Indentation across size scales and disciplines: Recent developments in experimentation and modeling

Gouldstone, Andrew; Chollacoop, Nuwong; Dao, Ming; Li, Ju; Minor, Andrew M.; Shen, Yu‐Lin

doi:10.1016/j.actamat.2006.08.044

Cited by 431 publications

(223 citation statements)

References 225 publications

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“…Plastic deformation in nanoscale volumes of materials often exhibits a stochastic, discontinuous character, in contrast to the typical smooth yield behavior in their bulk counterparts [1][2][3][4][5][6][7]. Such jerky behavior has been attributed to the instability of microscopic defect processes, such as dislocation nucleation or depinning in crystalline metals [8,9], phase transformation in semiconductors [10] and localized shear transformation in amorphous metals [11].…”

Section: Introductionmentioning

confidence: 99%

Size effects and strength fluctuation in nanoscale plasticity

Wang¹,

Zhong²,

Lu³

et al. 2012

Acta Materialia

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Section: Introductionmentioning

confidence: 99%

Size effects and strength fluctuation in nanoscale plasticity

Wang¹,

Zhong²,

Lu³

et al. 2012

Acta Materialia

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“…Similar intermittent plastic flow in the form of load fluctuations or displacement jumps is reported when the indentation depth is less than 100 nm both in thin and bulk samples [7][8][9][10][11][12]. Thus, nanoindentation experiments fall into the class of experiments where plastic instability manifests due to small deformed volume [7][8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 85%

“…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%

“…This means that we use Equation (13) for V m (σ) and express σ = F/A H in Equations (15) and (16) using Equations (5) and (7). A few comments are in order at this point.…”

Section: A Dislocation Dynamical Model For Load Fluctuations Using a mentioning

confidence: 99%

“…Traditionally, two modes of nanoindentation experiments are employed, namely, load/force controlled (LC) mode or displacement controlled (DC) mode [7,9,11,[13][14][15]. In both modes, experiments measure the force response of the sample (to the applied force) as a function of indentation depth.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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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