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  • 1.
    Ahmadkhaniha, Donya
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Huang, Y.
    University of Southampton, Southampton, UK.
    Jaskari, M.
    University of Oulu, Nivala, Finland.
    Järvenpää, A.
    University of Oulu, Nivala, Finland.
    Heydarzadeh Sohi, M.
    University of Tehran, Tehran, Iran.
    Zanella, Caterina
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Karjalainen, L.P.
    University of Oulu, Oulu, Finland.
    Langdon, T.G.
    University of Southampton, Southampton, UK..
    Effect of high-pressure torsion on microstructure, mechanical properties and corrosion resistance of cast pure Mg2017Conference paper (Refereed)
    Abstract [en]

    High-pressure torsion (HPT) processing was applied to cast pure Mg pieces and its effects on microstructure, hardness and tensile properties as well as corrosion resistance were evaluated. The microstructure of the processed samples was examined by electron backscatter diffraction (EBSD) and the mechanical properties were determined by microhardness and tensile tests. Corrosion resistance of the samples was studied via electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution. The results showed that HPT refined the grain size of Mg very effectively from millimeters in the cast structure to a few micrometers homogeneously through the thickness and created a basal texture on the surface. One or five turns of HPT produced no significant difference in the grain size of the processed Mg but the hardness was a maximum after one turn. The yield strength of the cast Mg was increased by seven times whereas the corrosion resistance was not affected by the HPT processing.

  • 2.
    Ahmadkhaniha, Donya
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Huang, Yi
    Materials Research Group, Department of Mechanical Engineering, University of Southampton, Southampton, United Kingdom.
    Jaskari, Matias
    Kerttu Saalasti Institute, University of Oulu, Nivala, Finland.
    Järvenpää, Antti
    Kerttu Saalasti Institute, University of Oulu, Nivala, Finland.
    Sohi, Mahmoud Heydarzadeh
    School of Metallurgy and Materials, College of Engineering, University of Tehran, Tehran, Iran.
    Zanella, Caterina
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Karjalainen, L. Pentti
    Centre for Advanced Steels Research, University of Oulu, Oulu, Finland.
    Langdon, Terence G.
    Materials Research Group, Department of Mechanical Engineering, University of Southampton, Southampton, United Kingdom.
    Effect of high-pressure torsion on microstructure, mechanical properties and corrosion resistance of cast pure Mg2018In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 53, no 24, p. 16585-16597Article in journal (Refereed)
    Abstract [en]

    High-pressure torsion (HPT) processing was applied to cast pure magnesium, and the effects of the deformation on the microstructure, hardness, tensile properties and corrosion resistance were evaluated. The microstructures of the processed samples were examined by electron backscatter diffraction, and the mechanical properties were determined by Vickers hardness and tensile testing. The corrosion resistance was studied using electrochemical impedance spectroscopy in a 3.5% NaCl solution. The results show that HPT processing effectively refines the grain size of Mg from millimeters in the cast structure to a few micrometers after processing and also creates a basal texture on the surface. It was found that one or five turns of HPT produced no significant difference in the grain size of the processed Mg and the hardness was a maximum after one turn due to recovery in some grains. Measurements showed that the yield strength of the cast Mg increased by about seven times whereas the corrosion resistance was not significantly affected by the HPT processing. 

  • 3.
    Ahmadkhaniha, Donya
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Pinate, Santiago
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Leisner, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. RISE Research Institute of Sweden, Borås.
    Zanella, Caterina
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Electrodeposition of Ni high P composite coatings containing nano and submicro ceramic particles2017Conference paper (Other academic)
    Abstract [en]

    In this study, electrodeposition of Ni-P composite coatings has been carried out to investigate the possibility of replacing hard chromium coatings. Therefore, electrodeposition of Ni-P based composite coating with different SiC particle size (50 nm, 100 nm and 500 nm) or B4C (500 nm) was performed. The coating’s composition was evaluated by energy dispersive spectroscopy (EDS), microhardness of the coatings was measured by Vickers indentor and polarization measurements were carried out to study the corrosion behavior of the coatings. The results showed that B4C particles can codeposit in higher percent respect to SiC ones. Ceramic particles increased microhardness of Ni-P coatings to 700HV0.01. The polarization behavior of all the coatings in 3.5% NaCl was similar in as plated state proving that particles did not hindered the passive behaviour. Finally, the effect of heat-treatment (at 400 ºC for 1 hour) on the coating’s properties was studied to compare the contribution of particles and heat-treatment on mechanical and corrosion properties of the coatings. Heat-treatment increased the coating’s microhardness and changed the anodic polarization behavior of the coatings respect to the as plated conditions.

  • 4.
    Ahmadkhaniha, Donya
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Eriksson, Fredrik
    Linkopings universitet, Department of Physics, Linkoping, Sweden.
    Leisner, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. RISE Research Institute of Sweden, Borås, Sweden.
    Zanella, Caterina
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Effect of SiC particle size and heat-treatment on microhardness and corrosion resistance of NiP electrodeposited coatings2018In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 769, p. 1080-1087Article in journal (Refereed)
    Abstract [en]

    Electrodeposition of NiP composite coatings with nano and sub-micron sized SiC has been carried out to investigate the possibility of replacing hard chromium coatings. The composition and structure of the coatings were evaluated by energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis, respectively. Microhardness was measured by Vickers indentation and polarization measurements were carried out to study the corrosion behavior of the coatings. The results showed that submicron particles can be codeposited with a higher content as compared to nano sized ones. However, even if a smaller amount of the nano-sized SiC particles are incorporated in the coating, the contribution to an increasing microhardness was comparable with the submicron sized particles, which can be related to the higher density of codeposited particles. SiC particles did not change the anodic polarization behavior of NiP coatings in a 3.5% NaCl solution. Finally, the effect of heat-treatment on the coatings properties at 400 °C for 1 h was studied to investigate the contribution of particles and heat-treatment on hardness and corrosion properties. It was found that the heat-treatment doubled the microhardness and changed the anodic polarization behavior of the coatings from passive to active with respect to the as-plated conditions.

    The full text will be freely available from 2020-08-04 00:00
  • 5.
    Aladov, V ,A.
    et al.
    RAS, Submicron Heterostruct Microelect Res & Engn Ctr, St Petersburg, Russia.
    Belov, Ilja
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Valyukhov, V. P.
    Peter Great St Petersburg Polytech Univ, St Petersburg, Russia.
    Zakgeim, A. L.
    RAS, Submicron Heterostruct Microelect Res & Engn Ctr, St Petersburg, Russia.
    Chernyakov, A. E.
    RAS, Submicron Heterostruct Microelect Res & Engn Ctr, St Petersburg, Russia.
    A study of thermal regime in the high-power LED arrays2018In: St. Petersburg Polytechnical University Journal: Physics and Mathematics, ISSN 2405-7223, Vol. 11, no 3, p. 39-51Article in journal (Refereed)
    Abstract [en]

    Thermal resistance and temperature distribution for high-power AlGaInN LED chip-on-board arrays were measured by different methods and tools. The p-n junction temperature was determined through measuring a temperature-dependent forward voltage drop on the p-n junction, at a low measuring current after applying a high heating current. Furthermore, the infrared thermal imaging technique was employed to obtain the temperature map for the test object. A steady-state 3D computational model of the experimental setup was created including temperature-dependent power dissipation in the LED chips. Simulations of the heat transfer in the LED array were performed to further investigate temperature gradients observed in the measurements. Simulations revealed possible thermal deformation of the assembly as the reason for the hot spot formation. The bending of the assembly was confirmed by surface curvature measurements.

  • 6.
    Ali, Sharafat
    et al.
    Science and Technology Division, Corning Incorporated, Corning, NY, United States.
    Bogdanoff, Toni
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Jonson, Bo
    School of Engineering, Department of Built Environment and Energy Technology, Linnæus University, Växjö, Sweden.
    Hardness, elastic modulus and refractive index of oxynitride glasses prepared from woody biofuel ashes2017In: European Journal of Glass Science and Techology. Part B. Physics and Chemistry of Glasses, ISSN 1753-3562, Vol. 58, no 6, p. 231-236Article in journal (Refereed)
    Abstract [en]

    This paper reports the hardness, elastic modulus and refractive index values of the oxynitride glasses prepared from woody biofuel ashes. The glasses were prepared in nitrogen atmosphere at 1350-1500°C with addition of Ca metal as a precursor to the extra addition of this modifier. The glasses were homogenous, but appeared translucent grey to black. They contained up to 23 eq% of Ca and 5 eq% of N. The glass densities vary slightly between 2·76 to 2·92 g/cm3. The molar volume and compactness values vary between 8·01 cm3/mol to 8·31 cm3/mol and 0·446 to 0·462 respectively. Mechanical properties like hardness and reduced elastic modulus show values, up to 10 and 105 GPa, respectively. These properties are strongly correlated with the amount of N in the glass. The refractive index (1·54-1·75) increases with increasing N and Ca contents.

  • 7.
    Amieva Llavona, Jose Manuel
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Influence of Molybdenum on mechanical and thermal properties in lamellar graphite cast iron2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this work hypoeutectic lamellar graphite iron alloyed with seven different levels of molybdenum was studied in order to characterize its thermal and mechanical properties. Several tests were conducted and experimental data was collected from, laser flash (LFA), differential scanning calorimeter (DSC), dilatometer and tensile test.

    Micrographs taken from the polished specimens were captured and studied through quantitative measurements of several parameters, e.g. graphite fraction, shape, form. Afterward, the same samples were colour etched with picric acid in order to perform a qualitative analysis of the matrix.

    It was concluded from the data collected, that molybdenum has a significant influence in the UTS. Such influence, increases the UTS strongly with the amount of molybdenum. It was also found that the pearlitic matrix changes into ausferrite matrix, for the 0.96% of molybdenum, but ausferrite it is detected from 0.65% of molybdenum onwards. Regarding thermal properties, molybdenum does not have noticeable effect but it is possible to see a clear worsen in the conductivity in the specimen, which has ausferrite as matrix.

    Graphite does not seem to have a clear behavior with the different concentration of molybdenum but in the other hand, the matrix shows clear differences as it was mention before.

    During solid state reaction, it was detected a clear influence of molybdenum additions, where the latent heat and the volumetric change were measured during the eutectoid reaction and show a decreasing behavior for molybdenum contents above 0.65%.

  • 8.
    Andriollo, Tito
    et al.
    Department of Mechanical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark.
    Hellström, Kristina
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Sonne, Mads R.
    Department of Mechanical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark.
    Thorborg, Jesper
    Department of Mechanical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark.
    Tiedje, Niels
    Department of Mechanical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark.
    Hattel, Jesper
    Department of Mechanical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark.
    Uncovering the local inelastic interactions during manufacture of ductile cast iron: How the substructure of the graphite particles can induce residual stress concentrations in the matrix2018In: Journal of the mechanics and physics of solids, ISSN 0022-5096, E-ISSN 1873-4782, Vol. 111, p. 333-357Article in journal (Refereed)
    Abstract [en]

    Recent X-ray diffraction (XRD) measurements have revealed that plastic deformation and a residual elastic strain field can be present around the graphite particles in ductile cast iron after manufacturing, probably due to some local mismatch in thermal contraction. However, as only one component of the elastic strain tensor could be obtained from the XRD data, the shape and magnitude of the associated residual stress field have remained unknown. To compensate for this and to provide theoretical insight into this unexplored topic, a combined experimental-numerical approach is presented in this paper. First, a material equivalent to the ductile cast iron matrix is manufactured and subjected to dilatometric and high-temperature tensile tests. Subsequently, a two-scale hierarchical top-down model is devised, calibrated on the basis of the collected data and used to simulate the interaction between the graphite particles and the matrix during manufacturing of the industrial part considered in the XRD study. The model indicates that, besides the viscoplastic deformation of the matrix, the effect of the inelastic deformation of the graphite has to be considered to explain the magnitude of the XRD strain. Moreover, the model shows that the large elastic strain perturbations recorded with XRD close to the graphite–matrix interface are not artifacts due to e.g. sharp gradients in chemical composition, but correspond to residual stress concentrations induced by the conical sectors forming the internal structure of the graphite particles. In contrast to common belief, these results thus suggest that ductile cast iron parts cannot be considered, in general, as stress-free at the microstructural scale. 

  • 9.
    Appusamy Boopathy, Harish
    et al.
    Jönköping University, School of Engineering, JTH, Product Development. Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Bonthala, Pavan Kumar
    Jönköping University, School of Engineering, JTH, Product Development. Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Electrochemical etching and anodizing as key stages of surface treatment of aluminium foil for electrolytic capacitor industry: Application of Electro Chemical Impedance Spectroscopy as non-destructive characterization of etched anode foil with an anodized dielectric oxide layer2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the initial stage, the sample preparation was done by using the techniques of Anodic etching and anodic forming processes where a repeated trial and error method of sample preparation headed towards making out a suitable sample set for characterization. After this step, the set of 2 different industrial samples were introduced and anodic oxide forming process was carried out in different electrolytes.

     

     In the sample preparations, 4 different electrolytes were used 15% wt. Ammonium Adiphate, 1.5% wt. Ammonium Phosphate, 7% wt. Boric acid and 15% Penta Borate at different stages for performing the anodic oxide forming process. Minimum forming voltages of 20V to a maximum of 100V was employed in the sample preparation and to overcome the waiting time in forming the etched samples a higher current of 0.5A was used.

     

    After the samples preparation, Electrochemical Impedance spectroscopy was used as a tool for characterising the various groups of samples and for observing the micro structures of various samples, they were fractured and the observed on the cross section by SEM.

     

    After the analysis of the etched samples was made, an attempt to compare the results of the data of these samples to that of the 2 set of industrial samples was made and found that the resultant data wasn’t stable enough to characterize since huge scattering were occurring and whereby the simulation of the CPE circuit for the chosen circuit in the analysis was not possible.

     

    Under the analysis, a randomly chosen industrial sample was also used and the resultant data was utilised in understanding the response of the system to different electrolytes.

  • 10.
    Awe, Samuel A.
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Jarfors, Anders E. W.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Dahle, Arne
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Development of cast Al-Cu-Si ternary eutectic alloys for high temperature applications2016In: Proceedings and Abstracts Book of European Advanced Materials Congress, At Stockholm, Sweden / [ed] Ashutosh Tiwari, Linköping: VBRI Press , 2016Conference paper (Refereed)
  • 11.
    Awe, Samuel A.
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting. Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Jarfors, Anders E.W.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting. Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Lee, Young C.
    Dahle, Arne
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Development of new Al-Cu-Si alloys for high temperature performance2017In: Advanced Materials Letters, ISSN 0976-3961, E-ISSN 0976-397X, Vol. 8, no 6, p. 695-701Article in journal (Refereed)
    Abstract [en]

    In a quest to develop new light metal alloys that can perform excellently at elevated-temperatures (from 300°C to 400°C), a ternary eutectic Al-Cu-Si alloy was exploited to gain a deeper understanding of the alloy system and its suitability for high temperature applications. The alloys studied, with chemical composition of Al-27%Cu-5%Si (by weight percent) with Ni addition in the range of 0 to 1.5%wt, were cast in a rapid solidification casting technique. The solidification characteristics of the alloy was studied using the Thermo-Calc software. Microstructures were characterized in a scanning electron microscope coupled with energy dispersive spectrometry (SEM-EDS). Finally, the elevated-temperatures tensile properties of the alloys were investigated. Comparing the microstructures and mechanical properties of these Al-Cu-Si(-Ni) alloys with conventional Al-Si alloy A319, the refined microstructure with dispersed Ni intermetallic particles formed in the as-cast Al-Cu-Si(-Ni) alloys deliver improved elevated temperature properties. In particular, the yield strength and ultimate tensile strength of the new alloy with 1.5% Ni at 400?C were observed to be 220% and 309% higher, respectively, than for conventional A319 alloy.

  • 12.
    Beckius, Fredrik
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Jönköping University, School of Engineering, JTH, Product Development.
    Gustafsson, Robin
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Jönköping University, School of Engineering, JTH, Product Development.
    Connecting casting simulation and FE software including local variation of physical properties.: Investigation on local material properties and microstructure in a grey iron cylinder head.2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 13.
    Belov, Ilja
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing - Surface technology.
    Reliability study of GaN HEMTs2016Conference paper (Other academic)
  • 14.
    Belov, Ilja
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Alavizadeh, Zahra
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Lindgren, Mats
    Omnisys Instruments AB, Västra Frölunda, Sweden.
    Ryden, Jan
    Saab AB, Göteborg, Sweden.
    Leisner, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. RISE Research Institutes of Sweden, Borås, Sweden.
    Experimental and CFD evaluation of active anti-condensation methods for non-hermetic cabinets2018In: 19th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE, 2018, Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Experimental evaluation of several active anti-condensation methods for application in non-hermetic electronics enclosures was performed in harsh climatic conditions, including RH = 70% and T = 43 °C. The studied methods included blowing the air along the exposed surface, combination of blowing and air heating as well as local heating of the exposed surface in natural convection conditions. The purpose was to prevent/remove the dew on/from the exposed surface of a micro-condensation sensor. The difference between the methods was quantified in terms of time for dew removal. The power consumption aspects were discussed. A CFD based optimization methodology was developed to determine the heating profiles for the local anti-condensation PCB heater in a non-hermetic cabinet exposed to the quickly changing climatic conditions. The potential for 60% energy savings was revealed by simulation.

  • 15.
    Belov, Ilja
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Nordh, Andreas
    Salomonsson, Kent
    Jönköping University, School of Engineering, JTH, Product Development.
    Leisner, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Fin‐Tube and Plate Heat Exchangers: Evaluation of Transient Performance2017Conference paper (Refereed)
    Abstract [en]

    A methodology for evaluation of transient performance of, and comparison between plate heat exchanger and plate-fin-and-tube heat exchanger was developed and realized, including experiment and 3-D simulation. Heat transfer from water to a gas medium was addressed. The heated gas volume was the same for both heat exchanger designs. This was achieved by placing the plate-fin-and-tube heat exchanger into enclosure. The volume average temperature of the gas as function of time was computed. Estimated material cost for the studied designs was at least seven times lower than for the stainless steel plate heat exchanger. The performance of the selected plate-fin-and-tube heat exchanger design was found comparable to the plate heat exchanger, when both fin and tube materials were set to Al, and the enclosure was a light-weight thermal insulator. Transient behavior of the studied heat exchangers should be of interest for micro-grid applications, but also for thermal management in electronic cabinets and data centers.

  • 16.
    Belov, Vladimir
    et al.
    Ogarev Mordovia State University, Saransk, Russian Federation.
    Leisner, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. RISE, Swedish Research Institute, Safety and Transport/Electronics, Borås, Sweden.
    Mannikoff, Anders
    Herrljunga Elektriska AB, Herrljunga, Sweden.
    Belov, Ilja
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Mathematical Model of Multi-Phase Power Converter for Parallel Computation2018In: International Journal of Emerging Electric Power Systems, ISSN 2194-5756, E-ISSN 1553-779X, Vol. 19, no 1, article id 20170114Article in journal (Refereed)
    Abstract [en]

    A mathematical model of a multi-phase power conversion system composed of modified bridge-elements (B-system) capable for parallel computation has been developed. Experimental validation on the example of a power system including a synchronous generator and an AC-DC rectifier has been performed. A mathematical algorithm for B-system assembly and steps to obtain mathematical model of the B-system have been developed. Integration of mathematical models of conversion system into the complete model of a multi-phase power system has been explained and evaluation of computational efficiency of parallel computation techniques for the developed model of an AC-DC-AC converter has been performed. The presented modelling method can be employed in the design phase of smart grids, for power quality and conducted emission analysis. 

  • 17.
    Bhat, Abhishek Govind
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Thermodynamic apporach for reduction of solag amount and viscosity in CGI production process2018Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The work presented aims to reduce the amount and viscosity of the slag produced in the furnace during the production of Compacted Graphite Iron in SCANIA foundry and simulate the actual process using thermodynamic calculations to estimate the amount and the composition of the slag.

    The estimation of slag amount and slag compositions was done using CALPHAD (Calculation of Phase Diagram) method which can be done using the thermodynamic software Thermo-Calc using the composition of the raw materials and the phase diagrams calculation. In the present work, an appropriate calculation method to estimate the amount and composition of slag was established and based on the calculations, strategies to decrease the viscosity were suggested.

  • 18.
    Bjurenstedt, Anton
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting. Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    On the influence of imperfections on microstructure and properties of recycled Al-Si casting alloys2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    There are great energy savings to be made by recycling aluminium; as little as 5% of the energy needed for primary aluminium production may be required. Striving to produce high quality aluminium castings requires knowledge of microstructural imperfections, which is extra important when casting recycled aluminium that generally contains higher levels of imperfections compared to primary aluminium. Imperfections include amongst others Si, Fe, and Mn as well as oxides. Si is needed for castability, but it may also initiate fracture. There are different types of Fe-rich intermetallics influencing properties of castings, generally in a negative direction. Oxides constitute cracks and they are elusive because they are difficult to quantify.

    This thesis aims to increase knowledge about imperfections in recycled aluminium castings originating from alloying elements and the melt. Experiments were performed in advanced laboratory equipment, including X-radiographic imaging during solidification and in-situ tensile testing in a scanning electron microscope. Experiments were also performed at industrial foundry facilities.

    The experiments showed that the nucleation temperature of primary α-Fe intermetallics increased with higher Fe, Mn, and Cr contents. Primary α-Fe are strongly suggested to nucleate on oxides and to grow in four basic morphologies. Lower nucleation frequency of α-Fe promoted faster growth and hopper crystals while higher nucleation frequency promoted slower growth rates and massive crystals. Results also showed that a decrease in the size of the eutectic Si and plate-like β-Fe intermetallics improved tensile properties, foremost the elongation to fracture. In β-Fe containing alloys the transversely oriented intermetallics initiated macrocracks that are potential fracture initiation sites. In alloys with primary α-Fe foremost clusters of intermetallics promoted macrocracks. In fatigue testing, a transition from β-Fe to α-Fe shifted the initiation sites from oxides and pores to the α-Fe, resulting in a decrease of fatigue strength. Oxides in Al-Si alloys continue to be elusive; no correlations between efforts to quantify the oxides and tensile properties could be observed.

  • 19.
    Bjurenstedt, Anton
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Casari, Daniele
    Department of Physics, Norwegian University of Science and Technology, Trondheim, Norway.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Mathiesen, Ragnvald H.
    Department of Physics, Norwegian University of Science and Technology, Trondheim, Norway.
    Dahle, Arne K.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    In-situ study of morphology and growth of primary α-Al(FeMnCr)Si intermetallics in an Al-Si alloy2017In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 130, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Morphology and growth of primary α-Al(FeMnCr)Si intermetallics have been studied in-situ during solidification of a commercial secondary aluminum alloy employing X-radiographic imaging combined with deep-etching. The α-Al(FeMnCr)Si intermetallics were found to nucleate primarily on surface oxides, and the continued growth yielded both rhombic dodecahedrons and elongated rod-like morphologies. Both morphologies were observed as hopper and massive types, where the hopper intermetallics had the higher growth rates. The growth rate, which determines the type, appears to be linked to nucleation frequency; higher nucleation frequency promoted massive types and lower nucleation frequency promoted hopper intermetallics. 

  • 20.
    Bjurenstedt, Anton
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting. Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Ghassemali, Ehsan
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting. Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting. Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Dahle, Arne
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    The effect of Fe-rich intermetallics on crack initiation in cast aluminium: an in-situ tensile studyManuscript (preprint) (Other academic)
  • 21.
    Bogdanoff, Toni
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Development of aluminium-silicon alloys with improved properties at elevated temperature2017Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Aluminium-silicon alloys have gained increasing market share in the automotive and aerospace industry because of increased environmental demands. These alloys have a high strength-to-weight ratio, good corrosion resistance, castability and recycling potential. However, variations in properties and limited performance at elevated temperature are restricting these alloys from use at elevated temperatures. During the last decades, researchers have investigated ways to improve the properties at elevated temperatures. However, the effect of some transition elements is not well understood. The aim of this work is to investigate the aluminium-silicon alloys with addition of cobalt and nickel for high temperature applications. Tensile testing and hardness testing were conducted on samples produced by directional solidification in a Bridgman furnace with condition generating a microstructure corresponding to that obtained in high pressure die casting, i.e. SDAS ~ 10 µm. The results show that cobalt and nickel improve the tensile properties up to 230 °C.

  • 22.
    Bogdanoff, Toni
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Dahle, Arne K.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Effect of Co and Ni Addition on the Microstructure and Mechanical Properties at Room and Elevated Temperature of an Al–7%Si Alloy2018In: International Journal of metalcasting, ISSN 1939-5981, E-ISSN 2163-3193, Vol. 12, no 3, p. 434-440Article in journal (Refereed)
    Abstract [en]

    Increasing environmental demands are forcing the automotive industry to reduce vehicle emissions by producing more light-weight and fuel efficient vehicles. Al–Si alloys are commonly used in automotive applications because of excellent castability, high thermal conductivity, good wear properties and high strength-to-weight ratio. However, most of the aluminium alloys on the market exhibit significantly reduced strength at temperatures above 200 °C. This paper presents results of a study of the effects of Co and Ni in a hypoeutectic Al–Si alloy on microstructure and mechanical properties at room and elevated temperature. Tensile test specimens with microstructures comparable to those obtained in high-pressure die casting, i.e. SDAS ~ 10 µm, were produced by directional solidification in a Bridgman furnace. The results show an improvement in tensile properties up to 230 °C.

  • 23.
    Bogdanoff, Toni
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Dahle, Arne K.
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    The effect of SI content on microstructure and mechanical properties of Al-Si alloy2016In: La Metallurgia Italiana, ISSN 0026-0843, Vol. 108, no 6Article in journal (Refereed)
    Abstract [en]

    Al-Si alloys are the most popular casting alloys due to their excellent castability combined with high strengthto-weight ratio. This paper investigates the role of Si content in the range of 6.5 wt. % to 14.4 wt. % on the microstructure and mechanical properties of Al-Si-Mg casting alloys. All alloys were modified with 90-150 ppm Sr. No grain refiner was added. The samples were produced by directional solidification providing a microstructure that corresponds to microstructures found in die castings. From the phase diagram and coupled zone, increasing the Si level up to 14.4 wt. % is expected to start a competition between formation of α- dendrites and a fully eutectic microstructure. However, it is known that Sr-modification shifts the eutectic to higher Si contents. For the lower Si contents, the microstructure of the samples consisted of α-dendrites and a modified Al-Si eutectic. At 12.4 wt. % Si and above, a cellular eutectic microstructure was observed. No primary Si was observed even at 14.4 wt. % Si. The mechanical properties in terms of yield and tensile strength did not vary remarkably as a function of the Si level unlike the elongation to failure that dropped from 12 % at 6.5 wt. % Si to nearly 6 % at 14.4 wt. % Si; but still the material is exhibiting an elongation to failure that is far higher than normally expected.

  • 24.
    Burman, Erik
    et al.
    University College London, United Kingdom.
    Elfverson, Daniel
    Umeå universitet, Sweden.
    Hansbo, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Larson, Mats
    Umeå universitet, Sweden.
    Larsson, Karl
    Umeå universitet, Sweden.
    Shape optimization using the cut finite element method2018In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 328, p. 242-261Article in journal (Refereed)
    Abstract [en]

    We present a cut finite element method for shape optimization in the case of linear elasticity. The elastic domain is defined by a level-set function, and the evolution of the domain is obtained by moving the level-set along a velocity field using a transport equation. The velocity field is the largest decreasing direction of the shape derivative that satisfies a certain regularity requirement and the computation of the shape derivative is based on a volume formulation. Using the cut finite element method no re-meshing is required when updating the domain and we may also use higher order finite element approximations. To obtain a stable method, stabilization terms are added in the vicinity of the cut elements at the boundary, which provides control of the variation of the solution in the vicinity of the boundary. We implement and illustrate the performance of the method in the two-dimensional case, considering both triangular and quadrilateral meshes as well as finite element spaces of different order.

  • 25.
    Burman, Erik
    et al.
    Department of Mathematics, University College London, London, United Kingdom.
    Hansbo, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Stabilized nonconforming finite element methods for data assimilation in incompressible flows2018In: Mathematics of Computation, ISSN 0025-5718, E-ISSN 1088-6842, Vol. 87, no 311, p. 1029-1050Article in journal (Refereed)
    Abstract [en]

    We consider a stabilized nonconforming finite element method for data assimilation in incompressible flow subject to the Stokes equations. The method uses a primal dual structure that allows for the inclusion of nonstandard data. Error estimates are obtained that are optimal compared to the conditional stability of the ill-posed data assimilation problem.

  • 26.
    Burman, Erik
    et al.
    Department of Mathematics, University College London, London, United Kingdom.
    Hansbo, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Larson, Mats G.
    Department of Mathematics and Mathematical Statistics, Umeå University, Umeå, Sweden.
    A cut finite element method with boundary value correction2018In: Mathematics of Computation, ISSN 0025-5718, E-ISSN 1088-6842, Vol. 87, no 310, p. 633-657Article in journal (Refereed)
    Abstract [en]

    In this contribution we develop a cut finite element method with boundary value correction of the type originally proposed by Bramble, Dupont, and Thomée in [Math. Comp. 26 (1972), 869-879]. The cut finite element method is a fictitious domain method with Nitsche-type enforcement of Dirichlet conditions together with stabilization of the elements at the boundary which is stable and enjoy optimal order approximation properties. A computational difficulty is, however, the geometric computations related to quadrature on the cut elements which must be accurate enough to achieve higher order approximation. With boundary value correction we may use only a piecewise linear approximation of the boundary, which is very convenient in a cut finite element method, and still obtain optimal order convergence. The boundary value correction is a modified Nitsche formulation involving a Taylor expansion in the normal direction compensating for the approximation of the boundary. Key to the analysis is a consistent stabilization term which enables us to prove stability of the method and a priori error estimates with explicit dependence on the meshsize and distance between the exact and approximate boundary.

  • 27.
    Burman, Erik
    et al.
    Department of Mathematics, University College London, London, United Kingdom.
    Hansbo, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Larson, Mats G.
    Department of Mathematics and Mathematical Statistics, Umeå University, Sweden.
    A simple approach for finite element simulation of reinforced plates2018In: Finite elements in analysis and design (Print), ISSN 0168-874X, E-ISSN 1872-6925, Vol. 142, p. 51-60Article in journal (Refereed)
    Abstract [en]

    We present a new approach for adding Bernoulli beam reinforcements to Kirchhoff plates. The plate is discretised using a continuous/discontinuous finite element method based on standard continuous piecewise polynomial finite element spaces. The beams are discretised by the CutFEM technique of letting the basis functions of the plate represent also the beams which are allowed to pass through the plate elements. This allows for a fast and easy way of assessing where the plate should be supported, for instance, in an optimization loop.

  • 28.
    Burman, Erik
    et al.
    Department of Mathematics, University College London, London, United Kingdom.
    Hansbo, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Larson, Mats G.
    Department of Mathematics and Mathematical Statistics, Umeå University, Umeå, Sweden.
    A simple finite element method for elliptic bulk problems with embedded surfaces2019In: Computational Geosciences, ISSN 1420-0597, E-ISSN 1573-1499, Vol. 23, no 1, p. 189-199Article in journal (Refereed)
    Abstract [en]

    In this paper, we develop a simple finite element method for simulation of embedded layers of high permeability in a matrix of lower permeability using a basic model of Darcy flow in embedded cracks. The cracks are allowed to cut through the mesh in arbitrary fashion and we take the flow in the crack into account by superposition. The fact that we use continuous elements leads to suboptimal convergence due to the loss of regularity across the crack. We therefore refine the mesh in the vicinity of the crack in order to recover optimal order convergence in terms of the global mesh parameter. The proper degree of refinement is determined based on an a priori error estimate and can thus be performed before the actual finite element computation is started. Numerical examples showing this effect and confirming the theoretical results are provided. The approach is easy to implement and beneficial for rapid assessment of the effect of crack orientation and may for example be used in an optimization loop. 

  • 29.
    Burman, Erik
    et al.
    Department of Mathematics, University College London, United Kingdom.
    Hansbo, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Larson, Mats G.
    Department of Mathematics and Mathematical Statistics, Umeå University, Sweden.
    Augmented Lagrangian and Galerkin least-squares methods for membrane contact2018In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 114, no 11, p. 1179-1191Article in journal (Refereed)
    Abstract [en]

    In this paper, we propose a stabilized finite element method for the numerical solution of contact between a small deformation elastic membrane and a rigid obstacle. We limit ourselves to friction-free contact, but the formulation is readily extendable to more complex situations. 

  • 30.
    Burman, Erik
    et al.
    University College London, London, UK.
    Hansbo, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Larson, Mats G
    Umeå University, Umeå, Sweden.
    Solving ill-posed control problems by stabilized finite element methods: an alternative to Tikhonov regularization2018In: Inverse Problems, ISSN 0266-5611, E-ISSN 1361-6420, Vol. 34, no 3, article id 035004Article in journal (Refereed)
    Abstract [en]

    Tikhonov regularization is one of the most commonly used methods for the regularization of ill-posed problems. In the setting of finite element solutions of elliptic partial differential control problems, Tikhonov regularization amounts to adding suitably weighted least squares terms of the control variable, or derivatives thereof, to the Lagrangian determining the optimality system. In this note we show that the stabilization methods for discretely illposed problems developed in the setting of convection-dominated convection– diffusion problems, can be highly suitable for stabilizing optimal control problems, and that Tikhonov regularization will lead to less accurate discrete solutions. We consider some inverse problems for Poisson’s equation as an illustration and derive new error estimates both for the reconstruction of the solution from the measured data and reconstruction of the source term from the measured data. These estimates include both the effect of the discretization error and error in the measurements.

  • 31.
    Burman, Erik
    et al.
    Department of Mathematics, University College London, United Kingdom.
    Hansbo, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Larson, Mats G.
    Department of Mathematics and Mathematical Statistics, Umeå University, Sweden.
    Larsson, Karl
    Department of Mathematics and Mathematical Statistics, Umeå University, Sweden.
    Cut finite elements for convection in fractured domains2018In: Computers & Fluids, ISSN 0045-7930, E-ISSN 1879-0747Article in journal (Refereed)
    Abstract [en]

    We develop a cut finite element method (CutFEM) for the convection problem in a so called fractured domain, which is a union of manifolds of different dimensions such that a d dimensional component always resides on the boundary of a d+1 dimensional component. This type of domain can for instance be used to model porous media with embedded fractures that may intersect. The convection problem is formulated in a compact form suitable for analysis using natural abstract directional derivative and divergence operators. The cut finite element method is posed on a fixed background mesh that covers the domain and the manifolds are allowed to cut through a fixed background mesh in an arbitrary way. We consider a simple method based on continuous piecewise linear elements together with weak enforcement of the coupling conditions and stabilization. We prove a priori error estimates and present illustrating numerical examples.

  • 32.
    Burman, Erik
    et al.
    Department of Mathematics, University College London, London, United Kingdom.
    Hansbo, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Larson, Mats G.
    Department of Mathematics and Mathematical Statistics, Umeå University, Umeå, Sweden.
    Larsson, Karl
    Department of Mathematics and Mathematical Statistics, Umeå University, Umeå, Sweden.
    Massing, André
    Department of Mathematics and Mathematical Statistics, Umeå University, Umeå, Sweden.
    Finite element approximation of the Laplace–Beltrami operator on a surface with boundary2019In: Numerische Mathematik, ISSN 0029-599X, E-ISSN 0945-3245, Vol. 141, no 1, p. 141-172Article in journal (Refereed)
    Abstract [en]

    We develop a finite element method for the Laplace–Beltrami operator on a surface with boundary and nonhomogeneous Dirichlet boundary conditions. The method is based on a triangulation of the surface and the boundary conditions are enforced weakly using Nitsche’s method. We prove optimal order a priori error estimates for piecewise continuous polynomials of order (Formula presented.) in the energy and (Formula presented.) norms that take the approximation of the surface and the boundary into account. 

  • 33.
    Burman, Erik
    et al.
    Department of Mathematics, University College London, United Kingdom.
    Hansbo, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Larson, Mats G.
    Department of Mathematics and Mathematical Statistics, Umeå University, Sweden.
    Massing, André
    Department of Mathematics and Mathematical Statistics, Umeå University, Sweden.
    Cut finite element methods for partial differential equations on embedded manifolds of arbitrary codimensions2019In: Mathematical Modelling and Numerical Analysis, ISSN 0764-583X, E-ISSN 1290-3841, Vol. 52, no 6, p. 2247-2282Article in journal (Refereed)
    Abstract [en]

    We develop a theoretical framework for the analysis of stabilized cut finite element methods for the Laplace-Beltrami operator on a manifold embedded in Rd of arbitrary codimension. The method is based on using continuous piecewise linears on a background mesh in the embedding space for approximation together with a stabilizing form that ensures that the resulting problem is stable. The discrete manifold is represented using a triangulation which does not match the background mesh and does not need to be shape-regular, which includes level set descriptions of codimension one manifolds and the non-matching embedding of independently triangulated manifolds as special cases. We identify abstract key assumptions on the stabilizing form which allow us to prove a bound on the condition number of the stiffness matrix and optimal order a priori estimates. The key assumptions are verified for three different realizations of the stabilizing form including a novel stabilization approach based on penalizing the surface normal gradient on the background mesh. Finally, we present numerical results illustrating our results for a curve and a surface embedded in R3.

  • 34.
    Burman, Erik
    et al.
    Mathematics, University College London, London, United Kingdom.
    Hansbo, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Larson, Mats G.
    Mathematics and Mathematical Statistics, Umeå University, Umeå, Sweden.
    Samvin, David
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    A cut finite element method for elliptic bulk problems with embedded surfaces2019In: GEM - International Journal on Geomathematics, ISSN 1869-2672, E-ISSN 1869-2680, Vol. 10, no 1, article id 10Article in journal (Refereed)
    Abstract [en]

    We propose an unfitted finite element method for flow in fractured porous media. The coupling across the fracture uses a Nitsche type mortaring, allowing for an accurate representation of the jump in the normal component of the gradient of the discrete solution across the fracture. The flow field in the fracture is modelled simultaneously, using the average of traces of the bulk variables on the fractures. In particular the Laplace–Beltrami operator for the transport in the fracture is included using the average of the projection on the tangential plane of the fracture of the trace of the bulk gradient. Optimal order error estimates are proven under suitable regularity assumptions on the domain geometry. The extension to the case of bifurcating fractures is discussed. Finally the theory is illustrated by a series of numerical examples. 

  • 35.
    Burman, Erik
    et al.
    UCL, Department of Mathematics, London, United Kingdom.
    Hansbo, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Larson, Mats G.
    Umeå Universitet, Department of Mathematics and Mathematical Statistics, Umeå, Sweden.
    Zahedi, Sara
    The Royal Institute of Technology (KTH), Department of Mathematics, Stockholm, Sweden.
    Stabilized CutFEM for the convection problem on surfaces2019In: Numerische Mathematik, ISSN 0029-599X, E-ISSN 0945-3245, Vol. 141, no 1, p. 103-139Article in journal (Refereed)
    Abstract [en]

    We develop a stabilized cut finite element method for the convection problem on a surface based on continuous piecewise linear approximation and gradient jump stabilization terms. The discrete piecewise linear surface cuts through a background mesh consisting of tetrahedra in an arbitrary way and the finite element space consists of piecewise linear continuous functions defined on the background mesh. The variational form involves integrals on the surface and the gradient jump stabilization term is defined on the full faces of the tetrahedra. The stabilization term serves two purposes: first the method is stabilized and secondly the resulting linear system of equations is algebraically stable. We establish stability results that are analogous to the standard meshed flat case and prove h3 / 2 order convergence in the natural norm associated with the method and that the full gradient enjoys h3 / 4 order of convergence in L2. We also show that the condition number of the stiffness matrix is bounded by h- 2. Finally, our results are verified by numerical examples. 

  • 36.
    Burman, Erik N.
    et al.
    UCL, Department of Mathematics, London, United Kingdom.
    Hansbo, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Larson, Mats G.
    Umeå Universitet, Department of Mathematics and Mathematical Statistics, Umeå, Sweden.
    A cut finite element method with boundary value correction for the incompressible Stokes equations2019In: Numerical mathematics and advanced applications ENUMATH 2017, Cham: Springer, 2019, Vol. 126, p. 183-192Conference paper (Refereed)
    Abstract [en]

    We design a cut finite element method for the incompressible Stokes equations on domains with curved boundary. The cut finite element method allows for the domain boundary to cut through the elements of the computational mesh in a very general fashion. To further facilitate the implementation we propose to use a piecewise affine discrete domain even if the physical domain has curved boundary. Dirichlet boundary conditions are imposed using Nitsche’s method on the discrete boundary and the effect of the curved physical boundary is accounted for using the boundary value correction technique introduced for cut finite element methods in Burman et al. (Math Comput 87(310):633–657, 2018). 

  • 37.
    Burman, E.
    et al.
    University College London, London, United Kingdom.
    Elfverson, D.
    Umeå University, Umeå, Sweden.
    Hansbo, Peter
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Larson, M. G.
    Umeå University, Umeå, Sweden.
    Larsson, K.
    Umeå University, Umeå, Sweden.
    Cut topology optimization for linear elasticity with coupling to parametric nondesign domain regions2019In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 350, p. 462-479Article in journal (Refereed)
    Abstract [en]

    We develop a density based topology optimization method for linear elasticity based on the cut finite element method. More precisely, the design domain is discretized using cut finite elements which allow complicated geometry to be represented on a structured fixed background mesh. The geometry of the design domain is allowed to cut through the background mesh in an arbitrary way and certain stabilization terms are added in the vicinity of the cut boundary, which guarantee stability of the method. Furthermore, in addition to standard Dirichlet and Neumann conditions we consider interface conditions enabling coupling of the design domain to parts of the structure for which the design is already given. These given parts of the structure, called the nondesign domain regions, typically represent parts of the geometry provided by the designer. The nondesign domain regions may be discretized independently from the design domains using for example parametric meshed finite elements or isogeometric analysis. The interface and Dirichlet conditions are based on Nitsche's method and are stable for the full range of density parameters. In particular we obtain a traction-free Neumann condition in the limit when the density tends to zero. 

  • 38. Campbell, John
    et al.
    Svidró, József Tamás
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting. Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Svidró, Judit
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Molding and Casting Processes2017In: ASM Handbook, Volume 1A: Cast Iron Science and Technology / [ed] Doru M. Stefanescu, Materials Park, Ohio: ASM International, 2017, p. 189-206Chapter in book (Refereed)
  • 39.
    Ceschini, Lorella
    et al.
    Department of Industrial Engineering (DIN), Alma Mater Studiorum–University of Bologna, Bologna, Italy.
    Dahle, Arne
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Gupta, Manoj
    Department of Mechanical Engineering, National University of Singapore, Singapore.
    Jarfors, Anders E.W.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Jayalakshmi, S.
    Department of Mechanical Engineering, Bannari Amman Institute of Technology (BIT), Sathyamangalam, India.
    Morri, Alessandro
    Interdepartmental Center for Industrial Research-Advanced Mechanics and Materials (CIRI-MAM), Alma Mater Studiorum–University of Bologna, Bologna, Italy.
    Rotundo, Fabio
    Interdepartmental Center for Industrial Research-Advanced Mechanics and Materials (CIRI-MAM), Alma Mater Studiorum–University of Bologna, Bologna, Italy.
    Toschi, Stefania
    Department of Industrial Engineering (DIN), Alma Mater Studiorum–University of Bologna, Bologna, Italy.
    Singh, R. Arvind
    Department of Aeronautical Engineering, Bannari Amman Institute of Technology (BIT), Sathyamangalam, India.
    Aluminum and Magnesium Metal Matrix Nanocomposites2017Book (Other academic)
    Abstract [en]

    The book looks into the recent advances in the ex-situ production routes and properties of aluminum and magnesium based metal matrix nanocomposites (MMNCs), produced either by liquid or semi-solid state methods. It comprehensively summarizes work done in the last 10 years including the mechanical properties of different matrix/nanoreinforcement systems. The book also addresses future research direction, steps taken and missing developments to achieve the full industrial exploitation of such composites. The content of the book appeals to researchers and industrial practitioners in the area of materials development for metal matrix nanocomposites and its applications.

  • 40.
    Ceschini, Lorella
    et al.
    Department of Civil, Chemical, Environmental and Materials Engineering, University of Bologna, Italy.
    Morri, Alessandro
    Department of Industrial Engineering, University of Bologna, Italy.
    Toschi, Stefania
    Department of Industrial Engineering, University of Bologna, Italy.
    Bjurenstedt, Anton
    Swerea SWECAST, Jönköping, Sweden.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Influence of sludge particles on the fatigue behavior of Al-Si-Cu secondary aluminium casting alloys2018In: Metals, E-ISSN 2075-4701, Vol. 8, no 4, article id 268Article in journal (Refereed)
    Abstract [en]

    Al-Si-Cu alloys are the most widely used materials for high-pressure die casting processes. In such alloys, Fe content is generally high to avoid die soldering issues, but it is considered an impurity since it generates acicular intermetallics (β-Fe) which are detrimental to the mechanical behavior of the alloys. Mn and Cr may act as modifiers, leading to the formation of other Fe-bearing particles which are characterized by less harmful morphologies, and which tend to settle on the bottom of furnaces and crucibles (usually referred to as sludge). This work is aimed at evaluating the influence of sludge intermetallics on the fatigue behavior of A380 Al-Si-Cu alloy. Four alloys were produced by adding different Fe, Mn and Cr contents to A380 alloy; samples were remelted by directional solidification equipment to obtain a fixed secondary dendrite arm spacing (SDAS) value (~10 µm), then subjected to hot isostatic pressing (HIP). Rotating bending fatigue tests showed that, at room temperature, sludge particles play a detrimental role on fatigue behavior of T6 alloys, diminishing fatigue strength. At elevated temperatures (200◦C) and after overaging, the influence of sludge is less relevant, probably due to a softening of the α-Al matrix and a reduction of stress concentration related to Fe-bearing intermetallics.

  • 41.
    Ceschini, Lorella
    et al.
    University of Bologna, Italy.
    Morri, Alessandro
    University of Bologna, Italy.
    Toschi, Stefania
    University of Bologna, Italy.
    Boromei, Iuri
    University of Bologna, Italy.
    Bjurenstedt, Anton
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting. Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting. Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Al-Si-Cu alloys for high pressure die casting: Influence of Fe, Mn, and Cr on room temperaturemechanical properties2016In: La Metallurgia Italiana, ISSN 0026-0843, no 6, p. 77-80Article in journal (Refereed)
    Abstract [en]

    Al-Si-Cu alloys with high Fe content are widely employed in high pressure die casting (HPDC). Even if Feis usually considered an impurity in secondary aluminum alloys, leading to the formation of harmfulintermetallic compounds, it helps in mitigating or eliminating the problem of die soldering. As a result,secondary Al alloys with Fe content of about 1 wt% are commonly employed for the production of HPDCcastings. Aiming to change the morphology of harmful Fe-bearing phases towards less detrimentalmorphologies, proper alloying elements may be added to the alloys. Mn and Cr (both present in thealuminum scrap), as instance, are reported to prevent from the formation of the acicular β-Al5FeSi phase,leading to the formation of more compact and polygonal intermetallics. Such phases are usually referredto as “sludge” particles. The influence of sludge particles on mechanical properties of Al -Si-Cu castings isstill under investigation. The present work aims at evaluating the effect of impurities (Fe, Mn and Cr)typically present in secondary Al alloys on the microstructure and mechanical properties of the A380 (Al -Si-Cu) alloy. Samples with different Fe, Mn and Cr content were produced and processed through adirectional solidification equipment to obtain specimens with controlled SDAS (~10 μm). Hardness androtating bending fatigue tests were carried out at room temperature. Mechanical properties of the alloyswere then related to the microstructure, analyzed by optical and scanning electron microscopy.

  • 42.
    Ceschini, Lorella
    et al.
    University of Bologna, Italy.
    Morri, Alessandro
    University of Bologna, Italy.
    Toschi, Stefania
    University of Bologna, Italy.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Johansson, Sten
    Linköping University.
    Effect of microstructure and overaging on the tensile behaviour at room and elevated temperature of C355-T6 cast aluminum alloy2015In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 83, p. 626-634Article in journal (Refereed)
    Abstract [en]

    The present study was focused on the microstructural and mechanical characterization of the Al–Si–Cu–Mg C355 alloy, at room and elevated temperature. In order to evaluate the influence of microstructural coarseness on mechanical behavior, samples with different Secondary Dendrite Arm Spacing (SDAS) (20–25 μm for fine microstructure and 50–70 μm for coarse microstructure), were produced through controlled casting conditions. The tensile behavior of the alloy was evaluated at T6 condition and at T6 with subsequent high temperature exposure (41 h at 210 °C, i.e. overaging), both at room and elevated temperature (200 °C). Microstructural investigations were performed through optical and electron microscopy.

    The results confirmed the important role of microstructure on the tensile behavior of C355 alloy. Ultimate tensile strength and elongation to failure strongly increased with the decrease of SDAS. Larger SDAS, related to lower solidification rates, modify microstructural features, such as eutectic Si morphology and size of the intermetallic phases, which in turn influence elongation to failure. Overaging before tensile testing induced coarsening of the strengthening precipitates, as observed by STEM analyses, with consequent reduction of the tensile strength of the alloy, regardless of SDAS. A more sensible decrease of tensile properties was registered at 200 °C testing temperature.

  • 43.
    Ceschini, Lorella
    et al.
    University of Bologna.
    Morri, Alessandro
    University of Bologna.
    Toschi, Stefania
    University of Bologna.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Messieri, Simone
    Ducati Motor Holding .
    The influence of cooling rate on microstructure, tensile and fatigue behavior of heat treated Al-Si-Cu-Mg alloys2017In: Liquid metals and alloys: From structure to industrial applications / [ed] Lars Arnberg, Franco Bonollo and Roberto Montanari, Trans Tech Publications, 2017, p. 81-92Chapter in book (Refereed)
    Abstract [en]

    Al-Si-Mg alloys are commonly employed for the production of automotive castings. In view of the recent stringent emissions standards and consequent engine downsizing, these components must withstand higher temperatures and stresses than in the past. In this regard, the heat treatable quaternary Al-Si-Cu-Mg alloys gained particular interest in recent years, due to their superior mechanical properties and higher thermal stability. The present research activity was addressed to evaluate the influence of cooling rate on microstructure and consequently on room temperature tensile and fatigue behaviour of the A354 and C355 alloys. Samples for mechanical tests were produced under controlled cooling rates, in order to induce different secondary dendrite arm spacing (SDAS) values, classified as fine (20-25μm) and coarse (50-70μm). The experimental results showed that the cooling rate strongly influences the type, size and morphology of intermetallic particles. The presence of coarse intermetallic phases, mostly Fe-based, observed in coarse SDAS specimens, was reported to strongly affect ultimate tensile strength (UTS), elongation to failure and fatigue strength of both the investigated alloys. A correlation between UTS and fatigue resistance was found, independent of microstructural coarseness.

  • 44.
    Chernyakov, Anton E.
    et al.
    SHM R&E Center, RAS, St.Petersburg, Russia.
    Aladov, Andrey V.
    SHM R&E Center, RAS, St.Petersburg, Russia.
    Belov, Ilja
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Zakgeim, Alexander L.
    SHM R&E Center, RAS, St.Petersburg, Russia.
    Thermal resistance and temperature distribution in blue and white high-power LED arrays2017In: Proceedings of the 23rd International Workshop on Thermal Investigations of ICs and Systems (THERMINIC), 2017, IEEE, 2017, p. 1-4, article id Code 132094Conference paper (Refereed)
    Abstract [en]

    Thermal resistance and temperature distribution for high-power AlGaInN LED chip-on-board arrays in blue and white versions were measured by different methods and tools. The p-n junction temperature was determined through measuring a temperature-dependent forward voltage drop on the p-n junction, at a low measuring current after applying a high heating current. Furthermore, the infrared thermal imaging technique was employed to obtain the temperature map for the test object. A steady-state 3D computational model of the experimental setup was created including temperature-dependent power dissipation in the LED chips and partitioned interfacial thermal resistance between the heatsink and the LED array. Simulations of the heat transfer in the LED array were performed to further investigate temperature gradients observed in the measurements.

  • 45.
    Christina, Keller
    et al.
    Jönköping University, Jönköping International Business School, JIBS, Informatics.
    Wass, Sofie
    Jönköping University, Jönköping International Business School, JIBS, Informatics.
    Seifeddine, Salem
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Zetterlind, Madelene
    Jönköping University, School of Engineering, JTH, Industrial Engineering and Management.
    Jarfors, Anders
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Vomacka, Peter
    Hackås Precision Foundry.
    Structured knowledge transfer through online education: Mutual benefits for academia and industry2016Conference paper (Refereed)
    Abstract [en]

    Scientists are required to disseminate the results of research to the society and companies participating in research projects. The dissemination procedure normally consists of seminars, scientific and layman journal contributions, and conferences that generally are not flexible and timely enought to capture industrial needs. In an effort to accelerate knowledge transfer and technology implementation to sustain and improve competitiveness, Jönköping University has developed a one-year online master programme in cast metals and processes in collaboration with the industry. The collaboration includes development of the curriculum, case studies, lectures and study visits. To explore the development process, we performed interviews and a survey with participating students/professionals, teachers and industrial partners. Our results show that a profound two-way knowledge transfer took place, and that course content and teaching were highly relevant to the industry. Furthermore, industry and academia engaged in new joint research collaborations. Consequently, we hypothesize that the procedure for structured knowledge transfer can be implemented in materials education at advanced level to foster engagement between university, industry and society.

  • 46.
    Dini, Hoda
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    As-cast AZ91D magnesium alloy properties: Effects of microstructure and temperature2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Today, there is an essential need for lightweight, energy-efficient, environmentally benign engineering systems, and this is the driving force behind the development of a wide range of structural and functional materials for energy generation, energy storage, propulsion, and transportation. These challenges have motivated the use of magnesium alloys for lightweight structural systems. Magnesium has a density of 1.74 g/cm3, which is almost 30% less than that of aluminium, one quarter of steel, and almost identicalto polymers. The ease of recycling magnesium alloys as compared to polymers makes them environmentally attractive, but their poor mechanical performance is the primary reason for the limited adoption of these alloys for structural applications.

    The Mg-Al-Zn alloy AZ91D exhibits an excellent combination of strength, die-castability, and corrosion resistance. However, its mechanical performance with regard to creep strength, for example, at evaluated temperatures is poor. Moreover, very little is known about the correlation between its mechanical properties and microstructural features. This thesis aims to provide new knowledge regarding the role played by microstructure in the mechanical performance of the magnesium alloy. The properties/performance of the material in relation to process parameters became of great interest during the investigation.

    An exhaustive characterisation of the grain size, secondary dendrite arm spacing (SDAS) distribution, and fraction of Mg17Al12 was performed using optical and electron backscatter diffraction (EBSD). These microstructural parameters were correlated to the offset yield point (Rp0.2), fracture strength, and elongation to failure of the material. It was proposed that the intermetallic phase, Mg17Al12, plays an important role in determining the mechanical and physical properties of the alloy in a temperature range of room temperature to 190°C by forming a rigid network of intermetallic. The presence of this network was confirmed by studying the thermal expansion behaviour of samples of the alloy containing different amounts of Mg17Al12.

    A physically based constitutive model with a wide validity range was successfully adapted to describe the flow stress behaviour of AZ91D with various microstructures. The temperature-dependent variables of the model correlated quite well with the underlying physics of the material. The model was validated through comparison with dislocation densities obtained using EBSD.

    The influence of high-pressure die-cast parameters on the distortion and residual stress of the cast components was studied, as were distortion and residual stress in components after shot peening and painting. Interestingly, it was found that intensification pressure has a major effect on distortion and residual stresses, and that the temperature of the fixed half of the die had a slight influence on the component's distortion and residual stress.

  • 47.
    Dini, Hoda
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Andersson, Nils-Eric
    Jönköping University, School of Engineering, JTH, Mechanical Engineering.
    Jarfors, Anders E.W.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Effect of process parameters on distortion and residual stress in high pressure die cast AZ91D components after shot peening and paintingManuscript (preprint) (Other academic)
  • 48.
    Dini, Hoda
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Andersson, Nils-Eric
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Jarfors, Anders E.W.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Effect of process parameters on distortion and residual stress of high-pressure die-cast AZ91D components2018In: International Journal of metalcasting, ISSN 1939-5981, E-ISSN 2163-3193, Vol. 12, no 3, p. 487-497Article in journal (Refereed)
    Abstract [en]

    This paper presents a study of distortion and residual stress within a high-pressure die-cast AZ91D component, cast under different processing conditions. The influence of process parameters, i.e., die temperature, cooling time, intensification pressure and first-phase injection speeds, was examined. Distortions were measured using the in-house standard analog quality control fixture. Residual stress depth profiles were measured using a prism hole-drilling method. It was found that the most important process parameter affecting the distortion was intensification pressure and the second most important was temperature difference between the two die halves (fixed and moving side). Tensile residual stresses were found very near the surface. Increasing the intensification pressure resulted in an increased level of tensile residual stresses.

  • 49.
    Dini, Hoda
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Svoboda, A.
    Andersson, Nils-Eric
    Jönköping University, School of Engineering, JTH, Mechanical Engineering.
    Ghassemali, Ehsan
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Lindgren, L.
    Jarfors, Anders E.W.
    Jönköping University, School of Engineering, JTH, Mechanical Engineering.
    Modeling the Deformation Behavior of As-Cast AZ1D Including the Effect of The Cast Microstructure2017In: Proceedings of PLASTICITY ’17: The Twenty Third International Conference on Plasticity, Damage, and Fracture, 2017, p. 37-39Conference paper (Refereed)
  • 50.
    Dini, Hoda
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Svoboda, Ales
    Department of Materials and Manufacturing, School of Engineering, Jönköping University, Jönköping, Sweden.
    Andersson, Nils-Eric
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Ghassemali, Ehsan
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Lindgren, Lars-Erik
    Division of Mechanics of Solid Materials, Luleå University of Technology, Luleå, Sweden.
    Jarfors, Anders E.W.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Optimization and validation of a dislocation density based constitutive model for as-cast Mg-9%Al-1%Zn2018In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 710, p. 17-26Article in journal (Refereed)
    Abstract [en]

    A dislocation density-based constitutive model, including effects of microstructure scale and temperature, was calibrated to predict flow stress of an as-cast AZ91D (Mg-9%Al-1%Zn) alloy. Tensile stress-strain data, for strain rates from 10-4 up to 10-1 s-1 and temperatures from room temperature up to 190 °C were used for model calibration. The used model accounts for the interaction of various microstructure features with dislocations and thereby on the plastic properties. It was shown that the Secondary Dendrite Arm Spacing (SDAS) size was appropriate as an initial characteristic microstructural scale input to the model. However, as strain increased the influence of subcells size and total dislocation density dominated the flow stress. The calibrated temperature-dependent parameters were validated through a correlation between microstructure and the physics of the deforming alloy. The model was validated by comparison with dislocation density obtained by using Electron Backscattered Diffraction (EBSD) technique.

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