A chevron-notched bowtie micro-beam bend test for fracture toughness measurement of brittle materials

Cui, Fiona Yuwei; Vinci, Richard P.

doi:10.1016/j.scriptamat.2017.01.031

Cited by 18 publications

(5 citation statements)

References 13 publications

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“…A size-dependent shift of the BDT to lower temperatures was also found for the semiconductors GaAs [20] and Si [21,22]. The microcantilever testing technique introduced by Di Maio and Roberts [23] offers the great advantage of a local determination of fracture properties and fracture toughness of single phases [24][25][26][27][28], at interfaces [29,30] and grain boundaries [31][32][33]. The technique was further developed for testing of materials showing non-negligible plastic deformation by Wurster et al [34].…”

Section: Accepted Manuscriptmentioning

confidence: 97%

The brittle-ductile transition of tungsten single crystals at the micro-scale

et al. 2018

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The loading rate effect on the brittle-ductile transition temperatures of tungsten single crystals at the micro-scale was investigated by microcantilevers with a (100)[001] crack system. Specimens with a length to width to height of 15 µm / 4 µm / 6 µm were fabricated by focused ion beam milling. At low temperatures (-90 to -25 °C) the samples failed by brittle cleavage fracture, irrespective of the applied loading rate at a fracture toughness of 3.2 MPa•m 1/2 . With increasing temperatures up to 500 °C and depending on the applied loading rate, the fracture toughness increased and significant crack tip plasticity and dislocation-controlled microcleavage were observed by means of high resolution electron backscatter diffraction measurements performed after testing. With respect to macroscopic specimens, a shift of the brittle-ductile transition to lower temperatures and a significantly lower activation energy of the brittle-ductile transition of 0.36 eV were found. We explain this by the increase in flow stresses due to sample size effects.

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Section: Accepted Manuscriptmentioning

confidence: 97%

The brittle-ductile transition of tungsten single crystals at the micro-scale

et al. 2018

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“…for fracture toughness measurements is that the only parameter of import is the maximum load. Such samples are difficult to prepare on the microscale with sufficient accuracy, but notable progress was achieved recently [59][60][61]. However, it should be noted that the simple procedure for evaluating the fracture toughness of chevron-notched samples is only possible in materials without an R-curve behavior of the fracture resistance, so where the fracture toughness does not increase with crack extension.…”

Section: Ideally Brittle Crack Propagationmentioning

confidence: 99%

Fracture mechanics of micro samples: Fundamental considerations

2018

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• Fundamental concepts of fracture mechanics are revisited with respect to their applicability in miniaturized experiments • Stress state and notch sharpness in miniaturized samples need to be considered • For size independent fracture toughness values, sample sizes must obey relations to the microstructure and fracture process zone • Different contributions to material toughness can be separated by appropriate experimental design

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“…The cohesive force to separate the bonds was then supposed to be dependent on interatomic force-displacement relationships, i.e., interatomic potential, and later associated with the surface energy per unit area. However, it has been only recently that those concepts have been addressed systematically, due to important advancements of in-situ observation of mechanical behavior at small scales [2][3][4][5][6][7][8][9][10][11] and developments of computational techniques such as molecular dynamics supported by improvement in computational power [12][13][14]. Sumigawa et al.…”

Section: Introductionmentioning

confidence: 99%

Strain energy density approach for brittle fracture from nano to macroscale and breakdown of continuum theory

Gallo

Hagiwara

Shimada

et al. 2019

Theoretical and Applied Fracture Mechanics

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In contrast to the great success at the macroscale, fracture mechanics theory fails to describe the fracture at a critical size of several nanometers due to the emerging effect of atomic discreteness with decreasing material size. Here, we propose a novel formulation for brittle fracture, from macro-to even atomic scales, based on extended strain energy density, and give an insight into the breakdown of continuum theory. Numerical experiments based on molecular statistics (MS) simulations are conducted on single-edge cracked samples made of silicon while varying the size until few nanometers, and loaded under mode I. The strain energy density is then defined as a function of the interatomic potential and averaged over the fracture process zone. Finally, by using an attenuation function, the atomic strain energy density gradient is homogenized to allow a comparison between the continuum and discrete formulation. Results show that the fracture process zone is scale independent, confirming that the ideal brittle fracture is ultimately governed by atomic bond-breaking. A singular stress field according to continuum fracture mechanics is still also present. However, when the singular stress field length (distance from the crack tip at which the stress deviates 5% from the theoretical field of r 0.5) is in the range of 4-5 times the fracture process zone, continuum fracture mechanics fails to describe the fracture, i.e., the breakdown of continuum theory. The new formulation, instead, goes well beyond that limit.

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A chevron-notched bowtie micro-beam bend test for fracture toughness measurement of brittle materials

Cited by 18 publications

References 13 publications

The brittle-ductile transition of tungsten single crystals at the micro-scale

The brittle-ductile transition of tungsten single crystals at the micro-scale

Fracture mechanics of micro samples: Fundamental considerations

Strain energy density approach for brittle fracture from nano to macroscale and breakdown of continuum theory

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