Failure Modes and Grain-Boundary Effects in Polycrystalline Materials

2004 ◽  
Vol 819 ◽  
Author(s):  
M. A. Zikry ◽  
W. M. Ashmawi
Keyword(s):  
Dislocation Density ◽  
Grain Boundary ◽  
Failure Modes ◽  
Large Strain ◽  
Ductile Failure ◽  
Boundary Effects ◽  
Polycrystalline Materials ◽  
Multiple Slip ◽  
Computational Schemes ◽  
Polycrystalline Aggregates

AbstractDislocation-density based multiple-slip constitutive formulations and specialized computational schemes are introduced to account for large-strain ductile failure modes in polycrystalline aggregates. Furthermore, new kinematically based interfacial grain-boundary regions and formulations are introduced to account for dislocation-density transmission, absorption, and pile-ups that may occur due to grain-boundary misorientations and void interactions.

Inelastic Behavior and Grain-Boundary Effects in Polycrystalline Materials

2006 ◽  
Vol 978 ◽  
Author(s):  
Jibin Shi ◽  
Mohammed Zikry ◽  
Tarek Moustafa Hatem
Keyword(s):  
Dislocation Density ◽  
Grain Boundary ◽  
Boundary Effects ◽  
Polycrystalline Materials ◽  
Inelastic Behavior ◽  
Multiple Slip ◽  
Computational Schemes ◽  
Grain Boundary Effects ◽  
Polycrystalline Aggregates

AbstractDislocation-density based multiple-slip constitutive formulations and specialized computational schemes are introduced to account for grain-boundary (GB) effects in polycrystalline aggregates. New kinematically based interfacial grain-boundary regions and formulations are introduced to account for dislocation-density transmission, absorption, and pile-ups that may occur due to CSL grain-boundary misorientations.

Microstructurally Induced Ductile Deformation Mechanisms and Grain-Boundary Effects in Polycrystalline Aggregates

1999 ◽  
Vol 578 ◽  
Author(s):  
W. M. Ashmawi ◽  
M. A. Zikry
Keyword(s):  
Dislocation Density ◽  
Grain Boundary ◽  
Large Strain ◽  
Ductile Deformation ◽  
Boundary Effects ◽  
Deformation Mechanisms ◽  
Multiple Slip ◽  
Computational Schemes ◽  
Polycrystalline Aggregates ◽  
Deformation Modes

AbstractDislocation-density based multiple-slip constitutive formulations and specialized computational schemes are introduced to account for large-strain ductile deformation modes in polycrystalline aggregates. Furthermore, new kinematically based interfacial grain-boundary regions and formulations are introduced to account for dislocation-density transmission, absorption, and pile-ups that may occur due to grain-boundary misorientations and properties.

Prediction of Grain-Boundary Interfacial Mechanisms in Polycrystalline Materials

2001 ◽  
Vol 124 (1) ◽  
pp. 88-96 ◽  
Author(s):  
W. M. Ashmawi ◽  
M. A. Zikry
Keyword(s):  
Dislocation Density ◽  
Grain Boundary ◽  
Material Behavior ◽  
Polycrystalline Materials ◽  
Total Dislocation Density ◽  
Dislocation Densities ◽  
Multiple Regions ◽  
Polycrystalline Aggregates ◽  
And Control ◽  
Deformation Modes

A multiple slip dislocation-density based crystalline formulation has been coupled to a kinematically based scheme that accounts for grain-boundary (GB) interfacial interactions with dislocation densities. Specialized finite-element formulations have been used to gain detailed understanding of the initiation and evolution of large inelastic deformation modes due to mechanisms that can result from dislocation-density pile-ups at GB interfaces, partial and total dislocation-density transmission from one grain to neighboring grains, and dislocation density absorption within GBs. These formulations provide a methodology that can be used to understand how interactions at the GB interface scale affect overall macroscopic behavior at different inelastic stages of deformation for polycrystalline aggregates due to the interrelated effects of GB orientations, the evolution of mobile and immobile dislocation-densities, slip system orientation, strain hardening, geometrical softening, geometric slip compatibility, and localized plastic strains. Criteria have been developed to identify and monitor the initiation and evolution of multiple regions where dislocation pile-ups at GBs, or partial and total dislocation density transmission through the GB, or absorption within the GB can occur. It is shown that the accurate prediction of these mechanisms is essential to understanding how interactions at GB interfaces affect and control overall material behavior.

A Micro-Mechanical Model for Grain-Boundary Cavitation in Polycrystalline Materials

2015 ◽  
Vol 665 ◽  
pp. 65-68
Author(s):  
Vincenzo Gulizzi ◽  
Alberto Milazzo ◽  
Ivano Benedetti
Keyword(s):  
Grain Boundary ◽  
Mechanical Model ◽  
Evolution Equations ◽  
Scale Model ◽  
Polycrystalline Materials ◽  
Statistical Features ◽  
Voronoi Tessellations ◽  
Numerical Tests ◽  
Cohesive Laws ◽  
Polycrystalline Aggregates

In this work, the grain-boundary cavitation in polycrystalline aggregates is investigated by means of a grain-scale model. Polycrystalline aggregates are generated using Voronoi tessellations, which have been extensively shown to retain the statistical features of real microstructures. Nucleation, thickening and sliding of cavities at grain boundaries are represented by specific cohesive laws embodying the damage parameters, whose time evolution equations are coupled to the mechanical model. The formulation is presented within the framework of a grain-boundary formulation, which only requires the discretization of the grain surfaces. Some numerical tests are presented to demonstrate the feasibility of the method.

Modeling of the Plastic Deformation of Polycrystalline Materials in Micro and Nano Level Using Finite Element Method

2013 ◽  
Vol 22 ◽  
pp. 41-60 ◽  
Author(s):  
Mohammad Jafari ◽  
Saeed Ziaei-Rad ◽  
Nima Nouri
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Finite Element ◽  
Dislocation Density ◽  
Grain Boundary ◽  
Constitutive Equations ◽  
Nanocrystalline Materials ◽  
Boundary Phase ◽  
Polycrystalline Materials ◽  
Microcrystalline Materials

Recent experiments on polycrystalline materials show that nanocrystalline materials have a strong dependency to the strain rate and grain size in contrast to the microcrystalline materials. In this study, mechanical properties of polycrystalline materials in micro and nanolevel were studied and a unified notation for them was presented. To completely understand the rate-dependent stress-strain behavior and size-dependency of polycrystalline materials, a dislocation density based model was presented that can predict the experimentally observed stress-strain relations for these materials. In nanocrystalline materials, crystalline and grain-boundary were considered as two separate phases. The mechanical properties of the crystalline phase were modeled using viscoplastic constitutive equations, which take dislocation density evolution and diffusion creep into account, while an elasto-viscoplastic model based on diffusion mechanism was used for the grain boundary phase. For microcrystalline materials, the surface-to-volume ratio of the grain boundaries is low enough to ignore its contribution to the plastic deformation. Therefore, the grain boundary phase was not considered in microcrystalline materials and the mechanical properties of the crystalline phase were modeled using an appropriate dislocation density based constitutive equation. Finally, the constitutive equations for polycrystalline materials were implemented into a finite-element code and the results obtained from the proposed constitutive equations were compared with the experimental data for polycrystalline copper and good agreement was observed.

Dislocation density based crystal plasticity finite element simulation of Al bicrystal with grain boundary effects

2014 ◽  
Vol 1651 ◽  
Author(s):  
Zhe Leng ◽  
David P. Field ◽  
Alankar Alankar
Keyword(s):  
Finite Element ◽  
Dislocation Density ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Crystal Plasticity ◽  
Microstructure Evolution ◽  
Polycrystalline Materials ◽  
Boundary Character ◽  
Crystal Plasticity Finite Element ◽  
Grain Boundary Character

ABSTRACTCrystal plasticity finite element method is a useful tool to investigate the anisotropic mechanical behaviors as well as the microstructure evolution of metallic materials and it is widely used on single crystals and polycrystalline materials. However, grain boundary involved mechanisms are barely included in the polycrystalline models, and modeling the interaction between the dislocation and the grain boundaries in polycrystalline materials in a physically consisstent way is still a long-standing, unsolved problem. In our analysis, a dislocation density based crystal plasticity finite element model is proposed, and the interaction between the dislocation density and the grain boundaries is included in the model kinematically. The model is then applied to Al bicrystals under 10% compression to investigate the effects of grain boundary character, e.g. grain boundary misorientation and grain boundary normal, on the stress state and the microstructure evolution. The modeling results suggest a reasonable correspondence with the experimental result and the grain boundary character plays a crucial role in the stress concentration and dislocation patterning.

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