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Journal of Nanomaterials
Volume 2008, Article ID 380961, 5 pages
Research Article

Dislocation Nucleation and Pileup under a Wedge Contact at Nanoscale

1Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, USA
2Department of Mechanical Engineering and Materials Science, Rice University, Houston, TX 77251, USA

Received 5 November 2007; Accepted 18 January 2008

Academic Editor: Junlan Wang

Copyright © 2008 Y. F. Gao and J. Lou. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Indentation responses of crystalline materials have been found to be radically different at micrometer and nanometer scales. The latter is usually thought to be controlled by the nucleation of dislocations. To explore this physical process, a dislocation mechanics study is performed to determine the conditions for the nucleation of a finite number of dislocations under a two-dimensional wedge indenter, using the Rice-Thomson nucleation criterion. The configurational force on the dislocation consists of the applied force, the image force, and the interaction force between dislocations. Dislocations reach equilibrium positions when the total driving force equals the effective Peierls stress, giving a set of nonlinear equations that can be solved using the Newton-Raphson method. When the apex angle of the wedge indenter increases, the critical contact size for dislocation nucleation increases rapidly, indicating that dislocation multiplication near a blunt wedge tip is extremely difficult. This geometric dependence agrees well with experimental findings.