Acta Metall Sin  2019, Vol. 55 Issue (11): 1477-1486    DOI: 10.11900/0412.1961.2019.00025
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A Three-Dimensional Discrete Dislocation Dynamics Simulation on Micropillar Compression of Single Crystal Copper with Dislocation Density Gradient
XIONG Jian1,WEI Dean1,LU Songjiang1,KAN Qianhua1,KANG Guozheng1,ZHANG Xu1,2()
1. Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province, School of Mechanics and Engineering, Southwest Jiaotong University, Chengdu 610031, China
2. State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi'an Jiaotong University, Xi'an 710049, China
Abstract

 ZTFLH: TG146.1
Fund: National Natural Science Foundation of China Nos(11672251);National Natural Science Foundation of China Nos(11872321);and Opening Fund of State Key Laboratory for Strength and Vibration of Mechanical Structures(SV2018-KF-10)
Corresponding Authors:  Xu ZHANG     E-mail:  xzhang@swjtu.edu.cn
 Fig.1  Dislocation discretization in the discrete dislocation dynamics simulation (The red node is the physical node, representing the real dislocation node; the blue nodes are the discretization nodes, which are generated according to certain rules; the green point is the surface node, which connects a dislocation segment; the black line is the dislocation segment)Color online Table 1  Number of sources, dislocation density and dislocation spacing in different layers for the model configurations Table 2  Material parameters used in the discrete dislocation dynamics simulation Fig.2  Initial dislocation configurations of dislocation density gradient structure model under different loading directions (The colors of dislocation lines in the graph represents different types of Burgers vectors of dislocations)Color online(a) the loading direction is perpendicular to the direction of dislocation density gradient, the arrows indicate loading direction(b) the loading direction is parallel with the direction of dislocation density gradient, the arrows indicate loading direction Fig.3  Equivalent stress-strain curves and dislocation density evolution curves of single crystal copper micropillar with dislocation density gradient structure under different loading directions Table 3  Schmid factors of 12 slip systems in single crystalline copper under different loading directions Fig.4  Primary slip systems under two different loading directions (The planes ACD (normal vector is ($1ˉ$11)) and BCD (normal vector is (1$1ˉ$1)) are the primary slip planes, and the red edges of the Thompson tetrahedron are the primary slip directions, AC and AD represent the slip directions of [0$1ˉ$1] and [101] in the slip plane ACD, respectively; BC and BD represent the slip directions of [$1ˉ$01] and [011] in the slip plane BCD, respectively)Color online(a) along X axis (b) along Z axis Fig.5  The snapshots of evolved dislocation structures corresponding to strains of 0.05% (a), 0.10% (b), 0.15% (c), 0.20% (d) and 0.25% (e) in the compression process along the X-axis direction which is perpendicular to the dislocation density gradient directionColor online Fig.6  Distributions of plastic strain on the surface corresponding to strains of 0.05% (a), 0.10% (b), 0.15% (c), 0.20% (d) and 0.25% (e) in the compression process along the X-axis direction which is perpendicular to the dislocation density gradient directionColor online Fig.7  The evolutions of plastic strain (a) and the dislocation density (b) in bottom, middle and top layer, which have different dislocation densities, when loading direction is along X-axis which is perpendicular to the dislocation density gradient direction Fig.8  The snapshots of evolved dislocation structure corresponding to strains of 0.05% (a), 0.10% (b), 0.15% (c), 0.20% (d) and 0.25% (e) in the compression process along the Z-axis direction which is parallel with the dislocation density gradient directionColor online Fig.9  Distributions of plastic strain on the surface corresponding to strains of 0.05% (a), 0.10% (b), 0.15% (c), 0.20% (d) and 0.25% (e) in the compression process along the Z-axis direction which is parallel with the dislocation density gradient directionColor online Fig.10  The evolutions of plastic strain (a) and the dislocation density (b) in bottom, middle and top layer, which have different dislocation densities, when loading direction is along Z-axis which is parallel with the dislocation density gradient direction