Surface constrained plasticity: Oxide rupture and the yield point process

Kramer, Donald E.; Yoder, Karl; Gerberich, William W

doi:10.1080/01418610108216651

Cited by 99 publications

(49 citation statements)

References 37 publications

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“…Specifically, for indenters in the size range actually used in experiment, dislocation activity takes place well in advance of the first force drop, in line with the findings of Kramer et al [9]. Conversely, the first force drop probably occurs as a result of a dislocation avalanche involving large numbers of previously nucleated dislocations.…”

Section: P H Y S I C a L R E V I E W L E T T E R Ssupporting

confidence: 74%

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Effect of Indenter-Radius Size on Au(001) Nanoindentation

2003

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We address the question of whether results obtained for small indenters scale to indenter sizes in the experimental range. The quasicontinuum method is used in order to extend the computational cell size to 2 2 1 m 3 , nominally containing of order 2:5 10 11 atoms, and in order to permit consideration of indenter radii in the range 70 ÿ 700 A. The dislocation structures for the large indenter are found to be less sharp and to extend over a larger region than for the small indenter. In addition, the large-indenter force-displacement curve differs from that corresponding to the small indenter in one important respect, namely, the absence of force drops during indentation, despite profuse dislocation activity. Based on these observations, we conclude that the indenter force is not a reliable indicator of the onset of dislocation activity and plastic deformation for indenter sizes in the experimental range. DOI: 10.1103/PhysRevLett.90.226102 PACS numbers: 02.70.-c, 31.15.-p, 46.15.-x The objective of this work is to ascertain the effect of indenter radius on the mechanics of nanoindentation of ductile fcc crystals at zero temperature (see, e.g., [1][2][3][4][5][6][7][8][9] for experimental background). For definiteness, we specifically focus on the indentation of Au (001) by spherical indenters of tip radii 70 and 700 A. One reason why the tip radius size is of concern is that straight molecular dynamics calculations have often relied on artificially small indenters in order to reduce the size of the computational cell [10 -20], and the scaling of the results to larger indenters is not straightforward. In particular, it is not immediately clear how dislocation activity depends onand how effective properties such as the force vs depthof-indentation relation scales with -indenter size.The technique we use in order to sidestep the size restrictions of straight molecular dynamics is the quasicontinuum method of Tadmor and co-workers [21][22][23]. Thus, by coarsening the level of spatial resolution of the computational mesh away from the indenter we are able to span realistic material samples of the order of 2 2 1 m 3 , which nominally contain 2:5 10 11 atoms. This helps to capture the elastic field of the indenter without introducing spurious or parasitic effects associated with periodicity or small sample sizes. By adapting the mesh size to the deformation field, the calculations provide full atomistic resolution over an appropriate region under the indenter. In this manner, the calculation is reduced to a coarse-grained system of size several orders of magnitude smaller than the original one, without appreciable loss of accuracy. In addition, this model reduction enables us to consider a wide range of indenters (70 to 700 A in the work presented here).The particular implementation of the quasicontinuum method used in the calculations has been described in [23]. In particular, following [21-23] we adopt as adaption indicatorwhere K denotes a simplex in the triangulation, II E K denotes the second invariant of the L...

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Section: P H Y S I C a L R E V I E W L E T T E R Ssupporting

confidence: 74%

“…The objective of this work is to ascertain the effect of indenter radius on the mechanics of nanoindentation of ductile fcc crystals at zero temperature (see, e.g., [1][2][3][4][5][6][7][8][9] for experimental background). For definiteness, we specifically focus on the indentation of Au(001) by spherical indenters of tip radii 70 and 700 A.…”

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confidence: 99%

Effect of Indenter-Radius Size on Au(001) Nanoindentation

2003

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“…Compared to face centered cubic (fcc) systems, the plastic behavior of bcc metals is very complex and is still relatively poorly understood [10][11][12][13][14]. As a consequence, only a few nanoindentation studies have addressed dislocation nucleation in pure bcc single crystals [15][16][17][18][19][20][21]. Most of these studies have been performed on Fe-3 wt%…”

Section: Introductionmentioning

confidence: 99%

Dislocation nucleation in bcc Ta single crystals studied by nanoindentation

et al. 2007

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“…However, if this envelope is further segmented according to the materials tested, we can identify a much smaller region that is accessible to oxidizing materials such as metals. In the existing experimental literature, studies on these materials either require a sufficiently low test temperature to retard oxide growth 3,18,22 , or involve flowing inert gas to dilute oxygen content in the atmosphere around the sample [48][49] . Avoiding oxidation is clearly a critical point for the smallest nanoindentation experiments, lest the measured properties become convoluted with those of the oxide.…”

Section: Introductionmentioning

confidence: 99%

Hot nanoindentation in inert environments

Trenkle

Packard

Schuh

2010

Review of Scientific Instruments

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An instrument capable of performing nanoindentation at temperatures up to 500 o C in inert atmospheres, including partial vacuum and gas near atmospheric pressures, is described.Technical issues associated with the technique (such as drift and noise) and the instrument (such as tip erosion and radiative heating of the transducer) are identified and addressed. Based on these considerations, preferred operation conditions are identified for testing on various materials. As a proof-of-concept demonstration, the hardness and elastic modulus of three materials are measured: fused silica (non-oxidizing), aluminum and copper (both oxidizing). In all cases, the properties match reasonably well with published data acquired by more conventional test methods.2

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Surface constrained plasticity: Oxide rupture and the yield point process

Cited by 99 publications

References 37 publications

Effect of Indenter-Radius Size on Au(001) Nanoindentation

Effect of Indenter-Radius Size on Au(001) Nanoindentation

Dislocation nucleation in bcc Ta single crystals studied by nanoindentation

Hot nanoindentation in inert environments

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