Discrete Dislocation Dynamics Simulations of Irradiation Hardening in Nuclear Materials

2020 ◽  
pp. 2243-2271
Author(s):  
Jaime Marian ◽  
Steve Fitzgerald ◽  
Giacomo Po
Keyword(s):  
Dislocation Dynamics ◽  
Nuclear Materials ◽  
Irradiation Hardening ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Dynamics Simulations

scholarly journals Multiscale Modelling of Nanoindentation

2007 ◽  
Vol 345-346 ◽  
pp. 925-930 ◽  
Author(s):  
Hyung Jun Chang ◽  
Heung Nam Han ◽  
Marc Fivel
Keyword(s):  
Finite Element Modelling ◽  
Numerical Models ◽  
Dislocation Dynamics ◽  
Nanoindentation Test ◽  
Discrete Dislocation Dynamics ◽  
The Past ◽  
Discrete Dislocation ◽  
The World ◽  
Continuum Description ◽  
Dynamics Simulations

Nanoindentation is an interesting technique used to probe the local mechanical properties of a material. Although this test has been widely used and developed over the world during the past few years, it remains a lot of uncertainties regarding the interpretation of nanoindentation data. In this study, we propose to simulate the nanoindentation test of FCC single crystals like Cu or Ni using three numerical models. At the lowest scale, molecular dynamics simulations give details of the nucleation of the first dislocations induced by the indentation. At an intermediate scale, discrete dislocation dynamics simulations are performed to study the evolution of the dislocation microstructure during the loading. Finally, at the upper scale, 3D finite element modelling using crystal plasticity constitutive equations give a continuum description of the indentation induced plasticity. It is shown how the different models are interconnected together.

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.

Mechanics and Dislocation Structures at the Micro-Scale: Insights on Dislocation Multiplication Mechanisms from Discrete Dislocation Dynamics Simulations

2014 ◽  
Vol 1651 ◽  
Author(s):  
D. Weygand
Keyword(s):  
Dislocation Dynamics ◽  
Discrete Dislocation Dynamics ◽  
Relative Contribution ◽  
Discrete Dislocation ◽  
Dynamics Simulations ◽  
Stress Drops ◽  
Dislocation Sources ◽  
Continuum Theories ◽  
Dislocation Multiplication

ABSTRACTThe plasticity of micro-pillar deformation has widely been studied by discrete dislocation dynamics simulations to explain the so-called size effect. In this study the role of glissile junctions forming during plastic deformation under various loading scenarios is in the center of interest. The activity of these naturally forming dislocation sources is followed in detail. Surprisingly these junctions are rather active sources and not just another obstacle as often assumed. Their relative contribution to the overall dislocation density for the simulated specimens reaches often values of 20% or even more. The formation of such a glissile junction is often correlated to stress drops or the end of a stress drop. It is therefore suggested – at least for the sample sizes considered – that this dislocation multiplication mechanism should be take into account in continuum models such as crystal plasticity of higher order dislocation continuum theories.

Determination of Dislocation Interaction Strengths Using Discrete Dislocation Dynamics of Curved Dislocations

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Alankar Alankar ◽  
Ioannis N. Mastorakos ◽  
David P. Field ◽  
Hussein M. Zbib
Keyword(s):  
Shear Stress ◽  
Pure Aluminum ◽  
Dislocation Dynamics ◽  
Dislocation Interaction ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Junction Formation ◽  
Latent Hardening ◽  
Dynamics Simulations

In latent interactions of dislocations, junction formation is one of the most important phenomena that contribute to the evolution of strength. In this work, the latent hardening coefficients for pure aluminum are estimated using 3D multiscale dislocation dynamics program (MDDP). Three well-known junction configurations, namely, the Hirth lock, the glissile junction, and the Lomer lock, are studied using 3D discrete dislocation dynamics simulations. The evolution of strength is discussed as a function of the resolved shear stress (RSS) and the number of junctions for the three junctions investigated. Hirth lock and Lomer lock are found to be the weakest and strongest junctions, respectively. Collinear reaction of dislocations does not form a junction but causes a higher strength than a Lomer lock. Quantitative and qualitative results are compared with those found in the literature.

scholarly journals A Novel Mechanical Method to Measure Shear Strength in Specimens Under Pressure

2006 ◽  
Vol 929 ◽  
Author(s):  
Juan Pablo Escobedo ◽  
David Field ◽  
David Lassila ◽  
Mary Leblanc
Keyword(s):  
Shear Strength ◽  
Thin Foil ◽  
Testing Procedure ◽  
Dislocation Dynamics ◽  
Calibration Data ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Thin Foils ◽  
Experimental Apparatus ◽  
Dynamics Simulations

ABSTRACTA new experimental apparatus has been developed for performing shear tests on specimens held under moderately high hydrostatic pressures (on the order of 4 GPa). This testing procedure experimentally determines the pressure-dependent shear strength of thin foil specimens. The experiments provide calibration data for models of materials subjected to extreme pressures such as the Steinberg-Guinan hardening model and can assist in model validation for discrete dislocation dynamics simulations, among others. This paper reports the development of the experimental procedures and the results of initial experiments on thin foils of polycrystalline Ta performed under hydrostatic pressures ranging from 1 to 4 GPa. Both yielding and hardening behavior of Ta are observed to be sensitive to the imposed pressure.

Sign in / Sign up

Export Citation Format

Share Document