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Crystal Plasticity Based Finite Element Analysis Of Deformation And Fracture Of Polycrystalline Lamellar Gamma Tial Alpha Ti3al Alloys
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Book Synopsis Crystal Plasticity-based Finite Element Analysis of Deformation and Fracture of Polycrystalline Lamellar [gamma]-TiAl + [alpha]-Ti3Al Alloys by : Surya Batchu
Download or read book Crystal Plasticity-based Finite Element Analysis of Deformation and Fracture of Polycrystalline Lamellar [gamma]-TiAl + [alpha]-Ti3Al Alloys written by Surya Batchu and published by . This book was released on 2001 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Dual-time Scale Finite Element Model for Simulating Cyclic Deformation of Polycrystalline Alloys by : Sivom Manchiraju
Download or read book A Dual-time Scale Finite Element Model for Simulating Cyclic Deformation of Polycrystalline Alloys written by Sivom Manchiraju and published by . This book was released on 2007 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: This thesis presents a dual-time scale finite element model for simulating cyclic deformation in a Titanium alloy Ti-6242. The material is characterized by crystal plasticity constitutive relations. Modeling cyclic deformation using conventional time integration algorithms in a single time scale can be prohibitive for crystal plasticity computations. Typically 3D crystal plasticity based fatigue simulations found in the literature are in the range of 100 cycles. Results are subsequently extrapolated to thousands of cycles, which can lead to considerable error in fatigue predictions. However, the dual-time scale model enables simulations up to a significantly high number of cycles to reach local states of damage initiation leading to fatigue crack growth. This formulation decomposes the governing equations into two sets of problems, corresponding to a coarse time scale (low frequency) cycle-averaged problem and a fine time scale (high frequency) oscillatory problem. A statistically equivalent 3D polycrystalline model of Ti-6242 is simulated by the crystal plasticity finite element model to study the evolution of local stresses and strains in the microstructure with cyclic loading. The comparison with the single time scale reference solution shows excellent accuracy while the efficiency gained through time-scale compression can he enormous. However, the method does not succeed under oscillatory loading conditions, in which material undergoes plastic deformation in both tensile and compressive loads with-in a cycle.
Book Synopsis Texture Informed Crystal Plasticity Finite Element Modeling of Polycrystalline Material Deformation by : Zhe Leng
Download or read book Texture Informed Crystal Plasticity Finite Element Modeling of Polycrystalline Material Deformation written by Zhe Leng and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The interaction between the dislocation and the grain boundaries is also incorporated in the model. For the near grain boundary regions, particular consideration and finite element formula is applied to account for the additional activation energy term as well as the geometric compatibility of the grain boundary during dislocation penetration events, both of the energy term and the geometric barrier depend on the grain boundary character. The formulations applied here provide a reasonable methodology to understand how the interactions between dislocation and grain boundary affect the overall mechanical behavior and the microstructure, and quantitative comparisons of predicted geometrically necessary dislocation distributions with the those determined experimentally indicates a reasonable agreement, further analysis also indicates that stress concentration, as well as the dislocation patterning, depends highly on the grain boundary characters.
Book Synopsis Crystal Plasticity Based Modelling of Surface Roughness and Localized Deformation During Bending in Aluminum Polycrystals by : Jonathan Rossiter
Download or read book Crystal Plasticity Based Modelling of Surface Roughness and Localized Deformation During Bending in Aluminum Polycrystals written by Jonathan Rossiter and published by . This book was released on 2015 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research focuses on numerical modeling of formability and instabilities in aluminum with a focus on the bending loading condition. A three-dimensional (3D) finite element analysis based on rate-dependent crystal plasticity theory has been employed to investigate non-uniform deformation in aluminum alloys during bending. The model can incorporate electron backscatter diffraction (EBSD) maps into finite element analyses. The numerical analysis not only accounts for crystallographic texture (and its evolution) but also accounts for 3D grain morphologies, because a 3D microstructure (constructed from two-dimensional EBSD data) can be employed in the simulations. The first part of the research concentrates on the effect of individual aluminum grain orientations on the developed surface roughness during bending. The standard orientations found within aluminum are combined in a systematic way to investigate their interactions and sensitivity to loading direction. The end objective of the study is to identify orientations that promote more pronounced surface roughness so that future material processes can be developed to reduce the occurrence of these orientations and improve the bending response of the material. It was identified that Goss and Brass textures have the largest negative impact on bendability of the aluminum, with Goss being the most dependent on loading direction and Brass being detrimental in all loading directions. The second part of the research focuses on the representation of grain boundaries within the models. A new modeling approach of adding 20 [mu]m wide grain boundary zones in conjunction with using single crystal material properties was developed and validated. Large columnar grain samples of aluminum were produced at McMaster University and analysed with Electron Back Scatter Diffraction to identify the grain structure prior to destructive testing. In-situ Digital Image Correlation strain measurements were taken during a mechanical strength test. The combination of initial microstructure information as well as in-situ strain distributions allowed for a study analysing the effect of adding grain boundary zones into the models. The results showed that the error in predicted strain distribution could be reduced by 60% by the addition of hard grain boundary zones. During bending simulations using the grain boundary zone modelling approach, it was found that the network of hard grain boundary zones worked to distribute the applied bending load over more of the sample as opposed to the historic approach of representing grain boundaries as neighbouring regions with different orientations. The addition of grain boundary zones into the models can improve the accuracy of future studies.
Book Synopsis Crystal Plasticity Modeling of Polycrystalline Ti-6242 and Study of Local Phenomena by : Dhyanjyoti Deka
Download or read book Crystal Plasticity Modeling of Polycrystalline Ti-6242 and Study of Local Phenomena written by Dhyanjyoti Deka and published by . This book was released on 2005 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: This work develops an experimentally validated computational model based on crystal plasticity for the analysis of two-phase [alpha]/[beta]Ti-6242 polycrystalline alloys. A rate dependent elasto-crystal plasticity model is incorporated in this model to accommodate anisotropy in material behavior and tension-compression asymmetry inherent to this alloy. A combination of detailed micro-testing, orientation imaging microscopy, computational simulations and minimization process involving Genetic algorithms (GA) is implemented in this study for careful characterization and calibration of the material parameters. Size effects are also considered in this analysis. A homogenized equivalent model of the transformed [beta] colonies is developed for incorporation in the Ti-6242 Finite Element (FE) model. The polycrystalline Ti-6242 computational model is constructed to incorporate accurate phase volume fractions as well as orientation distributions that are statistically equivalent to those observed in the OIM scans. The effects of accurate orientation, misorientation and micro-texture distributions are investigated through simulations using this computational model. The model is used to simulate constant strain rate and creep tests in compression and tension and the results are validated with experiments. The effects of microstructure and creep induced load-shedding on the localization of microstructural stresses and strains are studied for potential crack initiation criteria. Further, the microstructure has been studied at the point of failure in Ti-6242 in tension creep and dwell tests. Critical grains with the highest basal normal stress, stress in the loading direction and equivalent plastic strain are identified in the tension creep test and their specific crystallographic orientations and misorientations are studied. The critical grains in the case of dwell fatigue loading are also identified and a criterion for primary crack nucleation in Ti-6242 is developed.
Book Synopsis High-Resolution Crystal Plasticity Simulations by : Martin Diehl
Download or read book High-Resolution Crystal Plasticity Simulations written by Martin Diehl and published by Apprimus Wissenschaftsverlag. This book was released on 2016-03-02 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work the possibilities and capabilities of high-resolution crystal plasticity simulations are presented and discussed. Giving several examples, it is shown how the application of crystal plasticity simulations helps to understand the micro-mechanical behaviour of crystalline materials. To avoid the high computational costs associated with crystal plasticity simulations that arise from (i) the evaluation of the selected constitutive law, and (ii) the solution of the associated mechanical boundary value problem, both contributions to the runtime have to be kept small. This is done by (i) employing a rather simple—and therefore fast—constitutive model, and by (ii) using an effective spectral method employing fast Fourier transforms for solving the partial differential equations describing the mechanical behaviour. Here, an improved spectral solver incorporated into the Düsseldorf Advanced Material Simulation Kit (DAMASK) is used.
Book Synopsis Dislocation-based Crystal Plasticity Finite Element Modelling of Polycrystalline Material Deformation by : Chunlei Liu
Download or read book Dislocation-based Crystal Plasticity Finite Element Modelling of Polycrystalline Material Deformation written by Chunlei Liu and published by . This book was released on 2006 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt: ABAQUS/CAE is employed as a finite element method solver, and several user's subroutines were developed to model fcc crystals with 2 and 12 slip systems. The developed material models are applied to study single and polycrystal deformation behavior of copper. Interfaces between the ABAQUS user's subroutine Umat and the ABAQUS main code are developed to allow further extension of the current method.
Book Synopsis Crystal Plasticity Finite Element Simulations Using Discrete Fourier Transforms by : Hamad F. Al-Harbi
Download or read book Crystal Plasticity Finite Element Simulations Using Discrete Fourier Transforms written by Hamad F. Al-Harbi and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Crystallographic texture and its evolution are known to be major sources of anisotropy in polycrystalline metals. Highly simplified phenomenological models cannot usually provide reliable predictions of the materials anisotropy under complex deformation paths, and lack the fidelity needed to optimize the microstructure and mechanical properties during the production process. On the other hand, physics-based models such as crystal plasticity theories have demonstrated remarkable success in predicting the anisotropic mechanical response in polycrystalline metals and the evolution of underlying texture in finite plastic deformation. However, the integration of crystal plasticity models with finite element (FE) simulations tools (called CPFEM) is extremely computationally expensive, and has not been adopted broadly by the advanced materials development community. The current dissertation has mainly focused on addressing the challenges associated with integrating the recently developed spectral database approach with a commercial FE tool to permit computationally efficient simulations of heterogeneous deformations using crystal plasticity theories. More specifically, the spectral database approach to crystal plasticity solutions was successfully integrated with the implicit version of the FE package ABAQUS through a user materials subroutine, UMAT, to conduct more efficient CPFEM simulations on both fcc and bcc polycrystalline materials. It is observed that implementing the crystal plasticity spectral database in a FE code produced excellent predictions similar to the classical CPFEM, but at a significantly faster computational speed. Furthermore, an important application of the CPFEM for the extraction of crystal level plasticity parameters in multiphase materials has been demonstrated in this dissertation. More specifically, CPFEM along with a recently developed data analysis approach for spherical nanoindentation and Orientation Imaging Microscopy (OIM) have been used to extract the critical resolved shear stress of the ferrite phase in dual phase steels. This new methodology offers a novel efficient tool for the extraction of crystal level hardening parameters in any single or multiphase materials.
Book Synopsis International Aerospace Abstracts by :
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1997 with total page 940 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Crystal Plasticity Modeling of Fully Lamellar Titanium Aluminide Alloys by : Jan Eike Schnabel
Download or read book Crystal Plasticity Modeling of Fully Lamellar Titanium Aluminide Alloys written by Jan Eike Schnabel and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In the present thesis, a thermomechanically coupled, defect density based crystal plasticity model is presented. This model accounts for the evolution of dislocation densities and twinned volume fractions on different slip and twinning systems during plastic deformation and thermal recovery. Considering the evolution of dislocation densities and twinned volume fractions allows a physics based formulation of the work hardening model and enables a physically meaningful representation of dissipation and stored energy of cold work in the applied thermomechanical framework. In the course of this thesis, the presented crystal plasticity model was applied to investigate several aspects of the plastic deformation behavior of fully lamellar titanium aluminide alloys. After calibrating the work hardening model to fit experimental results, it was successfully used to relate specifics of the macroscopic stress-strain response of fully lamellar titanium aluminides to the work hardening interactions on the microscale. By combining numerical studies and experimental findings from literature, it was further possible to identify and consequently model the relative contribution of the different coexisting microstructural interfaces to the macroscopic yield strength. With this microstructure sensitive model formulation, the influence of the microstructural parameters on the inhomogeneous microplasticity of fully lamellar titanium aluminides was studied. Due to its defect density based formulation, the model enabled trends in the static recovery behavior to be investigated. Finally, the model was extended in order to account for the anomalous dependence of the yield strength of fully lamellar titanium aluminides on temperature.
Book Synopsis Matrix and Interface Deformation in High Temperature Intermetallic Compounds and Composites by :
Download or read book Matrix and Interface Deformation in High Temperature Intermetallic Compounds and Composites written by and published by . This book was released on 1995 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: This project is concerned with the experimental and theoretical study of deformation and fracture mechanisms in MoSi(2) and TiAl alloy materials and of interfaces between these alloys. Past work has included (1) identifying dominant deformation mechanisms in MoSi2, (2) predicting the geometric hardening for suggested slip systems in MoSi2, and (3) finite element simulations of the deformation in intermetallic compounds (TiAl, MoSi2) pertaining to the microstructural subtleties in polycrystalline aggregates. More recent work has been concerned with the modeling of lamella microstructures in Ti3Al/TiAl and TiAl alloys. In particular, the framework has been created to perform detailed modeling of deformation processing in TiAl alloys. jg p1.
Book Synopsis Crystal Plasticity Finite Element Analysis of Deformation Behaviour in SAC305 Solder Joint by : Payam Darbandi
Download or read book Crystal Plasticity Finite Element Analysis of Deformation Behaviour in SAC305 Solder Joint written by Payam Darbandi and published by . This book was released on 2014 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A New Crystal Plasticity Formulation to Simulate Large-strain Plasticity of Polycrystalline Metals at Elevated Temperatures by : Edward D. Cyr
Download or read book A New Crystal Plasticity Formulation to Simulate Large-strain Plasticity of Polycrystalline Metals at Elevated Temperatures written by Edward D. Cyr and published by . This book was released on 2017 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation explores the plasticity polycrystalline metals, with particular attention paid to aluminum and its alloys. Specifically aluminum Al-Mg sheet alloys, which are currently replacing steel parts for panel and some structural componentry in the automotive industry. At the forefront of this transition, is the problem of poor room-temperature formability of the aluminum sheet when compared to its steel counterparts. A promising solution to this has been the use of warm-forming to increase formability, preventing redesign of automotive parts from steel to aluminum (Li and Ghosh, 2003). In this thesis, a new constitutive framework and methodology is developed to accurately model elevated temperature behaviour of polycrystalline aluminum. This study describes a picture of the physics behind slip dominated deformation in polycrystalline metals, and the mechanical characterization techniques used to determine modeling parameters for crystal plasticity. A review on modeling techniques and published work on the versatility of crystal plasticity theory and application is also presented. An initial model is then developed for a fully temperature dependent crystal plasticity framework. The model employs a generic hardening law to study the effect of temperature on material hardening, and conclusions are made on the lack of microstructural correlation between the model and physical behaviour of the material. The same framework is then implemented in the well known Marciniak-Kuzynski (1967) based limit strain formulation as an application study with Chang and Asaro (1981) type hardening. Temperature dependency is studied and formability is predicted for different aluminum alloys. The study reveals that, again, phenomenological-based hardening is only satisfactory for predicting elevated-temperature behaviour, and results are very sensitive to model input parameters. In the second half of this dissertation, a physical model is carefully developed from fundamental dislocation theories. The model is formulated on the basis of accumulation of dislocations as the dominating strengthening mechanism in polycrystals, introduces recovery as a thermally activated process leading to temperature dependent softening. The model is used to study temperature dependency of slip deformation in pure aluminum, and the correlation between physical processes and model parameters. The model is able to capture and predict deformation response, as well as suggest explanation to the influence of temperature on microstructural behaviour. Finally, the model is applied to study the temperature dependency of microstructural parameters in 5xxx series Al-Mg sheet alloys. Experimental data is used to characterized material parameters at warm forming temperatures, and the model is used to predict stress-strain response. The model is then used to discuss the effect of temperature on two different alloys and suggests explanation on the microstructural causes leading to variation hardening behaviour between the two alloys over the temperature range studied. The work then concludes the improvement of model predictability, and the utility of such a model in microstructural design.
Book Synopsis Micromechanical Modeling of the Deformation Behavior of Polycrystalline Gamma-TiAl Based Alloys by : Wilfried Thomas Marketz
Download or read book Micromechanical Modeling of the Deformation Behavior of Polycrystalline Gamma-TiAl Based Alloys written by Wilfried Thomas Marketz and published by . This book was released on 2001 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Grain-Scale Crystal Plasticity Finite Element (FE) Simulations of Waspaloy During Hot Deformation by :
Download or read book Grain-Scale Crystal Plasticity Finite Element (FE) Simulations of Waspaloy During Hot Deformation written by and published by . This book was released on 2004 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report results from a contract tasking Max-Planck-Institute for Eisenforschung as follows: The project aims to understand and predict the mechanical, crystallographic, and topological behavior of gamma grains in Waspaloy during plastic deformation at high temperature. The study will be conducted by use of a crystal plasticity finite element method that updates the local crystallographic and hardening state of the material via integration of the evolution equations for the crystal lattice orientation and the critical resolved shear stress.
Book Synopsis Development of a 3D Microstructure Sensitive Crystal Plasticity Model for Aluminum by : Alankar Alankar
Download or read book Development of a 3D Microstructure Sensitive Crystal Plasticity Model for Aluminum written by Alankar Alankar and published by . This book was released on 2010 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Experimental Investigation and Multi-scale Modeling of Strain Localization, Shear Banding and Fracture in Precipitation Hardened Aluminum Alloys by : Waqas Muhammad
Download or read book Experimental Investigation and Multi-scale Modeling of Strain Localization, Shear Banding and Fracture in Precipitation Hardened Aluminum Alloys written by Waqas Muhammad and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Finite element (FE) simulations are widely used in automotive design processes to model the forming and crashworthiness behavior of structural materials. Comprehensive material characterization and the availability of suitable constitutive models are prerequisites for accurate modeling of these operations. Numerical modeling of formability and crashworthiness is complex as it involves large deformations, instability, ruptures, damage propagation, and fracture. The effectiveness of computer-aided engineering (CAE) based design and performance evaluations significantly depends on the ability of numerical models to predict the material work hardening behavior, flow localization and fracture. This thesis presents a combined experimental and numerical study to explore microstructure property relationships involving strain localization, shear banding and fracture in precipitation hardened aluminum alloys. More specifically, the AA6xxx series aluminum alloys are of key interest for automotive applications, requiring good formability, hemmability and crash energy absorption characteristics. The goal of this work is to enhance the existing experimental understanding and modeling capabilities with respect to strain localization, shear banding and fracture in AA6xxx series precipitation hardened aluminum alloys, through development and coupling of multiscale modeling frameworks with advanced constitutive models for material work hardening and failure. In these regards, a crystal plasticity based constitutive hardening model is developed to account for the intragranular backstresses that arise from the formation of deformation induced dislocation substructure in precipitation hardened aluminum alloys. Based on thorough experimental investigation, it is learned that the substructure starts as pinned dislocation tangles with some regions having relatively high dislocation content while others being virtually dislocation free. With persistent deformation the substructure evolves into a well defined equiaxed cell/subgrain structure with majority of dislocations being trapped at the subgrain cell wall boundaries. The substructure induces intragranular backstresses due to blockage of dislocation passage leading to the experimentally observed Bauschinger effect at the macroscopic scale. The proposed hardening model accounts for these induced stresses and successfully predicts the experimentally measured flow behavior during cyclic simple shear and cyclic TCT and CTC loadings of AA6063. More importantly, the new backstress hardening model successfully reproduces the experimentally observed Bauschinger effect upon loading reversal. It is further shown that the crystallographic texture evolves significantly during cyclic simple shear deformation and the model successfully predicts the experimentally observed texture evolution. The study reveals that for proper prediction of flow behavior and the experimentally observed Bauschinger effect in precipitation hardened aluminum alloys, a physically motivated model that can account for the induced internal stresses, must be employed to describe material hardening on a polycrystalline level. Next, a multiscale modeling approach is developed where a macro-scale component level simulation is performed using conventional phenomenological plasticity and the boundary conditions of the region of interest are extracted and applied to the crystal plasticity based finite element model to account for the relevant microstructural physics. The proposed approach is successfully validated by simulating wrap-bending deformation of AA6063 and by comparing the observed texture evolution, slip band formation within grains, through thickness strain localization and the development of surface roughness with corresponding experimental data. The proposed approach enhances existing modeling capabilities for better predictability of material response under complex loading paths. After developing the multiscale framework, a new constitutive approach is developed to predict failure by extending the existing nano-void theory of ductile failure to precipitation hardened aluminum alloys by accounting for the effects of precipitation induced dislocation substructure on point defect generation. A new evolution law for the effective obstacle strength associated with substructure evolution is incorporated into the formulation. The proposed failure criterion is successfully validated against experimental data and its versatility is demonstrated by coupling the failure criterion with stress-strain data generated through crystal plasticity simulations, to predict failure strain for arbitrary loading - stress triaxiality conditions. Next, a comprehensive experimental investigation is performed to study the relationship between microstructure, plastic deformation and fracture behavior of precipitation hardened aluminum alloy AA6016 during bending. It is shown that the bendability of AA6016 alloy is limited by the formation of severe surface undulations and surface cracking, which are associated with the heterogenous nature of slip concentrating into coarse slip bands and intense shear banding originating from surface low cusps in the form of mutually orthogonal transgranular bands. Micro-cracks originate from low cusp regions along the outer tensile surface and propagate along the intensely sheared planes within shear bands. Results show that grains with S texture component are prone to shear banding and failure during bending and the contrary is true for Cube oriented grains. It is observed that intergranular micro-void nucleation and crack propagation is favored in areas with high grain boundary misorientations and intense slip band impingements along boundaries, perhaps due to the reduction in local cohesive strength of such boundaries. Finally, the developed multiscale modeling approach in conjunction with the newly developed hardening and failure models for age-hardenable aluminum alloys are applied to predict the experimentally observed shear banding and fracture behavior of AA6016 during bending. The simulated results successfully predict the experimentally observed shear banding and the predominant transgranular fracture behavior. It is shown that the advancing crack tip alternates from a less critical localization condition to a more critical one, as it requires lesser energy for the creation of new fracture surfaces while still sustaining the imposed plastic deformation. It is observed that Copper, Brass and Cube texture components show good resistance to shear banding and are therefore characterized as high bendability components, whereas the contrary is true for the S texture component. Lastly, the coupled numerical framework, presented herein, provides an excellent tool for CAE, virtual material characterization and analysis of microstructure-property relationships.
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