Browsing by Subject "Deformation"
Now showing 1 - 20 of 25
- Results Per Page
- Sort Options
Item A generalized model to estimate the elastic stiffness tensor of mudrocks based on the full strain tensor(2021-05-07) Wiggs, David McLean; Flemings, Peter Barry, 1960-I develop a three-step framework to model the anisotropic elastic properties of a mechanically compacted mudrock based on the full strain tensor. I model the microstructure as an effective medium representative of locally aligned domains of clay grains and fluid filled porosity with isolated quartz. Then I predict the orientation of these building blocks due to the application of any strain field. Finally, the previous two steps are combined to determine an effective medium model for the entire mudrock that predicts the elastic stiffness matrix. I focus on the relationship of deformation to porosity reduction and grain alignment in mudrocks. My results show that the application of axial loading leads to the development of elastic anisotropy with stiffnesses increasing more rapidly in the direction perpendicular to loading. These stiffness predictions closely match experimental data on a mudrock specimen from Eugene Island – Gulf of Mexico. I further apply my three-step framework to predict elastic stiffnesses in a synthetic salt basin based on the full strain tensor predicted by an evolutionary poromechanical model. This coupling allows us to predict elastic stiffnesses and anisotropy due to sediment deposition and non-uniaxial salt loading. Accurate estimation of elastic stiffnesses for mudrocks based on the full strain tensor holds immense potential to improve pressure prediction, seismic imaging in complex geologic environments, and prospect evaluationItem Analysis of the effects of carbonate mounds on associated stratal geometry and fracture development, Sacramento Mountains, New Mexico, USA(2016-12) Tinker, Nathan Scott; Janson, Xavier; Zahm, Christopher Kent; Kerans, Charles; Fisher, William LThe objective of this research is an integrated structural‐stratigraphic analysis of compaction‐related fracturing in carbonate mounds and associated cover strata. The influence of early-cemented carbonate mounds on subsequent sediment deposition (such as creation of hard substrates and topographic relief) is relatively well-understood. The effect of early-cemented carbonate mounds during burial, however, has not been studied in detail. Early marine cementation of mounds enhances mechanical rigidity, which reduces mound compaction during burial as compared to less-resistant sediments surrounding and overlying the mound. This rigidity difference facilitates differential compaction of sediments overlying the mound, which are warped over the inflection point created by the mound topography. This study hypothesizes that there is a measurable increase in fracture intensity associated with differential compaction above early-lithified carbonate mounds. Thus, this work analyzes and quantifies the effects of differential compaction on stratal geometry, mechanical stratigraphy, and fracture development in Mississippian strata overlying carbonate mounds which are well-exposed in the Sacramento Mountains in southeast New Mexico. Methods employed in this study are drawn from structural geology, sedimentology, petrography, and remote sensing in an effort to adequately determine facies, examine fracture characteristics (e.g. size, orientation, and intensity), and to better understand which process(es) most directly control those characteristics (e.g. host rock facies type, diagenesis, bed thickness, mound proximity, mound size). Innovative methods of outcrop characterization such as high-resolution gigapan photography and unmanned aerial vehicle (UAV) photography were combined with photogrammetric techniques to create photo-realistic 3D outcrop models. The resulting models enabled a cost-effective, more detailed, less-distorted, and more comprehensive interpretation compared to previous methods, and improved understanding of the relationship between stratigraphy, rock mechanical evolution, and structural deformation in carbonate mound systems. Field work documented facies, stratal geometries, folds, faults, and fracture sets which validated observations and characterizations made using high-resolution field photographs and 3D outcrop models. Results of this work show that paleotopographic relief which has been early lithified (in this instance, Mississippian carbonate mounds) directly controls fracture development and overlying stratal geometry, in that there is a significant increase in tension fracture (mode 1) intensity above pre-existing rigid structures and over-steepening of bed dips beyond an expected and reasonable angle of repose. Additionally, this work outlines a multi-stage tectonostratigraphic sequence of the development of the stratigraphically complex Teepee Mound assemblage based on field observations of facies, fractures, stratal geometries, and diagenetic effects (e.g. cementation, compaction, and chertification), which includes new evidence of late-Mississippian tectonic compression. This result emphasizes the importance of understanding both syndepositional and post-depositional processes in outcrop characterization. Specifically, syndepositional processes establish the original mechanical stratigraphy and control the formation and propagation of early mechanical discontinuities, which in turn set up the fabric of weaknesses preferentially utilized by later fracture development. Post-depositional mechanical and diagenetic processes alter mechanical stratigraphy and rock brittleness, and thus influence fracture propagation through time.Item CM Murchison : nebular formation of fine-grained chondrule rims followed by impact processing on the CM parent body(2017-01-06) Hanna, Romy Darlene; Ketcham, Richard Alan, 1965-; Zolensky, Mike E; Hamilton, Victoria E; Holt, Jack W; Lassiter, John CWe examine the primitive carbonaceous chondrite, CM Murchison, to infer details concerning its formation and subsequent processing on the CM parent body. We use X-ray computed tomography (XCT) to measure the 3D morphology and spatial relationship of fine-grained rims (FGRs) of Type I chondrules and find that the relationship between FGR volume and interior core radius is well described by a power law function as proposed for FGR accretion in a turbulent nebula by Cuzzi (2004). We also find evidence that the rimmed chondrules were slightly larger than Kolmogorov-stopping-time nebular particles. Evidence against parent body FGR formation includes a positive correlation between rim thickness and chondrule size and no correlation between interior chondrule roughness (used as a proxy for degree of aqueous alteration) and FGR volume. We find that the chondrules are foliated and that the FGRs are compressed in the direction of maximum stress, resulting in rims that are consistently thicker in the plane of foliation. After accretion to the CM parent body, the material within Murchison experienced brittle deformation, porosity loss, and aqueous alteration. XCT reveals that partially altered chondrules define a prominent foliation and weak lineation. The presence of a lineation and evidence for a component of rotational, noncoaxial shear suggest that the deformation was caused by impact. Olivine optical extinction indicates that the sample is classified as shock stage S1 and electron microscopy reveals that plastic deformation was minimal and that brittle deformation was the dominant microstructural strain-accommodating mechanism. Evidence such as serpentine veins parallel to the foliation fabric and crosscutting alteration veins strongly suggest that some aqueous alteration post-dated or was contemporaneous with the deformation and that multiple episodes of fracturing and mineralization occurred. Finally, using the deformed shape of the chondrules we estimate the strain and infer that the original bulk porosity of Murchison before deformation was 32.2 – 53.4%. Our findings suggest that significant porosity loss, deformation, and compaction from impact can occur on chondrite parent bodies whose samples record only a low level of shock, and that significant chondrule deformation can result from brittle processes and does not require plastic deformation of grains.Item Compression and permeability behavior of natural mudstones(2011-12) Schneider, Julia, 1981-; Flemings, Peter Barry, 1960-; Mohrig, David; Cardenas, Meinhard B.; Day-Stirrat, Ruarri J.; Germaine, John T.Mudstones compose nearly 70% of the volume of sedimentary basins, yet they are among the least studied of sedimentary rocks. Their low permeability and high compressibility contribute to overpressure around the world. Despite their fundamental importance in geologic processes and as seals for anthropogenic-related storage, a systematic, process-based understanding of the interactions between porosity, compressibility, permeability, and pore-size distribution in mudstones remains elusive. I use sediment mixtures composed of varying proportions of natural mudstone such as Boston Blue Clay or Nankai mudstone and silt-sized silica to study the effect of composition on permeability and compressibility during burial. First, to recreate natural conditions yet remove variability and soil disturbance, I resediment all mixtures in the laboratory to a total stress of 100 kPa. Second, in order to describe the systematic variation in permeability and compressibility with clay fraction, I uniaxially consolidate the resedimented samples to an effective stress equivalent to about 2 km of burial under hydrostatic conditions. Scanning electron microscope images provide insights on microstructure. My experiments illuminate the controls on mudstone permeability and compressibility. At a given porosity, vertical permeability increases by an order of magnitude for clay contents ranging from 59% to 34% by mass whereas compressibility reduces by half at a given vertical effective stress. I show that the pore structure can be described by a dual-porosity system, where one rock fraction is dominated by silt where large pores are present and the majority of flow occurs and the other fraction is dominated by clay where limited flow occurs. I use this concept to develop a coupled compressibility-permeability model in order to predict porosity, permeability, compressibility, and coefficient of consolidation. These results have fundamental implications for a range of problems in mudstones. They can be applied to carbon sequestration, hydrocarbon trapping, basin modeling, overpressure distribution and geometry as well as morphology of thrust belts, and an understanding of gas-shale behavior.Item The construction and use of physics-based plasticity models and forming-limit diagrams to predict elevated temperature forming of three magnesium alloy sheet materials(2013-08) Antoniswamy, Aravindha Raja; Taleff, Eric M.Magnesium (Mg) alloy sheets possess several key properties that make them attractive as lightweight replacements for heavier ferrous and non-ferrous alloy sheets. However, Mg alloys need to be formed at elevated temperatures to overcome their limited room-temperature formabilities. For example, commercial forming is presently conducted at 450°C. Deformation behavior of the most commonly used wrought Mg alloy, AZ31B-H24, and two potentially competitive materials, AZ31B-HR and ZEK100 alloy sheets, with weaker crystallographic textures, are studied in uniaxial tension at 450°C and lower temperatures. The underlying physics of deformation including the operating deformation mechanisms, grain growth, normal and planar anisotropy, and strain hardening are used to construct material constitutive models capable of predicting forming for all three Mg alloy sheets at 450°C and 350°C. The material models constructed are implemented in finite-element-method (FEM) simulations and validated using biaxial bulge forming, an independent testing method. Forming limit diagrams are presented for the AZ31B-H24 and ZEK100 alloy sheets at temperatures from 450°C down to 250°C. The results suggest that forming processes at temperatures lower than 450°C are potentially viable for manufacturing complex Mg components.Item Construction and validation of a hot torsion testing instrument(2014-05) Weldon, Andrew James; Taleff, Eric M.The need to increase vehicle performance, particularly fuel efficiency, has led to an increased interest in using lightweight metals for vehicle structural components. Lightweight aluminum alloys offer the potential to significantly reduce vehicle mass when structural components that use steel are replaced. Mass reduction is a very efficient route to increase vehicle performance. In vehicles with traditional powertrains, mass reduction can increase fuel efficiency. In vehicles with electrical powertrains, mass reduction can increase driving range. Regardless of the specific structural application, the best performance of any aluminum alloy is only obtained by achieving a microstructure that produces the best material properties. For wrought aluminum alloys, hot and cold deformation steps are critical to obtaining a desirable microstructure prior to the forming of a final component. For sheet material, the first step in controlling the final microstructure is microstructure evolution during hot rolling the cast ingot material. Hot rolling precedes cold rolling of the sheet to final thickness in most commercial sheet manufacturing operations. Microstructure during hot rolling is difficult to study because it requires a combination of high temperatures, fast strain rates and large strains to do so. Furthermore, specimens for microstructural examination must be extracted from these conditions while retaining the characteristics of the specific conditions that are to be studied. Hot torsion testing is the traditional approach to meeting these experimental requirements. In this investigation, a new hot torsion testing instrument is designed, fabricated and validated to enable future experiments that will elucidate microstructure evolution under conditions pertinent to hot rolling. This new instrument is integrated with computerized control and data acquisition systems. Validation experiments were conducted to characterize its capabilities. It is concluded that the completed instrument meets the requirements necessary to study plastic deformation and microstructure evolution in aluminum alloys under conditions relevant to hot rolling.Item Defects and deformation in nanostructured metals(2009-12) Carlton, Christopher Earl; Ferreira, Paulo J. (Paulo Jorge)A better understanding of how the nanoscale environment affects the mechanical properties of materials, in particular metallic nanoparticles and nanocrystalline metals is vital to the development of next generation materials. Of special interest is obtaining a fundamental understanding of the inverse Hall-Petch Effect in nanocrystalline metals, and nanoindentation in individual nanoparticles. Understanding these subjects is critical to understanding how the mechanical properties of materials are fundamentally affected by nanoscale dimensions. These topics have been addressed by a combination of theoretical modeling and in-situ nanoindentation transmission electron microscopy (TEM) analysis. Specifically, the study of the inverse Hall-Petch effect in nanocrystalline metals will be investigated by a thorough review of the literature followed by a proposed novel theoretical model that better explains the experimentally observed behavior of nanocrystalline metals. On the other hand, the nanoindentation of individual nanoparticles is a very new research topic that has yet to aggregate a large body of experimental data. In this context, in-situ TEM nanoindentation experiments on silver nanoparticles will be first performed to determine the mechanisms of deformation in these nanostructures. A theoretical explanation for the observed deformation mechanisms will be then developed and its implications will be discussed. In addition to nanoparticles, this study will also provide unique and valuable insight into the deformation mechanisms of nanopillars, a growing area of research despite much controversy and speculation about their actual mechanisms of deformation. After studying the novel behavior of both nanocrystalline metals and nanoparticles, useful applications of both classes of materials will be explored. The discussion of applications will focus on utilizing the interesting behaviors explored in the dissertation. Of particular interest will be applications of nanoparticles and nanocrystalline materials to coatings, radiation resistance and super-plastic materials.Item Dune behavior in a multidirectional wind regime : White Sands Dune Field, New Mexico(2014-08) Pederson, Anine Oehlenschlaeger; Kocurek, GaryAs with most dune fields, the White Sands Dune Field in New Mexico forms in a wind regime that is not unimodal. In this study, dune behavior at White Sands was documented from a time series of five lidar-derived digital elevation models (DEM) and compared to a record of wind direction and speed during the same period. For the study period of June 2007 - June 2010, 244 sand-transporting wind events occurred and define a dominant wind mode from the SW and lesser modes from the NNW and SSE. Based upon difference maps and tracing of dune brinklines, overall dune behavior consists of migration to the NE, but with along-crest migration of dune sinuosity to the SE. Permutations of the DEMs allow matching specific dune behavior with wind modes. The SW winds are transverse to dune orientations and cause most forward migration. The NNW winds cause along-crest migration of dune sinuosity and low stoss bedforms, as well as SE migration of NE-trending dune terminations. The SSE winds cause ephemeral dune deformation, especially crestal slipface reversals. Dune deformation occurs because of unequal deposition along the lee face as a function of the incidence angle formed between the wind and the local brinkline orientation. Incidence-angle control on dune deformation and types of lee-face surface processes allows for an idealized model for White Sands dunes. The dunes behave as complex systems in which each wind event deforms the dune shape, this new shape then serves as the configuration for the next wind event.Item Effects of Aggregate Gradation and Angularity on VMA and Rutting Resistance(2001-06) Park, Dae-Wook; Chowdhury, Arif; Button, Joe W.The Superpave system adopted the voids in mineral aggregate (VMA) criteria developed by McLeod using the 75-blow Marshall compactor for conventional dense-graded hot mix asphalt (HMA) mixtures. This VMA criteria is a function of only the nominal size of aggregate regardless of shape, texture, or gradation. The Superpave volumetric mixture design process contains a required minimum value for fine aggregate angularity (FAA) as a function of traffic level and position of the layer within the pavement structure. This parameter is reported as the percentage of uncompacted air voids, with larger values generally indicating increased aggregate angularity and, thus, higher VMA and better resistance to permanent deformation. The purpose of this study was to evaluate the effects of FAA and gradation on the resulting VMA of certain HMA mixtures. The effect of FAA was evaluated using mixtures containing coarse limestone combined with six different fine aggregates. Mixtures with three gradations which pass through, above, and below the restricted zone; three different mineral filler contents; and four different values of FAA were analyzed to evaluate the effects of these parameters on VMA of Superpave mixtures. Based on analyses of these tests, mixtures containing fine granite or limestone showed less permanent deformation than mixtures containing fine river gravel or natural rounded sand. FAA values and permanent deformation did not correlate well. Gradations that pass through the restricted zone did not significantly affect mixture VMA. Mineral filler contents and FAA value did affect mixture VMA significantly. Higher FAA values yielded higher VMA.Item Field Validation of the Cross-Anisotropic Behavior of Unbound Aggregate Bases(2001-03) Tutumluer, Erol; Adu-Osei, Alex; Little, Dallas N.; Lytton, Robert L.The ICAR Research Project 502 has focused on determining structural considerations of unbound aggregate pavement layers for a proper representation in the new AASHTO Pavement Design Guide 2002. The research team developed models for the resilient and permanent deformation behavior from the results of triaxial tests conducted at the Texas Transportation Institute (TTI) and at the University of Illinois. The studies have mainly indicated that the unbound aggregate base (UAB) material should be modeled as nonlinear and cross-anisotropic to account for stress sensitivity and the significant differences between vertical and horizontal moduli and Poisson's ratios. UABs were constructed at the TTI Riverside research facility and tested for response and performance using the one-third scale model of the Texas Mobile Loading Simulator. The resilient responses of the test sections were modeled. The nonlinear cross-anisotropic material models used in the base layer predicted vertical deflections that are close to field deflections in the analyzed TTI pavements. Field validation data were also collected from a full-scale pavement test study conducted at Georgia Tech. The test sections had extensive instrumentation and the pavement response variables, such as stresses, strains, and deformations, were measured in all pavement layers including the UABs. The validation of the anisotropic modeling approach was accomplished by analyzing these test sections using GT-PAVE finite element program, predicting UAB responses, and comparing them to the measured ones. Laboratory testing of the aggregate samples was conducted at the University of Illinois and the characterization models were developed for the stress sensitive, cross-anisotropic aggregate behavior. With nonlinear anisotropic modeling of the UAB, the resilient behavior of pavement test sections was successfully predicted at the same time for a number of response variables. In addition, the stress sensitive, cross-anisotropic representation of the base was shown to greatly reduce the horizontal tension computed in the granular base when compared to a linear isotropic representation.Item Foreland basin evolution and exhumation along the deformation front of the Eastern Cordillera, northern Andes, Colombia(2010-08) Bande, Alejandro Ezequiel; Horton, Brian K., 1970-; Ketcham, Richard A.; Steel, Ronald J.Tracking the phases of Cenozoic deformation in the Eastern Cordillera of Colombia has proven to be a challenging task. Clear disagreements remain in interpretations of the timing of uplift of the Eastern Cordillera, possibly based on difficulties in distinguishing first-cycle Central Cordillera grains from recycled Eastern Cordillera clasts. This thesis focuses on the Eocene-Pliocene sedimentary record of the eastern foothills of the Eastern Cordillera at a latitude of 6°N, integrating basin analysis with several provenance techniques in order to date the activation of several thrust systems. Based on assessments of depositional environments and sediment dispersal patterns together with mineralogical and geochronological provenance, the onset of uplift in the axial zone of the Eastern Cordillera is constrained to be Oligocene. Prior to uplift, deposition in the eastern foothills was sourced from the eastern craton. Following the Oligocene episode, a continuous eastward advance of deformation is documented. An early Miocene episode probably reactivated the easternmost Cretaceous rift boundary along the eastern side of the Eastern Cordillera. Subsequent footwall shortcuts of those faults initiated activity in the middle to late Miocene, creating an intermontane (piggyback) basin in the eastern foothills at that time. In the preferred interpretation, this in-sequence history of thrust activation represents the main phases of deformation in the Eastern Cordillera from Eocene to Pliocene time, with neotectonic activity recording continued shortening.Item High-temperature carbonate replacement mineralization, metamorphism, deformation, and intrusion in the Bryant District, Beaverhead County, Montana(2003) McGuire, James B.; Kyle, J. RichardThe Bryant District, in the southwest Montana fold-and-thrust belt, contains many structurally and lithologically controlled high-temperature carbonate replacement Pb-Zn-Cu-Ag-Au deposits. Laramide crustal shortening prepared Cambrian and Devonian carbonate strata for fluid circulation through thrusting and folding. Thrust-controlled mineralization is present in the Lion Mountain mines, whereas fold-controlled chimney-style mineralization is present in the Cleve-Avon mines. Pb isotopic evidence indicates that base and precious metals in the district were not directly sourced from phases of the adjacent Late Cretaceous Pioneer Batholith. Ore Pb was probably scavenged from the Middle Proterozoic Belt Supergroup that underlies the district. A small pluton, satellitic to the Pioneer Batholith, underlies the Hecla Dome and may have set up a hydrothermal system which produced carbonate replacement as well as Mo skarn mineralization. Fluid inclusions in ore-associated quartz from the Bryant District are CO2-rich and have salinities from 3 to 8 wt% NaCl equivalent with homogenization temperatures from 260 to 330°C. Fluorine-deficient porphyry Mo deposits in Montana and Idaho, most notably Cannivan Gulch 5 km northwest of the Bryant District, have remarkably similar fluid inclusion characteristics, suggesting that the Bryant District carbonate replacement deposits may be the distal portion of a porphyry Mo system. The mineralization in the Bryant District appears to be related to a late satellitic intrusion of the Pioneer Batholith. Such an intrusion was hypothesized (Winchell, 1914; Karlstrom, 1948) and recently proven by exploratory drilling on the Hecla Dome. Field evidence suggests that Pb-Zn-Cu-Ag-Au mineralization took place after most Laramide shortening, intrusion of the bulk of the Pioneer Batholith, regional metamorphism, and contact metamorphism related to the emplacement of an intrusion below the Hecla DomeItem In situ melt generation in anatectic migmatites and the role of strain in preferentially inducing melting(2011-08) Levine, Jamie Sloan Fentiman, 1979-; Mosher, Sharon, 1951-; Carlson, William D.; Cloos, Mark; Daczko, Nathan; Siddoway, ChristineDeformation and partial melting have long been recognized to occur together, but differentiating which actually occurred first has remained enigmatic. Prevailing theories suggest that partial melting typically occurs first, and deformation is localized into melt-rich areas because they are rheologically weak. However, evidence from three different areas, suggests the role of strain has been underestimated in localizing partial melting. The Wet Mountains of central Colorado provide evidence for synchronous partial melting and deformation, with each process enhancing the other. Throughout the Wet Mountains, deformation is concentrated in areas where melt producing reactions occurred, and melt appears to be localized along deformation-related features. Melt microstructures present within the Wet Mountains correlate well with crustal-scale plutons and magmatic bodies and provide a proxy for crustal-scale melt flow. Granitic gneisses from the Llano Uplift, central Texas, provide evidence for partial melting occurring within small-scale shear zones and surrounding country rocks, synchronously. In the field, shear zones appear to contain former melt, whereas the country rock does not provide macroscopic evidence for partial melting. However, detailed microstructural investigation of shear zones and country rocks indicates the same density of melt microstructures, in both rock types. Melt microstructures are important for understanding the full melting history of a rock and without detailed structural and petrographic analysis, erroneous conclusions may be reached. Granulite-facies migmatites of the Albany-Fraser Orogen, southwestern Australia, have undergone partial melting, synchronous with three phases of bidirectional extension. Four major groups of leucosomes, including: foliation-parallel, cross-cutting, boudin neck and jumbled channelway leucosomes and late pegmatites were analyzed via whole-rock geochemistry, and there is evidence for fluid-saturated and -undersaturated biotite- and amphibole-dehydration melting. Migmatites from these three locations contain pseudomorphs of melt along subgrain and grain boundaries, areas of high dislocation density, in quartz and plagioclase. For these rocks that involve multicomponent systems, the primary cause for preferential melting in high strain locations is enhanced diffusion rates along the subgrain boundary because of pipe diffusion or water associated with dislocations.Item Interactions between turbidity currents, turbidites and topography generated by a mobile substrate(2016-12) Minton, Brandon Wade; Mohrig, David; Kim, Wonsuck; Buttles, JamesModels for development and filling of submarine minibasins remain incomplete for the following reasons: (1) they seldom account for growth of seafloor topography via subsurface salt motion that coincides with turbidite sedimentation; (2) they seldom account for interactions between turbidity currents and seafloor topography that influence subsequent sedimentation patterns; and (3) they seldom consider the degree to which the evolution of seafloor topography associated with any single minibasin is affected by its neighboring minibasins. These points have now been addressed through a novel set of laboratory experiments. In the suites of experiments, turbidity currents consisting of 1.5% sediment by volume were released onto a 1.2 m x 1.2 m x 0.05 m platform filled by a composite layer of PDMS polymer and pliable putty (Silly Putty™). Interactions between pre-existing bed topography and turbidity currents result in differential loading of the substrate and influence depositional patterns. These interactions are achieved through a combination of blocking and focusing of currents by topography and by remobilization and removal of deposits from steeply sloping surfaces. Spatially varying deposit thicknesses generate locations that exceed the threshold load and begin to deform the mobile substrate. Turbidites of insufficient thickness are simply “along for the ride” and do not contribute to substrate deformation. Additionally, the tendency of the far-field surface to uplift or subside is preconditioned by the topography of the initial surface. These findings represent contributions towards the goal of better defining the important transition from turbidite sedimentation on an unconfined slope to deposition in minibasins.Item Kinematic analysis of outcrop-scale structures, southern Big Sur segment of Highway 1, Monterey and San Luis Obispo Counties, California(2007) Trasko, Keith Patrick; Cloos, MarkThe Nacimiento Block is located in the Southern Coast Ranges of California, and consists mainly of Franciscan Complex accretionary prism rocks. It is cross-cut by the San Gregorio-Hosgri Fault Zone, a major right-lateral strand of the San Andreas Fault System. The Nacimiento Block is bounded on the east by the Nacimiento Fault, of debated timing and kinematics, which separates it from the Salinian Block. The Salinian Block is a piece of the Sierra Nevada Batholith, and both the Salinian and Nacimiento Blocks have been displaced from southern California by right-lateral slip on the San Andreas Fault System. To address the question of fault kinematics, a 48 kilometer long section of the Nacimiento Block was examined along California Highway 1 between Lopez Point and Ragged Point. Exposure occurs along approximately 20 kilometers of the transect, and landsliding obscures approximately half of the exposure. The remaining 10 kilometers of outcrop were mapped. Kinematic data were taken on 29 outcrops, totaling 542 minor faults, 406 with slickenlines and 258 with sense of slip indicators, along with 314 veins. Of the faults, 202 are dip-slip (60-90° rake), 113 are oblique-slip (31-59° rake), and only 91 are strike-slip (0-30° rake). The dominant mode of minor faulting is normal, with 111 faults observed, compared to 25 reverse, 24 left-lateral, and 28 right-lateral strike-slip. Two sets of vein and one set of dike orientations were measured. Stereographic analysis reveals the normal and reverse faults dip steeply to the southwest and strike northwest-southeast, subparallel to the coast and San Gregorio-Hosgri and Nacimiento Faults. There is no dominant orientation to the strike-slip faults. Faults of all types cut 17 slab-window related andesitic dikes, which are likely Early Miocene in age according to apatite and zircon fission track ages. The character of all fault planes is similar, indicating they are coeval. Three stages of deformation are recognized. Subduction generated mélange, the dominant lithology in this area, and "broken formations". A second stage of deformation is recorded in the emplacement of dikes and one set of veins. A third stage of deformation is recorded in the minor planar faults that were measured in this study. It is proposed that this latest phase of deformation is caused by the gravitational collapse of the western edge of the Santa Lucia Range. The normal faults parallel the coastline and local slope angles are up to 40°. Coeval strike-slip associated with the San Gregorio-Hosgri Fault Zone is superimposed on this deformation. Apatite fission track ages (n=3) indicate that the dikes mapped along Highway 1 cooled to 110°C at approximately 11 Ma. This indicates an unroofing rate on the order of 300 m/my. This anomalously fast unroofing is accomplished by side-inwards gravitational collapse and erosionItem Measuring liquefaction-induced deformation from optical satellite imagery(2014-05) Martin, Jonathan Grant; Rathje, Ellen M.Liquefaction-induced deformations associated with lateral spreading represent a significant hazard that can cause substantial damage during earthquakes. The ability to accurately predict lateral-spreading displacement is hampered by a lack of field data from previous earthquakes. Remote sensing via optical image correlation can fill this gap and provide data regarding liquefaction-induced lateral spreading displacements. In this thesis, deformations from three earthquakes (2010 Darfield, February 2011 Christchurch, and 2011 Tohoku Earthquakes) are measured using optical image correlation applied to 0.5-m resolution satellite imagery. The resulting deformations from optical image correlation are compared to the geologic conditions, as well as field observations and measurements of liquefaction. Measurements from optical image correlation are found to have a precision within 0.40 m in all three cases, and results agree well with field measurements.Item Nanoindentation study of buckling and friction of silicon nanolines(2009-05) Luo, Zhiquan; Ho, P. S.Silicon-based nanostructures are essential building blocks for nanoelectronic devices and nano-electromechanical systems (NEMS). As the silicon device size continues to scale down, the surface to volume ratio becomes larger, rendering the properties of surfaces and interfaces more important for improving the properties of the nano-devices and systems. One of those properties is the friction, which is important in controlling the functionality and reliability of the nano-device and systems. The goal of this dissertation is to investigate the deformation and friction behaviors of single crystalline silicon nanolines (SiNLs) using nanoindentation techniques. Following an introduction and a summary of the theoretical background of contact friction in Chapters 1 and 2, the results of this thesis are presented in three chapters. In Chapter 3, the fabrication of the silicon nanolines is described. The fabrication method yielded high-quality single-crystals with line width ranging from 30nm to 90nm and height to width aspect ratio ranging from 10 to 25. These SiNL structures have properties and dimensions well suited for the study of the mechanical and friction behaviors at the nanoscale. In Chapter 4, we describe the study of the mechanical properties of SiNLs using the nanoindentation method. The loading-displacement curves show that the critical load to induce the buckling of the SiNLs can be correlated to the contact friction and geometry of SiNLs. A map was built as a guideline to describe the selection of buckling modes. The map was divided into three regions where different regions correlate to different buckling modes including Mode I, Mode II and slidingbending of SiNLs. In Chapter 5, we describe the study of the contact friction of the SiNL structures. The friction coefficient at the contact was extracted from the loaddisplacement curves. Subsequently, the frictional shear stress was evaluated. In addition, the effect of the interface between the indenter and SiNLs was investigated using SiNLs with surfaces coated by a thin silicon dioxide or chromium film. The material of the interface was found to influence significantly the contact friction and its behavior. Cyclic loading-unloading experiments showed the friction coefficient dramatically changed after only a few loading cycles, indicating the contact history is important in controlling the friction behaviors of SiNLs at nanoscales. This thesis is concluded with a summary of the results and proposed future studies.Item On the response of rubbers at high strain rates(2009-12) Niemczura, Johnathan Greenberg; Ravi-Chandar, K.The purpose of this study is to examine the propagation of waves of finite deformation in rubbers through experiments and analysis. First, attention is focused on the propagation of one-dimensional dispersive waves in strips of latex and nitrile rubber. Tensile wave propagation experiments were conducted at high strain-rates by holding one end fixed and displacing the other end at a constant velocity. A high-speed video camera was used to monitor the motion and to determine the evolution of strain and particle velocity in rubber strips. Analysis of the response through the theory of finite wave propagation indicated a need for an appropriate constitutive model for rubber; by quantitative matching between the experimental observations and analytical predictions, an appropriate instantaneous elastic response for the rubbers was obtained. This matching process suggested that a simple power-law constitutive model was capable of representing the high strain-rate response for both rubbers used. Next, the propagation of one-dimensional shock waves in strips of latex and nitrile rubber is examined. Shock waves have been generated under tensile impact in pre-stretched rubber strips; analysis of the response yields the tensile shock adiabat for rubbers. The propagation of shocks is analyzed by developing an analogy with the theory of detonation. Attention is then focused on the propagation of unloading waves of finite deformation in a rubber specimen analytically and experimentally. A rubber strip stretched to many times its initial length is released at one end and the resulting unloading is examined. Dispersive waves as well as shock waves are observed in these experiments. Quantitative discrepancies between the analytical model and experimental observations are again used to motivate a power-law model. Hysteresis in the response is attributed to strain-induced crystallization and melting phase transitions in natural latex rubber, and to nonequilibrium microstructural deformation in nitrile rubber. Finally, a Kolsky experiment is conducted and analyzed under the framework of dispersive loading and unloading waves utilized in the previous experiments. In this experiment, a phase boundary is introduced separating low and high strain phases of the rubber and is demonstrated to persist as a stationary boundary in latex rubber.Item Pliocene-Quaternary deformation and magmatism at the southern margin of the Puna plateau, Argentine Andes(2005) Baldwin, Austin Kyle; Marrett, RandallNew fault data and mapping of volcanic rocks from northwestern Argentina's Cordillera de San Buenaventura, a Pliocene-Quaternary, E-W trending volcanic range at the southern margin of the Puna plateau adjacent to the modern volcanic arc at 27°S, reveal numerous tectonomagmatic characteristics unique in the region. Faults in the Cordillera de San Buenaventura dominantly strike ENE-WSW, with lengths reaching at least 30-40 km. Fault motion, where measurable, has been normal, commonly with a right-lateral component. Some faults displace alluvium and dated Plio-Quaternary non-explosive lava domes and flows, intermediate in composition, with throws of 1-100 m, whereas other faults do not affect overlying volcanics. Previous studies in the surrounding southern Puna have reported Pliocene-Quaternary NNW-SSE extension along N-S to NNE-SSW striking right-slip faults commonly associated with volumetrically-minor mafic monogenetic cinder cones and flows. Explosive eruptions with intermediate compositions have also characterized the southern Puna during the Pliocene-Quaternary. Volcanics erupted during this time period in the Cordillera de San Buenaventura lack both mafic and explosive tendencies. The new data, combined with existing data, suggest that the Cordillera de San Buenaventura overlies a shallow magma chamber, which thermally weakened the upper crust and promoted the growth of the observed ENE-WSW striking normal and oblique-slip faults during the Pliocene-Quaternary. The new faults created right-stepping extensional transfers by linking preexisting NNE-SSW striking right-slip faults. Decreased horizontal stress at these transfers facilitated magma ascent from the underlying chamber. Periodic breaches of the magma chamber cupola by slip on faults prevented magmatic fluid accumulation and explosive eruptions. Mafic magma ascending beneath the Cordillera de San Buenaventura pooled in the shallow magma chamber, where it assimilated silica-rich crustal material and differentiated, eventually reaching the surface with an intermediate composition. In surrounding areas, where no shallow magma chamber existed, rising magmas reached the surface with mafic compositions. The high topography of the Cordillera de San Buenaventura may be the combined effect of mechanical doming by the shallow magma chamber, thermal uplift, isostatic elevation of an extensional transfer block, and local accumulation of Plio-Quaternary volcanicsItem Predicting deformation mechanisms during high speed impact of Ag nanoparticles(2020-03-27) Chitrakar, Tushar Vijay; Kovar, Desiderio; Becker, Michael F.; Keto, John W; Taleff, Eric MA number of aerosol deposition methods are currently used to produce thick films by impacting particles onto a substrate at high velocities. Though these processes operate at a similar range of velocities, there are significant differences in the sizes of the particles used in the aerosol. Conventional aerosol deposition methods deposit 0.1–40 μm sized-particles, whereas the laser ablation of microparticle aerosol process uses very fine 2–40 nm nanoparticles (NPs) to produce thick films. For particles smaller than 0.1 μm, deformation mechanisms that occur upon impact have not been studied previously in a systematic manner. In this dissertation, molecular dynamic simulations are used to study the time-evolution of deformation mechanisms that occur at very small timescales and high strain rates during high speed impact of Ag NPs. The defect evolution and the underlying mechanisms for deformation are systematically studied and documented by varying the NP size, the NP impact velocity, and the NP crystallographic orientation relative to the substrate. A wide range of microstructures ranging from polycrystalline to epitaxial morphologies are observed for these simulations. Because epitaxial deposition by particle impact has not been experimentally obtained, considerable attention is given to understanding the factors that are predicted to lead to epitaxy. Disordering is an important mechanism because it can play a role in epitaxial growth at high deposition velocities. A critical parameter is proposed to predict disordering that occurs upon impact. An alternative method to obtain epitaxial deposition at lower deposition velocities is also explored. The goal of this dissertation is to develop a thorough understanding of the available processing parameters for controlling the microstructure for a single NP deposition event. The impact studies in this dissertation provide fundamental guidelines needed to ultimately understand the formation of thick films where thousands of particles are impacted to produce a film.