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  • 1.
    Alimadadi, Majid
    et al.
    Department of Natural Sciences, Mid Sweden University, Sweden.
    Lindström, Stefan B
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Kulachenko, Artem
    Department of Solid Mechanics, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Role of microstructures in the compression response of three-dimensional foam-formed wood fiber networks2018Ingår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 14, s. 8945-8955Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High-porosity, three-dimensional wood fiber networks made by foam forming present experimentally accessible instances of hierarchically structured, athermal fiber networks. We investigate the large deformation compression behavior of these networks using fiber-resolved finite element analyses to elucidate the role of microstructures in the mechanical response to compression. Three-dimensional network structures are acquired using micro-computed tomography and subsequent skeletonization into a Euclidean graph representation. By using a fitting procedure to the geometrical graph data, weare able to identify nine independent statistical parameters needed for the regeneration of artificial networks with the observed statistics. The compression response of these artificially generated networks and the physical network is then investigated using implicit finite element analysis. A direct comparison of the simulation results from the reconstructed and artificial network reveals remarkable differences already in the elastic region. These can neither be fully explained by density scaling, the size effect nor the boundary conditions. The only factor which provides the consistent explanation of the observed difference is the density and fiber orientation nonuniformities; these contribute to strain-localization so that the network becomes more compliant than expected for statistically uniform microstructures. We also demonstrate that the experimentally manifested strain-stiffening of such networks is due to development of new inter-fiber contacts during compression.

  • 2.
    Alm Grundström, Henrik
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Developments in Topology Optimization in the ADDMAN Project2018Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This document gives an account of some of the work done so far on topology optimization (TO) in the ADDMAN project. As well as the mathematical formulations and implementations details, short discussions are presented on some of the nuances of the different formulations and how they should be used efficiently

  • 3.
    Alm Grundström, Henrik
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära.
    Topology Optimization for Additive Manufacturing Considering Stress and Anisotropy2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Additive manufacturing (AM) is a particularly useful manufacturing method for components designed using topology optimization (TO) since it allows for a greater part complexity than any traditional manufacturing method. However, the AM process potentially leads to anisotropic material properties due to the layer-by-layer buildup of parts and the fast and directional cooling. For Ti6Al4V tensile specimens built using electron beam melting (EBM), it has been observed that flat built specimens show superior strength and elastic moduli compared to top built specimens. Designs with the loading direction parallel to the build layers are therefore expected to show greater reliability.

    In this thesis a procedure is developed to optimize the AM build orientation considering anisotropic elastic material properties. A transversely isotropic material model is used to represent the in-plane and out-of-plane characteristics of AM produced parts. Two additional design variables are added to the TO formulation in order to control the orientation of the material using a coordinate transformation. Sensitivity analysis for the material direction variables is conducted for compliance as well as maximum von-Mises stress using a -norm stress aggregation function.

    The procedures for the AM build orientation optimization and stress constraints are implemented in the finite element software TRINITAS and evaluated using a number of examples in 2D and 3D. It is found that the procedure works well for compliance as well as stress but that a combination of these may lead to convergence issues due to contradicting optimal material orientations. An evaluation of the -norm stress aggregation function showed that a single global stress measure in combination with a stress correction procedure works well for most problems given that the mesh is refined enough to resolve the stresses accurately.  

  • 4.
    Alm Grundström, Henrik
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Trinitas Topology Optimization Tutorial Document2018Rapport (Övrigt vetenskapligt)
  • 5.
    Andersson, Håkan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    A Co-Simulation Approach for Hydraulic Percussion Units2018Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This Licentiate of Engineering thesis concerns modelling and simulation of hydraulic percussion units. These units are often found in equipment for breaking or drilling in rock and concrete, and are also often driven by oil hydraulics, in which complex fluid-structure couplings are essential for their operation.

    Current methodologies used today when developing hydraulic percussion units are based on decoupled analyses, which are not correctly capturing the important coupled mechanisms. Hence, an efficient method for coupled simulations is of high importance, since these mechanisms are critical for the function of these units. Therefore, a co-simulation approach between a 1D system simulation model representing the fluid system and a structural 3D FE-model is proposed.

    This approach is presented in detail, implemented for two well-known simulation tools and evaluated for a simple but relevant model. The Hopsan simulation tool was used for the fluid system and the FE-simulation software LS-DYNA was used for the structural mechanics simulation. The co-simulation interface was implemented using the Functional Mock-up Interface-standard.

    The approach was further developed to also incorporate multiple components for coupled simulations. This was considered necessary when models for the real application are to be developed. The use of two components for co-simulation was successfully evaluated for two models, one using the simple rigid body representation, and a second where linear elastic representations of the structural material were implemented.

    An experimental validation of the co-simulation approach applied to an existing hydraulic hammer was performed. Experiments on the hydraulic hammer were performed using an in-house test rig, and responses were registered at four different running conditions. The co-simulation model was developed using the same approach as before. The corresponding running conditions were simulated and the responses were successfully validated against the experiments. A parameter study was also performed involving two design parameters with the objective to evaluate the effects of a parameter change.

    This thesis consists of two parts, where Part I gives an introduction to the application, the simulation method and the implementation, while Part II consists of three papers from this project.

    Delarbeten
    1. A co-simulation method for system-level simulation of fluid-structure couplings in hydraulic percussion units
    Öppna denna publikation i ny flik eller fönster >>A co-simulation method for system-level simulation of fluid-structure couplings in hydraulic percussion units
    Visa övriga...
    2017 (Engelska)Ingår i: Engineering with Computers, ISSN 0177-0667, E-ISSN 1435-5663, Vol. 33, nr 2, s. 317-333Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    This paper addresses a co-simulation method for fluid power driven machinery equipment, i.e. oil hydraulic machinery. In these types of machinery, the fluid-structure interaction affects the end-product performance to a large extent, hence an efficient co-simulation method is of high importance. The proposed method is based on a 1D system model representing the fluid components of the hydraulic machinery, within which structural 3D Finite Element (FE) models can be incorporated for detailed simulation of specific sub-models or complete structural assemblies. This means that the fluid system simulation will get a more accurate structural response, and that the structural simulation will get more correct fluid loads at every time step, compared to decoupled analysis. Global system parameters such as fluid flow, performance and efficiency can be evaluated from the 1D system model simulation results. From the 3D FE-models, it is possible to evaluate displacements, stresses and strains to be used in stress analysis, fatigue evaluation, acoustic analysis, etc. The method has been implemented using two well-known simulation tools for fluid power system simulations and FE-simulations, respectively, where the interface between the tools is realised by use of the Functional Mock-up Interface standard. A simple but relevant model is used to validate the method.

    Ort, förlag, år, upplaga, sidor
    SPRINGER, 2017
    Nyckelord
    Co-simulation; Fluid-structure coupling; System simulation; Functional mock-up interface; Fluid power machinery; Transmission line modelling
    Nationell ämneskategori
    Datorsystem
    Identifikatorer
    urn:nbn:se:liu:diva-136875 (URN)10.1007/s00366-016-0476-8 (DOI)000398468100012 ()
    Anmärkning

    Funding Agencies|Atlas Copco Construction Tools

    Tillgänglig från: 2017-04-30 Skapad: 2017-04-30 Senast uppdaterad: 2018-09-11
    2. System level co-simulation of a control valve and hydraulic cylinder circuit in a hydraulic percussion unit
    Öppna denna publikation i ny flik eller fönster >>System level co-simulation of a control valve and hydraulic cylinder circuit in a hydraulic percussion unit
    Visa övriga...
    2017 (Engelska)Ingår i: Proceedings of 15:th Scandinavian International Conference on Fluid Power, June 7-9, 2017, Linköping, Sweden / [ed] Petter Krus, Liselott Ericson and Magnus Sethson, Linköping: Linköping University Electronic Press, 2017, Vol. 144, s. 225-235Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    In this study a previously developed co-simulation method that is based on a 1D system model representing the fluid components of a hydraulic machinery, within which structural 3D Finite Element (FE) models can be incorporated for detailed simulation of specific sub-models or complete structural assemblies, is further developed. The fluid system model consists of ordinary differential equation sub-models that are computationally very inexpensive, but still represents the fluid dynamics very well. The co-simulation method has been shown to work very well for a simple model representing a hydraulic driven machinery. A more complex model was set up in this work, in which two cylinders in the hydraulic circuit were evaluated. Such type of models, including both the main piston and control valves, are necessary as they represent the real application to a further extent than the simple model, of only one cylinder. Two models have been developed and evaluated, from the simple rigid body representation of the structural mechanics model, to the more complex model using linear elastic representation. The 3D FE-model facilitates evaluation of displacements, stresses, and strains on a local level of the model. The results can be utilised for fatigue assessment, wear analysis and for predictions of noise radiation.

    Ort, förlag, år, upplaga, sidor
    Linköping: Linköping University Electronic Press, 2017
    Serie
    Linköping Electronic Conference Proceedings, ISSN 1650-3686, E-ISSN 1650-3740 ; 144
    Nyckelord
    Co-simulation, Fluid-structure coupling, System simulation, Functional mockup interface, Fluid power machinery, Transmission line modelling
    Nationell ämneskategori
    Teknisk mekanik Farkostteknik Reglerteknik
    Identifikatorer
    urn:nbn:se:liu:diva-151015 (URN)10.3384/ecp17144225 (DOI)9789176853696 (ISBN)
    Konferens
    15th Scandinavian International Conference on Fluid Power, June 7-9, 2017, Linköping, Sweden
    Tillgänglig från: 2018-09-11 Skapad: 2018-09-11 Senast uppdaterad: 2018-09-11Bibliografiskt granskad
  • 6.
    Andersson, Håkan
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling. Linköpings universitet, Tekniska fakulteten. Construct Tools PC AB, Sweden.
    Nordin, Peter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling. Linköpings universitet, Tekniska fakulteten.
    Borrvall, Thomas
    DYNAmore Nordic AB, Brigadgatan 5, S-58758 Linkoping, Sweden.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Hilding, Daniel
    DYNAmore Nordic AB, Brigadgatan 5, S-58758 Linkoping, Sweden.
    Schill, Mikael
    DYNAmore Nordic AB, Brigadgatan 5, S-58758 Linkoping, Sweden.
    Krus, Petter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    A co-simulation method for system-level simulation of fluid-structure couplings in hydraulic percussion units2017Ingår i: Engineering with Computers, ISSN 0177-0667, E-ISSN 1435-5663, Vol. 33, nr 2, s. 317-333Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper addresses a co-simulation method for fluid power driven machinery equipment, i.e. oil hydraulic machinery. In these types of machinery, the fluid-structure interaction affects the end-product performance to a large extent, hence an efficient co-simulation method is of high importance. The proposed method is based on a 1D system model representing the fluid components of the hydraulic machinery, within which structural 3D Finite Element (FE) models can be incorporated for detailed simulation of specific sub-models or complete structural assemblies. This means that the fluid system simulation will get a more accurate structural response, and that the structural simulation will get more correct fluid loads at every time step, compared to decoupled analysis. Global system parameters such as fluid flow, performance and efficiency can be evaluated from the 1D system model simulation results. From the 3D FE-models, it is possible to evaluate displacements, stresses and strains to be used in stress analysis, fatigue evaluation, acoustic analysis, etc. The method has been implemented using two well-known simulation tools for fluid power system simulations and FE-simulations, respectively, where the interface between the tools is realised by use of the Functional Mock-up Interface standard. A simple but relevant model is used to validate the method.

  • 7.
    Andersson, Håkan
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten. Epiroc, Sweden.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Hilding, D.
    Dynamore Nord AB, Brigadgatan 5, S-58758 Linkoping, Sweden.
    Schill, M.
    Dynamore Nord AB, Brigadgatan 5, S-58758 Linkoping, Sweden.
    Sigfridsson, E.
    Epiroc, Sweden.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Validation of a co-simulation approach for hydraulic percussion units applied to a hydraulic hammer2019Ingår i: Advances in Engineering Software, ISSN 0965-9978, E-ISSN 1873-5339, Vol. 131, s. 102-115Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, a previously developed co-simulation approach has been adopted to simulate the responses of an existing hydraulic hammer product. This approach is based on a 1D system model representing the fluid components and a 3D finite element model representing the structural parts of the hydraulic hammer. The simulation model was validated against four experiments with different running conditions. The corresponding set-ups were analysed using the co-simulation method in order to evaluate the overall responses. A parameter study was also performed involving the working pressure and the restrictor diameter, with the objective to validate that a parameter change in the simulation model will affect the input and output power in the same direction as in the experiments. The experimental responses used in the validation were time history data of fluid pressure, component position and acceleration, and structural stresses. The experiments result in high frequency and high amplitude excitations of the hydraulic hammer and thus require a model with a high resolution of the model dynamics. The conclusion of the validation is that the simulation model is able to replicate the experimental responses with high accuracy including the high frequency dynamics. The favourable outcome of the validation makes the described co-simulation approach promising as an efficient tool for a wide range of other applications where short time duration mechanisms need to be studied.

  • 8.
    Andersson, Håkan
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Hilding, Daniel
    DYNAmore Nordic AB, Brigadgatan 5, 587 58 Linköping, Sweden.
    Schill, Mikael
    DYNAmore Nordic AB, Brigadgatan 5, 587 58 Linköping, Sweden.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    System level co-simulation of a control valve and hydraulic cylinder circuit in a hydraulic percussion unit2017Ingår i: Proceedings of 15:th Scandinavian International Conference on Fluid Power, June 7-9, 2017, Linköping, Sweden / [ed] Petter Krus, Liselott Ericson and Magnus Sethson, Linköping: Linköping University Electronic Press, 2017, Vol. 144, s. 225-235Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this study a previously developed co-simulation method that is based on a 1D system model representing the fluid components of a hydraulic machinery, within which structural 3D Finite Element (FE) models can be incorporated for detailed simulation of specific sub-models or complete structural assemblies, is further developed. The fluid system model consists of ordinary differential equation sub-models that are computationally very inexpensive, but still represents the fluid dynamics very well. The co-simulation method has been shown to work very well for a simple model representing a hydraulic driven machinery. A more complex model was set up in this work, in which two cylinders in the hydraulic circuit were evaluated. Such type of models, including both the main piston and control valves, are necessary as they represent the real application to a further extent than the simple model, of only one cylinder. Two models have been developed and evaluated, from the simple rigid body representation of the structural mechanics model, to the more complex model using linear elastic representation. The 3D FE-model facilitates evaluation of displacements, stresses, and strains on a local level of the model. The results can be utilised for fatigue assessment, wear analysis and for predictions of noise radiation.

  • 9.
    Andric, J.
    et al.
    Chalmers, Sweden.
    Lindström, Stefan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Sasic, S.
    Chalmers, Sweden.
    Nilsson, H.
    Chalmers, Sweden.
    Ballistic deflection of fibres in decelerating flow2016Ingår i: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 85, s. 57-66Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate the motion of inertial, rod-like fibres in the decelerating flow of a wedge-shaped channel with non-creeping fibre-flow interactions. We consider the trajectories of isolated fibres to identify the conditions for which these trajectories deflect from the streamlines of the flow as well as a rectilinear path. We carry out analytical and numerical studies under the assumption of an infinite fibre hydrodynamic resistance to transverse flow, and we expand the numerical study by taking into account a finite transverse hydrodynamic resistance. The analytical analysis identifies a longitudinal ballistic number Be and a transverse ballistic number B-t as two dimensionless parameters that govern the fibre dynamics. It is found that Be is the product of the Stokes number Ste(l) in the longitudinal direction of the fibre and the channel opening angle beta. As anticipated, a fibre moves along the streamlines in the viscosity-dominated regime (B-l amp;lt;amp;lt; 1, B-t amp;lt;amp;lt; 1), while it moves in a straight line without being rotated in the inertia-dominated regime (Bt amp;gt;amp;gt; 1). The focus of the present study is on the intermediate regime (B-l amp;gt;amp;gt; 1, B-t amp;lt; 1), in which we identify and analyse a fibre trajectory that significantly deviates from the streamlines of the flow. This behaviour is observed for both infinite and finite resistances to transverse flow, and it is referred to as ballistic deflection. We argue that ballistic deflection may increase the rate of collisions between suspended fibres, and thus potentially affects the rate of fibre aggregation in flowing suspensions. An order of magnitude estimate of the ballistic numbers identifies dry-forming of pulp mats, which includes an air-wood fibre flowing suspension, to operate in the regime of ballistic deflection. (C) 2016 Elsevier Ltd. All rights reserved.

  • 10.
    Andric, Jelena
    et al.
    Chalmers, Sweden.
    Lindström, Stefan B
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära.
    Sasic, Srdjan
    Chalmers, Sweden.
    Nilsson, Hakan
    Chalmers, Sweden.
    Numerical investigation of fiber flocculation in the air flow of an asymmetrical diffuser2014Ingår i: Proceedings of the 12th International Conference on Nanochannels, Microchannels and Minichannels (ICNMM), AMER SOC MECHANICAL ENGINEERS , 2014, nr V001T12A013, s. V001T12A013-Konferensbidrag (Refereegranskat)
    Abstract [en]

    A particle-level rigid fiber model is used to study flocculation in an asymmetric planar diffuser with a turbulent Newtonian fluid flow, resembling one stage in dry-forming process of pulp mats. The fibers are modeled as chains of rigid cylindrical segments. The equations of motion incorporate hydrodynamic forces and torques from the interaction with the fluid, and the fiber inertia is taken into account. The flow is governed by the Reynolds-averaged Navier-Stokes equations with the standard k - omega turbulence model. A one-way coupling between the fibers and the flow is considered. A stochastic model is employed for the flow fluctuations to capture the fiber dispersion. The fibers are assumed to interact through short-range attractive forces, causing them to interlock as the fiber-fiber contacts occur during the flow. It is found that the formation of fiber flocs is driven by both the turbulence-induced dispersion and the gradient of the averaged flow field.

  • 11.
    Andric, Jelena S.
    et al.
    Chalmers University of Technology, Sweden.
    Lindström, Stefan B
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Sasic, Srdjan M.
    Chalmers University of Technology, Sweden.
    Nilsson, Håkan
    Chalmers University of Technology, Sweden.
    PARTICLE-LEVEL SIMULATIONS OF FLOCCULATION IN A FIBER SUSPENSION FLOWING THROUGH A DIFFUSER2017Ingår i: Thermal Science, ISSN 0354-9836, E-ISSN 2334-7163, Vol. 21, s. S573-S583Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate flocculation in dilute suspensions of rigid, straight fibers in a decelerating flow field of a diffuser. We carry out numerical studies using a particle-level simulation technique that takes into account the fiber inertia and the non-creeping fiber-flow interactions. The fluid flow is governed by the Reynolds averaged Navier-Stokes equations with the standard k-omega eddy-viscosity turbulence model. A one-way coupling between the fibers and the flow is considered with a stochastic model for the fiber dispersion due to turbulence. The fibers interact through short-range attractive forces that cause them to aggregate into flocs when fiber-fiber collisions occur. We show that ballistic deflection of fibers greatly increases the flocculation in the diffilser. The inlet fiber kinematics and the fiber inertia are the main parameters that affect fiber flocculation in the predffuser region.

  • 12.
    Azeez, Ahmed
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära.
    Effect of dwell time on stress intensity factor of ferritic steel for steam turbine applications2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In the transition from conventional to green energy production resources, steam turbines are used to satisfy the lack of energy during peaks in the demand times and the limited access of renewable resources. This type of usage for steam turbines makes them operate on a flexible schedule, which leads to unpredictable issues related to shorter component life and faster crack propagation. Thus, the steam turbine components must be examined to determine their specific life period. This will help set proper maintenance intervals and prevent unexpected failures. For that, thermo-mechanical fatigue (TMF) testing is used, where a specimen made of the same material as the turbine component is subjected to both temperature and load variation. The specimen is pre-cracked to investigate the crack propagation behavior, which is the focus of this study.

    This thesis work concentrates on simulating the TMF cycle for the steam turbine casing component. The material is 9%-10%Cr ferritic steel. The aim is to understand the material behavior during crack propagation and to predict a useful testing parameter. The method provided in this work discusses two cases, both are out-of-phase (OP) TMF tests with strain control. The maximum and minimum temperatures for the cycle are 600 ˚C and 400 ˚C respectively, while the maximum and minimum strain levels are 0 and  respectively. The study will investigate different , which is the maximum compressive strain level. Case 1 has a dwell time at the maximum temperature only, while case 2 has dwell times at both maximum and minimum temperatures. The method utilizes the stress intensity factor (SIF) to characterize the crack tip conditions. Also, it uses Paris' law to estimate the duration of the tests. For simplification, only the elastic behavior of the material is considered.

    The results obtained show no effect of using different pre-crack lengths due to the strain control condition. Minor effects can be observed by using different dwell times, however very short dwell times must be avoided to produce reliable results. A recommended dwell time of 5 minutes could be used, since longer dwell times will make the test prohibitively time-consuming. The compressive strain levels used in the work shows large effects on the results. Using low compressive strain values will produce a very long time for the tests, while very high compressive strains produce large plasticity. Thus, high compressive strains must be avoided since the SIF describes cracks for only elastic or near elastic cases. Also, small compressive strain levels in case 2 should not be used since it will lead to results like case 1. This is due to the small creep effect at the minimum temperature. Finally, compressive strain levels of 0.6 %, 0.5 % and 0.4 % are recommended for case 1, while only 0.6 % compressive strain level is recommended for case 2.

    This thesis contributes to the fields of solid mechanics, fracture mechanics and the use of TMF testing, where a recommended set of testing parameters are provided.

  • 13.
    Azeez, Ahmed
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Filosofiska fakulteten. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Characterisation of Deformation and Damage in a Steam Turbine Steel Subjected to Low Cycle Fatigue2019Ingår i: Structural Integrity Procedia / [ed] Elsevier, 2019Konferensbidrag (Refereegranskat)
  • 14.
    Azeez, Ahmed
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Filosofiska fakulteten. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Lindström, Stefan B
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Low Cycle Fatigue Modelling of Steam Turbine Rotor Steel2019Ingår i: Structural Integrity Procedia / [ed] Elsevier, Elsevier, 2019Konferensbidrag (Refereegranskat)
  • 15.
    Benselfelt, Tobias
    et al.
    Department of Fiber Technology, KTH, Stockholm, Sweden.
    Nordenström, Malin
    Department of Fiber Technology, KTH, Stockholm, Sweden.
    Lindström, Stefan B
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Wågberg, Lars
    Department of Fiber Technology, KTH, Stockholm, Sweden.
    Explaining the Exceptional Wet Integrity of Transparent Cellulose Nanofibril Films in the Presence of Multivalent Ions: Suitable Substrates for Biointerfaces2019Ingår i: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 13, nr 6, artikel-id 1900333Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cellulose nanofibrils (CNFs) assemble into water‐resilient materials in the presence of multivalent counter‐ions. The essential mechanisms behind these assemblies are ion–ion correlation and specific ion effects. A network model shows that the interfibril attraction indirectly influences the wet modulus by a fourth power relationship to the solidity of the network (Ew ∝ φ4). Ions that induce both ion–ion correlation and specific ion effects significantly reduce the swelling of the films, and due to the nonlinear relationship dramatically increase the wet modulus. Herein, this network model is used to explain the elastoplastic behavior of wet films of 2,2,6,6‐tetramethylpiperidine‐1‐oxyl radical (TEMPO)‐oxidized, carboxymethylated, and phosphorylated CNFs in the presence of different counter‐ions. The main findings are that the aspect ratio of the CNFs influences the ductility of the assemblies, that the bivalency of phosphorylate ligands probably limits the formation of interfibril complexes with divalent ions, and that a higher charge density increases the friction between fibrils by increasing the short‐range attraction from ion–ion correlation and specific ion effects. These findings can be used to rationally design CNF materials for a variety of applications where wet strength, ductility, and transparency are important, such as biomaterials or substrates for bioelectronics.

  • 16.
    Berglund, Martina
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Logistik- och kvalitetsutveckling. Linköpings universitet, Tekniska fakulteten.
    Andersson, Torbjörn
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Maskinkonstruktion. Linköpings universitet, Tekniska fakulteten.
    Hedbrant, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska fakulteten.
    Pavlasevic, Vanja
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Maskinkonstruktion. Linköpings universitet, Tekniska fakulteten.
    Stålhand, Jonas
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Understanding the user beyond ‘common sense’ – teaching Product Ergonomics to design engineering students2015Ingår i: Proceedings 19th Triennial Congress of the IEA, International Ergonomics Association , 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Multidisciplinary frameworks are needed to develop products that fit the human. Ergonomics is a multifaceted field that encompasses physical, cognitive and organizational aspects, and it is therefore a suitable subject to be taught to design engineering students.

    The objective of this paper was to describe and reflect upon how a systems perspective on Ergonomics is developed and conveyed in a course in Product Ergonomics to engineering students at the Design and Product Development (DPD) programme at Linköping University, Sweden. The paper is based on the authors’ experiences from teaching the course in Product Ergonomicsas well ason 52 students’ written reflections about their view on Ergonomics before and after taking the course.

    Means and ideas for teaching Ergonomics with a systems perspective included organizing a theoretical introduction into weekly themes and thereafter integrating and applying these themes in a product concept project under supervision of a multidisciplinary teacher team.

    The paper also reflects on how the systems perspective of Ergonomics is planned for and realized in the intended, implemented and attained curriculum.

  • 17.
    Berglund, Martina
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Logistik- och kvalitetsutveckling. Linköpings universitet, Tekniska fakulteten.
    Pavlasevic, Vanja
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Maskinkonstruktion. Linköpings universitet, Tekniska fakulteten.
    Andersson, Torbjörn
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Maskinkonstruktion. Linköpings universitet, Tekniska fakulteten.
    Hedbrant, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska fakulteten.
    Stålhand, Jonas
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Theme-based assessment of education in design and product development2014Ingår i: Proceedings of the 10th International CDIO Conference, Universitat Politècnica de Catalunya, 2014Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    One fundamental challenge in choosing an examination form to assess student achievements is to find an examination which, both encourages students to continuously elaborate the course content and constitutes a learning process itself. The objective of this paper is to share and reflect on the development and implementation of a new theme-based examination in a six credit course in Product Ergonomics given in the engineering programme Design and Product Development at Linköping University, Sweden. The course runs during four months and has two parts: one theoretical and one applied. The former focuses on theoretical ergonomic topics, models and methods while the latter is a project aiming at consolidating the students’ understanding of the theory by implementing the knowledge in a product development case. To encourage the students to adapt a deep learning approach, the traditional written mid-term exam for the theoretical part was abandoned and another concept developed. In the new concept, the theoretical part was split onto six weekly themes. Each theme was introduced at the beginning of the week by high-lighting main theories and models followed by a group-work assignment to be elaborated on by the students during the week. The theme was examined at the end of the week through a short written exam and a seminar to discuss and reflect upon the theme. From a student perspective, the positive outcome of the theme-based examination was peer learning and a more active learning style. The students appreciated the theme-based structure of the course. Occasionally, some students commented that weekly examinations could be perceived as stressful. The teachers perceived the students to be more acquainted with ergonomics theory and methods which increased the quality of the course project. The reported theme-based assessment is one example of implementing among others the CDIO syllabus parts 2.2 and 3.1and CDIO standards 8 and 11.

  • 18.
    Busse, Christian
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Aspects of Crack Growth in Single-Crystal Nickel-Base Superalloys2017Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Denna licentiatavhandling är en produkt av resultat som genererats i forskningsprojektet KME-702, och omfattar modellering, mikrostrukturundersökningar och materialprovning av gjutna nickelbaserade superlegeringar.

    Huvudsyftet med detta arbete är att modellera sprickförloppet under utmattning i enkristallina nickelbaserade superlegeringar. För att uppnå detta har kristallorienteringens inverkan på sprickbeteendet utvärderats. Resultaten visar att kristallorienteringen har en stark inverkan på materialbeteendet, således måste hänsyn till denna tas. Dessutom har en linjär-elastisk sprickdrivkraftsparameter lämplig att beskriva kristallografisk sprickbildning utvecklats. Denna parameter är baserad på anisotropa spänningsintensitetsfaktorer på kristallplan och kan prediktera det korrekta kristallografiska sprickplanet efter övergång från Modus I spricka. Slutligen har undersökts en metod för att ta hand om inelastiska deformationer i en linjär-elastisk brottmekanikskontext. Ett restspänningsfält extraherades från en osprucken finita element modell med en ideal plastisk materialmodell. Denna överlagrades på spänningsfältet från den spruckna modellen, som analyserades med en linjär-elastisk materialmodell, för att ta hänsyn till de inelastiska deformationerna vid bestämning av sprickdrivkraften. Modelleringsarbetet validerades genom materialprovning på två olika provgeometrier vid olika temperaturer.

    Licentiatavhandlingen består av två delar, där del I ger en introduktion och bakgrund till forskningsområdet medan del II består av tre papper.

    Delarbeten
    1. A FINITE ELEMENT STUDY OF THE EFFECT OF CRYSTAL ORIENTATION AND MISALIGNMENT ON THE CRACK DRIVING FORCE IN A SINGLE-CRYSTAL SUPERALLOY
    Öppna denna publikation i ny flik eller fönster >>A FINITE ELEMENT STUDY OF THE EFFECT OF CRYSTAL ORIENTATION AND MISALIGNMENT ON THE CRACK DRIVING FORCE IN A SINGLE-CRYSTAL SUPERALLOY
    Visa övriga...
    2016 (Engelska)Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2016, VOL 7A, AMER SOC MECHANICAL ENGINEERS , 2016, nr UNSP V07AT28A002Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    The elastic and plastic anisotropy of the single-crystal materials bring many difficulties in terms of modeling, evaluation and prediction of fatigue crack growth. In this paper a single-crystal material model has been adopted to a finite element-environment, which is paired with a crack growth tool. All simulations are performed in a three-dimensional context. This methodology makes it possible to analyze complex finite element-models, which are more application-near than traditional two-dimensional models. The influence of the crystal orientation, as well as the influence of misalignments of the crystal orientation due to the casting process are investigated. It is shown that both the crystal orientation and the misalignment from the ideal crystal orientation are important for the crack driving force. The realistic maximum limit of 10 degrees misalignment is considered. It can be seen that crack growth behavior is highly influenced by the misalignment. This knowledge is of great interest for the industry in order to evaluate the crack growth in single-crystal components more accurately.

    Ort, förlag, år, upplaga, sidor
    AMER SOC MECHANICAL ENGINEERS, 2016
    Nationell ämneskategori
    Teknisk mekanik
    Identifikatorer
    urn:nbn:se:liu:diva-132570 (URN)10.1115/GT2016-56305 (DOI)000385461600011 ()978-0-7918-4983-5 (ISBN)
    Konferens
    ASME Turbo Expo: Turbine Technical Conference and Exposition
    Tillgänglig från: 2016-11-14 Skapad: 2016-11-14 Senast uppdaterad: 2019-11-19
    2. Three-Dimensional LEFM Prediction of Fatigue Crack Propagation in a Gas Turbine Disk Material at Component Near Conditions
    Öppna denna publikation i ny flik eller fönster >>Three-Dimensional LEFM Prediction of Fatigue Crack Propagation in a Gas Turbine Disk Material at Component Near Conditions
    Visa övriga...
    2016 (Engelska)Ingår i: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 138, nr 4, artikel-id 042506Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    In this paper, the possibility to use linear elastic fracture mechanics (LEFM), with and without a superimposed residual stress field, to predict fatigue crack propagation in the gas turbine disk material Inconel 718 has been studied. A temperature of 400 degrees C and applied strain ranges corresponding to component near conditions have been considered. A three-dimensional crack propagation software was used for determining the stress intensity factors (SIFs) along the crack path. In the first approach, a linear elastic material behavior was used when analyzing the material response. The second approach extracts the residual stresses from an uncracked model with perfectly plastic material behavior after one loading cycle. As a benchmark, the investigated methods are compared to experimental tests, where the cyclic lifetimes were calculated by an integration of Paris law. When comparing the results, it can be concluded that the investigated approaches give good results, at least for longer cracks, even though plastic flow was taking place in the specimen. The pure linear elastic simulation overestimates the crack growth for all crack lengths and gives conservative results over all considered crack lengths. Noteworthy with this work is that the 3D-crack propagation could be predicted with the two considered methods in an LEFM context, although plastic flow was present in the specimens during the experiments.

    Ort, förlag, år, upplaga, sidor
    ASME, 2016
    Nationell ämneskategori
    Maskinteknik
    Identifikatorer
    urn:nbn:se:liu:diva-126240 (URN)10.1115/1.4031526 (DOI)000371125800020 ()
    Anmärkning

    Funding Agencies|Siemens Industrial Turbomachinery AB through Research Consortium of Materials Technology for Thermal Energy Processes [KME-702]; Swedish Energy Agency

    Tillgänglig från: 2016-03-21 Skapad: 2016-03-21 Senast uppdaterad: 2019-11-19
  • 19.
    Busse, Christian
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Modelling of Crack Growth in Single-Crystal Nickel-Base Superalloys2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This dissertation was produced at the Division of Solid Mechanics at Linköping University and is part of a research project, which comprises modelling, microstructure investigations and material testing of cast nickel-base superalloys. The main objective of this work was to deepen the understanding of the fracture behaviour of single-crystal nickel-base superalloys and to develop a model to predict the fatigue crack growth behaviour. Frequently, crack growth in these materials has been observed to follow one of two distinct cracking modes; Mode I like cracking perpendicular to the loading direction or crystallographic crack growth on the octahedral {111}-planes, where the latter is associated with an increased fatigue crack growth rate. Thus, it is of major importance to account for this behaviour in component life prediction. Consequently, a model for the prediction of the transition of cracking modes and the correct active crystallographic plane, i.e. the crack path, and the crystallographic crack growth rate has been developed. This model is based on the evaluation of appropriate crack driving forces using three-dimensional finite-element simulations. A special focus was given towards the influence of the crystallographic orientation on the fracture behaviour. Further, a model to incorporate residual stresses in the crack growth modelling is presented. All modelling work is calibrated and validated by experiments on different specimen geometries with different crystallographic orientations. This dissertation consists of two parts, where Part I gives an introduction and background to the field of research, while Part II consists of six appended papers.

    Delarbeten
    1. A FINITE ELEMENT STUDY OF THE EFFECT OF CRYSTAL ORIENTATION AND MISALIGNMENT ON THE CRACK DRIVING FORCE IN A SINGLE-CRYSTAL SUPERALLOY
    Öppna denna publikation i ny flik eller fönster >>A FINITE ELEMENT STUDY OF THE EFFECT OF CRYSTAL ORIENTATION AND MISALIGNMENT ON THE CRACK DRIVING FORCE IN A SINGLE-CRYSTAL SUPERALLOY
    Visa övriga...
    2016 (Engelska)Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2016, VOL 7A, AMER SOC MECHANICAL ENGINEERS , 2016, nr UNSP V07AT28A002Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    The elastic and plastic anisotropy of the single-crystal materials bring many difficulties in terms of modeling, evaluation and prediction of fatigue crack growth. In this paper a single-crystal material model has been adopted to a finite element-environment, which is paired with a crack growth tool. All simulations are performed in a three-dimensional context. This methodology makes it possible to analyze complex finite element-models, which are more application-near than traditional two-dimensional models. The influence of the crystal orientation, as well as the influence of misalignments of the crystal orientation due to the casting process are investigated. It is shown that both the crystal orientation and the misalignment from the ideal crystal orientation are important for the crack driving force. The realistic maximum limit of 10 degrees misalignment is considered. It can be seen that crack growth behavior is highly influenced by the misalignment. This knowledge is of great interest for the industry in order to evaluate the crack growth in single-crystal components more accurately.

    Ort, förlag, år, upplaga, sidor
    AMER SOC MECHANICAL ENGINEERS, 2016
    Nationell ämneskategori
    Teknisk mekanik
    Identifikatorer
    urn:nbn:se:liu:diva-132570 (URN)10.1115/GT2016-56305 (DOI)000385461600011 ()978-0-7918-4983-5 (ISBN)
    Konferens
    ASME Turbo Expo: Turbine Technical Conference and Exposition
    Tillgänglig från: 2016-11-14 Skapad: 2016-11-14 Senast uppdaterad: 2019-11-19
    2. Prediction of crystallographic cracking planes in single-crystal nickel-base superalloys
    Öppna denna publikation i ny flik eller fönster >>Prediction of crystallographic cracking planes in single-crystal nickel-base superalloys
    Visa övriga...
    2018 (Engelska)Ingår i: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 196, s. 206-223Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The inherent anisotropy of single-crystal nickel-base superalloys brings many difficulties in terms of modelling, evaluation and prediction of fatigue crack growth. Two models to predict on which crystallographic plane cracking will occur is presented. The models are based on anisotropic stress intensity factors resolved on crystallographic slip planes calculated in a three-dimensional finite-element context. The developed models have been compared to experiments on two different test specimen geometries. The results show that a correct prediction of the crystallographic cracking plane can be achieved. This knowledge is of great interest for the industry and academia to better understand and predict crack growth in single-crystal materials.

    Ort, förlag, år, upplaga, sidor
    Elsevier, 2018
    Nyckelord
    Single-crystal nickel-base superalloys; Anisotropy; Fracture mechanics; Stress intensity factor; Crystallographic cracking
    Nationell ämneskategori
    Teknisk mekanik
    Identifikatorer
    urn:nbn:se:liu:diva-148380 (URN)10.1016/j.engfracmech.2018.04.047 (DOI)000432704300014 ()
    Anmärkning

    Funding Agencies|Swedish Energy Agency; Siemens Industrial Turbomachinery AB through the Research Consortium of Materials Technology for Thermal Energy Processes [KME-702]

    Tillgänglig från: 2018-06-15 Skapad: 2018-06-15 Senast uppdaterad: 2019-11-19
    3. Evaluation of the crystallographic fatigue crack growth rate in a single-crystal nickel-base superalloy
    Öppna denna publikation i ny flik eller fönster >>Evaluation of the crystallographic fatigue crack growth rate in a single-crystal nickel-base superalloy
    Visa övriga...
    2019 (Engelska)Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 127, s. 259-267Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Cracks in single-crystal nickel-base superalloys have been observed to switch cracking mode from Mode I to crystallographic cracking. The crack propagation rate is usually higher on the crystallographic planes compared to Mode I, which is important to account for in crack growth life predictions. In this paper, a method to evaluate the crystallographic fatigue crack growth rate, based on a previously developed crystallographic crack driving force parameter, is presented. The crystallographic crack growth rate was determined by evaluating heat tints on the fracture surfaces of the test specimens from the experiments. Complicated crack geometries including multiple crystallographic crack fronts were modelled in a three dimensional finite element context, The data points of the crystallographic fatigue crack growth rate collapse on a narrow scatter band for the crystallographic cracks indicating a correlation with the previously developed crystallographic crack driving force.

    Ort, förlag, år, upplaga, sidor
    ELSEVIER SCI LTD, 2019
    Nyckelord
    Single-crystal nickel-base superalloys; Finite element analysis; Fracture mechanics; Stress intensity factor; Crystallographic cracking; Fatigue crack growth rate
    Nationell ämneskategori
    Teknisk mekanik
    Identifikatorer
    urn:nbn:se:liu:diva-160388 (URN)10.1016/j.ijfatigue.2019.05.023 (DOI)000482492600024 ()
    Anmärkning

    Funding Agencies|Linkoping University; Siemens Industrial Turbomachinery AB

    Tillgänglig från: 2019-09-23 Skapad: 2019-09-23 Senast uppdaterad: 2019-11-19
    4. Three-Dimensional LEFM Prediction of Fatigue Crack Propagation in a Gas Turbine Disk Material at Component Near Conditions
    Öppna denna publikation i ny flik eller fönster >>Three-Dimensional LEFM Prediction of Fatigue Crack Propagation in a Gas Turbine Disk Material at Component Near Conditions
    Visa övriga...
    2016 (Engelska)Ingår i: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 138, nr 4, artikel-id 042506Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    In this paper, the possibility to use linear elastic fracture mechanics (LEFM), with and without a superimposed residual stress field, to predict fatigue crack propagation in the gas turbine disk material Inconel 718 has been studied. A temperature of 400 degrees C and applied strain ranges corresponding to component near conditions have been considered. A three-dimensional crack propagation software was used for determining the stress intensity factors (SIFs) along the crack path. In the first approach, a linear elastic material behavior was used when analyzing the material response. The second approach extracts the residual stresses from an uncracked model with perfectly plastic material behavior after one loading cycle. As a benchmark, the investigated methods are compared to experimental tests, where the cyclic lifetimes were calculated by an integration of Paris law. When comparing the results, it can be concluded that the investigated approaches give good results, at least for longer cracks, even though plastic flow was taking place in the specimen. The pure linear elastic simulation overestimates the crack growth for all crack lengths and gives conservative results over all considered crack lengths. Noteworthy with this work is that the 3D-crack propagation could be predicted with the two considered methods in an LEFM context, although plastic flow was present in the specimens during the experiments.

    Ort, förlag, år, upplaga, sidor
    ASME, 2016
    Nationell ämneskategori
    Maskinteknik
    Identifikatorer
    urn:nbn:se:liu:diva-126240 (URN)10.1115/1.4031526 (DOI)000371125800020 ()
    Anmärkning

    Funding Agencies|Siemens Industrial Turbomachinery AB through Research Consortium of Materials Technology for Thermal Energy Processes [KME-702]; Swedish Energy Agency

    Tillgänglig från: 2016-03-21 Skapad: 2016-03-21 Senast uppdaterad: 2019-11-19
  • 20.
    Busse, Christian
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Gustafsson, David
    Siemens Ind Turbomachinery AB, Sweden.
    Rasmusson, Patrik
    Siemens Ind Turbomachinery AB, Sweden.
    Sjodin, Bjorn
    Siemens Ind Turbomachinery AB, Sweden.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Three-Dimensional LEFM Prediction of Fatigue Crack Propagation in a Gas Turbine Disk Material at Component Near Conditions2016Ingår i: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 138, nr 4, artikel-id 042506Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, the possibility to use linear elastic fracture mechanics (LEFM), with and without a superimposed residual stress field, to predict fatigue crack propagation in the gas turbine disk material Inconel 718 has been studied. A temperature of 400 degrees C and applied strain ranges corresponding to component near conditions have been considered. A three-dimensional crack propagation software was used for determining the stress intensity factors (SIFs) along the crack path. In the first approach, a linear elastic material behavior was used when analyzing the material response. The second approach extracts the residual stresses from an uncracked model with perfectly plastic material behavior after one loading cycle. As a benchmark, the investigated methods are compared to experimental tests, where the cyclic lifetimes were calculated by an integration of Paris law. When comparing the results, it can be concluded that the investigated approaches give good results, at least for longer cracks, even though plastic flow was taking place in the specimen. The pure linear elastic simulation overestimates the crack growth for all crack lengths and gives conservative results over all considered crack lengths. Noteworthy with this work is that the 3D-crack propagation could be predicted with the two considered methods in an LEFM context, although plastic flow was present in the specimens during the experiments.

  • 21.
    Busse, Christian
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Loureiro Homs, Jordi
    Siemens Ind Turbomachinery AB, Sweden.
    Gustafsson, David
    Siemens Ind Turbomachinery AB, Sweden.
    Palmert, Frans
    Siemens Ind Turbomachinery AB, Sweden.
    Sjodin, Bjorn
    Siemens Ind Turbomachinery AB, Sweden.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    A FINITE ELEMENT STUDY OF THE EFFECT OF CRYSTAL ORIENTATION AND MISALIGNMENT ON THE CRACK DRIVING FORCE IN A SINGLE-CRYSTAL SUPERALLOY2016Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2016, VOL 7A, AMER SOC MECHANICAL ENGINEERS , 2016, nr UNSP V07AT28A002Konferensbidrag (Refereegranskat)
    Abstract [en]

    The elastic and plastic anisotropy of the single-crystal materials bring many difficulties in terms of modeling, evaluation and prediction of fatigue crack growth. In this paper a single-crystal material model has been adopted to a finite element-environment, which is paired with a crack growth tool. All simulations are performed in a three-dimensional context. This methodology makes it possible to analyze complex finite element-models, which are more application-near than traditional two-dimensional models. The influence of the crystal orientation, as well as the influence of misalignments of the crystal orientation due to the casting process are investigated. It is shown that both the crystal orientation and the misalignment from the ideal crystal orientation are important for the crack driving force. The realistic maximum limit of 10 degrees misalignment is considered. It can be seen that crack growth behavior is highly influenced by the misalignment. This knowledge is of great interest for the industry in order to evaluate the crack growth in single-crystal components more accurately.

  • 22.
    Busse, Christian
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Palmert, Frans
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Sjodin, B.
    Siemens Ind Turbomachinery AB, Sweden.
    Almroth, P.
    Siemens Ind Turbomachinery AB, Sweden.
    Gustafsson, D.
    Siemens Ind Turbomachinery AB, Sweden.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Evaluation of the crystallographic fatigue crack growth rate in a single-crystal nickel-base superalloy2019Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 127, s. 259-267Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cracks in single-crystal nickel-base superalloys have been observed to switch cracking mode from Mode I to crystallographic cracking. The crack propagation rate is usually higher on the crystallographic planes compared to Mode I, which is important to account for in crack growth life predictions. In this paper, a method to evaluate the crystallographic fatigue crack growth rate, based on a previously developed crystallographic crack driving force parameter, is presented. The crystallographic crack growth rate was determined by evaluating heat tints on the fracture surfaces of the test specimens from the experiments. Complicated crack geometries including multiple crystallographic crack fronts were modelled in a three dimensional finite element context, The data points of the crystallographic fatigue crack growth rate collapse on a narrow scatter band for the crystallographic cracks indicating a correlation with the previously developed crystallographic crack driving force.

  • 23.
    Busse, Christian
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Palmert, Frans
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Sjodin, B.
    Siemens Ind Turbomachinery AB, Sweden.
    Almroth, P.
    Siemens Ind Turbomachinery AB, Sweden.
    Gustafsson, D.
    Siemens Ind Turbomachinery AB, Sweden.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Prediction of crystallographic cracking planes in single-crystal nickel-base superalloys2018Ingår i: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 196, s. 206-223Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The inherent anisotropy of single-crystal nickel-base superalloys brings many difficulties in terms of modelling, evaluation and prediction of fatigue crack growth. Two models to predict on which crystallographic plane cracking will occur is presented. The models are based on anisotropic stress intensity factors resolved on crystallographic slip planes calculated in a three-dimensional finite-element context. The developed models have been compared to experiments on two different test specimen geometries. The results show that a correct prediction of the crystallographic cracking plane can be achieved. This knowledge is of great interest for the industry and academia to better understand and predict crack growth in single-crystal materials.

    Publikationen är tillgänglig i fulltext från 2020-05-05 15:21
  • 24.
    Busse, Christian
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Palmert, Frans
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Siemens Ind Turbomachinery AB, Sweden.
    Wawrzynek, Paul
    Fracture Anal Consultants Inc, NY USA.
    Sjodin, Bjorn
    Siemens Ind Turbomachinery AB, Sweden.
    Gustafsson, David
    Siemens Ind Turbomachinery AB, Sweden.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Crystallographic crack propagation rate in single-crystal nickel-base superalloys2018Ingår i: 12TH INTERNATIONAL FATIGUE CONGRESS (FATIGUE 2018), E D P SCIENCES , 2018, Vol. 165, artikel-id 13012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Single-crystal nickel-base superalloys are often used in the hot sections of gas turbines due to their good mechanical properties at high temperatures such as enhanced creep resistance. However, the anisotropic material properties of these materials bring many difficulties in terms of modelling and crack growth prediction. Cracks tend to switch cracking mode from Mode I cracking to crystallographic cracking. Crystallographic crack growth is often associated with a decrease in crack propagation life compared to Mode I cracking and this must be taken into account for reliable component lifing. In this paper a method to evaluate the crystallographic crack propagation rate related to a crystallographic crack driving force parameter is presented. The crystallographic crack growth rate is determined by an evaluation of heat tints on the fracture surface of a specimen subjected to fatigue loading. The complicated crack geometry including two crystallographic crack fronts is modelled in a three dimensional finite element context. The crack driving force parameter is determined by calculating anisotropic stress intensity factors along the two crystallographic crack fronts by finite-element simulations and post-processing the data in a fracture mechanics tool that resolves the stress intensity factors on the crystallographic slip planes in the slip directions. The evaluated crack propagation rate shows a good correlation for both considered crystallographic cracks fronts.

  • 25.
    Calmunger, Mattias
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Materials Technology, Sandviken, Sweden.
    Eriksson, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan J.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Characterization of austenitic stainless steels deformed at elevated temperature2017Ingår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 48A, nr 10, s. 4525-4538Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Highly alloyed austenitic stainless steels are promising candidates to replace more expansive nickel-based alloys within the energy-producing industry. The present study investigates the deformation mechanisms by microstructural characterisation, mechanical properties and stress-strain response of three commercial austenitic stainless steels and two commercial nickel-based alloys using uniaxial tensile tests at elevated temperatures from 400 C up to 700 C. The materials showed different influence of temperature on ductility, where the ductility at elevated temperatures increased with increasing nickel and solid solution hardening element content. The investigated materials showed planar dislocation driven deformation at elevated temperature. Scanning electron microscopy showed that deformation twins were an active deformation mechanism in austenitic stainless steels during tensile deformation at elevated temperatures up to 700 C.

  • 26.
    Calmunger, Mattias
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Influence of Cyclic Oxidation in Moist Air on Surface Oxidation-Affected Zones2017Konferensbidrag (Refereegranskat)
  • 27.
    Calmunger, Mattias
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Filosofiska fakulteten. Linköpings universitet, Tekniska fakulteten.
    Lindström, Thomas
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Effect of Additive Manufacturing on Fatigue Crack Propagation of a Gas Turbine Superalloy2019Ingår i: Structural Integrity Procedia, Elsevier, 2019Konferensbidrag (Refereegranskat)
  • 28.
    Daghighi, Abtin
    et al.
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för Kirurgi, Ortopedi och Onkologi. Linköpings universitet, Medicinska fakulteten.
    Tropp, Hans
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för Kirurgi, Ortopedi och Onkologi. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Centrum för kirurgi, ortopedi och cancervård, Ryggkliniken US.
    Dahlström, Nils
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Diagnostikcentrum, Röntgenkliniken i Linköping. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Klarbring, Anders
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    F.E.M. Stress-Investigation of Scolios Apex2018Ingår i: Open Biomedical Engineering Journal, ISSN 1874-1207, E-ISSN 1874-1207, Vol. 12, s. 51-71Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In scoliosis, kypholordos and wedge properties of the vertebrae should be involved in determining how stress is distributed in the vertebral column. The impact is logically expected to be maximal at the apex.

  • 29.
    Domeij Bäckryd, Rebecka
    et al.
    Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära.
    Ryberg, Ann-Britt
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten. Combitech AB, Trollhättan, Sweden.
    Nilsson, Larsgunnar
    Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära.
    Multidisciplinary design optimisation methods for automotive structures2017Ingår i: International Journal of Automotive and Mechanical Engineering, ISSN 2229-8649, Vol. 14, nr 1, s. 4050-4067Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Multidisciplinary design optimisation (MDO) can be used as an effective tool to improve the design of automotive structures. Large-scale MDO problems typically involve several groups who must work concurrently and autonomously in order to make the solution process efficient. In this article, the formulations of existing MDO methods are compared and their suitability is assessed in relation to the characteristics of automotive structural applications. Both multi-level and single-level optimisation methods are considered. Multi-level optimisation methods distribute the design process but are complex. When optimising automotive structures, metamodels are often required to relieve the computational burden of detailed simulation models. The metamodels can be created by individual groups prior to the optimisation process, and thus offer a way of distributing work. Therefore, it is concluded that a single-level method in combination with meta-models is the most straightforward way of implementing MDO into the development of automotive structures. If the benefits of multi-level optimisation methods, in a special case, are considered to compensate for their drawbacks, analytical target cascading has a number of advantages over collaborative optimisation, but both methods are possible choices.

  • 30.
    Eriksson, Robert
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Chen, Zhe
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Jonnalagadda, Krisha Praveen
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    BENDING FATIGUE OF THERMAL BARRIER COATINGS2017Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2017, VOL 6, AMER SOC MECHANICAL ENGINEERS , 2017, artikel-id V006T24A004Konferensbidrag (Refereegranskat)
    Abstract [en]

    Thermal barrier coatings (TBCs) are ceramic coatings used in gas turbines to lower the base metal temperature. During operation, the TBC may fail through, for example, fatigue. In the present study, a TBC system deposited on a Ni-base alloy was tested in tensile bending fatigue. The TBC system was tested as-sprayed and oxidized and two load levels were used. After interrupting the tests, at 10000-50000 cycles, the TBC tested at the lower load had extensive delamination damage whereas the TBC tested at the higher load was relatively undamaged. At the higher load, the TBC formed vertical cracks which relieved the stresses in the TBC and retarded delamination damage. A finite element analysis was used to establish a likely vertical crack configuration (spacing and depth) and it could be confirmed that the corresponding stress drop in the TBC should prohibit delamination damage at the higher load.

  • 31.
    Eriksson, Robert
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Chen, Zhe
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Jonnalagadda, Krisha Praveen
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Bending Fatigue of Thermal Barrier Coatings2017Ingår i: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 139, nr 12, s. 122101-1-122101-6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thermal barrier coatings (TBCs) are ceramic coatings used in gas turbines to lower the base metal temperature. During operation, the TBC may fail through, for example, fatigue. In this study, a TBC system deposited on a Ni-base alloy was tested in tensile bending fatigue. The TBC system was tested as-sprayed and oxidized, and two load levels were used. After interrupting the tests, at 10,000–50,000 cycles, the TBC tested at the lower load had extensive delamination damage, whereas the TBC tested at the higher load was relatively undamaged. At the higher load, the TBC formed vertical cracks which relieved the stresses in the TBC and retarded delamination damage. A finite element (FE) analysis was used to establish a likely vertical crack configuration (spacing and depth), and it could be confirmed that the corresponding stress drop in the TBC should prohibit delamination damage at the higher load.

  • 32.
    Eriksson, Robert
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Jonnalagadda, Krisha Praveen
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    A STUDY ON CRACK CONFIGURATIONS IN THERMAL BARRIER COATINGS2017Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2017, VOL 6, AMER SOC MECHANICAL ENGINEERS , 2017, artikel-id V006T24A005Konferensbidrag (Refereegranskat)
    Abstract [en]

    Spallation of thermal barrier coatings subjected to thermal fatigue occurs through cracking in or close to the metal ceramic interface. To better match an experimentally observed damage progression curve with initially slow crack growth followed by rapid crack growth, a multitude of crack paths were modeled in a finite element analysis. Comparisons with experimental data enabled the most likely crack path to be identified. It was shown that the most likely failure type for the studied TBC system was crack initiation from pre-existing defects in the thermal barrier coating which propagated into the interface, leading to spallation. The results were used to fit a crack propagation model.

  • 33.
    Eriksson, Robert
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chen, Zhe
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    A low cycle fatigue life model for a shot peened gas turbine disc alloy2019Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 124, s. 34-41Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Turbine disks in gas turbines are subjected to cyclic load at high temperature, making, especially the fir tree type blade attachments, susceptible to fatigue. Shot peening of the fir tree attachments may be used to increase the fatigue life by introducing compressive residual stresses. In the current study, both polished and shot peened notched specimens made from alloy 718 were subjected to low cycle fatigue at 450-550 degrees C. The shot peening generally increased the fatigue life, although the effect diminished for high loads. It was shown that the effect of shot peening could be handled as mean stress effects in a life model based on a Smith-Watson-Topper (SWT) type parameter, sigma(max)Delta epsilon/2. A material model which captured the mean stress was set up to get the SWT parameter at the notch root. It was shown that thermal relaxation of residual stresses and initial strain hardening from cold work could be excluded from the finite element analysis used to establish the mean stress; this since the plasticity in the first cycle dominated the plastic deformation of the specimen. Overall, the SWT-based life model worked satisfactorily. However, the prediction of correct mean stresses at 550 degrees C proved somewhat difficult as the degree of mean stress relaxation at this temperature varies widely in available literature data.

  • 34.
    Eriksson, Robert
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Evaluation of notch effects in low cycle fatigue of alloy 718 using critical distances2018Ingår i: 12TH INTERNATIONAL FATIGUE CONGRESS (FATIGUE 2018), E D P SCIENCES , 2018, Vol. 165, artikel-id 15001Konferensbidrag (Refereegranskat)
    Abstract [en]

    Gas turbine disks contain many notch-like features acting as stress raisers. The fatigue life based on the notch root stress may be overly conservative as the steep stress gradient in front of the notch may give rise to so-called notch support. In the current work, the theory of critical distances was applied to the prediction of the total fatigue life of low cycle fatigued, notched specimens made from alloy 718. The fatigue tests were performed at 450 degrees C and 550 degrees C. It was found that, for lives shorter than 5000-10000 cycles, the notched specimens had longer lives than would have been expected based on the notch root strain. For lives longer than 5000-10000 cycles, there were no notch support. The life prediction for notched specimens could be significantly improved by basing the prediction on the strain chosen some distance from the notch (the critical distance). An expression for calculating the critical distance based on the notch root strain was suggested.

  • 35.
    Eriksson, Robert
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Filosofiska fakulteten.
    Torstenfelt, Bo
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Klarbring, Anders
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    OPTIMIZING THERMAL BARRIER COATING DESIGN USING STRUCTURAL OPTIMIZATION METHODS2017Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2017, VOL 6, AMER SOC MECHANICAL ENGINEERS , 2017, artikel-id V006T24A003Konferensbidrag (Refereegranskat)
    Abstract [en]

    Thermal barrier coatings (TBCs) are used in gas turbines to reduce creep, thermo-mechanical fatigue, and oxidation, or to allow for reduced air cooling. TBCs may fail due to fatigue. Structural optimization methods were applied to optimize the. TBC thickness in such a way as to increase the life of the TBC. The TBC thickness was varied for three cases: 1) minimizing TBC volume, 2) minimizing TBC maximum effective stress, and 3) minimizing compliance (minimizing the strain energy). The results from the optimization were used to estimate the relative change in TBC life via a strain energy based failure criterion and a Coffin-Manson-like expression. Minimization of volume had limited use due to limitations in the current implementation. Minimization of effective stress did not give any significant increase in life. The minimization of compliance increased the estimated TBC life at highly stressed regions.

  • 36.
    Ewest, D.
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten. Siemens Ind Turbomachinery AB, Sweden.
    Almroth, P.
    Siemens Ind Turbomachinery AB, Sweden.
    Sjodin, B.
    Siemens Ind Turbomachinery AB, Sweden.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    A modified compliance method for fatigue crack propagation applied on a single edge notch specimen2016Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 92, s. 61-70Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Crack length measurements with high accuracy are often difficult to achieve during fatigue crack propagation testing under non-isothermal conditions. In this work a modified approach to the compliance method defined in e.g. ASTM E647 is described, which is better suited for high loads, varying temperatures and for taking the scatter in Youngs modulus into account. A numerical finite element study is performed for a single edge notch specimen, to investigate the influence of initiation locations on the accuracy of the method. The change in cracked area versus change in stiffness for three different cases are numerically shown to collapse to one curve, i.e. the result is not significantly affected by how the crack is initiated. The numerical study is compared to results from two experiments using different materials, with heat tinting during the tests for extracting snapshots of the crack fronts. A good agreement between the experiments and the numerical study is shown. A new compliance curve and a new geometry function for the stress intensity factor is proposed for the single edge notch specimen. (C) 2016 Elsevier Ltd. All rights reserved.

  • 37.
    Ewest, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Modelling and experimental evaluation of non-linear fatigue crack propagation in a ductile superalloy2016Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Fatigue life evaluation is an important part in the design process of an industrial gas turbine. The fatigue life can be divided into crack initiation and crack propagation, and not to address the crack propagation part usually yields a non-conservative and overcomplicated design. Historically a lot of attention has been directed towards the crack initiation, but the crack propagation part in an industrial gas turbine context has not been given the same attention due to limitations in theoretical modelling, lack of test possibilities and that the design requirements have been fulfilled within the initiation life. However, with the need to reduce service down time and to improve performance, the crack propagation life needs to be further accounted for. As an example, cracks that emerge from notches or other stress concentrations grow under non-elastic conditions, which cannot be modelled with linear theories.

    In this Licentiate of Engineering thesis a non-linear approach is put forward in which the plastic contribution in fatigue crack propagation is addressed and accounted for. The theoretical background is not new, but the finite element implementation done was, to the author knowledge, not available. This numerical post processing tool can calculate the non-linear ΔJ value for an arbitrary 2D-geometry. It was used to produce an expression for a non-linear geometry factor used in a simple expression for estimation of ΔJ in a test evaluation context. Room temperature tests were performed on a single notch specimen, under both displacement and force control. The latter were carried out in order to show the behaviour under small scale yielding conditions, while the displacement controlled testing was to show large scale yielding at the beginning of the tests. It was shown that all the test results could be collected in a Paris law type plot with ΔJ if the crack closure effect is taken into account. Furthermore, a study was performed where both a linear and a non-linear approach are applied on the displacement controlled tests. It was concluded that for the studied test series, the linear fatigue fracture parameter ΔK underestimates the crack growth behaviour if the elasto-plastic stresses from the tests are used, hence yielding non-conservative results.

    Since this project focuses on non-linear crack propagation at thermo-mechanical conditions a crack length description is put forward, which simplifies and increases the accuracy of crack length measurements in fatigue crack propagation tests. It has also been shown that irrespectively of the crack initiation location in a single edge notch specimen the data fall on one curve, meaning that no care has to be taken regarding this aspect when evaluating crack length with the modified compliance method put forward in Paper III.

    This Licentiate of Engineering thesis consists of two parts, where Part I gives an introduction to the subject, while Part II consists of three papers.

    Delarbeten
    1. Fatigue crack propagation in a ductile superalloy at room temperature and extensive cyclic plastic flow
    Öppna denna publikation i ny flik eller fönster >>Fatigue crack propagation in a ductile superalloy at room temperature and extensive cyclic plastic flow
    Visa övriga...
    2015 (Engelska)Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 80, s. 40-49Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Fatigue crack propagation experiments under both force and displacement control have been performed on the wrought superalloy Haynes 230 at room temperature, using a single edge notched specimen. The force controlled tests are nominally elastic, and the displacement controlled tests have nominally large plastic hysteresis at the beginning of the tests, but saturates towards linear elastic conditions as the crack grows. As some tests are in the large scale yielding regime, a non-linear fracture mechanics approach is used to correlate crack growth rates versus the fracture parameter Delta J. It is shown that crack closure must be accounted for, to correctly model the crack growth seen in all the tests in a unified manner. For the force controlled small scale yielding tests the Newman crack closure model was used. The Newman equation is however not valid for large nominal cyclic plasticity, instead the crack closure in the displacement controlled tests is extracted from the test data. A good agreement between all tests is shown, when closure is accounted for and effective values of Delta J are used.

    Ort, förlag, år, upplaga, sidor
    ELSEVIER SCI LTD, 2015
    Nyckelord
    Fatigue crack propagation; Haynes 230; Large scale yielding; Cyclic J-integral or Delta J; Crack closure
    Nationell ämneskategori
    Teknisk mekanik
    Identifikatorer
    urn:nbn:se:liu:diva-122045 (URN)10.1016/j.ijfatigue.2015.04.006 (DOI)000360596500005 ()
    Anmärkning

    Funding Agencies|Siemens Industrial Turbomachinery AB, Finspang, Sweden

    Tillgänglig från: 2015-12-18 Skapad: 2015-10-19 Senast uppdaterad: 2017-12-01
    2. Comparison between linear and non-linear fracture mechanics analysis of experimental data for the ductile superalloy Haynes 230
    Öppna denna publikation i ny flik eller fönster >>Comparison between linear and non-linear fracture mechanics analysis of experimental data for the ductile superalloy Haynes 230
    Visa övriga...
    2016 (Engelska)Ingår i: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 138, nr 6, s. 062101-1-062101-7Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    With increasing use of renewable energy sources, an industrial gas turbine is often a competitive solution to balance the power grid. However, life robustness approaches for gas turbine components operating under increasingly cyclic conditions are a challenging task. Ductile superalloys, as Haynes 230, are often used in stationary gas turbine hot parts such as combustors. The main load for such components is due to nonhomogeneous thermal expansion within or between parts. As the material is ductile, there is considerable redistribution of stresses and strains due to inelastic deformations during the crack initiation phase. Therefore, the subsequent crack growth occurs through a material with significant residual stresses and strains. In this work, fatigue crack propagation experiments, including the initiation phase, have been performed on a single edge notched specimen under strain controlled conditions. The test results are compared to fracture mechanics analyses using the linear ΔK and the nonlinear ΔJ approaches, and an attempt to quantify the difference in terms of a life prediction is made. For the tested notched geometry, material, and strain ranges, the difference in the results using ΔKeff or ΔJeff is larger than the scatter seen when fitting the model to the experimental data. The largest differences can be found for short crack lengths, when the cyclic plastic work is the largest. The ΔJ approach clearly shows better agreement with the experimental results in this regime.

    Ort, förlag, år, upplaga, sidor
    ASME Press, 2016
    Nationell ämneskategori
    Teknisk mekanik Annan materialteknik
    Identifikatorer
    urn:nbn:se:liu:diva-126576 (URN)10.1115/1.4031712 (DOI)000374713500010 ()
    Anmärkning

    Funding agencies: Siemens Industrial Turbomachinery AB, Finspang, Sweden

    Tillgänglig från: 2016-03-30 Skapad: 2016-03-30 Senast uppdaterad: 2017-11-30
  • 38.
    Ewest, Daniel
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten. Siemens Ind Turbomachinery AB,Finspång, Sweden.
    Almroth, P.
    Siemens Ind Turbomachinery AB, Finspång, Sweden.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Sjodin, B.
    Siemens Ind Turbomachinery AB, Finspång, Sweden.
    Fatigue crack propagation in a ductile superalloy at room temperature and extensive cyclic plastic flow2015Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 80, s. 40-49Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fatigue crack propagation experiments under both force and displacement control have been performed on the wrought superalloy Haynes 230 at room temperature, using a single edge notched specimen. The force controlled tests are nominally elastic, and the displacement controlled tests have nominally large plastic hysteresis at the beginning of the tests, but saturates towards linear elastic conditions as the crack grows. As some tests are in the large scale yielding regime, a non-linear fracture mechanics approach is used to correlate crack growth rates versus the fracture parameter Delta J. It is shown that crack closure must be accounted for, to correctly model the crack growth seen in all the tests in a unified manner. For the force controlled small scale yielding tests the Newman crack closure model was used. The Newman equation is however not valid for large nominal cyclic plasticity, instead the crack closure in the displacement controlled tests is extracted from the test data. A good agreement between all tests is shown, when closure is accounted for and effective values of Delta J are used.

  • 39.
    Ewest, Daniel
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten. Siemens Ind Turbomachinery AB, Sweden.
    Almroth, P.
    Siemens Ind Turbomachinery AB, Sweden.
    Sjodin, B.
    Siemens Ind Turbomachinery AB, Sweden.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Isothermal and thermomechanical fatigue crack propagation in both virgin and thermally aged Haynes 2302019Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 120, s. 96-106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fatigue crack propagation tests under both isothermal and non-isothermal thermomechanical fatigue conditions have been performed on wrought Haynes 230, a ductile combustor material. A number of specimens were thermally aged by pre-straining and subsequent furnace exposure for 3000 h at 600 degrees C. The tests were performed both under load and strain control, between room temperature and 600 degrees C. The thermally aged notched specimens show a decrease in the crack initiation life, similar to results previously reported for smooth test specimens at room temperature. For the crack growth rates, the effects of thermal ageing were less pronounced than for crack initiation. Further, the tests have been simulated using the finite element method to calculate the crack driving force, where the plasticity induced crack closure is handled with a full history description. A temperature dependent linear kinematic hardening plasticity law has been adopted for describing the material behaviour between room temperature and 600 degrees C. A post-processing tool was used in which the plasticity induced crack opening level was calculated, followed by a calculation of the effective Delta J range for each crack length. The adopted procedure yields good correlation between the different tests, under both isothermal and non-isothermal conditions.

  • 40.
    Ewest, Daniel
    et al.
    Siemens Ind Turbomachinery AB, Sweden.
    Almroth, Per
    Siemens Ind Turbomachinery AB, Sweden.
    Sjodin, Bjorn
    Siemens Ind Turbomachinery AB, Sweden.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    COMPARISON BETWEEN LINEAR AND NON-LINEAR FRACTURE MECHANICS ANALYSIS OF EXPERIMENTAL DATA FOR THE DUCTILE SUPERALLOY HAYNES 2302015Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2015, VOL 7A, ASME Press, 2015, nr V07AT28A014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Vith increasing use of renewable energy sources, an industrial us turbine is often a competitive solution to balance the power rid. However, life robustness approaches for gas turbine corn9nents operating under increasingly cyclic conditions, is a chalmging task. Ductile superalloys, as Haynes 230, are often used n stationary gas turbine hot parts such as combustors. The main cad for such components is due to non -homogeneous thermal xpansion within or between parts. As the material is ductile Jere is considerable redistribution of stresses and strains due to nelastic deformations during the crack initiation phase. There ore, the subsequent crack growth occurs through a material with :gnificant residual stresses and strains. In this work, fatigue ack propagation experiments, including the initiation phase, ave been performed on a single edge notched specimen under train controlled conditions. The test results are compared to -acture mechanics analyses using the linear AK and the non near AJ approaches, and an attempt to quantify the difference 2 terms of a life prediction is made. For the tested notched gemetry, material and strain ranges, the difference in the results using AKeff or ATeff are larger than the scatter seen when fitting the model to the experimental data. The largest differences can be found for short crack lengths, when the cyclic plastic work is the largest. The AJ approach clearly shows better agreement with the experimental results in this regime.

  • 41.
    Ewest, Daniel
    et al.
    Siemens Industrial Turbomachinery AB, Finspång, Sweden .
    Almroth, Per
    Siemens Industrial Turbomachinery AB, Finspång, Sweden .
    Sjödin, Björn
    Siemens Industrial Turbomachinery AB, Finspång, Sweden .
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Comparison between linear and non-linear fracture mechanics analysis of experimental data for the ductile superalloy Haynes 2302016Ingår i: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 138, nr 6, s. 062101-1-062101-7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With increasing use of renewable energy sources, an industrial gas turbine is often a competitive solution to balance the power grid. However, life robustness approaches for gas turbine components operating under increasingly cyclic conditions are a challenging task. Ductile superalloys, as Haynes 230, are often used in stationary gas turbine hot parts such as combustors. The main load for such components is due to nonhomogeneous thermal expansion within or between parts. As the material is ductile, there is considerable redistribution of stresses and strains due to inelastic deformations during the crack initiation phase. Therefore, the subsequent crack growth occurs through a material with significant residual stresses and strains. In this work, fatigue crack propagation experiments, including the initiation phase, have been performed on a single edge notched specimen under strain controlled conditions. The test results are compared to fracture mechanics analyses using the linear ΔK and the nonlinear ΔJ approaches, and an attempt to quantify the difference in terms of a life prediction is made. For the tested notched geometry, material, and strain ranges, the difference in the results using ΔKeff or ΔJeff is larger than the scatter seen when fitting the model to the experimental data. The largest differences can be found for short crack lengths, when the cyclic plastic work is the largest. The ΔJ approach clearly shows better agreement with the experimental results in this regime.

  • 42.
    Gade, Jan-Lucas
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Mechanical Properties of Arteries: Identification and Application2019Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    I denna licentiatavhandling föreslås en metod för att identifiera mekaniska egenskaper hos artärer in vivo. De mekaniska egenskaperna är kopplade till utvecklingen av hjärt-kärlsjukdomar, och möjligheten att identifiera dessa egenskaper skulle således kunna underlätta diagnostisering, behandling och uppföljning av dessa sjukdomar.

    Den förslagna metoden använder kliniskt mätbara tryck-radie-signaler och löser ett minimeringsproblem för att bestämma sex parametrar som beskriver kärlets mekaniska egenskaper. Artären modelleras som ett homogent, inkompressibelt och spänningsfritt tunnväggigt rör där kärlväggen utgörs av en elastindominerad matris armerad med inbäddade kollagenfibrer.

    För att validera parameteridentifieringen skapas en uppsättning representativa, virtuella artärer med hjälp av finita element. Dessa in silico-artärer baseras på publicerade data för mänsklig bukaorta och används för att generera fiktiva tryckradie-signaler vilka sedan matas in i den förslagna modellen. Genom att parametrar och randvillkor för in silico-artärerna är kända fungerar dessa som en kontroll mot vilka resultatet från parameteridentifieringen kan jämföras. Parametrarna som beskriver den icke trycksatta radien och den elastindominerade matrisen visar god överensstämmelse med de in silico-artärerna för friska kärl. Större diskrepans erhålls för de parametrar som associeras med kollagenet, och den största avvikelsen erhålls för den parameter som beskriver den axiella försträckningen. För artärer med patologiskt lågt elastininnehåll identifieras felaktiga parametrar, men resultatet avslöjar ändå tydligt en sjuk artär.

    De identifierade parametrarna har också använts för att jämföra spänningstillst åndet i membranmodellen och in silico-artäreren. Spänningstillståndet har delats upp i en isotrop och en anisotrop komponent svarande mot, i huvudsak, den elastindominerade matrisen samt kollagenfibrerna. Resultatet visar en mycket god överensstämmelse för bägge komponenterna hos in silico-artärer med låg spänningsgradient genom väggen. Med ökande spänningsgradient försämras dock överensstämmelsen.

    Resultatet visar att den förslagna metoden är kapabel att identifiera adekvata parametrar och att förutsäga spänningskomponenterna i en frisk aorta.

    Delarbeten
    1. An in vivo parameter identification method for arteries: numerical validation for the human abdominal aorta
    Öppna denna publikation i ny flik eller fönster >>An in vivo parameter identification method for arteries: numerical validation for the human abdominal aorta
    2019 (Engelska)Ingår i: Computer Methods in Biomechanics and Biomedical Engineering, ISSN 1025-5842, E-ISSN 1476-8259, s. 426-441Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    A method for identifying mechanical properties of arterial tissue in vivo is proposed in this paper and it is numerically validated for the human abdominal aorta. Supplied with pressure-radius data, the method determines six parameters representing relevant mechanical properties of an artery. In order to validate the method, 22 finite element arteries are created using published data for the human abdominal aorta. With these in silico abdominal aortas, which serve as mock experiments with exactly known material properties and boundary conditions, pressure-radius data sets are generated and the mechanical properties are identified using the proposed parameter identification method. By comparing the identified and pre-defined parameters, the method is quantitatively validated. For healthy abdominal aortas, the parameters show good agreement for the material constant associated with elastin and the radius of the stress-free state over a large range of values. Slightly larger discrepancies occur for the material constants associated with collagen, and the largest relative difference is obtained for the in situ axial prestretch. For pathological abdominal aortas incorrect parameters are identified, but the identification method reveals the presence of diseased aortas. The numerical validation indicates that the proposed parameter identification method is able to identify adequate parameters for healthy abdominal aortas and reveals pathological aortas from in vivo-like data.

    Ort, förlag, år, upplaga, sidor
    Taylor & Francis, 2019
    Nyckelord
    In vivo, parameter identification, abdominal aorta, in silico, finite element method, validation
    Nationell ämneskategori
    Övrig annan teknik
    Identifikatorer
    urn:nbn:se:liu:diva-155056 (URN)10.1080/10255842.2018.1561878 (DOI)000466370800009 ()30806081 (PubMedID)2-s2.0-85062322494 (Scopus ID)
    Forskningsfinansiär
    Vetenskapsrådet, 21-2014-4165
    Tillgänglig från: 2019-03-11 Skapad: 2019-03-11 Senast uppdaterad: 2019-08-29Bibliografiskt granskad
  • 43.
    Gade, Jan-Lucas
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Stålhand, Jonas
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Thore, Carl-Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    An in vivo parameter identification method for arteries: numerical validation for the human abdominal aorta2019Ingår i: Computer Methods in Biomechanics and Biomedical Engineering, ISSN 1025-5842, E-ISSN 1476-8259, s. 426-441Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A method for identifying mechanical properties of arterial tissue in vivo is proposed in this paper and it is numerically validated for the human abdominal aorta. Supplied with pressure-radius data, the method determines six parameters representing relevant mechanical properties of an artery. In order to validate the method, 22 finite element arteries are created using published data for the human abdominal aorta. With these in silico abdominal aortas, which serve as mock experiments with exactly known material properties and boundary conditions, pressure-radius data sets are generated and the mechanical properties are identified using the proposed parameter identification method. By comparing the identified and pre-defined parameters, the method is quantitatively validated. For healthy abdominal aortas, the parameters show good agreement for the material constant associated with elastin and the radius of the stress-free state over a large range of values. Slightly larger discrepancies occur for the material constants associated with collagen, and the largest relative difference is obtained for the in situ axial prestretch. For pathological abdominal aortas incorrect parameters are identified, but the identification method reveals the presence of diseased aortas. The numerical validation indicates that the proposed parameter identification method is able to identify adequate parameters for healthy abdominal aortas and reveals pathological aortas from in vivo-like data.

  • 44.
    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
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Sjöström, Sören
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Mechanical and thermodynamical study of a macroscopically coherent phase transition.Case of the martensitic transformation1991Ingår i: Journal de Physique IV, ISSN 1155-4339, Vol. 1, s. C4-89-C4-94Artikel i tidskrift (Refereegranskat)
    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.

  • 45.
    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
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Sjöström, Sören
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Micromechanical simulation of a martensitic transformaation by Finite Elements1991Ingår i: Journal de Physique IV, ISSN 1155-4339, Vol. 1, s. C4-77-C4-82Artikel i tidskrift (Refereegranskat)
    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.

  • 46.
    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
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Sjöström, Sören
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Micromechanical simulation of martensitic transformation by Finite Elements1991Ingår i: Journal de Physique IV, ISSN 1155-4339, Vol. 1, s. C4-77-C4-82Artikel i tidskrift (Refereegranskat)
    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.

  • 47.
    Ganghoffer, J.F.
    et al.
    ICSI, 15, Rue Jean Starcky, BP 2478, 68057 Mulhouse Cedex, France.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    A micromechanical model of the martensitic transformation1998Ingår i: Mechanics of Materials, ISSN 0167-6636, Vol. 27, nr 3, s. 125-144Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A micromechanical model of the martensitic transformation at the grain scale has been established, considering the more specific case of ferrous alloys. The transformation proceeds through the formation of successive variants of the product phase within a unit cell representative of a grain; interactions between neighbouring grains are simulated by the choice of periodic boundary conditions. From a thermodynamical analysis, a selection rule for the order and orientation of the forming martensitic variants has been established, based on internal stresses anisotropy. These concepts have been implemented into a two-dimensional finite element simulation of the transformation, considering an elastoplastic behaviour of both parent and product phases. Morphological and crystallographical features of the transformation are considered: one variant consists of a thin layer of elements within the mesh that can form with four possible discrete orientations. Simulation results show the development of the plate pattern as a combination of the influence of both external load and internal stresses built during the progress of the transformation. These are related to global evolutions of transformation plasticity vs. transformation progress. Comparison with experiments show a similar form of the evolutions of the total strain; however, the model overestimates the strain levels. The possible reasons for this discrepancy are discussed.

  • 48.
    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
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    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
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    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 Elements1994Ingår i: Journal de Physique IV, ISSN 1155-4339, Vol. 4, s. C3-215-C3-220Artikel i tidskrift (Refereegranskat)
    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.

  • 49.
    Gibaud, Thomas
    et al.
    Université de Lyon, Lyon, France.
    Perge, Christophe
    Université de Lyon, Lyon, France.
    Lindström, Stefan B
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Taberlet, Nicolas
    Université de Lyon, UFR de Physique, Université Claude Bernard Lyon I, Lyon, France .
    Manneville, Sebastien
    Laboratoire de Physique, CNRS/UMR 5672, Ecole Normale Supérieure de Lyon, Université de Lyon, 46 allée d'Italie, 69007 Lyon, France.
    Multiple yielding processes in a colloidal gel under large amplitude oscillatory stress2016Ingår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 12, nr 6, s. 1701-1712Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fatigue refers to the changes in material properties caused by repeatedly applied loads. It has been widely studied for, e.g., construction materials, but much less has been done on soft materials. Here, we characterize the fatigue dynamics of a colloidal gel. Fatigue is induced by large amplitude oscillatory stress (LAOStress), and the local displacements of the gel are measured through high-frequency ultrasonic imaging. We show that fatigue eventually leads to rupture and fluidization. We evidence four successive steps associated with these dynamics: (i) the gel first remains solid, (ii) it then slides against the walls, (iii) the bulk of the sample becomes heterogeneous and displays solid-fluid coexistence, and (iv) it is finally fully fluidized. It is possible to homogeneously scale the duration of each step with respect to the stress oscillation amplitude sigma_0. The data are compatible with both exponential and power-law scalings with sigma_0, which hints at two possible interpretations of delayed yielding in terms of activated processes or of the Basquin law. Surprisingly, we find that the model parameters behave nonmonotonically as we change the oscillation frequency and/or the gel concentration.

  • 50.
    Grossmann, Oscar
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära.
    Lateral stability analysis of frames for civilianaircraft structures2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The fuselage of a civilian airplane is a quite complex structure build from slendermembers and panels. Slender members are essential to minimize the weight of theairplane. These slender structures are at risk of buckling due to high compressiveloads. The scope of this thesis is to evaluate the lateral stability of one of thesestructures, a curved beam later referred to as the frame. Three main factorsthat affect the lateral stability of the frame will be discussed: The effect of thesurrounding geometry, the load conditions and the initial curvature of the frame.A literature study was carried out to find current information and methodologiesregarding such structures. The most promising techniques were later implementedto evaluate the lateral stability of the frame.The results from the analysis indicate that the structures surrounding the frameare sufficiently stiff so they won’t deflect and rotate together with the frame whenit buckles laterally. The whole cross section of the frame was assumed to be a rigidbody in this thesis but the experience from the present work indicates that thismight be wrong. The stress distribution in the frame was seen as a combination oftwo different load cases, plane bending and pure compression. By analyzing theseload cases individually we found that for the pure compression case the criticalbuckling stress was lower than for the maximum stress level of the plane bendingcase. The effect of the initial curvature of the frame was evaluated for the planebending load case. The initial curvature increased the resistance to the lateralbuckling modes but had also local effects on the stability of the frame. The crosssection of the frame is of the type of an open channel and if one were to take theinitial curvature into consideration one would also have to make sure that the webdoesn’t buckle locally due to increased radial compressive stress in the web.It was found that the surrounding structures could be disregarded if one appliesfixed boundary conditions to the fastener line of the frame where it is connected tothe skin panel. Further evaluation of how the initial curvature affects the bucklingmode is needed but the results look promising.v

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