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

Abstract

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.

A method of coupling discrete dislocation plasticity to the crystal plasticity finite element method

“…The work was devoted to the investigation of the effect of microstructure, including nucleation source density, and number and orientation of pre-defined slip planes, on the indentation pressure [33][34][35]. Furthermore, the effect of indenter shape on the indentation pressure was studied using numerical simulations [36,37], which have also been successfully corroborated by experimental data [17]. The damage due to dislocation activity in indentation processes was simulated in [38], which aimed to provide the link between the dislocation structure and the macroscopic fatigue phenomenon.…”

Strain hardening in 2D discrete dislocation dynamics simulations: A new ‘2.5D’ algorithm

“…An alternative approach is thus a two-dimensional method (2D DD) that sacrifices some physical fidelity for computational efficiency. Following early work by Amodeo and Ghoniem (1990), the most commonly used 2D DD model by Van der Giessen and Needleman (1995) considers parallel straight edge dislocations in plane strain, which permits the study of problems involving complex inhomogeneous loading such as the growth of cracks (Deshpande et al, 2001;Chakravarthy and Curtin, 2010b), bi-material fracture (O'Day and Curtin, 2005), micro-void evolution (Segurado and Llorca, 2009), indentation (Widjaja et al, 2007), thin films (Nicola et al, 2006;Chng et al, 2006) and sliding/friction (Deshpande et al, 2004). The 2D DD method captures the long range interactions between dislocations, which enables size and gradient effects to emerge naturally, but truly 3D phenomena like junction formation and forest hardening are missing, so that standard 2D DD models predict elastic/perfectly-plastic response under nominally homogeneous loading conditions.…”

Plane-strain discrete dislocation plasticity incorporating anisotropic elasticity

“…Cleveringa et al, 2000;O'Day and Curtin, 2004;Deshpande et al, 2002) or indenter tips (e.g. Widjaja et al, 2005Widjaja et al, , 2007 and investigations of microstructural size effects in bulk (Cleveringa et al, 1997;Balint et al, 2008;Guruprasad et al, 2008) and thin film materials (Nicola et al, 2003(Nicola et al, , 2005b.…”