COMPUTATIONAL SIMULATION |
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Multiscale Simulation of Geometric Effect on Onset Plasticity of Nano-scale Asperities |
Siyuan ZHOU,Jianfeng JIN,Lu WANG,Jingyi CAO,Peijun YANG
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Key Laboratory for Anisotropy and Texture of Materials of Education Department, School of Materials Science and Engineering,Northeastern University, Shenyang 110819 |
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Abstract To understand mechanical behaviors of the asperities on a metal rough surface is helpful for understanding the friction, wear property of materials and designing micro/nano electromechanical devices. In the study, multiscale quasicontinuum (QC) method was used to explore geometric effect on onset plasticity of nano-scale asperities on aluminum and copper thin films during nanoindentation on the (001) surface. The results show that existing asperities significantly reduce the yield stress of thin film, compared with the stress of the flat film. For a rectangular asperity, the aspect ratio (width/height) affects yield stress of both films without much change. For a trapezoidal asperity, the yield stress decreases with the base angle (α), especially when the α is over 54.7°. It is also found that deformation twinning can be formed in the aluminum film under the condition of constraining full dislocation formation at nanoscale.
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Published: 25 January 2018
Online: 2018-01-25
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QC model represents a single asperity on the (001) thin film during nanoindentation with a cross-sectional trapezoid shape,where H,α,D and D' is the height, the base angle, top and bottom length, respectively
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Stress-displacement curves during nanoindentation on a smooth surface and on two asperities (D=20 ?, H=20 ? and α=90°) and (D=20 ?,H=20 ? and α=45°) associated with dislocation morphology of the onset plasticity
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(a)Yield stress and (b)dislocation slip planes with different aspect ratios (AR) of the rectangular patterned lines, and dislocation morphology in the Al film with the asperity of H=40 ?, (c)AR=0.5, (d)AR=1.0, (e)AR=1.8 and (f)dislocation morphology in the Cu film with H=40 ? and AR=1.8
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(a)The yield stress of the Al and Cu films containing the asperity at different base angle with the constant D=40 ? and AR=1 and dislocation morphology in the Al film containing the asperity with (b)α=14°, (c)α=55°,and(d)α=81°
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The energy (ΔESurf) for evaluating the effect of sidewall surface at different base angles of the asperities with D=40 ?, AR=1.0
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(a)Stress-displacement curves of the Al and Cu films with the asperity of AR=1.8 and H=40 ? and (b)dislocation morphology at each force-event event in the curve (a)
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Stress-displacement curve on the Al surface with the asperity of D=80 ?,H=40 ?,α=14°, associated with deformation twinning
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