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Laser Powder Directed Energy Deposition (LP-DED) Inconel 718: Laser Power and Heat Treatment Effect on Microstructure and Mechanical Properties
Get PDFThis study examines the microstructure and mechanical properties (tensile, hardness, and fatigue endurance) of laser powder-directed energy deposition (LP-DED) printed specimens with varying deposition parameters. Five samples with power inputs ranging from 350 to 2620W, all of similar thicknesses, were evaluated to enable a direct comparison. The varying specimens were heat treated, including stress relief, hot isostatic pressing, solution, and two-step aging. The resulting microstructures and their corresponding hardness values were compared at each heat treatment stage. The fully heat-treated specimens\u27 tensile properties and fatigue life were also examined and compared. Key findings of this study indicate that complete heat treatment will recrystallize and homogenize the microstructures of specimens printed, regardless of the varying parameters. This transformation shifts the microstructure from a predominantly dendritic structure to an austenitic one, incorporating annealing twins and increasing its hardness correspondingly. This heat treatment schedule produced nearly comparable tensile and fatigue properties, irrespective of the parameter variations. This investigation reveals that samples produced at the lowest laser power (350W) demonstrated a finer microstructure, improving overall mechanical properties. This research provides an efficient post-processing HT schedule for LP-DED Inconel 718 for aerospace applications. It contributes to the material\u27s characterization and the printing process\u27s standardization
My Little Poetic/prose Book Of Words, Sayings, And Stories In Broken Spanish And A Little Bit Of German / Mi Libro Chiquito De Poética / Prosa De Palabras, Dichos, Y Historias Español Fracturado Y Un Poquetito Alemán
Get PDFAcknowledgements
First and foremost, I would like to thank Jonathan Taylor and Sarah Thompson for the wonderful job they did in providing me with feedback. I took into consideration all their comments. Their comments aligned with Dr. Powers, and I really took a deeper look into my Spanish/English translations on whether I should have them or not. I found a happy medium for all of it. I also went back and looked at the rest of the class’s comments and made sure that I did not miss any of the details that were pointed out to me the first time around. As far as modeling after any author, I tried to think about how Claudia Rankine spoke in Citizen when she wrote her prose, as well as Sara Uribe’s prose writing in Antigona Gonzales. Both have a very simple language style that comes across strong when making points. Also, they both rely on personal stories. In addition, I thought about Ilya Kaminski in Deaf Republic, for he added a prose and titling style that allowed me to be creative, as well as aware of using similes. Gabrielle’s sample of her “Creative Experiments – Kind of Performance Objects I’ve been,” was my inspiration for my own creative experiment that I wrote on page 29. As far as my writing went, I kind of understood what I wanted from the outset of my master’s in fine arts, and I wrote in that manner. The inspiring professors were J.D. Pluecker, Andrea Cote Botero, Sylvia Aguilar, Nelson Cardenas, and Tim Hernandez. I especially would like to thank my committee for all their help and encouragement which are as follows: UTEP Associate Professor of Creative Writing and Chair of Committee, Andrea Cote Botero; UTEP Assistant Professor of Creative Writing, Sylvia Aguilar; and IU East Professor of English / Director and Advisor of Women’s and Gender Studies, Edwina Helton
Mechanical stability of body-centered cubic iron in Born-von Kármán parameter space using evolutionary algorithms
No full textThis study aims to assess the mechanical stability of body-centered cubic (BCC) structure, focusing on pure iron as a representative case. The primary approach involves utilizing phonon dispersion curves analysis to gain insights into the vibrational properties and overall stability of the crystal lattice through a multi-faceted computational approach. The goal of the study is to find the regions (pockets) in Born-von Kármán (BvK) parameter space where the crystal is stable for certain temperature and pressure.
This involves setting up the crystal parameters, creating a body-centered cubic (BCC) crystal with specific lattice parameters (2.86 for iron) establishing force constants, and employing Phonopy for phonon dispersion analysis. We developed a genetic algorithm to investigate the mechanical stability of body-centered cubic (BCC) iron in reduced BvK parameter space. For each genetic solution, we calculate the phonon dispersion relations by computing the dynamical matrix at various grid points across the Brillouin Zone. We then evaluate the stability of each solution by measuring deviations from predefined mechanical stability conditions.
Introduction of the RMSE metric provides a quantitative assessment of the accuracy of the computational model. The imaginary frequencies identified during the phonon dispersion analysis highlight potential areas of instability in the BvK space, and application of a genetic algorithm serves as an innovative approach to optimize the model and enhance its accuracy.
The comprehensive nature of this analysis positions it as a foundational study for further exploration into the mechanical stability of metallic crystals, with potential applications in materials science and engineering
The Cost Of Student Mandatory Fees: An Examination Of The Longitudinal Growth In Student Mandatory Fees At Four-Year Public Universities In Texas And Their Impact On Student Retention Rates
Get PDFThe ever-increasing costs and debt incurred by US college students is a hotly contested issue. In March 2022, the Texas Higher Education Coordinating Board (THECB) released a refreshed strategic plan for the stateâ??s higher education: Building a Talent Strong Texas. The refreshed plan concentrated on access for minority populations, enhanced student completion goals, and expanded the focus on reducing student debt. Texas set out to lead the nation in the least college student debt reported. One of the least examined or understood college costs is student mandatory fees (Arnott, 2012; Black & Taylor, 2018; Kelchen, 2016; Reinagel & Cooper, 2020). This study sought to examine the rising costs associated with student mandatory fees at four-year public institutions in Texas. The quantitative study used six years of publicly available national panel data to determine a) by what magnitude required fees were increasing, b) whether fees were becoming an increasing proportion of the price of attendance (PoA) for in-state and out-of-state students living off campus without family, and c) to examine the relationship between student fees and institutional fall-to-fall retention rates. Findings included a 591 mean average increase (24%) out-of-state fees at public, four-institutions in Texas (n=32). Despite increases over the six years, fees did not represent a greater proportion of the price of attendance reported. The study also found that rate term for both in-state and out-of-state fees did explain statistically significant variance in institutional student retention rates, but upon further examination no specific variables in the proposed models were significant. Institutional variability did account for over 90% of variance in the proposed model which has implications for the THECB to intervene around institutional flexibility in determining student fees as a component of higher education costs
Risk And Protective Factors Associated With The Relationship Between Adverse Childhood Experiences And Alcohol Expectancies In Latina College Students
Get PDFAlcohol use among college students is a public health concern, with rates increasing in recent years. Several constructs have been studied in past research to assess alcohol use, alcohol consequences, and motives to drinking. However, to the authorâ??s knowledge, no study has assessed risk and protective factors that may influence the relationship between alcohol expectancies and Adverse Childhood Experiences (ACEs) among Latina college students living on the U.S/Mexico border. The present study assessed the relationship between ACEs and positive and negative alcohol expectancies, as well as the impact of risk and protective moderating factors on the relationship. Latina college students (N=341) were recruited from a Hispanic Serving Institution and completed an online survey which included: demographics, the Center for Youth Wellness Adverse Childhood Experience Questionnaire (CYW ACE-Q) Teen Self-Report, the Comprehensive Effects of Alcohol (CEOA) measure, the Children of Alcoholics Screening Test (CAST), the Depression, Anxiety, Stress Scale â?? 21 (DASS), The Family Health Scale -Long Form (FHS-LF), and the Brief-Resilience Scale (BRS). Descriptive analyses were conducted to yield participant characteristics. Hierarchal linear regressions were used to test for main and interactive effects. Results indicated a positive association between positive alcohol expectancies ( = .049, p \u3c.001) and negative alcohol expectancies ( = .049, p \u3c.001) with adverse childhood experiences. However, no moderators influenced the relationship between ACEs and positive and negative alcohol expectancies. Results of this study will inform alcohol prevention programs to target Latina college students, particularly those who have experienced childhood trauma
Working In The Shadows: The Impact Of Wage Theft Among Undocumented Workers In El Paso, Texas
Get PDFThe documentary film titled Working in the Shadows: The Impact of Wage Theft Among Undocumented Workers in El Paso, Texas sheds light on the pervasive issue of wage theft experienced by undocumented workers in the region. Through personal testimonies, interviews with workers, legal experts, and government officials, the film delves into the challenges faced by undocumented workers who are vulnerable to exploitation due to their legal status.Undocumented workers in El Paso face a host of challenges, including unpaid wages, unsafe working conditions, and fear of retaliation if they assert their rights. The film highlights the critical role of community organizations, legal experts, and law enforcement in addressing wage theft and advocating for the rights of undocumented workers. Additionally, the documentary emphasizes the importance of extending legal protections to all workers, regardless of their immigration status. Wage theft not only takes a financial toll on undocumented workers but also has significant social and psychological repercussions. The film explores the stigma, stress, and anxiety experienced by workers, who are pushed deeper into poverty by unscrupulous employers. By amplifying the voices and struggles of undocumented workers, the film aims to educate the public about the pervasive problem of wage theft and inspire empathy and understanding among viewers. Ultimately, Working in the Shadows serves as a powerful educational tool that encourages viewers to act against wage theft and support the rights of undocumented workers in El Paso and beyond. By shedding light on this often-overlooked issue, the documentary strives to inspire change, promote social justice, and advocate for fair labor practices for all workers, regardless of their legal status
Development Of A Digital Engineering Testing Framework For Cubesat Applications
Get PDFDigital Engineering (DE) is playing an important and expanded role in todayâ??s industry. As engineering systems become more and more complex with each new iteration, the need for a more efficient and agile methodology for project management and development is needed. The SleeperSat-1 (SPST-1) is a Modular Open System Architecture (MOSA) type of small satellite being developed by the UTEP Aerospace Center. The SPST-1 will mostly use digital engineering tools for its lifecycle research and development. CubeSats require rigorous environmental testing not only to ensure the success of the mission, but also to ensure the safety of the crew, space vehicle and other CubeSats stowed in the same deployer. The workflow and implementation of DE tools to develop a high-fidelity Digital Twin (DT) to test and validate results for CubeSats environmental testing are presented, as well as the design of a modular CubeSat chassis
Will Consumer-Generated Reviews and Electronic Word-of-Mouth Communications Affect Subjective Norm Perceptions, Attitudes Toward Social Commerce, and Social Shopping Intensions Among Gen Z Consumers?
Get PDFSocial commerce has become a global phenomenon in recent years. Its convenience and accessibility have revolutionized how consumers shop and interact with brands and merchants. Gen Z consumers make up the majority (55.5%) of social buyers, and they are likely to be influenced by consumer-generated reviews (CGRs) and electronic word-of-mouth (eWOM) on social media. This thesis draws on the Theory of Planned Behavior (TPB) and employs a quantitative online questionnaire to determine whether CGRs and eWOM influence subjective norms (SN) perceptions, attitudes toward social commerce (ASC), and social shopping intention (SSI) of Gen Z consumers. The theoretical framework also included three message dimensions of eWOM and CGRs (i.e., believability, credibility, and trust) as antecedents.The multiple regression results showed that credibility significantly predicts consumersâ?? SN. However, believability and trust did not influence the SN of consumers. After controlling the preceding variables, the multiple regression analysis found that SN is a positive and significant predictor of ASC, and ASC was also a positive and significant predictor of SSI. Discussions, implications, and future research directions were provided.
Keywords: Consumer-Generated Reviews (CGRs); Electronic Word-of-Mouth (eWOM); Gen Z Consumers; Regression Analysis; Social Commerce; Subjective Norms; Survey; Theory of Planned Behavior
High Pressure Boiling Enhancement Using Micro/nano Structures
No full textThe enhancement of boiling heat transfer is critical because it has the ability to solve thermal management issues that are seen across all engineering and manufacturing applications. The focus of this research is first to characterize the critical heat flux (CHF) on cylindrical surfaces during high pressure pool boiling where fundamental boiling parameters were characterized such as bubble diameter, bubble growth, wait time, and bubble departure frequency as well as an approximation for nucleation site density. The results were compared with 4 different models t in investigate if the pressure, engineered surface or other factor dictated the value of CHF.A custom-built heater was designed to test cylindrical samples under pool boiling capable to deliver radial heat flux to challenge all the engineering samples tested on pool boiling up to CHF. The active heating area on the cylindrical tubes had a dimension of 9.5 mm outer diameter and 10.5 mm length. A custom-built cylindrical heater was designed using a nichrome wire coil of 30 AWG with a resistance of 19.57 Ω/inch of coil to provide joule heating to the cylindrical tubes. The electrical wire was insulated from the copper heater using a thin layer of alumina paste. The research detailed here is based on the characterization of pool boiling heat transfer enhancement on cylindrical tubes with circumferential micro-channels, nanostructures, and hierarchical surfaces where they were compared with a cylindrical copper tube with smooth surface as reference using saturated water at different pressure conditions: 1 bar, 2 bar and 3 bar pressure. Three engineered copper tubes with circumferential microchannel dimensions of 300 μm, 600 μm, and 900 μm fin width and a fixed 400 μm channel width with 410 μm channel depth were machined using CNC. Additionally, nano-leaves CuO surface were fabricated on a plain copper tube copper to create nanostructures. Hierarchical surfaces were fabricated with the three circumferential microchannel of 300 μm, 600 μm, and 900 μm fin width and the same technic of CuO nano-leaves. The plain cylindrical copper tube reached a CHF value of 72 W/cm2 at 1 bar, 98 W/cm2 at 2 bar, and 120.5 W/cm2 at 3 bar pressure. The cylindrical tubes with circumferential microchannel geometries tested at atmospheric pressure reached a CHF value between 131-144 W/cm2, which corresponds to 82% to 100% enhancement compared to the plain cylindrical tube at 1 bar. CHF on cylindrical tubes with circumferential microchannel reached values in the range of 172 -185 W/cm2 at 2 bar pressure and for 3 bar pressure CHF values in the range of 193 â?? 201 W/cm2 where all these values of CHF represent an enhancement over 100%. The nanostructure reached 110.22 W/cm2 that corresponds to 53% enhancement compared with plain cylindrical tube. The nanostructured tube reached CHF of 125.28 W/cm2 that corresponds to 27.8% enhancement compared with plain cylindrical tube at 2 bar and 74% enhancement compared with plain cylindrical tube at atmospheric pressure. Nanostructure tube reached CHF of 145 W/cm2 at a wall superheat of 17.23 with a HTC of 86 kW/m2K. The hierarchical tubes were tested at atmospheric pressure, 2 bar and 3 bar where they reached a CHF value between 133-151 W/cm2, 175-194 W/cm2, and 217-235 W/cm2 for atmospheric, 2 bar and 3 bar pressure, respectively. Also, a flow boiling setup was developed to work at a range of atmospheric to 10 bar pressure at a volumetric flow rate of 1000 kg/m2s and between a temperature range of ambient temperature to 180 °C. To validate the setup a test was performed at 10 K subcooled with distilled water and titanium that was deposited with a sputtering on an infrared radiation transparent flat sapphire. Flat heaters were built on a substrate of optical grade sapphire, where the heater consists of a substrate of sapphire with dimensions of 20 Ã? 20 mm2 with 1 mm thickness. A thin layer of 20 nm of ITO is deposited by thermal evaporation that works as the Joule heating element, and gold pads around the ends of the sapphire are deposited for electrical connection as well as definition of the tested area of 10 Ã? 10 mm2. The results obtained with water as working fluid were compared with literature data that showed a good similarity with the results for flow boiling under same conditions. 10 K infrared thermometry was used during 10 K subcooled flow boiling and pool boiling with FC-72 at atmospheric pressure and 4 bar to capture fundamental boiling parameters such as bubble departure diameter, bubble growth time as well as wall superheat and heat flux. An initial calibration test has been performed for the infrared camera. The flow boiling tests will be performed at atmospheric pressure under a mass flux of 1000 kg/m2s with a hydraulic diameter of 1.5 cm. The high-speed infrared thermometry technique will measure the local time-dependent 2-D temperature and heat flux distribution on the boiling surface. However, the bubble side and departure time of the bubbles on FC-72 did not allow us to obtain the fundamental boiling parameters. On the other hand, boiling curves were obtained for pool and flow boiling at atmospheric and 4 bar pressure with a subcooled of 10 K
Feasibility Study For The Detection Of Damage To Composite Overwrapped Pressure Vessels With Phase Array Ultrasonic Testing
Get PDFWhen discussing the field of Nondestructive Examination, there are various techniques and instrumentation that can be utilized for analysis of components. However, with newer technology and the development of newer forms of technique, it is critical to explore exactly how these can be applied. This work will aim to explore one newer technique, Phased Array Ultrasonic Testing, and determine the viability of its use for examining Composite Overwrapped Pressure Vessels (COPVs). Currently, the types of vessels have been used in a variety of ways such as in transportation vehicles. More notably, these vessels are used in aerospace applications hence the importance of inspecting these components before use. A development of a test plan was utilized to provide a guide to obtain results that could be comparable to those already collected by established techniques such as ultrasonic testing, shearography, acoustic emission, etc. The test plan was created to be able to be system independent and identifies key test parameters such as probes, frequency, imaging modes, and suggestions for future work