Theses/Dissertations - Mechanical Engineering
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Item A method for replicating ice accretion roughness using multi-scale analog distributions.(2018-03-23) Clemenson, John-Mark, 1994-; McClain, Stephen Taylor.A new approach of creating an analog surface for a surface with natural roughness is presented based on the hypothesis that the dominant skin friction and heat transfer augmentation mechanisms are 1) the vortex shedding from the roughness elements and 2) the interaction of the shed vortices with the next downstream roughness elements. An autocorrelation function was employed on a real ice surface to capture the root-mean-square-roughness height, the primary streamwise wavelength, and the aspect ratio of surface microscales. Two distributions of deterministic roughness, one of ellipsoids and one of elliptical cones, were created to match the primary features of the real ice surface. This work describes the analog surface creation method and characterizes the convective enhancement and velocity boundary layer development of the analog surfaces. The convective enhancement and velocity boundary layer results associated with the analog surfaces are then compared to those of the real ice surface.Item A photogrammetric method for measuring transient frost surface roughness.(2018-11-26) Miyauchi, Taber Scott, 1994-; McClain, Stephen Taylor.Cold-soaked fuel frost (CSFF) is a form of aircraft wing contamination that results in aerodynamic degradation. Unless a certification exemption for a specific aircraft model is provided by the FAA, an operator of an aircraft is not allowed to takeoff with CSFF on aircraft wing surfaces. To assist manufacturers in the design of air vehicles and to assist the FAA in evaluating exemption requests, frost roughness evolution must be characterized and modeled. However measuring transient frost roughness is difficult because of the optical and material properties of frost. This experimental investigation presents a nonintrusive, in-situ method of measuring frost roughness using structure-from-motion photogrammetry. This method was validated with fabricated rough surfaces and was used on a closed-loop psychrometric wind tunnel that is capable of producing frost formations in various environmental conditions. The resulting roughness parameters and detailed height distributions were analyzed to determine the effects of each environmental variable.Item A Study of chemical treatments and processing for banana fiber-reinforced LDPE composites.(2016-07-25) Chester, Patrick, 1991-; Jordan, William Mark, 1950-Natural fiber-reinforced polymeric composites have been gaining popularity due to their low weight and high sustainability potential. Banana pseudo-stem fibers in particular present a unique opportunity for reinforcement since they are widely grown and are currently considered an agricultural waste product. However, poor bonding between the hydrophilic fiber and a comparatively hydrophobic thermoplastic matrix, such as LDPE, have limited composite properties. This study looks at two known natural fiber treatments designed to promote interfacial bonding, peroxide and permanganate treatment, and documents their effect on banana pseudo-stem fibers and a banana fiber/LDPE injection molded composite. It was found that peroxide treatment enhances the strength of individual fibers but is thermally unstable. Permanganate treatment decreases the moisture absorption of the fibers and improves interfacial bonding but provides no advantage over untreated fibers in composite properties. This study also looks into special processing considerations for injection molding natural fiber composite parts.Item A study of frost growth and roughness on a cold flat plate under forced convection.(2020-03-19) Zhang, Tongxin, 1987-; O'Neal, Dennis.The growth and roughness of frost formed on a cold flat plate under forced convection was characterized through experimental observations and analysis. The results indicated that the evolution of frost roughness was mainly determined by the complex structures of frost crystals appearing on the top of the frost layer. The frost crystal type, frost crystal size, and frost crystal distribution were strongly affected by environmental conditions and collectively determined the formation of frost surface roughness. Frost roughness parameters, including frost root-mean-square height and frost surface skewness, were measured by utilizing a 3-D photogrammetric method. The growth of frost roughness under various environmental conditions were then assessed. Both frost root-mean-square height and surface skewness increased with time until reaching a maximum value (up to 0.69 mm and 2.34, respectively), before starting to decrease. The frost surface skewness peak, the maximum frost root-mean-square height, and the time for the appearance of frost root-mean-square height typically varied linearly with the surrounding environmental conditions. The experimental investigation also showed that frost roughness varied over both time and location on the test surfaces. The frost equivalent sand-grain roughness height, calculated by using the frost root-mean-square height and frost surface skewness, was applied to represent the unevenness of frost roughness on cold substrates. Through an ANOVA test on the data of the frost equivalent sand-grain roughness height, air humidity and air temperature with p-values less than 0.05 were indicated to be the key factors determining the changes in the variation of the frost roughness in space. Empirical correlations were developed to describe the relationships between the appearance of the frost roughness peak and environmental conditions. Finally, based on the frost roughness data collected in this study, a predictive model of frost roughness parameters, including frost root-mean-square height, frost surface skewness, and frost equivalent sand-grain roughness height, was established with the R-square values of 0.57, 0.65, and 0.53, respectively.Item Aerodynamic and aeroacoustic design considerations for small-scale, fixed-pitch, horizontal-axis wind turbines operating at low reynolds numbers.(2017-03-22) Hays, Andrew W., 1993-; Van Treuren, Kenneth W.Renewable energy is needed now more than ever to meet demands as conventional energy sources are being depleted. Wind energy has the potential to provide a substantial amount of renewable energy. Of increasing interest is the development of small wind turbines for residential and urban applications. In these settings, a new concern is the noise that these turbines produce due to their operation at higher rotational speeds. Experimental noise data for the NREL S823, Eppler 387, NACA 4412 and NACA 0012 2D airfoils were taken for Reynolds number from 50,000 to 200,000. From these studies, trends based upon airfoil shape were gathered and used in choosing a new airfoil for testing a new rotor design. From these trends, two new airfoils were chosen to compare to the baseline rotor that utilized the S823 airfoil. The two new rotors, each utilizing the Eppler 216 and SD 7062 airfoils, showed an increase of power production from 5-60%. These rotors were also able to decrease the generated noise by up to 9.5 dB(A).Item Aerodynamic and aeroacoustic design of small unmanned aircraft system propellers at low Reynolds numbers.(2020-11-19) Sanchez, Ricardo D., 1996-; Van Treuren, Kenneth W.The Small Unmanned Aircraft System (sUAS) has become an overwhelmingly important asset for military intelligence, surveillance, and reconnaissance in addition to a multitude of needs in the commercial industry. More research should investigate sUAS propulsion systems and specifically the propellers, largely responsible for noise generation and inefficiencies in power consumption at low Reynolds numbers. Experimental noise data compared stock, modified, and five bladed propellers reducing tip vortex strength and noise generation. Results showed measurable far field sound decay and five bladed noise reductions of 5 dBA. Three motors compared propeller power consumption and resulted in increased electrical efficiencies of 14.5% and 31.3%. An airfoil study showed the GOE358 as the most aerodynamically efficient airfoil tested. A Prandtl bell-shaped lift distribution, minimum induced loss design, was applied to a propeller resulting in decreased power consumption and improved electrical efficiency by 18.51% with a SPL reduction of 11.15 dBA compared against the Baseline propeller. The Baseline propeller used an industry standard minimum loss propeller design.Item Aerodynamic design considerations for small-scale, fixed-pitch, horizontal-axis wind turbines operating in class 2 winds.(2012-08-08) Burdett, Timothy A.; Van Treuren, Kenneth W.; Engineering.; Baylor University. Dept. of Mechanical Engineering.Renewable sources of energy, such as wind, are necessary to meet the growing demand as conventional energy sources are depleted. Very little research has been accomplished to improve wind turbine performance in Class 2 winds. This work experimentally analyzed techniques to improve the aerodynamic performance of small-scale, fixed-pitch, horizontal-axis wind turbines in Class 2 winds. Experimental data for the S823 airfoil was taken for Reynolds numbers from 50,000 to 200,000. A trip strip was shown to improve airfoil performance for Reynolds numbers below 100,000. Additional wind tunnel studies validated the wind turbine testing procedure. Using blade element theory (BET) and blade element momentum theory (BEMT), wind turbine blades with optimum angle of twist were designed and tested. Results suggest the BEMT-optimized blades will perform better at the design point. The sensitivity of the design angle on power production was also examined, resulting in negligible difference for the conditions tested.Item An anisotropic topology optimization method for carbon fiber-reinforced Fused Filament Fabrication.(2016-07-26) Hoglund, Robert M., 1992-; Smith, Douglas E., 1962-Topology optimization has become an increasingly important field in materials engineering for determining optimal material distribution given certain loading conditions. As the desire for stronger, lightweight structural parts grows as well as the influence of additive manufacturing in the composites industry, there is a need for determining optimal structural orientation of Fused Filament Fabrication (FFF)-produced parts, especially those that have been improved with the addition of carbon fiber to the polymer feedstock. In this work, variations of the Solid Isotropic Material with Penalization (SIMP) method for topology optimization are proposed and modified, using the Adjoint Variable Method for design sensitivity analysis, a sensitivity filter to prevent checkerboarding, and a transversely isotropic material model. Using this technique, optimizations are performed for varying x- and y- direction orientation, as well as a variable material angle. Tested FFF-produced samples show agreement with computational results.Item An investigation into the electrical, optical, and microstructural effects of aluminum-doping amorphous indium zinc oxide via ultra-high vacuum co-sputter deposition.(2019-04-24) Reed, Austin Spencer, 1994-; Yokochi, Alexandre F.T.Indium Zinc Oxide (IZO) has emerged as a high-potential material candidate for electronic applications involving novel flexible and transparent devices. IZO’s rapid growth can be attributed to its high carrier mobility (~40-50 cm2/Vs), room-temperature fabrication, superb transparency (>85%), and semi-/conducting capabilities [13, 14]. While IZO’s characteristically high carrier density (~1020 cm-3) has prevented immediate application as a semiconductor [15, 18], strategies to lower the carrier density into the semiconducting range have emerged (<1017 cm-3) [1,8,18]. Recently, novel doping techniques have demonstrated success in deterring IZO’s carrier generation while maintaining both its microstructural and optoelectrical properties. This study investigates the effects of doping IZO thin films with Al3+ via ultra-high vacuum co-sputter deposition. Films were fabricated at room-temperature (~25oC) implementing direct-current and radio-frequency power sources for IZO and Al3+, respectively. An effective carrier suppression of ~103 cm-3 at RF-25W was observed, as well as the enhancement of amorphous-phase stability via Al3+-inclusion in IZO.Item Analytic modeling and applications of barotropic flows over sloping topographies using similarity solutions.(2017-03-31) Ibanez Amador, Ruy, 1991-; Kuehl, Joseph.The continental slope is a region in the ocean that consists of a strong sloping topography. The slope acts as a barrier to large scale geophysical transport, but small scale mechanisms are not well understood. Studies are mostly limited to large scale simulations and spatially limited field measurements. I developed an analytic method to obtain a base flow field for regions of the continental slope. Using scaling arguments, I reduce the system to the leading order dynamical balances and apply a similarity method to find solutions of the flow. It is possible to retain the nonlinear terms for a special case, which provides insight into the base nonlinear dynamics of the flow. I show that the solutions are relevant to regions of the continental slope using bathymetry data from the National Oceanic and Atmospheric Administration.Item Annual energy use of series and parallel fan powered terminal units.(2017-12-06) Lu, Di, 1993-; O'Neal, Dennis.Traditional mass and energy balance component models of fixed and variable airflow series and parallel fan powered terminal units (FPTUs) were used to estimate the annual energy use in a small office building with hourly loads for five cities generated from EnergyPlus. Fixed airflow series and parallel fan powered terminal units with permanent split capacitor motors were assumed to be the baseline in each city. All variable airflow FPTUs utilized electronically commutated motors. Sizing effects of the variable airflow FPTUs were evaluated by examining the use of the capacity factors. Variable airflow series units showed 10% reduction in total energy use compared to fixed airflow series FPTUs. Variable airflow parallel FPTUs showed little energy savings compared to their fixed airflow counterparts. Energy analysis was also performed on two approaches for controlling the cooling operations of variable airflow series units and impact of leakage on the performance of parallel FPTUs.Item Applications of the wavelet synchrosqueezed transform for ultrasonic inspections : quantifying layer height and visualizing missing extrudates in material extrusion printed samples and visualizing wrinkles in carbon fiber laminates.(May 2023) Battershell, Luke William, 1998-; Jack, David Abram, 1977-In the aerospace industry there is a push to find uses for additively manufactured components with the goal of taking advantage of the increased freedom of design that it allows. Material extrusion, specifically fused filament fabrication (FFF), is one of the most prevalent methods for additive manufacturing currently used in industry. Currently the main use of additive manufacturing in the aerospace industry is for use in rapid prototyping. To move from that to functional use, additively manufactured components need to be inspectable. This thesis aims to improve existing inspection methods for material extrusion printed components by introducing the use of the wavelet synchrosqueezed transform (WSST) in the analysis of ultrasonic testing (UT) inspection data. The proposed method uses the WSST to quantify layer height and visualize missing extrudate. The method for quantifying layer height was extended to the visualization of wrinkles in carbon fiber laminates which are commonly used in the aerospace industry.Item Applying mass and energy balances to model series and parallel fan-powered terminal units.(2015-07-31) Reid, Carl L., 1989-; O'Neal, Dennis.Performance data from four manufacturers of fan-powered terminal units was analyzed and simple models of the fan/motor power use developed. These data included two fan motors: permanent split capacitor motors with silicon controlled rectifier control and electronically commutated motors. Fan sizes ranged from approximately 250 to 3500 ft³/min (0.118 to 1.65 m³/s) and motor sizes ranged from one-third to one hp (248.6 to 745.7 W). A mass and energy balance component approach was used to estimate the annual heating, cooling, and fan energy use of a five zone small office building that utilized a variable air volume system with fan-powered terminal units. Results were then compared to published results that used a systems approach to model fan-powered terminal units. Comparisons were made for five cities (Houston, New York, San Francisco, Chicago, and Phoenix). The two modeling approaches produced results that were within six percent of each other.Item Assessing precision and application of marker placement device to enhance motion capture studies.(2020-11-13) Whiddon, Forrest J., 1994-; Rylander, Jonathan.Motion capture has become an important clinical tool used in applications of therapy and treatment plans as well as surgical evaluations. However, due to factors such as human error, having multiple examiners, and using multiple days, there is an inherent presence of error within clinical motion capture due to marker replacement. The objective of this study was to develop and evaluate a device that increases the precision of repeatedly placing motion capture markers on a subject for between-day and between-examiner situations. Each mechanical component of the device, as well as body positioning and marker placement repeatability, was evaluated for differences that compounded throughout the process. Kinematic trials were executed to indicate the significance of the device in application. The results showed that the device performed superiorly to human marking of all levels, producing maximum difference measurements of <8.08 mm and minimal measurements resulting in significant kinematic change.Item Assessment of shaped film cooling holes at high density ratios for gas turbine cooling using S-PIV and PSP.(2016-02-27) Watson, Travis B., 1992-; Wright, Lesley Mae.During film-hole cooling, relatively cold air is extracted from the compressor of a gas turbine engine and forced through the turbine airfoils in order to lower their surface temperatures. To investigate the effects of various film cooling hole geometries on film-cooling hole performance, shaped film cooling holes are observed using Stereo-Particle Image Velocimetry (S-PIV). Experiments are performed at various locations where the coolant-to-mainstream interaction is captured using multiple density ratios and blowing ratios. Using S-PIV the three-dimensional flow field is measured and coupled with surface film-cooling effectiveness measurements obtained through a pressure sensitive paint (PSP) technique. Flow vorticity distributions are derived from velocity measurements. Results clearly show that film cooling is enhanced by dispersing coolant from racetrack shaped inlets and incorporating anti-vortex designs within a laidback, fanshaped hole.Item Can changing running shoes immediately reduce the risk of tibial stress fractures?(2018-04-23) Tavares, Jennifer E., 1990-; Rylander, Jonathan.Running is becoming a more popular sport worldwide however many runners suffer from tibial stress fractures (TSF). While there are various kinematic, kinetic, and anthropometric risk factors associated with TSF, it is though that by changing running shoes one or several of these risk factors will decrease. This thesis is focused on the kinetics, kinematics, and muscle activation patterns of commercially available shoes as they affect known risk factors for TSF. Five different running conditions (barefoot, minimalist, maximalist, neutral, and stability shoes) were analyzed in this study. The test protocol utilized 3D motion capture, force plates, and EMG. The findings of the current study suggest that strike pattern and foot alignment rather than shoes are the determining factors in eliminating risk factors for TSF. Future works should involve fatigue studies and gait retraining studies to determine the best shoe for long term reduction of TSF risk.Item Characterization of fan coils units with electrically commutated motors.(2019-08-05) Cramer, Jessica, 1993-; O'Neal, Dennis.The data from five manufacturers were obtained for the purpose of developing of a method for generalizing fan coil units (FCUs) with electronically commutated motors (ECMs. In addition, the University of Louisiana at Lafayette (ULL) provided data for 40 more units. Three methods were tested for levels of variation in results and consistency between various types of ECM FCUs. First, units were analyzed by their fan efficacy: The Fan Efficacy Method, the Constant ESP method, and finally, the System ESP method. The success of the constant ESP method proved overall indifferent to variations between different ECM FCUs such as ESP, horizontal versus vertical, manufacturer, setting, and motor size. This model was capable of producing airflow and power versus ESP curves at a given setting, using only the design airflow and ESP.Item Characterization of sub-surface wrinkles within a laminated composite using a novel phased array ultrasonic scanning technique incorporating a portable nozzle and robotic arm.(May 2023) Khan, Irrtisum, 1993-; Jack, David Abram, 1977-Due to their superior strength to weight ratio as compared to metals, the use of laminated composites is growing in the aerospace, automotive and energy sectors. This increased performance is severely compromised by the presence of out-of-plane wrinkles, a manufacturing defect that occurs in thick complex curvature composite stacks. This thesis presents an ultrasound scanning technique utilizing a novel phased array approach to detect out-of-plane wrinkles and, unlike previous literature results, quantify wrinkle dimensions. Multiple nozzle designs are provided for phased array probes to improve portability and scanning setup. A robotic system is presented that incorporates the novel scanning technique, which allows inspection of parts with non-planar geometries. The measured quantities are validated using 𝜇-CT scans, and results are provided that show average relative errors of 8.33%, 22.79% and 9.72% for, respectively, wrinkle height, width, and intensity corresponding to an average absolute error of, respectively, 0.057mm, 1.59mm and 4.7 × 10−3 .Item Characterization of the internal temperature and phase state of amorphous materials using ultrasonic non-destructive evaluation.(2019-08-07) Jeffrey, Taylor Danielle, 1991-; Jack, David Abram, 1977-Ultrasound has a wide range of applicability and is used across many industries for non-destructive evaluation. Temperature is one of the key parameters in thermodynamic systems, and ultrasound has been studied as a means of temperature measurement for many years. Polymer, petro-chemical, power plant, food processing, and composites are just some of the industries which already make use of ultrasonics and stand to benefit from advances in the understanding and technology surrounding ultrasonic testing and evaluation. This research uses an amorphous wax with a low coefficient of thermal expansion; it is highly attenuative, and that attenuation change is a function of the temperature of the wax. The results of this research demonstrate the ability of this method to approximate 2D planar temperature and phase behavior of the wax using only ultrasonic data and externally located thermocouples, making it a truly non-invasive method.Item Characterizing hip motion during activities of daily living.(2017-07-27) Fuller, Carley E., 1993-; Rylander, Jonathan.In the United States alone, 332,000 people received a total hip replacement (THR) each year [1 – need to reattach ref]. Following a total hip arthroplasty, doctors get asked by their patients if they can still do particular activities. There is not enough information out there for them to confidently answer their patients. Additionally, their patients’ questions stem for fear of dislocating. Hip dislocation occurs in between 2% and 11% of patients and is estimated to cost at least $75 million per year [2 from Hip Char protocol]. Therefore, the purpose of this study is to explore activities of daily living (ADLs) that can cause hip dislocation in THA patients so that clinicians can give better instructions to patients and improve post-op rehabilitation strategies following surgery. Our goal is to quantify the movement strategies employed (by healthy persons) to complete these common tasks and identify the motions that can make a person more vulnerable to hip dislocation.