cut edges, have been developed based on a scientific ground and a fitness for purpose design philosophy. Volvos new weld class system, which is an open standard, is now a base for the revision of the international weld quality system ISO 5817. In this article the major findings in these research activities are briefly presented and discussed.

  • 311.
    Barsoum, Zuheir
    et al.
    KTH. Nordic Welding Engineering AB, Nansta 208, Forsa, Sweden.
    Stenberg, Thomas
    KTH. Nordic Welding Engineering AB, Nansta 208, Forsa, Sweden.
    Lindgren, E.
    Fatigue properties of cut and welded high strength steels-Quality aspects in design and production2018In: Procedia Engineering, Elsevier, 2018, Vol. 213, p. 470-476Conference paper (Refereed)
    Abstract [en]

    In this study, several aspects regarding effect of quality on the fatigue strength in welded cut HSS have been investigated and are discussed. A novel numerical algorithm has been developed which assesses the welded surface and calculates and quantifies weld quality parameters and the presence of defects which are critical in fatigue applications. The algorithm is designed for implementation in serial production. It will provide robust and reliable feedback on the quality being produced, which is essential if high strength steels are utilized and high quality welds are necessary for the structural integrity of the welded component. Two welding procedures which can increase the weld quality in as welded conditions have been assessed. It was found that by using these methods, the fatigue strength can be increased with 20% compared to normal weld quality. Furthermore, two fatigue assessment methods ability to account for increased weld quality in low cycle and high cycle fatigue applications has been studied. One of these methods showed sufficient accuracy in predicting the fatigue strength with small scatter and also account for increased weld quality. The influence of surface quality on cut edges was studied and the fatigue strength was estimated using international standards and a fatigue strength model for cut edges. It was found that the fatigue strength in testing was 15-70% higher compared to the estimation, thus proving a weak link between the international standard and fatigue strength.

  • 312.
    Basirat, Mitra
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    An Insight into the Effect of Deformation on Carbide Dissolution in the Band Structure of Bearing Steel2013In: Diffusion In Solids And Liquids VIII, Trans Tech Publications Inc., 2013, p. 171-176Conference paper (Refereed)
    Abstract [en]

    Dendritic segregation in deformed samples remains in the form of band structure, which is a high-strained region. The present work investigates the effect of the uphill diffusion process, occurring during deformation, on the dissolution of carbide particles in the band structure. A series of hot compression tests are performed on the cast structure of bearing steel by using a hydraulic testing machine, MTS 810. Cylindrical specimens are deformed in a temperature range of 800 degrees C to 900 degrees C and at strain rates of 5s(-1) and 0.5s(-1). In order to eliminate the recovery process, samples are immediately quenched after the compression. The microsegregation of Cr, Mo, Mn and Si are investigated in the band structure, which shows a tendency of uphill diffusion during deformation process. The results show that the volume fraction of carbides varies with the increased straining. The results also show that deformation causes the fragmentation, dispersion of pearlite in the dendrites and the dissolution of spheroidized carbides in the band structure.

  • 313.
    Basirat, Mitra
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Disorder Structure formation during plastic defroamtion of pure copper2012In: International journal of material science, ISSN 0973-4589, Vol. 7, no 3, p. 169-182Article in journal (Refereed)
    Abstract [en]

    The effect of the deformation process at 300˚C on the cast structure of pure copper is investigated. The temperature measurements during compression test are performed by a new experimental method developed earlier [1]. The deformed structure is studied with the aid of optical and transmission electron microscopy. Micrographs show the formation of deformed bands with high internal energy, due to many lattice defects. The strain energy calculations are based on an energy balance and the data obtain from micrograph studies performed by optical and transmission electron microscopy. It is found that there is a significant difference in the strain energy values obtained in the present work compared to the values available in the literature.  The strain energy values obtained in the band structure of the present work are 17.4% to 24% of the heat of fusion of Cu. Such high energy is sufficient to change the normal FCC structure to a disordered atomic structure in the highly deformed regions, during plastic deformation.

  • 314.
    Basirat, Mitra
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Effect of deformation on microsegregation in cast structure of bearing steel2012In: TMS 2012 141st Annual Meeting & Exhibition - Supplemental Proceedings, Vol 2: Materials Properties, Characterization, And Modeling, 2012, Vol. 2, p. 309-316Conference paper (Refereed)
    Abstract [en]

    Microsegregation changes in the cast structure of a five-ton ingot of ball bearing steel are investigated by a series of hot compression tests. Cylindrical specimens are deformed at a temperature range of 800 degrees C to 900 degrees C and strain rates of 0.5 s(-1). Samples are quenched after the compression in order to eliminate the homogenization time. Subsequently they are analysed with the aid of Electron Microprobe Analysis (EMPA) in order to investigate the effect of hot compression on microsegregation of Mo, Cr, Mn and Si. It is found that highly segregated regions are regions for formation of deformation bands. It seems that the degree of microsegregation increases by increasing the deformation. An attempt is made to estimate the diffusion coefficients of alloying elements during the deformation process. The increase of microsegregation during deformation is explained by tendency for uphill diffusion.

  • 315.
    Basirat, Mitra
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Plastic Deformation and Recrystallization in Incoloy 825Manuscript (preprint) (Other academic)
  • 316. Basu, S.
    et al.
    Lahiri, A. K.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Activity of Ferric Oxide in Steelmaking Slag2010In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, no 2, p. 414-419Article in journal (Refereed)
    Abstract [en]

    Refining reactions in steelmaking primarily involve oxidation of impurity element(s). The oxidation potential of the slag and the activity of oxygen in the metal (h(O)) are the major factors controlling these chemical reactions. In turn, the oxidation potential of the slag is influenced strongly by the equilibrium distribution of oxygen between ferrous and ferric oxides. We recently investigated the activity coefficient of FeO in steelmaking slag and the effect of chemical composition thereon. This work is focused on estimation of the activity coefficient of Fe2O3.

  • 317. Basu, S.
    et al.
    Lahiri, A. K.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Distribution of phosphorus and oxygen between liquid steel and basic oxygen steelmaking slag2008In: Proc. ICS 2008: The 4th Int. Congress Sci. Technol. Steelmaking, 2008, p. 594-597Conference paper (Refereed)
  • 318. Basu, S.
    et al.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Lahiri, A. K.
    Thermodynamics of Phosphorus and Sulphur Removal during Basic Oxygen Steelmaking2010In: STEEL RESEARCH INTERNATIONAL    , 2010, Vol. 81, no 11, p. 932-939Conference paper (Refereed)
    Abstract [en]

    Removal of impurity elements from hot metal is essential in basic oxygen steelmaking. Oxidation of phosphorus from hot metal has been studied by several authors since the early days of steelmaking. Influence of different parameters on the distribution of phosphorus, seen during the recent work of the authors, differs somewhat from that reported earlier. On the other hand, removal of sulphur during steelmaking has drawn much less attention. This may be due to the magnitude of desulphurisation in oxygen steelmaking being relatively low and desulphurisation during hot metal pre-treatment or in the ladle furnace offering better commercial viability Further, it is normally accepted that sulphur is removed to steelmaking slag in the form of sulphide only However, recent investigations have indicated that a significant amount of sulphur removed during basic oxygen steelmaking can exist in the form of sulphate in the slag under oxidising conditions. The distribution of sulphur during steelmaking becomes more important in the event of carry-over of sulphur-rich blast-furnace slag, which increases sulphur load in the BOF. The chemical nature of sulphur in this slag undergoes a gradual transition from sulphide to sulphate as the oxidative refining progresses.

  • 319.
    Basu, Somnath
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Studies on dephosphorisation during steelmaking2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This work is aimed at understanding the thermodynamic principles influencing the phosphorus partition between slag and steel during steelmaking, particularly during refining of high-phosphorus hot metal using the basic oxygen steelmaking (BOS) process. Mapping of the slag path has been carried out using a mass balance model based on input conditions and off-gas analysis, which has been validated by intermediate measurements of slag and metal composition in an industrial basic oxygen furnace (BOF). The slag composition is found to vary over a wide range of basicity (%CaO/%SiO2) and iron oxide content. The partition of phosphorus increases with progress of refining but reduces during the intermediate period, corresponding to a decrease in iron oxide concentration and formation of “dry slag”. The phosphorus partition ratio increases again towards the end of the process. The equilibrium partition ratios for such conditions have been theoretically estimated using slag “model(s)”, based on the estimated slag compositions. It is seen that the partition ratio of phosphorus remains within 45% – 60% of the equilibrium value, showing a gradual decrease with progress of the refining process.

    Equilibrium phosphorus partition ratios for slags containing low concentrations of MnO and Al2O3 have been experimentally determined, over the ranges of basicity and iron oxide concentration approximately corresponding to that observed in the typical BOS process. It is seen that the equilibrium phosphorus partition ratio is practically independent of basicity greater than 2.5 – 2.6, over the entire range of temperature and FeOx concentration studied. Variation of the activity of P2O5 with basicity and FeOx concentration has been investigated to explain the trends observed in the variation of phosphorus partition ratio. It is seen that the activity coefficient of P2O5 is lowest, and hence most conducive for removal of phosphorus from steel, over certain finite ranges of basicity and iron oxide concentration. It follows that the efficiency of dephosphorisation is likely to be maximum if the basic oxygen steelmaking process is operated within these ranges. Simultaneous with this work, mathematical correlations have been developed for estimation of P2O5 activity coefficient and phosphorus partition ratio as functions of slag composition. The correlations are compared with those proposed by earlier workers and are found to result in better predictions over certain composition ranges.

  • 320.
    Basu, Somnath
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lahiri, Ashok Kumar
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    A model for activity coefficient of P2O5 in BOF slag and phosphorus distribution between liquid steel and slag2007In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 47, no 8, p. 1236-1238Article in journal (Refereed)
  • 321.
    Basu, Somnath
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lahiri, Ashok Kumar
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Phosphorus partition between liquid steel and CaO-SiO2-FeOx-P2O5-MgO slag containing 15-25 %FeO2007In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 38, no 4, p. 623-630Article in journal (Refereed)
    Abstract [en]

    CaO-SiO2-FeO2-P2O5-MgO bearing slags are typically used in the basic oxygen steelmaking (BOS) process. The partition ratio of phosphorus between slag and steel is an index of the phosphorus holding capacity of the slag, which determines the phosphorus content achievable in the finished steel. The influence of factors such as FeO content and basicity on the phosphorus partition ratio was investigated at two different temperatures. The partition ratio initially increased with basicity but remained constant beyond a basicity of 2.5 to 2.6. An increase in the FeO content up to 18 to 20 mass pct was beneficial for the phosphorus partition at a basicity level of 2 to 3, but a higher concentration of FeO resulted in a decrease in the phosphorus partition ratio; the FeO concentration corresponding to this transition varied with basicity and temperature. At even lower basicities, however, the equilibrium phosphorus partition showed either no change, or a marginally decreasing trend, with an increase in the FeO content.

  • 322.
    Basu, Somnath
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lahiri, Ashok Kumar
    KTH.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Phosphorus partition between liquid steel and CaO-SiO2-P2O5-MgO slag containing low FeO2007In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 38, no 3, p. 357-366Article in journal (Refereed)
    Abstract [en]

    CaO-SiO2-FeOx-P2O5-MgO bearing slags are typical in the basic oxygen steelmaking (BOS) process. The partition ratio of phosphorus between slag and steel is an index of the phosphorus holding capacity of the slag, which determines the phosphorus content achievable in the finished steel. The influences of FeO concentration and basicity on the equilibrium phosphorus partition ratios were experimentally determined at temperatures of 1873 and 1923 K, for conditions of MgO saturation. The partition ratio initially increased with basicity but attained a constant value beyond basicity of 2.5. An increase in FeO concentration up to approximately 13 to 14 mass pet was beneficial for phosphorus partition.

  • 323.
    Basu, Somnath
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lahiri, Ashok Kumar
    KTH.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Halder, Jayanta
    Change in phosphorus partition during blowing in a commercial BOF2007In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 47, no 5, p. 766-768Article in journal (Refereed)
  • 324. Battley, M.
    et al.
    Allen, T.
    Schierlink, J.
    Lake, S.
    Pehrson, Petter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Hydroelastic behaviour of slam loaded composite hull panels2008In: High Perform. Yacht Des. Conf., HPYD, 2008, p. 37-46Conference paper (Refereed)
    Abstract [en]

    The effects of stiffness on hydroelastic responses of composite marine hull panels subjected to water slamming loads have been experimentally characterised. Panels included a very flexible single skin laminate, a medium stiffness sandwich panel and a very stiff sandwich panel. Panels were tested at a deadrise angle of 10° for a range of water impact velocities from 0.5 to 7m/s in a Servo-hydraulic Slam Testing System. Results demonstrate that the panel stiffness has a significant effect on the responses of slam loaded composite panels. Flexible panels had reductions in the local velocity at the centre of the panel relative to the water, reducing peak pressures at the panel centre. Pressures increased near to the chine edge of the panel, possibly due to reductions in the local deadrise angle due to panel deformation. Such effects were particularly noticeable when the loading rate was of similar order to the first natural frequency of the panel. The implications of the effects of panel stiffness on effective pressure and panel structural response on composite structural design are discussed.

  • 325. Battley, Mark
    et al.
    Burman, Magnus
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Characterization of Ductile Core Materials2010In: Journal of Sandwich Structures and Materials, ISSN 1099-6362, E-ISSN 1530-7972, Vol. 12, no 2, p. 237-252Article in journal (Refereed)
    Abstract [en]

    This article describes an experimental investigation of characterization methods for ductile core materials. Full-field optical strain measurement methods are used to determine the strain distributions in standard testing methods such as block shear and four-point beam testing, particularly for highly ductile cores subjected to large deformations. The results show that the stress and strain fields in both block shear and sandwich beam tests are very different to those assumed by the testing standards. The test methods result in complex post yield states of stress in the core materials, meaning the core shear strength and ultimate shear strain should not be calculated by classical methods in the post yield region.

  • 326.
    Bayard, Ove
    KTH, Superseded Departments, Production Engineering. KTH, Superseded Departments, Materials Processing.
    Investigation of the verification techniques for modelling turning processes2000Licentiate thesis, monograph (Other scientific)
  • 327. Bayazit, Mehmet
    et al.
    Das, Prabir Kumar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Tasdemir, Yuksel y
    Moisture susceptibility of warm mix asphalt2014In: Indian journal of engineering & materials sciences, ISSN 0971-4588, E-ISSN 0975-1017, Vol. 21, no 6, p. 683-691Article in journal (Refereed)
    Abstract [en]

    In this study, moisture susceptibility characteristics of wax modified bitumens and warm mix asphalt (WMA) mixtures are determined. The asphalt mixtures are prepared with 50170 penetration grade unmodified bitumen and modified bitumens with three different types of additives (Fischer Tropsch wax, montan wax and polyethylene wax) by weight of 6%. The moisture susceptibility characteristic of the four bitumens is determined with Sessile drop method and that for asphalt mixtures is determined with Nicholson stripping test on loose asphalt mixtures and Modified Lottman test on compacted asphalt mixtures. Furthermore, Marshall stability with different blow numbers of WMA mixtures are determined. The findings from all of these tests suggest that due to the Fischer Tropsch wax and montan wax modification the asphalt mixture become more moisture susceptible which correlates with the surface energy characterization. Interestingly, polyethylene wax modification shows positive moisture performance.

  • 328. Baykal, A.
    et al.
    Deligöz, H.
    Sozeri, H.
    Durmus, Z.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Triethylene Glycol Stabilized CoFe2O4 Nanoparticles2012In: Journal of Superconductivity and Novel Magnetism, ISSN 1557-1939, Vol. 25, no 6, p. 1879-1892Article in journal (Refereed)
    Abstract [en]

    We report on the synthesis and detailed composition, thermal, micro-structural, ac-dc conductivity performance and dielectric permittivity characterization of triethylene glycol (TREG) stabilized CoFe 2O 4 nanoparticles synthesized by polyol method. XRD analysis confirmed the inorganic phase as CoFe 2O 4 with high phase purity. Microstructure analysis with TEM revealed well separated, spherical nanoparticles in the order of 6 nm, which is also confirmed by X-ray line profile fitting. FT-IR analysis confirms that TREG is successfully coated on the surface of nanoparticles. Overall conductivity of nanocomposite is approximately two magnitudes lower than that of TREG with increase in temperature. The ac conductivity showed a temperature dependent behavior at low frequencies and temperature independent behavior at high frequencies which is an indication of ionic conductivity. The dc conductivity of the nanocomposites and pure TREG are found to obey the Ar- rhenius plot with dc activation energies of 0.258 eV and 0.132 eV, respectively. Analysis of dielectric permittivity functions suggests that ionic and polymer segmental motions are strongly coupled in the nanocomposite. TREG stabilized CoFe 2O 4 nanoparticles has lower ε and ε than that of pure TREG due to the doping of cobalt. As the temperature increases, the frequency at which (ε ) reaches a maximum shifted towards higher frequencies. On the other hand, the activation energy of TREG for relaxation process was found to be 0.952 eV which indicates the predominance of electronic conduction due to the chemical nature of TREG. Contrarily, no maximum peak of tan Ύ was observed for the nanocomposite due to the being out of temperature and frequency range applied in the study.

  • 329.
    Baykal, Berkan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    A Methodology Study of the Evolution of the Secondary Brassmaking Process when Adding of Non-metallic Inclusions2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Previously most of the research focusing on non-metallic inclusions additions have focused on Fealloys. The presence of inclusions has a great effect on the material properties of Fe-alloy. Brass (Cu-Zn) is a germicidal material which has been widely used for especially drinking water applications. However, the influence of non-metallic inclusions on the material properties in brass have only been studied to a limited degree by other researchers.

    The secondary brass-making process is not a common process compared to the secondary steelmaking process. The process of secondary metal making (re-melting) has several purposes such as to improve the cleanliness, deoxidation, microstructure, composition etc. The secondary brass making process is performed to improve mechanical and chemical properties of brass.

    The present work presents a precursory methodology research on the influence of the non-metallic inclusions on liquid Cu-alloys for the brass grade (CuZn38). The vague effect of the secondary brass-making technic for CuZn38 eco-brass research is estimated based on thermodynamic considerations.

    During a secondary brass-making process, the effects of the primary addition of the raw Al2O3 powder formation in molten brass has been studied by using a by specific quartz tube suction technique. The present work studied influence of the addition of raw Al2O3 powder in brass based on quartz tube samples and ingot samples.

    The used Al2O3 inclusions and deoxidizer in brass show that a similar characterization can be found as when secondary Al2O3 inclusions are present in steel-making. The results showed that the Al2O3 particles in brass had different morphologies. Specifically, Al2O3 reacts with ZnO under the formation of ZnAl2O4

  • 330.
    Baykov, Vitaly
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Point defect interactions and structural stability of compounds2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Theoretical studies of point defect interactions and structural stability of compounds have been performed using density functional theory. The defect-related properties, such as activation energy of diffusion, electronic and magnetic structure of selected materials have been studied.

    The major part of the present work is devoted to a very important material for semiconductor industry, GaAs. The formation energies of intrinsic point defects and the solution energies of 3d transitions in GaAs have been calculated from first principles. Based on the calculated energies, we analysed the site preference of defects in the crystal. The tendency of defects to form clusters has been investigated for the intrinsic defects as well as for impurities in GaAs. The magnetic moment of 3d impurities has been calculated as a function of the chemical environment. The possibility of increasing the Curie temperature in (Ga,Mn)As by co-doping it with Cr impurities has been examined on the basis of calculated total energy difference between the disordered local moment and the ferromagnetically ordered spin configurations. We found that, in order to reach the highest critical temperature, GaAs should be separately doped with either Cr or Mn impurities. Also, we have shown that diffusion barrier of interstitial Mn depends on the charge state of this impurity in (Ga, Mn)As. The formation of defect complexes between interstitial and substitutional Mn atoms, and their influence on the value of diffusion barrier for interstitial Mn, has been studied.

    The pair interactions energies between interstitial oxygen atoms in hcp Zr, Hf and Ti have been calculated using first principles. Based on the calculated energies, the oxygen ordering structures in IVB transition metal solid solutions have been explained. A prediction of nitrogen ordering in Hf-N solid solution has been made.

    The thermodynamic description of intermetallic compounds in the Zr-Sn binary system has been obtained. The conclusion has been made that Zr substitution on the Sn sites takes place in the Zr4Sn phase, which accounts for the unusual stoichiometry of this Cr3Si structure type compound.

    The influence of pressure on the phase stability in the Fe-Si system has been investigated. We have found instability of the hcp Fe0.9Si0.1 random alloy with respect to the decomposition onto the Si-poor hcp Fe alloy and the B2 FeSi under high pressure. The tendency of this decomposition becomes stronger with increasing the applied pressure.

  • 331.
    Baykov, Vitaly
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Isaev, P. A.
    Moscow State Institute of Steel and Alloys.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Vekilov, Y. K.
    Moscow State Institute of Steel and Alloys.
    Abrikosov, I. A.
    Linköping University.
    Ab Initio Studies of the Energy Characteristics and Magnetic Properties of Point Defects in GaAs2005In: Physics of the solid state, ISSN 1063-7834, E-ISSN 1090-6460, Vol. 47, no 10, p. 1831-1836Article in journal (Refereed)
    Abstract [en]

    The formation energies of intrinsic point defects and solution energies of transition metal impurities in gallium arsenide are determined on the basis of ab initio calculations using the method of a locally self-consistent Green's function, which is a generalization of the coherent potential approximation. Based on the calculated energies, the conclusion is made that the As-Ga antisite defect is the most common intrinsic defect in GaAs. Calculations showed that transition metal impurities, except for Ni, preferentially occupy gallium sites substitutionally. The magnetic moments of impurity atoms are calculated as a function of the chemical environment. It is shown that, in compensated GaAs, Mn atoms tend to form clusters.

  • 332.
    Baykov, Vitaly
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jerlerud Perez, Rosa
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sundman, Bo
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Structural stability of intermetallic phases in the Zr-Sn system2006In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 55, no 5, p. 485-488Article in journal (Refereed)
    Abstract [en]

    A thermodynamic description of the intermetallic compounds in the Zr-Sn binary system has been obtained using total energy calculations by means of the Vienna ab initio simulation package. Our calculations show that hexagonal compounds Zr5Sn4 and Zr5Sn3 are the most stable phases in the Zr-Sn binary system. Their high stability is found to be due to hybridization of the Sn 5p with Zr 4d electronic states. Based on the calculated energies, the conclusion is made that Zr substitution on the Sri sites takes place in the Zr4Sn phase, which accounts for the unusual stoichiometry of this Cr3Si structure type compound.

  • 333.
    Baykov, Vitaly
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Smirnova, E. A.
    Department of Theoretical Physics of Steel and Alloys, Moscow.
    Abrikosov, I. A.
    Department of Physics and Measurement Technology, Linköping University.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Magnetic properties of 3d impurities in GaAs2007In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 310, no 2, p. 2120-2122Article in journal (Refereed)
    Abstract [en]

    Electronic structure, thermodynamic, and magnetic properties of 3d-transition metal (TM) impurities in GaAs have been studied from first principles using Green's function approach. The studied TM impurities (V, Cr, Mn, and Fe) are found to form substitutional alloys on the Ga sublattice. The possibility of raising the Curie temperature TC in (GaMn) As by co-doping it with Cr impurities was examined on the basis of total energy difference between the disordered local moment (DLM) and the ferromagnetically ordered (FM) spin configurations. The calculated Curie temperature and magnetic moment have maxima for GaAs doped with Cr and Mn. The magnetic properties of Mn-doped GaAs are shown to be more sensitive to antisite As defects than those of Cr-doped GaAs. However, the Cr impurities are sensitive to the presence of acceptor defects, such as vacancies on the Ga sublattice. The investigation of the electronic structure of pseudo-ternary alloys (Ga(1-x-y)MnxCry) As has shown a mutual compensation of Mn and Cr impurities. Therefore, in order to reach the highest critical temperature, GaAs has to be separately doped with Cr or Mn impurities. The GaAs doped with Fe is found to be non-ferromagnetic.

  • 334.
    Beaussant Törne, Karin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Investigation of corrosion properties of metals for degradable implant applications2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Degradable metallic implants are a new class of biomaterials with potentialto replace permanent materials in temporary applications to reduce therisk of long term adverse effects.This thesis focuses on in vitro testing of zinc and magnesium based metals.As new degradable metals are developed screening of new materials within vitro test methods is an attractive option to avoid unnecessary, time consumingand expensive animal studies. The influence of factors such as ioniccomposition of the test solution, buffer system, strain and alloy compositionwas investigated. By employing electrochemical in situ techniques such asimpedance spectroscopy it is possible to study the metal-solution interfaceand determine the properties of the corroding surface. Ex situ surface characterizationtechniques such as scanning electron microscopy and infraredspectroscopy were then used to complement the results of the electrochemicalmeasurements.The importance of appropriate selection of the test solution is highlightedin this work. Zinc was found to corrode in Ringer’s solution by a mechanismcloser to in vivo corrosion than in a phosphate buffered saline solution(PBS).Ringer’s solution is therefore the more appropriate test environment for longterm evaluation of zinc based metals.When evaluating the corrosion of Zn-Mg and Zn-Ag alloys in Ringer’ssolution selective dissolution was found to occur for both types of alloys. Localprecipitation and formation of a porous, less protective, layer of corrosionproducts was found for Zn-Mg alloys. The selective dissolution of Zn-Agalloy caused an enrichment of AgZn3 on the surface which may affect thebiocompatibility of the alloy.The use of HEPES to maintain the pH of the test solution increasedthe corrosion rate of magnesium due to formation of a less protective layerof corrosion products. Magnesium corrosion should therefore preferably bestudied in solutions where the pH is maintained by the biological buffer systemCO2/H2CO3.In addition to saline solutions human whole blood and plasma were evaluatedas more clinically relevant in vitro environments. They were found toproduce reproducible results and to be suitable for short term experiments.Formation of a corrosion product layer comprised of both organic and inorganicmaterial was detected on zinc in both plasma and whole blood.During anodic polarization the adsorption of organic species on the zincsurface was found to increase the surface coverage of Zn ions in whole blood.The increased surface coverage then allowed for precipitation of a protectivelayer of Zn5(PO4)3 and a subsequent decrease in corrosion rate at higherpotentials.When subjecting zinc samples to strain the organic/inorganic corrosionproduct formed in whole blood was observed by impedance spectroscopy toprevent micro cracking and premature failure.The cracking of magnesium alloy samples under applied strain was alsocharacterized by impedance. Changes in surface properties due to crack initiation

  • 335.
    Beaussant Törne, Karin Beaussant
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics. Abbott, St Paul, MN USA.
    Khan, Fareed Ashraf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ornberg, Andreas
    Weissenrieder, Jonas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Zn-Mg and Zn-Ag degradation mechanism under biologically relevant conditions2018In: Surface Innovations, ISSN 2050-6252, E-ISSN 2050-6260, Vol. 6, no 1-2, p. 81-92Article in journal (Refereed)
    Abstract [en]

    Zinc (Zn) alloys form a promising new class of biodegradable metals that combine suitable mechanical properties with the favorable degradation properties of pure zinc. However, the current understanding of the influence of alloying elements on the corrosion of zinc alloys, in biologically relevant media, is limited. The authors studied the degradation of three alloys, zinc-4 wt% silver (Ag), zinc-0.5 wt% magnesium (Mg) and zinc-3 wt% magnesium by in situ electrochemical impedance spectroscopy (EIS). After exposure for 1 h or 30 d, the samples were characterized by infrared spectroscopy and scanning electron microscopy. The presence of secondary phases in the alloy microstructure induced selective corrosion and increased the degradation rate. EIS analysis revealed an increase in surface inhomogeneity already at short (hours) immersion times. The microgalvanic corrosion of the zinc-silver alloy resulted in enrichment of the AgZn3 phase at the sample surface. The enrichment of silver and potential release of AgZn3 particles may result in complications during the tissue regeneration. The zinc-magnesium alloy surface was depleted of the magnesium-rich phase after 8-12 d. The selective dissolution caused local precipitation of corrosion products and a thicker corrosion layer with larger pore size consistent with increased corrosion rate.

  • 336.
    Becerra Garcia, Marley
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Saba, M. M. F.
    Liu, Lige
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Visacro, S.
    Using low-level currents measured during lightning events to estimate upward leader properties2018In: 34th International Conference on Lightning Protection, ICLP 2018, Institute of Electrical and Electronics Engineers Inc. , 2018Conference paper (Refereed)
    Abstract [en]

    Low-level currents measured prior to return strokes can potentially provide information about the properties of upward leaders during lightning flashes. However, these currents need to be properly analysed and interpreted in order to be useful for evaluating upward connecting leaders. In this paper, low-level currents measured before return strokes in two lightning events to two structures in Brazil are analysed and interpreted as case studies. The discharge current estimated from one of these events is used as input to a detailed thermohydrodynamic model with an extensive kinetic scheme for N2/O2 mixtures. The model allows the evaluation of the physical and chemical properties of upward connecting leaders. Estimates of the temperature, mass density, electric field and radius of the channel are presented for an upward connecting leader propagating in a lightning event. In addition, estimates of the axial density of electrons, ions and neutral particles (including NO and NO2) are also reported.

  • 337.
    Becerra, Marley
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Friberg, Andreas
    ABB Corporate Research, Västerås.
    Arc jets blown by outgassing polymers in air2014In: Proceedings of the 20th International Conference on Gas Discharges and Their Applications GD2014, GD2014 , 2014, p. 1-4Conference paper (Refereed)
    Abstract [en]

    This paper describes experimental results about the behaviour of arc jets transversely blown in the presence of outgassing polymers (POM –CH2O– or PMMA –C5H8O2–). The arc jets are ignited in air between copper electrodes under a 2 kA, 50 Hz AC current. High speed photography and optical emission spectroscopy are used to study the mechanism leading to the increase of the arc voltage when polymers are used instead of non-ablating materials (e.g. quartz). It is found that the transversal blowing flow caused by the injection of ablation vapours have a weak effect on the arc voltage build-up. Instead, the chemical changes in the plasma environment appear to better explain the observed increase in the arc voltage when polymers are used. 

  • 338.
    Bechta, Sevostian
    et al.
    A.P. Alexandrov Research Institute of Technology (NITI).
    Krushinov, E.V.
    A.P. Aleksandrov Research Institute of Technology.
    Almjashev, V.I.
    Institute of Silicate Chemistry of Russian Academy of Sciences.
    Vitol, S.A
    A.P. Aleksandrov Research Institute of Technology.
    Mezentseva, L.P.
    Institute of Silicate Chemistry of Russian Academy of Sciences.
    Petrov, Yu.B.
    Saint-Petersburg Electrotechnical University ‘LETI’.
    Lopukh, D.B.
    Saint-Petersburg Electrotechnical University ‘LETI’.
    Khabensky, V.B.
    A.P. Aleksandrov Research Institute of Technology.
    Barrachin, M.
    Institut de Radioprotection et Suˆrete´ Nucle´aire (IRSN).
    Hellmann, S.
    Framatome ANP GmbH.
    Froment, K.
    Laboratoire de Physico-chimie et Thermohydraulique Multiphasiques (LPTM), CEA/Grenoble, DTN/SE2T/LPTM – 17 rue des Martyrs.
    Fischer, M.
    Framatome ANP GmbH.
    Tromm, W.
    FZK, IKET, Karlsruhe, Forschungszentrum Karlsruhe GmbH.
    Bottomley, D.
    European Commission – DG – Joint Research Centre, Institute for Transuranium Elements.
    Defoort, F.
    Laboratoire de Physico-chimie et Thermohydraulique Multiphasiques (LPTM), CEA/Grenoble, DTN/SE2T/LPTM – 17 rue des Martyrs.
    Gusarov, V.V.
    Institute of Silicate Chemistry of Russian Academy of Sciences.
    Phase diagram of the UO2-FeO1+x system2007In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 362, no 1, p. 46-52Article in journal (Refereed)
    Abstract [en]

    Phase-relation studies of the UO2–FeO1+x system in an inert atmosphere are presented. The eutectic point has beendetermined, which corresponds to a temperature of (1335 ± 5) C and a UO2 concentration of (4.0 ± 0.1) mol.%. Themaximum solubility of FeO in UO2 at the eutectic temperature has been estimated as (17.0 ± 1.0) mol.%. Liquidus temperaturesfor a wide concentration range have been determined and a phase diagram of the system has been constructed.

  • 339.
    Bechta, Sevostian
    et al.
    A.P. Alexandrov Research Institute of Technology (NITI).
    Krushinov, E.V.
    A.P. Aleksandrov Research Institute of Technology.
    Almjashev, V.I.
    Institute of Silicate Chemistry of Russian Academy of Sciences.
    Vitol, S.A
    A.P. Aleksandrov Research Institute of Technology.
    Mezentseva, L.P.
    Institute of Silicate Chemistry of Russian Academy of Sciences.
    Petrov, Yu.B.
    Saint-Petersburg Electrotechnical University ‘LETI’.
    Lopukh, D.B.
    Saint-Petersburg Electrotechnical University ‘LETI’.
    Khabensky, V.B.
    A.P. Aleksandrov Research Institute of Technology.
    Barrachin, M.
    Institut de Radioprotection et Suˆrete´ Nucle´aire (IRSN).
    Hellmann, S.
    Framatome ANP GmbH.
    Froment, K.
    Laboratoire de Physico-chimie et Thermohydraulique Multiphasiques (LPTM), CEA/Grenoble, DTN/SE2T/LPTM – 17 rue des Martyrs.
    Fischer, M.
    Framatome ANP GmbH.
    Tromm, W.
    FZK, IKET, Karlsruhe, Forschungszentrum Karlsruhe GmbH.
    Bottomley, D.
    European Commission – DG – Joint Research Centre, Institute for Transuranium Elements.
    Defoort, F.
    Laboratoire de Physico-chimie et Thermohydraulique Multiphasiques (LPTM), CEA/Grenoble, DTN/SE2T/LPTM – 17 rue des Martyrs.
    Gusarov, V.V.
    Institute of Silicate Chemistry of Russian Academy of Sciences.
    Phase diagram of the ZrO2-FeO system2006In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 348, no 1-2, p. 114-121Article in journal (Refereed)
    Abstract [en]

    The results on the ZrO2–FeO system studies in a neutral atmosphere are presented. The refined eutectic point has beenfound to correspond to a ZrO2 concentration of 10.3 ± 0.6 mol% at 1332 ± 5 C. The ultimate solubility of iron oxide inzirconia has been determined in a broad temperature range, taking into account the ZrO2 polymorphism. A phase diagramof the pseudobinary system in question has been constructed.

  • 340.
    Beheshti, Reza
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Akhtar, Shahid
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Heat treatment of black dross for the production of a value added material - a preliminary study2012In: EPD Congress 2012, John Wiley & Sons, 2012, p. 353-360Conference paper (Refereed)
    Abstract [en]

    The potential use of Black Dross (BD) as a raw material for the production of refractories, fluxing agents and glasses is the main motivation of the present study. Heat treatment experiments were carried out in Ar, and under reduced pressure (20 Pa), to evaluate the salt removal efficiency. The chemical composition of the BD after heat treatment was investigated by SEM-EDS and XRD analyses. Based on the present results, it is established that the salt starts to evaporate at ≈1273 K in Ar, and under reduced pressure. The salt removal efficiency in a 20 g sample was found to increase in both cases as a function of time and temperature. Moreover, in Ar the chlorine concentration was lowered to 0.3 wt% after heat treatment at 1523 K for 10 hours. Under reduced pressure, however, 0.2 wt% residual chlorine was obtained after 8 hours at 1473 K.

  • 341.
    Beheshti, Reza
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Aune, R. E.
    Automotive Lithium-ion battery recycling: A theoretical evaluation2016In: TMS Annual Meeting, The Minerals, Metals, and Materials Society, 2016, no CONFCODENUMBER, p. 65-71Conference paper (Refereed)
    Abstract [en]

    Lithium-ion Batteries (LiBs) are today used in significant quantities in the automotive industry. As these batteries are expected to last the lifetime of the vehicle, they will not be ending their useful lives in large numbers for another 10-15 years. An opportunity does therefore exist to prepare for some of the roadblocks that might arise during the development of technologies for environmentally sound recycling of LiBs. In view of this, there is a need for reliable thermodynamic and kinetic data so that a secondary product of high enough metal value, as well as quality, can be produced making it possible to find a market for its purpose. In the present study the equilibrium conditions for obtaining the best conditions possible for recovering the metal content through the aluminum recycling process were studied. All thermodynamic calculations were performed using the FactSage™ software, and the chosen chemical compositions represent the two main families of IiBs, i.e. LiNiCOAlO2 and LiFePO4 The possible production of PH3 and P4 (white phosphor) during the recycling process is also briefly discussed.

  • 342.
    Beheshti, Reza
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Moosberg-Bustnes, J.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Modeling and simulation of isothermal reduction of a single hematite pellet in gas mixtures of H2 and CO2014In: TMS 2014 143rd Annual Meeting & Exhibition, Annual Meeting Supplemental Proceedings, The Minerals, Metals, and Materials Society, 2014, p. 495-502Conference paper (Refereed)
    Abstract [en]

    In the present project a time dependent computerized model that fairly accurately simulates the isothermal reduction of a hematite pellet with the use of CO and H2 gas mixtures have been developed. The model, which is based on the Shrinking Core Model (SCM), allows for the description of the chemical reactions taking place and the mass transfer conditions existing for each of the gas species present within the pellet. The equations used to describe the different steps are numerically solved with 1D axial symmetric Finite Element Modeling (FEM) using the commercial COMSOL 4.3b software. Small-scale laboratory experiments were also performed under well-controlled conditions to get an understanding for the weight loss of the pellets as a function of time. The results obtained from these experiments were incorporated into the model. The developed model clearly shows some deviations from the experimental results, but this is believed to be due to the existing variations in the shape and size of the pellets, the porosity distribution and the pelletizing history of the industrial pellets.

  • 343.
    Beheshti, Reza
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Nothern Research Institute Narvik, Norway.
    Moosberg-Bustnes, J.
    Kennedy, M. W.
    Aune, R. E.
    Reduction of commercial hematite pellet in isothermal fixed bed-experiments and numerical modelling2016In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 43, no 1, p. 31-38Article in journal (Refereed)
    Abstract [en]

    In the present work, fixed bed reduction experiments were conducted at 1173 K over a range of H-2/CO ratios from 0.8 to 2.0 and subsequently modelled numerically (R). The model consists of two one-dimensional, isothermal and time dependent models. The gas-solid reactions were kinetically modelled using a modified shrinking core approach, and the equations were solved using the commercial software COMSOL Multiphysics H. The simulation results agree with thermal gravity experimental data with an average difference of 2.5%. A sensitivity analysis was conducted using the numerical model to establish the optimum operational conditions. The effects of the reducing gas ratio and flow rate, pellet radius and porosity, and the total bed height on the overall degree of reduction were also investigated.

  • 344.
    Beheshti, Reza
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Northern Research Institute, Norway.
    Moosberg-Bustnes, John
    Akhtar, Shahid
    Aune, Ragnhild E.
    Black Dross: Processing Salt Removal from Black Dross by Thermal Treatment2014In: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 66, no 11, p. 2243-2252Article in journal (Refereed)
    Abstract [en]

    The salt removal from black dross by thermal treatment has experimentally been studied under different conditions in both a stationary resistance furnace and in a laboratory scale rotary furnace. The experiments were designed based on partial pressure calculations using the Thermo-Calc software (Thermo-Calc Software, Stockholm, Sweden). The salt removal efficiency was evaluated by scanning electron microscope (SEM) energy-dispersive x-ray spectroscopy and x-ray diffraction analyses, and the optimum conditions for treatment established, i.e., temperature, gas flow rate, holding time, rotation rate, and sample size. The overall degree of chloride removal was established to increase as a function of time and temperature, as well as by reduced pressure. Under atmospheric pressure, the highest degree of chloride removal from a 20 g sample was obtained after 10 h at 1523 K resulting in a 98% removal and a final chloride content of 0.3 wt.% in the residue. Under reduced pressure, the chloride concentrate was lowered to 0.2 wt.% after thermal treatment of a 20 g sample at 1473 K for 8 h. In the case of 200 g samples treated in a rotary furnace, the chloride concentrate was 2.5 wt.% after 14 h at 1523 K, representing a removal of 87%. Below 0.3 wt.% chloride content, the material is deemed a nonhazardous waste.

  • 345.
    Beheshti, Reza
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Moosberg-Bustnes, John
    Akhtar, Shahid
    Aune, Ragnhild.E.
    Black Dross Processing: Utilization of Black Dross in the Production of a Ladle Fluxing Agent2017In: Journal of Sustainable Metallurgy, ISSN 2199-3831, Vol. 3, no 2, p. 265-273Article in journal (Refereed)
    Abstract [en]

    In the present study, black dross (BD) residue, a hazardous by-product generated during secondary aluminum production, has been evaluated as a possible raw material for the production of a calcium aluminate-based ladle fluxing agent to be used in the steel industry. The thermally treated BD [pretreated black dross (PBD)] used as a starting material, consisted of approximately 49.5 ± 3.5 wt% alumina and 0.3 wt% chloride. The effects of different process parameters on the properties of the produced flux were experimentally investigated, i.e., the CaO/Al2O3 ratio, the sintering temperature and time, and the cooling medium. The prepared samples were all sintered in a rapid high-temperature inductive furnace, and later characterized by SEM–EDS, XRD, XRF, and DTA/TG analyses. Dissolution tests were also performed using a synthetic slag simulating the carryover. Based on the presently obtained results, it can be concluded that the utilization of PBD as the alumina source during the production of a calcium aluminate fluxing agent shows promising results, and the optimum process conditions were established to be 1523 K for 15 min as the sintering temperature and time, water as the cooling medium, and a CaO/Al2O3 ratio of 0.94. Utilizing PBD as a raw material in the production of a value-added product would significantly reduce the need for the disposal of BD as a waste, and thereby help to decrease the overall environmental impact. It would also provide economic benefit to both the steel and aluminum industry.

  • 346.
    Beheshti, Reza
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Northern Research Institute Narvik, Norway.
    Moosberg-Bustnes, John
    Kennedy, Mark W.
    Aune, Ragnhild E.
    Reduction kinetics of commercial haematite pellet in a fixed bed at 1123-1273 K2016In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 43, no 5, p. 394-402Article in journal (Refereed)
    Abstract [en]

    In the present study a model for future use in the modelling of moving bed direct reduction reactors has been developed. The model of a fixed bed reactor for the production of sponge iron from haematite incorporates both heat-and mass-transfer, as well as the chemical reduction rate. The model results were compared to the experimental data obtained from a lab scale reactor in the temperature range 1123-1273 K, as well as to the output from a simple model assuming isothermal conditions. The H-2/CO ratio (beta) of the reducing gas was in all cases varied from 0.8 to 2.0. Overall the non-isothermal model developed permits a more accurate representation of the experimental data than the isothermal estimates, with a typical discrepancy of only 1.3%.

  • 347.
    Bekele, Abiy
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Rydén, Nils
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Gudmarsson, Anders
    Peab Asfalt AB, Drivhjulsvagen 11, S-12630 Hagersten, Sweden..
    Birgisson, Bjorn
    Texas A&M Univ, Dept Civil Engn, College Stn, TX 77843 USA..
    Automated Non-contact Resonance Excitation Method to Assess Low Temperature Dynamic Modulus of Asphalt Concrete2019In: Journal of nondestructive evaluation, ISSN 0195-9298, E-ISSN 1573-4862, Vol. 38, no 2, article id 43Article in journal (Refereed)
    Abstract [en]

    This paper studies the applicability of an automated non-destructive testing method to monitor the stiffness of asphalt concrete at low temperatures. A loudspeaker is used as a source of non-contact excitation of the axially symmetric fundamental resonant frequencies of a disc-shaped asphalt concrete specimen positioned inside an environmental chamber. Measured resonant frequencies are used to calculate the dynamic moduli of the specimen at different temperatures. The repeatability of the method as well as the effect of loudspeaker height above the sample are studied. Results show that the main advantage of the non-contact excitation method, compared to manually applied impact hammer excitation, is that repeatable automated measurements can be performed while the specimen is placed inside an environmental temperature chamber. This methodology enables to study the effect of only low temperature conditioning on the dynamic modulus of asphalt concrete without interference from mechanical loading.

  • 348.
    Bellani, Gabriele
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Lundell, Fredrik
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Söderberg, L. Daniel
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Experimental study of the forming process: Fluid velocity and fluid-fiber interaction measurements2008Conference paper (Refereed)
    Abstract [en]

    A study of the flow in the direct vicinity of a forming wire and a fiber network during forming is reported. The measurements are performed with Particle Image Velocimetry in a scaled system. Index-of-refraction matching is used to gain optical access to the flow. Time resolved measurements of the flow velocity in the vertical and horizontal direction is obtained in a plane with a size of 60 × 40 fiber diameters. The spatial resolution is 2 fiber diameters. Data is obtained for three drainage velocities and two different lengths of the fibers. The relative level of the velocity fluctuations are found to decrease with drainage velocity and is higher in the flow above a network mat of shorter fibers compared to the network made of longer fibers. The size of the flow structures is obtained by spectral analysis and compared for the six cases.

  • 349.
    Belonoshko, Anatoly
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Davis, Sergio
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Rosengren, Anders
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Ahuja, Rajeev
    Department of Physics, Uppsala University.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Simak, Sergei
    Burakovsky, Leonid
    Preston, D. L.
    Xenon melting: Density functional theory versus diamond anvil cell experiments2006In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 74, p. 054114-Article in journal (Refereed)
    Abstract [en]

    We performed two-phase ab initio density functional theory based molecular dynamics simulations of Xe melting and demonstrated that, contrary to claims in the recent literature, the pressure dependence of the Xe melting curve is consistent with the corresponding-states theory as well as with the melting curve obtained earlier from classical molecular dynamics with a Xe pair potential. While at low pressure the calculated melting curve is in perfect agreement with reliable experiments, our calculated melting temperatures at higher pressures are inconsistent with those from the most recent diamond anvil cell experiment. We discuss a possible explanation for this inconsistency.

  • 350.
    Belonoshko, Anatoly
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Davis, Sergio
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Skorodumova, Natalia
    Department of Physics, Uppsala University.
    Lundow, Per-Håkan
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Rosengren, Anders
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Properties of the fcc Lennard-Jones crystal model at the limit of superheating2007In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 76, p. 064121-Article in journal (Refereed)
    Abstract [en]

    The face-centered-cubic (fcc) Lennard-Jones (LJ) model can be considered as a representative model of a simple solid. We investigate the mechanism of melting at the limit of superheating in the fcc LJ solid by means of the procedure recently developed by us [Phys. Rev. B 73, 012201 (2006)]. Insight into the mechanism of melting was gained by studying diffusion and defects in the fcc LJ solid by means of molecular dynamics simulations. We found that the limit of superheating achieved by us is likely to be the highest so far. We also found that the size of the cluster which ignites the melting is very small (down to five to six atoms, depending on the size of the supercell) and closely correlates with the linear size of a supercell when the number of atoms varies between 500 and 13 500.

45678910 301 - 350 of 5250
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf