Discrete dislocation sim ulation of thin film plasticit y

2001 ◽  
Vol 673 ◽  
Author(s):  
B. von Blanckenhagen ◽  
P. Gumbsch ◽  
E. Arzt
Keyword(s):  
Thin Film ◽  
Dislocation Motion ◽  
Source Size ◽  
Dislocation Dynamics ◽  
Polycrystalline Thin Film ◽  
Confined Geometry ◽  
Free Standing ◽  
Capping Layer ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation

ABSTRACTA discrete dislocation dynamics sim ulation is used to investigate dislocation motion in the confined geometry of a polycrystalline thin film. The repeated activ ation of a Frank-Read source is sim ulated. The stress to activate the sources and to initiate plastic fiow is significantly higher than predicted by models where the dislocations extend o ver the entire film thic kness. An efiective source size, which scales with the grain dimensions, yields fiow stresses in reasonable agreemen t with experimen ts. The infiuence of dislocations deposited at interfaces is investigated by comparing calculations for a film sandwic hed between a substrate and a capping layer with those for a free standing film.

3D Discrete Dislocation Models Of Thin-Film Plasticity

1997 ◽  
Vol 505 ◽  
Author(s):  
A. Hartmaier ◽  
M. C. Fivel ◽  
G. R. Canova ◽  
P. Gumbsch
Keyword(s):  
Thin Film ◽  
Three Dimensional ◽  
Dislocation Dynamics ◽  
Normal Stresses ◽  
Bulk Materials ◽  
Free Standing ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Dislocation Models ◽  
Dimensional Simulation

ABSTRACTThree-dimensional simulation schemes for discrete dislocation dynamics (DDD) have been used successfully to investigate plasticity of bulk materials. The adaptation of these DDD schemes to a description of thin-film plasticity requires detailed modeling of the interfaces and surfaces of the film. One possible method is to compensate for the normal stresses that a dislocation distribution exerts on a surface by appropriate point loads. This traction-compensation method is extended to a free standing film (two opposing surfaces). The extension to a thin film on a substrate is possible.

scholarly journals Influence of Excess Volumes Induced by Re and W on Dislocation Motion and Creep in Ni-Base Single Crystal Superalloys: A 3D Discrete Dislocation Dynamics Study

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 637 ◽  
Author(s):  
Siwen Gao ◽  
Zerong Yang ◽  
Maximilian Grabowski ◽  
Jutta Rogal ◽  
Ralf Drautz ◽  
...  
Keyword(s):  
Single Crystal ◽  
Excess Volume ◽  
Dislocation Motion ◽  
Excess Volumes ◽  
Dislocation Dynamics ◽  
Size Difference ◽  
Strengthening Effect ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Solute Atoms

A comprehensive 3D discrete dislocation dynamics model for Ni-base single crystal superalloys was used to investigate the influence of excess volumes induced by solute atoms Re and W on dislocation motion and creep under different tensile loads at 850 ° C. The solute atoms were distributed homogeneously only in γ matrix channels. Their excess volumes due to the size difference from the host Ni were calculated by density functional theory. The excess volume affected dislocation glide more strongly than dislocation climb. The relative positions of dislocations and solute atoms determined the magnitude of back stresses on the dislocation motion. Without diffusion of solute atoms, it was found that W with a larger excess volume had a stronger strengthening effect than Re. With increasing concentration of solute atoms, the creep resistance increased. However, a low external stress reduced the influence of different excess volumes and different concentrations on creep.

Situating the Vector Density Approach Among Contemporary Continuum Theories of Dislocation Dynamics

2021 ◽  
pp. 1-32
Author(s):  
Joseph Anderson ◽  
Vignesh Vivekanandan ◽  
Peng Lin ◽  
Kyle Starkey ◽  
Yash Pachaury ◽  
...  
Keyword(s):  
Collective Behavior ◽  
Dislocation Motion ◽  
Dislocation Dynamics ◽  
Past Century ◽  
Vector Density ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Dislocation Mechanics ◽  
Field Dislocation ◽  
Continuum Theories

Abstract For the past century, dislocations have been understood to be the carriers of plastic deformation in crystalline solids. However, their collective behavior is still poorly understood. Progress in understanding the collective behavior of dislocations has primarily come in one of two modes: the simulation of systems of interacting discrete dislocations and the treatment of density measures of varying complexity which are considered as continuum fields. A summary of contemporary models of continuum dislocation dynamics is presented. This includes, in order of complexity, the two-dimensional statistical theory of dislocations, the field dislocation mechanics treating the total Kroner-Nye tensor, vector density approaches which treat geometrically necessary dislocations on each slip system of a crystal, and high-order theories which examine the effect of dislocation curvature and distribution over orientation. Each of theories contain common themes, including statistical closure of the kinetic dislocation transport equations and treatment of dislocation reactions such as junction formation. An emphasis is placed on how these common themes rely on closure relations obtained by analysis of discrete dislocation dynamics experiments. The outlook of these various continuum theories of dislocation motion is then discussed.

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