518 Prismatic Dislocation Motion by Multi-scale Modeling of Discrete Dislocation Dynamics and Boundary Element Method

2005 ◽  
Vol 2005.80 (0) ◽  
pp. _5-41_-_5-42_
Author(s):  
Tomohito TSURU ◽  
Yoji SHIBUTANI
Author(s):  
Sergio Lucarini ◽  
Manas Vijay Upadhyay ◽  
Javier Segurado

Abstract FFT methods have become a fundamental tool in computational micromechanics since they were first proposed in 1994 by H. Moulinec and P. Suquet for the homogenization of composites. From that moment on many dierent approaches have been proposed for a more accurate and efficient resolution of the non- linear homogenization problem. Furthermore, the method has been pushed beyond its original purpose and has been adapted to many other problems including continuum and discrete dislocation dynamics, multi-scale modeling or homogenization of coupled problems as fracture or multiphysical problems. In this paper, a comprehensive review of FFT approaches for micromechanical simulations will be made, covering the basic mathematical aspects and a complete description of a selection of approaches which includes the original basic scheme, polarization based methods, Krylov approaches, Fourier-Galerkin and displacement-based methods. The paper will present then the most relevant applications of the method in homogenization of composites, polycrystals or porous materials including the simulation of damage and fracture. It will also include an insight into synergies with experiments or its extension towards dislocation dynamics, multi-physics and multi-scale problems. Finally, the paper will analyze the current limitations of the method and try to analyze the future of the application of FFT approaches in micromechanics.


2005 ◽  
Vol 29 (3) ◽  
pp. 403-421
Author(s):  
Kamran Behdinan ◽  
Yigui Xu ◽  
Zouheir Fawaz

A new technique called Molecular Element Method is proposed for multi-scale modeling and simulations of nano/micro-systems. In this technique, the system is divided into molecular elements whose properties are represented by sets of equivalent physical parameters obtained from atomic information. The discrete system is solved based on continuum mechanics theories. The resultant element information from system solving is then used as an external constraint for the elements, to investigate the atomic information within, using molecular dynamics calculations. Both system properties and atomic information at local zones can be obtained accurately and efficiently in this way, A crystal of Cu having 285,883 atoms with a through the thickness hole inside is investigated using this technique. Tension stresses of the crystal and the slip of atoms around the hole’s edge are revealed corresponding to five strain loads. Compared with the results obtained from the classical molecular dynamics method, the maximum stress error is 2.7%, while the computational time is only 7.2-11.8% of that taken by the classical method.


2001 ◽  
Vol 673 ◽  
Author(s):  
B. von Blanckenhagen ◽  
P. Gumbsch ◽  
E. Arzt

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.


Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 637 ◽  
Author(s):  
Siwen Gao ◽  
Zerong Yang ◽  
Maximilian Grabowski ◽  
Jutta Rogal ◽  
Ralf Drautz ◽  
...  

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.


2001 ◽  
Vol 683 ◽  
Author(s):  
Shafique M. A. Khan ◽  
Hussein M. Zbib ◽  
Darcy A. Hughes

ABSTRACTA Multi-scale model coupling discrete dislocation dynamics with continuum plasticity and finite element analysis is used to study the self-stress field of geometrically necessary (dislocation) boundaries (GNBs). The results for a single GNB are presented here. The internal structure of the GNB is obtained from the Frank's formula using experimentally measured misorientation angle/axis pair as the input. Several different types of model boundary conditions (using FEA) are analyzed together with the effect of different parameters like the domain length and mesh sensitivity. It is shown that choosing the right boundary conditions for the FEA strongly affects the predicted internal stress fields of these dislocation boundaries, particularly the long-range effect.


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