Mechanical testing and finite element simulation of laser-drilled TBC systems
| Autor: | Ebrahimzade Isfahani, Vahid |
|---|---|
| Přispěvatelé: | Singheiser, Lorenz, Krüger, Manja |
| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: | |
| Zdroj: | Aachen 1 Online-Ressource (125 Seiten) : Illustrationen, Diagramme (2018). doi:10.18154/RWTH-2019-07487 = Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2018 |
| DOI: | 10.18154/rwth-2019-07487 |
| Popis: | Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2018; Aachen 1 Online-Ressource (125 Seiten) : Illustrationen, Diagramme (2018). = Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2018 Cooling holes in gas turbine components prevent the superalloy from exposure to very high temperatures that could lead to degradation of the thermomechanical properties. There are around 100.000 cooling holes in a gas turbine, and if their quality is not sufficient, this might lead to a premature failure of the whole system. This is the main reason to optimize drilling of cooling holes. Recently, laser drilling has been used to drill such holes, since it provides a faster and more productive solution in comparison to conventional methods, such as electro discharge/chemical machining (EDM/ECM).The behavior of laser-drilled TBC systems under thermomechanical loading has not been studied in detail in literature, which is the focus of this PhD thesis. In the current work, as an initial step to assess laser drilling effects in the as-drilled state, flat specimens were drilled with long-pulsed and ultra-short pulsed laser set-ups, and a microstructural analysis was performed to permit selection of the best laser-drilling method. In an extension of the first test series, a second set of specimens was cyclic oxidized, in order to understand the effect of thermal load on TBC adherence in the vicinity of laser drilled holes. Specimens were drilled with long-pulsed laser sources (flash lamp and fiber laser) and with different drilling modes such as percussion as well as trepanation mode. As the third step, LCF tests of specimens undrilled and laser-drilled by flash lamp laser, trepanation mode, as well as ultra-short pulsed laser at two angles, 30° and 90°, were performed at 850°C with different mechanical strain ranges, 0.38% and 0.67%, in order to analyze the quality of laser drilling quality on the life time and failure mechanism. Additionally, Finite Element Method (FEM) simulations were performed to improve the understanding of the experimental observations of laser-drilled TBC coated superalloy under thermal loading conditions. 3D simulations were performed to study the influence of angle of the hole as well as recast layer on the stress distribution, in order to aid further optimization of laser drilling processes. 2D FEM simulations were also performed to do a sensitivity analysis studying the effect of coefficient of thermal expansion (CTE), creep rate, elastic moduli, and TGO thickness on the stress distribution, thereby validating the experimental results. Published by Aachen |
| Databáze: | OpenAIRE |
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