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  • 1.
    Akhtar, Shahid
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Shaikh, Md. Robiul Haque
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Micro Porosity Development in Directionally Solidified A356 Castings Doped with Anodized Plates and Sintered Aluminium2011Ingår i: European Congress and Exhibition on Advanced Materials and Processes (EUROMAT) 2011, Symposium C52: Processing and characterizing techniques, 2011Konferensbidrag (Refereegranskat)
  • 2. Akselsen, O. M.
    et al.
    Aune, Ragnhild E.
    Fostervoll, H.
    Harsvoer, A. S.
    Dry hyperbaric welding of subsea pipelines2006Ingår i: Welding Journal, ISSN 0043-2296, Vol. 85, nr 6, s. 52-55Artikel i tidskrift (Refereegranskat)
  • 3. Akselsen, O. M.
    et al.
    Harsvaer, A.
    Fostervoll, H.
    Aune, Ragnhild E.
    Root bead profiles in hyperbaric GTAW of X70 pipeline2006Ingår i: International Journal of Offshore and Polar Engineering, ISSN 1053-5381, Vol. 16, nr 2, s. 123-127Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This investigation began with the goal of studying the root bead penetration profiles in hyperbaric GTAW welding of X70 pipelines. Such profiles may vary substantially depending on the wire and base metal chemical composition. Root beads were deposited with a pressure corresponding to 75-m seawater depth, and with a systematic increase of 10 A in the pulse current until burnthrough took place. The results obtained showed that the penetration profiles were different between the 2 wires included in the welding program. The largest penetration width was found for wire B with the highest sulphur content (0.013% S), with a maximum width of about 8-mm width on the pipe inside for 160 A. At pulse current levels of 120 to 170 A, the difference between the 2 wires was about 1 mm. With current beyond 180 A, the profiles approached similar values, followed by burnthroughs for both wires at 190 A. However, the welding parameters were already too hot at 180 A. These results are probably caused by a Marangoni convection in the weld pool. A high content of surface active elements (e.g., sulphur) is known to shift the How pattern, providing deeper penetration. In practice, small variations in the bead penetration profile may have large consequences during offshore tie-in welding. Cost-increasing repair operations may be required if nondestructive inspection later reveals poor root bead quality. Such actions require mobilisation of huge resources.

  • 4. Akselsen, Odd M.
    et al.
    Aune, Ragnhild E.
    Olden, Vigdis
    Rorvik, Gisle
    Effects of phase transformations on residual stresses in welding of stainless steels2007Ingår i: International Journal of Offshore and Polar Engineering, ISSN 1053-5381, Vol. 17, nr 2, s. 145-151Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this investigation, we investigate the effects of solid state phase transformation on residual stresses in welding super-martensitic stainless steels, using the Satoh experimental test approach. The results obtained clearly demonstrate that the austenite-to-martensite phase transformation has remarkable effects on the final tensile residual stress level, and stresses as low as 70 to 170 MPa were found, depending on the weld thermal program. These results may imply that unnecessary conservatism is often used when assuming residual stresses to be of the same order as the base metal yield strength.

  • 5. Akselsen, Odd M.
    et al.
    Fostervoll, Hans
    Harsvaer, Ansgar
    Aune, Ragnhild E.
    Weld metal mechanical properties in hyperbaric GTAW of X70 pipeline2006Ingår i: International Journal of Offshore and Polar Engineering, ISSN 1053-5381, Vol. 16, nr 3, s. 233-240Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present investigation, 2 different wires for hyperbaric (underwater) GTA (gas tungsten arc) welding of X70 pipelines have been tested with respect to their weld metal mechanical properties. Welding of full coupons at different pressures (seawater depths of 16, 75 and 200 msw) was done with subsequent weld metal chemical analyses, hardness measurements, tensile testing and Charpy V notch testing as well as microstructure characterization. It is shown that both wires satisfied strength requirements set to X70 grade, representing a weld metal overmatch situation. Both wires gave sufficient impact toughness, but the toughness of the Ni-Mo containing weld was reduced with increasing seawater depth. This observation was strongly linked to the positioning of the Charpy V notch, and crack growth in a brittle, partially transformed region as a consequence of reheating by subsequent stringer beads. The embrittling microstructure consisted of high carbon MA (martensite-austenite constituents islands) decorating prior austenite grain boundaries. This microstructure was less pronounced when welding with the high Ni wire, which may explain why no similar toughness drop was found.

  • 6.
    Arzpeima, Minoodokht
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Björling, Gunilla
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Antimicrobial Efficacy and Degradation Route of Silver-Based Coated Endotracheal Tubes2012Konferensbidrag (Refereegranskat)
  • 7.
    Arzpeima, Minoodokht
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Rosén, Annika
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Sanchez, Javier
    Björling, Gunilla
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Chemotherapy-Induced Surface Degradation and Thrombogenicity of Intravascular Catheters: A Preliminary In-Vitro Study with Focus on Breast Cancer2012Konferensbidrag (Refereegranskat)
  • 8.
    Aune, Ragnhild E.
    KTH, Tidigare Institutioner                               , Metallurgi.
    Thermodynamic studies of some high temperature systems1997Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
  • 9.
    Aune, Ragnhild E.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Battezzati, L.
    Egry, I.
    Etay, J.
    Fecht, H. J.
    Giuranno, D.
    Novakovic, R.
    Passerone, A.
    Ricci, E.
    Schmidt-Hohagen, F.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Wunderlich, R.
    Surface tension measurements of Al-Ni based alloys from ground-based and parabolic flight experiments: Results from the ThermoLab project2006Ingår i: Microgravity, science and technology, ISSN 0938-0108, E-ISSN 1875-0494, Vol. 18, nr 3-4, s. 73-76Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Surface tension measurements of different alloys of the Al-Ni system, performed both under reduced gravity conditions in parabolic flights and on ground by conventional techniques, are presented. The alloys compositions were selected on the basis of the intrinsic compound forming tendency with the aim to allow a sensitive test of model predictions.

  • 10.
    Aune, Ragnhild E.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Battezzati, Livio
    Brooks, Rob
    Egry, Ivan
    Fecht, Hans-Joerg
    Garandet, Jean-Paul
    Mills, Ken C.
    Passerone, Alberto
    Quested, Peter N.
    Ricci, Enrica
    Schneider, Stephan
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Wunderlich, Rainer K.
    Vinet, Bernard
    Measurement of Thermophysical Properties of Liquid Metallic Alloys in a Ground- and Microgravity Based Research Programme - the ThermoLab Project2005Ingår i: Microgravity, science and technology, ISSN 0938-0108, E-ISSN 1875-0494, Vol. 16, nr 1-4, s. 7-10Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ThermoLab project is concerned with the measurement of the thermophysical properties of industrial alloys in the liquid phase. The project combines long and short duration microgravity measurements based on containerless processing with an electromagnetic levitation device and a ground based experimental programme using conventional and containerless processing techniques. An overview of the project and representative results from the ground based experimental programme are given. Alloys investigated included Ni-based, Fe-based, a Cu-Sn-Mg alloy and a gamma-TiAl alloy.

  • 11.
    Aune, Ragnhild E.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Battezzati, Livio
    Brooks, Rob
    Egry, Ivan
    Fecht, Hans-Joerg
    Garandet, Jean-Paul
    Mills, Ken C.
    Passerone, Alberto
    Quested, Peter N.
    Ricci, Enrica
    Schneider, Stephan
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Wunderlich, Rainer K.
    Vinet, Bernard
    Surface Tension and Viscosity of Industrial Alloys from Parabolic Flight Experiments: Results of the ThermoLab Project2005Ingår i: Microgravity, science and technology, ISSN 0938-0108, E-ISSN 1875-0494, Vol. 16, nr 1-4, s. 11-14Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The surface tension and the viscosity of a series of industrial alloys have been measured by the oscillating drop technique with an electromagnetic levitation device under reduced gravity conditions in several parabolic flights. It was demonstrated that the 20 seconds of reduced gravity available in a parabola were sufficient for melting, heating into the liquid phase, and cooling to solidification of typically 7 mm diameter metallic specimen. The surface tension and the viscosity were obtained from the frequency and the damping time constant of the oscillation which were evaluated from the temperature signal of a highresolution pyrometer. Alloys processed included steels, Ni-based superalloys, and Ti-alloys which were supplied by industrial partners to the project. Three to four parabolas were sufficient to obtain the surface tension and the viscosity over a large range in temperature.

  • 12.
    Aune, Ragnhild E.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Battezzati, Livio
    Brooks, Robert
    Egry, Ivan
    Fecht, Hans-Joerg
    Garandet, Jean-Paul
    Hayashi, Miyuki
    Mills, Ken C.
    Passerone, Alberto
    Quested, Peter N.
    Ricci, Enrica
    Schmidt-Hohagen, Frank
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Vinet, Bernard
    Wunderlich, Rainer K.
    Thermophysical properties of IN738lc, MM247lc and CMSX-4 in the liquid and high temperature solid phase2005Ingår i: Superalloys 718, 625, 706 and Derivatives, Proceedings, 2005, s. 467-476Konferensbidrag (Refereegranskat)
    Abstract [en]

    Thermophysical properties of the Ni-based superalloys CMSX-4, IN738LC, and MM247LC have been measured in the liquid and high-temperature solid phase. Properties included calorimetric, thermal transport, the surface tension, and the viscosity. Experiments have been performed in ground-based laboratory using classical calorimetry and rheometry as well as under reduced gravity conditions in an electromagnetic levitation device on board parabolic flights. In this contribution, an overview of the various properties of three Ni-based superalloys is given with emphasis on the surface tension and viscosity as obtained from the parabolic flight experiments. The measurements were performed within a program called ThermoLab dedicated to the measurement of thermophysical properties of industrial alloys.

  • 13.
    Aune, Ragnhild E.
    et al.
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Hayashi, M.
    Nakajima, K.
    Seetharaman, Seshadri
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Thermophysical properties of silicate slags2002Ingår i: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 54, nr 11, s. 62-69Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The optimization of metallurgical processes requires reliable data of the slag phase. This paper focuses on three properties that are relevant to heat and mass-transfer calculations-viscosities, thermal diffusivities, and surface tensions of silicate melts. A brief account of the experimental techniques used for the measurements of these properties, with special reference to the work carried out in the Division of Metallurgy, Royal Institute Of Technology, Stockholm, Sweden, are presented, along with the advantages and limitations. As these properties are structure-oriented, the impact of structure on these properties is also presented. The paper is intended as a state-of-the-art review of the subject.

  • 14.
    Aune, Ragnhild E.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Hayashi, M.
    Sridhar, S.
    Thermodynamic approach to physical properties of silicate melts2005Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 32, nr 2, s. 141-150Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The thermophysical properties of silicate melts are strongly structure dependent. It is well known that the viscosity of slags increases with increasing degree of polymerisation of the silicate anion. Even the thermodynamic properties of slags are dependent on the species type and population in the melt. Thus, a link between the thermophysical and thermochemical properties of silicate melts is logically expected. The present paper elucidates the salient features of Darken's excess stability approach to the Gibbs energy of solution as applied to the viscosities of silicate melts. It is demonstrated that the second derivatives of the viscosities of binary silicate melts with respect to composition indicate maxima corresponding to the existence of stable compounds in these systems. The concept has been successfully applied to the following systems: Al2O3-SiO2, CaO-SiO2, FeO-SiO2, MgO-SiO2 and MnO-SiO2. In all cases, the second derivative plots of viscosities with respect to composition show peaks corresponding to the metasilicates. The second derivatives of the activation energies of viscous flow with respect to temperature have earlier been shown to reflect the formation of associates/embryos in homogeneous silicate melts, indicating the readiness of the melt to separate a solid phase. Thermodynamic coupling of thermal diffusivities in the case of the CaO-Al2O3-SiO2 system from laser flash measurements of these slags, as a function of temperature, has been examined as part of the present study. Densities have been estimated from integral molar enthalpies in the case of silicate systems, and the results are presented.

  • 15.
    Aune, Ragnhild, E
    et al.
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Jacob, K.T
    Seetharaman, Seshadri
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Thermodynamic Data of the Rare Earth Sesquioxides1996Rapport (Övrig (populärvetenskap, debatt, mm))
  • 16.
    Aune, Ragnhild E.
    et al.
    Norwegian Univ Sci & Technol NTNU, Norway.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    The Seetharaman Seminar June 14-15, 2010 in Stockholm, Sweden: Materials Processing Towards Properties2010Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 81, nr 10, s. 811-Artikel i tidskrift (Övrigt vetenskapligt)
  • 17.
    Aune, Ragnhild, E
    et al.
    KTH, Tidigare Institutioner                               , Metallurgi.
    Seetharaman, Seshadri
    KTH.
    Experimental studies of heat capacities of Nd2Fe17, Nd2Fe17N1.49 and Nd2Fe17N1.75 alloys in the temperature range 273-773 K1998Ingår i: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 17, nr 4, s. 299-311Artikel i tidskrift (Refereegranskat)
  • 18.
    Aune, Ragnhild, E
    et al.
    KTH, Tidigare Institutioner                               , Metallurgi.
    Sichen, Du
    KTH.
    Seetharaman, Seshadri
    Phase Relationships in the System Mn-Co-C1997Ingår i: The Japan Society of Calorimetry and Thermal Analysis - Netsu Sokutei, Vol. 24, nr 4, s. 171-178Artikel i tidskrift (Refereegranskat)
  • 19.
    Aune, Ragnhild E.
    et al.
    KTH, Tidigare Institutioner, Materialvetenskap.
    Sridhar, S.
    Hayashi, Miyuki
    Viscosities and Gibbs energies: On a common structural base2004Ingår i: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 22, nr 5/6, s. 369-378Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present paper reviews the extensive work carried out with respect to the modeling of viscosities of high temperature melts carried out in the Division of Metallurgy, Royal Institute of Technology (KTH), Stockholm, Sweden. This work was inspired to a great extent by a past collaboration with Professor Ken Mills at Imperial College, London, UK. A thermodynamic approach based on Richardson's theory of ideal mixing of silicates, was used to predict the viscosities of binary silicates. The second derivative of In eta with respect to composition was used to predict the setting of ordering in a homogeneous silicate melt during cooling as it approaches the liquidus temperature. The paper clearly demonstrates the powerfulness of the thermodynamic approach to physical properties of high temperature melts.

  • 20.
    Aune, Ragnhild, E
    et al.
    KTH, Tidigare Institutioner                               , Metallurgi.
    Sridhar, S
    Sichen, Du
    A Galvanic Cell Study Of the Ni-W-O System in the Temperature Range 1034-1317 K1994Ingår i: Journal of Chemical Thermodynamics, ISSN 0021-9614, E-ISSN 1096-3626, Vol. 26, nr 5, s. 493-505Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Experimental studies of the standard molar Gibbs free energy of formation of NiWO4 have been carried out using a solid-state galvanic cell involving (zirconium oxide + calcium oxide) electrolyte in the temperature range T = 1034 K to 1317 K. The galvanic cell used can be represented as

    -Pt|{(1 - δ)Ni + δW}(f.c.c.), NiWO4(s), WO2.72(s)|(1 - x)ZrO2 + x CaO|NiO(s), Ni(s)|Pt+,

    where δ « 1. The e.m.f. against temperature plot shows a break at T ≈ 1167 K, indicating a possible phase transformation occurring in the ternary mixture. These studies were complemented by X-ray-diffraction studies of some ternary mixtures equilibrated at T = 1073 K and 1273 K. A thermodynamic assessment of (nickel + tungsten + oxygen) was carried out as part of the present work, incorporating the present results along with those available in the literature for the ternary as well as the three binaries involved. The isothermal sections at T = 1073 K and 1273 K are presented.

  • 21.
    Aune, Ragnhild Elizabeth
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Heikkinen, E. -P.
    Koponen, J.
    Samuelsson, C.
    Heiskanen, K.
    Progress report by the Nordic International Masters Platform (NIMP) Operative group2006Rapport (Övrigt vetenskapligt)
  • 22.
    Aune, Ragnhild Elizabeth
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Kekkonen, Marko
    Proceedings of the Symposium in Honour of Professor Lauri E. Holappa of the Helsinki University of Technology: Metal Separation Technologies III2004Proceedings (redaktörskap) (Refereegranskat)
  • 23.
    Aune, Ragnhild Elizabeth
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Experimental designs toward an understanding of process phenomena in steelmaking2006Ingår i: Iron and Steel Technology, ISSN 1547-0423, Vol. 3, nr 12, s. 137-146Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Various experimental studies towards the understanding of different process phenomena in iron and steelmaking were presented. Thermal diffusivity measurement was carried out at various temperature to monitor the structural changes occurring in coke. X-ray diffraction measurements were carried out to determine the average crystallite size of graphite along the structural c-axis and in the structural ab plane. It was observed that the apparent thermal diffusivity during the cooling cycle is larger than the heating cycle. Many experiments were also conducted in a high-temperature x-ray diffraction unit, to study the rate of graphitization at any given temperature for a given coke sample. An experimental design for the investigation of the mechanism of reduction in the blast furnace shaft, and the role of coke by dynamic x-ray photography was also carried out. The heating and melting of a mold flux during continuous casting were also simulated in specially designed laboratory.

  • 24.
    Aune, Ragnhild Elizabeth
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Experimental designs towards an understanding of process phenomena in steel making2005Ingår i: ICS 2005: Proceedings of the 3rd International Congress on the Science and Technology of Steelmaking, 2005, s. 381-392Konferensbidrag (Refereegranskat)
  • 25.
    Aune, Ragnhild Elizabeth
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Experimental Designs towards an Understanding of Process Phenomena in Steel Making2006Ingår i: Iron & Steel Technology, ISSN 1547-0423, Vol. 3, nr 12, s. 137-146Artikel i tidskrift (Refereegranskat)
  • 26.
    Aune, Ragnhild Elizabeth
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Thermodynamic Aspects of Metals Processing2005Ingår i: Fundamentals of Metallurgy / [ed] Seshadri Seetharaman, Woodhead Publishing Limited, 2005, s. 38-81Kapitel i bok, del av antologi (Refereegranskat)
  • 27.
    Backman, Sara
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Björling, Gunilla
    Johansson, Unn-Britt
    Lysdahl, Michael
    Markström, Agneta
    Schedin, Ulla
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Frostell, Claes
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Material Wear of Polymeric Tracheostomy Tubes: A Six-Month Study2009Ingår i: The Laryngoscope, ISSN 0023-852X, E-ISSN 1531-4995, Vol. 119, nr 4, s. 657-664Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objectives: The objectives were to study long-term material wear of tracheostomy tubes made of silicone (Si), polyvinyl chloride (PVC), and polyurethane (PU) after 3 and 6 months of clinical use. Study Design: The study has a prospective and comparative design. Methods: Nineteen patients with long-term tracheostomy, attending the National Respiratory Center in Sweden, were included, n = 6 with Si tubes, n = 8 with PVC tubes, and n = 5 with PU tubes. The tubes were exposed to the local environment, in the trachea for 3 and 6 months and analyzed by scanning electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, and differential scanning calorimetry. Results: All tubes revealed severe surface changes. No significant differences were established after 3 or 6 months of exposure between the various materials. The changes had progressed significantly after this period, compared to previously reported changes after 30 days of exposure. The results from all analyzing techniques correlated well. Conclusions: All tubes, exposed in the trachea for 3-6 months, revealed major degradation and changes in the surface of the material. Polymeric tracheostomy tubes should be changed before the end of 3 months of clinical use.

  • 28.
    Beheshti, Reza
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Akhtar, Shahid
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Heat treatment of black dross for the production of a value added material - a preliminary study2012Ingår i: EPD Congress 2012, John Wiley & Sons, 2012, s. 353-360Konferensbidrag (Refereegranskat)
    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.

  • 29.
    Beheshti, Reza
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Moosberg-Bustnes, J.
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Modeling and simulation of isothermal reduction of a single hematite pellet in gas mixtures of H2 and CO2014Ingår i: TMS 2014 143rd Annual Meeting & Exhibition, Annual Meeting Supplemental Proceedings, The Minerals, Metals, and Materials Society, 2014, s. 495-502Konferensbidrag (Refereegranskat)
    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.

  • 30. Björling, Gunilla
    et al.
    Arzpeima, Minoodokht
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Considerations in Tube Selection2011Konferensbidrag (Refereegranskat)
  • 31. Björling, Gunilla
    et al.
    Axelsson, Sara
    Johansson, Unn-Britt
    Lysdahl, Michael
    Aune, Ragnhild Elizabeth
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Frostell, Claes
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Long-Term Tracheostomy: Aspects on Tube Change and Material Wear2007Konferensbidrag (Refereegranskat)
    Abstract [en]
    • The tracheostomy tubes in use are exposed not only to bacteria but also the lining fluids, which are a first defence against toxicity in inhaled gases. It contains several antioxidants. The complex bacteriological environment in the trachea, as well as the formation of a biofilm on the tube surface through colonization of bacteria, is believed to affect the mechanical and chemical properties of the tube material. The study was conducted at the National Respiratory Centre (NRC) at Danderyd Hospital in collaboration with the Royal Institute of Technology and Sophiahemmet University College in Stockholm, Sweden.
  • 32. Björling, Gunilla
    et al.
    Axelsson, Sara
    Johansson, Unn-Britt
    Lysdahl, Michael
    Markström, Agneta
    Schedin, Ulla
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Frostell, Claes
    Karlsson, Sigbritt
    Clinical use and material wear of polymeric tracheostomy tubes2007Ingår i: The Laryngoscope, ISSN 0023-852X, E-ISSN 1531-4995, Vol. 117, nr 9, s. 1552-1559Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    OBJECTIVES: The objectives were to compare the duration of use of polymeric tracheostomy tubes, i.e., silicone (Si), polyvinyl chloride (PVC), and polyurethane (PU), and to determine whether surface changes in the materials could be observed after 30 days of patient use. METHODS: Data were collected from patient and technical records for all tracheostomized patients attending the National Respiratory Center in Sweden. In the surface study, 19 patients with long-term tracheostomy were included: six with Bivona TTS Si tubes, eight with Shiley PVC tubes, and five with Trachoe Twist PU tubes. All tubes were exposed in the trachea for 30 days before being analyzed by scanning electron microscopy (SEM) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). New tubes and tubes exposed in phosphate-buffered saline were used as reference. RESULTS: Si tubes are used for longer periods of time than those made of PVC (P < .0001) and PU (P = .021). In general, all polymeric tubes were used longer than the recommended 30-day period. Eighteen of the 19 tubes exposed in patients demonstrated, in one or more areas of the tube, evident surface changes. The morphologic changes identified by SEM correlate well with the results obtained by ATR-FTIR. CONCLUSIONS: Si tracheostomy tubes are in general used longer than those made of PVC and PU. Most of the tubes exposed in the trachea for 30 days suffered evident surface changes, with degradation of the polymeric chains as a result.

  • 33. Björling, Gunilla
    et al.
    Lysdahl, Michael
    Markström, Agneta
    Schedin, Ulla
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Frostell, Claes
    Johansson, Unn-Britt
    Health-Related Quality of Life and Patient Experiences of Long-Term Tracheostomy2009Konferensbidrag (Refereegranskat)
  • 34. Fecht, H. -J
    et al.
    Schneider, S.
    Wunderlich, R. K.
    Battezzati, L.
    Papandrea, C.
    Palumbo, M.
    Egry, I.
    Mills, K.
    Quested, P.
    Brooks, R.
    Giuranno, D.
    Novakovic, R.
    Passerone, A.
    Ricci, E.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Vinet, B.
    Garandet, J. -P
    Measurement of thermophysical properties of liquid metallic alloys in a ground- And microgravity based research program. The Thermolab Project2005Ingår i: La Metallurgia Italiana, ISSN 0026-0843, Vol. 97, nr 3, s. 47-51Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An outline of the Thermolab Project is reported with the aim of informing on the wide range of properties which are becoming available for some industrial alloys. Selected examples of experiments and properties are provided.

  • 35. Fritzsch, R.
    et al.
    Akbarnejad, Shahin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Aune, Ragnhild Elizabeth
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    A novel method for automated quantification of particles in solidified aluminium2014Ingår i: TMS 2014 143rd Annual Meeting & Exhibition, Annual Meeting Supplemental Proceedings, The Minerals, Metals, and Materials Society, 2014, s. 535-543Konferensbidrag (Refereegranskat)
    Abstract [en]

    Particle concentration and size distribution in the melt can give important information regarding the filtration efficiency and the quality of the aluminium. LiMCA (Liquid Metal Cleanliness Analyser) system, used in primary and secondary production of aluminium, provides in-situ data for granulometric and total density information on the inclusion content, but has problems quantifying particles < 20 μm in size. To be able to determine the required cleanliness with particle counts down' to 10 μm for modern alloys a novel method for automated quantitative results has been developed. Results are obtained using a user friendly technique based on the ImagePro® Plus 7.0 software. The different image processing steps adopted for automated quantification of the particle count in a size range from 2 to 50 μm is described and discussed together with the obtained results. The automated technique has been benchmarked elsewhere with a manual particle count reviling an error of ∼3% on the overall filtration efficiency.

  • 36. Fritzsch, R.
    et al.
    Kennedy, M. W.
    Bakken, J. A.
    Aune, Ragnhild Elizabeth
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Electromagnetic priming of Ceramic Foam Filters (CFF) for liquid aluminum filtration2013Ingår i: TMS Light Met., 2013, nr Light Metals 2013 - At the TMS 2013 Annual Meeting and Exhibition, s. 973-979Konferensbidrag (Refereegranskat)
    Abstract [en]

    Commercial Ceramic Foam Filters (CFF) of 30, 50 and 80 Pores Per Inch (PPI) have been primed, using magnetic field strengths of 0.06-0.2T, for periods of 1-10 minutes. The influence of time and field strength on the gas removal from the CFF structure, and the resulting improvements in filter productivity, are discussed. The obtained results are related to Finite Element Modeling (FEM) of the metal flow fields induced by the electromagnetic Lorentz forces. Higher filtration rates were obtained for 50 PPI magnetically primed, than for 30 PPI gravity primed filters. This suggests that electromagnetic priming offers an opportunity to use 50 PPI filters, with a higher overall filtration efficiency than 30 PPI filters, in existing cast house applications where the low productivity/high priming head of these filters would otherwise rule them out. Estimated filtration efficiency of different filter types are presented as functions of velocity and thickness.

  • 37. Fritzsch, R.
    et al.
    Mirzaei, B.
    Kennedy, M. W.
    Aune, Ragnhild Elizabeth
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Automated quantification of SiC-particles in solidified A356 aluminium using ImagePro® plus 7.02013Ingår i: TMS Annu Meet, 2013, s. 69-77Konferensbidrag (Refereegranskat)
    Abstract [en]

    The quantitative particle concentration can give important information about the cleanliness of melts for quality control in primary and secondary production of aluminum. Manual quantification of the particle concentration is normally a time consuming process and human control can bias the acquired images and particle count. The present paper explains the automated image-processing steps for the quantification of SiC-particles, with equivalent diameters from 2 to 25 μm, in solidified A356. A total of 700 micrographs, acquired with a standard white light microscope with 10 x magnification, were analyzed. The applied software (Image Pro-Plus 7.0 from MediaCybernetics®) allows for programming of macros which in turn provides the user with a higher degree of control. The automated results are compared with the results obtained by manually counting the particles in the same micrographs. The impact of the automated results on the estimated filtration efficiency was established to be only ∼3%.

  • 38. Hong, V. V.
    et al.
    Aune, Ragnhild E.
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Phuc, N. X.
    Seetharaman, Seshadri
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Nitrogenation studies of Nd2Fe17 alloys2003Ingår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 327, nr 04-feb, s. 404-409Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present investigation, the kinetics of nitrogenation of Nd2Fe17 alloys were studied in order to optimize the magnetic properties of the pure Nd2Fe17 alloy by the introduction of nitrogen interstitials. The nitrogenation kinetics was followed in the temperature interval 1173-1473K by the use of the thermogravimetric (TG) technique. The nitrogenated alloys were prepared from a Nd2Fe17 master alloy by heat treating in different partial pressures of nitrogen under well-controlled conditions. The results of the TG experiments showed that there was an initial incubation time before the onset of nitrogenation. The length of the incubation period was found to be a function of temperature and the partial pressure of nitrogen in the gas. The nitrogen used was of high purity (99.9999% N-2). The gas purification system adopted in the present work could effectively remove traces of reducing as well as oxidizing impurity gases in the system. In order to remove the traces of CO, CH4 and H-2, (as well as other hydrocarbons) if present, the gas was passed through a column of Cu turnings kept at 973 K. The lower portion of the Cu column was surface oxidized. The reducing gases got oxidized passing through this column and CO2 and H2O were formed. Further, the oxygen impurity in the gas (ca. 10(-2) Pa) could react with the remaining reducing gases. These products were absorbed by columns of ascarite and dehydrite, respectively. Remaining oxygen impurity in the gas could then be removed by passing the gas through a furnace containing Mg turnings at 773 K. The rate of nitrogen uptake after this period was found to increase with increasing temperature. After an initial rapid nitrogenation period, the reaction rate was found to slow down, possibly due to nitrogen atoms diffusing into the bulk. The reaction was found to be rapid, and the incubation time was conspicuously absent, when nitrogen gas was used without the purification steps mentioned earlier. Oxygen impurity in the gas was found to have a strong influence on the reaction kinetics. Heat capacity measurements, as well as magnetic hysteresis measurements, were also conducted. The heat capacity of the Nd2Fe17 master alloy, as well as that of the nitrogenated alloys, Was determined in the temperature interval 293-773 K by the use of the differential scanning calorimetric technique. From the experimental heat-capacity data the Curie temperatures of the alloys were derived. Compared to the master alloy, significantly increased Curie temperatures were obtained for the nitrogenated alloys. The magnetic measurements were conducted at 300 K by the use of a quantum design magnetometer. The results obtained indicate that the nitrogenated alloys were soft magnets as no large hysteresis loop was found to exist.

  • 39.
    Jönsson, Pär
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Du, Sichen
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Matsushita, Taishi
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Sundberg, Sven
    The Seetharaman Seminar June 14-15, 2010 in Stockholm, Sweden2012Ingår i: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 31, nr 3, s. 193-193Artikel i tidskrift (Övrigt vetenskapligt)
  • 40.
    Kaali, Peter
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Momcilovic, Dane
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Markstrom, Agneta
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Czel, Gyorgy
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Degradation of Biomedical Polydimethylsiloxanes During Exposure to In Vivo Biofilm Environment Monitored by FE-SEM, ATR-FTIR, and MALDI-TOF MS2010Ingår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 115, nr 2, s. 802-810Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polymers used for biomedical purposes in medical devices are usually requested to be inert to degradation. This article describes that slow irreversible changes were observed in silicone surfaces exposed to in vivo biofilms even if silicone, in general, is supposed to have excellent long-term properties. Tracheostomy tubes made of silicone rubber were exposed to in vivo biofilm environments in clinical tests for periods of 7, 3, and 6 months. The chemical degradation was monitored by MALDI-TOF MS, ATR-FTI.R, and FE-SEM. In addition, the physical changes were monitored by contact angle and hardness measurements. Cyclic polydimethylsiloxane (PDMS) was detected on the surfaces of new (unaged) silicones. On the surfaces of the in vivo samples new compounds, presumably linear methyl-hydroxyl-terminated PDMS, were detected in addition to cyclic PDMS. These compounds may be formed as a result of the hydrolysis of linear dimethyl terminated PDMS, which is also present in the silicone rubber. ATR-FTIR spectroscopy confirmed that hydrolysis had indeed occurred during the in vivo exposure, since Si-OH groups were detected. Furthermore, significant changes in the topography were detected by FE-SEM, indicating the initiation of degradation. No significant changes in the contact angle of the in vivo used samples were observed, but this information may be shielded by the fact that biofilm may remain on the surface, despite the thorough cleaning before the analysis. It is also possible that the surface hydrophobicity was recovered by the diffusion of linear low-molecular-weight compounds from the bulk.

  • 41.
    Kaali, Peter
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Pérez-Madrignal, Maria M.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Czel, Gyorgy
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    The influence of Ag(+), Zn(2+) and Cu(2+) exchanged zeolite on antimicrobial and long term in vitro stability of medical grade polyether polyurethane2011Ingår i: Express Polymer letters, ISSN 1788-618X, Vol. 5, nr 12, s. 1028-1040Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study aims to investigate the limitations and applicability of different ion exchanged zeolites as antimicrobial additive in thermoplastic polyether type polyurethanes. These composites were designed to improve the health quality of hospitalized patients by expressing both biocompatibility and relevant antimicrobial activity. The zeolites were exchanged with silver, copper and zinc ions and single, binary and ternary ion-exchanged zeolite-polyurethane composites were prepared. The antimicrobial activity and the resistance of the composites against the human environment play vital role in the applicability of the materials as a medical device therefore these properties were investigated. The antimicrobial test were performed on Methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa and Candida tropicalis. The tests showed that the efficiency of the silver ions is superior to the other single ionic systems. Besides, the binary and ternary ion-exchanged samples had similar antimicrobial efficiency regardless the type of the ions in the zeolite. The biocompatibility tests were carried out in-vitro in artificial body fluids for a period of 12 weeks. As a result of the in-vitro test, degradation of the composites were observed and the structural changes of the materials were detected and described by Scanning Electron Microscopy, Contact Angle measurements and Attenuated Total Reflection Fourier Transform Infrared Spectroscopy.

  • 42.
    Kaali, Peter
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Czel, Gyoergy
    Department of Polymer Engineering, University of Miskolc.
    Momcilovic, Dane
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Antimicrobial properties of Ag+ loaded zeolite polyester polyurethane and silicone rubber and long-term properties after exposure to in-vitro ageing2010Ingår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 95, nr 9, s. 1456-1465Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In biomedical applications, tubes (e.g. catheters etc.) are commonly produced from polyurethane (PU) and silicone rubber which are known to be biocompatible materials. Several studies have shown that tubes, which are connected to the body (invasive) (especially urinary, tracheotomy and central venous catheters) are associated with infections. The present study reports the development of a new method aiming at obtaining antibacterial properties for PU and silicone rubber by mixing respective material with a natural antibacterial agent (Ag+ loaded zeolite) in different weight fractions. The influence of the zeolite content on the antimicrobial properties were analysed by exposure to bacteria (ISO 22196) and mixtures of fungi (ISO 846). The materials were also subject to artificial body fluids (Artificial Lysosomal Fluid (ALF) and Gamble's solution) for periods up to three months and the subsequent changes in the chemical properties after in-vitro exposure were determined by Matrix Assisted Laser Deposition/Ionization Time Of Flight Mass Spectrometry (MALDI-TOF MS) and Attenuated Total Reflection Fourier Transform Infra Red spectroscopy (ATR-FTIR). It was established that the antimicrobial effect of the materials increased with the increase of the zeolite content. The wettability of the materials was found to decrease significantly during the in-vitro exposure, but this could not be correlated to the zeolite content. In the PU samples, the formation of free carbonyl and -OH groups was observed, which corresponds to oxidative degradation. In case of the silicone rubber the ratio of cyclic PDMS to linear PDMS (H, CH3 and dimethyl terminated) decreased, which indicates a change in the concentration of the compounds. The formation and increase of the O-H bond during the exposure was also confirmed by the infrared spectra of the material which corresponds to hydrolysis of the silicone rubber.

  • 43.
    Kaali, Peter
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Czel, Gyorgy
    Modelling the ion distribution in single, binary and ternary ion exchanged Azeolite2011Ingår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093Artikel i tidskrift (Övrigt vetenskapligt)
  • 44. Kennedy, M. W.
    et al.
    Akhtar, S.
    Bakken, J. A.
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Dept. of Material Science and Engineering, Norwegian University of Science and Technology (NTNU), N-7491, Trondheim, Norway.
    Analytical and fem modeling of aluminum billet induction heating with experimental verification2016Ingår i: Light Metals 2012, Springer International Publishing , 2016, s. 269-275Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    Induction heating is commonly used in the re-heating of aluminum billets before forging or extrusion. Powerful finite element modeling (FEM) tools are available to assist in the design of such processes; however, such models should be validated by comparison with analytical solutions or experimental results to ensure accuracy. Induction heating experiments have been performed using a number of different coil designs and work piece dimensions at 50 Hz. Aluminum alloys with different electrical conductivities have been used, i.e. 6060 and A356. Process parameters such as: current, power, magnetic field, electrical conductivity, etc. have been measured with high precision instrumentation. Experimental data are presented and compared with equivalent 1D analytical and 2D axial symmetric FEM modeling results. The effect of frequency on the induction heating process is reviewed using the validated analytical and FEM models. Some recommendations are given with respect to appropriate modeling techniques, boundary conditions and numerical mesh sizes.

  • 45. Kennedy, M. W.
    et al.
    Akhtar, S.
    Bakken, J. A.
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap. Department of Materials Science and Engineering, Norwegian University of Science and Technology, Norway.
    Review of classical design methods as applied to aluminum billet heating with induction coils2011Ingår i: TMS Annual Meeting, 2011, s. 707-722Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the present study classical induction design tools are applied to the problem of heating non-magnetic metal billets, using 50 Hz AC. As an example of great practical industrial interest, the induction heating of aluminum billets is addressed specifically. The predicted work piece power is compared with the measured work piece power for a long and a short coil, using well established methods, such as those of Burch and Davis, introduced in 1926/28, Dwight and Bagai in 1935, Baker in 1944/57, Vaughan and Williamson in 1945, and by Tudbury in 1960. A calculation methodology based on a combination of the available tools is also introduced and discussed. The method has proven to give an error of <10% of the actual work piece power. An equation for Tudbury's work piece shortness correction factor is disclosed for the first time.

  • 46.
    Kennedy, Mark W.
    et al.
    Norwegian University of Science and Technology, Trondheim, Norway .
    Akhtar, S.
    Bakken, J. A.
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Analytical and FEM modeling of aluminum billet induction heating with experimental verification2012Ingår i: Light Metals 2012, John Wiley & Sons, 2012, s. 269-275Konferensbidrag (Refereegranskat)
    Abstract [en]

    Induction heating is commonly used in the re-heating of aluminum billets before forging or extrusion. Powerful finite element modeling (FEM) tools are available to assist in the design of such processes; however, such models should be validated by comparison with analytical solutions or experimental results to ensure accuracy. Induction heating experiments have been performed using a number of different coil designs and work piece dimensions at 50 Hz. Aluminum alloys with different electrical conductivities have been used, i.e. 6060 and A356. Process parameters such as: current, power, magnetic field, electrical conductivity, etc. have been measured with high precision instrumentation. Experimental data are presented and compared with equivalent 1D analytical and 2D axial symmetric FEM modeling results. The effect of frequency on the induction heating process is reviewed using the validated analytical and FEM models. Some recommendations are given with respect to appropriate modeling techniques, boundary conditions and numerical mesh sizes.

  • 47. Kennedy, Mark W.
    et al.
    Akhtar, S.
    Bakken, J. A.
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Empirical Verification of a Short Coil Correction FactorManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The magnetic field produced in the air-gap by any particular 'short coil' at a fixed current, is affected by a highly complex interaction of the coil and work piece geometries and changes in frequency. A frequency modified semi-empirical short coil correction factor, based upon the formula published by Vaughan and Williamson in 1945, is presented and experimentally verified. This new equation is shown to predict the total system reactive power and the average magnetic flux at the surface of the work piece with typical differences of less than 2% at 50 Hz AC and to accurately predict work piece heating rates typically within 5% for aluminum billets at 50 Hz to 500 kHz AC. The work piece real and reactive powers, and total system reactive power are compared with both analytic and 2D axial symmetric FEM model solutions, as a function of operating frequencies from 50 Hz to 500 kHz. Measured flux density is compared to FEM and analytical predictions at 50 Hz.

  • 48. Kennedy, Mark W.
    et al.
    Akhtar, Shahid
    Norwegian University of Science and Technology (NTNU) Trondheim, Norway.
    Bakken, Jon Arne
    Aune, Ragnhild E.
    Norwegian University of Science and Technology (NTNU) Trondheim, Norway.
    Analytical and Experimental Validation of Electromagnetic Simulations Using COMSOL®, re Inductance, Induction Heating and Magnetic Fields2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a snap shot of experimental work, which has been conducted at NTNU on billet heating with induction coils. A significant volume of experimental data have been collected for coils running with up to 0.2T: high accuracy Hall probe readings (+/-1%), metal conductivity (+/-0.5%), and heat generation (+/- 4%) have been collected.Results are analyzed using newly developed analytical models and COMSOL 2D axial symmetric models. Agreement is exceptionally good for both magnetic field strength/distribution and induced heating in the aluminium billets.

  • 49. Kennedy, Mark W.
    et al.
    Akhtar, Shahid
    Bakken, Jon Arne
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Effect of Electromagnetic Lorentz Force on the Distribution of Inclusions Removed from Liquid Aluminum by a Ceramic Foam Filter in Continuous Filtration Tests2012Konferensbidrag (Refereegranskat)
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    Bakken, Jon Arne
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
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