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- Leidermark, Daniel, et al.
(author)
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Thermomechanical fatigue life due to scatter in constitutive parameters
- 2021
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In: Computational materials science. - : Elsevier. - 0927-0256 .- 1879-0801. ; 198
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Journal article (peer-reviewed)abstract
- For critical component application, such as aerospace turbine rotors, it is imperative to be able to make accurate in-service material behaviour and component life predictions for both design and monitoring of component life. The development of such predictive capability is dependent on the quality of the experimental data from which the material parameters are derived. This paper shows the effect that scatter which may be present within experimental data, manifesting itself within the constitutive parameters derived from this data, has on the resulting fatigue crack initiation life of the nickel-based superalloy RR1000. Industrial relevance was added to this investigation by the use of flight representative thermomechanical fatigue loading cycles and state of the art material behaviour and fatigue crack initiation models used within the finite element simulations conducted. The effect of the scatter in to the modelling approach on the outcoming predictions is made via a Monte-Carlo analysis. This analysis consisted of running the same simulation several times, but with the experimentally determined and validated baseline constitutive parameters varied via correction factors built into the model, for each run via a singular value decomposition procedure. It was found that small scatter in has only a very localised scatter out effect on the crack initiation predictions under the flight representative loading.
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3. |
- Stekovic, Svjetlana, 1967-, et al.
(author)
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Towards the elaboration of the European Code of Practice for TMF crack growth
- 2016
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Conference paper (other academic/artistic)abstract
- In recent years, there has been an increasing interest towards the environmental impact of air travel. As a result, it is of vital importance to the European aviation industry to reduce the engine emissions. For this purpose, ACARE set new challenging targets aiming to reduce emissions, fuel consumption and raising temperature capabilities. This will ultimately be achieved by the introduction of novel engine design and new materials able to sustain complex loadings from take-off, cruise, descent and shut down. It is a prerequisite to understand the impact of such environments in current alloys.Specifically, Thermo-Mechanical Fatigue (TMF), which occurs at the rim of turbine discs, aerofoils and rear structures need to be assessed. At these locations, the harsh thermal transients during take-off and descent may cause the formation of cracks. A previous European project on TMF, which ended in 2005, has been successful at evaluating and addressing issues related to thermo-mechanical fatigue testing. This project led to the elaboration of a code of practice for TMF studies, which has been implemented by testing houses and equipment manufacturers worldwide. A European project has recently been awarded, under the umbrella of both `Horizon 2020' and Clean Sky 2, aiming to evaluate and model TMF crack initiation and growth.TMF crack growth (CG) methods are essential to demonstrate that structural components meet the certification requirements of being tolerant at handling damages and the presence of melt anomalies. They are also needed to assess remnant lives in cracked turbine components such as vanes. However, crack growth in TMF loading cycles cannot be currently reliably measured experimentally nor predicted by existing CG models. Therefore, isothermal propagation data are used to conservatively handle TMF effects, which can lead to over-designed components and loss of engine efficiency. Our project aims to address those deficiencies.
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