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Abstract
A numerical study is performed to investigate the effect of loading history on the size-dependent material properties of pure and nitrogen-doped ultrananocrystalline diamond (UNCD) specimens under different shear loading paths. A simple procedure with combined kinetic Monte Carlo and molecular dynamics methods is adopted to form a polycrystalline UNCD with an artificial grain boundary (GB). By randomly adding different numbers of nitrogen atoms into the GBs, the effects of nitrogen doping and GB width on the UNCD responses under pre-compressioned/tensioned shear loading conditions are studied. It appears that the loading history has certain influence on the size-dependent material properties of UNCD, which provides useful information for formulating a multiscale constitutive model with applications to general cases.
ACKNOWLEDGEMENTS
L.S. wishes to thank the partial support from the Australian Research Council under Grant No. DP0772478 and Monash University under the Faculty of Engineering Small Grant scheme. Z.C. would like to acknowledge the support from the US/NSF-NIRT program under Grant No. 0304472, and the support from the National Natural Science Foundation of China under Project Nos. 10421202, 10640420176 and 50679013, the Program for Changjiang Scholars and Innovative Research Teams in Universities of China, and the National Key Basic Research Special Foundation of China (2005CB321704). The authors are grateful to the NIRT members: Professors Espinosa, Hersam, Belytschko and Schatz at Northwestern University, and Professor Auciello at the University of Illinois at Chicago, as well as the collaborators at Argonne National Laboratory: Drs. Carlisle and Zapol, for joint discussions. , and were produced by utilizing software VMD developed by Humphrey et al. [Citation35].