Stochastic Dislocation Dynamics under Creep Conditions in Metals

2002 ◽  
Vol 731 ◽  
Author(s):  
Masato Hiratani ◽  
Hussein M. Zbib
Keyword(s):  
Thermal Fluctuation ◽  
Dislocation Motion ◽  
Cross Slip ◽  
Dislocation Dynamics ◽  
Atomistic Simulations ◽  
Thermal Processes ◽  
New Model ◽  
Slip Mechanism ◽  
Fcc Metals ◽  
Thermally Activated

AbstractA stochastic model is proposed to study dislocation dynamics in metallic single crystals. A Langevin type thermal fluctuation is taken into account for the model to maintain thermal equilibrium. This approach works as Brownian motion of segmental dislocations. Additionally, a new model for implementing the cross slip mechanism in FCC metals is developed based on results obtained by atomistic simulations. This new model is capable of simulating realistic thermal processes such as thermally activated dislocation motion during easy glide or cross slip during cold working of metals.

Simulation of Dislocation Dynamics in Ni3Al: A Study of Velocity Autocorrelations

1999 ◽  
Vol 578 ◽  
Author(s):  
C. K. Erdonmez ◽  
D. C. Chrzan
Keyword(s):  
Yield Strength ◽  
Applied Stress ◽  
Critical Stress ◽  
Threshold Stress ◽  
Dislocation Motion ◽  
Cross Slip ◽  
Dislocation Dynamics ◽  
Thermally Activated ◽  
Simple Rules ◽  
Isotropic Elasticity

AbstractThe yield strength anomaly in some L12 compounds has been linked to the thermally assisted cross slip of screw superdislocations. This work continues earlier efforts to understand the yield strength anomaly in L12 alloys using computer simulations of dislocation motion. Dislocations are modelled within isotropic elasticity theory, and simple rules are used to model the cross-slip process in the two dimensional geometry of the simulation. The velocity of a single dislocation in Ni3Al is studied as a function of the applied stress. The observed velocities vary nonlinearly with the applied stress. Further, dislocations are observed to become immobile for small applied loads. At high stresses, the dislocations are observed to advance relatively unhindered by the thermally activated cross slip process. Fluctuations in the velocity of the dislocations are studied, and their autocorrelation function shows an increased correlation time near a threshold stress. This threshold stress is identified with the critical stress proposed in earlier works.

Modeling of Dislocation Mobility in Metals: Effect of Obstacles and Thermal Processes

2001 ◽  
Vol 683 ◽  
Author(s):  
Masato Hiratani ◽  
Hussein M. Zbib
Keyword(s):  
Thermal Activation ◽  
Dislocation Dynamics ◽  
Thermal Processes ◽  
Weak Point ◽  
Dislocation Glide ◽  
Thermally Activated ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Activation Rate ◽  
Activation Event

ABSTRACTThermally activated dislocation glide velocity through weak point obstacle arrays is studied analytically and computationally. Thermal activation rate is estimated using the modified Friedel relations under the weak obstacle approximation. The average flight velocity after an activation event as a function of stress and temperature is obtained by the discrete dislocation dynamics (DD). This numerical calculation includes the effect of self-stress, interaction with electrons and phonons, and the inertial effect. These results are implemented into a phenomenological model to study the dislocation velocity under various conditions. The model can reproduce both obstacle control and drag control motion in low and high velocity regions, and a flow stress anomaly at transient regions.

scholarly journals Dislocation Topological Evolution and Energy Analysis in Misfit Hardening of Spherical Precipitate by the Parametric Dislocation Dynamics Simulation

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6368
Author(s):  
Haiwei Zheng ◽  
Jianbin Liu ◽  
Shinji Muraishi
Keyword(s):  
Slip Plane ◽  
Dislocation Line ◽  
Strain Curve ◽  
Dislocation Motion ◽  
Dislocation Dynamics ◽  
Dynamics Simulation ◽  
Slip Mechanism ◽  
Topological Evolution ◽  
Spherical Precipitate ◽  
Primary Slip Plane

Interaction of a single dislocation line and a misfit spherical precipitate has been simulated by the Parametric Dislocation Dynamics (PDD) method in this research. The internal stress inside the precipitate is deduced from Eshelby’s inclusion theory, the stress of the dislocation line and outside the precipitate is calculated by Green’s function. The influence of different relative heights of the primary slip plane on dislocation evolution is investigated, while the cross-slip mechanism and annihilation reaction are considered. The simulation results show three kinds of dislocation topological evolution: loop-forming (Orowan loop or prismatic loop), helix-forming, and gradual unpinning. The dislocation nodal force and the velocity vectors are visualized to study dislocation motion tendency. According to the stress–strain curve and the energy curves associated with the dislocation motion, the pinning stress level is strongly influenced by the topological change of dislocation as well as the relative heights of the primary slip plane.

Dislocation-mediated Mechanisms of Mass Transport around Nanoindentations in Fcc Metals

2002 ◽  
Vol 738 ◽  
Author(s):  
Oscar Rodríguez de la Fuente ◽  
Esther Carrasco ◽  
Miguel A. González ◽  
Juan M. Rojo
Keyword(s):  
Mass Transport ◽  
Surface Diffusion ◽  
Dislocation Motion ◽  
Cross Slip ◽  
Dislocation Theory ◽  
Present Evidence ◽  
Fcc Metals

ABSTRACTWe present evidence for the operation on reconstructed Au(001) of a novel mechanism, involving dislocation motion, which is much more efficient than surface diffusion to redistribute mass around nanoindentations. Cross-slip of individual dislocations generated around the indentation point, with a screw component perpendicular to the surface, is shown to be responsible for the generation of multiple-storied, crystallographically-oriented terraces around the nanoindentation points. We also show that standard dislocation theory can be used to quantitatively describe the characteristics of the dislocations involved in the different processes around the nanoindentation.

Formation and strength of dislocation junctions in FCC metals : A study by dislocation dynamics and atomistic simulations

2001 ◽  
Vol 11 (PR5) ◽  
pp. Pr5-19-Pr5-26 ◽  
Author(s):  
C. S. Shin ◽  
M. C. Fivel ◽  
D. Rodney ◽  
R. Phillips ◽  
V. B. Shenoy ◽  
...  
Keyword(s):  
Dislocation Dynamics ◽  
Atomistic Simulations ◽  
Fcc Metals
Sign in / Sign up

Export Citation Format

Share Document