Browsing by Subject "Department of Mechanical Engineering"
Now showing 1 - 16 of 16
Results Per Page
Sort Options
Item Analytical Analysis of Self-Folded Carbon Nanotube Structures(2012-04-18) Sun, LudongCarbon nanotubes (CNT) are allotropes of carbon with a cylindrical nanostructure, which exhibit excellent mechanical properties such as high strength and resilience. They are promising material for many areas. Due to computational limitations of full atomic simulations of CNT systems, one has to use a mesoscopic (coarse-grained) models, that are much more computationally efficient, but still able to capture the important features of the mechanical behavior of CNT systems. The big scope of the project we will research is to see if DEM can be effectively used for modeling CNT systems. Distinct element method (DEM) is a technique currently used for large scale simulations in granular and discontinuous materials such as granular flows, powder mechanics, and rock mechanics. DEM allows the use of particles with complex geometries rather than simply considering point masses and thousands of particles can be considered in a model with a relatively low computational cost. For the UROP I am doing, I did some basic jobs to do the analytical analysis for two configurations (nanoring and nanoracket) to find the critical length when is potential energy reaches the minimum value. The critical length for the nanoring is found to be 2 π √(EI/ η). E is the Young’s modulus of the carbon nanotube; I is the moment inertia for a hollow circular cross section; η is the cohesive energy. For the critical length for the nanoracket, the results varied because the different assumptions of the shape. The most accurate is found to be 12√(EI/ η). The results have been verified using the DEM in PFC3D, which means the DEM to model the carbon nanotube is acceptable.Item Assessment of O-ring Seal Performance by Measurement of Acoustic Emission Signals(2011-04-13) Sun, ZhenO-rings are commonly installed in fluid systems for sealing purpose. There is ongoing research towards improving O-rings’ sealing performances by using adaptive elastomeric materials at the Department of Mechanical Engineering at University of Minnesota. As part of seal development the performance of the seal has to be assessed. In this research a test stand for measuring leakage was constructed and leakage measurement was demonstrated as the seal leakage was measured by Monitoring Acoustic Emission (AE) signals. The test stand was constructed in which a specified load or a specified displacement can be applied to an O-ring held between flat plates, high pressure air introduced to the inside of the seal and AE due to leakage measured. The scope of this research was to try to quantify leakage rate of in use O-ring as a function of AE signals. The AE signals were measured as a function of volumetric air flow rate Q, working fluid pressure P, O-ring counterface force F and seal AE sensor distance d. Results showed that the Root Mean Square (RMS) values of AE signals increased with Q, P and F but decrease with d. Results also showed that the frequency spectrums of AE signals were wideband with multiple peaks at different frequencies. The physical interpretation of frequency spectrum was discussed but was not fully explained.Item Effects of Surfactants on The Yield and Size of Gold Nanorods(2011-02-03) Lee, Kuang ChinItem Elasticity of the Mouse Ocular Lens Capsule as Measured by Osmotic Swelling(2009-04-08) Powell, TracyAnimal basement membranes are networks of laminin, type IV collagen and other proteins essential for physiological functions. Deficiencies or abnormalities in the proteins can lead to muscular dystrophy, kidney disease, hearing loss, and, in the extreme, embryonic demise. In an effort to determine how the complex structure determines the functional properties of the basement membrane, the change in mechanical behavior is being investigated on samples with defective or absent associative proteins as compared to those with intact matrix components. A test was developed using the mouse model to take advantage of the genetic control possible in the mouse. The ocular lens capsule is a basement membrane which is large and thick, relative to others in the body, and which can be studied without major disruption. The lens is extracted from the eye and subjected to osmotic swelling, requiring minimal dissection and manipulation. The change in radius over time is evaluated with a mathematical model recently developed using porcine lenses to determine the elasticity of the capsule. Currently, data are being collected and analyzed to determine the elasticity of the normal mouse ocular lens capsule, which will serve as the control for future studies on mice with genetically-determined basement membrane modifications.Item Free Piston Engine CAD Model and Demonstrational Unit(2009-04-08) Guertin, BradA free piston engine consists of one or more pistons which is/are displaced each in one cylinder through a combustion process followed by a motion which would return it back to its pre-combustion location. The free piston engine differs from conventional engines in several ways including the way this return occurs and the result of the power stroke (the motion associated with gas expansion after combustion). Firstly, the conventional engine uses a series of linkages to turn the linear motion of the piston into a rotational motion. The free piston engine is different because it uses the linear motion to produce a different type of energy which, in the case of this project, would be electrical current and fluid power. Historically, this type of engine has only been used for small commercial products, but with some modifications, it could be developed into an engine which could power vehicles and similar machines currently powered with traditional internal combustion engines. Because of its design, it can operate more efficiently which has become a major advantage in today's fuel economy minded society.Item Heat Transfer in Liquid Piston Isothermal Air Compressor/Expander(2010) Rice, Andrew; Zhang, Chao; Saadat, Mohsen; Li, Perry; Simon, TerryAn "open accumulator" high pressure compressed air approach has been proposed for storing excess wind energy locally. This approach does not require special geological sites or additional fossil fuel as in conventional compressed air storage (CAES) approach. It relies on a combined hydraulics and pneumatic approach to attain both high energy density and power density. A critical element in the approach is an isothermal high pressure air compressor/expander. In this regard, research is underway to develop a liquid piston based compressor/expander with improved heat transfer and sealing properties.Item Hydrostatic Transmission for Wind Power Generation RS-0008-09(2010) Thul, Brenen; Dutta, Rahul; Stelson, Kim; Bohlmann, Brad; Gust, Mike; Kildegaard, ArneThe University of Minnesota is performing research on the application of continuously variable hydrostatic transmissions for wind turbines. By replacing the gearbox of traditional wind turbines with a continuously variable hydrostatic transmission (HST), the rotor speed could be controlled independent of the generator speed. This would allow the use of more conventional synchronous generators instead of higher cost variable speed permanent magnet generators, and eliminate the need for power electronics. The gearbox of traditional wind turbines is one of the primary sources of premature failure and maintenance. HSTs have been the dominant choice for propulsion in agricultural, construction, forestry, and mining vehicles for more than half a century. Thus, replacing the gearbox in a wind turbine with an HST should improve the reliability of the machine. The IREE seed funding will be used by the University of Minnesota to begin the process of building a lab scale (50 kW) test stand to perform research on applying HSTs to wind turbines. The research will initially focus on determining the best drivetrain hardware configuration as well as on optimizing the wind turbine’s control algorithm.Item Introduction of Cryopreservation Solutions Using a Microfluidic Device(2009-04-08) Fager, AndrewCryopreservation solutions must contain some type of cryoprotective agent. Conventional methods of cryopreserving blood cells for therapeutic applications involve the use of dimethyl sulfoxide (DMSO). Current methods of cryoprotectant introduction require trained lab technicians and are labor intensive. It is proposed that a microfluidic device can be used to introduce a cryopreservation solution into a cell suspension. Microfluidic devices for this application use low Reynolds number (laminar) flows to control cell motion and diffusion of DMSO from one stream to the other. Numerical simulations suggest that diffusion-based introduction of DMSO into cells using a microfluidic device is viable. In order to validate the theoretical model used in these simulations, a prototype was built and the flow of two parallel streams, (1) a cell suspension without DMSO or a PBS solution stream and (2) a donor stream with DMSO, was characterized experimentally. Desired outlet concentration is 10% DMSO v/v in cell suspension.Item The Reproducibility and Repeatability of Valgus Stress Radiographs to Assess Medial Knee Ligament Injuries(2009-04-08) Ihde, BrendanThe amount of medial compartment opening determined by valgus stress radiography for medial knee injuries has not been well documented. The purpose of this study was to use valgus stress radiography to measure medial compartment opening following sequential sectioning of medical knee structures and develop guidelines for clinical usage.Item Solar Fuels from Nanostructured Ceria-based Oxides(2011-11) Petkovich, Nick; Rudisill, Stephen; Boman, Daniel; Stein, Andreas; Venstrom, Luke; Davidson, Jane H.The solar resource can be converted into liquid fuels to offset petroleum use in the transportation sector using a thermochemical process based on cerium oxide (CeO2). To increase the rate of fuel production in the process, three-dimensionally ordered macroporous (3DOM) CeO2-based oxides are employed.Item Study of Behaviors of Single Large Intruders in Bulk Flow(2009-04-08) Sun, ZhenUnderstanding the fundamentals of granular flow is crucial to industrial applications. Good examples are found in processing pharmaceutical pills and ceramic powders. Mixing granular materials is a major concern for engineers who process granular materials. Developing sensor particles to track the flow of granular materials is a good way to understand the characteristics of granular flow. In order to facilitate the development of sensor particles, it is crucial to understand how the sensor particles behave in bulk granular flow. This research was to study how a single intruder's (sensor) movement might be different than that of the bulk particles. In other words, this research is to understand the segregation process, so that details of this disparate movement could be used to predict the bulk behavior. Most of the segregation occurs in the vertical direction so that most parts of this research is focused on exploring the vertical segregation between intruders and matrix particles.Item Thermochemical Seasonal Energy Storage using Calcium Chloride(2011-11) Quinnell, Josh; Davidson, JaneSpace heating accounts for 45 percent of all residential energy. The major challenge in using solar thermal systems for space heating is the inadequate winter solar resource. To address this challenge, we have developed long-term storage to save solar energy from the summer for use in the winter.Item Using Virtual Reality Environments for Medical Devices Design(2009-10-07) Konchada, Vamsi; Coffey, Dane; Borazjani, Iman; Sotiropoulos, Fotis; Erdman, Arthur; Interrante, Victoria; Keefe, Daniel F.There is an urgent need for improved design methodologies and tools that give designers meaningful and accurate feedback early in the design process; virtual reality can be used to fill this need. Virtual reality provides a highly engaging environment that allows user to experience and comprehend abstract concepts. It can allow designers to broadly explore the space of potential design alternatives, and to expand the boundaries of complex designs that are possible given today's computer assisted tools. Medical device researchers seek to better understand the complexities of cardiac anatomy, visualize how surrounding structures affect device function and deployment, and ultimately design more effective devices. Virtual representation combines visual graphics, virtual reality applications, finite element analysis based on the architecture of a 3D model. Introducing virtual reality based tools into the process of medical device design can significantly improve the process. We present our initial work aimed at developing new immersive visualization and interactive design tools for improving the medical device design process. Our initial work focuses on developing 3-dimensional visualizations of simulated blood flow through mechanical heart valves. Our goal is to develop 3D user interfaces for refining medical device designs within the context of patient-specific anatomy and simulated flow data.Item Visualization of Pulsating Low-Speed Flows from a Basic Annular Jet(2009-10-07) Padron, SantiagoFlow in the initial region of a pulsating low-speed annular water jet issuing into a quiescent water reservoir was visualized by means of a dye. The objective of this study was to characterize the different flow regimes as a function of pulse frequency. The blocking ratio was fixed at 0.7. The Reynolds number was varied from 59 to 155 and the Strouhalnumber from 0.133 to 1.90. For the experimental conditions considered, two different flow regimes were observed.