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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
The flipped classroom is a teaching method that flips the activities done in and out of class, i.e., concepts are learned out of class and problems are worked in class under the supervision of the instructor. Studies have indicated several benefits of the FC, including improved performance and engagement. In the past years, further studies have investigated the benefits of FC in statics, dynamics, and mechanics of materials courses and indicate similar performance benefits. However, these studies address a need for additional studies to validate their results due to the short length of their research or small classroom size. In addition, many of these studies do not measure student attitudes, such as self-efficacy, or the difference in time spent out of class on coursework. The objective of this research is to determine the effectiveness of the flipped classroom system (FC) in comparison to the traditional classroom system (TC) in a large mechanics of materials course. Specifically, it aims to measure student performance, student self-efficacy, student attitudes on lecture quality, motivation, attendance, hours spent out of class, practice, and support, and difference in impact between high, middle, and low achieving students. In order to accomplish this, three undergraduate mechanics of materials courses were analyzed during the spring 2015 semester. One FC section served as the experimental group (92 students), while the two TC sections served as the control group (125 students). To analyze student self-efficacy and attitudes, a survey instrument was designed to measure 18 variables and was administered at the end of the semester. Standardized core outcomes were compared between groups to analyze performance. This paper presents the specific course framework used in this FC, detailed results of the quantitative and qualitative analysis, and discussion of strengths and weaknesses. Overall, an overwhelming majority of students were satisfied with FC and would like more of their classes taught using FC. Strengths of this teaching method include greater confidence, better focus, higher satisfaction with practice in class and assistance received from instructors and peers, more freedom to express ideas and questions in class, and less time required outside of class for coursework. Results also suggest that this method has a greater positive impact on high and low achieving students and leads to higher performance. The criticisms made by students focused on lecture videos to have more worked examples. Overall, results suggest that FC is more effective than TC in a large mechanics of materials course.
ContributorsLee, Andrew Ryan (Author) / Zhu, Haolin (Thesis director) / Middleton, James (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
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
Bangladesh is facing one of the largest mass poisonings in human history with over 77 million people affected by contaminated water each and every day. Over the last few years, the 33 Buckets team has come together to help fulfill this clean water need through filtration, education, and an innovative distribution system to inspire and empower people in Bangladesh and across the world. To start this process, we are working with the Rahima Hoque Girls' school in the rural area of Raipura, Bangladesh to give girls access to clean water where they spend the most time. Through our assessment trip in May 2012, we were able to acquire technical data, community input, and partnerships necessary to move our project forward. Additionally, we realized that in many cases, including the Rahima Hoque school, water problems are not caused by a lack of technology, but rather a lack of utilization and maintenance long-term. To remedy this, 33 Buckets has identified a local filter to have installed at the school, and has designed a small-scale business focused on selling clean water in bulk to the surrounding community. Our price point and association with the Rahima Hoque Girls' school makes our solution sustainable. Plus, with the success of our first site, we see the potential to scale. We already have five nearby schools interested in working to implement similar water projects, and with over 100,000 schools in Bangladesh, many of which lack access to the right water systems, we have a huge opportunity to impact millions of lives. This thesis project describes our journey through this process. First, an introduction to our work prior to the assessment trip and through the ASU EPICS program is given. Second, we include quantitative and qualitative details regarding our May 2012 assessment trip to the Rahima Hoque school and Dhaka. Third, we recount some of the experiences we were able to participate in following the trip to Bangladesh, including the Dell Social Innovation Challenge. Fourth, we examine the technical filtration methods, business model development, and educational materials that will be used to implement our solution this summer. Finally, we include an Appendix with a variety of social venture competitions and applications that we have submitted over the past two years, in addition to other supplementary materials. These are excellent examples of our diligence and provide unique insight into the growth of our project.
ContributorsStrong, Paul Andrew (Co-author) / Shah, Pankti (Co-author) / Huerta, Mark (Co-author) / Henderson, Mark (Thesis director) / El Asmar, Mounir (Committee member) / LaBelle, Jeffrey (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2013-05
Description
The focus of education in the classroom traditionally is one of fact memorization and recall. The teaching process of linear knowledge progression is not always in tune with the way that the human brain actually processes, conceptualizes, and comprehends concepts and information. In an introductory engineering class, focused on materials engineering and its related concepts, a system of lecture interventions has been put in place to increase concept comprehension by supplementing lecture units with various activities, from additional worksheets, explicit concept discussions, and most recently, YouTube videos showcasing specific concepts and situations. In an attempt to correct the lack of actual concept comprehension, these interventions seek to interact with the human mind in a way that capitalizes on its ability to process and interpret non-linear knowledge and information.
Using a concept test given prior to the lecture unit, and after, the difference in scores is used to recognize if the concepts presented have actually been comprehended. Used specifically in a lecture unit on solubility and solutions, the concept test tested student’s knowledge of supersaturated, saturated, and unsaturated solutions. With a visual identification and a written explanation, the student’s ability to identify and explain the three solutions was tested.
In order to determine the cause of the change in score from pre- to post-test, an analysis of the change in scores and the effects of question type and solution type was conducted. The significant results are as follows:
The change in score from pre- to post-test was found to be significant, with the only difference between the two tests being the lecture unit and intervention
From pre- to post-test, solution type had a significant effect on the score, with the unsaturated solution being the most easily recognized and explained solution type
Students that felt that the YouTube videos greatly increased their concept comprehension, on average, performed better than their counterparts and also saw a greater increase their score from pre- to post-test
Using a concept test given prior to the lecture unit, and after, the difference in scores is used to recognize if the concepts presented have actually been comprehended. Used specifically in a lecture unit on solubility and solutions, the concept test tested student’s knowledge of supersaturated, saturated, and unsaturated solutions. With a visual identification and a written explanation, the student’s ability to identify and explain the three solutions was tested.
In order to determine the cause of the change in score from pre- to post-test, an analysis of the change in scores and the effects of question type and solution type was conducted. The significant results are as follows:
The change in score from pre- to post-test was found to be significant, with the only difference between the two tests being the lecture unit and intervention
From pre- to post-test, solution type had a significant effect on the score, with the unsaturated solution being the most easily recognized and explained solution type
Students that felt that the YouTube videos greatly increased their concept comprehension, on average, performed better than their counterparts and also saw a greater increase their score from pre- to post-test
ContributorsLinich, Christopher Graham (Author) / Krause, Stephen (Thesis director) / Middleton, James (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2014-05
Description
The purpose of this creative thesis project is to create the framework of an educational class package based off of a course offered at Arizona State University. The course chosen for this project is an honors course titled Deductive Logic: Leadership and Management Techniques and is taught by Dean Kashiwagi, PhD. The class package is designed to be published over an online platform so students and professors from various institutions can access the material. Currently the platform is in its final stages of development and is slated to go live on July of 2014. The future development of the package will be geared towards facilitating interdisciplinary collaboration between institutions based off of course concepts.
ContributorsGunnoe, Jake Alan (Author) / Kashiwagi, Dean (Thesis director) / Kashiwagi, Jacob (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor) / Del E. Webb Construction (Contributor)
Created2014-05
Description
This thesis examines a variety of techniques implemented in modern senior design classes at Arizona State University with a special focus on the mechanical engineering senior capstone the traditional ABET capstone mechanical engineering capstone course, as well as the InnovationSpace Program. First, an overview regarding the growing profession of engineering and its relation to academic education is examined. Next, program and project overviews of both the capstone senior design course and the InnovationSpace are detailed, followed by a comparison of the two course's curriculum. Finally, key differences are highlighted, and suggestions introduced that might serve to improve both courses in the future. The senior design capstone course was found to lack accountability and diversity leading to a lack of innovative solutions. However, the course simultaneously succeeded in maintaining wellaccepted traditional engineer practices and documentation. The InnovationSpace program on the other hand provides accountability, diversity, and modern approaches to product development.
ContributorsKennedy, Patrick Bernales (Author) / Kuhn, Anthony (Thesis director) / Hedges, Craig (Committee member) / 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