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Articles 691 - 720 of 953
Full-Text Articles in Aerospace Engineering
Gaseous Corrosion In Hard Disk Drive: A Computational Study, Hardik Shah
Gaseous Corrosion In Hard Disk Drive: A Computational Study, Hardik Shah
Mechanical and Aerospace Engineering Theses - Archive
HDD is the largest digitally encoded data storage device. HDD is used to store digital data in data centers, computers and laptops. A typical HDD consists of a casing, an actuator arm, actuator axis, head, platters, power connectors, and jumper pins. The platter is made up of non-magnetic material and is covered by magnetic material, which stores the data. The magnetic heads are mounted on a moving actuator arm to read and write the data. One of the modes of failure of a HDD is corrosion. The parts of the HDD are corroded by coming in contact with the contaminants. …
Chemoelastoplastic Analysis Of A Copper-Graded Silicon Nanorod For Lithium-Ion Battery Anode Application, Chao Ji
Mechanical and Aerospace Engineering Theses - Archive
Lithium-ion batteries are currently widely used in electronics, electrical vehicles and other devices/machines. Along with the mounting demand for much improved performance in these developing technological fields, silicon was recognized to possess much higher energy capacity when used as an anode than graphite that is currently used. However, there occurs colossal volume expansion of silicon anode during the lithiation process. The material consequently suffers enormous stresses, especially, at the interface with a current collector, which deteriorate the device quickly during cycling. To prevent the active material (Si) from falling off from a current collector, nanoengineering strategies have been suggested, including …
Application Of Phase Change Material In Sustainable Cooling Of Data Centers, Nikhil Dhiman
Application Of Phase Change Material In Sustainable Cooling Of Data Centers, Nikhil Dhiman
Mechanical and Aerospace Engineering Theses - Archive
The ever increasing information technology heat load and data center cooling energy are the main reasons to investigate the performance of microencapsulated phase change slurry over other heat transfer fluids. In recent years, more effort is being made on the development of a new technique to use the phase change materials as pump-able heat transfer fluid and as heat storage system.Microencapsulated phase change slurry is dispersion where the phase change material, microencapsulated by a polymeric capsule, is dispersed in water. Compared to water, these new fluids have a higher heat capacity during phase change and a possible enhancement, as a …
Thermal Management Method For Foil Bearings In Turbine Hot Section, Tejas Devidas Patil
Thermal Management Method For Foil Bearings In Turbine Hot Section, Tejas Devidas Patil
Mechanical and Aerospace Engineering Theses - Archive
Recently, Air Foil Bearings (AFB) are gaining higher industrial acceptance in micro-turbo machinery. AFB show high speed operating capability and environmental friendly operation in comparison to rolling element bearings. Utilization of ambient air as a lubricant eliminates maintenance of a pressurized oil lubricating system. AFBs are therefore a feasible alternative to oil lubricated bearings in small machines. High speed operation results in thermal management issues which can be solved through a suitable cooling mechanism. Axial cooling by passing air through bearing support structure (called bump foils) is the most commonly used. In this method, cooling is achieved in the heat …
Immersion Cooling Of High End Data Center Server And Validation Through Experiments, Harsh Patel
Immersion Cooling Of High End Data Center Server And Validation Through Experiments, Harsh Patel
Mechanical and Aerospace Engineering Theses - Archive
Despite recent improvements in data center cooling efficiency such as hot and cold aisle and air side economizer, air cooling may not have the capacity to cool high end racks such as from IBM's NetBAY42 (150Kw and above). Increasing computer capabilities in data center has resulted in increase in rack power density per square ft as indicated by the latest uptime. The cooling of such high powered servers and corresponding racks poses a significant challenge to thermal engineers.The use of immersion cooling is novel approach for data center cooling. In this study after some modification high powered server is fully …
A Numerical Study Of Incompressible Fluid Flow Over A Forward Facing Step At Various Grades, Peter Andrew Martinez
A Numerical Study Of Incompressible Fluid Flow Over A Forward Facing Step At Various Grades, Peter Andrew Martinez
Mechanical and Aerospace Engineering Theses - Archive
The study of the effect of natural forces on hydraulic structures is of great concern for the accurate prediction of when a design could be at risk of failure. In recent times the use of the shallow water equations to predict the behavior of the free surface for flow over a step has proven inaccurate because only a hydrostatic pressure distribution is considered. One of the phenomena that will not be accounted for with the shallow water equations in such a setup is the formulation of undular bore type waves on the surface. In order for a more accurate representation …
Design, Fabrication And Test Of Surface Tension-Driven Microboats And Thermally Oscillatory Bubble-Propelled Microsubmarines, Lei Qiao
Mechanical and Aerospace Engineering Dissertations - Archive
In this work, we develop microboats and microsubmarines, which are capable of moving on and under water, respectively. The microboat is propelled due to the difference between surface tensions around stern and bow. This difference is generated by releasing a liquid with lower surface tension than water from the stern. We explore both horizontal and vertical motions of the microboats through a combination of experimental and theoretical investigations. It has a length of 8 mm and weight of 20 mg with the highest speed of 25 cm/s and travel distance of 85 cm. Moreover, we design, fabricate and test microboats …
Passive Wireless Antenna Sensors For Crack Detection And Shear/Compression Sensing, Irshad Mohammad
Passive Wireless Antenna Sensors For Crack Detection And Shear/Compression Sensing, Irshad Mohammad
Mechanical and Aerospace Engineering Dissertations - Archive
Despite the fact that engineering components and structures are carefully designed against fatigue failures, 50 to 90% of mechanical failures are due to fatigue crack formation. The severity of the failure depends on both the crack length and its orientation with respect to the loading direction. Many types of sensors are available that can detect fatigue crack propagation. But, crack orientation detection has been rarely reported in the literature. We evaluated a patch antenna sensor capable of detecting crack propagation as well as crack orientation changes. The aim of the sensors would be to evaluate the real-time health condition of …
Illustration Of Fundamentals Of Mechanical Vibration Using Computable Document Format, Shiva Deshmukh
Illustration Of Fundamentals Of Mechanical Vibration Using Computable Document Format, Shiva Deshmukh
Mechanical and Aerospace Engineering Theses - Archive
The main objective of this study is focused on the better understanding of the basic concepts of mechanical vibrations and its free and ready availability to the entire student community all over the globe.In this study the concepts of vibrations are projected in the form of mathematical models. The mathematical models are designed using MATHEMATICA. These models are graphical in nature and can be animated at will. They are compiled and converted to the Computable Document Format referred as CDF.A very special function Manipulate is used in making the models. This function has given the models an ability to compute …
Graph Theoretic Framework Based Cooperative Control And Estimation Of Multiple Uavs For Target Tracking, Mousumi Ahmed
Graph Theoretic Framework Based Cooperative Control And Estimation Of Multiple Uavs For Target Tracking, Mousumi Ahmed
Mechanical and Aerospace Engineering Dissertations - Archive
Designing the control technique for nonlinear dynamic systems is a significant challenge. Approaches to designing a nonlinear controller are studied and an extensive study on backstepping based technique is performed in this research with the purpose of tracking a moving target autonomously. Our main motivation is to explore the controller for cooperative and coordinating unmanned vehicles in a target tracking application.To start with, a general theoretical framework for target tracking is studied and a controller in three dimensional environment for a single UAV is designed. This research is primarily focused on finding a generalized method which can be applied to …
Lumped Parameter Modeling Of Fluid Line Dynamics With Turbulent Flow Conditions, Yi-Wei Huang
Lumped Parameter Modeling Of Fluid Line Dynamics With Turbulent Flow Conditions, Yi-Wei Huang
Mechanical and Aerospace Engineering Dissertations - Archive
A procedure for obtaining rational polynomial transfer functions representing ordinary differential equations for time domain transient response simulations of systems with fluid transmission lines with incompressible turbulent flow is formulated and presented. The method is based on the use of an inverse frequency least squares algorithm applied to the distributed parameter model for laminar flow with added lumped resistance to match the additional resistance associated with turbulence. Guidelines for using the algorithm are included with focus on the use of weighting parameters, the number of resonant modes to be included, and the bandwidth of the pressure/flow pulsation dynamics in the …
Solution To Three Dimensional Incompressible Navier-Stokes Equations Using Finite Element Method, Shrinivas Ganesh Apte
Solution To Three Dimensional Incompressible Navier-Stokes Equations Using Finite Element Method, Shrinivas Ganesh Apte
Mechanical and Aerospace Engineering Theses - Archive
A primitive variable mixed order formulation of finite element method for solving three dimensional incompressible Navier-Stokes equations is presented. The method of weighted residuals is used to obtain the approximate solutions of linear and nonlinear partial differential equations. The physical domain is discretized by using unstructured tetrahedral elements. Unequal order interpolation functions are used for pressure & velocity variables while the temporal discretization is carried out by using an implicit time marching scheme based on finite differencing.One of the major difficulties arising during the finite element solution of the incompressible Navier-Stokes equations is the efficient factorization/preconditioning of the resulting indefinite …
High Enthalpy Characterization Of The Uta Hypersonic Shock Tunnel, Raheem Temitope Bello
High Enthalpy Characterization Of The Uta Hypersonic Shock Tunnel, Raheem Temitope Bello
Mechanical and Aerospace Engineering Theses - Archive
In hypersonic wind tunnel testing, matching the flow enthalpy conditions for the hypersonic air-breathing corridor is of great importance in order to assure the validity of experimental results. The flow enthalpy of the UTA hypersonic shock tunnel is increased by a shock induced detonation driver. The detonation mixture consist of hydrogen and oxygen in stoichiometric quantities ( 2H2+O2 ? 2H2O). Experimental variations of pressure and the volume of the detonation section were performed to characterize the enthalpy limits, and overall performance of the UTA hypersonic shock tunnel. The UTA HST test section is designed for a nominal Mach number of …
Experimental And Numerical Investigation Of Mass Transfer In Microreactors, Wei-Tsen Han
Experimental And Numerical Investigation Of Mass Transfer In Microreactors, Wei-Tsen Han
Mechanical and Aerospace Engineering Dissertations - Archive
In this work, two types of microreactors for reactions have been studied, which were involving multiple fluid phases: liquid-liquid (immiscible liquids) phase and gas-liquid phase. Investigation of mass transfer within reacting flows in microreactors has been carried out in these two multiphase systems. For the liquid-liquid phase, a microfluidic system was designed and fabricated to generate a slug flow pattern of immiscible liquids. This system was used to demonstrate the effect of the flow pattern on mass transfer and the effect on chemical reaction rate for a simple acid-base reaction. The reaction progression was tracked by measuring the pH along …
Experimental Identification Of Force Coefficients Of Hybrid Air Foil Bearings, Yu Ping Wang
Experimental Identification Of Force Coefficients Of Hybrid Air Foil Bearings, Yu Ping Wang
Mechanical and Aerospace Engineering Theses - Archive
Successful applications for air foil bearings in small to midsize turbo-machinery have been acknowledged. Air foil bearings do not require oil lubricant thus they are capable of operating under much higher temperature than oil-lubricated bearings and they entail less maintenance costs if well-designed. However, when rotor size increases beyond 100 mm in diameter, reliability becomes an issue due to comparable increase in rotor weight with respect to increase in load capacity of the bearing. Furthermore, dry rubbing during starts and stops also causes concerns due to typical slow acceleration and deceleration characteristics of large turbo-machinery. The concept of hybrid air …
Experimental Feasibility Study Of Radial Injection Cooling Of Three-Pad Radial Air Foil Bearings, Suman K. Shrestha
Experimental Feasibility Study Of Radial Injection Cooling Of Three-Pad Radial Air Foil Bearings, Suman K. Shrestha
Mechanical and Aerospace Engineering Theses - Archive
Air foil bearings use ambient air as a lubricant allowing environment-friendly operation. When they are designed, installed, and operated properly, air foil bearings are very cost effective and reliable solution to oil-free turbomachinery. Because air is used as a lubricant, there are no mechanical contacts between the rotor and bearings and when the rotor is lifted off the bearing, near frictionless quiet operation is possible. However, due to the high speed operation, thermal management is one of the very important design factors to consider. Most widely accepted practice of the cooling method is axial cooling, which uses cooling air passing …
Thermal Behavior Of Dielectric Materials During Rapid Heating, Daipayan Sarkar
Thermal Behavior Of Dielectric Materials During Rapid Heating, Daipayan Sarkar
Mechanical and Aerospace Engineering Theses - Archive
The objective of this research is to understand the temperature variation in dielectric materials of different geometry. The work is divided into three major segments. The Thermal Wave model has been taken into consideration as the classical Fourier law of heat conduction breaks down when a dielectric material of sub-micron geometry is heated rapidly. The first partof the work discusses primarily about the temperature distribution in a semi-infinite dielectric material, followed by the temperature profile in a finite body (plate) and finally mathematical formulation is presented for a two-layered body. The thermal wave equation is used because in dielectric materials …
Mitigation Of Hot-Spots In High-End Microprocessors Using Bulk And Thin Film Thermoelectric Coolers, Agat Hirachan
Mitigation Of Hot-Spots In High-End Microprocessors Using Bulk And Thin Film Thermoelectric Coolers, Agat Hirachan
Mechanical and Aerospace Engineering Theses - Archive
Due to localized high heat fluxes, hot-spots are created in silicon chips. Cooling of the hot-spots is one of the major thermal challenges in today's integrated circuit (IC) industry. Many researches have been conducted to find ways to cool hot-spots using different techniques as uniform heating is highly desired. First part of the thesis focuses on cooling of hot-spot using conventional thermoelectric cooler (Melcor_CP1.0-31-05L.1) and a micro heat pipe. A chip package with conventional integrated heat spreader and heat sink was designed. Hot-spot was created at the center of the silicon die with background heat at rest of the area. …
Dynamic Performance Of Offset-Preloaded Two Pad Foil Bearings, Shrikant Ashok Yadav
Dynamic Performance Of Offset-Preloaded Two Pad Foil Bearings, Shrikant Ashok Yadav
Mechanical and Aerospace Engineering Theses - Archive
Commercial application of the air foil bearing (AFB) in microturbomachinary have been acknowledged. Absence of external pressurizing and lubricating system makes them light and compact. Simple construction, low friction drag and reliability at high speed operations are few more advantages of the AFBs. With all these advantages AFB proves to be the suitable option for oil-free small turbomachinery which includes micro gas turbines with shaft power less than 1000hp. Micro gas turbine generators are typically two shaft configuration with power generation capacity less than 500KW. Although many micro gas turbines with AFBs have been developed, due to the proprietary nature …
Dynamic Mode Decomposition Of Detonation Waves, Rahul Kumar
Dynamic Mode Decomposition Of Detonation Waves, Rahul Kumar
Mechanical and Aerospace Engineering Theses - Archive
Dynamic mode decomposition is applied to study the self-excited fluctuations supported by transversely unstable detonations. The focus of this study is on the effect of forcing on the limit cycle solutions. Using DMD, only the most coherent modes are analyzed. The most coherent modes in this case are the fundamental and the fourth harmonic. The analysis is based on the coherency of the self-excited detonation modes due to turbulence. Analysis reveals coherency is significantly affected with a turbulent Mach number greater than 0.3 and also the regions downstream of the shock are more affected by turbulence than the region just …
Trajectory Generation And Constrained Control Of Quadrotors, Carlos Alberto Tule
Trajectory Generation And Constrained Control Of Quadrotors, Carlos Alberto Tule
Mechanical and Aerospace Engineering Theses - Archive
Unmanned Aerial Systems, although still in early development, are expected to grow in both the military and civil sectors. As part of the UAV sector, the quadrotor helicopter platform has been receiving a lot of interest from various academic and research institutions because of their simplistic design and low cost to manufacture, yet remaining a challenging platform to control. Four different controllers were derived for the trajectory generation and constrained control of a quadrotor platform. The rst approach involves the linear version of the Model Predictive Control (MPC) algorithm to solve the state constrained optimization problem. The second approach uses …
Stress Analysis In Curved Composite Due To Thermal Loading, Jared Cornelius Polk
Stress Analysis In Curved Composite Due To Thermal Loading, Jared Cornelius Polk
Mechanical and Aerospace Engineering Theses - Archive
Many structures in aircraft, cars, trucks, ships, machines, tools, bridges, and buildings, consist of curved sections. These sections vary from straight line segments that have curvature at either one or both ends, segments with compound curvatures, segments with two mutually perpendicular curvatures or Gaussian curvatures, and segments with a simple curvature. With the advancements made in multi-purpose composites over the past 60 years, composites slowly but steadily have been appearing in these various vehicles, compound structures, and buildings. These composite sections provide added benefits over isotropic, polymeric, and ceramic materials by generally having a higher specific strength, higher specific stiffnesses, …
Using Gpu-Based Computing To Accelerate Finite Element Problems, Jacob Watt
Using Gpu-Based Computing To Accelerate Finite Element Problems, Jacob Watt
Mechanical and Aerospace Engineering Theses - Archive
Historically Graphics Processing Units (GPU) have been used for offloading graphical visualization and made popular in use for video games, but with the development of NVIDIA's CUDA architecture and programing language there has been an increase in the use of GPUs in general purpose (GPGPU) programing. Problems involving large systems of linear equations, such as the Finite Element Analysis (FEA), can benefit greatly from the parallel computing capabilities of GPUs. In my thesis I will solve Poisson's equation and discuss the advantages and disadvantages of the massively parallel environment of GPUs. I will show that on a unstructured grid that …
Determination Of Factors To Improve Effectiveness Of Triangulation Members For A Formula Sae Race Car Frame, Vikram Nair
Determination Of Factors To Improve Effectiveness Of Triangulation Members For A Formula Sae Race Car Frame, Vikram Nair
Mechanical and Aerospace Engineering Theses - Archive
This thesis suggests which factors have significant effect on the torsional and flexural stiffness of a space frame without contributing excessively to its weight. These factors are used as design variables to display the interaction plots generated by performing a Design of Experiments (DOE) using the Hyperstudy tool in Hyperworks by Altair®. The DOE will also provide a mathematical model which can help predict the responses by varying several factors in the design. The node - element models are created in ANSYS classic and are analyzed for various load cases that are representative of the loads on a formula SAE …
Characterization Of Uta Hypersonic Shock Tunnel, Derek Glenn Leamon
Characterization Of Uta Hypersonic Shock Tunnel, Derek Glenn Leamon
Mechanical and Aerospace Engineering Theses - Archive
Characterization of a hypersonic shock tunnel was performed under low enthalpy conditions. A rake was designed and fabricated to measure pitot pressure and heat flux at three axial locations in the test section. Pitot pressures at three locations provided an indication of the inviscid core. Thin film RTD sensors with a fast response time were fabricated to measure the heat flux under these low enthalpy conditions. The Cook-Felderman algorithm was used to estimate the heat flux from the temperature history. Results for the first millisecond of test time showed a probe tip surface temperature increase of 15-20 K and a …
Computational Study Of Heat Transfer Enhancement For A Dimpled Surface In A Channel, Abhijit Paranjape
Computational Study Of Heat Transfer Enhancement For A Dimpled Surface In A Channel, Abhijit Paranjape
Mechanical and Aerospace Engineering Theses - Archive
Heat transfer augmentation techniques have gained great importance in different engineering applications to deal with thermal management issues. In this work, a numerical investigation was carried out to see the effects of spherical dimple arrays on heat transfer characteristics in a channel. These effects were observed for dimples on the bottom wall of the channel for laminar airflows. The effects of a 21×7 staggered array and a 19×4 inline array on the bottom wall were investigated using a 3D steady viscous computational fluid dynamics package with an unstructured grid. The heat transfer characteristics were studied as a function of the …
Spur Gear Analysis Using Mathcad, Jaydeep K. Panchal
Spur Gear Analysis Using Mathcad, Jaydeep K. Panchal
Mechanical and Aerospace Engineering Theses - Archive
In gear manufacturing applications, it is required to calculate surface stress and bending stress with minimum error. This thesis represents engineering calculation of bending and surface compression of external teethed involute spur gear. One may change the input values to calculate the engineering data for gears. The freedom of changing input values gives the capability to program to calculate for factor, Y; and the bending geometry factor, J to analyze spur gear geometry. Here the engineering gear calculation has been done by developing program in Mathcad software. The program is designed to calculate surface and bending stress data by input …
Torsional Analysis Of A Composite I-Beam, Vishal Mukesh Smita Sanghavi
Torsional Analysis Of A Composite I-Beam, Vishal Mukesh Smita Sanghavi
Mechanical and Aerospace Engineering Theses - Archive
A simple methodology for analysis of thin walled composite I-Beam subjected to free torsion and restrained torsion is developed. Classical Lamination Theory is extended from the laminate level to the structural level for analysis purpose.The developed expressions for shear center, equivalent torsional rigidity and equivalent warping rigidity for a composite mono-symmetric I-Beam depends on the material properties, ply stacking sequence, fiber orientation and geometryThe results from the proposed theory gives better agreement with the ANSYSTM results than the traditional smeared property approach.
Control Of A Teleoperating Robotic Arm Subject To Time Delays, Pankaj Prakash Sarda
Control Of A Teleoperating Robotic Arm Subject To Time Delays, Pankaj Prakash Sarda
Mechanical and Aerospace Engineering Theses - Archive
Robotics in Minimally Invasive Surgeries (MIS) can be explored to its full potential if there is complete transparency between the surgeon and the virtual environment. In the setup, haptic device which conveys force from the surgeon to the surgery site and vice verse acts as the master station and robotic arm at the surgery site acts as the slave robot. In surgeries carried out remotely, time delays in the communication channels can cause commanded velocity/force to overshoot before the surgeon can even pull out during a task causing temporary or permanent damage during the surgery. Since the physical capability of …
Study Of The Surface Roughness Evolution In Fatigued 316l Stainless Steel, Ye Wang
Study Of The Surface Roughness Evolution In Fatigued 316l Stainless Steel, Ye Wang
Mechanical and Aerospace Engineering Theses - Archive
Fatigue is a critical design consideration in many aerospace structures. As improvements are sought in overall performance, maintenance requirements, and total service life of modern aircrafts, the demands for fatigue control techniques, such as material design for fatigue resistance, reliable fatigue life prediction, and continuous material damage monitoring, have increased. The most common practices to ensure fatigue safety include: fracture mechanics based fatigue life prediction, periodic non-destructive inspections, and material processing control. Reasonable successes have been achieved by applying these three techniques to ensure the safe operation of aerospace structures. It is worth mentioning that most of the present fatigue …