Matching Items (17)
Description
Although wind turbine bearings are designed to operate 18-20 years, in the recent years premature failure among these bearings has caused this life to reduce to as low as a few months to a year. One of the leading causes of premature failure called white structure flaking is a mechanism that was first cited in literature decades ago but not much is understood about it even today. The cause of this mode of failure results from the initiation of white etched cracks (WECs). In this report, different failure mechanisms, especially premature failure mechanisms that were tested and analyzed are demonstrated as a pathway to understanding this phenomenon. Through the use of various tribometers, samples were tested in diverse and extreme conditions in order to study the effect of these different operational conditions on the specimen. Analysis of the tested samples allowed for a comparison of the microstructure alterations in the tested samples to the field bearings affected by WSF.
ContributorsSharma, Aman (Author) / Foy, Joseph (Thesis director) / Adams, James (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2015-05
Description
A model has been developed to modify Euler-Bernoulli beam theory for wooden beams, using visible properties of wood knot-defects. Treating knots in a beam as a system of two ellipses that change the local bending stiffness has been shown to improve the fit of a theoretical beam displacement function to edge-line deflection data extracted from digital imagery of experimentally loaded beams. In addition, an Ellipse Logistic Model (ELM) has been proposed, using L1-regularized logistic regression, to predict the impact of a knot on the displacement of a beam. By classifying a knot as severely positive or negative, vs. mildly positive or negative, ELM can classify knots that lead to large changes to beam deflection, while not over-emphasizing knots that may not be a problem. Using ELM with a regression-fit Young's Modulus on three-point bending of Douglass Fir, it is possible estimate the effects a knot will have on the shape of the resulting displacement curve.
ContributorsSexton, Thurston Bryant (Author) / Takahashi, Timothy (Thesis director) / Jones, Donald (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / School of Human Evolution and Social Change (Contributor)
Created2015-05
Description
The following is a report that will evaluate the microstructure of the nickel-based superalloy Hastelloy X and its relationship to mechanical properties in different load conditions. Hastelloy X is of interest to the company AORA because its strength and oxidation resistance at high temperatures is directly applicable to their needs in a hybrid concentrated solar module. The literature review shows that the microstructure will produce different carbides at various temperatures, which can be beneficial to the strength of the alloy. These precipitates are found along the grain boundaries and act as pins that limit dislocation flow, as well as grain boundary sliding, and improve the rupture strength of the material. Over time, harmful precipitates form which counteract the strengthening effect of the carbides and reduce rupture strength, leading to failure. A combination of indentation and microstructure mapping was used in an effort to link local mechanical behavior to microstructure variability. Electron backscatter diffraction (EBSD) and energy dispersive spectroscopy (EDS) were initially used as a means to characterize the microstructure prior to testing. Then, a series of room temperature Vickers hardness tests at 50 and 500 gram-force were used to evaluate the variation in the local response as a function of indentation size. The room temperature study concluded that both the hardness and standard deviation increased at lower loads, which is consistent with the grain size distribution seen in the microstructure scan. The material was then subjected to high temperature spherical indentation. Load-displacement curves were essential in evaluating the decrease in strength of the material with increasing temperature. Through linear regression of the unloading portion of the curve, the plastic deformation was determined and compared at different temperatures as a qualitative method to evaluate local strength.
ContributorsCelaya, Andrew Jose (Author) / Peralta, Pedro (Thesis director) / Solanki, Kiran (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2015-05
Description
Widespread knowledge of fracture mechanics is mostly based on previous models that generalize crack growth in materials over several loading cycles. The objective of this project is to characterize crack growth that occurs in titanium alloys, specifically Grade 5 Ti-6Al-4V, at the sub-cycle scale, or within a single loading cycle. Using scanning electron microscopy (SEM), imaging analysis is performed to observe crack behavior at ten loading steps throughout the loading and unloading paths. Analysis involves measuring the incremental crack growth and crack tip opening displacement (CTOD) of specimens at loading ratios of 0.1, 0.3, and 0.5. This report defines the relationship between crack growth and the stress intensity factor, K, of the specimens, as well as the relationship between the R-ratio and stress opening level. The crack closure phenomena and effect of microcracks are discussed as they influence the crack growth behavior. This method has previously been used to characterize crack growth in Al 7075-T6. The results for Ti-6Al-4V are compared to these previous findings in order to strengthen conclusions about crack growth behavior.
ContributorsNazareno, Alyssa Noelle (Author) / Liu, Yongming (Thesis director) / Jiao, Yang (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
The study of the mechanical behavior of nanocrystalline metals using microelectromechanical systems (MEMS) devices lies at the intersection of nanotechnology, mechanical engineering and material science. The extremely small grains that make up nanocrystalline metals lead to higher strength but lower ductility as compared to bulk metals. Effects of strain-rate dependence on the mechanical behavior of nanocrystalline metals are explored. Knowing the strain rate dependence of mechanical properties would enable optimization of material selection for different applications and lead to lighter structural components and enhanced sustainability.
ContributorsHall, Andrea Paulette (Author) / Rajagopalan, Jagannathan (Thesis director) / Liao, Yabin (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2014-05
Description
Due to increasing lack of resources and funding for budding student musicians, it is often not possible for this demographic to create, record, and produce their original music in the same high-budget studio environment in which music has been traditionally made. The objective of this project is to explore alternatives which are more accessible to young independent musicians and reveal the most cost-efficient routes to obtain a high-quality result. To make this comparison, the group created budget recordings of their original music in a bedroom in true DIY fashion, and then recorded the same songs in a professional music studio using the best music and recording equipment available. The DIY recordings were mixed and mastered by the group members themselves, as well as separately by a professional audio engineer. The studio recordings were also mixed and mastered by a professional audio engineer, resulting in three final products with varying costs and quality. Ultimately, the group found that without mixing and mastering experience, it is very difficult to achieve high quality results. With the same budget recorded tracks, the group found that quality of the final product vastly increased when a professional audio engineer mixed and mastered the tracks. As far as the quality of the result, the studio recorded tracks were by far the best. Not only was the quality of the sounds from the high-end music and recording equipment much higher, the band had more freedom to be creative without the responsibility of simultaneously serving as recording engineers as was the case in the low budget recordings. The group concluded that this project was highly successful and demonstrated that high quality results could be obtained on a budget. The DIY recording techniques used in this project prove that independent musicians without access to expensive equipment and resources can still produce high quality music at the cost of more effort to serve as audio engineers in addition to musicians. However, recording in a studio with the help of a producer and professional audio engineers affords creative freedom and an increase in sound quality that is simply not possible to reproduce without the equipment and expertise that money can buy.
ContributorsBonk, Alan (Co-author) / Dhuyvetter, Nicholas Alan (Co-author) / Wickham, Kevin (Co-author) / Tobias, Evan (Thesis director) / Swoboda, Deanna (Committee member) / W.P. Carey School of Business (Contributor) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
The goal of this research is to compare the mechanical properties of CP-Ti and Ti-O and to understand the relationship between a material's microstructure and its response to fatigue. Titanium has been selected due to its desirable properties and applicability in several engineering fields. Both samples are polished and etched in order to visualize and characterize the microstructure and its features. The samples then undergo strain-controlled fatigue tests for several thousand cycles. Throughout testing, images of the samples are taken at zero and maximum load for DIC analysis. The DIC results can be used to study the local strains of the samples. The DIC analysis performed on the CP-Ti sample and presented in this study will be used to understand how the addition of oxygen in the Ti-O impacts fatigue response. The outcome of this research can be used to develop long-lasting, high strength materials.
ContributorsRiley, Erin Ashland (Author) / Solanki, Kiran (Thesis director) / Oswald, Jay (Committee member) / School of Art (Contributor) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
This creative project is centered around the development and pitch of a 10-hour TV series consisting of story and character documents, pitch deck and pitch script; a full length draft of the series pilot is included. Development of the series' story and characters were done alongside Thesis Director Peter Murrieta.
ContributorsLe, Brian (Author) / Murrieta, Peter (Thesis director) / Bernstein, Gregory (Committee member) / Barrett, The Honors College (Contributor) / The Sidney Poitier New American Film School (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2023-05
DescriptionThis creative project is centered around the development and pitch of a 10-hour TV series consisting of story and character documents, pitch deck and pitch script; a full length draft of the series pilot is included. Development of the series' story and characters were done alongside Thesis Director Peter Murrieta.
ContributorsLe, Brian (Author) / Murrieta, Peter (Thesis director) / Bernstein, Gregory (Committee member) / Barrett, The Honors College (Contributor) / The Sidney Poitier New American Film School (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2023-05
DescriptionThis creative project is centered around the development and pitch of a 10-hour TV series consisting of story and character documents, pitch deck and pitch script; a full length draft of the series pilot is included. Development of the series' story and characters were done alongside Thesis Director Peter Murrieta.
ContributorsLe, Brian (Author) / Murrieta, Peter (Thesis director) / Bernstein, Gregory (Committee member) / Barrett, The Honors College (Contributor) / The Sidney Poitier New American Film School (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2023-05