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A combined dislocation–cohesive zone model for fracture in nanocrystalline materials

Published online by Cambridge University Press:  25 January 2012

Yingguang Liu
Affiliation:
Department of Mechanical Engineering, Nanjing University of Technology, Nanjing 210009, Jiangsu, People’s Republic of China
Jianqiu Zhou*
Affiliation:
Department of Mechanical Engineering, Nanjing University of Technology, Nanjing 210009, Jiangsu, People’s Republic of China; and Department of Mechanical Engineering, Wuhan Institute of Technology, Wuhan 430070, Hubei, People’s Republic of China
Tongde Shen
Affiliation:
High-Tech Research Institute & State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology, Nanjing 210009, Jiangsu, People’s Republic of China
*
a)Address all correspondence to this author. e-mail: zhouj@njut.edu.cn
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Abstract

A combined dislocation–cohesive zone model was proposed to describe the fracture toughness of nanocrystalline (nc) materials. In the framework of the model, cohesive stress near crack tip initiates edge dislocations, which move to the opposite grain boundaries. The emitted dislocations provide a shielding effect of the crack. The dependence of both the maximum number of dislocations, emitted by a crack, and the critical stress intensity factor on grain size d (ranging from 20 to100 nm) for Cu was calculated. The calculated results show that (i) nc materials have low fracture toughness, (ii) the critical stress intensity factor decreases with decreased grain size, and (iii) the grain size effect is not high; for instance, increasing the grain size from 20 to 100 nm increases the value of critical stress intensity factor only by 0.035 MPa/m1/2.

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Articles
Copyright
Copyright © Materials Research Society 2012

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