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- Leidermark, Daniel, 1980-
(författare)
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Crystal plasticity and crack initiation in a single-crystal nickel-base superalloy : Modelling, evaluation and applications
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this dissertation the work done in the projects KME-410/502 will be presented.The overall objective in these projects is to evaluate and develop tools for designingagainst fatigue in single-crystal nickel-base superalloys in gas turbines. Experimentshave been done on single-crystal nickel-base superalloy specimens in order toinvestigate the mechanical and fatigue behaviour of the material. The constitutivebehaviour has been modelled and veried by FE-simulations of the experiments.Furthermore, the microstructural degradation during long-time ageing has been investigatedwith respect to the material's yield limit. The eect has been includedin the constitutive model by lowering the resulting yield limit. Moreover, the fatiguecrack initiation of a component has been analysed and modelled by using acritical plane approach in combination with a critical distance method. Finally, asan application, the derived single-crystal model was applied to all the individualgrains in a coarse grained specimen to predict the dispersion in fatigue crack initiationlife depending on random grain distributions.This thesis is divided into three parts. In the rst part the theoretical framework,based upon continuum mechanics, crystal plasticity, the critical plane approachand the critical distance method, is derived. This framework is then used in thesecond part, which consists of six included papers. Finally, in the third part, detailsof the used numerical procedures are presented.
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| 2. |
- Leidermark, Daniel, 1980-
(författare)
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Modelling of constitutive and fatigue behaviour of a single-crystal nickel-base superalloy
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this licentiate thesis the work done in the project KME410 will be presented. The overall objective of this project is to evaluate and develop tools for designing against fatigue in single-crystal nickel-base superalloys in gas turbines. Experiments have been done on single-crystal nickel-base superalloy specimens in order to investigate the mechanical behaviour of the material. The constitutive behaviour has been modelled and verified by simulations of the experiments. Furthermore, the microstructural degradation during long-time ageing has been investigated with respect to the component’s yield limit. The effect has been included in the constitutive model by lowering the resulting yield limit. Finally, the fatigue crack initiation of a component has been analysed and modelled by using a critical plane approach.This thesis is divided into three parts. In the first part the theoretical framework, based upon continuum mechanics, crystal plasticity and the critical plane approach, is derived. This framework is then used in the second part, which consists of three included papers. Finally, in the third part, details are presented of the used numerical procedures.
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| 3. |
- Leidermark, Daniel, 1980-, et al.
(författare)
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The effect of random grain distributions on fatigue crack initiation in a notched coarse grained superalloy specimen
- 2012
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Ingår i: Computational materials science. - : Elsevier. - 0927-0256 .- 1879-0801. ; 51:1, s. 273-280
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Tidskriftsartikel (refereegranskat)abstract
- Coarse grained superalloys are of large interest in high temperature applications, and can be found in e.g.gas turbine components, where great care must be given with respect to high temperature fatigue. Due tothe large grain size, the material behaviour at e.g. sharp notches cannot be considered homogeneous. As aconsequence, the fatigue behaviour is likely to expose a large variation. In order to numerically investigatethis variation, a Monte Carlo analysis has been carried out by 100 FE-simulations of notched specimens,where placements and orientations of the grains were randomised. Furthermore, each grain wasmodelled as a unique single-crystal, displaying both anisotropic elastic and plastic behaviour and tension/compression asymmetry. The effect of randomness was investigated by the obtained dispersion infatigue crack initiation life. It was concluded that the fatigue life behaviour of coarse grained nickel-basesuperalloys may show a considerable variation, which cannot be captured by one single deterministicanalysis based on data for a homogenised material. Furthermore, the dispersion is of such a magnitudethat it needs to be taken into account in industrial applications where highly stressed coarse grainedmaterials are used.
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