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| 2. |
- Forsberg, K., et al.
(author)
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Theory of fission gas release in a growing grain
- 2001
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In: 16th International Conference on Structural Mechanics in Reactor Technology (SMIRT-16), Washington D.C., USA, 12-17 August 2001.. - 9781510816992
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Conference paper (peer-reviewed)
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| 3. |
- Jernkvist, Lars Olof, et al.
(author)
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A Numerical Model for Delayed Hydride Cracking of Zirconium Alloy Cladding Tubes
- 2007
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In: SMiRT 19 Transactions;C01/3. - : International Association for Structural Mechanics in Reactor Technology.
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Conference paper (other academic/artistic)abstract
- An integrated numerical model for hydride-induced failure of zirconium alloys is presented. The model solves the time-dependent and interconnected problems of temperature- and stress-directed diffusion of hydrogen, metal-hydride phase transformation, stress-directed hydride orientation, hydrogen-induced expansion and fracture within a two- dimensional finite element framework. The finite element method allows representation of arbitrary two-dimensional geometries and thermo-mechanical loading conditions. The model has a wide range of application, but is intended primarily for analyses of delayed hydride cracking in cladding tubes of light water reactor nuclear fuel rods.
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| 4. |
- Jernkvist, Lars Olof, et al.
(author)
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Modeling stress and temperature history effects on the initiation of hydride cracks at blunt flaws in Zr-2.5%Nb pressure tubes
- 2013
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Conference paper (other academic/artistic)abstract
- We study initiation of hydride induced cracks in Zr-2.5%Nb CANDU reactor pressure tubes, containing blunt notches and exposed to temperature cycles by use of a novel computational model. The model uses a continuum description of the two-phase (alpha-phase metal plus delta-phase hydride) material, and solves the multi-field partial differential equations for temperature- and stress-directed hydrogen diffusion together with mechanical equilibrium in a finite element setting. Point-kinetics models are used for metal-hydride phase transformation and stress-directed orientation of hydrides, while a cohesive zone fracture model caters for initiation and propagation of cracks. Our calculations show that the propensity for crack initiation through hydride fracture at the notch during an overload event depends on the preceding histories of stress and temperature, and in particular, on the number of ratcheting thermal cycles experienced by the hydrided material. The calculated results agree favorably with experiments reported in open literature.
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| 5. |
- Jernkvist, Lars Olof, et al.
(author)
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Multi-field modeling of hydrogen transport and fracture in group 4 transition metals
- 2012
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In: Proceedings of the International Hydrogen Conference (IHC 2012): Hydrogen-Materials Interactions. - : ASME Press. - 9780791860298 ; , s. 717-726
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Conference paper (other academic/artistic)abstract
- This work deals with a computational model for hydrogen transport, hydrogen induced deformation, embrittlement and fracture in hydride forming metals, notably Ti and Zr. The model uses a continuum description of the two-phase (alpha-phase metal plus delta-phase hydride) material, and solves the multi-field partial differential equations for temperature- and stress-directed hydrogen diffusion together with mechanical equilibrium in a three-dimensional finite element setting. Point-kinetics models are used for metal-hydride phase transfor¬mation and stress-directed orientation of hydrides, while a cohesive zone fracture model caters for initiation and propagation of cracks. The model as a whole is versatile and can be used to study a wide range of problems and conditions involving transport of hydrogen by directed diffusion in combination with hydride precipitation and fracture. The applicability of the model is demon-strated by simulations of fracture tests on a hydrogen-charged Zr-Nb alloy.
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| 7. |
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| 8. |
- Knudsen, Jacob, et al.
(author)
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Dynamic stability of weakly damped oscillators with elastic impacts and wear
- 2003
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In: Journal of Sound and Vibration. - : Academic Press. - 0022-460X .- 1095-8568. ; 263:1, s. 175-204
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Journal article (peer-reviewed)abstract
- The dynamics of non-linear oscillators comprising of a single-degree-of-freedom system and beams with elastic two-sided amplitude constraints subject to harmonic loads is analyzed. The beams are clamped at one end, and constrained against unilateral contact sites near the other end. The structures are modelled by a Bernoulli-type beam supported by springs using the finite element method. Rayleigh damping is assumed. Symmetric and elastic double-impact motions, both harmonic and sub-harmonic, are studied by way of a Poincaré mapping that relates the states at subsequent impacts. Stability and bifurcation analyses are performed for these motions, and domains of instability are delineated. Impact work rate, which is the rate of energy dissipation to the impacting surfaces, is evaluated and discussed. In addition, an experiment conducted by Moon and Shaw on the vibration of a cantilevered beam with one-sided amplitude constraining stop is modelled. Bifurcation observed in the experiment could be captured
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