Commercially pure titanium can take up to six months to successfully manufacture a six-inch in diameter ingot in which can be shipped to be melted and shaped into other useful components. The applications to the corrosion-resistant, light weight, strong metal are endless, yet so is the manufacturing processing time. At a cost of around $80 per pound of certain grades of titanium powder, the everyday consumer cannot afford to use titanium in the many ways it is beneficial simply because the number of processing steps it takes to manufacture consumes too much time, energy, and labor. In this research, the steps it takes from the raw powder form to the final part are proposed to be reduced from 4-8 steps to only 2 steps utilizing a new technology that may even improve upon the titanium properties at the same time as it is reducing the number of steps of manufacture. The two-step procedure involves selecting a cylindrical or rectangular die and punch to compress a small amount of commercially pure titanium to a strong-enough compact for transportation to the friction stir welder to be consolidated. Friction stir welding invented in 1991 in the United Kingdom uses a tool, similar to …

Joining two dissimilar metals, specifically Mg and Al alloys, using conventional welding techniques is extraordinarily challenging. Even when these alloys are able to be joined, the weld is littered with defects such as cracks, cavities, and wormholes. The focus of this project was to use friction stir welding to create a defect-free joint between Al 2139 and Mg WE43. The stir tool used in this project, made of H13 tool steel, is of fixed design. The design included an 11 mm scrolled and concave shoulder in addition to a 6 mm length pin comprised of two tapering, threaded re-entrant flutes that promoted and amplified material flow. Upon completion of this project an improved experimental setup process was created as well as successful welds between the two alloys. These successful joints, albeit containing defects, lead to the conclusion that the tool used in project was ill fit to join the Al and Mg alloy plates. This was primarily due to its conical shaped pin instead of the more traditional cylindrical shaped pins. As a result of this aggressive pin design, there was a lack of heat generation towards the bottom of the pin even at higher (800-1000 rpm) rotation speeds. This …

Magnesium alloys are a popular research topic for structural applications because they have a lower density than conventional structural materials, including steel, titanium, and aluminum; however, the reliability and safety of their mechanical properties must be further proven. An important mechanical property for this purpose is fracture toughness, which is the measure of the material's resistance to crack propagation. In this study, a model of an experiment to investigate the fracture toughness of a magnesium alloy WE43 before and after friction stir processing (FSP) is developed, and the results are compared to those produced by a digital image correlation (DIC) system during an experiment from another paper. The model results of the material before FSP matched well with the DIC results, but the model of the material after FSP only partially matches the DIC results. In addition, a theoretical approach to calculating the standard fracture toughness value, KIc, from the modeling results is proposed, and is found to be a conservative approach.

Natural fibers like kenaf, hemp, flax and sisal fiber are becoming alternatives to conventional petroleum fibers for many applications. One such applications is the use of Non-woven bio-fiber mats in the automobile and construction industries. Non-woven hemp fiber mats were used to manufacture plywood in order to optimize the plywood structure. Hemp fiber mats possess strong mechanical properties that comparable to synthetic fibers which include tensile strength and tensile modulus. This study focuses on the use of hemp fiber mat as a core layer in plywood sandwich composite. The optimization of fiber mat plywood was done by performing a three factor experiment. The three factors selected for this experiment were number of hemp mat layers in the core, mat treatment of the hemp mat, and the glue content in the core. From the analysis of all treatments it was determined that single hemp mat had the highest effect on improving the properties of the plywood structure.

Cellular metals exhibit combinations of mechanical, thermal and acoustic properties that provide opportunities for various implementations and applications; light weight aerospace and automobile structures, impact and noise absorption, heat dissipation, and heat exchange. Engineered cell topologies enable one to control mechanical, thermal, and acoustic properties of the gross cell structures. A possible way to manufacture complex 3D metallic cellular solids for mass production with a relatively low cost, the investment casting (IC) method may be used by combining the rapid prototyping (RP) of wax or injection molding. In spite of its potential to produce mass products of various 3D cellular metals, the method is known to have significant casting porosity as a consequence of the complex cellular topology which makes continuous fluid's access to the solidification interface difficult. The effects of temperature on the viscosity of the fluids were studied. A comparative cost analysis between AM-IC and additive manufacturing methods is carried out. In order to manufacture 3D cellular metals with various topologies for multi-functional applications, the casting porosity should be resolved. In this study, the relations between casting porosity and processing conditions of molten metals while interconnecting with complex cellular geometries are investigated. Temperature, and pressure conditions on the …

Novel tissue mimicking materials have been developed for cancer treatment research. In the present research work, the tissue mimicking material is printed using 3D bioprinting technology. The nanoparticles are homogeneously mixed with tissue mimicking materials to enhance the heating capacity. The thermal conductivity of tissue mimicking materials is measured using a micropipette thermal sensor (MTS). Further, the optimal value is identified based on optimization technique and incorporated into a theoretical model to predict the surface temperature of microsphere. The heat conduction governing equation with Lambert law is numerically solved using COMSOL Multiphysics software. To validate the present simulation results, the experiments are conducted using a continuous laser system.

This thesis project investigates the configuration of an enclosed evaporation chamber with the intention of converting seawater into potable freshwater. The evaporation chamber's sole heat source is provided by a Fresnel lens, located above the chamber, which concentrates sunlight onto a 3-inch diameter focal plate built into the core of the chamber. The design of the evaporation chamber is modeled after a solar still and is coupled with a heat exchanger to boost efficiency of the system. The chamber was designed with the objectives of being portable, lightweight, low cost, corrosion resistant, interchangeable, and size convenient with the goal of producing 1 Liter of freshwater per hour of operation. The evaporation chamber consists of two primary components, a core and an attached arrangement of fins, all of which are heated via the Fresnel lens. A consistent intake of 2 grams/second of saltwater enters from the top of the chamber and is then gravity fed across the fins. Fin orientation has been designed to inhibit the flow rate of water within the chamber, maximizing the surface area of contact with the heated fins. The evaporation chamber was modeled through SOLIDWORKS and underwent a physical optimization study to reduce material usage while …

This research investigates the bio-products/phase change material (PCM) composites for the building envelope application. Bio-products, such as wood and herb, are porous medium, which can be applied in the building envelope for thermal insulation purpose. PCM is infiltrated into the bio-product (porous medium) to form a composite material. The PCM can absorb/release large amount of latent heat of fusion from/to the building environment during the melting/solidification process. Hence, the PCM-based composite material in the building envelope can efficiently adjust the building interior temperature by utilizing the phase change process, which improves the thermal insulation, and therefore, reduces the load on the HVAC system. Paraffin wax was considered as the PCM in the current studies. The building energy savings were investigated by comparing the composite building envelope material with the conventional material in a unique Zero-Energy (ZØE) Research Lab building at University of North Texas (UNT) through building energy simulation programs (i.e., eQUEST and EnergyPlus). The exact climatic conditions of the local area (Denton, Texas) were used as the input values in the simulations. It was found that the EnergyPlus building simulation program was more suitable for the PCM based building envelope using the latent heat property. Therefore, based on the …

There is a wide range of applications for 3D printing technology with an additive manufacturing such as aerospace, automotive, marine and oil/gas, medical, consumer, electronics, building construction, and many others. There have been many pros and cons for 3D additive manufacturing. Even though 3D printing technology has many advantages: freedom to design and innovate without penalties, rapid iteration through design permutations, excellence mass customization, elimination of tolling, green manufacturing, minimal material wastes, energy efficiency, an enablement of personalized manufacturing. 3D additive manufacturing still has many disadvantages: unexpected pre- and post-processing requirement, high-end manufacturing, low speed for mass production, high thermal residual stress, and poor surface finish and dimensional accuracy, and many others. Especially, the issues for 3D additive manufacturing are on high cost for process and equipment for high-end manufacturing, low speed for mass production, high thermal residual stress, and poor surface finish and dimensional accuracy. In particular, it is relatively challenging to produce casting products with lattice or honeycomb shapes having sophisticated geometries. In spite of the scalable potential of periodic cellular metals to structural applications, the manufacturing methods of I∙AM Casting have been not actively explored nor fully understood. A few qualitative studies of I∙AM Casting has been …

Emissions of air pollutants from non-conventional sources have been on the rise in the North Texas area over the past decade. These include primary pollutants such as volatile organic compound (VOC) and oxides of nitrogen (NOx) which also act as precursors in the formation of ozone. Most of these have been attributed to a significant increase in oil and gas production activities since 2000 within the Barnett Shale region adjacent to the Dallas-Fort Worth metroplex region. In this study, air quality concentrations measured at the Denton Airport and Dallas Hinton monitoring sites operated by the Texas Commission on Environmental Quality (TCEQ) were evaluated. VOC concentration data from canister-based sampling along with continuous measurement of oxides of nitrogen (NOx), ozone (O3), particulate matter (PM2.5), and meteorological conditions at these two sites spanning from 2000 through 2014 were employed in this study. The Dallas site is located within the urban core of one of the fastest growing cities in the United States, while the Denton site is an exurban site with rural characteristics to it. The Denton Airport site was influenced by natural gas pads surrounding it while there are very few natural gas production facilities within close proximity to the Dallas …

This research work is focused on a conceptual combination of membrane-based energy recovery ventilator (ERV) and phase change material (PCM) to provide energy savings in building heating, ventilation & air-conditioning (HVAC) systems. An ERV can recover thermal energy and moisture between the outside fresh air (OFA) entering into the building and the exhaust air (EA) leaving from the building thus reducing the energy consumption of the HVAC system for cooling and heating the spaces inside the building. The membranes were stacked parallel to each other forming adjacent channels in a counter-flow arrangement for OFA and EA streams. Heat and moisture is diffused through the membrane core. Flat-plate encapsulated PCM is arranged in OFA duct upstream/downstream of the ERV thereby allowing for further reduction in temperature by virtue of free cooling. Paraffin-based PCMs with a melting point of 24°C and 31°C is used in two different configurations where the PCM is added either before or after the ERV. Computational fluid dynamics (CFD), and heat and mass transfer modeling is employed using COMSOL Multiphysics v5.3 to perform the heat and mass transfer analysis for the membrane-based ERV and flat-plate PCMs. An 8-story office building was considered to perform building energy simulation using …

The goal of this dissertation is to demonstrate that data from a remotely located building can be utilized for energy modeling of a similar type of building and to demonstrate how to use this remote data without physically moving the data from one server to another using Virtual Information Fabric Infrastructure (VIFI). In order to achieve this goal, firstly an EnergyPlus model was created for Greek Life Center, a campus building located at University of North Texas campus at Denton in Texas, USA. Three thermal comfort models of Fanger model, Pierce two-node model and KSU two-node model were compared in order to find which one of these three models is most accurate to predict occupant thermal comfort. This study shows that Fanger's model is most accurate in predicting thermal comfort. Secondly, an experimental data pertaining to lighting usage and occupancy in a single-occupancy office from Carnegie Mellon University (CMU) has been implemented in order to perform energy analysis of Greek Life Center assuming that occupants in this building's offices behave similarly as occupants in CMU. Thirdly, different data types, data formats and data sources were identified which are required in order to develop a city-scale urban building energy model (CS-UBEM). …

For years, the alloy of choice for electroplating electronic components has been tin-lead (Sn-Pb) alloy. However, the legislation established in Europe on July 1, 2006, required significant lead (Pb) content reductions from electronic hardware due to its toxic nature. A popular alternative for coating electronic components is pure tin (Sn). However, pure tin has the tendency to spontaneously grow electrically conductive Sn whisker during storage. Sn whisker is usually a pure single crystal tin with filament or hair-like structures grown directly from the electroplated surfaces. Sn whisker is highly conductive, and can cause short circuits in electronic components, which is a very significant reliability problem. The damages caused by Sn whisker growth are reported in very critical applications such as aircraft, spacecraft, satellites, and military weapons systems. They are also naturally very strong and are believed to grow from compressive stresses developed in the Sn coating during deposition or over time. The new directive, even though environmentally friendly, has placed all lead-free electronic devices at risk because of whisker growth in pure tin. Additionally, interest has occurred about studying the nature of other metal whiskers such as zinc (Zn) whiskers and comparing their behavior to that of Sn whiskers. Zn …

Interfacial mechanical properties of adhesive joints are very crucial in board applications, including composites, multilayer structures, and biomedical devices. Establishing traction-separation (T-S) relations for interfacial adhesion can evaluate mechanical and structural reliability, robustness, and failure criteria. Due to the short range of interfacial adhesion such as micro to nanoscale, accurate measurements of T-S relations remain challenging. The advent of machine learning (ML) became a promising tool to predict materials behaviors and establish data-driven mechanical models. In this study, we integrated a state-of-the-art ML method, finite element analysis (FEA), and standard experiments to develop data-driven models for characterizing the interfacial mechanical properties precisely. Macroscale force-displacement curves are derived from FEA with incorporation of double cantilever beam tests to generate the dataset for ML model. The eXtreme Gradient Boosting (XGBoost) multi-output regressions and classifier models are used to determine T-S relations with R2 score of 98.8% and locate imperfections at the interface with accuracy of around 80.8%. The outcome of the XGBoost models demonstrated accurate predictions and fast calculation speed, outperforming several other ML methods. Using 3D printed double cantilever beam specimens, the performance of the ML models is validated experimentally for different materials. Furthermore, a XGBoost model-based package is designed to …

This study investigated a new approach to achieving high energy density supercapacitors (SCs) by using high surface area self-activated carbon from waste coffee grounds (WCGs) and modifying 3D printed electrodes' porous structure by varying infill density. The derived activated carbons' surface area, pore size, and pore volume were controlled by thermally treating the WCGs at different temperatures (1000˚C, 1100˚C, and 1200˚C) and post-treating with HCL to remove water-soluble ashes and contaminants that block activated carbon pores. Surface area characterization revealed that the carbon activated at 1000˚C had the highest surface of 1173.48 m2 g-1, and with the addition of HCL, the surface area increased to 1209.35 m2 g-1. This activated carbon was used for fabricating the electrodes based on the surface area and having both micropores and macropores, which are beneficial for charge storage. Direct ink writing (DIW) method was utilized for 3D printing SC electrodes and changing the electrode structure by increasing the infill densities at 30%, 50%, and 100%. Upon increasing the infill densities, the electrodes' mass increased linearly, porosity decreased, and the total surface area increased for the 30% and 50% infill electrodes but decreased for the 100% infill electrode. Cyclic voltammetry (CV) test on the assembled …

Nondestructive testing (NDT) using ultrasound band 1-5 MHz, has been widely used for the early-stage detection of structural failure; however, it fails to detectf material degradation, fatigue, and microcracks. NDT with nonlinear ultrasound (NLU) can detect a microscopic discontinuity or imperfection that may be a source of the second harmonic in the reflected signal. In this research, we focus on creating a metamaterial band filter that filters out nonlinearities induced by the instrument itself. A 1D elastic superlattice (SL) acoustic filter is designed with a bandgap in its frequency spectrum that covers the frequency range of second harmonic. The SL is made of periodically alternating Cu and Sn-Pb solder layers. We conducted analytical and numerical calculations to obtain the appropriate thickness of each layer. The metamaterial in this study has the pass band for the fundamental frequency of 5 MHz and the first stop band centered near the frequency of 10 MHz; 5 MHz was chosen because the second harmonic at 10 MHz can detect 200μm micro-scale damage. Experiments with aluminum as the reference specimen and with SL filter were conducted. A function-generator generates 3 pulses sine signal, within the frequency range from 2.5 MHz to 20MHz. Spectral analysis of …

Sequential single-axis vibration testing strategies often produce over-testing when qualifying system hardware. Multi-axis excitation techniques can simulate realistic service environments, but the hardware and testing strategies needed to do so tend to be costly and complex. Test engineers instead must execute sequential tests on single-axis shaker tables to excite each degree of freedom, which the previous two decades of vibration testing literature have shown to cause extensive over-testing when considering cross-axis responses in assessing the severity of the applied test environments. Traditional assessments assume that the test article responds only in the axis of excitation, but often significant response occurs in the off-axes as well. This paper proposes a method to address the over-testing problem by approximating a simultaneous multi-axis test using readily-available, single-axis shaker tables. By optimizing the angle of excitation and the boundary condition through dynamic test fixture design, the test article can be tested using a Single-Input, Multiple-Output (SIMO) test in a way that approximates a Multiple-Input, Multiple-Output (MIMO) test. This paper shows the proposed method in simulation with a 2D finite element box assembly with removable component (BARC) model attached to springs with variable stiffness. The results include quantified test quality assessment metrics with comparison to …

A particle image velocimetry (PIV) computer software is analyzed in this work by applying automatic differentiation on it. We create two artificial images that contained particles that where moved with a known velocity field over time. These artificial images were created with parameters that we would have on real PIV experiments. Then we applied a PIV software to find the velocity output vectors. As we mentioned before, we applied automatic differentiation through all the algorithm to track the derivatives of the output vectors regarding interesting parameters declared as inputs. By analyzing these derivatives we analyze the sensitivity of the output vectors to changes on each one of the parameters analyzed. One of the most important derivatives calculated in this project was the derivative of the output regarding the image intensity. In future work we plan to use this derivative combined with the intensity probability distribution of each image pixel, to find PIV uncertainties. If we achieve this goal we will find an uncertainty method that will save computational power and will give uncertainty values with computer accuracy.

In this study, a series of denim fiberboards are fabricated using two different resins, malamine urea formaldehyde (MUF) and polymeric methylene diphenyl diisocyanate (pMDI). Two experimental design factors (1) adhesive content and (2) MUF-pMDI weight ratio, were studied. All the denim fiberboard samples were fabricated following the same resin blending, cold-press and hot-press procedures. The physical and mechanical tests were conducted on the fiberboard following the procedures described in ASTM D1037 to obtain such as modulus of elasticity (MOE), modulus of rupture (MOR), internal bond (IB), thickness swell (TS), and water absorption (WA). The results indicated that the MOE was significantly affected by both factors. IB was affected significantly by weight ratio of different glue types, with 17 wt% more MDI resin portion in the core layer of the denim boards, the IB for total adhesive content 15% fiberboard was enhanced by 306%, while for total adhesive content 25% fiberboard, enhanced by 205%. TS and WA, with higher adhesive content used in denim boards' fabrication, and more pMDI portion in the core layer of the boards, the boards' TS and WA was reduced by up to 64.2% and 78.8%, respectively.

Incorporating insulation material with phase change materials (PCMs) could help enhance the insulation capability for further building energy savings by reducing the HVAC loadings. During the phase change process between the solid and liquid states, heat is being absorbed or released by PCMs depending on the surrounding temperature. This research explores the benefits of a polyurethane (PU)-PCM composite insulation material through infiltrating paraffin wax as PCM into PU open cell foam. The new PU-PCM composite provides extra shielding from the exterior hot temperatures for buildings. Through this study, it was demonstrated that PU-PCM composite insulation could potentially help building energy savings through reducing the loads on the HVAC systems based on the building energy modeling using EnergyPlus. The Zero Energy Lab (ZØE) at the University of North Texas was modeled and studied in the EnergyPlus. It is a detached building with all wall facades exposed to the ambient. It was determined that the new PU-PCM insulation material could provide 14% total energy saving per year and reduce the electricity use due to cooling only by around 30%.

Providing conditioned and fully controlled room is the final goal for having a comfortable building. But on the other hand making smart controllers to provide the required cooling or heating load depending on occupants' real time feeling is necessary. This study has emphasized on finding a meaningful and steady state parameter in human body that can be interpreted as comfort criterion which can be expressed as the general occupants' sensation through their ambient temperature. There are lots of researches on human physiological behavior in different situations and also different body parts reaction to the same ambient situation. Body parts which have the biggest reliable linear fluctuation to the changes are the best subject for this research. For these tests, wrist and palm have been selected and their temperatures on different people have been measured accurately with thermal camera to follow the temperature trend on various comfort levels. It is found that each person reaches to his own unique temperature on these two spots, when he/ she feels comfortable, or in other word each person's body temperature is a precise nominate for comfort feeling of that individual. So in future by having this unique comfort parameter and applying them to the …

The use of collection systems for magnetic sorbents such as Magnetic Activated Carbon are discussed in order to gauge their efficacy in marine environments. Two collectors were built and tested, one which utilized a radial orientation of magnets and another with axially placed magnets. The two systems underwent a series of test with differing linear velocities and angular velocities. From the results, the axial system outperformed its radial counterpart, being most effective with a relatively high concentration of discs placed in series. The medium concentration, however, proved increasingly effective with higher velocities, meaning an optimization concentration exists for this design. The radial system was tested with high and low concentrations of small and large magnets, respectively. The larger magnets, although providing less concentration points in the alternating array, proved more effective for the collection of MAC. From these tests several new innovations were suggested, including belt tensioners, add on mechanisms, and a hybridized design in order to fully optimize the collection of MAC.

This dissertation focuses on studying membrane air dehumidification for a membrane moisture exchanger in a membrane heat pump system. The study has two parts: an optimization of membrane moisture exchanger for air dehumidification in the macroscale, and diffusion of water vapor in polymer nanocomposites membrane for humid air dehumidification in the nanoscale. In the first part of the research, the mass transport of water vapor molecules through hydrophilic silica nanochannel chains in hydrophobic polyurethane matrix was studied by simulations and experiments for different membrane moisture exchanger design configurations. The mass transport across the polymer nanocomposite membrane occurs with the diffusion of moist air water vapor molecules in the membrane moisture exchanger in a membrane heat pump air conditioning system for air dehumidification purposes. The hydrophobic polyurethane matrix containing the hydrophilic silica nanochannel chains membrane is responsible for transporting water vapor molecules from the feed side to the permeate side of the membrane without allowing air molecules to pass through.In the second part of the research, diffusion analysis of the polymer nanocomposite membrane were performed in the nanoscale for the polymer nanocomposite membrane. The diffusion phenomena through the polymer, the polymer nanocomposite without modifying the silica surfaces, and the polymer nanocomposite …

Pillared-graphene structure (PGS) is a novel three-dimensional structure consists of parallel graphene sheets that are separated by carbon nanotube (CNT) pillars that is proposed for efficient thermal management of electronics. For microscale simulations, finite element analyses were carried out by imposing a heat flux on several PGS configurations using a Gaussian pulse. The temperature gradient and distribution in the structures was evaluated to determine the optimum design for heat transfer. The microscale simulations also included conducting a mesh-independent study to determine the optimal mesh element size and shape. For nanoscale simulations, Scienomics MAPS software (Materials And Processes Simulator) along with LAMMPS (Large-scale Atomic/ Molecular Massively Parallel Simulator) were used to calculate the thermal conductivity of different configurations and sizes of PGS. The first part of this research included investigating PGS when purely made of carbon atoms using non-equilibrium molecular dynamics (NEMD). The second part included investigating the structure when supported by a copper foil (or substrate); mimicking production of PGS on copper. The micro- and nano-scale simulations show that PGS has a great potential to manage heat in micro and nanoelectronics. The fact that PGS is highly tunable makes it a great candidate for thermal management applications. The simulations were …