Crystal Plasticity Modeling of Deformation in FCC Metals and Predictions for Recrystallization Nucleation PDF Download
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Author: Supriyo Chakraborty (Ph. D. materials engineering)
Publisher:
ISBN:
Category : Nucleation
Languages : en
Pages : 0
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Book Description
Crystal plasticity modeling was used to understand the deformation process of FCC metals and alloys. Firstly, we investigated the issue of cube texture development during static recrystallization of FCC metals, which has been vigorously debated over the last 70 years. A Full-field elasto-viscoplastic fast-Fourier transform (EVP-FFT)based crystal plasticity solver coupled with dislocation density based constitutive model was employed to understand the deformation process in copper under plane strain compression. Simulation results revealed that the grains with initially cube orientation retained a small fraction of the cube component in the deformed state, whereas, some of the grains with initially non-cube orientations developed the cube component during the deformation. For strain up to 0.46, non-cube grains which are within 10-20 deg from the ideal cube orientation showed the highest affinity to develop the cube component during deformation. However, the cube component developed during the deformation was unstable and rotated away from the cube orientation with further deformation. With increasing strain up to 1.38, some of the grains with higher angular deviation from the ideal cube orientation also developed the cube component. No particular axis preference was observed for the non-cube grains, rather, the evolution of the cube component becomes dynamic at larger strain. Rotation of the non-cube grains towards the cube component is mainly driven by the local relaxation of the imposed boundary conditions. Significant changes in lattice rotation and slip activity were observed with different relaxed constraints. Best correlation was found for the e13 strain component and the development of cube component. Analysis of the disorientation angle and the dislocation density difference with the neighboring locations showed that the cube component developed during the deformation can play a significant role during nucleation. Secondly, we used the mean-field visco-plastic self-consistent (VPSC) and the full-field EVP-FFT based crystal plasticity models to investigate the effect of different deformation modes and their interactions on the mechanical behavior and texture evolution in the equiatomic CrCoNi alloy. The presence of twin/HCP lamella has been attributed to the excellent mechanical behavior of this alloy. However, this hypothesis is not critically studied yet. An electron back scatter diffraction (EBSD) microstructure image was considered as input for both the EVP-FFT and VPSC simulations. We found the latent hardening ratio of twin to slip systems is approximately three times higher. Although twinning started to occur in those grains which are oriented along 111, substantial twinning has been found in almost all the grains at higher strain. We observed that the overall texture evolution is only influenced by slip mechanism and twinning has negligible effect on it. grain rotation predicted by the full field simulations matched well with the EBSD observation.
Author: Supriyo Chakraborty (Ph. D. materials engineering)
Publisher:
ISBN:
Category : Nucleation
Languages : en
Pages : 0
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Book Description
Crystal plasticity modeling was used to understand the deformation process of FCC metals and alloys. Firstly, we investigated the issue of cube texture development during static recrystallization of FCC metals, which has been vigorously debated over the last 70 years. A Full-field elasto-viscoplastic fast-Fourier transform (EVP-FFT)based crystal plasticity solver coupled with dislocation density based constitutive model was employed to understand the deformation process in copper under plane strain compression. Simulation results revealed that the grains with initially cube orientation retained a small fraction of the cube component in the deformed state, whereas, some of the grains with initially non-cube orientations developed the cube component during the deformation. For strain up to 0.46, non-cube grains which are within 10-20 deg from the ideal cube orientation showed the highest affinity to develop the cube component during deformation. However, the cube component developed during the deformation was unstable and rotated away from the cube orientation with further deformation. With increasing strain up to 1.38, some of the grains with higher angular deviation from the ideal cube orientation also developed the cube component. No particular axis preference was observed for the non-cube grains, rather, the evolution of the cube component becomes dynamic at larger strain. Rotation of the non-cube grains towards the cube component is mainly driven by the local relaxation of the imposed boundary conditions. Significant changes in lattice rotation and slip activity were observed with different relaxed constraints. Best correlation was found for the e13 strain component and the development of cube component. Analysis of the disorientation angle and the dislocation density difference with the neighboring locations showed that the cube component developed during the deformation can play a significant role during nucleation. Secondly, we used the mean-field visco-plastic self-consistent (VPSC) and the full-field EVP-FFT based crystal plasticity models to investigate the effect of different deformation modes and their interactions on the mechanical behavior and texture evolution in the equiatomic CrCoNi alloy. The presence of twin/HCP lamella has been attributed to the excellent mechanical behavior of this alloy. However, this hypothesis is not critically studied yet. An electron back scatter diffraction (EBSD) microstructure image was considered as input for both the EVP-FFT and VPSC simulations. We found the latent hardening ratio of twin to slip systems is approximately three times higher. Although twinning started to occur in those grains which are oriented along 111, substantial twinning has been found in almost all the grains at higher strain. We observed that the overall texture evolution is only influenced by slip mechanism and twinning has negligible effect on it. grain rotation predicted by the full field simulations matched well with the EBSD observation.
Author: Franz Roters
Publisher: John Wiley & Sons
ISBN: 3527642099
Category : Technology & Engineering
Languages : en
Pages : 188
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Book Description
Written by the leading experts in computational materials science, this handy reference concisely reviews the most important aspects of plasticity modeling: constitutive laws, phase transformations, texture methods, continuum approaches and damage mechanisms. As a result, it provides the knowledge needed to avoid failures in critical systems udner mechanical load. With its various application examples to micro- and macrostructure mechanics, this is an invaluable resource for mechanical engineers as well as for researchers wanting to improve on this method and extend its outreach.
Author: William A. Counts
Publisher:
ISBN:
Category : Crystals
Languages : en
Pages :
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Book Description
It is well documented that the mechanical response of polycrystalline metals depends on the metal's microstructure, for example the dependence of yield strength on grain size (Hall-Petch effect). Local continuum approaches do not address the sensitivity of deformation to microstructural features, and are therefore unable to capture much of the experimentally observed behavior of polycrystal deformation. In this work, a crystal plasticity model is developed that predicts a dependence of yield strength on grain size without grain size explicitly entering into the constitutive equations. The grain size dependence in the model is the result of non-local effects of geometrically necessary dislocations (GNDs), i.e. GNDs harden both the material at a point and the surrounding material. The conventional FeFp kinematics for single crystals have been augmented based on a geometric argument that accounts for the grain orientations in a polycrystal. The augmented kinematics allows an initial GND state at grain boundaries and an evolving GND state due to sub-grain formation within the grain to be determined in a consistent manner. Numerically, these non-local affects are captured using a non-local integral approach rather than a conventional gradient approach. The non-local crystal plasticity model is used to simulate the tensile behavior in copper polycrystals with grain sizes ranging from 14 to 244 micron. The simulation results show a grain size dependence on the polycrystal's yield strength, which are qualitatively in good agreement with the experimental data. However, the Hall-Petch exponent predicted by the simulations is more like d-1 rather than d-0.5. The effects of different simulation parameters including grain shape and misorientation distribution did not greatly affect the Hall-Petch exponent. The simulation results indicate that the Hall-Petch exponent is sensitive to the grain boundary strength: the Hall-Petch exponent decreases as grain boundary strength decreases. The intragrain misorientations predicted by the non-local model were compared with experiments on polycrystalline nickel. Experimentally, the intragrain misorientations were tracked by electron back scatter diffraction (EBSD) at various strain levels from the same location. On average, the simulation results predicted enough misorientation throughout the sample. However, the model did not correctly predict the spatial details of the intragrain misorientation.
Author: John Grandfield
Publisher: Springer
ISBN: 3319481444
Category : Technology & Engineering
Languages : en
Pages : 1351
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Book Description
The Light Metals symposia are a key part of the TMS Annual Meeting & Exhibition, presenting the most recent developments, discoveries, and practices in primary aluminum science and technology. Publishing the proceedings from these important symposia, the Light Metals volume has become the definitive reference in the field of aluminum production and related light metal technologies. The 2014 collection includes papers from the following symposia: •Alumina and Bauxite •Aluminum Alloys: Fabrication, Characterization and Applications •Aluminum Processing •Aluminum Reduction Technology •Cast Shop for Aluminum Production •Electrode Technology for Aluminum Production •Light-metal Matrix (Nano)-composites
Author: Jaspreet Singh Nagra
Publisher:
ISBN:
Category : Aluminum alloys
Languages : en
Pages : 191
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Book Description
The present thesis develops several new full-field, fast Fourier transform (FFT)-based crystal plasticity modelling tools for microstructure engineering. These tools are used to explore elasto-viscoplastic deformation, localized deformation, 3D grain morphology, microstructure evolution, dynamic recrystallization and their effects on formability of polycrystalline metals with particular attention paid to sheet alloys of aluminum and magnesium. The new FFT-based crystal plasticity models developed in this work overcome several inherent problems present in the well-known crystal plasticity finite element method (CP-FEM) and elasto-viscoplastic fast Fourier transform method (EVP-FFT) in solving representative volume element (RVE)-based problems. The new models have demonstrated significant fidelity in simulating various deformation phenomena in polycrystalline metals and prove to be faster and accurate alternatives for obtaining full-field solutions of micromechanical fields in aluminum and magnesium sheet alloys. In particular to the aluminum alloys, which are currently replacing heavier steel parts in the automotive industry, the sheet aluminum alloys have significantly improved corrosion resistance and strength-to-weight properties in comparison to steel. However, aluminum alloys are still outperformed by steel in terms of formability. To improve the formability of an aluminum sheet, one method is to develop physics-based predictive computational tools, which can accurately and efficiently predict the behavior of aluminum alloys and thus allow designing the microstructure with desired properties. Accordingly, in first part of this thesis, a novel numerical framework for modelling large deformation in aluminum alloys is developed. The developed framework incorporates the rate-dependent crystal plasticity theory into the fast Fourier transform (FFT)-based formulation, and this is named as rate tangent crystal plasticity-based fast Fourier transform (i.e., RTCP-FFT) framework. This framework is used as a predictive tool for obtaining stress-strain response and texture evolution in new strain-paths with minimal calibration for aluminum alloys. The RTCP-FFT framework is benchmarked against an existing FFT-based model at small strains and finite element-based model at large strains, respectively, for the case of an artificial Face Centered Cubic (FCC) polycrystal. The predictive capability as well as the computational efficiency of the developed framework are then demonstrated for aluminum alloy (AA) 5754. In the second part of this thesis, the RTCP-FFT framework, developed earlier, is coupled with the Marciniak and Kuczynski (MK) approach to establish a new full-field framework for generating forming limit diagrams (FLDs) of aluminum sheet alloys, e.g., AA3003 and AA5754. The new coupled framework is able to investigate the complex effects of grain morphology, local deformation, local texture and grain interactions on the predictions of forming limit strains. This study reveals that among the various microstructural features, the grain morphology has the strongest effect on the predicted FLDs for aluminum alloys. Furthermore, this study also suggests that the FLD predictions can be significantly improved if the actual grain structure of the material is properly accounted for in the crystal plasticity models. In addition to aluminum alloys, magnesium alloys are getting significant attention by the automotive industry due to their light weight and high specific strength. However, the automotive industry has not been able to take full advantage of the lightweight characteristic of magnesium alloys because of their poor formability at room temperature. Therefore, to enhance the workability and restore their ductility, the magnesium alloys are formed at elevated temperature. High temperature forming of magnesium alloys is often accompanied by dynamic recrystallization (DRX), which allows the final microstructure, as well as the properties of the material (e.g., initial grain size, initial texture, etc.), to be controlled. Therefore, DRX coupled with a full-field crystal plasticity FLD framework can be used as a tool to design microstructure of a material. Since it would be beneficial to be able to redesign the material properties of magnesium alloys using physics-based computational tools than using physical experiments, this work takes a step ahead towards such an outcome by presenting a new framework that predicts DRX and models its effects on the formability of magnesium alloys. Accordingly, in the third part of this thesis, a new full-field, efficient and mesh-free numerical framework, to model microstructure evolution, dynamic recrystallization (DRX) and formability in hexagonal closed-packed (HCP) metals such as magnesium alloys at warm temperatures, is developed. This coupled framework combines three new FFT-based approaches, namely: (a) crystal plasticity modelling of HCP alloys, (b) DRX model, and (c) MK model. First, a rate tangent-fast Fourier transform-based elasto-viscoplastic crystal plasticity constitutive model for HCP metals (RTCP-FFT-HCP) is developed. Then, it is coupled with a probabilistic cellular automata (CA) approach to model DRX. Furthermore, this new model is coupled with the Marciniak-Kuczynski (M-K) approach to model formability of magnesium alloys at elevated temperatures. The RTCP-FFT-HCP model computes macro stress-strain response, twinning volume fraction, micromechanical fields, texture evolution and local dislocation density. Nucleation of new grains and their subsequent growth is modeled using the cellular automata approach with probabilistic state switching rule. This framework is validated at each level of the coupling for magnesium sheet alloy, AZ31. First, the RTCP-FFT-HCP model is validated by comparing the simulated macro stress-strain responses under uniaxial tension and compression with experimental measurements at room temperature. Furthermore, the texture evolution predicted with the new model is compared with experiments. The predictions show a good agreement with experiments with high degree of accuracy. Next, the forming limit diagrams (FLDs) are simulated at 100 C, 200 C and 300 C, respectively, for AZ31 sheet alloy considering the effects of DRX. The predicted FLDs show very good agreement with the experimental measurements. The study reveals that the DRX strongly affects the deformed grain structure, grain size and texture evolution and also highlights the importance accounting for DRX during FLD simulations at high temperatures.
Author: Zhuo Zhuang
Publisher: Academic Press
ISBN: 0128145927
Category : Technology & Engineering
Languages : en
Pages : 452
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Book Description
Dislocation Based Crystal Plasticity: Theory and Computation at Micron and Submicron Scale provides a comprehensive introduction to the continuum and discreteness dislocation mechanism-based theories and computational methods of crystal plasticity at the micron and submicron scale. Sections cover the fundamental concept of conventional crystal plasticity theory at the macro-scale without size effect, strain gradient crystal plasticity theory based on Taylar law dislocation, mechanism at the mesoscale, phase-field theory of crystal plasticity, computation at the submicron scale, including single crystal plasticity theory, and the discrete-continuous model of crystal plasticity with three-dimensional discrete dislocation dynamics coupling finite element method (DDD-FEM). Three kinds of plastic deformation mechanisms for submicron pillars are systematically presented. Further sections discuss dislocation nucleation and starvation at high strain rate and temperature effect for dislocation annihilation mechanism. - Covers dislocation mechanism-based crystal plasticity theory and computation at the micron and submicron scale - Presents crystal plasticity theory without size effect - Deals with the 3D discrete-continuous (3D DCM) theoretic and computational model of crystal plasticity with 3D discrete dislocation dynamics (3D DDD) coupling finite element method (FEM) - Includes discrete dislocation mechanism-based theory and computation at the submicron scale with single arm source, coating micropillar, lower cyclic loading pillars, and dislocation starvation at the submicron scale
Author: Chaitali Shridhar Patil
Publisher:
ISBN:
Category : Polycrystals
Languages : en
Pages : 0
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Book Description
Understanding spatial evolution of micromechanical fields like effective stress or effective strain during deformation of polycrystalline materials is important for the whole life cycle of structural components, starting from process optimization to damage predictions. For this purpose, crystal plasticity modelling and simulation is an important predictive tool. Validity and accuracy of these simulations depend on the choice of the constitutive law. Therefore, this study assesses influence of the constitutive laws on the full field predictions of the crystal plasticity simulations. In this regard, we analysed two different aspects of the constitutive law. Firstly, one of the main components of the constitutive law for the plastic deformation is the hardening law. In this study, therefore, we compare full field predictions using the phenomenological Voce hardening law and the dislocation density based hardening law. As functional form of these two hardening laws is different, evolution of the critical resolved shear stress of the two laws need not to be same for all orientations during the deformation. Hence, we quantified differences in the local effective stress and texture predictions of the two laws during tensile deformation of copper. Crystal plasticity simulations were performed using a three dimensional (3D) fast Fourier transform-based elasto-viscoplastic (EVP-FFT) micromechanical solver. Simulation results show that the local distribution of stress strongly depends on the hardening rule. Average texture predicted by both the laws do not vary significantly. However, spatial orientation evolution (micro-texture) varies with increasing strain. This can be attributed to the spatially different shear strain accumulation between the two laws. Dislocation densities back calculated from the critical resolved shear stress are more homogeneous in the Voce hardening law than the predictions of the dislocation density based hardening law. Finally, dislocation density based law predicts higher accumulation of the dislocation density for the grains near the 001 orientation compared to grains with other orientations. Multiple slip activity within the 001 grains can result in higher accumulation of the dislocation density, which requires further experimental validation in the future. Secondly, cross slip of the screw dislocations is one of the important mechanisms of dislocation evolution during the deformation of medium to high stacking fault energy FCC metals. In the recent literature, it has been proposed that activation energy for the cross slip depends on the applied stress state. As a result, cross slip mediated dynamic recovery of the screw dislocations will also be influenced by the applied stress state. Hence, we incorporated the stress dependent dynamic recovery of the screw dislocations in the constitutive law. We analysed influence of the dynamic recovery on the evolution of the dislocation density and the micro-texture during the tension, compression as well as plane strain compression of polycrystalline aluminium. Even with the incorporation of the stress state dependent dynamic recovery, grain average dislocation density accumulation of the 001 grains is the highest during uniaxial deformation. Hence, detailed experimental and simulation analysis of these grains is required. In case of plane strain compression, dynamic recovery of the screw dislocations increases nucleation propensity of the cube orientation ({001}100). As the sharp cube texture is commonly observed after static recrystallization of FCC materials, our results highlight importance of dynamic recovery of the screw dislocations in the dislocation density based hardening laws.
Author: Dierk Raabe
Publisher: John Wiley & Sons
ISBN: 3527604219
Category : Technology & Engineering
Languages : en
Pages : 885
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Book Description
This book fills a gap by presenting our current knowledge and understanding of continuum-based concepts behind computational methods used for microstructure and process simulation of engineering materials above the atomic scale. The volume provides an excellent overview on the different methods, comparing the different methods in terms of their respective particular weaknesses and advantages. This trains readers to identify appropriate approaches to the new challenges that emerge every day in this exciting domain. Divided into three main parts, the first is a basic overview covering fundamental key methods in the field of continuum scale materials simulation. The second one then goes on to look at applications of these methods to the prediction of microstructures, dealing with explicit simulation examples, while the third part discusses example applications in the field of process simulation. By presenting a spectrum of different computational approaches to materials, the book aims to initiate the development of corresponding virtual laboratories in the industry in which these methods are exploited. As such, it addresses graduates and undergraduates, lecturers, materials scientists and engineers, physicists, biologists, chemists, mathematicians, and mechanical engineers.
Author: Aboozar Mapar
Publisher:
ISBN: 9780355539189
Category : Electronic dissertations
Languages : en
Pages : 207
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Book Description
Author: Carlos N. Tome
Publisher: Elsevier
ISBN: 0128207205
Category : Technology & Engineering
Languages : en
Pages : 381
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Book Description
Material Modeling with the Visco-Plastic Self-Consistent (VPSC) Approach: Theory and Practical Applications provides readers with knowledge of material viscoplasticity and robust modeling approaches for predicting plastic deformation of crystal aggregates. Visco-Plastic Self-Consistent (VPSC) is the identifier of a computer code developed for the specific mechanical regime addressed (visco-plastic: VP) and the approach used (self-consistent: SC) meant to simulate large plastic deformation of aggregates, thermo-elastic material deformation, as well as predict stress-strain response, texture evolution of aggregates and stress-strain state inside grains. This approach is very versatile and able to tackle arbitrary material symmetry (cubic, hexagonal, trigonal, orthorhombic, triclinic), twinning, and multiphase aggregates. It accounts for hardening, reorientation and shape change of individual grains, and can be applied to the deformation of metals, inter-metallics and geologic aggregates. Readers will have access to a companion website where they can download code and modify its input/output or add subroutines covering specific simulation research needs. - Highlights a modeling approach that allows readers to accurately predict stress-strain response, texture evolution of aggregates, and internal stress states inside grains while also accounting for hardening, reorientation and shape change of individual grains - Features modeling techniques that can be applied to the deformation of metals, inter-metallics and geologic aggregates - Covers the theoretical aspects of homogeneous effective medium models as they apply to the simulation of plasticity and elasticity - Provides several practical examples and applications of materials of different symmetry subjected to different deformation conditions
