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2010

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Articles 451 - 480 of 687

Full-Text Articles in Mechanical Engineering

Experimental Study Of Micro-Vortex Generators At Mach 2.5, Adam J. Pierce Jan 2010

Experimental Study Of Micro-Vortex Generators At Mach 2.5, Adam J. Pierce

Mechanical and Aerospace Engineering Theses - Archive

Vortex generators are geometrical shapes that produce trailing vortices and are widely used for their ability to improve the flow quality over areas where flow separation may occur. Current topics involve utilizing the performance capabilities of vortex generators to influence the boundary layer under supersonic conditions. Such influence may provide an alternative means of reducing boundary layer flow separation and improving the overall quality of the flow in the boundary layer. This influence would maintain low drag in supersonic inlets and reduce the need for mechanical equipment used for boundary layer bleed leading to a reduction in aircraft weight and …

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Experimental Investigation Of Thermal Behaviour Of Air Foil Bearings, Ramesh Pandeshwara Sadashiva Jan 2010

Experimental Investigation Of Thermal Behaviour Of Air Foil Bearings, Ramesh Pandeshwara Sadashiva

Mechanical and Aerospace Engineering Theses - Archive

Micro-turbo machinery demands gas bearings to ensure compactness, lightweight and extreme temperature operation. Gas bearings with large stiffness and damping, and preferably of low cost, will enable successful commercial applications. One of the gas bearing which is used for experimental investigation is the Air foil bearing. Previously developed test rig has been modified and further developed for investigating this bearing at various temperatures and speeds. These gas bearings are self acting hydrodynamic air bearings which have been successfully applied to a variety of turbo machinery applications. This new modified test rig also has the capability to measure bearing torque during …

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Analysis And Design Of A Two-Wheeled Robot With Multiple User Interface Inputs And Vision Feedback Control, Eric Stephen Olson Jan 2010

Analysis And Design Of A Two-Wheeled Robot With Multiple User Interface Inputs And Vision Feedback Control, Eric Stephen Olson

Mechanical and Aerospace Engineering Theses - Archive

This thesis describes the development of a small, inexpensive, controllable mobile two-wheeled robot. It also describes the development of a software interface which allows several open- and closed-loop control methods to be easily implemented. The developed hardware and software modules provide for an open and modular system for research purposes. This is demonstrated through the Bluetooth wireless control of the robot using LabVIEW based software modules. The open-loop control inputs implemented are sliders in a LabVIEW GUI, joystick, and voice commands. The closed-loop control methods included a PD control algorithm that guides the robot to go directly to a user …

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Applications Of Sensitivity Data To Eigensolution Reanalysis Of Modified Structures, Chandrashekhar Sureshchandra Patadia Jan 2010

Applications Of Sensitivity Data To Eigensolution Reanalysis Of Modified Structures, Chandrashekhar Sureshchandra Patadia

Mechanical and Aerospace Engineering Theses - Archive

Methods of computing eigensolution sensitivity have been known for a long time. Both exact and approximate methods are available in the literature. While eigenvalue sensitivity is used routinely in structural optimization with eigenvalue constraints, few application of eigenvector derivatives are reported in the literature. The objective of this thesis is to present an effective eigensolution reanalysis approach using first and second order eigenvector sensitivity data. In the proposed new approach, modes shapes and their derivatives are used as basis vector for eigensolution of the modified system. Comparison of numerical results with several existing eigensolution reanalysis methods shows the proposed algorithms …

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Inverse Design Of Airfoils Using A Flexible Membrane Method, Kamon Thinsurat Jan 2010

Inverse Design Of Airfoils Using A Flexible Membrane Method, Kamon Thinsurat

Mechanical and Aerospace Engineering Theses - Archive

The Modified Garabedian Mc-Fadden (MGM) method is used to inversely design airfoils. The Finite Difference Method (FDM) for Non-Uniform Grids was developed to discretize the MGM equation for numerical solving. The Finite Difference Method (FDM) for Non-Uniform Grids has the advantage of being used flexibly with an unstructured grids airfoil. The commercial software FLUENT is being used as the flow solver. Several conditions are set in FLUENT such as subsonic inviscid flow, subsonic viscous flow, transonic inviscid flow, and transonic viscous flow to test the inverse design code for each condition. A moving grid program is used to create a …

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Effective Thermal Management Of Electronic Devices From System To Die Level, Saket Karajgikar Jan 2010

Effective Thermal Management Of Electronic Devices From System To Die Level, Saket Karajgikar

Mechanical and Aerospace Engineering Dissertations - Archive

In any electronic device, the resistance to the flow of current through the transistors, interconnects, etc. results in a significant heat generation. If this heat is not removed from the device by providing appropriate cooling solutions, the possibility of thermal run away is very high. Under this condition the temperature would continue to rise until it reaches a point at which the device ceases to operate or loses its physical integrity. In presence of a cooling mechanism, the temperature rise is moderated as it asymptotically reaches an acceptable steady state value. Before any device is introduced in the market, it …

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Trajectory Uncertainty Analysis For The Development Of A Queuing Model For The National Airspace System, Manju Nag Jan 2010

Trajectory Uncertainty Analysis For The Development Of A Queuing Model For The National Airspace System, Manju Nag

Mechanical and Aerospace Engineering Theses - Archive

In this research, we propose to support the development of a queuing model for the National Airspace System (NAS) by providing distributions for the various phases of flight, accounting for the uncertainties in flight trajectory which includes factors such as weight, power factor, lift co-efficient. In addition to this, a detailed study is done on the impact of weather on flight routes and two days in 2006 are compared to show the effect of weather on flight times. The research develops from a good understanding of the NAS and its requirements to implement a system capable of dealing with issues …

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Aerodynamic Shape Optimization Of A Vertical Axis Wind Turbine, Travis Justin Carrigan Jan 2010

Aerodynamic Shape Optimization Of A Vertical Axis Wind Turbine, Travis Justin Carrigan

Mechanical and Aerospace Engineering Theses - Archive

The purpose of this study is to introduce and demonstrate a fully automated process for optimizing the airfoil cross-section of a vertical axis wind turbine (VAWT). The objective is to maximize the torque while enforcing typical wind turbine design constraints such as tip speed ratio, solidity, and blade profile. By fixing the tip speed ratio and solidity of the wind turbine, there exists an airfoil cross-section for which the torque can be maximized, requiring the development of an iterative design system.The design system required to maximize torque incorporates rapid geometry generation and automated hybrid mesh generation tools with viscous, unsteady …

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Effect Of Structural Design Parameters On Wafer Level Csp Ball Shear Strength And Their Influence On Accelerated Thermal Cycling Reliability, Nikhil R. Lakhkar Jan 2010

Effect Of Structural Design Parameters On Wafer Level Csp Ball Shear Strength And Their Influence On Accelerated Thermal Cycling Reliability, Nikhil R. Lakhkar

Mechanical and Aerospace Engineering Dissertations - Archive

Wafer level chip scale package (WLCSP) is one of the most popular packages due to its size and cost advantages. It is expected that the usage of WLCSP in microelectronics and MEMS industry combined is going to cross 16000 Million Units by 2013. One of the main advantages of implementing WLCSP is its time to market because most of the package is done at the wafer level. Once the wafer processing is completed the package is just diced and mounted on board and the board is ready to go. However, just like any other package WLCSP too is not ideal …

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Development Of A Multi-Material Stereolithography System, Ho-Chan Kim, Jae-Won Choi, Ryan B. Wicker Jan 2010

Development Of A Multi-Material Stereolithography System, Ho-Chan Kim, Jae-Won Choi, Ryan B. Wicker

Mechanical Engineering Faculty Research

Researchers continue to explore possibilities for expanding additive manufacturing (AM) technologies into direct product manufacturing. One limitation is in the materials available for use in AM that can meet the needs of end-use applications. Stereolithography (SL) is an AM technology well known for its precision and high quality surface finish capabilities. SL builds parts by selectively crosslinking or solidifying photo-curable liquid resins, and the resin industry has been continuously developing new resins with improved performance characteristics. This paper introduces a unique SL machine that can fabricate parts out of multiple SL materials. The technology is based on using multiple vats …

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High School Bridge Program: A Multidisciplinary Stem Research Program, Jiang Zhe, Dennis Doverspike, Julie Zhao, Paul C. Lam, Craig C. Menzemer Jan 2010

High School Bridge Program: A Multidisciplinary Stem Research Program, Jiang Zhe, Dennis Doverspike, Julie Zhao, Paul C. Lam, Craig C. Menzemer

Mechanical Engineering Faculty Research

A Science, Technology, Engineering and Math (STEM) summer Bridge Program was developed for high school students. The program was designed to encourage students to consider choosing an engineering major in college and to explore STEM as a future career. This was accomplished through a 10-week program involving multidisciplinary research activities. The participants in the program included 33 high school students. Among former participants in position to make a choice in terms of attending college, 100% had chosen to continue on in college, and 86% had chosen to major in a STEM area. The results indicated that that the program had …

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Solution To Incompressible Navier Stokes Equations By Using Finite Element Method, Wanchai Jiajan Jan 2010

Solution To Incompressible Navier Stokes Equations By Using Finite Element Method, Wanchai Jiajan

Mechanical and Aerospace Engineering Theses - Archive

The finite element method has become a popular method for the solution of the incompressible Navier-Stokes equations. High Reynolds number cases require fine meshes so computational efficiency becomes an important factor in algorithm and code development. In this work, a Galerkin finite element method is proposed to solve the two dimensional incompressible Navier-Stokes equations. This approach typically leads to a sparse and indefinite matrix that is difficult to solve efficiently. The formation of an indefinite matrix is avoided in the present work by introducing an artificial compressibility term in the continuity equation. The concept of this method is to transform …

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Finite Element Analysis Of Stresses In Involute Spur & Helical Gear, Shreyash D. Patel Jan 2010

Finite Element Analysis Of Stresses In Involute Spur & Helical Gear, Shreyash D. Patel

Mechanical and Aerospace Engineering Theses - Archive

Developing an analytical approach and modeling procedure to evaluate stress distribution under velocity and moment would provide a useful tool to improve spur gear design with high efficiency & low cost. The purpose of this work is to analyze and validate the stress distribution in spur & helical gears using contemporary commercial FEM program ANSYS coupled with the Pro/E solid modeler. Gear profiles are created in Pro Engineer using the Relation and Equation modeling procedure so as to make it a general model, dependant on certain key features like number of teeth, diametral pitch, and pressure and helix angle. These …

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Effects Of Curvature On The Stresses Of A Curved Laminated Beams Subjected To Bending, Thien Nguyen Jan 2010

Effects Of Curvature On The Stresses Of A Curved Laminated Beams Subjected To Bending, Thien Nguyen

Mechanical and Aerospace Engineering Theses - Archive

In aircraft structural applications, curved laminated beam structures are often used as part of the internal structure. If the curved composite structure is subjected to bending that tends to flatten or compress the composite structure, interlaminar stresses can be generated in the thickness direction of the composites. These interlaminar stresses are the major factor of delamination failure. Besides these stresses, the in-plane stresses can be also affected by the pre-existence of the beam curvature. This research has studied the variation of both tangential and radial stresses with respect to the changing in curvature, stacking sequence, and fiber orientation in a …

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A Micromechanics Model Of Thermal Expansion Coefficient In Fiber Reinforced Composites, Nittapon Srisuk Jan 2010

A Micromechanics Model Of Thermal Expansion Coefficient In Fiber Reinforced Composites, Nittapon Srisuk

Mechanical and Aerospace Engineering Theses - Archive

Fiber reinforced composites are widely used for the various applications in the aerospace, automotive, infrastructures and sporting goods industries. The evaluations of its mechanical and thermal properties are needed for accurate estimation of their structural response. In this study, a mathematical closed-form expression of unit cell model was developed to estimate the coefficient of thermal expansion (CTE) along longitudinal and transverse directions of unidirectional lamina. Unlike the previous models, the present model takes into consideration of the fiber configuration and volume fraction of each constituent in the unit cell. In addition, the model is also able to obtain the stresses …

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Dynamic Thermal Management Of Multi Core Processors Using Core Hopping, Avinash Raghu Jan 2010

Dynamic Thermal Management Of Multi Core Processors Using Core Hopping, Avinash Raghu

Mechanical and Aerospace Engineering Theses - Archive

Multi core processors are the order of the day today. The demand for greater levels of performance and the consequent increase in design complexity have rendered the single core processor obsolete and resulted in more cores being put onto a single chip. Processors incorporating more than 4 cores on a chip are dubbed many core processors. This, while improving performance, has lead to increased power densities. Also, the power distribution across the die surface is not uniform. These factors together, result in heat being concentrated at specific points on the die surface, called `hot spots'.The increase in die temperature results …

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Mean Pressure Measurements Of Micro-Vortex Generator At Mach 2.5, Yusi Shih Jan 2010

Mean Pressure Measurements Of Micro-Vortex Generator At Mach 2.5, Yusi Shih

Mechanical and Aerospace Engineering Theses - Archive

Shock wave/boundary layer interactions (SBLIs) are always an important issue for high-speed vehicles. SBLIs reduce the performance of aerodynamic surfaces and engine inlets, amongst a number of adverse effects. Micro-vortex generators (MVGs) are a potential flow control method that has seen intense investigation recently and have even been implemented in actual configurations at low speeds. The present research is focused on the mean pressures at Mach 2.5 around an MVG. Experiments were performed with a baseline flat plate and also with two MVG configurations (70 and 45 trailing edge) mounted ahead of a 5° ramp. In the present study MVGs …

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Axial Wave Propagation In Truncated Cones, Bhumil A. Diwanji Jan 2010

Axial Wave Propagation In Truncated Cones, Bhumil A. Diwanji

Mechanical and Aerospace Engineering Theses - Archive

While dealing with problems of impact analysis, where the force is dependent on the time, one can use the transient analysis to compute the response. Transient wave propagation has drawn interest from a long time mainly because of the way structural members behave when subjected to high rates of loading. Solutions to these problems find applications in the design of various mechanical equipments, or any situation where rigid objects are impacting on structural members.The first part of this study deals with the axial wave propagation in cones of different apex angles using transient analysis in ANSYS. The results from the …

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Fiber-Optic Pressure Sensor For Time-Of-Flight Measurements In A Shock Wave, Karthikeyan Jagadevan Jan 2010

Fiber-Optic Pressure Sensor For Time-Of-Flight Measurements In A Shock Wave, Karthikeyan Jagadevan

Mechanical and Aerospace Engineering Theses - Archive

Fiber-optic sensors are widely employed to detect pressures and temperatures precisely. In particular, MEMS-based Ber-optic sensors are immune to electromagnetic interference but may have limitations at high temperatures as encountered in combustors. To ensure high-temperature survivability, such sensors may be bondedanodically. This project explains the development of a Ber-optic pressure sensor utilizing intensity based principle whereby a fused silica optical window was glued to the tungsten carbide enclosure. The development was estimated to determine high pressures of up to at least 3.5 MPa (507 psi). The sensor is designed to capture the pressure pulse and the time-of-flight (TOF) of a …

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Peak Stress Of Composite Multiple-Hole Laminates With And Without Patch, Sakthivel Selvaraj Jan 2010

Peak Stress Of Composite Multiple-Hole Laminates With And Without Patch, Sakthivel Selvaraj

Mechanical and Aerospace Engineering Theses - Archive

In repairing of composite structures, the damage in the composite laminate is usually removed in the form of circular cutouts which results in holes in the laminate. Then a patch laminate is adhesively bonded to the damaged composite laminate. The presence of holes in any structures creates a high stress concentration at the edge of the hole which indeed reduces the life of the structure. The primary objective of this study is to investigate the high stress of the damaged laminate with different hole patterns and the effect of having single and double patches with various configurations on these hole …

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Computational Model For Transient And Steady State Analysis Of A 1-Dimensional Auto-Thermal Reformer, Srikanth Honavara Prasad Jan 2010

Computational Model For Transient And Steady State Analysis Of A 1-Dimensional Auto-Thermal Reformer, Srikanth Honavara Prasad

Mechanical and Aerospace Engineering Theses - Archive

This study presents a 1-dimensional mathematical model of steam reformer to be used with high temperature solid oxide fuel cell (SOFC). Steam reforming (SR) is widely used in industries to produce hydrogen from hydrocarbons. There are various physical processes associated with chemical reactions in the SR of methane such as mass, heat and momentum transport. In this study a one-dimensional SR reactor with built-in preheater and mixing chamber connected to fuel gas and steam reservoirs is modeled and analyzed. The main part of the reformer is a metallic tube with catalyst coating on the inner walls, and it can be …

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Parameter Estimation In Heat Transfer And Elasticity Using Trained Pod-Rbf Network Inverse Methods, Craig Rogers Jan 2010

Parameter Estimation In Heat Transfer And Elasticity Using Trained Pod-Rbf Network Inverse Methods, Craig Rogers

Electronic Theses and Dissertations

In applied mechanics it is always necessary to understand the fundamental properties of a system in order to generate an accurate numerical model or to predict future operating conditions. These fundamental properties include, but are not limited to, the material parameters of a specimen, the boundary conditions inside of a system, or essential dimensional characteristics that define the system or body. However in certain instances there may be little to no knowledge about the systems conditions or properties; as a result the problem cannot be modeled accurately using standard numerical methods. Consequently, it is critical to define an approach that …

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Experimental Studies Of The Heat Transfer Characteristics Of Silica Nanoparticle Water-Based Dispersion In Pool Boiling Using Nichrome Flat Ribbons And Wires, Diane Marie Vazquez Jan 2010

Experimental Studies Of The Heat Transfer Characteristics Of Silica Nanoparticle Water-Based Dispersion In Pool Boiling Using Nichrome Flat Ribbons And Wires, Diane Marie Vazquez

Electronic Theses and Dissertations

This work deals with a study of enhanced critical heat flux (CHF) and burnout heat flux (BHF) in pool boiling of water with suspended silica nanoparticles using ribbon-type and wire heaters. Previously our group and other researchers have reported three-digit percentage increase in critical heat flux in silica nanofluids. This study investigates the effect of various heater surface dimensions and cross-sectional shapes on pool boiling heat transfer characteristics of water and water-based nanofluids. CHF and BHF were analyzed for circular and rectangular cross-section nichrome wires and ribbons of increasing sizes in the range of 0.32mm to 2.38mm width, approaching a …

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High Heat Flux Spray Cooling With Ammonia On Enhanced Surfaces, Huseyin Bostanci Jan 2010

High Heat Flux Spray Cooling With Ammonia On Enhanced Surfaces, Huseyin Bostanci

Electronic Theses and Dissertations

Many critical applications today, in electronics, optics and aerospace fields, among others, demand advanced thermal management solutions for the acquisition of high heat loads they generate in order to operate reliably and efficiently. Current competing technologies for this challenging task include several single and two phase cooling options. When these cooling schemes are compared based on the high heat flux removal (100-1000 W/cm2) and isothermal operation (within several oC across the cooled device) aspects, as well as system mass, volume and power consumption, spray cooling appears to be the best choice. The current study focused on high heat flux spray …

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A Model Integrated Meshless Solver (Mims) For Fluid Flow And Heat Transfer, Salvadore Gerace Jan 2010

A Model Integrated Meshless Solver (Mims) For Fluid Flow And Heat Transfer, Salvadore Gerace

Electronic Theses and Dissertations

Numerical methods for solving partial differential equations are commonplace in the engineering community and their popularity can be attributed to the rapid performance improvement of modern workstations and desktop computers. The ubiquity of computer technology has allowed all areas of engineering to have access to detailed thermal, stress, and fluid flow analysis packages capable of performing complex studies of current and future designs. The rapid pace of computer development, however, has begun to outstrip efforts to reduce analysis overhead. As such, most commercially available software packages are now limited by the human effort required to prepare, develop, and initialize the …

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Processing, Optimization And Characterization Of Fire Retardant Polymer Nanocomposites, Jinfeng Zhuge Jan 2010

Processing, Optimization And Characterization Of Fire Retardant Polymer Nanocomposites, Jinfeng Zhuge

Electronic Theses and Dissertations

Fiber reinforced polymeric composites (FRPC) have superior physical and mechanical properties, such as high specific strength, light weight, and good fatigue and corrosion resistance. They have become competitive engineering materials to replace conventional metallic materials in many important sectors of industry such as aircraft, naval constructions, ships, buildings, transportation, electrical and electronics components, and offshore structures. However, since FRPC contain polymer matrix, the polymer composites and their structures are combustible. FRPC will degrade, decompose, and sometimes yield toxic gases at high temperature or subject to fire conditions. The objective of this study is to design and optimize fire retardant nanopaper …

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Alternative Cooling Technologies For Telecommunication Data Centers: Air Cooling And Rear Door Heat Exchangers, Venkata Naga Poornima Mynampati Jan 2010

Alternative Cooling Technologies For Telecommunication Data Centers: Air Cooling And Rear Door Heat Exchangers, Venkata Naga Poornima Mynampati

Mechanical and Aerospace Engineering Theses - Archive

Telecommunication industry is currently emphasizing to a miniaturization and convergence. The need for smaller, smarter and faster devices is leading drastic increment in power density and accordingly, thermal management of such devices has become a challenge. The heat generated by the devices has to be dissipated in order to ensure proper and efficient functioning of the electronics. Electronics cooling ranges from device level to the room level cooling. Data Center is a facility (room) consisting of servers used for managing and transferring data or information. The thermal management of this facility is challenging due to the huge decrease in floor …

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Macroinstability And Perturbation In Turbulent Stirred Tank Flows, Somnath Roy Jan 2010

Macroinstability And Perturbation In Turbulent Stirred Tank Flows, Somnath Roy

LSU Doctoral Dissertations

Impeller stirred tank reactors (STRs) are commonly used in the chemical processing industries for a variety of mixing and blending technologies. In this research, a numerical study of flow and mixing inside turbulently agitated STRs are carried out. An immersed boundary method (IBM) is utilized to represent moving impeller geometries in the background of multi-block structured curvilinear fluid. The IBM This curvilinear-IBM methodology is further combined with the large eddy simulation (LES) technique to address the issue of modeling unsteady turbulent flows in the STR. Verification of the combined IBM-LES implementation strategy in curvilinear coordinates is done through comparisons with …

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Uncertainty Analysis And Instrument Selection Using A Web-Based Virtual Experiment, Praveen Malali, Pooja Bais, Robert Choate, Sushil Chaturvedi Jan 2010

Uncertainty Analysis And Instrument Selection Using A Web-Based Virtual Experiment, Praveen Malali, Pooja Bais, Robert Choate, Sushil Chaturvedi

Mechanical & Aerospace Engineering Faculty Publications

A methodology has been developed and successfully implemented for transforming physical experiments in an undergraduate thermo-fluids laboratory at Old Dominion University (ODU), a doctoral university, into web-based virtual experiments while the Mechanical Engineering (ME) faculty at Western Kentucky University (WKU), an undergraduate university, have developed and implemented a Design of Experiments (DOE) Plan to assure that graduates of their program have acquired the skills necessary to design and conduct experiments and analyze experimental results. This paper presents details about a web-based virtual experiment designed to teach students about selection of instruments based on the uncertainty estimated from the virtual experiment. …

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Formula Sae Impact Attenuator Testing, Chad Abrahamson, Bill Bruns, Joseph Hammond, Josh Lutter Jan 2010

Formula Sae Impact Attenuator Testing, Chad Abrahamson, Bill Bruns, Joseph Hammond, Josh Lutter

The Journal of Undergraduate Research

The purpose of this paper is to validate the impact attenuator designed by SDSU Formula SAE team according to 2010 Formula SAE rules. The impact attenuator is made of Plascore PCGA-XR1-5.2-1/4-P-3003 aluminum honeycomb that is pre-crushed to 245 psi. The test was dynamically performed using a 661 lb mass dropped 8.3 ft onto the material sample at 23 ft/sec, and data was measured with an Olympus i-SPEED 3 high speed camera. The impact attenuator must have an average deceleration equal to or less than 20 G’s and a peak deceleration equal to or less than 40 G’s. Two specimens were …

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