scholarly journals The Size Effects of Point Defect on the Mechanical Properties of Monocrystalline Silicon: A Molecular Dynamics Study

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3011
Author(s):  
Wei Wan ◽  
Changxin Tang ◽  
An Qiu ◽  
Yongkang Xiang
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Yield Strength ◽  
Point Defect ◽  
Size Effects ◽  
Constant Strain Rate ◽  
Monocrystalline Silicon ◽  
Dislocation Slip ◽  
Actual Strength ◽  
Yield Strength Variation

The molecular dynamics method was used to simulate the fracture process of monocrystalline silicon with different sizes of point defect under a constant strain rate. The mechanism of the defect size on the mechanical properties of monocrystalline silicon was also investigated. The results suggested that the point defect significantly reduces the yield strength of monocrystalline silicon. The relationships between the yield strength variation and the size of point defect fitted an exponential function. By statistically analyzing the internal stress in monocrystalline silicon, it was found that the stress concentration induced by the point defect led to the decrease in the yield strength. A comparison between the theoretical strength given by the four theories of strength and actual strength proved that the Mises theory was the best theory of strength to describe the yield strength of monocrystalline silicon. The dynamic evolution process of Mises stress and dislocation showed that the fracture was caused by the concentration effect of Mises stress and dislocation slip. Finally, the fractured microstructures were similar to a kind of two-dimensional grid which distributed along the cleavage planes while visualizing the specimens. The results of this article provide a reference for evaluating the size effects of point defects on the mechanical properties of monocrystalline silicon.

scholarly journals Enhanced electrical conductivity and mechanical properties in thermally stable fine-grained copper wire

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Qingzhong Mao ◽  
Yusheng Zhang ◽  
Yazhou Guo ◽  
Yonghao Zhao
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Electrical Conductivity ◽  
Yield Strength ◽  
High Speed ◽  
Copper Wire ◽  
Rapid Development ◽  
Dislocation Slip ◽  
Ultrafine Grains ◽  
The Wire

AbstractThe rapid development of high-speed rail requires copper contact wire that simultaneously possesses excellent electrical conductivity, thermal stability and mechanical properties. Unfortunately, these are generally mutually exclusive properties. Here, we demonstrate directional optimization of microstructure and overcome the strength-conductivity tradeoff in copper wire. We use rotary swaging to prepare copper wire with a fiber texture and long ultrafine grains aligned along the wire axis. The wire exhibits a high electrical conductivity of 97% of the international annealed copper standard (IACS), a yield strength of over 450 MPa, high impact and wear resistances, and thermal stability of up to 573 K for 1 h. Subsequent annealing enhances the conductivity to 103 % of IACS while maintaining a yield strength above 380 MPa. The long grains provide a channel for free electrons, while the low-angle grain boundaries between ultrafine grains block dislocation slip and crack propagation, and lower the ability for boundary migration.

scholarly journals MD INVESTIGATIONS FOR MECHANICAL PROPERTIES OF COPPER NANOWIRES WITH AND WITHOUT SURFACE DEFECTS

2012 ◽  
Vol 09 (01) ◽  
pp. 1240003 ◽  
Author(s):  
Y. T. GU ◽  
H. F. ZHAN
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Yield Strength ◽  
Yield Point ◽  
Surface Defects ◽  
Volume Ratio ◽  
Strain Rates ◽  
Copper Nanowires ◽  
Dislocation Source ◽  
Different Temperatures

Based on the molecular dynamics (MD) method, the single-crystalline copper nanowire with different surface defects is investigated through tension simulation. For comparison, the MD tension simulations of perfect nanowire are first carried out under different temperatures, strain rates, and sizes. It has concluded that the surface–volume ratio significantly affects the mechanical properties of nanowire. The surface defects on nanowires are then systematically studied in considering different defect orientation and distribution. It is found that the Young's modulus is the insensitive of surface defects. However, the yield strength and yield point show a significant decrease due to the different defects. Different defects are observed to serve as a dislocation source.

Quasicontinuum Simulation of Uniaxial Tension of Single Crystal Copper Nanowire

2011 ◽  
Vol 694 ◽  
pp. 200-204
Author(s):  
Xing Lei Hu ◽  
Ying Chun Liang ◽  
Jia Xuan Chen ◽  
Hong Min Pen
Keyword(s):  
Mechanical Properties ◽  
Finite Element Method ◽  
Molecular Dynamics ◽  
Finite Element ◽  
Single Crystal ◽  
Size Effects ◽  
Tension Test ◽  
Quasicontinuum Method ◽  
Single Crystal Copper ◽  
Copper Nanowire

Quasicontinuum simulations of tension test of single crystal copper nanowire are performed to analyze deformation mechanism of tension process and size effects of mechanical properties. New tension models of nanowire are constructed by using quasicontinuum method, which has combined molecular dynamics and finite element method. Tension processes of three different length nanowires without notches and those with notches are simulated. Yield strength and elastic modulus are calculated according to the obtained load-displacement curves. Finally, the results show that the mechanical properties of copper nanowire have obvious size effect and the notches have obvious influence on the mechanical properties.

Temperature Effect on Tensile Behavior of Helical Multi-Shell Gold Nanowires

2006 ◽  
Vol 505-507 ◽  
pp. 385-390 ◽  
Author(s):  
Jenn Sen Lin ◽  
Shin Pon Ju ◽  
Yu-Lin Peng ◽  
Wen Jay Lee
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Tensile Testing ◽  
Constant Strain Rate ◽  
Helical Structure ◽  
Md Simulations ◽  
Tensile Behavior ◽  
Gold Nanowires ◽  
Deformation Behaviors ◽  
Fcc Structure

This study performs molecular dynamics (MD) simulations to investigate the tensile behavior of Helical Multi-Shell (HMS) gold nanowires. As their name suggests, these nanowires have a multi-shell helical structure rather than a conventional bulk FCC structure. The mechanical properties and deformation behaviors of the 7-1, 11-4 and 14-7-1 HMS structures are examined under tensile testing at temperatures between 4K and 300 K and a constant strain rate of 0.003% −1 ps . The results reveal that temperature influences the yielding stress, the Young’s modulus, and the deformation behaviors of HMS nanowires. The yielding stress of the 7-1 structure is found to be higher than that of the 11-4 or 14-7-1 structures. Finally, under different temperature conditions, many different close-packed structures are identified in the nanowires before they fracture.

scholarly journals Investigating size effects in graphene–BN hybrid monolayers: a combined density functional theory-molecular dynamics study

RSC Advances ◽  
2021 ◽  
Vol 11 (21) ◽  
pp. 12595-12606
Author(s):  
I. S. Oliveira ◽  
J. S. Lima ◽  
A. Freitas ◽  
C. G. Bezerra ◽  
S. Azevedo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Density Functional Theory ◽  
Size Effects ◽  
Density Functional ◽  
Functional Theory

We combine Density Functional Theory and Molecular Dynamics to study graphene–BN monolayers ranging from 2 nm to 100 nm. We find that the mechanical properties are independent of scale when we increase graphene and the BN domain proportionately.

Point Defect Effects on Tensile Strength of BCC-Fe Studied by Molecular Dynamics

2020 ◽  
Author(s):  
Pandong Lin ◽  
Junfeng Nie ◽  
Meidan Liu
Keyword(s):  
Molecular Dynamics ◽  
Tensile Strength ◽  
Point Defect ◽  
Yield Stress ◽  
Point Defects ◽  
Constant Strain Rate ◽  
Tensile Load ◽  
Perfect Crystal ◽  
Defect Concentration ◽  
Rpv Steel

Abstract BCC-Fe is the critical and major component of the reactor pressure vessel (RPV) steel. With long-tern neutron irradiation, many point defects can be obtained in RPV steel. In this paper, the points defects (interstitial, vacancy and Frenkel pair) effects on the tensile strength of Fe are studied by molecular dynamics simulations at 300K. The uni-axial tensile load is along [001] direction of the Fe samples loading in constant strain rate. The Fe atoms are added or removed randomly to generate point defects. For point defects, three types of point defects can decrease the tensile strength containing yield stress and strain of Fe samples. In addition, the tensile strength decreases with the increase of point defect concentration. With the same defect concentration, interstitials decrease the yield stress the most seriously compared with the vacancies and Frenkel pairs. Apart from that, the morphology and evolution of the microstructure of Fe with point defects are also investigated under tension. Compared with the perfect crystal, the generation of dislocation decreases the tensile strength dramatically. For sample with interstitials, interstitial clusters form and evolve in dislocations loops finally. For sample with vacancis, vacancy may aggregate together and vacancy clusters form as a result, which is seen as precursors of dislocation loop. Notably, the results are meaningful to understand the effects of point defects on tensile strength of BCC-Fe.

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