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  • 51.
    Vynnycky, Michael
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Saleem, Saud
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    An asymptotic approach to solidification shrinkage-induced macrosegregation in the continuous casting of binary alloys2018Inngår i: Applied Mathematical Modelling, ISSN 0307-904X, E-ISSN 1872-8480, Vol. 54, s. 605-626Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The modelling of macrosegregation in the continuous casting of alloys normally requires resource-intensive computational fluid dynamics (CFD). By contrast, here we develop an asymptotic framework for the case when macrosegregation is driven by solidification shrinkage; as a first step, a binary alloy is considered. Systematic asymptotic analysis of the steady-state two-dimensional mass, momentum, heat and solute conservation equations in terms of the shrinkage parameter indicates that the overall problem can be reduced to a hierarchy of decoupled problems: a leading-order problem that is non-linear, and a sequence of linear problems, with the actual macrosegregation of the solute then being determined by means of one-dimensional quadrature. A numerical method that solves this sequence is then developed and implemented, and yields realistic macrosegregation profiles at low computational cost.

  • 52.
    Vynnycky, Michael
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Saleem, Saud
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Towards an asymptotic framework for solidification shrinkage-induced macrosegregation in the continuous casting of binary alloysManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    The modelling of macrosegregation in the continuous casting of alloysnormally requires resource-intensive computational fluid dynamics(CFD). By contrast, here we develop an asymptotic framework for thecase when macrosegregation is driven by solidification shrinkage; as a firststep, a binary alloy is considered. Systematic asymptotic analysis of thesteady-state two-dimensional mass, momentum, heat and solute conservationequations in terms of the shrinkage parameter indicates that theoverall problem can be reduced to a hierarchy of decoupled problems: aleading-order problem that is non-linear, and a sequence of linear problems,with the actual macrosegregation of the solute then being determinedby means of one-dimensional quadrature.

  • 53.
    Vynnycky, Michael
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Zambrano, M.
    Univ Sao Paulo Sao Carlos, Inst Math & Comp Sci, Dept Appl Math & Stat, POB 668, BR-13560970 Sao Carlos, SP, Brazil..
    Towards a "moving-point" formulation for the modelling of oscillation-mark formation in the continuous casting of steel2018Inngår i: Applied Mathematical Modelling, ISSN 0307-904X, E-ISSN 1872-8480, Vol. 63, s. 243-265Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the continuous casting of steel, solidification begins at a triple point where solid steel, molten steel and molten flux meet; the motion of this point determines how surface defects known as oscillation marks (OSMs) are formed. Here, under a number of simplifying assumptions, we derive an asymptotic model in 15 dimensionless parameters that describes the relevant momentum and heat transfer for the process, and involves both surface tension at the meniscus between molten flux and molten steel and solidification; further development couples an earlier lubrication-theory model for the region below the triple point to a reduced model for the region above that is based around a regular perturbation treatment of the Navier Stokes equations in terms of the capillary number. The resulting problem is then broken up into a hierarchy of four sub-problems; the first one for the velocity field in the molten flux-is considered in depth. A numerical algorithm is developed for an isothermal situation in which the triple point moves only perpendicular to the casting direction; this involves the solution of a novel "moving point" problem to determine motion of the triple point. Comparison of model and experimental results indicates that this reduced model could produce OSMs having the observed depth if the triple point were not too far below the top of the meniscus; otherwise, the computed marks would be too deep. The analysis also tentatively relates the location of the triple point to the fold- and overflow-type OSMs that generally form in practice.

  • 54.
    Vynnycky, Michael
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Zambrano, M.
    Cuminato, J. A.
    On the avoidance of ripple marks on cast metal surfaces2015Inngår i: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 86, s. 43-54Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A mathematical model is derived for the purposes of predicting how to avoid unwanted defects, known as ripple marks, in the casting of metal ingots; the model is based around the momentum and heat transfer that occurs when a cooling molten metal meniscus rises between two parallel and vertical chill-mould walls. By using asymptotic techniques, the model is reduced systematically to a form that requires the numerical solution of a moving boundary problem involving just one partial differential equation. Numerical results are presented, and the significance of the model for predicting the depth and spacing of ripple marks in the casting of ingots and oscillation marks in continuous casting are discussed.

  • 55.
    Åberg, Jonas
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Vynnycky, Michael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Modelling of Thermal Stresses in Industrial Continuous Casting Processes2005Inngår i: Proceedings of the Femlab Conference, Stockholm, 2005Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper reports on progress in the implementationof COMSOL Multiphysics 3.2 to model thermalstresses in a three-dimensional solidifying shell, asoccurs typically in the industrial continuous casting ofcopper, copper alloys and steel. Computer memory requirementsprohibit a direct 3D numerical simulation ofthe temperature and the stresses. Instead, we use the factthat casting geometries are usually slender to divide thecalculation into three steps that are each less memoryintensive:(i) heat transfer and solidification is simulatedusing an arbitrary Lagrangian-Eulerian model; (ii) thetemperature solution is used to solve the force equilibriumequations in generalised plane strain mode appropriatefor a moving body; (iii) this solution is used tocompute the accumulated stress and strain in the body.Comparison between an analytical solution and a numericalsolution, that requires the simultaneous use ofseveral of Comsol Multiphysics’ peripheral features, ispresented.

  • 56.
    Åberg, Jonas
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Vynnycky, Michael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Nassar, Hani
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Bergström, Thomas
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    An on-site experimental heat flux study and its interpretation in a FEMLAB finite element simulation of continuous casting of copper in the South-Wire process2005Inngår i: Transactions of the Indian Institute of Metals, ISSN 0019-493X, Vol. 58, nr 4, s. 509-515Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The South-Wire process, a development of the Properzi process, to continuously cast copper has been studied both experimentally and by finite element computer simulation. The experimental work has been performed on site to get temperature data as a function of time at several locations within the mould. These experimental data have been used to evaluate boundary conditions for the heat transfer from the strand-mould interface and through the mould. A simulation model of the casting process has been developed in the program FEMLAB. In this program temperature varying material data and time varying boundary conditions have been used. The simulation model has been verified by comparing with an analytical solution, and then applied to the real physical process.

  • 57.
    Åberg, Jonas
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Vynnycky, Michael
    KTH, Skolan för teknikvetenskap (SCI), Centra, FaxénLaboratoriet.
    Widell, Björn
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Development of a finite element model for study of the developing stress and strain in a solidifying shell2006Rapport (Annet vitenskapelig)
12 51 - 57 of 57
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