The role of dislocations in the growth of nanosized voids in ductile failure of metals

Meyers, Marc A.; Traiviratana, Sirirat; Lubarda, Vlado A.; Benson, David J.; Bringa, Eduardo M.

doi:10.1007/s11837-009-0025-7

Cited by 66 publications

(38 citation statements)

References 57 publications

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“…14͑c͔͒. Similar to the void growth within a single crystal, 5,20 the early stage of the void growth at GBs also involves crystal plasticity as suggested previously. 37 However, the crystal plasticity can be reduced as local stress FIG.…”

Section: -6supporting

confidence: 55%

“…Given the importance of grain boundaries ͑GBs͒, considerable efforts including MD simulations have been dedicated to the mechanical or physical properties of different nanostructures under nonshock conditions. [4][5][6][7][8][9][10][11][12][13][14][15] MD is also a proven tool in modeling shock response and providing valuable physical insights. [16][17][18][19][20][21][22][23][24] However, MD shock simulations of defective solids [21][22][23]25 are few and focus on nanocrystalline metals with random GBs.…”

Section: Introductionmentioning

confidence: 99%

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Anisotropic shock response of columnar nanocrystalline Cu

Luo

Germann

Desai

et al. 2010

Journal of Applied Physics

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We perform molecular dynamics simulations to investigate the shock response of idealized hexagonal columnar nanocrystalline Cu, including plasticity, local shear, and spall damage during dynamic compression, release, and tension. Shock loading ͑one-dimensional strain͒ is applied along three principal directions of the columnar Cu sample, one longitudinal ͑along the column axis͒ and two transverse directions, exhibiting a strong anisotropy in the response to shock loading and release. Grain boundaries ͑GBs͒ serve as the nucleation sites for crystal plasticity and voids, due to the GB weakening effect as well as stress and shear concentrations. Stress gradients induce GB sliding which is pronounced for the transverse loading. The flow stress and GB sliding are the lowest but the spall strength is the highest, for longitudinal loading. For the grain size and loading conditions explored, void nucleation occurs at the peak shear deformation sites ͑GBs, and particularly triple junctions͒; spall damage is entirely intergranular for the transverse loading, while it may extend into grain interiors for the longitudinal loading. Crystal plasticity assists the void growth at the early stage but the growth is mainly achieved via GB separation at later stages for the transverse loading. Our simulations reveal such deformation mechanisms as GB sliding, stress, and shear concentration, GB-initiated crystal plasticity, and GB separation in nanocrystalline solids under shock wave loading.

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Section: -6supporting

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Anisotropic shock response of columnar nanocrystalline Cu

Luo

Germann

Desai

et al. 2010

Journal of Applied Physics

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“…Thus, this mechanism is responsible for void nucleation at the faster strain rates. Such voids are known to grow in shear [43] to relieve the constraints by a grain or a group of surrounding grains. Since the grains near the center of the specimen are the most constrained, the voids at the mid-film plane will grow and coalesce faster.…”

Section: Damage Evolution As a Function Of Strain Ratementioning

confidence: 99%

Strain rate sensitivity of nanocrystalline Au films at room temperature

et al. 2010

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Dimitrios, "Strain rate sensitivity of nanocrystalline Au films at room temperature" (2010) AbstractThe effect of strain rate on the inelastic properties of nanocrystalline Au films was quantified with 0.85 and 1.76 lm free-standing microscale tension specimens tested over eight decades of strain rate, between 6 Â 10 À6 and 20 s À1 . The elastic modulus was independent of the strain rate, 66 ± 4.5 GPa, but the inelastic mechanical response was clearly rate sensitive. The yield strength and the ultimate tensile strength increased with the strain rate in the ranges 575-895 MPa and 675-940 MPa, respectively, with the yield strength reaching the tensile strength at strain rates faster than 10 À1 s À1 . The activation volumes for the two film thicknesses were 4.5 and 8.1 b 3 , at strain rates smaller than 10 À4 s À1 and 12.5 and 14.6 b 3 at strain rates higher than 10 À4 s À1 , while the strain rate sensitivity factor and the ultimate tensile strain increased below 10 À4 s À1 . The latter trends indicated that the strain rate regime 10 À5 -10 À4 s À1 is pivotal in the mechanical response of the particular nanocrystalline Au films. The increased rate sensitivity and the reduced activation volume at slow strain rates were attributed to grain boundary processes that also led to prolonged (5-6 h) and significant primary creep with initial strain rate of the order of 10 À7 s À1 .

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“…In metals at high tensile pressures, the critical void size for plastic cavitation may be in the nanoscale, in which case plastic cavitation occurs by the emission of discrete dislocation loops. [21][22][23][24] Void nucleation in metals under shock loading has been extensively studied by means of molecular dynamics. [25][26][27][28][29][30] While these studies are remarkable for the fidelity and insights that they afford, including the role of inclusions, second-phase particles, dislocations, grain boundaries, and other microstructural features, they often fail to supply an analytical description of nucleation rates that can be effectively integrated into a larger multiscale framework.…”

Section: Introductionmentioning

confidence: 99%

Nanovoid nucleation by vacancy aggregation and vacancy-cluster coarsening in high-purity metallic single crystals

2011

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A numerical model to estimate critical times required for nanovoid nucleation in high-purity aluminum single crystals subjected to shock loading is presented. We regard a nanovoid to be nucleated when it attains a size sufficient for subsequent growth by dislocation-mediated plasticity. Nucleation is assumed to proceed by means of diffusion-mediated vacancy aggregation and subsequent vacancy cluster coarsening. Nucleation times are computed by a combination of lattice kinetic Monte Carlo simulations and simple estimates of nanovoid cavitation pressures and vacancy concentrations. The domain of validity of the model is established by considering rate-limiting physical processes and theoretical strength limits. The computed nucleation times are compared to experiments suggesting that vacancy aggregation and cluster coarsening are feasible mechanisms of nanovoid nucleation in a specific subdomain of the pressure-strain rate-temperature space.

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The role of dislocations in the growth of nanosized voids in ductile failure of metals

Cited by 66 publications

References 57 publications

Anisotropic shock response of columnar nanocrystalline Cu

Anisotropic shock response of columnar nanocrystalline Cu

Strain rate sensitivity of nanocrystalline Au films at room temperature

Nanovoid nucleation by vacancy aggregation and vacancy-cluster coarsening in high-purity metallic single crystals

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