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  • 1.
    Almroth, Per
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Solid Mechanics . Linköping University, The Institute of Technology.
    Hasselqvist, M.
    Demag Delaval Indust. Turbomach. AB, Finspång.
    Simonsson, Kjell
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Solid Mechanics .
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics . Linköping University, The Institute of Technology.
    Viscoplastic-plastic modelling of IN7922004In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 29, no 4, p. 437-445Article in journal (Refereed)
    Abstract [en]

    At high temperatures metallic materials behave in a viscous manner exemplified by strain rate dependence, stress relaxation and creep deformation. At low temperatures however, these effects are extremely small, and the behaviour is strain rate independent and shows no or very small relaxation effects. Finally there exists an intermediate region, in which the material behaviour is close to strain rate independent for high strain rates but at the same time shows time dependent inelastic effects, such as stress relaxation and creep. For IN792 this occurs at temperatures around 650 °C. The article describes the extension of a power-law viscoplastic model describing the behaviour of IN792 at 850 °C, also to describe the behaviour at 650 °C, by bounding the elastic-viscoplastic stress-space by a plastic yield surface. The model parameters have been estimated using data from creep test and tailored step relaxation tests, and the model fits well to both the step relaxation data aimed at resembling relevant component conditions and long term creep data. © 2003 Published by Elsevier B.V.

  • 2.
    Almroth, Per
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Solid Mechanics.
    Hasselqvist, Magnus
    Sjöström, Karl Henning Sören
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering.
    Simonsson, Kjell
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Solid Mechanics.
    Modeling of the high temperature behaviour of IN792 in gas turbine hot parts2002In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 25, no 3, p. 305-315Article in journal (Other academic)
    Abstract [en]

    The material parameters for two isothermal viscoplastic models with deliberately limited sets of material parameters have been estimated. The models are to describe the behaviour of the nickel based superalloy IN792 in a gas turbine hot part application. The models are based on a power law flow equation and the state variable used is backstress. The model calibration is done by least-squares optimization using non-standard constitutive tests that are aimed at describing relevant component conditions. The constitutive tests give information about the kinematic hardening effects for the backstress evolution equations, while secondary creep data provides stress versus inelastic strain rate information for the flow equation. All tests are uniaxial and isothermal. With the estimated parameter sets the models give relatively good fits to the data. The results suggest that the models can be used to describe the high temperature behaviour of IN792. ⌐ 2002 Elsevier Science B.V. All rights reserved.

  • 3.
    Brodin, Håkan
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Eriksson, Robert
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Johansson, Sten
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Fracture Mechanical Modelling of a Plasma Sprayed TBC System2009In: Advanced Ceramic Coatings and Interfaces IV / [ed] Dongming Zhu and Hua-Tay Lin, Westerville, OH, United States: American Ceramic Society Inc. , 2009, Vol. 30, no 3, p. 113-124Conference paper (Refereed)
    Abstract [en]

    A thermal barrier coating (TBC) system subjected to thermal cycling will develop a microcrack partem near the interface between the metallic bond coat and the ceramic top coat. These small cracks link up and form internal TBC delaminations during repeated heating / cooling. After a longer time period, the internal delamination cracks will form a larger spallation damage, where the TBC is detached from the underlying material. Since cracks are initiated in multiple sites of the thermal barrier coating, the damage is initially considered to be governed by local stress conditions. The purpose of the present work is to compare experimental data with predictions of a physically based fatigue life model. The present study has been performed on plasma-sprayed TBCs where the interface geometry has been varied. In the present work, calculation of fatigue life is done for a number of cases under thermal fatigue loading. Different interface geometries are compared in order to understand the influence of variations in the TC/BC interface roughness on oxidation behaviour and thermal fatigue life. Thermal fatigue tests indicate that an increased surface roughness is beneficial from a fatigue life point of view.

  • 4.
    Brodin, Håkan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials.
    Eriksson, Robert
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång.
    Östergren, Lars
    Volvo Aero Corporation, Trollhättan.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Solid Mechanics.
    Finite Element Modelling and Damage Evaluation of Air Plasma Sprayed Thermal Barrier Coatings2012Conference paper (Refereed)
  • 5.
    Brodin, Håkan
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials . Linköping University, The Institute of Technology.
    Li, Xin-Hai
    Siemens Industrial Turbomchinery AB.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics . Linköping University, The Institute of Technology.
    Influence on thermal barrier coating delamination behaviour of edge geometry2006Conference paper (Refereed)
  • 6.
    Brodin, Håkan
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Damage development in two thermal barrier coating systems2009In: ICF12,2009, 2009Conference paper (Other academic)
    Abstract [en]

          

  • 7.
    Eriksson, Robert
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Solid Mechanics.
    Brodin, Håkan
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Östergren, Lars
    GKN Aerospace Engine Systems, Trollhättan.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång.
    Influence of Interface Roughness on the Fatigue Life of Thermal Barrier Coatings2013Conference paper (Refereed)
  • 8.
    Eriksson, Robert
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Brodin, Håkan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Östergren, Lars
    GKN Aerospace Engine Systems, Trollhättan, Sweden.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    TBC bond coat-top coat interface roughness: influence on fatigue life and modelling aspects2013In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 236, p. 230-238Article in journal (Refereed)
    Abstract [en]

    Thermal barrier coatings (TBCs), when used in gas turbines, may fail through thermal fatigue, causing the ceramic top coat to spall off the metallic bond coat. The life prediction of TBCs often involves finite element modelling of the stress field close to the bond coat/top coat interface and thus relies on accurate modelling of the interface. The present research studies the influence of bond coat/top coat interface roughness on the thermal fatigue life of plasma sprayed TBCs. By using different spraying parameters, specimens with varying interface roughness were obtained. During thermal cycling it was found that higher interface roughness promoted longer thermal fatigue life. The interfaces were characterised by roughness parameters, such as Ra, Rq and Rq, as well as by autocorrelation, material ratio curves, probability plots and slope distribution. The variation of spray parameters was found to affect amplitude parameters, such as Ra, but not spacing parameters, such as RSm. Three different interface geometries were tried for finite element crack growth simulation: cosine, ellipse and triangular shape. The cosine model was found to be an appropriate interface model and a procedure for obtaining the necessary parameters, amplitude and wavelength, was suggested. The positive effect of high roughness on life was suggested to be due to a shift from predominantly interface failure, for low roughness, to predominantly top coat failure, for high roughness.

  • 9.
    Ganghoffer, J. F.
    et al.
    Ecole des Mines, Nancy.
    Gautier, E.
    Ecole des Mines, Nancy.
    Denis, S.
    Ecole des Mines, Nancy.
    Simon, A.
    Ecole des Mines, Nancy.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics . Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics . Linköping University, The Institute of Technology.
    Micromechanical simulation of a martensitic transformation by Finite Elements1991In: Journal de Physique IV: Colloque, ISSN 1155-4339, E-ISSN 1764-7177, Vol. 1, p. C4-77-C4-82Article in journal (Refereed)
    Abstract [en]

    A micromechanical model describing the martensitic transformation on the grain scale has been developed, using Finite Elements. First results gained from the simulation illustrate how the morphological evolution within the grain is directly controlled by the internal stress state. The reversible and irreversible part of transformation "plasticity" strain and their evolution with the transformation can then be obtained from these calculations.

  • 10.
    Ganghoffer, J.F.
    et al.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Denis, S.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Gautier, E.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Simon, A.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics . Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics . Linköping University, The Institute of Technology.
    Mechanical and thermodynamical study of a macroscopically coherent phase transition: Case of the martensitic transformation1991In: Journal de Physique IV: Colloque, ISSN 1155-4339, E-ISSN 1764-7177, Vol. 1, p. C4-89-C4-94Article in journal (Refereed)
    Abstract [en]

    In the general framework of a macroscopically coherent phase transition, the mechanical and thermodynamical behaviour of a two-phase volume element under structural evolution will be investigated and discussed. The identification of internal entropy production will then allow to formulate a general evolution condition for such a system and the internal stress state will appear to influence strongly the transformation behaviour, via the interface. The case of a martensitic transformation is considered. From that rigourous mechanical approach, we obtain the thermodynamical balance equation used for martensitic transformation.

  • 11.
    Ganghoffer, J.F.
    et al.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Denis, S.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Gautier, E.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Simon, A.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Mechanical and thermodynamical study of a macroscopically coherent phase transition.Case of the martensitic transformation1991In: Journal de Physique IV, ISSN 1155-4339, Vol. 1, p. C4-89-C4-94Article in journal (Refereed)
    Abstract [en]

    In the general framework of a macroscopically coherent phase transition, the mechanical and thermodynamical behaviour of a two-phase volume element under structural evolution will be investigated and discussed. The identification of internal entropy production will then allow to formulate a general evolution condition for such a system and the internal stress state will appear to influence strongly the transformation behaviour, via the interface. The case of a martensitic transformation is considered. From that rigourous mechanical approach, we obtain the thermodynamical balance equation used for martensitic transformation.

  • 12.
    Ganghoffer, J.F.
    et al.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Denis, S.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Gautier, E.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Simon, A.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Micromechanical simulation of a martensitic transformaation by Finite Elements1991In: Journal de Physique IV, ISSN 1155-4339, Vol. 1, p. C4-77-C4-82Article in journal (Refereed)
    Abstract [en]

    A micromechanical model describing the martensitic transformation on the grain scale has been developed, using Finite Elements. First results gained from the simulation illustrate how the morphological evolution within the grain is directly controlled by the internal stress state. The reversible and irreversible part of transformation "plasticity" strain and their evolution with the transformation can then be obtained from these calculations.

  • 13.
    Ganghoffer, J.F.
    et al.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Denis, S.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Gautier, E.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Simon, A.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Micromechanical simulation of martensitic transformation by Finite Elements1991In: Journal de Physique IV, ISSN 1155-4339, Vol. 1, p. C4-77-C4-82Article in journal (Refereed)
    Abstract [en]

    A micromechanical model describing the martensitic transformation on the grain scale has been developed, using Finite Elements. First results gained from the simulation illustrate how the morphological evolution within the grain is directly controlled by the internal stress state. The reversible and irreversible part of transformation "plasticity" strain and their evolution with the transformation can then be obtained from these calculations.

  • 14.
    Ganghoffer, J.F.
    et al.
    Laboratoire de Science et Génie des Matériaux Métalliques, UA 159 du CNRS, Ecole des Mines, Parc de Saurupt, 54042 Nancy cedex, France.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Denis, S.
    Laboratoire de Science et Génie des Matériaux Métalliques, UA 159 du CNRS, Ecole des Mines, Parc de Saurupt, 54042 Nancy cedex, France.
    Gautier, E.
    Laboratoire de Science et Génie des Matériaux Métalliques, UA 159 du CNRS, Ecole des Mines, Parc de Saurupt, 54042 Nancy cedex, France.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Simon, A.
    Laboratoire de Science et Génie des Matériaux Métalliques, UA 159 du CNRS, Ecole des Mines, Parc de Saurupt, 54042 Nancy cedex, France.
    Martensitic transformation plasticity simulations by Finite Elements1994In: Journal de Physique IV, ISSN 1155-4339, Vol. 4, p. C3-215-C3-220Article in journal (Refereed)
    Abstract [en]

    The mechanical behaviour associated to the martensitic transformation has been modelled using a 2D FE description. The martensite variants are constituted of different elements of the mesh and four different variants are allowed to transform in the grain. The transformation progress is prescribed using a thermodynamical criterion based on the maximal work associated to the variant formation. Transformation plasticity deformation and plates orientation patterns are obtained for three stress levels. These results are discussed in regard to the model used and the physical parameters introduced in the model.

  • 15.
    Ganghoffer, J.F.
    et al.
    Ecole des Mines, Nancy.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics . Linköping University, The Institute of Technology.
    Denis, S.
    Ecole des Mines, Nancy.
    Gautier, E.
    Ecole des Mines, Nancy.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics . Linköping University, The Institute of Technology.
    Simon, A.
    Ecole des Mines, Nancy.
    Martensitic transformation plasticity simulations by finite elements1994In: Journal de Physique IV: Colloque, ISSN 1155-4339, E-ISSN 1764-7177, Vol. 4, p. C3-215-C3-220Article in journal (Refereed)
    Abstract [en]

    The mechanical behaviour associated to the martensitic transformation has been modelled using a 2D FE description. The martensite variants are constituted of different elements of the mesh and four different variants are allowed to transform in the grain. The transformation progress is prescribed using a thermodynamical criterion based on the maximal work associated to the variant formation. Transformation plasticity deformation and plates orientation patterns are obtained for three stress levels. These results are discussed in regard to the model used and the physical parameters introduced in the model.

  • 16.
    Gustafsson, David
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Hornqvist, Magnus
    Volvo Aero Corporation.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Sharifimajd, Babak
    Siemens Industrial Turbomachinery AB.
    Fatigue crack growth behaviour of Inconel 718 with high temperature hold times2010In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 2, no 1, p. 1095-1104Article in journal (Refereed)
    Abstract [en]

    In this work, fatigue crack growth measurements have been made on center-cracked tension specimens of Inconel 718, where the focus has been to observe the effect of high temperature hold times on the fatigue crack growth behaviour of the material. The material testing has been done at three different temperatures, namely 450 degrees C, 550 degrees C and 650 degrees C. All testing were done in an isothermal LCF context with a standard test method for measuring the fatigue crack growth rates.

  • 17.
    Gustafsson, David
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Hornqvist, M
    Volvo Aero Corp.
    Mansson, T
    Volvo Aero Corp.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Influence of high temperature hold times on the fatigue crack propagation in Inconel 7182011In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 33, no 11, p. 1461-1469Article in journal (Refereed)
    Abstract [en]

    High temperature fatigue crack growth in Inconel 718 has been studied at the temperatures 450 degrees C, 500 degrees C, 550 degrees C and 650 degrees C. The tests were conducted both without hold times and with hold times of different lengths and with a mix of both. Focus has been on quantifying the effect the hold time has upon the crack growth rate and how much it damages the material. Furthermore, it has been investigated how this damage influences the actual cracking behavior, i.e. where in the loading cycle the damage contributes most to the crack growth. This damage is related to the concept of a damaged zone in front of the crack tip. The size of the damaged zone has been derived from the tests and a microscopy study to confirm the findings has also been carried out. It is found that the concept of a damaged zone can be a successful explanatory model for the observed crack growth behavior under high temperature hold time.

  • 18.
    Gustafsson, David
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Simonsson, Kjell
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Solid Mechanics.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Hörnqvist, Magnus
    Volvo Aero Corporation, Trollhättan.
    Månsson, Tomas
    Volvo Aero Corporation, Trollhättan.
    Sjöström, Sören
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Solid Mechanics.
    Fatigue Crack Growth behaviour of Inconel 718 - the Concept of a Damaged Zone Caused by High Temperature Hold Times2011In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 10, p. 2821-2826Article in journal (Refereed)
    Abstract [en]

    Fatigue crack growth testing of Inconel 718 has been carried out at the temperatures 550 °C and 650 °C. The tests were conducted using a mix of hold times and pure cyclic loading, referred to as block tests. From the test results, the existence of an embrittled volume or damaged zone in the vicinity of the crack tip has been revealed. It has been found that the evolution of this damaged zone can be sufficiently well described using a power law function with an exponent n = 0.25.

  • 19.
    Gustafsson, David
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Modeling of the Constitutive Behavior of Inconel 718 at Intermediate Temperatures2011In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 133, p. 094501-1-094501-4Article in journal (Refereed)
    Abstract [en]

    Turbine disks are of large importance to turbine designers as theyare exposed to hot environment and subjected to high loads. Inorder to analyze such components with respect to fatigue crackinitiation, the work generally starts with a rigorous analysis of thefirst few cycles, during which an important stress redistributionwill always take place in an inelastic structure. In this work, thenonlinear kinematic hardening law by Ohno and Wang (1998,“Constitutive Modeling of Cyclic Plasticity With Emphasis onRatchetting,” Int. J. Mech. Sci., 40, pp. 251–261) has been used incombination with an isotropic softening law for describing theinitial stress-strain distribution for strain controlled uniaxial testsof the material Inconel 718. Focus has been placed on finding asimple model with few material parameters and to describe theinitial softening and the comparatively small mean stress relaxationobserved during the material testing. The simulation resultsobtained by using the model fit the experimental resultswell.

  • 20.
    Jinnestrand, Magnus
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Solid Mechanics.
    Sjöström, Karl Henning Sören
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering.
    Stress state in thermal barrier coatings from 3D finite element simulations2001In: Int. Congress on theoretical and Applied Mechanics,2001, 2001Conference paper (Other academic)
    Abstract [en]

       

  • 21.
    Jinnestrand, Magnus
    et al.
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology.
    Investigation by 3D FE simulations of delamination crack initiation in TBC caused by alumina growth2001In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 135, no 2-3, p. 188-195Article in journal (Refereed)
    Abstract [en]

    In gas turbines, thermal barrier coatings (TBCs) applied by air plasma spraying are widely used to reduce the temperature in hot components. The TBC allows higher gas temperature and/or reduces the need for internal cooling in the hot components, thus increasing the efficiency of the gas turbine. Spallation is a common failure mechanism of TBC and occurs after a critical number of thermal cycles, when the alumina layer has grown to a critical thickness. The influence of the growing alumina layer and the top/bond-coat interface roughness in the TBC has been investigated. The primary goal was to identify failure mechanisms that can be incorporated into a life model of the TBC, and to increase the understanding of the delamination process in the TBC. A new formulation of alumina growth is proposed, in which the swelling strains caused by the volumetric increase during alumina growth depends on the stress state. The alumina growth model is used in 3D FE thermal cycling simulations of a TBC in which the thermal cycle time is long enough to characterize a typical cycle of a gas turbine. From the simulations, the growing alumina layer is observed to be one failure mechanism of the TBC. Without an alumina layer in the model, high delamination stress is observed at room temperature, above ridges of the top/bond-coat interface in the top coat. When the alumina is growing, the point of maximum delamination stress is moved towards the valleys. When the thickness of the alumina layer has grown to approximately 8–10 μm, positive delamination stress is found above the valleys in the top coat. The movement of the positive delamination stress region can explain why a delamination crack develops, which will cause spallation of the TBC during shutdown to room temperature.

  • 22.
    Leidermark, Daniel
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Moverare, Johan J.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Room temperature yield behaviour of a single-crystal nickel-base superalloy with tension/compression asymmetry2009In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 47, no 2, p. 366-372Article in journal (Refereed)
    Abstract [en]

    The constitutive behaviour at room temperature of a single-crystal nickel-base superalloy is presented in a new model. This model is based on crystal plasticity and takes Schmid- as well as non-Schmid stresses, elastic anisotropy and tension/compression asymmetry into account. By comparison with uniaxial tensile and compressive tests, the model is shown to reproduce the real behaviour well, including the tension/compression asymmetry. The model also shows that typically encountered deviations in orientations ofcastings have a non-negligible influence on stiffness and yield limit, which must be taken into account for industrial applications.

  • 23.
    Leidermark, Daniel
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Tension/Compression asymmetry of a single-crystal superalloy in virgin and degraded condition2010In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 58, no 15, p. 4986-4997Article in journal (Refereed)
    Abstract [en]

    The mechanical behaviour at room temperature of a single-crystal superalloy exposed to long term ageing at elevated temperature has been investigated, a topic important for the material’s resistance to thermal-mechanical fatigue. Specimens with several different crystallographic orientations were plastically deformed in either tension or compression before and after the long term furnace exposure. While the thermally activated degradation of the microstructure causes a reduction in yield limit of up to 25% for specimens initially deformed in the |001 and |011| directions, none or only moderate reduction was seen for specimens initially deformed along the |111| direction. This can be explained by the strong correlation between yield limit reduction and the amount of γ coarsening. By introducing an isotropic degradation function in a newly developed crystal plasticity model, the constitutive behaviour of both virgin and degraded materials has been described with good agreement with the experimental results.

  • 24.
    Leidermark, Daniel
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Segersäll, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Evaluation of Fatigue Crack Initiation in a Notched Single-crystal Superalloy Component2011In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 10, p. 619-624Article in journal (Refereed)
    Abstract [en]

    The fatigue crack initiation in a notched single-crystal nickel-base superalloy component at 500 °C was investigated and analysed. A critical plane approach in combination with a critical distance method has been adopted, in which the total shear strain ranges on the discrete slip planes are evaluated. Furthermore, a Coffin-Manson type of expression is used to predict the number of cycles to fatigue crack initiation. The experimental test specimens were studied by microscopy to determine on which crystallographic plane the fatigue initiation occurred. A good correlation between the experimental results and the simulated results were found.

  • 25.
    Leidermark, Daniel
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology. Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    A combined critical plane and critical distance approach for predicting fatigue crack initiation in notched single-crystal superalloy components2011In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 33, no 10, p. 1351-1359Article in journal (Refereed)
    Abstract [en]

    The fatigue crack initiation in notched single-crystal components of material MD2 is investigated and analysed. A critical plane approach in combination with a critical distance method has been adopted, in which the total shear strain ranges on the discrete crystallographic slip planes are evaluated. To determine the critical distance two approaches were evaluated, a mean value approach and a cycle dependent approach. Furthermore, a Coffin-Manson type of expression (derived from the results of a set of 12 smooth specimens) is used to predict the number of cycles to fatigue crack initiation. The numerical procedure is applied to a series of experiments, in which notched single-crystal components were exposed to uniaxial cyclic loading in the nominal [001] crystal direction at 500 degrees C with R(epsilon) = 0. A good correlation between the experimental results and the simulated results was found.

  • 26.
    Leidermark, Daniel
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Fatigue crack initiation in a notched single-crystal superalloy component2010In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 2, no 1, p. 1067-1075Article in journal (Refereed)
    Abstract [en]

    In this paper, the fatigue crack initiation in notched single-crystal test specimens of material MD2 is investigated and analysed. A critical plane approach is adopted, in which the total strain ranges on the discrete slip planes are evaluated. Furthermore, a Coffin-Manson type of expression is used to describe the number of cycles to fatigue crack initiation. This relation is determined from a set of smooth test specimens loaded uniaxially in the [001], [011] and directions at 500 °C with Rε=−1. The numerical procedure is then applied to a series of experiments, in which notched single-crystal test specimens were exposed to uniaxial cyclic loading in the [001] direction at 500 °C with Rε=0.

  • 27.
    Sadrossadat, Mohsen
    et al.
    Linköping University, Department of Management and Engineering. Linköping University, The Institute of Technology.
    Brodin, Håkan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Johansson, Sten
    Linköping University, Department of Management and Engineering. Linköping University, The Institute of Technology.
    Experimental realization and finite element simulation of residual stresses in Al-Si water sprayed cast componentsManuscript (preprint) (Other academic)
    Abstract [en]

    In this study, experiments were carried out to develop insights into  and understanding of the residual stresses that can arise during different thermal treatments of Al-Si components. The study consisted of two steps: experimental measurement of the residual stresses accumulated in the components and simulation of the results by finite element analysis. A special cooling apparatus was designed and built in order to perform selective cooling of the component. In the simulation step, the tensile behavior and parameters such as Young’s modulus values determined by tensile tests at different temperatures and the recorded cooling curves in the first step were used as input for the Abaqus software. The experimental results obtained by thermal analysis and residual stress measurement showed that by choosing a specific holding temperature before quenching, the value of residual stress increases linearly with flow rate of water spray coolant. On the other hand, for a constant value of cooling water flow rate, the maximum temperature difference between the middle and side bars of the test specimen (ΔTmax) and residual stress level decrease when the value of starting temperature of cooling decreases. It was shown that the strain gage method and thermal analysis are reliable techniques for measuring thermal residual stresses and prediction of residual strains in Al-Si components, respectively. It was also shown that the results obtained by simulation are reasonably in acceptable agreement with the experimentally measurements.

  • 28.
    Simonsson, Kjell
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Solid Mechanics .
    Sjöström, Sören
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Solid Mechanics .
    Mesomechanical modelling of the constitutive behaviour of a material during a martensitic transformation1999In: IUTAM Symposium on Micro- and Macrostructural Aspects of Thermoplasticity,1999, Boston: Kluwer , 1999, p. 345-Conference paper (Refereed)
    Abstract [en]

      

  • 29.
    Simonsson, Kjell
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Micromechanical modelling of the constitutive behaviour of a material during a martensitic transformation2002In: IUTAM Symposium on Micro- and Macrostructural Aspects of Thermoplasticity: Proceedings of the IUTAM Symposium held in Bochum, Germany, 25–29 August 1997, 2002, Vol. 62, p. 345-354Conference paper (Refereed)
  • 30.
    Sjöström, Sören
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Brodin, Håkan
    Siemens Industrial Turbomachinery, FINSPÅNG.
    Influence of TBC end geometry on the TMF life of an APS TBC2010In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 2, p. 1363-1371Article in journal (Refereed)
    Abstract [en]

    A TBC subjected to TMF loading may spall off after a sufficiently large number of cycles. This is a consequence of a combination of general fatigue damage growth and strong internal stresses caused by oxidation in the bondcoat/topcoat interface. Further, at the ends of the coating there are stress singularities, at which early fatigue cracks tend to develop. This can, however, be avoided or delayed by making the coating end chamfered. This work investigates the influence of coating end chamfer on the fatigue life of an APS TBC.

  • 31.
    Sjöström, Sören
    et al.
    Siemens Industrial Turbomachinery AB, FINSPÅNG, Sweden.
    Brodin, Håkan
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Thermomechanical fatigue life of TBCs - experimental and modelling aspects: 2010In: Advanced Ceramic Coatings and Interfaces V: Ceramic Engineering and Science Proceedings, Volume 31 / [ed] Zhu D, Lin H-T, Westerville, OH, United States: American Ceramic Society Inc. , 2010, Vol. 31, p. 23-39Conference paper (Refereed)
    Abstract [en]

    The fatigue life of APS TBC under TMF loading has been studied. Failure can be by spallation from convex surfaces, spallation from flat or nearly flat surfaces and spallation from sharp edges. The damage evolution leading to final failure has been studied experimentally, and based on the experimental observations, a fracture-mechanical model for the formation and growth of cracks in or near the thermally grown oxide and for the final failure of the TBC has been set up.

  • 32.
    Sjöström, Sören
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Solid Mechanics.
    Brodin, Håkan
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials.
    Jinnestrand, Magnus
    Siemens Industrial Turbomachinery AB, Finspång.
    Thermomechaical Fatigue Life of a TBC - Comparison of Computed and Measured Behaviour of Delamination Cracks2013Conference paper (Refereed)
  • 33.
    Sjöström, Sören
    et al.
    ALSTOM Power Sweden, Finspång.
    Burman, Jörgen
    Luleå University of Technology.
    Jinnestrand, Magnus
    Linköping University, Department of Management and Engineering, Solid Mechanics . Linköping University, The Institute of Technology.
    Lifetime prediction on gas turbine components with thermal barrier coatings, using micromechanics2002In: International Journal of Applied Mechanics and Engineering, ISSN 1425-1655, Vol. 7, no 1, p. 205-220Article in journal (Refereed)
  • 34.
    Storgärds, Erik
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Saarimäki, Jonas
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Gustafsson, David
    Siemens Ind Turbomachinery, Sweden.
    Mansson, Tomas
    GKN Aerosp Engine Syst, Sweden.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    SCATTER IN DWELL TIME CRACKING FOR A NI-BASED SUPERALLOY IN COMBINATION WITH OVERLOADS2015In: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2015, VOL 7A, ASME Press, 2015, no V07AT28A004Conference paper (Refereed)
    Abstract [en]

    In this paper scatter in crack growth for dwell time loadings combination with overloads has been investigated. Multiple Jsts were performed for surface cracks at 5500C in the commonly sed high temperature material Inconel 718. The test specimens -iginate from two different batches which also provides for a disission of how material properties affect the dwell time damage rnd overload impact. In combination with these tests an investiation of the microstructure was also carried out, which shows 9w it influences the growth rate. The results from this study show tat, in order to take overloads into consideration when analysing,ectrum loadings containing dwell times, one needs a substantial mount of material data available as the scatter seen from one atch to the other is of significant proportions.

  • 35.
    Storgärds, Erik
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Saarimäki, Jonas
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Gustafsson, David
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Månsson, Tomas
    GKN Aerospace Engine Systems, Trollhättan, Sweden.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Scatter in Dwell Time Cracking for a Ni-Based Superalloy in Combination With Overloads2016In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 138, no 1, p. 012502-012502Article in journal (Refereed)
    Abstract [en]

    In this paper, scatter in crack growth for dwell time loadings in combination with overloads has been investigated. Multiple tests were performed for surface cracks at 550 °C in the commonly used high temperature material Inconel 718. The test specimens originate from two different batches which also provide for a discussion of how material properties affect the dwell time damage and overload impact. In combination with these tests, an investigation of the microstructure was also carried out, which shows how it influences the growth rate. The results from this study show that, in order to take overloads into consideration when analyzing spectrum loadings containing dwell times, one needs a substantial amount of material data available as the scatter seen from one batch to the other are of significant proportions.

  • 36.
    Storgärds, Erik
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Saarimäki, Jonas
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Månsson, Tomas
    GKN Aerospace Engine Systems, Trollhättan, Sweden.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Impact of high cycle fatigue on dwell time crack growth in a Ni-based superalloy2015Manuscript (preprint) (Other academic)
    Abstract [en]

    Sustained load have been shown to give rise to increased crack growth rate at elevated temperature. Such loads generate a history dependent fatigue problem due to weakening and cracking of grain boundaries during dwell times, later broken apart during subsequent load cycles. So far most studies have focused on sustained load and the interaction of load cycles, overloads, and temperature, but few studies have been carried out for vibrations and how these affect the dwell time crack growth. Vibrations of different kinds are frequently seen in engine components, and present in combination with sustained loads a more realistic loading situation than the latter itself. An investigation of how a vibrational load affects the dwell time cracking and how to incorporate it in a modelling context is therefore of importance. In this paper a study of the most frequently used gas turbine material, Inconel 718, has been carried out. Mechanical testing has been conducted at 550◦C for surface cracks with and without the interaction of engine vibrations on sustained load, here represented by a superimposed high cycle fatigue (HCF) load. Subsequent investigation of the fracture behaviour was performed by Scanning Electron Microscope (SEM) and the modelling work has been conducted by incorporating the HCF load description within a history dependent crack growth law. The obtained results show reasonable accuracy with respect to the mechanical tests.

  • 37.
    Storgärds, Erik
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Saarimäki, Jonas
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Månsson, Tomas
    GDN Aerospace Engine Systems, Trollhättan.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Influence of Superimposed Vibrational Load on Dwell Time Crack Growth in a Ni-Based Superalloy2016In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 87, p. 301-310Article in journal (Refereed)
    Abstract [en]

    Sustained loads have for some Ni-based superalloys been shown to give rise to increased crack growth rate at elevated temperature. Such loads generate a history dependent fatigue problem due to weakening and cracking of grain boundaries during dwell times, later broken apart during subsequent load cycles. So far most studies have focused on the interaction of load cycles, overloads, and temperature. However, vibrations of different kinds are to some extent always present in engine components, and an investigation of how such loads affect the dwell time cracking, and how to incorporate them in a modelling context, is therefore of importance. In this paper a study of the most frequently used gas turbine material, Inconel 718, has been carried out. Mechanical crack propagation testing has been conducted at 550 °C for surface cracks with and without the interaction of superimposed vibrational loads. Subsequent investigation of the fracture behaviour was performed by scanning electron microscopy and the modelling work has been conducted by incorporating the vibration load description within a history dependent crack growth law. The obtained results show reasonable accuracy with respect to the mechanical test results.

  • 38.
    Storgärds, Erik
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Three-dimensional crack growth modelling of a Ni-based superalloy at elevated temperature and sustained loading2016In: Theoretical and applied fracture mechanics (Print), ISSN 0167-8442, E-ISSN 1872-7638Article in journal (Refereed)
    Abstract [en]

    High temperature materials subjected to elevated temperature have been shown to be sensitive to dwell times, giving an increased crack growth rate. The interaction between these dwell times and rapid cyclic loads have been shown to constitute a complex problem. Many models have been developed for 1D conditions, but the application to general 3D conditions has seldom been seen, although this is the most common case in most structures. In this paper a model for taking care of the interaction between these load modes in general 3D crack growth has been developed. The model uses 1D results for extension to general 3D, thus providing for local crack front evolution with a minimum of numerical simulations. The model has been implemented for usage with finite element calculations and several different tests are simulated and compared with experimental results for the nickel based superalloy Inconel 718 at 550◦C. The simulation results show crack shapes in agreement with experimental fracture surfaces and time to failure.

  • 39.
    Storgärds, Erik
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Gustafsson, David
    Siemens Ind Turbomachinery AB, Sweden.
    Mansson, Tomas
    GKN Aerosp Engine Syst, Sweden.
    MODELLING OF CRACK GROWTH WITH DWELL TIME FOR AERO ENGINE SPECTRA LOADINGS IN A NI-BASED SUPERALLOY2015In: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2015, VOL 7A, ASME Press, 2015, no V07AT28A003Conference paper (Refereed)
    Abstract [en]

    Testing and simulation of aero engine spectra with dwell Imes are reported in this paper. The modelling concept used built on LEFM and provides a history dependent evolution 2scription of dwell damage and its interaction with cyclic load. he simulations have been carried out for three spectra, 1) cyclic ?ads, 2) combined sustained load and cyclic loads and 3) slow ad ramps and cyclic loads, all for surface cracks at 550 C for nconel 718. All simulations show reasonable good agreement ith experimental results. Prediction of multiple tests of several atches is also provided to show statistical scatter

  • 40.
    Storgärds, Erik
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Gustafsson, David
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Månsson, Tomas
    GKN Aerospace Engine Systems, Trollhättan, Sweden.
    Modeling of Crack Growth With Dwell Time for Aero-engine Spectra Loadings in a Ni-Based Superalloy2016In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 138, no 1, p. 012501-012501Article in journal (Refereed)
    Abstract [en]

    Testing and simulation of aero-engine spectra with dwell times are reported in this paper. The modeling concept used is built on linear elastic fracture mechanics (LEFM) and provides a history-dependent evolution description of dwell damage and its interaction with cyclic load. The simulations have been carried out for three spectra: (1) cyclic loads, (2) combined sustained load and cyclic loads, and (3) slow load ramps and cyclic loads, all for surface cracks at 550 °C for Inconel 718. All simulations show reasonable good agreement with experimental results. Prediction of multiple tests of several batches is also provided to show statistical scatter.

  • 41.
    Storgärds, Erik
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Thermomechanical Fatigue Crack Growth Modeling in a Ni-Based Superalloy Subjected to Sustained Load2016In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 138, no 1, p. 012503-012503Article in journal (Refereed)
    Abstract [en]

    Thermomechanical fatigue (TMF) crack growth modeling has been conducted on Inconel 718 with dwell time at maximum load. A history dependent damage model taking dwell damage into account, developed under isothermal conditions, has been extended for TMF conditions. Parameter determination for the model is carried out on isothermal load controlled tests at 550–650 °C for surface cracks, which later have been used to extrapolate parameters used for TMF crack growth. Further, validation of the developed model is conducted on a notched specimen subjected to strain control at 50–550 °C. Satisfying results are gained within reasonable scatter level compared for test and simulated number of cycles to failure.

  • 42.
    Storgärds, Erik
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    THERMO-MECHANICAL FATIGUE CRACK GROWTH MODELLING IN A NI-BASED SUPERALLOY SUBJECTED TO SUSTAINED LOAD2015In: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2015, VOL 7A, ASME Press, 2015, no V07AT28A006Conference paper (Refereed)
    Abstract [en]

    Thermo-mechanical fatigue (TMF) crack growth modelling as been conducted on Inconel 718 with dwell time at maximum;ad. A history dependent damage model taking dwell damage uto account, developed under isothermal conditions, has been xtended for TMF conditions. Parameter determination for the lodel is carried out on isothermal load controlled tests at 55050 C for surface cracks, which later have been used to extrapole parameters used for TMF crack growth. Further, validation the developed model is conducted on a notched specimen sub?cted to strain control at 50-550 C. Satisfying results are gained ithin reasonable scatter level compared for test and simulated umber of cycles to failure.

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