Matching Items (9)
Description
Cavitation erosion is a significant cause of wear in marine components, such as impellers, propellers or rudders. While the erosion process has been widely studied on metals, the effect of cavitation on polymers is not well-understood. The stress response in metals differs greatly from that of polymers, e.g. rate and temperature effects are far more important, thus damage and wear mechanisms of polymers under cavitating flows are significantly different. In this work, heat-driven failure caused by viscous dissipation and void nucleation resulting from tensile stresses arising from stress wave reflections are investigated as two possible material failure mechanisms.
As a first step in developing a fundamental understanding of the cavitation erosion process on polymer surfaces, simulations are performed of the collapse of individual bubbles against a compliant surface e.g. metallic substrates with polyurea coatings. The surface response of collapse-driven impact loads is represented by a idealized, time-dependent, Gaussian pressure distribution on the surface. A two-dimensional distribution of load radii and durations is considered corresponding to characteristic of cavitating flows accelerated erosion experiments. Finite element simulations are performed to fit a response curve that relates the loading parameters to the energy dissipated in the coating and integrated with collapse statistics to generate an expected heat input into the coating.
The impulsive pressure, which is generated due to bubble collapse, impacts the material and generates intense shock waves. The stress waves within the material reflects by interaction with the substrate. A transient region of high tensile stress is produced by the interaction of these waves. Simulations suggests that maximum hydrostatic tension which cause failure of polyurea layer is observed in thick coating. Also, the dissipated viscous energy and corresponding temperature rise in a polyurea is calculated, and it is concluded that temperature has influence on deformation.
As a first step in developing a fundamental understanding of the cavitation erosion process on polymer surfaces, simulations are performed of the collapse of individual bubbles against a compliant surface e.g. metallic substrates with polyurea coatings. The surface response of collapse-driven impact loads is represented by a idealized, time-dependent, Gaussian pressure distribution on the surface. A two-dimensional distribution of load radii and durations is considered corresponding to characteristic of cavitating flows accelerated erosion experiments. Finite element simulations are performed to fit a response curve that relates the loading parameters to the energy dissipated in the coating and integrated with collapse statistics to generate an expected heat input into the coating.
The impulsive pressure, which is generated due to bubble collapse, impacts the material and generates intense shock waves. The stress waves within the material reflects by interaction with the substrate. A transient region of high tensile stress is produced by the interaction of these waves. Simulations suggests that maximum hydrostatic tension which cause failure of polyurea layer is observed in thick coating. Also, the dissipated viscous energy and corresponding temperature rise in a polyurea is calculated, and it is concluded that temperature has influence on deformation.
ContributorsPanwar, Ajay (Author) / Oswald, Jay (Thesis advisor) / Dooley, Kevin (Committee member) / Chen, Kangping (Committee member) / Arizona State University (Publisher)
Created2015
Description
Seamless carbon fiber reinforced polymer matrix (CFRP) composites are being investigated in many structural applications with the purpose of withstanding the extreme pressures and maintaining stiffness in mechanical systems. This report focuses on: fabrication of CFRP tubes and end caps, the production of a pressurization system to test standards set by Fiber Reinforced Composite (FRC) Pipe and Fittings for Underground Fire Protection Service [1], developing a library for different damage types for seamless composite pipes, and evaluating pre-existing flaws with flash thermography, carrying out hydrostatic testing, and performing nondestructive testing (NDT) to characterize damage induced on the pipes such as cracking, crazing, and fiber breakage. The tasks outlined will be used to develop design guidelines for different combinations of loading systems.
ContributorsFoster, Collin William (Author) / Yekani Fard, Masoud (Thesis director) / Chattopadhyay, Aditi (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
The U.S. Navy is interested in evaluating the dielectric performance of SF6 at 30 kHz in order to develop optimal bushing designs and to ensure reliable operation for the Very Low Frequency/ Low Frequency (VLF/LF) transmitting stations. The breakdown experiments of compressed SF6 at 30 kHz in the pressure range of 1-5 atm were conducted in both the uniform field (plane-plane gap) and the non-uniform field (rod-plane gap). To understand the impact of pressure on the breakdown voltage of SF6 at VLF/LF, empirical models of the dielectric strength of SF6 were derived based on the experimental data and regression analysis. The pressure correction factors that present the correlation between the breakdown voltage of SF6 at VLF/LF and that of air at 50/60 Hz were calculated. These empirical models provide an effective way to use the extensively documented breakdown voltage data of air at 60 Hz to evaluate the dielectric performance of SF6 for the design of VLF/LF high voltage equipment. In addition, several breakdown experiments and similar regression analysis of air at 30 kHz were conducted as well. A ratio of the breakdown voltage of SF6 to that of air at VLF/LF was calculated, from which a significant difference between the uniform gap and the non-uniform gap was observed. All the models and values provide useful information to evaluate and predict the performance of the bushings in practice.
ContributorsHan, Jian (Author) / Gorur, Ravi S (Thesis advisor) / Farmer, Richard G (Committee member) / Karady, George G. (Committee member) / Arizona State University (Publisher)
Created2010
Description
Essential to the field of petroleum engineering, well testing is done to determine the important physical characteristics of a reservoir. In the case of a constant production rate (as opposed to a constant pressure), the well pressure drop is a function of both time and the formation's boundary conditions. This pressure drop goes through several distinct stages before reaching steady state or semi-steady state production. This paper focuses on the analysis of a circular well with a closed outer boundary and details the derivation of a new approximation, intended for the transient stage, from an existing steady state solution. This new approximation is then compared to the numerical solution as well as an existing approximate solution. The new approximation is accurate with a maximum 10% margin of error well into the semi-steady state phase with that error decreasing significantly as the distance to the closed external boundary increases. More accurate over a longer period of time than the existing line source approximation, the relevance and applications of this new approximate solution deserve further exploration.
ContributorsKelso, Sean Andrew (Author) / Chen, Kangping (Thesis director) / Liao, Yabin (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / School of Music (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
The aim of this dissertation was to explore the construct and experiences of gender norm resistance (GNR) using both quantitative and qualitative methods. The purpose of Study 1 was to standardize and universalize what is already known about GNR by creating a quantitative GNR measure. In so doing, I operationalized the implicit and explicit GNR framework described by Way and colleagues (2014). On a sample of adolescents (484 6th grade students; girls = 234; 10-13 years old, Mage = 11.44 years, SD = .56) the GNR measure was tested for gender differences and to explore how GNR aligns with and differs from other constructs related to gender identity and peer relations. The results supported the two-factor model (implicit and explicit forms of GNR), supported convergent and discriminant validity, and identified mean level differences depending on GNR form, gender, ethnic identity, and gender typicality. The purpose of Study 2 was to explore why young men resist gender norms, what motivates their acts of resistance, and how they understand those motives. I expected that implicit GNR would be motivated by the pursuit of authentic nonconformity and would involve an awareness of norms, feeling gender atypical, and authenticity. I expected that explicit GNR would be motivated by a dislike of gender norms, and that it would involve an awareness of, dislike of, and pressure to conform to gender norms. The results supported these expectations and indicated a subtype of GNR, activist GNR, defined by the desire to change gender norms to benefit the social group. Both studies rely on the resistance/accommodation framework to describe the balance of conformity and resistance as individuals navigate systems of power and oppression.
ContributorsNielson, Matthew G (Author) / Martin, Carol Lynn (Thesis advisor) / Lindstrom Johnson, Sarah (Committee member) / Miller, Cindy F (Committee member) / Rogers, Leoandra Onnie (Committee member) / Arizona State University (Publisher)
Created2020
Description
This thesis is part of a larger research project, conducted by Elizabeth Stallings Young, which aims to improve understanding about the factors controlling the process of MIDP and the interaction between the biochemical reactions and the hydrological properties of soils treated with MIDP. Microbially Induced Desaturation and Precipitation (MIDP) is a bio-geotechnical process by which biogenic gas production and calcite mineral bio-cementation are induced in the pore space between the soil particles, which can mitigate earthquake induced liquefaction (Kavazanjian et al. 2015). In this process substrates are injected which stimulate indigenous nitrate reducing bacteria to produce nitrogen and carbon dioxide gas, while precipitating calcium carbonate minerals. The biogenic gas production has been shown to dampen pore pressure build up under dynamic loading conditions and significantly increase liquefaction resistance (Okamura and Soga 2006), while the precipitation of calcium carbonate minerals cements adjacent granular particles together. The objective of this thesis was to analyze the recorded pore pressure development as a result of biogenic gas formation and migration, over the entire two-dimensional flow field, by generating dynamic pressure contour plots, using MATLAB and ImageJ software. The experiment was run in a mesoscale tank that was approximately 114 cm tall, 114 cm wide and 5.25 cm thick. Substrate was flushed through the soil body and the denitrifying reaction occurred, producing gas and correspondingly, pressure. The pressure across the tank was recorded with pore pressure sensors and was loaded into a datalogger. This time sensitive data file was loaded into a MATLAB script, MIDPCountourGen.m, to create pressure contours for the tank. The results from this thesis include the creation of MIDPContourGen.m and a corresponding How-To Guide and pore pressure contours for the F60 tank. This thesis concluded that the MIDP reaction takes a relatively short amount of time and that the residual pressure in the tank after the water flush on day 17 offers a proof of effect of the MIDP reaction.
ContributorsCoppinger, Kristina Marie (Author) / van Paassen, Leon (Thesis director) / Kavazanjian, Edward (Committee member) / Stallings-Young, Elizabeth (Committee member) / Civil, Environmental and Sustainable Eng Program (Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
The goal of this study was to explore the relationship between locus of control and the influence of an unethical authority figure. This research is a preliminary, exploratory study given research design limits. It was hypothesized that subjects oriented towards internal locus of control are better able to resist pressure from an unethical authority figure. Subjects oriented towards the powerful others and chance orientations were hypothesized to be less able to resist pressure from an unethical authority figure. The results found that the presence of an unethical authority figure had little to no influence on self-perceived unethical decision-making; the difference in unethical behavior between cases with an authority figure present and without one present was not statistically significant. Further, no support was found for the hypotheses as no statistically significant relationship between locus of control orientations and the difference between the control case and test case was found (R2 = 0.02, model P-value > 0.05). Further analysis confirmed the results of Detert et al. (2008), finding no relationship between survey subjects’ locus of control orientations and unethical decision-making. Additional analysis indicates a relationship between unethical decision-making and gender (B = -5.14, P = 0.03, P < 0.05), providing some interesting avenues for future research.
ContributorsAmorosi, Kaitlin (Author) / Samuelson, Melissa (Thesis director) / Orpurt, Steven (Committee member) / Department of Finance (Contributor) / School of Accountancy (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
Manufacturing production is limited by three main factors, cost, both overall and on a per unit basis, final product quality, and process repeatability or frequency. Even producing small objects through the casting of epoxy resin, a liquid substance capable of hardening when in contact with a catalyst material presents these same issues. There are three distinct areas of epoxy resin casting influenced by each of these manufacturing factors, the material used to create molds, the air process applied to minimize defects, and resin demold time. This investigation was designed to determine the impact the three factors of manufacturing production have on the casting epoxy resin. Each category had numerous tests conducted to determine the best combination of production in terms of low cost, high quality, and high levels of repeatability. Ultimately, the best combination was the use of a platinum silicone called Mold Star 15, a pressure chamber, and an epoxy resin with a 12-hour cure time, called Amazing Resin. The final cost to create 100 products is $410.85. However, it should be noted for the highest quality dice, the utilization of a pressure chamber is required while the mold materials are interchangeable.
ContributorsFoster, Whitney (Author) / Delp, Deana (Thesis director) / Rajadas, John (Committee member) / Barrett, The Honors College (Contributor) / Engineering Programs (Contributor)
Created2022-05
Description
Spirometry is a type of pulmonary function test that measures the amount of air volume and the speed of air flow from a patient's breath in order to assess lung function. The goal of this project is to develop and validate a mobile spirometer technology based on a differential pressure sensor. The findings in this paper are used in a larger project that combines the features of a capnography device and a spirometer into a single mobile health unit known as the capno-spirometer. The following paper discusses the methods, experiments, and prototypes that were developed and tested in order to create a robust and accurate technology for all of the spirometry functions within the capno-spirometer. The differential pressure sensor is set up with one inlet measuring the pressure inside the spirometer tubing and the other inlet measuring the ambient pressure of the environment. The inlet measuring the inside of the tubing is very sensitive to its orientation and position with respect to the path of the air flow. It is found that taking a measurement from the center of the flow is 50% better than from the side wall. The sensor inlet is optimized at 37 mm from the mouthpiece inlet. The unit is calibrated by relating the maximum pressure sensor voltage signal to the peak expiratory flow rate (PEF) taken during a series of spirometry tests. In conclusion, this relationship is best represented as a quadratic function and a calibration equation is computed to provide a flow rate given a voltage change. The flow rates are used to calculate the four main spirometry parameters: PEF, FVC, FEV1, and FER. These methods are then referenced with the results from a commercial spirometer for validation. After validation, the pressure-based spirometry technology is proven to be both robust and accurate.
ContributorsMiller, Dylan (Author) / Forzani, Erica (Thesis advisor) / Trimble, Steve (Committee member) / Xian, Xiaojun (Committee member) / Arizona State University (Publisher)
Created2013