Contact area and size effects in discrete dislocation modeling of wedge indentation

Widjaja, Andreas; Giessen, E. van der; Deshpande, V.S.; Needleman, A.

doi:10.1557/jmr.2007.0090

Cited by 34 publications

(27 citation statements)

References 18 publications

(27 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…First, due to material sink-in a portion of the deformed material surface outside the contact tends to become almost parallel to the indenter surface so that when indentation continues and the indenter touches the surface of the crystal, the contact length suddenly increases. Secondly the surface roughens and, as discussed in detail by Widjaja et al [13], this also leads to abrupt increases in contact length. The predicted increase in the contact length a for the circular indenters in figure 3(b) exhibits the same general trend, with occasional jumps in contact length occurring with the average da/dh decreasing for increasing indentation depth.…”

Section: Numerical Resultsmentioning

confidence: 85%

See 1 more Smart Citation

The effect of indenter shape on sub-micron indentation according to discrete dislocation plasticity

Widjaja

Needleman

Giessen

2006

Modelling Simul. Mater. Sci. Eng.

View full text Add to dashboard Cite

The effect of indenter shape on sub-micron indentation according to discrete dislocation plasticity Widjaja, A.; Needleman, A.; Van der Giessen, E. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Abstract Two-dimensional discrete dislocation simulations of indentation in the submicron range are presented for wedge indenters with a sharp tip and for indenters with a circular tip. Plane strain calculations are carried out for single crystals that are initially free of mobile dislocations and with all dislocations nucleating from a specified distribution of internal sources. The hardness is expressed in terms of the indentation force divided by the actual contact area accounting for roughness of the surface in contact with the indenter. For wedge indenters the hardness is found to decrease with increasing indentation depth, while for indenters with a circular tip the hardness increases somewhat with increasing indentation depth. However, at a given indentation depth, the indentation hardness of circular indenters increases with decreasing tip radius. The difference in hardness evolution for the two tip shapes is mainly due to the manner in which the evolution of the contact area depends on indenter tip shape. The nominal hardness, i.e. that based on the geometric contact area neglecting material sinkin or pile-up and surface roughness, is found to follow the inverse square root size dependence predicted by Nix and Gao [1] and by Swadener et al [2], even though the plastic zone found in the simulations differs significantly in shape and size from that assumed in deriving the scaling laws.

show abstract

Section: Numerical Resultsmentioning

confidence: 85%

“…• as the contact length is significantly larger [13]. For the larger tip angle, the hardness clearly shows the typical size effect for wedge indentation, levelling off at a constant value of around H = 0.4 GPa at h = 0.4 µm.…”

Section: Hardnessmentioning

confidence: 89%

The effect of indenter shape on sub-micron indentation according to discrete dislocation plasticity

Widjaja

Needleman

Giessen

2006

Modelling Simul. Mater. Sci. Eng.

View full text Add to dashboard Cite

show abstract

“…In general, A differs from the nominal contact length A N 2d= tan o due to sink-in or pile-up as sketched in Fig. 1b, but it does not account for surface roughness which, as shown by Widjaja et al (2006), can lead to a significantly smaller contact area in some circumstances and especially for sharp indenters. Perfect sticking is assumed as soon as the wedge comes in contact with the film so the rate boundary conditions applied are…”

Section: Boundary Conditionsmentioning

confidence: 99%

“…In these simulations, ''low source density'' materials were considered with the plasticity size effect mainly resulting from sourcelimited plasticity. Widjaja et al (2005Widjaja et al ( , 2006 reported on two-dimensional simulations for the cylindrical indentation of materials with a wide range of source densities. Over the range of indentation depths considered in these studies, the increasing hardness with increasing indentation depth associated with sharp indenters was not obtained and the cylinder radius played a dominant role.…”

Section: Introductionmentioning

confidence: 99%

Discrete dislocation plasticity analysis of the wedge indentation of films

Balint¹,

Deshpande²,

Needleman³

et al. 2006

Journal of the Mechanics and Physics of Solids

View full text Add to dashboard Cite

Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. AbstractThe plane strain indentation of single crystal films on a rigid substrate by a rigid wedge indenter is analyzed using discrete dislocation plasticity. The crystals have three slip systems at AE35:3 and 90 with respect to the indentation direction. The analyses are carried out for three values of the film thickness, 2, 10 and 50 mm, and with the dislocations all of edge character modeled as line singularities in a linear elastic material. The lattice resistance to dislocation motion, dislocation nucleation, dislocation interaction with obstacles and dislocation annihilation are incorporated through a set of constitutive rules. Over the range of indentation depths considered, the indentation pressure for the 10 and 50 mm thick films decreases with increasing contact size and attains a contact size-independent value for contact lengths A44 mm. On the other hand, for the 2 mm films, the indentation pressure first decreases with increasing contact size and subsequently increases as the plastic zone reaches the rigid substrate. For the 10 and 50 mm thick films sink-in occurs around the indenter, while pile-up occurs in the 2 mm film when the plastic zone reaches the substrate. Comparisons are made with predictions obtained from other formulations: (i) the contact sizeindependent indentation pressure is compared with that given by continuum crystal plasticity; (ii) the scaling of the indentation pressure with indentation depth is compared with the relation proposed by Nix and Gao [1998

show abstract

“…Besides the experimental observations, computer simulations have greatly contributed to the investigation of the response of materials during nanoindentation. The common modeling methods are finite element [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41], crystal plasticity [42][43][44][45][46][47][48][49][50], discrete dislocation dynamics [51][52][53][54][55][56][57][58][59][60][61][62], the quasicontinuum method [63][64][65][66][67][68][69][70][71][72][73]…”

Section: Introductionmentioning

confidence: 99%

Review of Nanoindentation Size Effect: Experiments and Atomistic Simulation

2017

View full text Add to dashboard Cite

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.

show abstract

Contact area and size effects in discrete dislocation modeling of wedge indentation

Cited by 34 publications

References 18 publications

The effect of indenter shape on sub-micron indentation according to discrete dislocation plasticity

The effect of indenter shape on sub-micron indentation according to discrete dislocation plasticity

Discrete dislocation plasticity analysis of the wedge indentation of films

Review of Nanoindentation Size Effect: Experiments and Atomistic Simulation

Contact Info

Product

Resources

About