20 research outputs found
Mechanical characterisation of a fibre reinforced oxide/oxide ceramic matrix composite
Monotonic tension, fatigue and creep experiments were conducted on an oxide/oxide ceramic matrix composite over the range of temperature 20–1200 °C. The role of continuous fibre reinforcement, differential thermal expansion, stress redistribution interactions between fibres and matrix and the influence of inherent processing defects are all considered when describing the deformation and ultimate mechanical failure of these systems
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Results and implications of the EBR-II inherent safety demonstration tests
On April 3, 1986 two milestone tests were conducted in Experimental Breeder Reactor-2 (EBR-II). The first test was a loss of flow without scram and the second was a loss of heat sink without scram. Both tests were initiated from 100% power and in both tests the reactor was shut down by natural processes, principally thermal expansion, without automatic scram, operator intervention or the help of special in-core devices. The temperature transients during the tests were mild, as predicted, and there was no damage to the core or reactor plant structures. In a general sense, therefore, the tests plus supporting analysis demonstrated the feasibility of inherent passive shutdown for undercooling accidents in metal-fueled LMRs. The results provide a technical basis for future experiments in EBR-II to demonstrate inherent safety for overpower accidents and provide data for validation of computer codes used for design and safety analysis of inherently safe reactor plants
Evaluating the efficacy of alternative small scale test methodologies in deriving the mechanical properties of additive manufactured materials
With the continuous drive of the aerospace industry to implement additive manufactured (AM) components into the next generation of aero-engines, to benefit from the near net shape and weight saving potential that the technology has to offer, the requirement to understand their mechanical performance is also rising in parallel. This is further complicated by the highly localised and transient micro/macro structures that AM produced parts typically possess, raising a question mark over the suitability of more traditional mechanical test approaches where the bulk properties are heavily influenced by the presence of a single defect. As such, alternative experimental approaches, capable of establishing the properties of smaller more intricate structures and geometrically representative microstructures and cross sections, needs to be considered for process parameter down-selection. This paper will explore the suitability of several alternative mechanical test methodologies in characterising the mechanical behaviour of a nickel based superalloy, Inconel 718 (IN718), produced by laser powder bed fusion (LPBF), and establish which results correlate most favourably to those generated through more conventional means. For the first time, results will be presented from several mechanical test methodologies including small punch, shear punch, hardness, nano-indentation and profilometry based indentation plastometry experiments; a set of mechanical test approaches that have yet to be directly compared and discussed in a single study on an additively manufactured material. Findings will be supported by advanced microscopy in the form of field emission SEM and crystallographic texture maps produced through electron back-scattered diffraction