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 30 for “"Stress Redistribution"”.
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Stress Redistribution in Berea Sandstone Samples Using Acoustic Emission Tomography in the Laboratory
… velocity are typically representative of higher stress concentrations, whereas areas of low velocity can be areas of fracturing. The variation of velocity tomography described in this thesis uses acoustic emissions as sources for the propagation wave. Acoustic emission sources provide advantages …
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Passive Tomography to Image Stress Redistribution Prior to Failure on Berea Sandstone and Marcellus Shale for Caprock Integrity
… sample were calculated to determine how well the stress redistribution within the sample could be mapped using the recorded data. For the main indenter tests two samples were tested, a piece of Berea Sandstone and a piece of Marcellus Shale. The secondary test was a transform shear test using …
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Defining Stress Changes Ahead of a Tunnel Face and Design of a Data Acquisition System
… is a non-invasive technique to map the stress changes induced by mining ahead of the active face. Seismic tomography maps the velocity distributions of elastic waves traveling through a rock mass. The velocity distributions mapped in the tomograms can relate to anomalies in the rock such …
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Numerical analyses of the long term behavior of enhanced geothermal system (EGS)
… is to gain a better understanding of thermal stresses generated during the heat recovery process as a result of induced cooling of rocks and interaction of thermal stresses with existing lithologic stresses. The long term behavior of the EGS is assessed in terms of stress redistribution and …
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Study of the Effect of Interface Slip and Diffusion Mechanisms on the Creep of Metal and Intermetallic Matrix Composites
… influence of the two mechanisms on the transient stress redistribution between the composite constituents is investigated. For a composite whose matrix-reinforcement interface is either perfectly bonded, freely slipping, or rapidly diffusive, the transient solution scales with the applied load and …
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Imaging of Stress in Rock Samples using Numerical Modeling and Laboratory Tomography
… Many of these incidents take place due to stress redistribution resulting from mine workings. Thus it is very important to develop some tools to predict this failure in advance and prevent any fatalities arising from the failure. The current study uses two tools — numerical modeling and …
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Applications of Double-Difference Tomography for a Deep Hard Rock Mine
… the rock mass that can be used to infer relative stress of the rock mass. The data set used for the double-difference tomography inversion was from Creighton Mine in Sudbury, Ontario, Canada, and consisted of two months of data averaging 150 microseismic events per day. Three separate studies were …
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Microseismic Monitoring of a Room and Pillar Retreat Coal Mine in Southwest Virginia
… to provide more information about the changing stress conditions created by retreating and ultimately reduce risk to miners. Microseismicity has been proven to be an acceptable method of monitoring stress redistribution in underground coal mines and assist in explaining rockmass behavior …
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Nonlinear finite element analysis of tubular joints
… of tubular joints. The results include the stress redistribution within the joint at the ultimate state, the stiffness of the T-type joints at different load levels, the real failure modes of tubular joints under external loads and the assessment of the safety margins in the design process.
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Design and Testing of a Laboratory Ultrasonic Data Acquisition System for Tomography
… tomography allows for the measurement of stress-induced density changes inside of a rock mass or sample by non-invasive means. Tomography is a non-destructive testing method by which sensors are placed around a sample and energy is introduced into the sample at one sensor while the other …
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Static and Seismic Stability of Cut Slopes in Terms of Reliability
… failure as the critical failure mode. The stress condition along a potential failure surface both prior to and after an excavation is investigated by finite-element elasto-plastic analysis; in this process, a potential failure surface is modeled as joint elements. Through the investigation, …
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Fatigue behavior of notched carbon epoxy laminates during reversed cyclic loads
The relationships between fatigue damage, stress redistribution, and residual stiffness and strength were investigated for notched graphite epoxy laminates during fulIy-reversed cyclic loads. Two material systems, AS4/3501-6 and AS4/1808, two lamination arrangements, (0,45,90,-45)<sub>s</sub>₄ and …
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Micromechanics-Based Strength and Lifetime Prediction of Polymer Composites
… and theoretical understanding of micromechanical stress redistribution due to fiber fractures in unidirectional composite materials. In-situ measurements of fiber stress redistribution are made in macromodel composites where the fibers are large enough that strain gages can be mounted directly …
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Analysis of Composite Laminates with Matrix Cracks
… as a function of crack density and the axial stress redistribution due to the existence of matrix cracks. Both transverse cracks (2-D problem) and cross (transverse and longitudinal) cracks (3-D problem) are studied. Results for graphite/epoxy cross-ply laminates are presented and compared to …
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Impact of Stress-field Changes Induced by Hydraulic Fracturing on Subsurface Fault Stability
… fracturing formations can change in-situ stresses in the surrounding areas. There are concerns that hydraulic fracturing may potentially reactivate the subsurface faults nearby the treatment wells. The reactivated faults could cause many problems, such as early aborting/failure of …
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Micromechanics of finite length fibers in composite materials
… model is derived to study the point-wise stress variations which occur in the constituents of a hybrid 3-D short fiber composite subjected to arbitrary homogeneous loading conditions. The model includes the capability to analyze composites containing different types of fibers, different …
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Micromechanical Aspects of Aging in Granular Soils
… due to microbiological activity, internal stress redistribution caused by particle crushing, and buckling of the load chains due to particle slippage. New evidence points out that internal and time-dependent changes in the soil structure caused by particle slippage and rearrangement as the …
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A Numerical Based Determination of Stress Intensity Factors for Partially Cracked Flexural I-shaped Cross-sections
… bridge girders have been observed as a result of stress concentrations, design errors, welding quality control, and vehicular impacts. Cracks can grow in size with time and active cyclic live loads and may result in a member fracture. Fracture is a dangerous limit state which occurs with little to …
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Tailored Mechanical Response of 3D Microgranular Crystals with Hierarchical Architecture
… fully dense counterparts and unique nonlocal stress redistribution, surpassing classical granular mechanics through architectural design. This work establishes a path toward lightweight, tunable, and impact-resistant metamaterials, with broad applications in nonlinear waveguiding, energy …
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Automated Design of Reinforced Concrete Deep Beams
… concrete structures under a state of generalised stress, and also for their ease of manufacture and testing. The rationale for the method was that the steel bars carrying the loads once the concrete is cracked should be strained as close as possible to the steel s yield strain. It was found that, …
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