2017 - Mines Theses & Dissertations
http://hdl.handle.net/11124/118
2024-03-29T07:16:26ZEffects of thermal processing variations on microstructure and high cycle fatigue of beta-STOA Ti-6Al-4V
http://hdl.handle.net/11124/172049
Effects of thermal processing variations on microstructure and high cycle fatigue of beta-STOA Ti-6Al-4V
McArthur, Byron
Titanium alloys are often used in fatigue-limited structural applications within the aerospace industry. Because of the primary processing control and reactivity of titanium, the fatigue life of the material is predominantly dependent upon the α-phase microstructure, rather than internal defects such as voids or inclusions. For titanium alloy Ti – 6 wt % aluminum - 4 wt % vanadium (Ti-6Al-4V), the influence of cooling rate from above the ß-transus is known to affect the resulting microstructure and influence high cycle fatigue life. The transfer time from the furnace to the water-quenching bath significantly influences the cooling rate, and thus controls the microstructural development and fatigue properties. A hydraulic actuator produced from a Ti-6Al-4V forging failed prematurely during fatigue testing, and provided the industrial motivation for this work. A quench dilatometer was used, along with subsequent scanning electron microscopy, to explore the microstructural variations produced as a function of thermal history. Rotating bending fatigue testing in the high cycle fatigue regime highlighted a two orders of magnitude reduction in fatigue life due to an increased quenching transfer time. The increased quench transfer time was shown to create packets of co-oriented α laths that facilitated crack initiation. Fatigue crack growth rate measurements were also used to quantify post-initiation crack growth rates in microstructures produced by different quench delay times. Long crack growth rates were found to be similar for short and long quench delay times. Post-mortem fractographic analysis and electron back scattered diffraction aided in determining the microstructural influence on fatigue crack initiation and propagation, indicating that long, planar basal slip lengths contribute to crack nucleation. Based upon these findings, it is found that even minor variations in quench transfer time can significantly influence the high cycle fatigue life of titanium alloys.
Includes bibliographical references.; 2017 Fall.
2017-01-01T00:00:00ZCharacterization of magnetically driven colloidal microwheels and their fibrinolytic applications
http://hdl.handle.net/11124/172048
Characterization of magnetically driven colloidal microwheels and their fibrinolytic applications
Disharoon, Dante
Colloids carrying payloads of medication have become a popular drug delivery approach. Since it is not always possible to rely on blood circulation to distribute the colloids to the target site in the body, researchers seek to develop methods of controlling colloid movement. We advance the development of a magnetic system that moves colloids using a canted rotating magnetic field. Beads containing superparamagnetic iron oxide crystals assemble into wheel-like structures that rotate in alignment with the field and roll via wet friction along adjacent surfaces. These micro-wheels (μwheels) are suitable for drug delivery. We utilize μwheels to deliver tissue plasminogen activator (tPA) to a blood clot. tPA can be used to treat stroke but is rarely used because it can cause hemorrhaging. We show that μwheels functionalized with tPA combine mechanical and biochemical mechanisms to achieve enhanced fibrinolysis over that of soluble tPA at therapeutic concentrations. μwheels conjugated with an effective tPA concentration of 3.6 μg/mL degrade fibrin twofold faster than soluble tPA at 10 μg/mL. μwheels are an effective fibrinolytic because of their ability to target, penetrate into and concentrate at a clot. Here, we show that μwheels powered by a magnetic field are capable of exiting a laminar flow field and entering a connecting blocked channel. These experiments suggest that the μwheel translational mechanism is robust enough to navigate vasculature in order to target occlusions. Finally, we use total internal reflection microscopy (TIRM) to characterize the mechanism of μwheel translation. A sphere translating against a glass slide under influence of the magnetic field is 89 ± 39 nm from the slide. The gap distance can be affected by changing the load force on the μwheel or electrochemical interactions between the μwheel and surface, suggesting that μwheel interactions with vasculature will be tunable. The μwheels used herein are a novel and exciting drug delivery system whose potential applications are not limited to treating stroke.
Includes bibliographical references.; 2017 Fall.
2017-01-01T00:00:00ZUsing passive seismic data from multiple sensors for predicting earth dam and levee erosion
http://hdl.handle.net/11124/172047
Using passive seismic data from multiple sensors for predicting earth dam and levee erosion
Johnson, C. Travis
Earth dams and levees support industrial applications, flood defense, and irrigation infrastructure around the world. These structures naturally undergo erosion over time and massive erosion events can result in catastrophic failure. When these structures fail, disastrous floods can displace or even kill nearby residents. Thus, it is important to know when and where these structures have progressive internal erosion events so appropriate action can reduce the impact of the erosion. This work explores improvements on the performance of previous machine learning methods for the continuous health monitoring of earth dams and levees (EDLs). Specifically, we explore ensemble classification algorithms (Bagging, Boosting, and Random Forest) to combine the passive seismic data from multiple sensors; we note that previous work only considered the data from one sensor in the wired sensor network. By considering features extracted from the signals of multiple sensors, Boosting with support vector machines (SVMs) shows a 1.5 to 41.7% increase in F1 score over single support vector machine (SVM) models depending on the specific sensor chosen for the single SVM. We also explore the use of SVM models trained on data from distinct sensors for visualizing the locations of detected erosion events in the structure.
Includes bibliographical references.; 2017 Fall.
2017-01-01T00:00:00ZGeologic characterization and petroleum potential of the upper Cretaceous (Turonian) Wall Creek member and basement-involved hinterland vergent backthrusting, Salt Creek field, WY, U.S.A.
http://hdl.handle.net/11124/172046
Geologic characterization and petroleum potential of the upper Cretaceous (Turonian) Wall Creek member and basement-involved hinterland vergent backthrusting, Salt Creek field, WY, U.S.A.
Payne, Joshua M.
The Upper Cretaceous (Turonian) Wall Creek Member of the Frontier Formation represents the distal reaches of a progradational clastic wedge that formed in response to the Sevier orogeny. Following uplift along the Sevier highlands, sediments were eroded and subsequently transported east and deposited into the Western Interior Basin (WIB). These deposits have been exploited for oil and gas since the late 19th century and still represent a prominent target for horizontal exploration in the Rocky Mountain region. At Salt Creek Field, oil and gas has been produced from the sandstones of the Frontier Formation for over 100 years from a large, asymmetrical, anticlinal trap. This study integrates core, wireline log, and 3D seismic data at Salt Creek Field to characterize the Turonian Wall Creek Member with respect to basin and field scale depositional processes, structure, and reservoir quality. Furthermore, re-interpretation of the deeper structure shows greater complexity than previously understood. Integration of publically available and unpublished core, wireline log, and 3D seismic data lead to new interpretations at Salt Creek Field that carry significant implications for exploration within the intermountain basins of Wyoming and throughout the Rocky Mountain region: 1) the asymmetrical anticline at Salt Creek Field formed as a fault-propagation fold induced by the occurrence of multiple (five) hinterland-verging back thrusts. The multiple backthrusts occurred in response to the eastward verging thrust that bounds the western margin of the PRB, a Laramide feature. 2) A linear, bar-like sandbody of coarse-grained, transgressive reworked deposits are observed at Salt Creek Field and lie between the delta front sandstones of the Upper Wall Creek Member and the overlying marine Cody Shale. These sandstones form a structurally enhanced stratigraphic trap and contain above average oil saturation. A similar, reworked transgressive sandstone is observed at Spearhead Field in the PRB. These sandstones represent an active target for oil and gas exploration. 3) A geometrically confined medium-grained sandstone with an erosive base is located at the base of the Wall Creek Member along a relatively thick southwest-northeast trending depositional fairway at Salt Creek Field. The fairway of deposition suggests lowstand incision and/or the presence of syndepositional paleostructural trends associated with basement lineaments that resulted in accommodation remnants. Similar sandbodies of the Muddy Sandstone provide excellent reservoirs and are actively explored for in the PRB.
Includes bibliographical references.; 2017 Fall.
2017-01-01T00:00:00Z