Mechanical Engineering Commons^™

Design And Validation Of An Experimental Setup To Study Single Phase Heat Transfer Enhancement Of Femtosecond Laser Processed Metallic Surfaces, Sarah Jane Wallis

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

In the present work, a single phase flow heat transfer experimental loop was designed with the intention of studying the effects of femtosecond laser surface processing (FLSP) on metallic surfaces with the specific goal of enhancing heat transfer in compact heat exchangers currently in use by NASA. This experimental setup went through two major design iterations which are detailed in this thesis. The first iteration consisted of a counterflow fluid-to-fluid heat exchanger, which measured overall heat transfer coefficients and pressure drops, where the overall heat transfer coefficient is defined in terms of the total thermal resistance to heat transfer between …

Temporal Transformation Of Barrier Islands A Round Nakdong Estuary, Sukzun Youn

Theses and Dissertations

The Nakdong Estuary system near Busan, South Korea consists of dynamic shorelines characterized by morphological transformations that result from both natural disasters (typhoons and flooding) and construction projects (Nakdong Estuary Dam, gates in the West Nakdong River and Busan New-ports). This study aims to synthesize existing data for tides, waves, bathymetry and meteorological data obtained from a variety of institutions with the objectives of (1) identifying and ranking major factors that influence morphological transformations and (2) determining how these factors influence morphological change over time. These objectives were met by analyzing patterns of flow and sediment transport using Center Point …

The Influence Of Varying Fiber Stacking Sequence On The Tensile, Impact, And Water Absorption Properties Of Unidirectional Flax/E-Glass Fiber Reinforced Epoxy Composite, Mohammed F. Al-Edhari

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This thesis includes the study of the mechanical performance of two different types of fibers reinforced hybrid composites. Two kinds of fibers, natural fiber (flax) and synthetic fiber (E-glass), are used to reinforce epoxy resin. To evaluate the effective properties of the hybrid composites, a micromechanical analysis of the structure genome (SG) of a unidirectional fiber hybrid composites is performed using nite element analysis (FEA). Both fibers are assumed to be circular and packed in a hexagonal pattern. The effects of varying volume fractions and fiber locations, of the two fibers, on the elastic properties of the hybrid composites are …

The Effects Of Exhaust Vent Location On Thermal Comfort Inside The Residential Buildings Equipped With An Evaporative Cooling System, Armin Saraei

UNLV Theses, Dissertations, Professional Papers, and Capstones

Inlet and outlet conditions, Including size and location, have significant effects on the air distribution, temperature, humidity and thermal comfort in the buildings. In the current study, various strategies are presented for exhaust air vents and the effects of inlet and outlet vents locations are evaluated on providing thermal comfort in the residential and industrial buildings. To provide thermal comfort, three key factors need to be investigated based on ASHRAE standard 55- 2013 as follows: Comfort Zone, Thermal Sensation and Draft Rate. Flow distribution is studied as well in order to investigate the strategies, which make more vorticity in the …

Radiative Contour Mapping Using Uas Swarm, Zachary Cook

UNLV Theses, Dissertations, Professional Papers, and Capstones

The work is related to the simulation and design of small and medium scale unmanned aerial system (UAS), and its implementation for radiation measurement and contour mapping with onboard radiation sensors. The compact high-resolution CZT sensors were integrated to UAS platforms as the plug-and-play components using Robot Operation System. The onboard data analysis provides time and position-stamped intensities of gamma-ray peaks for each sensor that are used as the input data for the swarm flight control algorithm. In this work, a UAS swarm is implemented for radiation measurement and contour mapping. The swarm of UAS has advantages over a single …

Numerical Characterization Of The Flow Field And Heat Transfer Inside The Receiver Of A Parabolic Trough Solar Collector Carrying Supercritical Co2, Samad Gharehdaghimollahajloo

UNLV Theses, Dissertations, Professional Papers, and Capstones

The aim of this research is to provide a detailed numerical analysis of flow field and heat transfer inside the heat collecting element of a parabolic trough collector. The parabolic trough collector is used as the boiler in a direct Super Critical Carbon Dioxide (S-CO2) Brayton cycle.

A single collector is modeled and analyzed with different inlet conditions. The working fluid is supercritical since its pressure is increased to above critical pressure in the compressor while its temperature reaches 300 °C after passing through the recuperators and before entering the solar field. For the first time, this research considers both …

Theoretical And Experimental Investigation On The Multiple Shape Memory Ionic Polymer-Metal Composite Actuator, Qi Shen

UNLV Theses, Dissertations, Professional Papers, and Capstones

Development of biomimetic actuators has been an essential motivation in the study of smart materials. However, few materials are capable of controlling complex twisting and bending deformations simultaneously or separately using a dynamic control system. The ionic polymer-metal composite (IPMC) is an emerging smart material in actuation and sensing applications, such as biomimetic robotics, advanced medical devices and human affinity applications. Here, we report a Multiple Shape Memory Ionic Polymer-Metal Composite (MSM-IPMC) actuator having multiple-shape memory effect, and is able to perform complex motion by two external inputs, electrical and thermal. Prior to the development of this type of actuator, …

Trading Off Sound Pressure Level And Average Power Production For Wind Farm Layout Optimization, Eric Tingey, Andrew Ning

Faculty Publications

This research explores the trade-offs between a wind farm’s average power production and noise impact on nearby observers. Two specific wind farm designs were studied and optimized using the FLORIS wake model and an acoustic model based on semi-empirical turbine noise calculations. It was found in the two wind farms that the average power production could be increased, up to 8.01% in one and 3.63% in the other, ignoring sound level considerations. Including a noise restriction in the optimization had a minimal impact on the optimal average power production within about a five-decibel range. Past this range, sound limitations decreased …

Fuel Performance Modeling Of Reactivity-Initiated Accidents Using The Bison Code, Charles Pearson Folsom

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The Fukushima Daiichi nuclear accidents in 2011 sparked considerable interest in the U.S. to develop new nuclear fuel with enhanced accident tolerance. Throughout the development of these new fuel concepts they will be extensively modeled using specialized computer codes and experimentally tested for a variety of different postulated accident scenarios. One accident scenario of interest, reactivity-initiated accident, is a nuclear reactor event involving a sudden increase in fission rate that causes a rapid increase in reactor power and temperature of the fuel which can lead to the failure of the fuel rods and are lease of radioactive material. The focus …

Aerodynamic Centers Of Arbitrary Airfoils, Orrin Dean Pope

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The study of designing stable aircraft has been widespread and ongoing since the early days of Orville and Wilbur Wright and their famous Wright Flyer airplane. All aircraft as they fly through the air are subject to minor changes in the forces acting on them. The field of aircraft stability seeks to understand and predict how aircraft will respond to these changes in forces and to design aircraft such that when these forces change the aircraft remains stable. The mathematical equations used to predict aircraft stability rely on knowledge of the location of the aerodynamic center, the point through which …

Water Surface Impact And Ricochet Of Deformable Elastomeric Spheres, Randy Craig Hurd

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Soft and deformable silicone rubber spheres ricochet from a water surface when rigid spheres and disks (or skipping stones) cannot. This dissertation investigates why these objects are able to skip so successfully. High speed cameras allow us to see that these unique spheres deform significantly as they impact the water surface, flattening into pancake-like shapes with greater area. Though the water entry behavior of deformable spheres deviates from that of rigid spheres, our research shows that if this deformation is accounted for, their behavior can be predicted from previously established methods. Soft spheres skip more easily because they deform significantly …

Blanking Clearance And Punch Velocity Effects On The Sheared Edge Characteristic In Micro-Blanking Of Commercially Pure Copper Sheet, Didin Zakariya Lubis, Ichsan Ristiawan

Journal of Mechanical Engineering Science and Technology (JMEST)

This study aims to identify the influences between clearance and punch velocity on the part edge quality of blanked parts. Experiments have been conducted using material copper, punch-die clearance and punch velocity variations. In order to determine the reachable punch-die clearance and punch velocity required for blanking. The quality of the part-edge characteristics shows that higher punch velocity and decreases clearance value can improve the part-edge quality, resulting in smaller burr height and rollover, and a larger shear zone. Furthermore, it could be observed that the part-edge quality improvement when blanking with high punch velocity is much more distinct for …

Formula Of Moulding Sand, Bentonite And Portland Cement To Improve The Quality Of Al-Si Cast Alloy, Andoko Andoko, Poppy Puspitasari, Avita Ayu Permanasari, Didin Zakaria Lubis

Journal of Mechanical Engineering Science and Technology (JMEST)

A binder is any material used to strengthen the bonding of moulding sand grains. The primary function of the binder is to hold the moulding sand and other materialstogether to produce high-quality casts. In this study, there were four binder compositions being tested, i.e. 5% bentonite + 5% Portland cement, 4% bentonite + 6% Portland cement, 6% bentonite + 4% Portland cement, and 7% bentonite + 3% Portland cement. Each specimen was measured for its compressive strength, shear strength, tensile strength and permeability. The highest compressive strength was obtained fromthe specimen composed of 6% bentonite+ 4% Portland cement. The highest …

Modeling Of Antenna For Deep Target Hydrocarbon Exploration, Nadeem Nasir, Noorhana Yahya, Hasnah Mohd Zaid, Afza Shafie, Norhisham Hamid

Journal of Mechanical Engineering Science and Technology (JMEST)

Nowadays control source electromagnetic method is used for offshore hydrocarbon exploration. Hydrocarbon detection in sea bed logging (SBL) is a very challenging task for deep target hydrocarbon reservoir. Response of electromagnetic (EM) field from marine environment is very low and it is very difficult to predict deep target reservoir below 2km from the sea floor. This work premise deals with modeling of new antenna for deep water deep target hydrocarbon exploration. Conventional and new EM antennas at 0.125Hz frequency are used in modeling for the detection of deep target hydrocarbon reservoir. The proposed area of the seabed model (40km ´ …

Properties Of Brass Under Different Pouring Temperatures In Sand Casting Process, Poppy Puspitasari, Avita Ayu Permanasari, Andoko Andoko, Bayu Angga Pratama

Journal of Mechanical Engineering Science and Technology (JMEST)

This study aimed to determine the toughness of casts produced by the sand casting process at various temperatures against brass, and to investigate the structure contained in the cast madeusing abrass metal mould. This study was experimental research that observed the results of a treatment applied to a specimen group. This pre-experimental study usedthe one-shot case study model in which a group of samples was given treatment. The results showed that the specimen poured at 900°C exhibiteda microstructure consisting ofgood Cu-Zn content, while that at 700°Chad the least Cu content. It indicates that the higher the temperature used for metal …

Development Of A Ferrite-Based Electromagnetic Wave Detector, Muhammad Hanis Bin Zakariah, Poppy Puspitasari, Nur Azliza Ahmad

Journal of Mechanical Engineering Science and Technology (JMEST)

Direct detection of hydrocarbon by an active source using electromagnetic (EM) wave termed Sea Bed Logging (SBL) has shown very promising results. However, currently available electromagnetic wave technology has a number of challenges including sensitivity and lapsed time. Our initial response to this issue is to develop a ferrite-based EM wave detector for Sea Bed Logging (SBL). Ferrite bar and copper rings in various diameters were used as detector 1 (D1). For Detector 2 (D2), toroid added with copper wires in different lengths at the centre of it were used. The first experiment is to determine the inductance and resistance …

Thermogravimetric And Kinetic Analysis Of Cassava Starch Based Bioplastic, Nanang Eko Wahyuningtiyas, Heru Suryanto, Eddy Rudiyanto, Sukarni Sukarni, Poppy Puspitasari

Journal of Mechanical Engineering Science and Technology (JMEST)

Cassava starch based bioplasticfor packaging application has great potency because of the various starchproducing plants in Indonesia.Bioplasticcan contribute to reduce the dependence on fossil fuels andpetroleumthat can solve the environmentalproblem.Thepurpose of this research is to find out the thermal decomposition and the activation energy of cassava starch based bioplastic. The methods weresynthesis bioplastic with cassava starch as main component and glycerol as plasticizer. The thermogravimetry analysis was conducted to obtain the decomposition process mechanism of bioplastic and the heating valueof bioplasticwas measured using theadiabatic bomb calorimetric. Data analysis was conducted using a fitting model approach with an acikalin method to …

Compositional And Structural Evolution During Ball Milling Of Ti-Based Metallic Glass Powder, Yanuar Rohmat Aji Pradana

Journal of Mechanical Engineering Science and Technology (JMEST)

Ti42Zr40Ta3Si7.5Sn7.5metallic glass powder prepared for subsequent consolidation by hot pressing were produced by high energy ball milling from amorphous ribbon and both of the compositional and structural evolution on milled powders were studied using XRD and DSC analyses. By using WC vial and balls, the abrasion of milling media occurred causing WC contamination on < 105 µm milled powder after 2 cycles of milling. Based on DSC analysis, the contamination clearly reduced theΔTxof the alloy up to 48%. On the other hand, the contamination were overcome after milling using SS vial and balls, proved by no crystal peak observed on XRD pattern of all milling cycle levels. However, the thermal stability was noticed to be decreased implying the presence of nanocrystals on the amorphous powder after ball milling and the nanocrystal amount tend to be higher when more milling cycles were applied.

Ensemble Machine Learning And Forecasting Can Achieve 99% Uptime For Rural Handpumps, Daniel L. Wilson, Jeremy R. Coyle, Evan A. Thomas

Mechanical and Materials Engineering Faculty Publications and Presentations

Broken water pumps continue to impede efforts to deliver clean and economically-viable water to the global poor. The literature has demonstrated that customers’ health benefits and willingness to pay for clean water are best realized when clean water infrastructure performs extremely well (>99% uptime). In this paper, we used sensor data from 42 Afridev-brand handpumps observed for 14 months in western Kenya to demonstrate how sensors and supervised ensemble machine learning could be used to increase total fleet uptime from a best-practices baseline of about 70% to >99%. We accomplish this increase in uptime by forecasting pump failures and …

Suspension-Driven Gravity Surges On Horizontal Surfaces: Effect Of The Initial Shape, ‪Nadim Zgheib, T. Bonometti, S. Balachandar

Mechanical Engineering Faculty Publications

We present results from highly resolved direct numerical simulations of canonical (axisymmetric and planar) and non-canonical (rectangular) configurations of horizontal suspension-driven gravity surges. We show that the dynamics along the initial minor and major axis of a rectangular release are roughly similar to that of a planar and axisymmetric current, respectively. However, contrary to expectation, we observe under certain conditions the final extent of the deposit from finite releases to surpass that from an equivalent planar current. This is attributed to a converging flow of the particle-laden mixture toward the initial minor axis, a behaviour that was previously reported for …

Transient Analysis Of Fracture Initiation In A Coupled Thermoelastic Solid, Louis Milton Brock

Mechanical Engineering Faculty Publications

An isotropic, thermoelastic solid is initially at rest at uniform (absolute) temperature, and contains a semi-infinite, plane crack. Application of in-plane and normal point forces to each face of the crack causes transient 3D growth. The related problem of discontinuities in temperature and displacement that exist on regions that exhibit dynamic similarity is first considered. Asymptotic expressions, whose inverses are valid near the crack edges for short times, are obtained in integral transform space. These lead to equations of the Wiener–Hopf type for the fracture problem. Analytical solutions are obtained and, upon inversion, subjected to a dynamic energy release rate …

Evolution Of The Pore Size Distribution In Sheared Binary Glasses, Nikolai V. Priezjev, Maxim A. Makeev

Mechanical and Materials Engineering Faculty Publications

Molecular dynamics simulations are carried out to investigate mechanical properties and porous structure of binary glasses subjected to steady shear. The model vitreous systems were prepared via thermal quench at constant volume to a temperature well below the glass transition. The quiescent samples are characterized by a relatively narrow pore size distribution whose mean size is larger at lower glass densities. We find that in the linear regime of deformation, the shear modulus is a strong function of porosity, and the individual pores become slightly stretched while their structural topology remains unaffected. By contrast, with further increasing strain, the shear …

Characterizing The Electromechanical Response Of Flexible Foam For Multifunctional Impact-Sensing Applications, Evan Troy Bird

Theses and Dissertations

Flexible foams have unique properties that make them well-suited to several engineering systems. They are often used in impact-related applications because of their superior energy absorption performance. Many multifunctional materials are also derived from flexible foams due to their high customizability, which allows them to satisfy a wide range of performance requirements. Though flexible foams have high potential in these and other classes of material applications, their success relies on the proper characterization of their complex behavior. This thesis promotes the application of flexible foams by characterizing their electromechanical response through both experimental and theoretical approaches. One study in this …

Optimal Design And Control Of An Electromechanical Transfemoral Prosthesis With Energy Regeneration, Farbod Rohani, Hanz Richter, Antonie J. Van Den Bogert

Mechanical Engineering Faculty Publications

In this paper, we present the design of an electromechanical above-knee active prosthesis with energy storage and regeneration. The system consists of geared knee and ankle motors, parallel springs for each motor, an ultracapacitor, and controllable four-quadrant power converters. The goal is to maximize the performance of the system by finding optimal controls and design parameters. A model of the system dynamics was developed, and used to solve a combined trajectory and design optimization problem. The objectives of the optimization were to minimize tracking error relative to human joint motions, as well as energy use. The optimization problem was solved …

Dns And Les Of Scalar Transfer Across An Air-Water Interface During Inception And Growth Of Langmuir Circulation, Amine Hafsi

USF Tampa Graduate Theses and Dissertations

Direct numerical simulations (DNS) of an initially quiescent coupled air-water interface driven by an air flow with free stream speed of 5 m/s have been conducted. The DNS solves a scalar advection-diffusion equation for dissolved gas (or scalar) concentration in order to determine the impact of the water-side turbulence on scalar (mass) transfer from the air side to the water side and subsequent vertical transport in the water column. Two simulations are compared: one with a freely deforming interface and a second one with a flat interface. In the first simulation, the deforming interface evolves in the form of gravity-capillary …

A Comparison Of Sensitivity Metrics For Two-Stage Ignition Behavior In Rapid Compression Machines, David Wilson, Casey Allen

Mechanical Engineering Faculty Research and Publications

A rapid compression machine (RCM) multi-zone model is used to simulate the ignition of primary reference fuel (PRF) mixtures that exhibit two-stage ignition behavior. Sensitivity coefficients for each reaction in the PRF mechanism are calculated from four different metrics: (1) first-stage energy release, (2) first-stage pressure rise, (3) first-stage ignition delay time, and (4) total ignition delay time. The sensitivity coefficients are used to provide four unique rankings, and the rankings are compared using Spearman’s rank correlation coefficient. Special emphasis is given to comparing the rankings based on first-stage energy release and total ignition delay time. The level of agreement …

Investigating Scalable Manufacturing Of High-Conductivity Wires And Coatings From Ultra-Long Carbon Nanotubes, Pouria Khanbolouki

Mechanical Engineering ETDs

Carbon nanotubes (CNTs) are a promising candidate for next generation of electrical wirings and electromagnetic interference (EMI) shielding materials due to their exceptional mechanical and electrical properties. Wires and coatings from ultralong nanotubes that are highly crystalline, well-aligned and densely packed can achieve this goal. High-performance CNT conductors will be relatively lightweight and resistant to harsh conditions and therefore can potentially replace current conductors in many industries including aerospace, automotive, gas and oil.

This thesis investigates a new manufacturing approach, based on conventional solution coating and wire drawing methods, to fabricate high conductivity wires and coatings from ultra-long carbon nanotubes. …

Effect Of Alignment, Sizing, And Manufacturing Method On Mechanical Properties Of Recycled Carbon Fiber Composites, Nekoda Van De Werken

Mechanical Engineering ETDs

The exceptional combination of properties offered by carbon fiber composites has propelled their incorporation into high performance markets such as aerospace, wind energy, luxury cars and sporting goods. While the use of carbon fiber in these sectors is expected to continue to increase, the high price and energy cost associated with carbon fiber production acts as a significant barrier of entry into larger volume markets, such as the automotive industry. One method of navigating this transition is through the use of recycled carbon fiber composites.

Carbon fiber reclamation can produce fibers with up to 90% and 100% of the strength …

Nonlinear Model-Based Control For Neuromuscular Electrical Stimulation, Ruzhou Yang

LSU Doctoral Dissertations

Neuromuscular electrical stimulation (NMES) is a technology where skeletal muscles are externally stimulated by electrodes to help restore functionality to human limbs with motor neuron disorder. This dissertation is concerned with the model-based feedback control of the NMES quadriceps muscle group-knee joint dynamics. A class of nonlinear controllers is presented based on various levels of model structures and uncertainties. The two main control techniques used throughout this work are backstepping control and Lyapunov stability theory.

In the first control strategy, we design a model-based nonlinear control law for the system with the exactly known passive mechanical that ensures asymptotical tracking. …

Experimental Study Of High-Temperature Range Latent Heat Thermal Energy Storage, Chatura Wickramaratne

USF Tampa Graduate Theses and Dissertations

Among all thermal energy storage (TES) systems, latent heat thermal energy storage (LHTES) attracts high interest due to its high energy density and high exergetic efficiency. Due to the high enthalpy of fusion and low cost, inorganic salts are becoming popular as phase change materials and are used as the storage media in LHTES systems. The main drawbacks for the inorganic salts are their low thermal conductivity and high reactivity above 500°C. Therefore, designing a cost-effective containment at these conditions with longevity is a challenge. Macro-encapsulation of the PCM is one way to solve both the PCM containment issue as …