Void initiation in fcc metals: Effect of loading orientation and nanocrystalline effects

Bringa, Eduardo M.; Traiviratana, Sirirat; Meyers, Marc A.

doi:10.1016/j.actamat.2010.04.043

Cited by 165 publications

(102 citation statements)

References 75 publications

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“…Although this phenomenon was realized as early as 1949 by Tipper [1], and a complete account was given by Dodd and Bai [2], the atomistic mechanisms are still not completely understood. An analytical model based on shear and prismatic loops emission was proposed by Lubarda, et al [3] in 2004, followed by a considerable effort in MD simulations of void growth, which confirmed the emission of shear loop in FCC metals [4]. For BCC metals, prismatic dislocation loops and twinning were observed by Rudd [5].…”

Section: Introductionmentioning

confidence: 60%

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Growth and collapse of nanovoids in tantalum monocrystals loaded at high strain rate

Tang¹,

Bringa²,

Remington³

et al. 2012

AIP Conference Proceedings

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Abstract. Shock-induced spall in ductile metals is known to occur by the sequence of nucleation, growth and coalescence of voids, even in high purity monocrystals. However, the atomistic mechanisms involved are still not completely understood. The growth and collapse of nanoscale voids in tantalum are investigated under different stress states and strain rates by molecular dynamics (MD) simulations. Three principal mechanisms of deformation are identified and quantitatively evaluated: shear loop emission, prismatic loop formation, and twinning. Dislocation shear loops expand as expected from a crystallographic analysis, and their extremities remain attached to the void surface in tension (if there is no dislocation reaction or cross slip), but can detach in compression and form prismatic loops due to cross slip and reactions. Prismatic loops that detach from the void are also formed by reaction of multiple shear loops sharing the same <111> slip direction during hydrostatic loading. Nanotwins form preferably upon both uniaxial and hydrostatic tensile stress. The void-size effect on plasticity is studied via MD simulations and is modeled based on the shear loop emission mechanism. The stresses required for generation of a free surface step, dislocation and bow are calculated by continuum dislocation theory. The predictions agree well with MD simulation results.

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Section: Introductionmentioning

confidence: 60%

“…For BCC metals, prismatic dislocation loops and twinning were observed by Rudd [5]. The goal of the current investigation is to extend the study by Bringa, et al [4] to a BCC metal and to develop a mechanistic understanding of the deformation mechanisms and void-size effect.…”

Section: Introductionmentioning

confidence: 99%

Growth and collapse of nanovoids in tantalum monocrystals loaded at high strain rate

Tang¹,

Bringa²,

Remington³

et al. 2012

AIP Conference Proceedings

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“…Prior atomistic studies revealed that the nanovoid growth process is affected by many factors, including, but not limited to, strain rate [9], temperature [10], initial porosity [11], initial void shape [12], and crystallographic orientations [13,14,15]. Compared with face-centered cubic (FCC) [1,10,12] and body-centered cubic (BCC) [9,2,11] systems, there exist much fewer studies of nanvoids in metals with a hexagonal close-packed (HCP) lattice, in part due to a lack of reliable interatomic potential and more complicated slip/twinning systems in the latter.…”

Section: Introductionmentioning

confidence: 99%

Deformation of periodic nanovoid structures in Mg single crystals

Chavoshi

2018

Mater. Res. Express

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Abstract. Large scale molecular dynamics (MD) simulations in Mg single crystal containing periodic cylindrical voids subject to uniaxial tension along the z direction are carried out. Models with different initial void sizes and crystallographic orientations are explored using two interatomic potentials. It is found that (i) a larger initial void always leads to a lower yield stress, in agreement with an analytic prediction; (ii) orientations, the two potentials identically predict the nucleation of edge dislocations on the prismatic plane, which then glide away from the void, resulting in extrusions at the void surface; in the case of the smallest initial void, these surface extrusions pinch the void into two voids. Besides bringing new physical understanding of the nanovoid structures, our work highlights the variability and uncertainty in MD simulations arising from the interatomic potential, an issue relatively lightly addressed in the literature to date.

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“…31,37 Moreover, the loading orientation and stress states were found to have strong effects on the sequence in which the loops form and interact. 34 With increasing strengths, void collapse was observed to transit from the "geometrical" mode to "hydrodynamic" mode in Cu nanofoam with high initial porosity of 50%. 27 Interacting of multiple voids was also found to decrease the stress required for the onset of plasticity under adiabatic uniaxial compression, compared to that for isolated void.…”

Section: Introductionmentioning

confidence: 99%

“…[25][26][27][28] Previous MD simulations have been conducted to investigate the collapse of a single nanovoid or a collection of nanovoids in both fcc and bcc metals at high strain rates. 27,[29][30][31][32][33][34][35][36][37][38][39] These studies have focused on dislocation activities and the resulting porosity evolution in nanoporous metals. Under high rate loading, the void surfaces were found to be dislocation sources, and their collective interaction leading to very high dislocation densities.…”

Section: Introductionmentioning

confidence: 99%

Scaling laws and deformation mechanisms of nanoporous copper under adiabatic uniaxial strain compression

Yuan

2014

AIP Advances

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A series of large-scale molecular dynamics simulations were conducted to investigate the scaling laws and the related atomistic deformation mechanisms of Cu monocrystal samples containing randomly placed nanovoids under adiabatic uniaxial strain compression. At onset of yielding, plastic deformation is accommodated by dislocations emitted from void surfaces as shear loops. The collapse of voids are observed by continuous emissions of dislocations from void surfaces and their interactions with further plastic deformation. The simulation results also suggest that the effect modulus, the yield stress and the energy aborption density of samples under uniaxial strain are linearly proportional to the relative density ρ. Moreover, the yield stress, the average flow stress and the energy aborption density of samples with the same relative density show a strong dependence on the void diameter d, expressed by exponential relations with decay coefficients much higher than -1/2. The corresponding atomistic mechanisms for scaling laws of the relative density and the void diameter were also presented. The present results should provide insights for understanding deformation mechanisms of nanoporous metals under extreme conditions.

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Void initiation in fcc metals: Effect of loading orientation and nanocrystalline effects

Cited by 165 publications

References 75 publications

Growth and collapse of nanovoids in tantalum monocrystals loaded at high strain rate

Growth and collapse of nanovoids in tantalum monocrystals loaded at high strain rate

Deformation of periodic nanovoid structures in Mg single crystals

Scaling laws and deformation mechanisms of nanoporous copper under adiabatic uniaxial strain compression

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