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Constitutive modeling for strain rate-dependent behaviors of nanocrystalline materials based on dislocation density evolution and strain gradient

Published online by Cambridge University Press:  26 November 2014

Youyi Wu
Affiliation:
School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing, Jiangsu 210009, China
Jianqiu Zhou*
Affiliation:
School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing, Jiangsu 210009, China; and School of Mechanical & Electrical Engineering, Wuhan Institute of Technology, Wuhan, Hubei 430070, China
Shuhong Dong
Affiliation:
School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing, Jiangsu 210009, China
Aosheng Hu
Affiliation:
School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing, Jiangsu 210009, China
Lu Wang
Affiliation:
School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing, Jiangsu 210009, China
Xuming Pang
Affiliation:
School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing, Jiangsu 210009, China
*
a)Address all correspondence to this author. e-mail: zhouj@njtech.edu.cn
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Abstract

To evaluate the influence of strain rate on mechanical behavior of nanocrystalline (NC) materials, a phase mixture constitutive model composed of ordered grain interior phase and plastically softer grain boundary dislocation pile up zone phase was built. Because of dissimilar properties and mismatch between the two phases, dislocation density evolution controlling mechanism based on statistically stored dislocations and geometrically necessary dislocations was analyzed and extended to NC regime to consider their disparate effects. Based on the composite model, a new stress–strain constitutive relation for strain rate-dependent behaviors was firstly established based on dislocation density evolution and strain gradient theory. The calculated data were then compared with corresponding experimental curves and strong strain rate-dependent behaviors were exhibited, which indicated that the predictions kept in good agreement with experiments. Further discussions were presented for calculations of strain rate sensitivity and activation volume for NC Ni through the proposed model.

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Articles
Copyright
Copyright © Materials Research Society 2014 

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References

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