Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 44 for “"Strain localization"”.
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Microscopic Strain Localization and Damage in Multi-phase Alloys
Identifying critical factors for microscopic strain localization and damage in multiphase alloys is challenging. In addition to distinct phase-specific properties, extra complexities arise from a broad spectrum of morphology and spatial distribution of phases. Multiple deformation mechanisms can …
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Grain size evolution and strain localization in deformed marbles
In the lithosphere, strain is frequently accommodated along localized shear zones, the rheology of which are inextricably linked to their microstructural characteristics. Shear zones in orogenic belts frequently form in calcite-rich lithologies due to the relatively low strength of these rocks, …
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Strain Localization in Tungsten Heavy Alloys and Glassy Polymers
During high strain rate deformations of metals and metallic alloys, narrow regions of intense plastic deformations have been observed experimentally. The phenomenon is termed strain localization and is usually a precursor to catastrophic failure of a structure. Similar phenomenon has been observed …
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Finite Element Modeling of Strain Localization Initiated by Geometric Irregularities
The localization of deformation into zones of intense straining, known as shear bands, is a common phenomenon in inelastic deformation. The modeling of this phenomenon by the finite element method is hampered by a number of factors; the lack of a priori knowledge of the location, direction, and …
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Deformation Mechanisms and Strain Localization in the Mafic Continental Lower Crust
… that cause weakening of the lower crust and strain localization are still poorly understood. Through microstructural analysis of naturally deformed samples, this PhD aims to investigate how weakening and strain localization occurs in the mafic continental lower crust. Mafic granulites are …
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Numerical modeling of strain localization in granular materials using Cosserat theory enhanced with microfabric properties
… Lagrangian frame is used to investigate the strain localization phenomenon "shear bands" in granular materials. The micro-polar theory was used as the mathematical foundation for the continuum formulations. A laboratory testing results are used for verification and comparison with the …
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Investigating the Kinematics and Dynamics of Strain Localization in the Northern Western Branch of the East African Rift System
… grabens in northwestern Uganda. The physics of strain localization in the northern Western Branch is not well understood. This PhD study investigated the kinematics and dynamics of strain localization in the northern Western Branch through two projects: 1) investigating the contribution of deep …
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Field and theoretical investigations of strain localization: Effects of mineralogy, shear heating and grain size evolution on deformation in the Earth
… Many processes are thought to contribute to strain localization in the Earth: (1) viscous dissipation or shear heating (e.g., Braeck and Podladchikov, 2007; Braeck et al., 2009; Kameyama et al., 1999; Kelemen and Hirth, 2007; Ogawa, 1987), (2) grain size reduction (e.g., Braun et al., 1999; …
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From some obscurity to clarity in Boom clay behavior: Analysis of its coupled hydro-mechanical response in the presence of strain localization
… Belgium), through analyzing the evolution of strain localization in shear bands mode. The modeling takes into account of the initial anisotropic stresses, mechanical cross-anisotropy, anisotropic permeabilities, and gravity effects. As a result, an eye-shape extension of EDZ accompanied by an …
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Constitutive equations for granular materials : application to dry sand and powder metal
Strain localization into shear bands is commonly observed in natural soil masses, as well as in human-built embankments, footings, retaining walls and other geotechnical structures. Although the onset of strain localization can be derived from standard bifurcation analyses, few numerical …
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A Continuum Thermomechanical Model for Energetic Materials
… rich behavior, including complex wave phenomena, strain localization phenomena, and changes of material phase.
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Large-scale simulation of the mechanical response of porcine cranial bone
… simulation-based approach to describe the stress-strain response of cranial bone in mammals that can be applied to animal studies for model validation purposes as well as in human head injury studies. First, we explicitly characterized a microstructure specimen by generating large biofidelic …
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The Effect of Pre-strain and Strain Path Changes on Ductile Fracture
… The mechanical behavior of materials undergoing strain path changes can be very different from those deformed in a given direction to fracture. The work presented here employed laser drilled model materials to better understand the effect of pre-strains and strain path changes on void growth and …
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Modeling the Role of Surfaces and Grain Boundaries in Plastic Deformation
… and loading procedures. Stress and strain localization phenomena are investigated at plastically deformed boundaries in axially strain thin film samples. Joint experimental and modelling work showed increased stress states at the intersections of slip planes and grain boundaries. …
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Weak Shock Waves on a Chip: Generation and Applications
… the need to generate large-amplitude transient strain waves at a high repetition rate, this thesis introduces a novel platform for the non-destructive generation and amplification of acoustic waves with associated strain levels in the percent range — up to the formation of shock waves. The …
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Geochemical and rheological constraints on the dynamics of the oceanic upper mantle
I provide constraints on mantle convection through observations of the rheology and composition of the oceanic upper mantle. Convection cannot be directly observed, yet is a fundamental part of the plate tectonic cycle. Relative motion among plates is accommodated by localized deformation at their …
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Localization and instability in sheared granular materials: role of friction and vibration
… Zone theory, to investigate the dynamics of strain localization and its connection to stability of sliding in sheared, dry, granular materials. We consider frictional and frictionless grains as well as presence and absence of acoustic vibrations. Our results suggest that at low and …
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Geochemical and rheological constraints on the dynamics of the oceanic upper mantle
I provide constraints on mantle convection through observations of the rheology and composition of the oceanic upper mantle. Convection cannot be directly observed, yet is a fundamental part of the plate tectonic cycle. Relative motion among plates is accommodated by localized deformation at their …
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Plagioclase preferred orientation in layered mylonites : evaluation of flow laws for the lower crust
… ODP Hole 735B. Deformation temperatures are constrained by two-pyroxene thermometry, stress is estimated from grain size, and deformation mechanisms are analyzed by microstructure and the presence or absence of a lattice preferred orientation (LPO). Our analyses indicate that mylonite layers …
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An experimental study and numerical simulation of sand-steel interface behaviour.
… from the sand mass. Experiments showed that strain localization takes place in the interface layer and the thickness of the interface layer increases gradually as the shear stress increases during a test. A Fortran program for Lade's model was written to simulate numerically the sand-steel …
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