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 94 for “"microcracks"”.
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Microdamage accumulation in bovine trabecular bone
… failure point, it develops damage in the form of microcracks. Normally, microcracks are repaired by the remodeling process, limiting the number of in vivo microcracks. However, if the rate of microdamage accumulation increases or the rate of remodeling slows, microdamage can accumulate, reducing …
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Effects of Extreme Low Temperature on Composite Materials
… and finding the rate of generation of microcracks in composites at cryogenic temperatures by acoustic emission technique. Microcracks increase the permeability of composites. So to study the permeability growth with microcracks, equipment is also designed to measure the permeability of …
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Shear Fracture Growth in Granular Rocks and Porosity-Permeability Relationships in Mudstones
… shear fractures through interaction of emergent microcracks occurring in shear and tensile modes. I document the mode and energy associated with microcracks to analyze fracture growth patterns and quantify energy release. Shear fracture growth in my sandstone model occurs through cooperative …
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Entwicklung mechanischer Modelle zur analytischen Beschreibung der Materialeigenschaften von textilbewehrtem Feinbeton
… orientated reinforcements in an averaged sense. Microcracks are included by additional strains in the representative volume element. The average interaction between the microcracks and the reinforcements is considered by an effective field approximation. As a criteria for the initiation of the …
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Deformation in the striped rock pluton, southwest Virginia
… least two generations of mineralized, dilatant microcracks. Minerals precipitated in the early set of microcracks have undergone extensive crystal plastic deformation. Late-stage microcracks are filled with completely undeformed minerals. The spatial distribution of normal fault mylonite zones …
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Thermomechanical property evaluation of molybdenum alloys
… alloy with 6% wt of spinel (MgAl2O4) develops microcracks which are related to the number of cycles. The microcracks are caused by the thermal expansion mismatch between the spinel particles and molybdenum matrix, as well as the processing conditions. After the tests, the specimen was polished …
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Post sheer stress flow of flowable composites containing microcapsules
… occur as a result of the composite developing microcracks after a filling. Microcracks are often due to stress from shrinkage during polymerization. Additionally, the replacement of bis-GMA with UDMA was studied due to the effort to replace BPA in dental materials. Additionally, these …
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Environmental effects on stitched RTM composites
… and a percent at the low temperature. Microcracks which were found predominantly around individual stitches were recorded using photomicrographs taken at the end of each cycling period. The glass stitched and Kevlar stitched laminates showed significant microcracking before cycling. The …
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Transverse microcracking in Celion 6000 graphite/PMR-15 polyimide composite
… loadings upon the development of transverse microcracks (TVM) in Celion 6000/PMR-15 graphite-epoxy laminates were investigated. Microcracks were observed using a replicating technique, microscopy and x-ray. The mechanical or thermal load at which microcracking initiates and the ply residual …
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Wear Mechanism/microstructure Relationships for Laser Processed Cast Iron (Erosion, Abrasion, Martensite, Transformation)
… in this area causes the initiation of microcracks. Further propagation of these microcracks with continued deformation is believed to be the origin of wear particle generation.
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Computer simulation of the osteocyte and bone lining cell network and the effect of normal physiological changes in cellular functions on that network
… factor. The effect of osteocyte apoptosis and microcracks are then examined by preventing signalling at and through the affected cells. It is found that a small percentage of apoptotic cells and tiny microcracks both lead to a significant reduction in the peak signal at the BLCs. The simulation …
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Self-sealing of thermal fatigue and mechanical damage in fiber-reinforced composite materials
… of these vessels leads to the formation of microcracks, which allow gas phase leakage across the tank walls. In this dissertation, self-healing functionality is imparted to a structural composite to effectively seal microcracks induced by both mechanical and thermal loading cycles. Two …
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Fracture of Hot-Pressed Silicon Nitride at Elevated Temperatures
… boundary separation results in the formation of microcracks in the vicinity of the main crack. The main crack then advances slowly by joining up with these nearby microcracks. Cavities and regions of grain boundary deformation were observed with SEM and TEM. A map was drawn of displacement rate …
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Grinding of cement clinkers : linking multi-scale fracture properties to system chemistry, mineralogy and microstructure
… (crack deflection, crack tip shielding by microcracks, crack trapping, and crack pinning) explained this behavior. Comparison of industrial clinkers showed that higher macroscale toughness (i.e., poor coarse grindability) was associated with oversized alite crystals, which was explained by …
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In-plane vibration of a plate having an elliptical hole of arbitrary eccentricity
… of the hole are theoretically capable of causing microcracks which have been observed experimentally. Several approaches were used including reduction of the mixed boundary value problem to a Fredholm equation, and to a matrix eigenvalue problem. Contour curves of various stresses and …
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Nondestructive photoelastic characterization of monocrystalline silicon photovoltaic wafers
… of residual stress and external loads acting on microcracks in the saw damage layer. This research presents a novel method for characterizing monocrystalline silicon wafers using a photoelastic imaging technique that is capable of measuring the bulk residual stress fields in silicon wafers as …
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Geophysical characterization of the effects of fractures and stress on subsurface reservoirs
… into two parts: larger scale fractures and microcracks. In the first part, we study the sensitivity of seismic waves and their time-lapse changes in hydraulic fracturing to the geometrical and mechanical properties of fractures that have dimensions comparable to the seismic wavelength. …
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The Effect of Long-Term Thermal Cycling on the Microcracking Behavior and Dimensional Stability of Composite Materials
… For some specimens in this study, the number of microcracks in thin-layer specimens exceeds that in thick-layer specimens by more than a factor of two. Despite the higher number of microcracks in the thin-layer specimens, small changes in CTE after thousands of cycles indicate that the thin-layer …
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A Parametric Study on the Effects of External Stimuli on the Aqueous Dissolution of Lithium Disilicate Glass
… introduced during grinding (scratch lines and microcracks) were preferentially leached and grew in size and number visible during dissolution. A semi-quantitative model was created using stereoscopic reconstruction to describe the preferential leaching of the microcracks as there was little …
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Role of cracks in creep of brittle, polycrystalline, structural ceramics
… sigmoidal region resulting from growth of microcracks along grain boundary facets, a tertiary or crack-enhanced stage associated with arrested microcracks, and a quarternary stage comprising crack linkage and coalescence. It was demonstrated that the formation and growth of cracks during …
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