Large scale atomistic simulation of size effects during nanoindentation: Dislocation length and hardness

Voyiadjis, George Z.; Yaghoobi, Mohammadreza

doi:10.1016/j.msea.2015.03.024

Cited by 87 publications

(29 citation statements)

References 31 publications

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“…Molecular dynamics (MD) is a powerful tool that can be incorporated as a pseudo-experimental tool to address the size effect during the nanoindentation. In the case of crystalline metals, many different aspects of nanoindentation experiment, such as initial dislocation nucleation and evolution pattern [79,81,83], the effect of surface step [80], effects of GB [84,88,126,127], the effect of film thickness [128], the effect of substrate [129], the effect of residual stress [130], the effect of boundary conditions [85] and size effects during nanoindentation [86,87] have been investigated using MD. Szlufarska [131] summarized the advances in atomistic modelling of the nanoindentation experiment.…”

Section: Atomistic Simulation Of Nanoindentationmentioning

confidence: 99%

“…The indenter force can be derived from the repulsive potential used to model the indenter. Voyiadjis and his co-workers [85][86][87] showed that the true indentation depth h is different from the tip displacement d during nanoindentation. They developed the required geometrical equations to obtain the precise indentation depth.…”

Section: Atomistic Simulation Of Nanoindentationmentioning

confidence: 99%

“…First, Voyiadjis and Yaghoobi [86] investigated the dislocation nucleation and evolution pattern during nanoindentation. As an example, Figure 16 shows the dislocation nucleation and evolution for Ni thin film indented by a cylindrical indenter during nanoindentation.…”

Section: Atomistic Simulation Of Nanoindentationmentioning

confidence: 99%

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Review of Nanoindentation Size Effect: Experiments and Atomistic Simulation

2017

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Nanoindentation is a well-stablished experiment to study the mechanical properties of materials at the small length scales of micro and nano. Unlike the conventional indentation experiments, the nanoindentation response of the material depends on the corresponding length scales, such as indentation depth, which is commonly termed the size effect. In the current work, first, the conventional experimental observations and theoretical models of the size effect during nanoindentation are reviewed in the case of crystalline metals, which are the focus of the current work. Next, the recent advancements in the visualization of the dislocation structure during the nanoindentation experiment is discussed, and the observed underlying mechanisms of the size effect are addressed. Finally, the recent computer simulations using molecular dynamics are reviewed as a powerful tool to investigate the nanoindentation experiment and its governing mechanisms of the size effect.

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Section: Atomistic Simulation Of Nanoindentationmentioning

confidence: 99%

Section: Atomistic Simulation Of Nanoindentationmentioning

confidence: 99%

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Review of Nanoindentation Size Effect: Experiments and Atomistic Simulation

2017

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“…A vast number of numerical studies on the evolution of dislocation structure exist in the literature, some concerned with discrete dislocations and molecular dynamics (Deshpande et al, 2003(Deshpande et al, , 2005Yaghoobi and Voyiadjis, 2014;Tarleton et al, 2015;Voyiadjis and Yaghoobi, 2015), while others take a continuum approach (Yefimov et al, 2004;Klusemann and Yalçinkaya, 2013;van Beers et al, 2013). GNDs accommodate the plastic strain gradients and thus, walls of GNDs are associated with high slip gradients occurring in a small region, and therefore also high second gradients of slip.…”

Section: Introductionmentioning

confidence: 99%

On modeling micro-structural evolution using a higher order strain gradient continuum theory

El-Naaman

Nielsen

Niordson

2016

International Journal of Plasticity

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Published experimental measurements on deformed metal crystals show distinct pattern formation, in which dislocations are arranged in wall and cell structures. The distribution of dislocations is highly non-uniform, which produces discontinuities in the lattice rotations. Modeling the experimentally observed micro-structural behavior, within a framework based on continuous field quantities, poses obvious challenges, since the evolution of dislocation structures is inherently a discrete and discontinuous process. This challenge, in particular, motivates the present study, and the aim is to improve the micro-structural response predicted using strain gradient crystal plasticity within a continuum mechanics framework. One approach to modeling the dislocation structures observed is through a back stress formulation, which can be related directly to the strain gradient energy. The present work offers an investigation of constitutive equations for the back stress based on both considerations of the gradient energy, but also includes results obtained from a purely phenomenological starting point. The influence of model parameters is brought out in a parametric study, and it is demonstrated how a proper treatment of the back stress enables dislocation wall and cell structure * Tel: +45 4525-4020, Fax: +45 4593-1475 URL: saeln@mek.dtu.dk (S.A. El-Naaman)

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“…Nowadays, thin film materials at micro-and nano-scale play a significant role in a wide range of engineering applications, such as medical instruments, micro-/nano-electromechanical systems (MEMS/NEMS), and optical devices [1][2][3][4]. The mechanical properties of thin film materials, which strongly influence the reliability and service life of a nano-device, have been attracting both industrial and scientific interest [4].…”

Section: Introductionmentioning

confidence: 99%

Atomistic Insights into the Effects of Residual Stress during Nanoindentation

Sun

Shi

2017

Crystals

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Abstract:The influence of in-plane residual stress on Hertzian nanoindentation for single-crystal copper thin film is investigated using molecular dynamics simulations (MD). It is found that: (i) the yield strength of incipient plasticity increases with compressive residual stress, but decreases with tensile residual stress; (ii) the hardness decreases with tensile residual stress, and increases with compressive residual stress, but abruptly drops down at a higher compressive residual stress level, because of the deterioration of the surface; (iii) the indentation modulus reduces linearly with decreasing compressive residual stress (and with increasing tensile residual stress). It can be concluded from the MD simulations that the residual stress not only strongly influences the dislocation evolution of the plastic deformation process, but also significantly affects the size of the plastic zone.

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Large scale atomistic simulation of size effects during nanoindentation: Dislocation length and hardness

Cited by 87 publications

References 31 publications

Review of Nanoindentation Size Effect: Experiments and Atomistic Simulation

Review of Nanoindentation Size Effect: Experiments and Atomistic Simulation

On modeling micro-structural evolution using a higher order strain gradient continuum theory

Atomistic Insights into the Effects of Residual Stress during Nanoindentation

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