The formation of fracture process zones in polygranular graphite as a precursor to fracture

Nakhodchi, Soheil; Smith, David J.; Flewitt, Peter E J

doi:10.1007/s10853-012-6785-4

Cited by 15 publications

(12 citation statements)

References 35 publications

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“…The structural integrity of quasi-brittle materials, such as graphite [1][2][3], ceramic composites [4] and bone and bone replacements [5], is commonly assessed with the conservative assumption of brittle fracture (e.g. [6,7]).…”

Section: Introductionmentioning

confidence: 99%

“…During the fracture of a partially cracked component that is fabricated from a quasi-brittle material, a fracture process zone develops due to distributed microcracking ahead of the crack tip [2,13]. The extent of the fracture process zone dictates the magnitude of the deviation of the component's deformation and fracture behaviour from that predicted by linear elastic analysis.…”

Section: Introductionmentioning

confidence: 99%

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Three-dimensional crack observation, quantification and simulation in a quasi-brittle material

et al. 2013

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To investigate the fracture behaviour of polygranular graphite (a quasi-brittle material), crack propagation in a short bar chevron notched specimen was studied by synchrotron X-ray computed tomography combined with digital volume correlation. Displacements were measured within the loaded test specimen, particularly the three-dimensional (3-D) profile of crack opening displacement. Analysis of the 3-D displacement field confirmed the existence of distributed damage in a fracture process zone, which significantly increased the effective crack length. Finite element simulations affirmed that the measured crack opening profiles could be reproduced using a cohesive zone model, but not with a linear elastic analysis. Comparing the simulation to the experimental results, it was deduced that the critical strain energy release rate varied across the crack front, i.e. the fracture toughness is constraint-dependent. This is proposed to be a general characteristic of quasi-brittle materials.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Three-dimensional crack observation, quantification and simulation in a quasi-brittle material

et al. 2013

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“…Crack growth and fracture in brittle and quasi-brittle graphite materials have been investigated in the past since 1970 by several researchers under different loading conditions at various temperatures (Ayatollahi and Aliha, 2008;Bruno and Latella, 2006;Etter et al, 2004;Jae et al, 2004;Lomakin et al, 1975;Mostafavi and Marrow, 2012;Mostafavi et al, 2013;Nakhodchi et al, 2013;Sato et al, 1981;Shi et al, 2008;Yamauchi et al, 2001). Such fracture investigations include mainly mode I, mixed mode I/II and pure mode II loading conditions at room and elevated temperatures.…”

Section: Introductionmentioning

confidence: 99%

Strain energy density to assess mode II fracture in U-notched disk-type graphite plates

Torabi

Berto

2014

International Journal of Damage Mechanics

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The brittle fracture criterion, namely the strain energy density (SED) over a control volume, which embraces the notch edge, is utilized in the present research to assess the experimentally obtained fracture loads of several U-notched Brazilian disk (UNBD) specimens made of a type of commercial graphite under pure mode II loading. The results show that the SED criterion could successfully predict the fracture loads of graphite specimens for different notch tip radii with an average discrepancy of about ±10%. It is proved in this investigation that not only the SED criterion works well on brittle fracture of notched graphite components under pure mode I, mixed mode I/II and pure mode III loading conditions, but also under pure mode II loading

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“…Additionally, Etter et al [8] evaluated the mode I fracture toughness of polycrystalline graphite by employing a single-edge cracked beam specimen. Dealing with theoretical and experimental studies on fracture toughness of graphite materials, one can refer to Ayatollahi and Aliha [9], Mostafavi and Marrow [10,11], Mostafavi et al [12][13][14], and Nakhodchi et al [15].…”

Section: Introductionmentioning

confidence: 99%

Notch Fracture Toughness Evaluation for a Brittle Graphite Material

Torabi

Berto

2014

Matls. Perf. Charact.

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First, several disc-type test samples weakened by a central bean-shaped slit with two U-shaped ends, called U-notched Brazilian disc (UNBD) specimens, made of commercial graphite, were prepared. Four notch tip radii were considered in the tests. Then, a monotonic compressive load was diametrally applied to each sample along the slit, resulting in pure mode I loading. After sudden fracture, the fracture loads were recorded and converted into the corresponding values of the notch fracture toughness (NFT) K Iq,c . The main advantage of the UNBD specimen is that the NTF test can be easily conducted without using complicated fixtures. The well-established brittle fracture model, namely the strain energy density (SED) over a specified control volume, which embraces the notch edge, was employed to estimate the fracture loads theoretically. A good agreement was found between experimental and theoretical results. Under Mode I loading, the SED and the NFT are linked by a simple relationship providing a powerful tool for the fracture assessment of different specimens and structural components weakened by notches.

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The formation of fracture process zones in polygranular graphite as a precursor to fracture

Cited by 15 publications

References 35 publications

Three-dimensional crack observation, quantification and simulation in a quasi-brittle material

Three-dimensional crack observation, quantification and simulation in a quasi-brittle material

Strain energy density to assess mode II fracture in U-notched disk-type graphite plates

Notch Fracture Toughness Evaluation for a Brittle Graphite Material

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