Computer Simulation of Plastic Deformation of Small Crystals

1991 ◽  
Vol 239 ◽  
Author(s):  
Masao Doyama
Keyword(s):  
Computer Simulation ◽  
Plastic Deformation ◽  
Yield Stress ◽  
Partial Dislocation ◽  
Iron Whisker ◽  
Small Crystals ◽  
Iron Whiskers

ABSTRACTThe deformation of body centered iron whiskers has been simulated. The iron whisker has a very sharp yield stress. Dislocations are created in a small coppe crystal. A higher stress was needed to create the first partial dislocation but less stress to create the second partial dislocation.

Computer Simulation of Creation of Dislocations in Copper Small Crystals

1993 ◽  
Vol 319 ◽  
Author(s):  
H. Tanaka ◽  
Masao Doyama
Keyword(s):  
Molecular Dynamics ◽  
Computer Simulation ◽  
Partial Dislocation ◽  
Stacking Fault ◽  
Shockley Partial Dislocation ◽  
Shockley Partial ◽  
Small Crystals ◽  
The Creation

AbstractDislocations were created near the center of the surface (101) of copper small crystals whose surfaces are (111), (111), (101), (101), (121), and (121) by use of n-body atom potentials and molecular dynamics. At first, a Heidenreich-Shockley partial dislocation was created., As the partial dislocation proceeds, the partial dislocation and the surface was connected with a stacking fault until the next Heidenreich-Shockley partial dislocation was created at the surface.Just before the creation of a partial dislocation the stress was the highest.

Atomistic investigations of tensile and shear mechanical properties of nanotwinned copper with embedded defects

2014 ◽  
Vol 03 (02) ◽  
pp. 1450012
Author(s):  
Yong-Gang Zheng ◽  
Yi-Fei Fu ◽  
Hong-Wu Zhang ◽  
Hong-Fei Ye
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Yield Stress ◽  
Partial Dislocation ◽  
Dislocation Nucleation ◽  
Boundary Dislocation ◽  
Dislocation Interactions ◽  
Simulation Results ◽  
Dynamics Simulations ◽  
Flow Stage

The tensile and shear mechanical properties of nanotwinned copper with embedded defects have been investigated by using molecular dynamics simulations. Simulation results show that the stress concentration at the tips of crack-like defects dominates the first partial dislocation nucleation at the onset of plastic deformation, the joint action of twin boundaries and dislocations controls the yield stress at the earlier plastic deformation stage and the dislocation/twin boundary–dislocation interactions determine the plastic flow stage. Furthermore, it is found that the yield stress decreases nonlinearly with the increase of the crack length, while it decreases almost linearly with the increase of the temperature.

Computer Simulation of Creation of Dislocations in Copper Small Crystals

1993 ◽  
Vol 319 ◽  
Author(s):  
H. Tanaka ◽  
Masao Doyama
Keyword(s):  
Molecular Dynamics ◽  
Computer Simulation ◽  
Partial Dislocation ◽  
Stacking Fault ◽  
Shockley Partial Dislocation ◽  
Shockley Partial ◽  
Small Crystals ◽  
The Creation

AbstractDislocations were created near the center of the surface (101) of copper small crystals whose surfaces are (111), (111), (101), (101), (121), and (121) by use of n-body atom potentials and molecular dynamics. At first, a Heidenreich-Shockley partial dislocation was created., As the partial dislocation proceeds, the partial dislocation and the surface was connected with a stacking fault until the next Heidenreich-Shockley partial dislocation was created at the surface.Just before the creation of a partial dislocation the stress was the highest.

Mechanichal Properties of DGEBA/TEPA Modified Epoxy Resin

2014 ◽  
Vol 775-776 ◽  
pp. 588-592
Author(s):  
Camila Rodrigues Amaral ◽  
Ruben Jesus Sanchez Rodriguez ◽  
Magno Luiz Tavares Bessa ◽  
Verônica Scarpini Cândido ◽  
Sergio Neves Monteiro
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Epoxy Resin ◽  
Yield Stress ◽  
Diglycidyl Ether ◽  
Notch Toughness ◽  
Epoxy Network ◽  
Structural Network ◽  
Flexural Tests ◽  
Modified Epoxy

The correlation between the structural network of a diglycidyl ether of the bisphenol-A (DGEBA) epoxy resin, modified by two distinct aliphatic amines (tetraethylenepentamine TEPA and jeffamine D230), and its mechanical properties, was investigated as possible matrix for abrasive composites applications. Both flexural tests, to determine the yield stress and the elastic modulus, as well as impact tests to determine the notch toughness, were performed. The DGEBA/D230 presented the highest stiffness and toughness but lowest yield stress. This epoxy network also displayed a greater plastic deformation during fracture.

Computer Simulation of Creation and Motion of Edge Dislocations in Face Centered Crystals

1994 ◽  
Vol 356 ◽  
Author(s):  
N. Tajima ◽  
T. Nozaki ◽  
T. Hirade ◽  
Y. Kogure ◽  
Masao Doyama
Keyword(s):  
Molecular Dynamics ◽  
Computer Simulation ◽  
Edge Dislocation ◽  
Embedded Atom ◽  
Small Crystals ◽  
Face Centered ◽  
Edge Dislocations

AbstractComplete and dissociated edge dislocations were created near the center of the surface (101) of aluminum small crystals whose surfaces are (111), (111), (101), (101). (121) and (121). Molecular dynamics with N-body embedded atom potentials were used. Higher stress is needed to create a complete edge dislocation than to create a dissociated dislocation.

Computer Simulation of Plastic Deformation in Tial Alloys in the Presence of Chromium

2018 ◽  
Vol 386 ◽  
pp. 383-387 ◽  
Author(s):  
Anton Gnidenko
Keyword(s):  
Computer Simulation ◽  
Plastic Deformation ◽  
Shear Modulus ◽  
Titanium Aluminide ◽  
Shear Resistance ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Tial Alloys ◽  
Shear Rupture ◽  
Titanium Vacancy

Quantum-mechanical calculations were used to investigate shear rupture in intermetallic titanium aluminide (TiAl) alloys in the presence of vacancy or chromium dopant. The substitution of both Ti and Al atoms by Cr atoms in the γ-TiAl crystal lattice was considered. The simulation of shear was carried out in the (111) slip plane along two directions, namely the [110] and [11-2]. The decrease in the shear resistance of the defects present in the γ-TiAl lattice was estimated. It was shown that when chromium occupies a titanium vacancy, it can compensate for this defect by increasing the shear modulus for the {111} <110> slip system.

A Model for the Conductivity and Compliance of Unpropped and Natural Fractures

SPE Journal ◽  
2017 ◽  
Vol 22 (06) ◽  
pp. 1893-1914 ◽  
Author(s):  
Weiwei Wu ◽  
Mukul M. Sharma
Keyword(s):  
Plastic Deformation ◽  
Yield Stress ◽  
Young’S Modulus ◽  
Correlation Length ◽  
Young's Modulus ◽  
Heterogeneous Surfaces ◽  
Natural Fractures ◽  
Wide Range ◽  
Fracture Closure ◽  
Deformation Interaction

Summary Fluid flow in unpropped and natural fractures is critical in many geophysical processes and engineering applications. The flow conductivity in these fractures depends on their closure under stress, which is a complicated mechanical process that is challenging to model. The challenges come from the deformation interaction and the close coupling among the fracture geometry, pressure, and deformation, making the closure computationally expensive to describe. Hence, most of the previous models either use a small grid system or disregard deformation interaction or plastic deformation. In this study, a numerical model is developed to simulate the stress-driven closure and the conductivity for fractures with rough surfaces. The model integrates elastoplastic deformation and deformation interaction, and can handle contact between heterogeneous surfaces. Computation is optimized and accelerated by use of an algorithm that combines the conjugate-gradient (CG) method and the fast-Fourier-transform (FFT) technique. Computation time is significantly reduced compared with traditional methods. For example, a speedup of five orders of magnitude is obtained for a grid size of 512 × 512. The model is validated against analytical problems and experiments, for both elastic-only and elastoplastic scenarios. It is shown that interaction between asperities and plastic deformation cannot be ignored when modeling fracture closure. By applying our model, roughness and yield stress are found to have a larger effect on fracture closure and compliance than Young's modulus. Plastic deformation is a dominant contributor to closure and can make up more than 70% of the total closure in some shales. The plastic deformation also significantly alters the relationship between fracture stiffness and conductivity. Surfaces with reduced correlation length produce greater conductivity because of their larger apertures, despite more fracture closure. They have a similar fraction of area in contact as compared with surfaces with longer fracture length, but the pattern of area in contact is more scattered. Contact between heterogeneous surfaces with more soft minerals leads to increased plastic deformation and fracture closure, and results in lower fracture conductivity. Fracture compliance appears not to be as sensitive to the distribution pattern of hard and soft minerals. Our model compares well with experimental data for fracture closure, and can be applied to unpropped or natural fractures. These results are obtained for a wide range of conditions: surface profile following Gaussian distribution with correlation length of 50 µm and roughness of 4 to 50 µm, yield stress of 100 to 1500 MPa, and Young's modulus of 20 to 60 GPa. The results may be different for situations outside this range of parameters.

The Influence of the Bauschinger Effect on the Yield Stress, Young’s Modulus, and Poisson’s Ratio of a Gun Barrel Steel

2005 ◽  
Vol 128 (2) ◽  
pp. 179-184 ◽  
Author(s):  
J. Perry ◽  
M. Perl ◽  
R. Shneck ◽  
S. Haroush
Keyword(s):  
Plastic Deformation ◽  
Yield Stress ◽  
Young’S Modulus ◽  
Poisson’S Ratio ◽  
Bauschinger Effect ◽  
Young's Modulus ◽  
Poisson's Ratio ◽  
Compression Tests ◽  
Residual Stress Field ◽  
Gun Barrel

The Bauschinger effect (BE) was originally defined as the phenomenon whereby plastic deformation causes a loss of yield strength restraining in the opposite direction. The Bauschinger effect factor (BEF), defined as the ratio of the yield stress on reverse loading to the initial yield stress, is a measure of the magnitude of the BE. The aim of the present work is to quantitatively evaluate the influence of plastic deformation on other material properties such as Young’s modulus and Poisson’s ratio for gun barrel steel, thus extending the definition of the Bauschinger effect. In order to investigate the change in this material’s properties resulting from plastic deformation, several uniaxial tension and compression tests were performed. The yield stress and Young’s modulus were found to be strongly affected by plastic strain, while Poisson’s ratio was not affected at all. An additional result of these tests is an exact zero offset yield point definition enabling a simple evaluation of the BEF. A simple, triphase test sufficient to characterize the entire elastoplastic behavior is suggested. The obtained experimental information is readily useful for autofrettage residual stress field calculations.

ATOMISTIC SIMULATION OF TORSIONAL VIBRATION AND PLASTIC DEFORMATION OF FIVE-FOLD TWINNED COPPER NANOWIRES

2014 ◽  
Vol 11 (supp01) ◽  
pp. 1344010 ◽  
Author(s):  
Y. G. ZHENG ◽  
Y. T. ZHAO ◽  
H. F. YE ◽  
H. W. ZHANG ◽  
Y. F. FU
Keyword(s):  
Plastic Deformation ◽  
Torsional Vibration ◽  
Partial Dislocation ◽  
Dislocation Nucleation ◽  
Activation Process ◽  
Torsional Angle ◽  
Wire Radius ◽  
Wire Length ◽  
Deformation Behaviors ◽  
The Wire

In this paper, atomistic simulations have been conducted to investigate the torsional mechanical behaviors of five-fold twinned nanowires (FTNs), including the torsional vibration properties, elasto-plastic deformation behaviors and activation process of the first partial dislocation nucleation. Simulation results show that the fundamental torsional vibration frequency is inversely proportional to the wire length and is independent of the wire radius. Provided that an effective shear modulus of FTNs is used, the classic elastic torsional theory may be applicable to nanoscale. Furthermore, it is found that the plastic deformation of FTNs is dominated by partial dislocation activities. The normalized critical torsional angle corresponding to the onset of plastic deformation increases with the decrease of the wire radius and temperature, while it is almost independent of the wire length and loading rate. In addition, the activation energy of the first partial dislocation nucleation is about several electric voltages and decreases with the increase of the wire radius and applied torsional load.

Computer Simulation of the Deformation of Small Crystals

1991 ◽  
Vol 37 ◽  
pp. 77-86 ◽  
Author(s):  
Masao Doyama ◽  
Ryoichi Yamamoto
Keyword(s):  
Computer Simulation ◽  
Small Crystals
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