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Descripción
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| The objective of this work is to show some new and original methods to determine the fracture toughness in brittle metals. In this case the analysis was performed for tungsten, which is considered a suitable material for plasma facing applications in the future fusion reactors. However, its structural use is compromised due to its inherent brittleness. Therefore, to improve this critical feature it is relevant to accurately measure its fracture toughness independent of geometrical parameters. The most common methods to produce cracks such as fatigue, indentation microfracture or electro-discharge machining cannot be used here because they are difficult to apply, do not produce reproducible cracks or induce extended thermal damage in the material. For these reasons, in a first part of this work four experimental methods, that gradually approach a crack-like notch, were compared to determine the effect of the notch root radius on the measured fracture toughness of a nanostructured bulk tungsten material. Three-point bending tests were performed on these four types of specimens with notches introduced with: a classical diamond disc, a diamond wire, a razor blade and an ultra-short pulsed laser. The results showed that the best alternative is to introduce a notch with a femtosecond pulsed laser. This method, which produces crack-like notches without thermal damage, possesses good reproducibility, high accuracy and reliable fracture toughness. It was previously used on ceramics but there is no evidence of its use on metals. Additionally, the ultra-short pulsed laser was used to introduce notches in tungsten foils of 0.1 mm thickness to perform in situ tensile tests inside a scanning electron microscope and determine the fracture toughness. Two types of geometries were also produced in the foils: single-edge and double-edge notched specimens. The introduction of the notches is a challenging task because of the reduced size of the samples and their slenderness. Single-edge notched specimens, easier to produce, were not suitable to provide accurate fracture toughness since the slenderness and the non-symmetric geometry resulted in complex stresses and momentum apart from the uniaxial tensile being applied to the sample. Double-edge notched specimens, however, produced accurate fracture toughness results, although introducing both notches aligned at both sides of the specimens involves higher complications during the notching process. | |
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Internacional
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Si |
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Nombre congreso
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2015 MRS Fall Meeting & Exhibit |
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Tipo de participación
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960 |
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Lugar del congreso
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Boston, USA |
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Revisores
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Si |
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ISBN o ISSN
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0000-0000 |
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DOI
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Fecha inicio congreso
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29/11/2015 |
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Fecha fin congreso
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04/12/2015 |
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Desde la página
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1 |
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Título de las actas
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Proceedings of the 2015 MRS Fall Meeting & Exhibit |