Modelling thermo-mechanical response of metal canister disposed in engineered barrier systems
The main objective of this thesis is to describe and implement a rate-dependent (viscoplastic) constitutive equations for copper based canister using a single internal state variable and use it for modelling disposal schemes subjected to shear conditions. The model of Bodner and Partom (BP) is consi...
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| Tipo de recurso: | tesis doctoral |
| Fecha de publicación: | 2022 |
| País: | España |
| Institución: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/363413 |
| Acceso en línea: | https://hdl.handle.net/2117/363413 https://dx.doi.org/10.5821/dissertation-2117-363413 |
| Access Level: | acceso abierto |
| Palabra clave: | Àrees temàtiques de la UPC::Enginyeria civil |
| Sumario: | The main objective of this thesis is to describe and implement a rate-dependent (viscoplastic) constitutive equations for copper based canister using a single internal state variable and use it for modelling disposal schemes subjected to shear conditions. The model of Bodner and Partom (BP) is considered for this purpose (Bodner & Partom, 1975). To evaluate the copper's response to variations in strain rate throughout a temperature range, this model uses viscoplastic constitutive equations based on a single internal state variable that is a function of plastic work. The BP constitutive model has been implemented in CODE_BRIGHT computer code (DIT-UPC, 2021; Olivella et al., 1994; Olivella et al., 1996). The constitutive equation is verified against existing results and its validation is carried out by assessing the capability to reproduce experiments. For verification, the stress-strain response of a bar under uniaxial tensile conditions at a constant velocity was simulated with CODE_BRIGHT and the results compared with the solution obtained from Stealth Finite Difference Code and the semi-analytical solutions. In addition, it is analyzed the reaction of a canister installed inside an engineered barrier which undergoes hydration and swelling until it reaches full saturation prior to shearing. The implemented elasto-viscoplastic model actually represents the behavior of the canister in yielding conditions. Although the canister is very stiff and strong compared to the clay components where it will be emplaced in a clay volume shear deformations occurring on the engineered barrier system (EBS) will have an impact on the canister (Börgesson, 1986). Finally, a repository of nuclear spent fuel is analyzed under extreme conditions as it is a long-life system and has to resist all types of environmental conditions, for instance earthquakes and glaciations. After model implementation and verification in CODE BRIGHT this program has been used to model the canister-clay shear tests in 2D and 3D. In the Mock-up scale and Full-scale in 2D and 3D models, a comparison between the total stress method (mechanical analysis only) and the effective stress method (hydro-mechanical analysis) has been investigated. Experimental results from a canister-clay shear test (Börgesson, 1986) have been compared to the findings of the numerical model using CODE BRIGHT. Sensitivity analysis on viscosity for total stress calculations and permeability for effective stress calculations have been performed in the Mock-up scale and Full-scale. In the canister-clay shear test, a mesh sensitivity analysis and also a comparison between the updated mesh (Lagrangian method) and the fixed mesh method have been carried out. Finally, in two and three dimensions, the simulation of canister-clay shear tests based on impact of discontinuity (the discontinuity is in the rock and due to it, there is shearing in canister-rock system), as well as sensitivity analysis of parameters and mesh in mechanical and a coupled hydro-mechanical analysis, have been investigated. |
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