Crack-Tip Plasticity and Quasi-Brittle Fracture of Single Crystals

Hirsch, P. B.

doi:10.1007/978-1-4899-1441-5_1

Cited by 4 publications

(9 citation statements)

References 37 publications

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“…Under some conditions, compressive stress is formed from some dislocations around a crack tip, which suppresses crack propagation and thus increases the fracture toughness (Figure 10) [101]. This is called crack-tip shielding by dislocations [101][102][103][104][105][106]. In the recent experimental reports [19,21] of dislocation toughening, it was suggested that pre-existing dislocations themselves shield the crack tip, resulting in an increase in fracture toughness.…”

Section: Toughening Mechanism By Pre-existing Dislocationsmentioning

confidence: 99%

“…In the recent experimental reports [19,21] of dislocation toughening, it was suggested that pre-existing dislocations themselves shield the crack tip, resulting in an increase in fracture toughness. However, from many other pre-existing dislocations, tensile stress results around a crack tip, which accelerates crack propagation and thus decreases the fracture toughness [104,105]. This is called crack-tip anti-shielding by dislocations [102,104,105].…”

Section: Toughening Mechanism By Pre-existing Dislocationsmentioning

confidence: 99%

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Possibility of High Ionic Conductivity and High Fracture Toughness in All-Dislocation-Ceramics

Yasui,

Hamamoto

2024

Materials

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Based on the results of numerical calculations as well as those of some related experiments which are reviewed in the present paper, it is suggested that solid electrolytes filled with appropriate dislocations, which is called all-dislocation-ceramics, are expected to have considerably higher ionic conductivity and higher fracture toughness than those of normal solid electrolytes. Higher ionic conductivity is due to the huge ionic conductivity along dislocations where the formation energy of vacancies is considerably lower than that in the bulk solid. Furthermore, in all-dislocation- ceramics, dendrite formation could be avoided. Higher fracture toughness is due to enhanced emissions of dislocations from a crack tip by pre-existing dislocations, which causes shielding of a crack tip, energy dissipation due to plastic deformation and heating, and crack-tip blunting. All-dislocation-ceramics may be useful for all-solid-state batteries.

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Section: Toughening Mechanism By Pre-existing Dislocationsmentioning

confidence: 99%

Section: Toughening Mechanism By Pre-existing Dislocationsmentioning

confidence: 99%

Possibility of High Ionic Conductivity and High Fracture Toughness in All-Dislocation-Ceramics

Yasui,

Hamamoto

2024

Materials

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“…98 Dislocation motion around crack tips can shield the crack tip and enhance fracture toughness by forming a plastic zone. [105][106][107][108][109][110][111][112][113]117,200 In metals, dislocations can typically be nucleated at crack tips, 105 which ensures the supply of dislocations. In ceramics, dislocation nucleation is generally not observed (see Figure 7C vs. D), although it was documented, for example, for low crack velocities.…”

Section: Limitation By the Necessity Of Nucleationmentioning

confidence: 99%

60 years of dislocations in ceramics: A conceptual framework for dislocation mechanics in ceramics

Porz

2022

Int J Ceramic Engine & Sci

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High‐tech ceramics are typically engineered by controlling point defects and interfaces while one‐dimensional dislocations have found much less attention so far. Nevertheless, their impact on almost any functional property and the sudden ease to fabricate them with novel synthesis methods, such as rapid densification, brings spotlight attention to dislocations as design dimension. Although the typical brittleness of ceramics insinuates the irrelevance of dislocations for mechanical behavior, abundant literature is spread over materials, decades, and disciplines, however, often unconnected. Here, a conceptual framework for dislocation mechanics in ceramics separated into five logical aspects, (1) fundamental mobility, (2) obstacles to motion, (3) limitation by necessity of nucleation, (4) motion complexity, and (5) avoidance of competing mechanisms, brings oversight into the complex behavior. In consequence, quicker identification of the limiting step allows to estimate the potential involved more precisely and to identify open research questions with greater ease. An introduction to dislocations and the functionality involved, a look back over the last six decades, and highlights of open question are dedicated to provide a framework and bridge the gap between the attached research fields.

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“…This has been used for Si, Ge, Al 2 O 3 , Mo single crystals (for reviews see Roberts et al 1993Roberts et al , 1994Hirsch 1995). When the fracture event is the nucleation of cracks ahead of the main shielded crack, as is the case for steels (Ritchie et al 1973), the condition is…”

Section: Discrete Dislocation Model For Bdtmentioning

confidence: 99%

“…These experimental studies supported by modelling demonstrate clearly that the BDT is a structure sensitive property. A recent review is given by Hirsch & Roberts (1996) and Hirsch (1995).…”

Section: Discrete Dislocation Model For Bdtmentioning

confidence: 99%

Modelling plastic zones and the brittle-ductile transition

Hirsch

Roberts

1997

Philosophical Transactions of the Royal Society of London. Seri

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Many crystalline solids fail by cleavage at low temperatures and by plastic processes at high temperatures. In the transition region, cleavage failure occurs at stresses increasing with increasing temperature, reflecting a decrease in yield stress and a consequent increase of plasticity around the crack tip. Crack tip plasticity blunts the crack and shields it through the compressive stresses in the plastic zone. This competition between cleavage and plastic flow can be modelled in terms of the generation (from a source), motion and interaction of dislocations moving on the slip plane containing the crack tip, obeying a velocity-stress-temperature law. Assumptions have to be made about the criterion for cleavage fracture and the density and strength of dislocation sources. While the temperature range and strain-rate sensitivity of the transition depend on the velocity law, the form of the transition (sharp or gradual) depends on spacing of the dislocation sources and thus the transition is structure sensitive. Static equilibrium arrays of discrete dislocations have also been modelled and these are compared with continuum plasticity models of the plastic zone.

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Crack-Tip Plasticity and Quasi-Brittle Fracture of Single Crystals

Cited by 4 publications

References 37 publications

Possibility of High Ionic Conductivity and High Fracture Toughness in All-Dislocation-Ceramics

Possibility of High Ionic Conductivity and High Fracture Toughness in All-Dislocation-Ceramics

60 years of dislocations in ceramics: A conceptual framework for dislocation mechanics in ceramics

Modelling plastic zones and the brittle-ductile transition

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