A study of the submicron indent-induced plastic deformation

1999 ◽  
Vol 14 (6) ◽  
pp. 2251-2258 ◽  
Author(s):  
C. F. Robertson ◽  
M. C. Fivel
Keyword(s):  
Plastic Deformation ◽  
Three Dimensional ◽  
Dislocation Nucleation ◽  
Dislocation Dynamics ◽  
Dynamics Simulation ◽  
Nanoindentation Test ◽  
Experimental Conditions ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Transmission Electron

A new method has been developed to achieve a better understanding of submicron indent-induced plastic deformation. This method combines numerical modeling and various experimental data and techniques. Three-dimensional discrete dislocation dynamics simulation and the finite element method (FEM) were used to model the experimental conditions associated with nanoindentation testing in fcc crystals. Transmission electron microscopy (TEM) observations of the indent-induced plastic volume and analysis of the experimental loading curve help in defining a complete set of dislocation nucleation rules, including the shape of the nucleated loops and the corresponding macroscopic loading. A validation of the model is performed through direct comparisons between a simulation and experiments for a nanoindentation test on a [001] copper single crystal up to 50 nm deep.

scholarly journals Influence of Size on the Fractal Dimension of Dislocation Microstructure

Metals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 478
Author(s):  
Yinan Cui ◽  
Nasr Ghoniem
Keyword(s):  
Fractal Dimension ◽  
Three Dimensional ◽  
Dislocation Dynamics ◽  
Two Dimensional ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Transmission Electron ◽  
Dynamics Simulations ◽  
2D And 3D ◽  
Microscopy Images

Three-dimensional (3D) discrete dislocation dynamics simulations are used to analyze the size effect on the fractal dimension of two-dimensional (2D) and 3D dislocation microstructure. 2D dislocation structures are analyzed first, and the calculated fractal dimension ( n 2 ) is found to be consistent with experimental results gleaned from transmission electron microscopy images. The value of n 2 is found to be close to unity for sizes smaller than 300 nm, and increases to a saturation value of ≈1.8 for sizes above approximately 10 microns. It is discovered that reducing the sample size leads to a decrease in the fractal dimension because of the decrease in the likelihood of forming strong tangles at small scales. Dislocation ensembles are found to exist in a more isolated way at the nano- and micro-scales. Fractal analysis is carried out on 3D dislocation structures and the 3D fractal dimension ( n 3 ) is determined. The analysis here shows that ( n 3 ) is significantly smaller than ( n 2 + 1 ) of 2D projected dislocations in all considered sizes.

Discrete Dislocation Dynamics Simulation on Strengths of Dislocation Network Stacks in Multilayered Structures

2007 ◽  
Vol 353-358 ◽  
pp. 1086-1089 ◽  
Author(s):  
Yoshihisa Kaneko ◽  
S. Hirota ◽  
Satoshi Hashimoto
Keyword(s):  
Three Dimensional ◽  
Multilayered Structure ◽  
Mobile Dislocation ◽  
Dislocation Dynamics ◽  
Dynamics Simulation ◽  
Dislocation Network ◽  
Multilayered Structures ◽  
Lattice Constants ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation

Strengths of multilayered structures have been investigated using three-dimensional discrete dislocation dynamics (DDD) simulation. The multilayered structure was modeled as a stack of misfit dislocation networks which must exist at an interface between adjoining crystals having different lattice constants. Passages of a single mobile dislocation through several kinds of network stacks were simulated. The critical stress required for the dislocation passage depended on the dislocation spacing of the network, the number of network sheet and the spacing between network sheets.

Influence of Initial Defects on the Mechanical Properties of Single Crystal Copper: Discrete Dislocation Dynamics Study

2018 ◽  
Vol 913 ◽  
pp. 627-635
Author(s):  
Ming Yi Zhang ◽  
Min Zhong ◽  
Shuai Yuan ◽  
Jing Song Bai ◽  
Ping Li
Keyword(s):  
Dislocation Density ◽  
Single Crystal ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Dislocation Dynamics ◽  
Single Crystal Copper ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Stress Curve ◽  
Initial Dislocation Density

In this paper, three dimensional discrete dislocation dynamics method was used to quantitatively investigate the influence of initial defects on mechanical response of single crystal copper. Both the irradiation defects (interstitial loops) and random dislocation lines with different densities are considered. The simulation results demonstrate that the yield strength of single crystal copper is higher with higher initial dislocation density and higher interstitial loop density. Dislocation density increases quickly by nucleation and multiplication and microbands are formed during plastic deformation when only the random dislocation lines are initially considered. Characteristics of microbands show excellent agreement with experiment results. Dislocation multiplication is suppressed in the presence of interstitial loops, and junctions and locks between dislocations and interstitial loops are formed. Dislocation density evolution shows fluctuation accompanied with strain-stress curve fluctuation.

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