PSI - Issue 23

Solveig Melin et al. / Procedia Structural Integrity 23 (2019) 137–142 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 5. Snapshots of dislocation structure at different axial strains. Green color corresponds to Shockley, purple to Stair-rod, turquoise to Frank, blue to Perfect and red to Oher types of dislocation. In Fig. 4f a snapshot perpendicular to the loading direction is inserted.

4. Conclusions

The mechanical behavior of nanosized Cu beams has been investigated under tensile loading. The beams consists either of one single grain or holds a centrally placed grain boundary, thus forming two grains. The different crystallographic orientations of the grains were [100], [110] and [111]. The grain boundary had a large impact on the strains at plastic initiation and rupture, which were significantly reduced, as compared to single crystal beams. The first dislocations were formed close to, or at the grain boundary, for all cases. For higher loads one of the grains were found more favorable for further dislocation formation and slip, and almost all plastic deformation occurred in one grain only. Also large differences in dislocation structures, portions of mobile and immobile dislocations and rupture strains were found between the different grain orientations, whereas the strain at plastic initiation remained similar for all cases. Further, the variation in dislocation density was found to closely correlate to axial stress variations during loading. A general observation was that, as the dislocation density increases, the axial stress decreases and vice versa. Ahadi, A., Hansson, P. and Melin, S. (2017). Tensile behaviour of single-crystal nano-sized Cu beams – Geometric scaling effects. Computational Material Sciene 135 (2017) 127-133. Ellard, B. T. and Miller, R.E. 2011. Modelling Materials Continuum, Atomistic and Multiscale Techniques, Cam.bridge University Press Foiles, S. M.,Baskes, M. I. and Daw, M. S. (1986). Embedded-atom-method functions for the fcc metals Cu, Ag, Au, Ni, Pd, Pt, and their alloys. Physical review B, Vol. 33, No. 12. LAMMPS; http://lammps.sandia.gov Stukowski, A. (2010). Visualization and analysis of atomistic simulation data with OVITO – the Open Visualization Tool. Modelling Simul. Mater. Sci. Eng. 18. Stukowski, A., Bulatov V.V. and Arsenlis, A. (2012). Automated identification and indexing of dislocations in crystal interfaces. August 8, 2012 Modelling and Simulations in Materials Science and Engineering Zhan, H.F., Gu, Y.T., Yan, C., Feng, X.Q. and Yarlagadda P. K. D. V. (2011). Numerical exporation of plastic deformation mechanisms of copper nanowires with surface defects. Computational Materials Science 50 (2011) 3425-3430. Yaghoobi, M. and Voyiadjis, G. Z. (2016). Size effects in fcc crystals during the high rate compression test. Acta Materialia 120(2016)190-201. References