List of Journal Publications
2009
2.
Kumar, R., Nicola, L., der Giessen, E. Van
Density of grain boundaries and plasticity size effects: A discrete dislocation dynamics study Journal Article
In: MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, vol. 527, no. 1-2, pp. 7–15, 2009.
Abstract | BibTeX | Tags: Discrete dislocations, Grain boundary, size effects, Thin films | Links:
@article{Kumar2009,
title = {Density of grain boundaries and plasticity size effects: A discrete dislocation dynamics study},
author = {R. Kumar and L. Nicola and E. Van der Giessen},
doi = {10.1016/j.msea.2009.08.072},
year = {2009},
date = {2009-01-01},
journal = {MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING},
volume = {527},
number = {1-2},
pages = {7–15},
abstract = {Discrete dislocation dynamics simulations are carried out to systematically investigate the microstructural and geometrical size dependence of films under tension that have a varying number of grains through their thickness. By varying film thickness, grain size and aspect ratio, more insight is gained into the competition between grain boundary hardening and film thickness effects. This provides a seamless link between previous dislocation plasticity studies and qualitative agreement with experimental data. In the simulations, plasticity arises from the collective motion of discrete dislocations of edge character. Their dynamics is incorporated through constitutive rules for nucleation, glide, pinning and annihilation. Grain boundaries are treated as impenetrable to dislocation motion. The numerical results show that the grain size dependence of yield in thin films as well as in bulk polycrystals is controlled by the density of grain boundaries.},
keywords = {Discrete dislocations, Grain boundary, size effects, Thin films},
pubstate = {published},
tppubtype = {article}
}
Discrete dislocation dynamics simulations are carried out to systematically investigate the microstructural and geometrical size dependence of films under tension that have a varying number of grains through their thickness. By varying film thickness, grain size and aspect ratio, more insight is gained into the competition between grain boundary hardening and film thickness effects. This provides a seamless link between previous dislocation plasticity studies and qualitative agreement with experimental data. In the simulations, plasticity arises from the collective motion of discrete dislocations of edge character. Their dynamics is incorporated through constitutive rules for nucleation, glide, pinning and annihilation. Grain boundaries are treated as impenetrable to dislocation motion. The numerical results show that the grain size dependence of yield in thin films as well as in bulk polycrystals is controlled by the density of grain boundaries.
2005
1.
Nicola, L., der Giessen, Erik Van, Needleman, Alan
Size effects in polycrystalline thin films analyzed by discrete dislocation plasticity Journal Article
In: THIN SOLID FILMS, vol. 479, no. 1-2, pp. 329–338, 2005.
Abstract | BibTeX | Tags: dislocation dynamics, Grain boundary, Interface, Stress | Links:
@article{Nicola2005a,
title = {Size effects in polycrystalline thin films analyzed by discrete dislocation plasticity},
author = {L. Nicola and Erik Van der Giessen and Alan Needleman},
doi = {10.1016/j.tsf.2004.12.012},
year = {2005},
date = {2005-01-01},
journal = {THIN SOLID FILMS},
volume = {479},
number = {1-2},
pages = {329–338},
abstract = {Stress development and relaxation in polycrystalline thin films perfectly bonded to a stiff substrate is analyzed numerically. The calculations are carried out within a two-dimensional plane strain framework. The film-substrate system is subject to a prescribed temperature decrease, with the coefficient of thermal expansion of the metal film larger than that of the substrate. Plastic deformation arises solely from the glide of edge dislocations. The dislocations nucleate from pre-existing Frank-Read sources, with the grain boundaries and film-substrate interface acting solely as impenetrable barriers to dislocation glide. At each stage of loading, a boundary value problem is solved to enforce the boundary conditions and the stress field and the dislocation Structure are obtained. The results of the simulations show both film-thickness and a am size dependent strengthening of polycrystalline films. Limited plasticity occurs in films with a sufficiently small grain-size, mainly due to a reduced nucleation rate in the constrained grain geometry.},
keywords = {dislocation dynamics, Grain boundary, Interface, Stress},
pubstate = {published},
tppubtype = {article}
}
Stress development and relaxation in polycrystalline thin films perfectly bonded to a stiff substrate is analyzed numerically. The calculations are carried out within a two-dimensional plane strain framework. The film-substrate system is subject to a prescribed temperature decrease, with the coefficient of thermal expansion of the metal film larger than that of the substrate. Plastic deformation arises solely from the glide of edge dislocations. The dislocations nucleate from pre-existing Frank-Read sources, with the grain boundaries and film-substrate interface acting solely as impenetrable barriers to dislocation glide. At each stage of loading, a boundary value problem is solved to enforce the boundary conditions and the stress field and the dislocation Structure are obtained. The results of the simulations show both film-thickness and a am size dependent strengthening of polycrystalline films. Limited plasticity occurs in films with a sufficiently small grain-size, mainly due to a reduced nucleation rate in the constrained grain geometry.
