Milan Ardeljan - Academia.edu (original) (raw)

Papers by Milan Ardeljan

Research paper thumbnail of Elastic constants of pure body-centered cubic Mg in nanolaminates

Computational Materials Science

Research paper thumbnail of Room temperature deformation mechanisms of Mg/Nb nanolayered composites

Journal of Materials Research

Research paper thumbnail of Mechanical response, twinning, and texture evolution of WE43 magnesium-rare earth alloy as a function of strain rate: Experiments and multi-level crystal plasticity modeling

International Journal of Plasticity

Research paper thumbnail of An automated procedure for geometry creation and finite element mesh generation: Application to explicit grain structure models and machining distortion

Computational Materials Science

Research paper thumbnail of Explicit modeling of double twinning in AZ31 using crystal plasticity finite elements for predicting the mechanical fields for twin variant selection and fracture analyses

Research paper thumbnail of Effect of dislocation density-twin interactions on twin growth in AZ31 as revealed by explicit crystal plasticity finite element modeling

International Journal of Plasticity

Research paper thumbnail of The plasticity of highly oriented nano-layered Zr/Nb composites

Acta Materialia, 2016

In prior work, bulk lamellar composites of pure zirconium and niobium (Zr/Nb) were manufactured b... more In prior work, bulk lamellar composites of pure zirconium and niobium (Zr/Nb) were manufactured by accumulative roll bonding (ARB). After the substantial amounts of straining required to refine the layers to nanoscale dimensions, formation of highly oriented Zr crystals was observed. In this work, we employ a spatially resolved multiscale crystal plasticity based model in 3D to study the orientational stability of Zr single crystals and Zr/Nb bicrystals during rolling deformation. The analysis reveals that predominant texture components arise due to substantially reduced ratios of slip resistances among the prismatic, pyramidal I <c+a>, and basal slip systems. In support, density functional theory (DFT) calculations of generalized stacking fault energy curves on these three slip systems suggest that the ratio of critical stresses to form these dislocations are within 2.5 times. This finding of reduced anisotropy in Zr at the nanoscale can provide insight into the design of nano-structuring processes for target textures, such as those containing highly oriented grains.

Research paper thumbnail of Strain rate and temperature sensitive multi-level crystal plasticity model for large plastic deformation behavior: Application to AZ31 magnesium alloy

International Journal of Plasticity, 2016

Research paper thumbnail of Explicit incorporation of deformation twins into crystal plasticity finite element models

Computer Methods in Applied Mechanics and Engineering, 2015

Deformation twinning is a subgrain mechanism that strongly influences the mechanical response and... more Deformation twinning is a subgrain mechanism that strongly influences the mechanical response and microstructural evolution of metals especially those with low symmetry crystal structure. In this work, we present an approach to modeling the morphological and crystallographic reorientation associated with the formation and thickening of a twin lamella within a crystal plasticity finite element (CPFE) framework. The CPFE model is modified for the first time to include the shear transformation strain associated with deformation twinning. Using this model, we study the stress-strain fields and relative activities of the active deformation modes before and after the formation of a twin and during thickening within the twin, and in the parent grain close to the twin and away from the twin boundaries. These calculations are carried out in cast uranium (U), which has an orthorhombic crystal structure and twins predominantly on the < > systems under ambient conditions. The results show that the resolved shear stresses on a given twin system on the twin-parent grain interface and in the parent are highly inhomogeneous. We use the calculated mechanical fields to determine whether the twin evolution occurs via thickening of the existing twin lamella or formation of a second twin lamella. The analysis suggests that the driving force for thickening the existing twin lamella is low and that formation of multiple twin lamellae is energetically more favorable. The overall modeling framework and insight into why twins in U tend to be thin are described and discussed in this paper.

Research paper thumbnail of Enhancement of orientation gradients during simple shear deformation by application of simple compression

Journal of Applied Physics, 2015

ABSTRACT

Research paper thumbnail of A study of microstructure-driven strain localizations in two-phase polycrystalline HCP/BCC composites using a multi-scale model

International Journal of Plasticity, 2015

Research paper thumbnail of Three dimensional predictions of grain scale plasticity and grain boundaries using crystal plasticity finite element models

Computer Methods in Applied Mechanics and Engineering, 2014

Highlights • Evolution of grain and grain boundary structure during plastic deformation is studie... more Highlights • Evolution of grain and grain boundary structure during plastic deformation is studied using crystal plasticity. • Procedures for creation, meshing and quantitative analysis of grain structure and grain boundaries are developed. • Systematic comparison between predictions on analogous 3D and 2D microstructures is conducted.

Research paper thumbnail of Texture evolution in two-phase Zr/Nb lamellar composites during accumulative roll bonding

International Journal of Plasticity, 2014

ABSTRACT We study the texture evolution and deformation mechanisms in a Zr/Nb layered composite u... more ABSTRACT We study the texture evolution and deformation mechanisms in a Zr/Nb layered composite using a combination of electron backscattered diffraction, dislocation density evolution modeling, and polycrystal plasticity simulations. Zr/Nb composites with individual layer thicknesses ranging from one-millimeter to four-micrometers were successfully fabricated at room temperature by accumulative roll bonding. Measured texture data during rolling and stress-strain curves in compression are presented. Under severe plastic deformation, we show that the textures of each polycrystalline phase correspond to textures of severely rolled single-phase rolled Zr and Nb. A visco-plastic self-consistent (VPSC)-dislocation density based model is applied to predict the deformation textures in the individual phases. The model indicates that large-strain deformation in Zr is accommodated by prismatic, pyramidal, and anomalously basal slip, and in Nb by both {110} and {112} slip. Our findings suggest that the polycrystalline layers of four micrometers per phase are still too coarse for the bimetal interfaces to have an effect on the texture evolution.

Research paper thumbnail of Texture evolution in two-phase Zr/Nb lamellar composites during accumulative roll bonding

ABSTRACT We study the texture evolution and deformation mechanisms in a Zr/Nb layered composite u... more ABSTRACT We study the texture evolution and deformation mechanisms in a Zr/Nb layered composite using a combination of electron backscattered diffraction, dislocation density evolution modeling, and polycrystal plasticity simulations. Zr/Nb composites with individual layer thicknesses ranging from one-millimeter to four-micrometers were successfully fabricated at room temperature by accumulative roll bonding. Measured texture data during rolling and stress-strain curves in compression are presented. Under severe plastic deformation, we show that the textures of each polycrystalline phase correspond to textures of severely rolled single-phase rolled Zr and Nb. A visco-plastic self-consistent (VPSC)-dislocation density based model is applied to predict the deformation textures in the individual phases. The model indicates that large-strain deformation in Zr is accommodated by prismatic, pyramidal, and anomalously basal slip, and in Nb by both {110} and {112} slip. Our findings suggest that the polycrystalline layers of four micrometers per phase are still too coarse for the bimetal interfaces to have an effect on the texture evolution.

Research paper thumbnail of Enhancement of orientation gradients during simple shear deformation by application of simple compression

Journal of Applied Physics, 2015

ABSTRACT

Research paper thumbnail of Elastic constants of pure body-centered cubic Mg in nanolaminates

Computational Materials Science

Research paper thumbnail of Room temperature deformation mechanisms of Mg/Nb nanolayered composites

Journal of Materials Research

Research paper thumbnail of Mechanical response, twinning, and texture evolution of WE43 magnesium-rare earth alloy as a function of strain rate: Experiments and multi-level crystal plasticity modeling

International Journal of Plasticity

Research paper thumbnail of An automated procedure for geometry creation and finite element mesh generation: Application to explicit grain structure models and machining distortion

Computational Materials Science

Research paper thumbnail of Explicit modeling of double twinning in AZ31 using crystal plasticity finite elements for predicting the mechanical fields for twin variant selection and fracture analyses

Research paper thumbnail of Effect of dislocation density-twin interactions on twin growth in AZ31 as revealed by explicit crystal plasticity finite element modeling

International Journal of Plasticity

Research paper thumbnail of The plasticity of highly oriented nano-layered Zr/Nb composites

Acta Materialia, 2016

In prior work, bulk lamellar composites of pure zirconium and niobium (Zr/Nb) were manufactured b... more In prior work, bulk lamellar composites of pure zirconium and niobium (Zr/Nb) were manufactured by accumulative roll bonding (ARB). After the substantial amounts of straining required to refine the layers to nanoscale dimensions, formation of highly oriented Zr crystals was observed. In this work, we employ a spatially resolved multiscale crystal plasticity based model in 3D to study the orientational stability of Zr single crystals and Zr/Nb bicrystals during rolling deformation. The analysis reveals that predominant texture components arise due to substantially reduced ratios of slip resistances among the prismatic, pyramidal I <c+a>, and basal slip systems. In support, density functional theory (DFT) calculations of generalized stacking fault energy curves on these three slip systems suggest that the ratio of critical stresses to form these dislocations are within 2.5 times. This finding of reduced anisotropy in Zr at the nanoscale can provide insight into the design of nano-structuring processes for target textures, such as those containing highly oriented grains.

Research paper thumbnail of Strain rate and temperature sensitive multi-level crystal plasticity model for large plastic deformation behavior: Application to AZ31 magnesium alloy

International Journal of Plasticity, 2016

Research paper thumbnail of Explicit incorporation of deformation twins into crystal plasticity finite element models

Computer Methods in Applied Mechanics and Engineering, 2015

Deformation twinning is a subgrain mechanism that strongly influences the mechanical response and... more Deformation twinning is a subgrain mechanism that strongly influences the mechanical response and microstructural evolution of metals especially those with low symmetry crystal structure. In this work, we present an approach to modeling the morphological and crystallographic reorientation associated with the formation and thickening of a twin lamella within a crystal plasticity finite element (CPFE) framework. The CPFE model is modified for the first time to include the shear transformation strain associated with deformation twinning. Using this model, we study the stress-strain fields and relative activities of the active deformation modes before and after the formation of a twin and during thickening within the twin, and in the parent grain close to the twin and away from the twin boundaries. These calculations are carried out in cast uranium (U), which has an orthorhombic crystal structure and twins predominantly on the < > systems under ambient conditions. The results show that the resolved shear stresses on a given twin system on the twin-parent grain interface and in the parent are highly inhomogeneous. We use the calculated mechanical fields to determine whether the twin evolution occurs via thickening of the existing twin lamella or formation of a second twin lamella. The analysis suggests that the driving force for thickening the existing twin lamella is low and that formation of multiple twin lamellae is energetically more favorable. The overall modeling framework and insight into why twins in U tend to be thin are described and discussed in this paper.

Research paper thumbnail of Enhancement of orientation gradients during simple shear deformation by application of simple compression

Journal of Applied Physics, 2015

ABSTRACT

Research paper thumbnail of A study of microstructure-driven strain localizations in two-phase polycrystalline HCP/BCC composites using a multi-scale model

International Journal of Plasticity, 2015

Research paper thumbnail of Three dimensional predictions of grain scale plasticity and grain boundaries using crystal plasticity finite element models

Computer Methods in Applied Mechanics and Engineering, 2014

Highlights • Evolution of grain and grain boundary structure during plastic deformation is studie... more Highlights • Evolution of grain and grain boundary structure during plastic deformation is studied using crystal plasticity. • Procedures for creation, meshing and quantitative analysis of grain structure and grain boundaries are developed. • Systematic comparison between predictions on analogous 3D and 2D microstructures is conducted.

Research paper thumbnail of Texture evolution in two-phase Zr/Nb lamellar composites during accumulative roll bonding

International Journal of Plasticity, 2014

ABSTRACT We study the texture evolution and deformation mechanisms in a Zr/Nb layered composite u... more ABSTRACT We study the texture evolution and deformation mechanisms in a Zr/Nb layered composite using a combination of electron backscattered diffraction, dislocation density evolution modeling, and polycrystal plasticity simulations. Zr/Nb composites with individual layer thicknesses ranging from one-millimeter to four-micrometers were successfully fabricated at room temperature by accumulative roll bonding. Measured texture data during rolling and stress-strain curves in compression are presented. Under severe plastic deformation, we show that the textures of each polycrystalline phase correspond to textures of severely rolled single-phase rolled Zr and Nb. A visco-plastic self-consistent (VPSC)-dislocation density based model is applied to predict the deformation textures in the individual phases. The model indicates that large-strain deformation in Zr is accommodated by prismatic, pyramidal, and anomalously basal slip, and in Nb by both {110} and {112} slip. Our findings suggest that the polycrystalline layers of four micrometers per phase are still too coarse for the bimetal interfaces to have an effect on the texture evolution.

Research paper thumbnail of Texture evolution in two-phase Zr/Nb lamellar composites during accumulative roll bonding

ABSTRACT We study the texture evolution and deformation mechanisms in a Zr/Nb layered composite u... more ABSTRACT We study the texture evolution and deformation mechanisms in a Zr/Nb layered composite using a combination of electron backscattered diffraction, dislocation density evolution modeling, and polycrystal plasticity simulations. Zr/Nb composites with individual layer thicknesses ranging from one-millimeter to four-micrometers were successfully fabricated at room temperature by accumulative roll bonding. Measured texture data during rolling and stress-strain curves in compression are presented. Under severe plastic deformation, we show that the textures of each polycrystalline phase correspond to textures of severely rolled single-phase rolled Zr and Nb. A visco-plastic self-consistent (VPSC)-dislocation density based model is applied to predict the deformation textures in the individual phases. The model indicates that large-strain deformation in Zr is accommodated by prismatic, pyramidal, and anomalously basal slip, and in Nb by both {110} and {112} slip. Our findings suggest that the polycrystalline layers of four micrometers per phase are still too coarse for the bimetal interfaces to have an effect on the texture evolution.

Research paper thumbnail of Enhancement of orientation gradients during simple shear deformation by application of simple compression

Journal of Applied Physics, 2015

ABSTRACT