Vol. 4, No. 9, 2009

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Modeling dislocation sources and size effects at initial yield in continuum plasticity

Saurabh Puri, Anish Roy, Amit Acharya and Dennis Dimiduk

Vol. 4 (2009), No. 9, 1603–1618

Size effects at initial yield (prior to stage II) of idealized micron-sized specimens are modeled within a continuum model of plasticity. Two different aspects are considered: specification of a density of dislocation sources that represent the emission of dislocation dipoles, and the presence of an initial, spatially inhomogeneous excess dislocation content. Discreteness of the source distribution appears to lead to a stochastic response in stress-strain curves, with the stochasticity diminishing as the number of sources increases. Variability in stress-strain response due to variations of source distribution is also shown. These size effects at initial yield are inferred to be due to physical length scales in dislocation mobility and the discrete description of sources that induce internal-stress-related effects, and not due to length-scale effects in the mean-field strain-hardening response (as represented through a constitutive equation).

continuum plasticity, dislocations, finite elements
Received: 16 July 2008
Revised: 14 March 2009
Accepted: 4 June 2009
Published: 17 January 2010
Saurabh Puri
Department of Mechanical Engineering
California Institute of Technology
Pasadena, CA 91125
United States
Anish Roy
Wolfson School of Mechanical and Manufacturing Engineering
Loughborough University
Leicestershire, LE11 3TU
United Kingdom
Amit Acharya
Department of Civil and Environmental Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
United States
Dennis Dimiduk
Air Force Research Laboratory
Materials and Manufacturing Directorate
AFRL/MLLM Bldg. 655
2230 Tenth Street
Wright-Patterson AFB, OH 45433-7817
United States