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2015

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Articles 811 - 840 of 1219

Full-Text Articles in Mechanical Engineering

Analytical Modeling Of Helium Turbomachinery Using Fortran 77, Purushotham Balaji Jan 2015

Analytical Modeling Of Helium Turbomachinery Using Fortran 77, Purushotham Balaji

Mechanical and Aerospace Engineering Theses - Archive

Advanced Generation IV modular reactors, including Very High Temperature Reactors (VHTRs), utilize helium as the working fluid, with a potential for high efficiency power production utilizing helium turbomachinery. Helium is chemically inert and nonradioactive which makes the gas ideal for a nuclear power-plant environment where radioactive leaks are a high concern. These properties of helium gas helps to increase the safety features as well as to decrease the aging process of plant components.The lack of sufficient helium turbomachinery data has made it difficult to study the vital role played by the gas turbine components of these VHTR powered cycles. Therefore, …

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Design And Cfd Analysis Of The Intake Manifold For The Honda Cbr250rr Engine, Subhash Seshadri Jan 2015

Design And Cfd Analysis Of The Intake Manifold For The Honda Cbr250rr Engine, Subhash Seshadri

Mechanical and Aerospace Engineering Theses - Archive

The scope of this project is to improve reliability issues on a turbocharged Honda CBR250RR engine and boost the performance by redesigning the intake manifold - one of the key components of this engine package. The engine has been used in the past by the UTA Formula SAE team in several open-wheeled race cars providing a light weight platform with a high power to weight ratio. Previous intake manifolds did not provide balanced distribution of air flow among all cylinders. This lead to incorrect air/fuel ratios were some cylinders ran too lean at times, while others were running too rich. …

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Numerical Investigation Of Steady State And Transient Thermal Performance Of A Multi-Chip Vapor Chamber, Mohammad Parhizi Jan 2015

Numerical Investigation Of Steady State And Transient Thermal Performance Of A Multi-Chip Vapor Chamber, Mohammad Parhizi

Mechanical and Aerospace Engineering Theses - Archive

Effective dissipation of heat generated in microelectronic devices during operation is critical for reliability and performance, particularly for advanced architectures such as microserver chips. Vapor chambers are a class of heat spreaders that have received much recent attention due to their passive nature and superior heat spreading capability. Several studies have investigated thermal performance of vapor chambers as heat spreading devices. However, developing a simple and accurate model which could be easily used in industry is still a big challenge. Moreover, more work needs to be done to optimize the performance of vapor chambers. For instance, developing a vapor chamber …

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Developing A 7mmx7mm Qfn Package Using Liquid Crystal Polymer, Mitul H. Naik Jan 2015

Developing A 7mmx7mm Qfn Package Using Liquid Crystal Polymer, Mitul H. Naik

Mechanical and Aerospace Engineering Theses - Archive

Quad Flat No-Lead (QFN) packages are one of the most widely used and popular packages in the industry. The QFN packages gained popularity in the last decade because of its excellent electrical/thermal characteristics and lower costs. QFN packages are widely used in automotive, defense, handheld devices where space is a constraint and high current circuits require the package is mounted on thick printed circuit boards. This work makes an attempt to develop an economical 7mm*7mm QFN package using Liquid Crystal Polymer (LCP).The first challenge in this work investigate the different grades of LCP to match the electrical as well as …

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Fluid-Crack Interaction In Hydraulic Fracturing, Harshil Vora Jan 2015

Fluid-Crack Interaction In Hydraulic Fracturing, Harshil Vora

Mechanical and Aerospace Engineering Theses - Archive

Hydraulic fracturing has been one of the major improvements in petroleum engineering in the past few decades. Since then this process has been used progressively and over million wells have been fracked using hydraulic fracturing technology. A thorough understanding of the formation of fracture network and its propagation is essential to keep evolving the technology. In the present study, the Linear Elastic Fracture Mechanics (LEFM) approach is applied to the crack propagation to understand the fluid crack interaction in brittle rocks under hydraulic loading. The boundary element method (BEM) is used to carry out the numerical analysis. Additionally, an explicit …

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Design And Optimization Of Under Tray For Formula Sae Race Car Using Cfd Analysis, Girish Bangalore Jalappa Jan 2015

Design And Optimization Of Under Tray For Formula Sae Race Car Using Cfd Analysis, Girish Bangalore Jalappa

Mechanical and Aerospace Engineering Theses - Archive

With the advent of inverted wings to produce down-force in Formula-1 during the 1960's, aerodynamics has played a big role in increasing the vehicle performance. An aerodynamics system consists of front, rear wings and an under-tray. This thesis focuses on design of a new under-tray using CFD analysis for a Formula-SAE car.

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Simulation Of Indeterminate Multiple, Simultaneous Impact And Contact For A Flexible Multibody System, Rohit Vijay Katti Jan 2015

Simulation Of Indeterminate Multiple, Simultaneous Impact And Contact For A Flexible Multibody System, Rohit Vijay Katti

Mechanical and Aerospace Engineering Theses - Archive

This work presents a method for understanding the impact behaviour of a flexible body undergoing multiple, simultaneous contacts. A continuous model is used with an event-driven function in MATLAB, which detects the collisions. The flexible body is defined as a system of particles, having inter-particle forces in terms of spring, damper coefficients. Equations of motion for such a Flexible MultiBody system are determined and then solved for different phases.In the method presented, the indeterminate nature of equations of motion encountered, during impact, and contact for flexible body are examined. Constraint forces are determined during the different phases of an impact …

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Thermo-Mechanical Design Considerations At The Server And Rack Levels To Achieve Maximum Data Center Energy Efficiency, Richard Mark Eiland Jan 2015

Thermo-Mechanical Design Considerations At The Server And Rack Levels To Achieve Maximum Data Center Energy Efficiency, Richard Mark Eiland

Mechanical and Aerospace Engineering Dissertations - Archive

Continually increasing demand for information technology (IT) applications and services has provided sustained growth and interest in data centers. The large amounts of energy consumed by data center facilities have placed a significant emphasis on the energy efficiency of their overall operation. One area of particular importance is the cooling energy required. Heat generation within a data center starts at the server level, specifically within the microelectronic devices that process digital information. Convective heat transfer is the primary driver for the removal of heat from an individual server. As such, cooling efficiency at the server level will be dictated by …

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Nanoscale Toughening Mechanisms Of Ultra High Temperature Novel Hfb2 Based Multiphase Ceramics, Zoher Shabbir Lavangia Jan 2015

Nanoscale Toughening Mechanisms Of Ultra High Temperature Novel Hfb2 Based Multiphase Ceramics, Zoher Shabbir Lavangia

Mechanical and Aerospace Engineering Theses - Archive

During return of spacecraft they endure very high temperatures (3000°F), few materials can withstand temperatures this high along with additional loads of the spacecraft. Reinforced carbon-carbon (RCC) material system is used as Thermal Protection System (TPS) which is made of laminated graphite rayon-phenolic epoxy, which need to sustain extreme heat. However, these materials are very prone to premature degradation due to oxidation. Silicon Carbide (SiC) and Hafnium Diboride (HfB2) are candidate materials for TPS but, they inherently lack the required toughness for such applications. This research is carried out in two stages, first is to study the individual properties of …

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Minimizing Power Consumption At Module, Server And Rack-Levels Within A Data Center Through Design And Energy-Efficient Operation Of Dynamic Cooling Solutions, John Edwards Fernandes Jan 2015

Minimizing Power Consumption At Module, Server And Rack-Levels Within A Data Center Through Design And Energy-Efficient Operation Of Dynamic Cooling Solutions, John Edwards Fernandes

Mechanical and Aerospace Engineering Dissertations - Archive

Data center energy consumption continues to increase with the proliferation in online services such as social networking, banking, entertainment, cloud computing, etc. Recent estimates show that associated power consumption accounts for around 2% and 1.8% of electricity production in the United States and worldwide respectively. In addition to growth in the industry, power densities continue to rise in IT equipment increasing the criticality of thermal management in data center operation. Cooling systems account for around a third of overall power consumption requiring more energy-efficient solutions across all levels within the facility.Liquid cooling of high power modules using cold plates has …

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Formalization Of The Engineering Science Discipline - Knowledge Engineering, Xiao Peng Jan 2015

Formalization Of The Engineering Science Discipline - Knowledge Engineering, Xiao Peng

Mechanical and Aerospace Engineering Dissertations - Archive

Knowledge is the most precious ingredient facilitating aerospace engineering research and product development activities. Currently, the most common knowledge retention methods are paper-based documents, such as reports, books and journals. However, those media have innate weaknesses. For example, four generations of flying wing aircraft (Horten, Northrop XB-35/YB-49, Boeing BWB and many others) were mostly developed in isolation. The subsequent engineers were not aware of the previous developments, because these projects were documented such which prevented the next generation of engineers to benefit from the previous lessons learned. In this manner, inefficient knowledge retention methods have become a primary obstacle for …

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Aspects Of Intuitive Control Framework: Stabilize, Optimize, And Identify, Pavan Kumar Nuthi Jan 2015

Aspects Of Intuitive Control Framework: Stabilize, Optimize, And Identify, Pavan Kumar Nuthi

Mechanical and Aerospace Engineering Dissertations - Archive

The duality of estimation and control problems is a well known fact in control theory literature. Parameter convergence and closed loop stability are usually competing interests for a given control scheme. This motivates identification routines to be performed only in offline experiments. On the other hand stable controllers do not guarantee parameter convergence to true parameters. Thus there is a need for a higher level abstraction for a control scheme which acts in stages and prioritizes various aspects at different stages. The stage abstraction for controller is inspired by human intuition towards dealing with control and identification simultaneously and hence …

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A Numerical Study Of Microfluidic Droplet Motions In Parallel-Plate Electrowetting-On-Dielectric (Ewod) Devices, Yin Guan Jan 2015

A Numerical Study Of Microfluidic Droplet Motions In Parallel-Plate Electrowetting-On-Dielectric (Ewod) Devices, Yin Guan

Mechanical and Aerospace Engineering Dissertations - Archive

Microscale water droplet motions in parallel-plate electrowetting-on-dielectric (EWOD) devices including transport, splitting, merging and dispensing have been numerically studied. The transient governing equations for the microfluidic flow are solved by a finite volume scheme with a two-step projection method on a fixed computational domain. The interface between liquid and gas is tracked by a coupled level set and volume-of-fluid (CLSVOF) method. A continuum surface force (CSF) model is employed to model the surface tension at the interface. Contact angle hysteresis which is an essential component in EWOD modeling is implemented together with a simplified model for the viscous stresses exerted …

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Composite Tie Rod Research, Design And Testing For Sae Baja, Amanda M. Nauman Jan 2015

Composite Tie Rod Research, Design And Testing For Sae Baja, Amanda M. Nauman

Williams Honors College, Honors Research Projects

Composite materials have become increasing popular in recent years. For the Baja SAE team, composites are typically only used for body panels. To grow as a team and to earn additional points in design competition, it was decided to explore composite use in mechanical applications, specifically for the tie rods. Research was conducted, looking into composite materials basics, types, and material properties. Additionally, manufacturing was explored, including a few projects separate from the tie rod application. 3D models were created after the materials were selected, and FEA analysis was conducted on the parts. Once theoretical testing was finished, the physical …

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Experimental And Computational Analysis Of Thermosyphon Based Water Heaters, Siddarth Ashokkumar Jan 2015

Experimental And Computational Analysis Of Thermosyphon Based Water Heaters, Siddarth Ashokkumar

Masters Theses

"Storage type electric water heaters are one of the most commonly found type of heaters in households today. Due to energy costs and limited generation capacity, there is a need for improving the efficiency of such water heaters. The efficiency of water heating systems have impact both at the household and at the national level, because of their sheer numbers. Efficient water heaters lead to lower utility bills for the consumer and also reduced demand on the grid supplying electrical power to such households. This leads to a reduction in the amount of fuel used in generating electrical power and …

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Generation And Validation Of Optimal Topologies For Solid Freeform Fabrication, Purnajyoti Bhaumik Jan 2015

Generation And Validation Of Optimal Topologies For Solid Freeform Fabrication, Purnajyoti Bhaumik

Masters Theses

"The study of fabricating topologically optimized parts is presented hereafter. The mapping of topology optimization results for Standard Tessellation Language (STL) writing would enable the solid freeform fabrication of lightweight mechanisms. Aerospace leaders such as NASA, Boeing, Airbus, European Aeronautic Defense And Space Company (EADS), and GE Aero invest in topology optimization research for the production of lightweight materials. Certain concepts such as microstructural homogenization, discretization, and mapping are reviewed and presented in the context of topology optimization. Future biomedical applications of solid freeform fabrication such as organ printing stand to save millions of lives through the robust development of …

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Freeform Extrusion Fabrication Of Titanium Fiber Reinforced 13-93 Bioactive Glass Scaffolds, Albin Thomas Jan 2015

Freeform Extrusion Fabrication Of Titanium Fiber Reinforced 13-93 Bioactive Glass Scaffolds, Albin Thomas

Masters Theses

"Although implants made with bioactive glass have shown promising results for bone repair, their application in repairing load-bearing long bones is limited due to their poor mechanical properties as compared to human bones. This thesis study is on freeform extrusion fabrication of silicate based 13-93 bioactive glass scaffolds reinforced with titanium fibers. A composite paste was prepared with 13-93 bioactive glass filled with titanium fibers (~16 µm in diameter and aspect ratio of ~250) having 0.1 to 0.4 vol. % of the bioactive glass scaffold. This paste was then filled into a syringe manually, and then extruded through a nozzle …

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Improving Fracture Toughness Of Silicon Carbide Based Ceramics By Microstructure Tailoring, Sheikh Fahad Ferdous Jan 2015

Improving Fracture Toughness Of Silicon Carbide Based Ceramics By Microstructure Tailoring, Sheikh Fahad Ferdous

Mechanical and Aerospace Engineering Dissertations - Archive

Ceramic materials are one of the most promising materials for wide variety of technical applications such as automotive, aerospace, medical, and other applications. They have very high strengths and high melting points relative to metals. However, low fracture toughness is one of the main barriers of ceramics prohibiting their wide-spread applications. This is because ceramics are mainly bonded with directional bonds which don’t allow dislocations based deformation. Several attempts have been made to increase the toughness of ceramic materials without sacrificing significantly the other mechanical properties. Here three different types of SiC based ceramics have been computationally (atomistic and up-scaled …

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Novel Device And Methods For Composite Material Characterization, Michael M. Tadros Jan 2015

Novel Device And Methods For Composite Material Characterization, Michael M. Tadros

Mechanical and Aerospace Engineering Dissertations - Archive

Composite materials have several advantages over metallic materials, with their high specific strength and ability to be elastically tailored to create advantageous structural responses. However, the widespread implementation of composite materials in primary structures is limited by our knowledge of how damage mechanisms interact and spread inside composite parts. To date, characterization has been conducted using one of two methods, surface measurements and subsurface measurements. Surface measurements cannot in general capture the failure of multidirectional composite laminates. Subsurface measurements allow for observations of the internal material structure and damage mechanisms inside the composite which might facilitate greater understanding of the …

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Computational Analysis Of I.T. Rack Under Vibration Load, Framroz Meheryar Bharucha Jan 2015

Computational Analysis Of I.T. Rack Under Vibration Load, Framroz Meheryar Bharucha

Mechanical and Aerospace Engineering Theses - Archive

Structural failure of a rack due to vibration could result in injury to people, damage to IT equipment, or interruption of services that depend on proper functioning of the IT and networking equipment in the rack. In this topic, a computational study of an IT rack and a group of racks placed adjacent to each other under three vibration load scenarios: transportation, office and earthquake vibration is presented.Each rack can weigh as much as 1600 kg (3500 lb.) when fully populated with IT equipment. Two standards commonly used for testing racks with synthetic seismic loads are the GR-63-CORE Network Equipment …

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Performance Analysis Of A Helium Cooled Vhtr Powered Brayton Cycle Topping Unit On An Existing Steam Cycle Using Numerical Propulsion System Simulation, Warren Romao Caetano Freitas Jan 2015

Performance Analysis Of A Helium Cooled Vhtr Powered Brayton Cycle Topping Unit On An Existing Steam Cycle Using Numerical Propulsion System Simulation, Warren Romao Caetano Freitas

Mechanical and Aerospace Engineering Theses - Archive

With the decommissioning of ageing coal power plants due to outdated technology and high levels of air pollution, the advantages of overhauling existing infrastructure is twofold. First, by providing an alternate, sustainable fuel source, like nuclear power, the problem of air pollution can be brought to check. Second, utilizing existing steam plant infrastructure reduces initial investment costs and allows investors to keep the existing steam plant running until the new infrastructure is ready to go online.The focus of this research is to design and analyze the topping cycle required to support an existing 300 MW power plant based on the …

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Quantifying Air Flow Rate Through A Server In An Operational Data Center And Assessing The Impact Of Using Theoretical Fan Curve, Neha Shigrekar Jan 2015

Quantifying Air Flow Rate Through A Server In An Operational Data Center And Assessing The Impact Of Using Theoretical Fan Curve, Neha Shigrekar

Mechanical and Aerospace Engineering Theses - Archive

Cooling is one of the major cost factors in data centres that accounts for 37% of the total data centre electricity consumption. Demands on cooling systems have increased substantially in recent years, due to increasing server densities. To avoid the overheating of servers, cooling aisles are over provisioned, but little attention is paid to the actual scenario at the server level. Cooling requirements of the servers is calculated on the basis of fan manufacturer’s published data for the air flow capacity of the server fan and system impedance data obtained from the server designer put together. Thus, the air flow …

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Performance Characteristics Of Single Effect Lithium Bromide/ Water Absorption Chiller For Small Data Centers, Abhishek Arun Babu Mysore Jan 2015

Performance Characteristics Of Single Effect Lithium Bromide/ Water Absorption Chiller For Small Data Centers, Abhishek Arun Babu Mysore

Mechanical and Aerospace Engineering Theses - Archive

A medium data center consists of servers performing operations such as file sharing, collaboration and email. There are a large number of small and medium data centers across the world which consume more energy and are less efficient when compared to large data center facilities of companies such as GOOGLE, APPLE and FACEBOOK. Such companies are making their data center facilities more environmental friendly by employing renewable energy solutions such as wind and solar to power the data center or in data center cooling. This not only reduces the carbon footprint significantly but also decreases the costs incurred over a …

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Chip Package Interaction Study To Analyze The Mechanical Integrity Of A 3-D Tsv Package, Pavan Rajmane Jan 2015

Chip Package Interaction Study To Analyze The Mechanical Integrity Of A 3-D Tsv Package, Pavan Rajmane

Mechanical and Aerospace Engineering Theses - Archive

The convergence and miniaturization of computing and communications dictates building up rather than out. As planar device miniaturization continues to its ultimate limits, the complexity of circuit interconnections for 2-D devices becomes a limitation for performance and drives up power dissipation [1]. As the consumers demand more functions on their hand-held electronic devices, the need for more devices such as memory, CPU and GPU in hand-held type footprints is increasing. Chip-stacking (3-D) is emerging as a powerful tool that satiates such IC package requirements. A 3-D FPGA would overcome the interconnect limitations, resulting in greater silicon efficiency per function (number …

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Experimental Study Of Quaternary Nitrate/Nitrite Molten Salt As Advanced Heat Transfer Fluid And Energy Storage Material In Concentrated Solar Power Plant, Sumeet Changla Jan 2015

Experimental Study Of Quaternary Nitrate/Nitrite Molten Salt As Advanced Heat Transfer Fluid And Energy Storage Material In Concentrated Solar Power Plant, Sumeet Changla

Mechanical and Aerospace Engineering Theses - Archive

Solar energy is used to produce electricity by two methods namely photovoltaic and concentrated solar power plant systems. Concentrated Solar power plants hold a distinct advantage over photovoltaic, which is that of energy storage. Energy can be stored in thermal energy storage system during day time and can be used to dispatch energy during peak demand and during raining or cloudy days to produce electricity. All concentrated solar power plants in operation use sensible heat storage method to store energy. Sensible heat storage system have been used in industry owing to ease of dispatch ability. Currently a binary mixture of …

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Impact Of Viscoelastic Material Characterization Of Pcb's On Thermomechanical Properties Of Qfn Thick Package Under Thermal Cycling, Karthik Rajashekar Jan 2015

Impact Of Viscoelastic Material Characterization Of Pcb's On Thermomechanical Properties Of Qfn Thick Package Under Thermal Cycling, Karthik Rajashekar

Mechanical and Aerospace Engineering Theses - Archive

The QFN component package is a quad flat pack (QFP) with “no-leads”, where the electrical contact to the printed circuit board (PCB) is made through soldering of the lands underneath the package body rather than the traditional leads formed along the perimeter. The popularity of this device package style is primarily due to the superior electrical and thermal performance demonstrated. It is one of the most cutting-edge technologies emerged in the market, exhibiting high performance with unparalleled cost effectiveness. But using thick PCBs (>3mm) is detrimental to the package reliability. The motivation of this work is to understand and …

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Liquid Cooling Of A High-Power Multi-Chip Module Using A Sectioned Cold Plate, Ananthavijayan Sridhar Jan 2015

Liquid Cooling Of A High-Power Multi-Chip Module Using A Sectioned Cold Plate, Ananthavijayan Sridhar

Mechanical and Aerospace Engineering Theses - Archive

With the advancement in micro-fabrication techniques and high performance chips, the heat flux generated through these electronics is reaching a point where air-cooling of these devices is not efficient enough. By definition, Multi-Chip Modules (MCMs) are specialized electronic packages where multiple Integrated-Circuits (ICs) and semiconductor dies are unified onto a single substrate. Increasing advancements in ICs enable MCMs as alternate packaging finding its application in high power electronics like power generation and cooling, medical devices, lasers and, military electronics etc. Hence, liquid cooling techniques are explored as possible solutions. In this study, a high power MCM is considered and, its …

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Comparison Of Modeling Methods For Power Cycle Components Using Supercritical Carbon Dioxide As The Operating Fluid, Joshua Schmitt Jan 2015

Comparison Of Modeling Methods For Power Cycle Components Using Supercritical Carbon Dioxide As The Operating Fluid, Joshua Schmitt

Electronic Theses and Dissertations

Supercritical carbon dioxide as a working fluid in a Brayton power cycle has benefits but also faces unique challenges in implementation. With carbon dioxide, turbomachinery is much more compact and potentially more cost effective. The primary impediments to cycle component performance are the high pressures required to bring the fluid to a supercritical state and the wildly varying fluid properties near the critical point. Simple design models are often used as a quick starting point for modern turbomachinery and heat exchanger design. These models are reasonably accurate for design estimate, but often assume constant properties. Since supercritical carbon dioxide varies …

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Coordinated Optimal Power Planning Of Wind Turbines In A Wind Farm, Puneet Vishwakarma Jan 2015

Coordinated Optimal Power Planning Of Wind Turbines In A Wind Farm, Puneet Vishwakarma

Electronic Theses and Dissertations

Wind energy is on an upswing due to climate concerns and increasing energy demands on conventional sources. Wind energy is attractive and has the potential to dramatically reduce the dependency on non-renewable energy resources. With the increase in wind farms there is a need to improve the efficiency in power allocation and power generation among wind turbines. Wake interferences among wind turbines can lower the overall efficiency considerably, while offshore conditions pose increased loading on wind turbines. In wind farms, wind turbines* wake affects each other depending on their positions and operation modes. Therefore it becomes essential to optimize the …

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A Full Coverage Film Cooling Study: The Effect Of An Alternating Compound Angle, Justin Hodges Jan 2015

A Full Coverage Film Cooling Study: The Effect Of An Alternating Compound Angle, Justin Hodges

Electronic Theses and Dissertations

This thesis is an experimental and numerical full-coverage film cooling study. The objective of this work is the quantification of local heat transfer augmentation and adiabatic film cooling effectiveness for two full-coverage film cooling geometries. Experimental data was acquired with a scientific grade CCD camera, where images are taken over the heat transfer surface, which is painted with a temperature sensitive paint. The CFD component of this study served to evaluate how well the v2-f turbulence model predicted film cooling effectiveness throughout the array, as compared with experimental data. The two staggered arrays tested are different from one another through …

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