Adiabatic shear failure in brittle solids

Grady, D. E.

doi:10.1016/j.ijimpeng.2011.01.001

Cited by 40 publications

(7 citation statements)

References 40 publications

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“…These phenomena are relevant at the extremely high stresses and strain rates induced by shock loading. Further causes include the coalescence of dislocation loops under high shear stresses, as occurs upon quasi-static mechanical load 50 51 , and adiabatic shear, which is governed by elastic strain energy in brittle solids 52 . Arguably, both the high strain rate induced by impact loading, and the coalescence of defects and defect clusters formed during irradiation may play an important role in the amorphization process observed here.…”

Section: Resultsmentioning

confidence: 99%

Radiation endurance in Al2O3 nanoceramics

Ferré

Mairov

Ceseracciu

et al. 2016

Sci Rep

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The lack of suitable materials solutions stands as a major challenge for the development of advanced nuclear systems. Most issues are related to the simultaneous action of high temperatures, corrosive environments and radiation damage. Oxide nanoceramics are a promising class of materials which may benefit from the radiation tolerance of nanomaterials and the chemical compatibility of ceramics with many highly corrosive environments. Here, using thin films as a model system, we provide new insights into the radiation tolerance of oxide nanoceramics exposed to increasing damage levels at 600 °C –namely 20, 40 and 150 displacements per atom. Specifically, we investigate the evolution of the structural features, the mechanical properties, and the response to impact loading of Al2O3 thin films. Initially, the thin films contain a homogeneous dispersion of nanocrystals in an amorphous matrix. Irradiation induces crystallization of the amorphous phase, followed by grain growth. Crystallization brings along an enhancement of hardness, while grain growth induces softening according to the Hall-Petch effect. During grain growth, the excess mechanical energy is dissipated by twinning. The main energy dissipation mechanisms available upon impact loading are lattice plasticity and localized amorphization. These mechanisms are available in the irradiated material, but not in the as-deposited films.

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Section: Resultsmentioning

confidence: 99%

Radiation endurance in Al2O3 nanoceramics

Ferré

Mairov

Ceseracciu

et al. 2016

Sci Rep

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“…Following prior phase field analysis [Clayton, 2014c], the elastic shear modulus µ =Ĉ 66 degrades completely upon solid-state localization, consistent with (3.48) and [Clayton, 2016b]. The regularization length l and intrinsic surface energy are chosen to have magnitudes corresponding to those for fracture since failure accompanies amorphization in experiments and since widths of amorphous zones observed experimentally are on the order of a nanometer [Yan et al, 2009;Grady, 2011], similar in magnitude to the fracture process zone size. In particular, l is computed via (3.51), where here τ = µ/(2π) is the theoretical shear strength [Clayton, 2011].…”

Section: Materials Characteristicsmentioning

confidence: 81%

Finsler-geometric continuum mechanics and the micromechanics of fracture in crystals

Clayton

2016

J. Micromech. Mol. Phys.

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A continuum theory for the mechanical response of solid bodies subjected to potentially finite deformation is further developed and applied to solve several new problems in the context of the micromechanics of crystalline solids. The theory invokes concepts from Finsler differential geometry, and it provides a diffuse interface description of fracture surfaces. The director or internal state vector is associated with an order parameter describing degradation of the solid. Here, the deformation gradient between pseudo-Finsler reference and spatial configuration spaces is decomposed into a product of two terms, neither necessarily integrable to a vector field. The first is the recoverable elastic deformation, the second is the residual deformation attributed to changes in free volume in failure zones. The latter is restricted to spherical or isotropic symmetry; resulting Euler–Lagrange equations for mechanical and state variable equilibrium are derived. Metric tensors and volume elements depend on the internal state via a conformal transformation, i.e., Weyl scaling. This version of the theory is first applied to tensile fracture of magnesium. Analytical solutions demonstrate the model's capability to predict ductile versus brittle fracture depending on incorporation of Weyl scaling, with results aligned with molecular dynamics (MD) simulations. The second application is shear fracture in boron carbide: solutions depict weakening and tensile pressure in conjunction with structural collapse in shear transformation zones, as suggested by experiments, quantum mechanics, and/or MD simulations.

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“…To be noted, the real material should be elastic-plastic. Provided the velocity of stress-release (even the propagation velocity of the elastic-plastic interface) is significantly lower than the elastic wave velocity (Lee, 1967), including elasticity in this analysis does not greatly alter the fluxes of energy and momentum into the shear band region, especially at strain rate higher than 10 3 /s (Grady, 1992;Grady, 2011). Except for the very early time response, which is elastic, the accuracy of rigid-plastic solution suffices for present study.…”

Section: Governing Equationsmentioning

confidence: 99%

Collective evolution dynamics of multiple shear bands in bulk metallic glasses

Chen

Jiang

Dai

2013

International Journal of Plasticity

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The collective behavior of multiple shear bands was investigated under in situ four-point bending tests of a Zr-based bulk metallic glass (BMG) over a wide range of sample scales. The self-organization of shear band pattern, characterized by shear band spacing and shear offset, is observed with the variation of sample size and bend curvature, which presents significant size effect and tension-compression asymmetry. To unveil these fundamental behaviors, an analytical model for the evolution dynamics of multiple shear banding is developed for BMGs. In this model, both micro-structural evolution and pressure sensitivity are taken into account by introducing a new law for the stress softening of BMGs within the framework of continuum mechanics; the collective evolution of shear bands is regarded as the coupling result of the structural softening, the momentum diffusion, and the energy conservation. Applying the proposed theoretical model to the bending deformation of BMGs, the analytical solutions of shear band spacing, shear offset and failure strain are obtained. The fundamental behaviors of multiple shear bands are uncovered, in line with the experimental observations: notable scaling laws are found in the evolution of shear band spacing and shear offset, and the inhomogeneous size effect of plasticity is revealed by a transition from weak to strong size-dependence of failure strain with decreasing sample thickness. To be further, a competing map of shear band nucleation and propagation is established based on energy dissipation. The underlying mechanism of these size dependent behaviors of multiple shear bands in BMGs is found to be ascribed to the energy dissipation competition between the nucleation and propagation of shear bands.

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Adiabatic shear failure in brittle solids

Cited by 40 publications

References 40 publications

Radiation endurance in Al2O3 nanoceramics

Radiation endurance in Al2O3 nanoceramics

Finsler-geometric continuum mechanics and the micromechanics of fracture in crystals

Collective evolution dynamics of multiple shear bands in bulk metallic glasses

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