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Showing 1 to 20 of 28 for “"Polycrystal"”.
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Stochastic Mean-Field Polycrystal Plasticity Methods
Finally, we incorporate the STM in a finite element simulation of the Taylor impact of two tantalum specimens. Our simulation predictions mimic the texture and deformation data measured from a powder metallurgy specimen. However, round-corner square rolled (RCSR) specimen simulations over-predict …
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Kinetics of Plastic Flow in Polycrystal Plasticity
An elasto-viscoplastic polycrystal plasticity model is developed that considers the kinetics of plastic flow. Strain rate and temperature dependencies, included in the single crystal constitutive response, are based on the isotropic mechanical threshold stress continuum model. A modified power law …
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Polycrystal plasticity : constitutive modeling and deformation processing
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1992.
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Deformation Mechanisms at Grain Boundaries in Polycrystal Plasticity
Strengthening by grain boundaries is commonly attributed to the dislocation pile-up at the boundary describing the effect of grain size, i.e. the Hall-Petch relation. In this work, the importance of the boundary structure is emphasized, along with grain size, in predicting the flow stress using …
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Percolation in Two-Dimensional Grain Boundary Structures and Polycrystal Property Closures
<p>The thesis addresses two topics in the study of material properties as determined by the microstructure. The first topic involves percolation as a tool in relating the grain boundary structure to global properties such as fracture and corrosion resistance. The second investigates optimization …
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Effects of Ionizing Radiation and Thermal Treatment on the Optical Transmittance of Polycrystal CsI
Made available in DSpace on 2017-07-06T18:55:55Z (GMT). No. of bitstreams: 3 Procoli_Alfredo_MS.pdf: 53494592 bytes, checksum: 51ba486fae18e6069c981234e27f2453 (MD5) Procoli_Alfredo_MS_ABS.pdf: 1014084 bytes, checksum: fe782389c66fbc39dd079c9fe74b9640 (MD5) license.txt: 4813 bytes, checksum: …
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Polycrystal Modeling of Precipitate Effects on the Mechanical Behavior of an Aluminum -Copper Alloy
… results were compared to single crystal and polycrystal compression experiments. Accurate simulations were obtained for most of the aging conditions and the correct trends due to precipitate-induced anisotropy were predicted.
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Specific Heat and Thermodynamic Properties of Metallic Systems: Instrumentation and Analysis
… 0.5 K. For the α-uranium, the specific heat of a polycrystalline sample was compared to that of a single crystal, and it was found that there was a significant difference in the specific heats, which has been attributed to microstrain in the polycrystal. The third law entropy for the polycrystal …
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Grain boundary network design
Grain boundaries in polycrystals form a complex interconnected network of intercrystalline interfaces. The crystallographic character of individual grain boundaries and the network structure of the grain boundary ensemble have been experimentally observed to have a strong influence on many …
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Grain-Boundary Kinetics And Nonequilibrium Grain-Boundary Structure
Microstructure of polycrystalline materials can be described as grain boundary (GB) networks; hence, GBs play major role in a wide-range of polycrystal properties. Control over GB kinetics provides effective means to tailor polycrystal properties through material processing. Understanding and …
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Domain structure, phase transformation, mechanical behavior and shape memory effect in a rare-earth orthoniobate lanthanum niobate
… and (4) exploring the shape memory effect in polycrystal ceramic LaNbO$\sb4$."
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A Multiscale Method for Simulating Fracture in Polycrystalline Metals
… approach is advanced to model microscale polycrystal domains in which atomistically-based cohesive zone parameters are incorporated into special directional decohesion finite elements that automatically apply appropriate ductile or brittle cohesive properties depending on the direction of …
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Constitutive equations for superelasticity in crystalline shape-memory materials
A crystal-mechanics-based constitutive model for polycrystalline shape-memory materials has been developed. The model has been implemented in a finite-element program. Finite-element calculations of polycrystal response were performed using two methods: (1) The full-finite element method where each …
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On the role of lattice defects interactions on strain hardening: A study from discrete dislocation dynamics to crystal plasticity modelling
… performing DDD simulations in low-symmetry polycrystals. The information extracted from the collective dislocation interactions are then passed to a series of constitutive models, and later used to quantify their effects at the scale of the polycrystal. For such purpose, a constitutive …
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Modeling of diffusional creep and stress relaxation in copper grains during manufacturing of microelectronic integrated circuits
… the effect of grain size on creep rate in a polycrystal under external load. The approach has been applied to study the stress relaxation in a typical Cu-Ta-dielectric structure subjected to thermal loads.</p><p>To improve the computational efficiency of the diffusional creep modeling, we …
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Exploration of incompatibility in Al-Li alloys using high energy diffraction microscopy and a crystal plasticity model
… High Energy Diffraction Microscopy (HEDM) and polycrystal plasticity simulations to study the local evolution of lattice strains to gain insight into the development of incompatibility. The identification of factors that initiate and drive delamination fracture, such as the development of shear …
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Multiscale strength homogenization : application to shale nanoindentation
… the elementary building block of shale is a clay polycrystal. The use of these scaling relations in the Level II-homogenization provides a first-order model for the prediction of the macroscopic strength properties of shale, based on only two parameters that delineate shale's macroscopic …
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Microporoelastic modeling of organic-rich shales
… (Mori-Tanaka) for immature systems and a polycrystal/ granular morphology for mature systems. Also, we show that interfaces play a role on the effective elasticity of mature organic-rich shales. The models are calibrated by means of ultrasonic pulse velocity measurements of elastic …
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Towards Crack-Resistant Polycrystalline Zirconia Shape-Memory Ceramics with Low Hysteresis
… materials from reaching their full potential: i) polycrystals catastrophically crack during the martensitic transformation, and ii) the transformation exhibits a large hysteresis of over 150 K. It is yet unknown what drives these phenomena and how they can be avoided. In this thesis, these …
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Influence of surface treatment on veneering porcelain shear bond strength to zirconia after cyclic loading
… Yttria-partially stabilized tetragonal zirconia polycrystal (Y-TZP) all-ceramic restorations have been reported to suffer from chipping or cracking of the veneering porcelain (VP) as the most common complication. There is little information in the literature regarding the influence of surface …
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