Atomistic mechanisms governing elastic limit and incipient plasticity in crystals

Li, Ju; Vliet, Krystyn J. Van; Zhu, Ting; Yip, Sidney; Suresh, S.

doi:10.1038/nature00865

Cited by 639 publications

(452 citation statements)

References 20 publications

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“…MD simulation of spherical indentation normal to the 111 surface of Al shows the atomic-level details of dislocation nucleation and subsequent incipient plasticity [50]. With the atoms colored by CN, the nucleation and propagation of dislocations can be clearly captured.…”

Section: Coordination Number (Cn)mentioning

confidence: 99%

How to identify dislocations in molecular dynamics simulations?

Wang

Yang

et al. 2014

Sci. China Phys. Mech. Astron.

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Dislocations are of great importance in revealing the underlying mechanisms of deformed solid crystals. With the development of computational facilities and technologies, the observations of dislocations at atomic level through numerical simulations are permitted. Molecular dynamics (MD) simulation suggests itself as a powerful tool for understanding and visualizing the creation of dislocations as well as the evolution of crystal defects. However, the numerical results from the large-scale MD simulations are not very illuminating by themselves and there exist various techniques for analyzing dislocations and the deformed crystal structures. Thus, it is a big challenge for the beginners in this community to choose a proper method to start their investigations. In this review, we summarized and discussed up to twelve existing structure characterization methods in MD simulations of deformed crystal solids. A comprehensive comparison was made between the advantages and disadvantages of these typical techniques. We also examined some of the recent advances in the dynamics of dislocations related to the hydraulic fracturing. It was found that the dislocation emission has a significant effect on the propagation and bifurcation of the crack tip in the hydraulic fracturing.

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Section: Coordination Number (Cn)mentioning

confidence: 99%

How to identify dislocations in molecular dynamics simulations?

Wang

Yang

et al. 2014

Sci. China Phys. Mech. Astron.

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“…The apparent decrease of the contact pressure under the maintained constant rate of displacement increase is tantamount to the pop-in observed during nanoindentation experiments [17][18][19]. Pop-in, alternatively referred to as the yield point, marks the onset of plasticity in defectfree crystals [17][18][19]. For load controlled experiments, pop-in appears as rapid displacement increase whereas its incidence under displacement control is evident as a load drop [20].…”

Section: Resultsmentioning

confidence: 99%

“…Then the contact pressure continues to gradually decrease approaching hardness (H) of bulk Si at ≈ 12 GPa [9]. The apparent decrease of the contact pressure under the maintained constant rate of displacement increase is tantamount to the pop-in observed during nanoindentation experiments [17][18][19]. Pop-in, alternatively referred to as the yield point, marks the onset of plasticity in defectfree crystals [17][18][19].…”

Section: Resultsmentioning

confidence: 99%

Influence of Phase Transformations on Incipient Plasticity of Si-Nanospheres

Chrobak

Nowak

2017

Acta Phys. Pol. A

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Our finding of the current spike effect highlighted for the first time in 2009 offers an enhanced understanding of the link between nanoscale mechanical deformation and electrical behavior, and ultimately suggests key advances in unique phase-change applications in future electronics. Certainly, crystal imperfections affect the properties of the nanoparticles themselves, e.g., their biocompatibility and biodegradability. The potential role of dislocations having a profound impact on the use of Si nanoparticles was largely overlooked, since plastic deformation of bulk Si is dominated by amorphization and phase transformations. Here we show an effect of bulk → nanoparticle transition (deconfinement) on incipient plasticity of Si-nanovolume. Our results provide a fresh insight into the dilemma concerning dislocation or phase transformation origin of nanoscale plastic deformation of semiconductor nanoobjects.

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“…In both modes, experiments measure the force response of the sample (to the applied force) as a function of indentation depth. While several load drops of decreasing magnitudes are seen in the DC mode experiments [7,9,11,[13][14][15], several displacement jumps of decreasing magnitudes are seen beyond the elastic limit in the LC mode experiments [10,12,14,16,17]. The maximum load on the elastic branch is close to the theoretical yield stress.…”

Section: Introductionmentioning

confidence: 90%

“…Furthermore, since the sample is expected to be dislocation free within the initial indented nanometer volume, nucleation of dislocation loops has to occur before their multiplication. A few simulations [16,21,23,26] also show detachment of the loops from the source followed by their propagation to the boundary (see Figure 9 of Ref. [23] and Figure 5 of Ref.…”

Section: General Form Of Time Evolution Equations For Dislocation Denmentioning

confidence: 99%

A Novel Approach to Modelling Nanoindentation Instabilities

Ananthakrishna

Krishnamoorthy

2018

Crystals

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Abstract:We review the recently developed models for load fluctuations in the displacement controlled mode and displacement jumps in the load controlled mode of indentation. To do this, we devise a method for calculating plastic contribution to load drops and displacement jumps by setting-up a system of coupled nonlinear time evolution equations for the mobile and forest dislocation densities by including relevant dislocation mechanisms. These equations are then coupled to the equation defining constant displacement rate or load rate. The model for the displacement controlled mode using a spherical indenter predicts all the generic features of nanoindentation such as the elastic branch followed by several force drops of decreasing magnitudes and residual indentation depth after unloading. The stress corresponding to the elastic force maximum is close to the yield stress of an ideal solid. The predicted numbers for all the quantities match experiments on single crystals of Au using a spherical indenter. We extend the approach to model the load controlled nanoindentation experiments that employ a Berkovich indenter. We first identify the dislocation mechanisms contributing to different regions of the F − z curve as a first step for obtaining a good fit to a given experimental F − z curve. This is done by studying the influence of the parameters associated with various dislocation mechanisms on the model F − z curves. The study also demonstrates that the model predicts all the generic features of nanoindentation such as the existence of an initial elastic branch followed by several displacement jumps of decreasing magnitudes and residual plasticity after unloading for a range of model parameter values. Furthermore, an optimized set of parameter values can be easily determined that give a good fit to the experimental load-displacement curves for Al single crystals of (110) and (133) orientations. Our model also predicts the indentation size effect in a region where the displacement jumps disappear. The good agreement of the results of the models with experiments supports our view that the present approach can be used as an alternate method to simulations. The approach also provides insights into several open questions.

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Atomistic mechanisms governing elastic limit and incipient plasticity in crystals

Cited by 639 publications

References 20 publications

How to identify dislocations in molecular dynamics simulations?

How to identify dislocations in molecular dynamics simulations?

Influence of Phase Transformations on Incipient Plasticity of Si-Nanospheres

A Novel Approach to Modelling Nanoindentation Instabilities

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