Nanomechanics of Crack Front Mobility

[+] Author and Article Information
Ting Zhu

Department of Mechanical Engineering,  Massachusetts Institute of Technology, Cambridge, MA 02139

Ju Li

Department of Materials Science and Engineering,  Ohio State University, Columbus, OH 43210

Sidney Yip

Departments of Nuclear Engineering and Materials Science and Engineering,  Massachusetts Institute of Technology, Cambridge, MA 02139syip@mit.edu

J. Appl. Mech 72(6), 932-935 (Oct 05, 2005) (4 pages) doi:10.1115/1.2047607 History: Received October 05, 2004; Revised October 05, 2005

Minimum energy paths for unit advancement of a crack front are determined by reaction pathway sampling, thus providing the reaction coordinates for the analysis of crack tip mechanics in ductile and brittle materials. We compare results on activation energy barrier and atomic displacement distributions for an atomically sharp crack in Cu, where one observes the emission of a partial dislocation loop, and in Si, where crack front extension evolves in a kink-like fashion.

Copyright © 2005 by American Society of Mechanical Engineers
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Figure 5

Contour of opening displacement (normalized by interplanar spacing h=2.35Å) at the Griffith load KIG(4)

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Figure 4

MEP of crack extension in Si at the Griffith load KIG(4)

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Figure 3

Contour of (a) shear displacement (normalized by the Burgers vector of a partial dislocation b=1.476Å) and (b) opening displacement (normalized by the interplanar spacing h=2.087Å) across the slip plane at the saddle-point state (3)

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Figure 2

MEP of dislocation loop emission in Cu at a load of G=0.75Gemit(3)

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Figure 1

(a) Schematics of a 3D atomically sharp crack front under a mode-I load KI; (b) energy landscape of the crack system at different loads (KI′<KIG<KI″<KIath). Open circle represents the initial state of a straight crack front under an applied load KI, closed circle is the final state after the crack front uniformly advances by one atomic spacing (under the same load KI as the initial state), and shaded circle corresponds to the saddle-point state in between.



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