Browsing by Subject "pressure"

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    Impact Force and Stress Distribution of Drop Impact
    (2021-08) Sun, Ting-Pi
    Drop impact is ubiquitous and relevant to many important natural phenomena and industrial applications. Although the kinematics of drop impact has been extensively studied through simulations and high-speed imaging, the understanding of drop impact is still far from fully understood. The studies of dynamics such as the impact force and the stress distribution of drop impact are still relatively scarce. The impact force and the stress distribution lead to the most important consequence throughout the industrial processes and are crucial factors to erosion on substrates or waterjet cutting. Here, we systematically investigate the impact force and the stress distribution of drop impact through experimental studies. To measure the impact force of drop impact, we synchronize the high-speed camera and the piezoelectric force sensor to obtain the temporal evolution of the impact force and the morphology of drop impact over several orders of magnitudes of Re. We verify the force-time scaling proposed by the self-similar theory at the high $Re$ regime. In the finite Re regime, we consider the effects from the viscosity of liquids and analyze the scaling by using a perturbation method, which matches our experimental results very well. The influence of viscoelasticity is also discussed. To obtain the temporal evolution of the stress distribution, which has not been measured experimentally, we develop a novel technique "high-speed stress microscopy." We confirm the propagation of the self-similar non-central maximum pressure and shear stress predicted by theories, and the shear force is also quantified. Moreover, we discover the impact-induced surface shock waves, which are crucial to the origin of erosion induced by drop impact. Furthermore, we measure the shear stress distribution of drop impact on micropatterned surfaces with high-speed stress microscopy. We investigate the influence of micropillars on substrates to the displacement distribution, the shear stress distribution, and the shear force. We hypothesize that the change of shear stress distribution may result from the formation of vortices. Finally, the results show that on the micropatterned surface, the maximum shear stress is suppressed, which is helpful for mitigating erosion to substrates. Our studies provide the experimental results for understanding the dynamics of drop impact. In addition to the pioneering works of measuring the stress distribution, high-speed stress microscopy can be applied to complicated conditions such as non-Newtonian drop impact and varying the ambient pressure. Besides, it opens the door for experimental exploration of the detailed information inside an impacting drop, including the patterns of the flow and the boundary layer.
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    Records of Metamorphism and Deformation at Maximum Depth in Gneiss Domes
    (2022-08) Hamelin, Clementine
    In exhumed orogens, much of the accessible material is quartzofeldspathic and records conditions of late-stage emplacement in the shallow crust at the high-temperature, low-pressure (HT-LP) conditions at which they equilibrated. Orogenic material may, however, be more deeply sourced than indicated by the recorded conditions of felsic rocks. To understand the magnitude of transport of heat and mass taking place during orogenic cycles, it is important to determine the depths from which material is sourced, and how this material is mobilized within the crust via lateral channelized flow and vertical flow that results in exhumation of former deep crust in gneiss dome structures. Mafic rocks are chemically and structurally refractory. As such, they have greater potential to preserve a record of petrogenesis and metamorphism at or near the maximum depth (peak-P) of metamorphism. Many gneiss domes contain mafic rocks as layers and lenses within the dominant felsic materials; e.g., the Montagne Noire (French Massif Central) and the Entia (central Australia) gneiss domes. In the Montagne Noire, scarce eclogites formed at HP conditions record metamorphic processes that occurred at or near the maximum-depth (peak-P) of metamorphism during lateral crustal flow. In the Entia, mafic granulites and amphibolites (± garnet) record progressive deformation and metamorphism primarily during exhumation. Geochemically and texturally distinct eclogites from the core and margin of the Montagne Noire dome retain geochemical and temporal records of deep-crustal processes. Results of in situ zircon and rutile U-Pb petrochronology show that both eclogites formed in the deep crust at HP (> 15 kbar, ~ 50 km) in association with doming at c. 320–310 Ma but had different protoliths and source regions within a pre-orogenic Cambro-Ordovician continental crustal package. In situ O-isotope analyses of zircon and garnet reveal that eclogite in the dome core traveled greater lateral distances and interacted more extensively with the surrounding gneisses during crustal flow relative to eclogite in the margin of the dome. These results show that a multi-method, multi-systems approach to studying eclogite in migmatite domes can be used to evaluate the relative magnitude and trajectory of deep orogenic crustal flow. In the Entia dome, two geochemically distinct groups of mafic rocks are identified based on their major element geochemistry but nevertheless share a common igneous protolith emplacement history marked by crustal contamination and enrichment in a continental arc-like setting. The least-deformed, dry mafic granulites preserve evidence for mid/HP metamorphism (~8–12 kbar), whereas moderately deformed garnet amphibolites record peak-T (~800ºC); the most deformed amphibolites record late retrogressive metamorphism in the mid crust during cooling. Magnetic fabric analysis reveals that the highest-T and plane to constrictional strains are preserved in the core of the Entia dome, representing a transposition of material deformed in compression in the lower- to mid-crust as material enters the central exhumation channel of the dome. In contrast, lower-T and predominantly plane to flattening strains are preserved along the margins of the dome and represent deformation of material flowing towards the dome apex and outward along the margins of the domal structure in the shallow crust in an overall extensional regime. These results are consistent with numerical model predictions of the internal strain patterns of gneiss domes formed during exhumation. Although the Montagne Noire and Entia domes are in different orogens and tectonic settings, they both provide field-based insight about the temporal, geochemical and structural records of crustal flow dynamics inherent to orogenic cores prior to their collapse. The Montagne Noire eclogites reveal that at least parts of the dome are deeply sourced, and that rocks exhumed in the core of domes may have a more extensive and protracted history of deep-crustal flow than those exhumed at the margin. In addition, mafic rocks in both domes provide a set of geochemical tools to distinguish multiple sources and origins of protolith material incorporated in domes. The Entia dome in particular reveals that the latest and potentially deepest-sourced material may be preferentially preserved in dome cores and record constrictional fabrics associated with deformation in the deep crust. These early records of metamorphism and processes animating the mid- to deep crust of orogens are effectively preserved in mafic rocks that can be successfully investigated using high-resolution in situ petrochronological, geochemical, structural and geothermobarometric tools. The integration of structural and metamorphic analyses of refractory lithologies in the Montagne Noire and Entia domes provides the most comprehensive P–T–t–d–X records of internal orogenic recycling and constraints on the magnitudes, rates and volumes of mass and heat transfer that contribute to the long-term stabilization of continents over time during crustal flow.
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    Temperature and Pressure Effects on Tissue Sealing and Protein Denaturation
    (2016-05) Scheumann, Joel
    Tissue sealing is an attractive method for tissue sealing in laparoscopic (minimally in-vasive) surgeries as it does not leave any materials in a patient’s body. Most of the re-search for tissue sealing has been concerned on the end-goal results of burst pressure, and not as much time has been spent investigating the more fundamental properties of tissue sealing which include temperature, pressure, time, vessel composition, disease state, and sealing modality (i.e., thermal, radiofrequency, and ultrasonic). This work in-vestigates temperature and pressure by studying how these parameters affect collagen denaturation and burst pressure. Ethicon provided carotid arteries that were sealed under controlled temperature and pressure with a constructed Thermal Jig. Additionally, dena-turation of collagen was studied with the use of carotid arteries and rat tail tendons with the use of FTIR spectroscopy under temperature and pressure control from an ATR ac-cessory. From the research, it was determined that the burst pressure was highest with the temperature of 140ºC. Changing the weight from 20lb to 50lb did not yield any sig-nificant difference. The results for burst pressure from the treatments of 100ºC;80psi;30s, 100ºC;330psi;30s, 140ºC;80psi;30s, and 140ºC;330psi;30s were 188.4 ± 55.3mm Hg, 439.9 ± 232.6mm Hg, 647.3 ± 241.3mm Hg, and 678.1 ± 153.7mm Hg, respectively. Denaturation onset was observed to be delayed with the application of pressure. For rat tail tendon, denaturation onset was observed to be 58.0 ± 2.5ºC and 60.1 ± 4.9ºC for loads of 0N and 2N, respectively. For carotid artery, the denaturation onset was observed to be 59.8 ± 0.7ºC, 59.8 ± 1.9ºC, 79.1 ± 4.3ºC, indeterminable, and indeterminable for loads of 0N, 2N, 10N, 20N, and 50N, respectively. To form an effec-tive seal one must increase the temperature above 100ºC. Additionally, the denaturation was delayed significantly as the load was increased. This mechanical pressure correlates with results from osmotic pressure that also cause a delay in protein denaturation. Fu-ture work should investigate protein denaturation to higher temperature and tissue fu-sion by varying disease state of arteries, tissue composition (i.e., collagen and elastin content), and sealing time.