Mechanical property evaluation on the bending and compressing behaviour of nano-beam

Abstract

Based on quasicontinuum (QC) multiscale simulation method, a series of simulation models were set up for bending and compressing rod-shaped microstructure of single crystal Cu. The effects of structural parameters on typical mechanical properties were analyzed, such as elastic modulus, elastic limit, yield strength, and Poisson’s ratio. According to the analysis of displacement, inner stress and strain energy, the mechanisms of deformation and failure were also revealed. The experimental result shows that the mechanical properties exhibit obvious size effect during the bending and compression process. In the bending simulation, when the span-thickness ratio is more than 10, the elastic modulus rises slightly with the increase of strain. And the smaller the beam is, the faster the elastic modulus grows. Meanwhile, when the span-thickness ratio keeps constant the elastic modulus will decrease with the growth of the beam sizes. However, in the compression model, the size effect on Poisson’s ratio is not remarkable. The dimensional change in one direction cannot influence the mechanical parameters greatly. Mechanical twins and dislocation contribute to the compression behaviour greatly. Meanwhile, the stress concentration can also be found in the inner partial area and the strain energy decreases abruptly after the crush of beam microstructure.

Keywords

nano-beam / multiscale simulation / bending / compressing / mechanical property

References

[1] Cagin T, Dereli G, Uludogan M, et al. Thermal and Mechanical Properties of Some fcc Transition Metals[J]. Physical Review B, 1999, 59(5): 3468-3473.

[2] Paulo SB, Jose-Pedro R. Large Deformation and Amorphization of Ni Nanowires under Uniaxial Strain: A Molecular Dynamics Study[J]. Physical Review B, 2000, 62(24): 16950-16955.

[3] Komanduri R, Chandrasekaran N, Raff LM. Molecular Dynamic Simulations of Uniaxial Tension at Nanoscale of Semiconductor Materials for Micro-electro-mechanical Systems[J]. Materials Science and Engineering A, 2003, 340: 58-67.

[4] Tschopp MA, McDowell DL. Influence of Single Crystal Orientation on Homogeneous Dislocation Nucleation under Uniaxial Loading[J]. Journal of the Mechanics and Physics of Solids, 2008, 56: 1806-1830.

[5] Li M, Chu WY, Gao KW, et al. Molecular Dynamics Simulation of Healing of an Ellipsoid Crack in Copper under Compressive Stress[J]. Materials Letters, 2004, 58: 543-546.

[6] Nozaki T, Doyama M, Kogure Y. Simulation of High Speed Deformation of Copper Single Crystals[J]. Materials Science and Engineering: A, 2003, 350(1-2): 233-237.

[7] Yang ZY, Lu ZX, Zhao Y. Atomistic Simulation on Size-dependent Yield Strength and Defects Evolution of Metal Nanowires[J]. Computational Materials Science, 2009, 46: 142-150.

[8] Yang ZY, Lu ZX, Zhao YP. Shape Effects on the Yield Stress and Deformation of Silicon Nanowires: A Molecular Dynamics Simulation[J]. Journal of Applied Physics, 2009, 106: 023537-1.

[9] Tadmor EB, Ortez M, Phillips R. Quasicontinuum Analysis of Defects in Solids[J]. Philosophical Magazine A, 1996, 73(6): 1529-1563.

[10] Mei JF, Ni YS, Li JW. The Effect of Crack Orientation on Fracture Behavior of Tantalum by Multiscale Simulation[J]. International Journal of Solids and Structures, 2011, 48: 3054-3062.

[11] Yu WS, Shen SP. Multiscale Analysis of the Effects of Nanocavity on Nanoindentation[J]. Computational Materials Science, 2009, 46: 425-430.

[12] Li JW, Lu HB, Ni YS, et al. Quasicontinuum Study the Influence of Misfit Dislocation Interactions on Nanoindentation[J]. Computational Materials Science, 2011, 50: 3162-3170.

[13] Hakobyan Y, Tadmor EB, James RD. Objective Quasicontinuum Approach for Rod Problems[J]. Physical Review B, 2012, 86: 1-16.

[14] Li CX, Tang XS, Xiang GB. Fatigue Crack Growth of Cable Steel Wires in a Suspension Bridge: Multiscaling and Mesoscopic Fracture Mechanics[J]. Theoretical and Applied Fracture Mechanics, 2010, 53: 113-126.

[15] Kiener D, Motz C, Dehm G. Dislocation-induced Crystal Rotations in Micro-compressed Single Crystal Copper Columns[J]. J. Mater. Sci., 43(7): 2503–2506

[16] Bai QS, Tong Z, Liang YC, et al. Simulation of scale dependency on tensile mechanical Properties of Single Crystal Copper Nano-rod[J]. Acta Metallurgica Sinica, 2010, 46(10): 1173-1180.

[17] Greer JR, Oliver WC, Nix WD. Size Dependence of Mechanical Properties of Gold at The Micron Scale in the Absence of Strain Gradients[J]. Acta Materialia, 2005, 53: 1821-1830.

[18] Park HS, Gall K, Zimmerman JA. Deformation of FCC Nanowires by Twinning and Slip [J]. J. Mech. Phys. Solids, 2006, 54(9): 1862-1881.

[19] Tang QH. Effect of Size on Mechanical Behavior of Au Pillars by Molecular Dynamics Study[J]. Science China-Physics, Mechanics and Astronomy, 2012, 55(6): 1111-1117.

[20] Stölken JS, Evans AG. A Micro-bend Test Method for Measuring the Plasticity Length Scale[J]. Acta Materialia, 1998, 46: 5109-5115.