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Title: CHARACTERIZATION OF A CHROMIUM VANADIUM STEEL IN A HAND TOOL APPLICATION
Creator: Cease, Herman
Date: 2011-04-23, 2011-05
Description: A chromium vanadium steel is characterized for use in a hex wrench hand tool application. The application justi es the need for a high...
Show moreA chromium vanadium steel is characterized for use in a hex wrench hand tool application. The application justi es the need for a high strength and ductile steel. The standard steel alloy used for hex wrenches is 8650. An alternative lower cost steel alloy, 61B60CrV, is considered for the hex wrench hand tool application. The microstructure achieved is tempered martensite. First martensite is formed to create a high strength but brittle material. Then the martensite is reheated and tem- pered to improve the ductility of the material. Both 8650 and 61B60CrV alloys are thermally processed in the same way to create the tempered martensitic structure. The mechanical properties of the proposed steel is evaluated and compared to that of the standard 8650 steel alloy. The 61B60CrV alloy evaluation includes torsion test- ing, hardness and hardenability measurements, and grain size determination. The 61B60CrV alloy is proven to meet the hex wrench hand tool mechanical requirements with a tempered martensitic microstructure. During Jominy hardness testing of the 61B60CrV alloy, it is determined that the hardness requirements are met for a wide range of microstructures. Samples of the 61B60CrV alloy are austempered for di er- ent durations then quenched to room temperature to create samples with di erent amounts of mixed microstructures of bainite and martensite. A range of mixed mi- crostructures are shown to meet the strength, ductility, and hardness requirements for the hex wrench hand tool application without tempering.
Ph.D. in Material Science and Engineering, May 2011
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Title: SIMULATION OF CENTERLINE DEFECT CLOSURE IN OPEN DIE FORGING
Creator: Zhou, Jie
Date: 2012-11-11, 2012-12
Description: Open die forging technique is mainly used to achieve desired product shape and refine the product mechanical quality. Large ingots tend to...
Show moreOpen die forging technique is mainly used to achieve desired product shape and refine the product mechanical quality. Large ingots tend to have internal defects such as shrinkage cavities and porosity, which have to be closed during the primary forging stage to ensure sound internal quality of forged parts. In this work, the finite element method was used to simulate the open die forging process, varying different process parameters that affect the void closure behavior profoundly. Numerical models were constructed in FORGE 2011® using practical forging parameters and material rheological data obtained experimentally from Gleeble compression tests. Forging variables including die design, operational practice and boundary conditions were studied thoroughly. Parameters such as die width, die geometry, die overlap, reduction amount per pass were studied with intense attention paid on the specific mechanical properties of H13 steel, so that this study can be applied to solve real world problems. Also, the temperature gradient and friction condition between billet and die were investigated. Physical experiment validation was carried out with a miniature billet sample. The experiment results were compared with the simulations, showing there was good agreement between the two, giving confidence to the simulation results. Based on the simulation results the optimum forging parameters were proposed to ensure full closure of internal defects.
M.S. in Materials Science and Engineering, December 2012
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Title: IMPROVEMENT OF VERTICAL-AXIS WIND TURBINE PERFORMANCE VIA TURBINE COUPLING
Creator: Mehrpooya, Payam
Date: 2014, 2014-07
Description: While vertical-axis wind turbines (VAWTs) have a simpler design than the horizontal-axis wind turbines, their development has been hindered...
Show moreWhile vertical-axis wind turbines (VAWTs) have a simpler design than the horizontal-axis wind turbines, their development has been hindered due to their unsteady aerodynamics and complex flow field. In this thesis, a parameterized study is conducted to simulate a baseline VAWT using STAR-CCM+, a commercial finite volume code. A hybrid grid scheme, with structured prism layer mesh at the surface of the blades, is used to properly resolve the turbulent boundary layers on the blades. The flow was highly unsteady due to the rotating geometries. Thus, a sliding mesh technique is implemented at the interface of rotating and stationary zones. The dominant factors limiting the performance of the VAWTs are investigated for a range of moderate tip speed ratios, by visualizing the flow field and modeling the individual blade aerodynamics. The VAWT aerodynamics is shown to be dominated by the dynamic stall, at low tip speed ratios, and by the blade-wake interactions and the wake blockage effects, at high tip speed ratios. The concept of turbine coupling is used to improve the performance of the VAWTs by their internal aerodynamic interactions. Two counter-rotating turbines are placed in close proximity, and simulated over the same range of tip speed ratios as before, and for a set of different spacing between them. The effects of spacing and the tip speed ratio on their overall power output and their wake recovery characteristics are then investigated. A cluster of turbines with spacing equal to 1.50 turbine diameters and tip speed ratio of three is shown to have the quickest wake recovery and highest power enhancement, increasing the turbine average power coefficient by 22%.
M.S. in Mechanical and Aerospace Engineering, July 2014
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Title: Relative hazards of nitrates and chlorates
Creator: Arnold, Charles Harry
Date: 2009, 1913
Publisher: Armour Institute of Technology
Description: http://www.archive.org/details/relativehazardso00arno
Thesis (B.S.)--Armour Institute of Technology

Title: DYNAMIC LIFT FORCE MEASUREMENTS ON A 2-D WING AND COMPARISONS WITH UNSTEADY AERODYNAMIC MODELS
Creator: Buntain, Seth
Date: 2011-11-27, 2011-12
Description: Experiments were conducted to collect dynamic force measurements on a pitching wing using canonical motions. Aerodynamic forces were isolated...
Show moreExperiments were conducted to collect dynamic force measurements on a pitching wing using canonical motions. Aerodynamic forces were isolated from inertia based forces to facilitate Observer Kalman Identification model building. Comparisons with classical unsteady aerodynamic theories show good agreement when their assumptions are maintained, with smokewire visualization to qualitatively explain where experiments deviate from theory. A reduced order model built using OKID was compared to experimental data, and showed better agreement than classical theories. Oscillations in the lift measurements were observed in the OKID model and experimental data, and some potential sources for the oscillations were ruled out.
M.S. in Mechanical and Aerospace Engineering, December 2011
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Title: HIGH ENERGY SODIUM BASED ROOM TEMPERATURE FLOW BATTERIES
Creator: Shamie, Jack
Date: 2015, 2015-12
Description: As novel energy sources such as solar, wind and tidal energies are explored it becomes necessary to build energy storage facilities to load...
Show moreAs novel energy sources such as solar, wind and tidal energies are explored it becomes necessary to build energy storage facilities to load level the intermittent nature of these energy sources. Energy storage is achieved by converting electrical energy into another form of energy. Batteries have many properties that are attractive for energy storage including high energy and power. Among many di erent types of batteries, redox ow batteries (RFBs) o er many advantages. Unlike conventional batteries, RFBs store energy in a liquid medium rather than solid active materials. This method of storage allows for the separation of energy and power unlike conventional batteries. Additionally ow batteries may have long lifetimes because there is no expansion or contraction of electrodes. A major disadvantage of RFBs is its lower energy density when compared to traditional batteries. In this Thesis, a novel hybrid Na-based redox ow battery (HNFB) is explored, which utilizes a room temperature molten sodium based anode, a sodium ion conducting solid electrolyte and liquid catholytes. The sodium electrode leads to high voltages and energy and allows for the possibility of multi-electron transfer per molecule. Vanadium acetylacetonate (acac) and TEMPO have been investigated for their use as catholytes. In the vanadium system, 2 electrons transfers per vanadium atom were found leading to a doubling of capacity. In addition, degradation of the charged state was found to be reversible within the voltage range of the cell. Contamination by water leads to the formation of vanadyl acetylacetonate. Although it is believed that vanadyl complex need to be taken to low voltages to be reduced back to vanadium acac, a new mechanism is shown that begins at higher voltages (2.1V). Vanadyl complexes react with excess ligand and protons to reform the vanadium complex. During this reaction, water is reformed leading to the continuous cycle in which vanadyl is formed and then reduced back to the original state. In the discharged state, it was found that precipitation occurs, but is due to solubility limits and not chemical reactions. The TEMPO system showed the potential of higher concentration catholytes although large capacity losses were found. Although no explanation is found, the behavior of the fade is related to time and concentration.
Ph.D. in Mechanical, Materials and Aerospace Engineering, December 2015
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Title: NOVEL MATERIAL SYNTHESIS THROUGH SOL-GEL AND HYDROTHERMAL METHODS FOR FUNCTIONAL APPLICATIONS
Creator: Wang, Chuanlong
Date: 2014, 2014-05
Description: Novel material synthesis was investigated in this thesis to show two major promising ceramic material Fe-Si-O composites and Na3MnCO3PO4...
Show moreNovel material synthesis was investigated in this thesis to show two major promising ceramic material Fe-Si-O composites and Na3MnCO3PO4 composite. Major processing factors in forming Fe2SiO4=SiO2 and Fe2O3=SiO2 powders via sol-gel synthesis followed by solid-state reactions are investigated. The results clearly indicate that the chemical compositions of the precursors, the ratio of the precursors, the nature of the catalyst used, and the gas atmosphere during solid-state reactions can all a ect the outcome of the reaction product(s). The formation of Fe2SiO4=SiO2 is enhanced by using the precursor iron(III) acetylacetonate as the Fe source with the precursor ratio of iron(III) acetylacetonate to tetraethylorthosilicatebeing 1:1 and the addition of formic acid. Otherwise, crystalline Fe and Fe3C are formed in place of Fe2SiO4. By altering the gas atmosphere during solid-state reactions from argon to oxygen, the reaction products change from Fe2SiO4=SiO2 to Fe2O3=SiO2. All of the observed phenomena can be rationalized via the degree of mixing of the Fe-O and Si-O domains at the molecular level in the gel network during sol-gel reactions and the presence of a reducing or oxidizing atmosphere during the solid-state reaction. Hydrothermal method was applied in synthesizing Na3MnCO3PO4 composite which was studied as a high energy density material for Na ion battery (NIBs). In order to improve electronic conductivity for NIBs battery, ball milling with graphite was introduced for the as-synthesized material. This thesis will investigate the roles played by the ionic conductivities and crystal structure changes introduced by high energy ball milling. Such a study has never been conducted before, and thus can o er guidelines to unlock a gateway to truly low cost Na3MnCO3PO4 cathode NIBs with superior performance.
M.S. in Materials Engineering, May 2014
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Title: Operation characteristics of forty gallon chemical fire engine
Creator: Cole, E. R., Puschel, H. W. F., Rusk, R. H.
Date: 2009, 1918
Publisher: Armour Institute of Technology
Description: http://www.archive.org/details/operationcharact00cole

Title: ANALYSIS OF TRANSPORT TOPOLOGY IN THE LEFT VENTRICLE UNDER HEALTHY AND DISEASED STATES
Creator: Hendabadi, Sahar
Date: 2013, 2013-12
Description: There is evidence that under healthy conditions the vortical nature of blood in the LV optimizes pumping, yet precise characterization of...
Show moreThere is evidence that under healthy conditions the vortical nature of blood in the LV optimizes pumping, yet precise characterization of transport in the LV has been lacking. Because the ventricle is not completely emptied during ejection, blood entering through the mitral valve also interacts with residual ow from preceding cycles. The clinical and physiological consequences of these uid dynamics and interactions remain poorly understood in both healthy and diseased hearts. Simulation and imaging studies have aimed to understand the role of intraventricular ow dynamics to facilitate lling, increase ejection e ciency, and avoid blood stasis inside the ventricular chamber. Moreover, these three aspects may be of key importance in patients with heart disease, and most prevalently dilated cardiomyopathy (DCM). In this thesis, we used in vivo measurement of ow in healthy and diseased hearts. A novel processing of Doppler-echocardiography data was performed on patients with DCM and healthy volunteers. Bi-directional velocity eld maps in the apical long axis were obtained and used to perform Lagrangian analysis of transport inside the LV. Lagrangian coherent structures (LCSs) were shown to reveal the boundaries of blood injected and ejected from the heart over multiple beats. These boundaries were used to quantify stasis in the LV, which has potential clinical importance for diagnosing pumping de ciency and thrombosis risk. Indeed, we show that repelling LCSs, in addition to revealing a schematic of the transport topology, also identify structures in the ow that may potentially in uence platelet activation, which we demonstrate on an idealized stenosis model for simplicity. The LCS framework also enabled improved characterization of LV vortices, which had previously received much attention using Eulerian characterizations. The Lagrangian framework presented here uncovered well-de ned boundaries to both E-wave and A-wave lling vortices, which have not been previously quanti ed. To validate the utility xii of the planar ow approximation imposed by Doppler-echocardiography in enabling the dominant transport processes to be characterized, two di erent sets of 3D phase contrast magnetic resonance imaging (PCMRI) data were used to compare 3D ow analysis results with results derived from 2D projection of data in the long-axis. The validation results indicated that the main transport structures were preserved in 2D projections, especially during the ejection phase. Analysis of LV ow topology was also performed in patients undergoing cardiac resynchronization therapy (CRT). The results of this study can contribute to the optimization of AV delays in these patients by taking the LV transport into account. xiii
PH.D in Mechanical Engineering, December 2013
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Title: EXPERIMENTAL METHODS TO DETERMINE MECHANICAL PROPERTIES OF ALUMINUM FOAM LIGAMENTS
Creator: Mathur, Saurabh
Date: 2013, 2013-07
Description: Metal foams are widely used these days and their applications are far reaching from engineering to medical and beyond. This study is aimed at...
Show moreMetal foams are widely used these days and their applications are far reaching from engineering to medical and beyond. This study is aimed at characterizing the property of aluminum foam ligaments in terms of their strength and response to loads. The defining characteristic of metal foams is a very high porosity: typically 75– 95% of the volume consists of void spaces which give them high strength to weight ratio. The aluminum foam (Duocell by ERG Aerospace Corp.) that is used in this study is manufactured using the parent material aluminum alloy 6101-T6. Through this work an effort has been made to understand the mechanical properties of aluminum foam ligaments. The elastic modulus was estimated by conducting bending experiments on ligaments. The yield stress was estimated through both bending and tension experiments which are followed by estimation of ultimate tensile stress using tension experiments on ligaments. A comparative study was also done to understand the difference in mechanical properties of ligaments to that of bulk aluminum alloy 6101-T6. This work also laid emphasis on characterization of ligament geometry in order to understand the mechanical properties of material as geometry plays a very crucial role in the mechanical response of ligaments. The elastic modulus of ligaments was estimated as 13.3 GPa. The yield strength from tension experiment was estimated as 140 MPa and the ultimate tensile strength was estimated as 190MPa
M.S. in Mechanical and Aerospace Engineering, July 2013
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Title: SYNTHESIS AND INVESTIGATION OF NOVEL CATHODE MATERIALS FOR SODIUM ION BATTERIES
Creator: Sawicki, Monica
Date: 2015, 2015-12
Description: Environmental pollution and eventual depletion of fossil fuels and lithium has increased the need for research towards alternative electrical...
Show moreEnvironmental pollution and eventual depletion of fossil fuels and lithium has increased the need for research towards alternative electrical energy storage systems. In this context, research in sodium ion batteries (NIBs) has become more prevalent since the price in lithium has increased due to its demand and reserve location. Sodium is an abundant resource that is low cost, and safe; plus its chemical properties are similar to that of Li which makes the transition into using Na chemistry for ion battery systems feasible. In this study, we report the effects of processing conditions on the electrochemical properties of Na-ion batteries made of the NaCrO2 cathode. NaCrO2 is synthesized via solid state reactions. The as-synthesized powder is then subjected to high-energy ball milling under different conditions which reduces particle size drastically and causes significant degradation of the specific capacity for NaCrO2. X-ray diffraction reveals that the lattice distortion has taken place during high-energy ball milling and in turn affects the electrochemical performance of the cathode material. This study shows that a balance between reducing particle size and maintaining the layered structure is essential to obtain high specific capacity for the NaCrO2 cathode. In light of the requirements for grid scale energy storage: ultra-long cycle life (>20,000 cycles and calendar life of 15 to 20 years), high round trip efficiency (> 90%), low cost, sufficient power capability, and safety; the need for a suitable cathode materials with excellent capacity retention such as Na2MnFe(CN)6 and K2MnFe(CN)6 will be investigated. Prussian blue (A[FeIIIFeII (CN)6]•xH2O, A=Na+ or K+) and its analogues have been investigated as an alkali ion host for use as a cathode material. Their structure (FCC) provides large ionic channels along the <100> direction enabling facile insertion and extraction of alkali ions. This material is also capable of more than one Na ion insertion per unit formula which holds great promise in increasing the energy density of the NIB. The electrochemical performance of the cathode material will be analyzed using cyclic voltammetry, and galvanostatic charge/discharge investigation.
Ph.D. in Materials Science and Engineering, December 2015
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Title: SYNERGETIC COMPUTATIONAL AND EXPERIMENTAL STUDIES OF WALL-BOUNDED TURBULENT FLOWS AND THEIR TWO-DIMENTIONALITY
Creator: Vinuesa, Ricardo
Date: 2013, 2013-05
Description: N/A
PH.D in Mechanical and Aerospace Engineering, May 2013

Title: The retardation of combustion through wire screens in closed pipes
Creator: Conway, F. J, Hall, K. V
Date: 2009, 1917
Publisher: Armour Institute of Technology
Description: http://www.archive.org/details/retardationofcom00conw
Thesis (B.S.)--Armour Institute of Technology, 1917 B.S. in Fire Protection Engineering,...
Show morehttp://www.archive.org/details/retardationofcom00conw
Thesis (B.S.)--Armour Institute of Technology, 1917 B.S. in Fire Protection Engineering, 1917
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Title: PURIFICATION AND CRYSTAL GROWTH OF INI AND ALLOYS IN1-xTLxI AND IN1-xGAxI FOR APPLICATION IN X-RAY AND GAMMA-RAY DETECTORS
Creator: Riabov, Volodymyr
Date: 2016, 2016-07
Description: The present work is focused on developing new semiconductor materials based on Indium Monoiodide (InI) for application in room temperature X...
Show moreThe present work is focused on developing new semiconductor materials based on Indium Monoiodide (InI) for application in room temperature X-ray and gamma-ray detectors. During past two decades InI was studied as room a temperature detector material due to suitable value of the energy gap and high atomic number of its constituents. The most recent studies include investigations at laboratories of Prof. A. Ostrogorsky at Rensselaer Polytechnic Institute (RPI) and Illinois Institute of Technology (IIT) during period 2009-2013. The present work was focused on (i) purification of starting InI material and (ii) crystal growth of InI and InI based alloys with objective to investigate effects of purification and alloying on crystal structure, electrical and mechanical properties. Purification was performed at Radiation Monitoring Devices (RMD) Inc. by innovative techniques combined with well established methods, such as Zone Refining Under Reactive Atmosphere. At RMD, purification was followed by crystal growth of InI by the travelling molten zone method. Crystal growth of InI and alloys In0.99Ga0.01I, In0.99Tl0.01I, In0.95Tl0.05I was performed by Vertical Gradient Freeze (VGF) Method at IIT. The microstructure of produced crystals was analyzed, and their Knoop micro-hardness was measured. The concentration of the dopants as a function of position along the crystals was analyzed by Glow Discharge Mass Spectrometry (GDMS) technique. Band gap of produced materials was estimated as a function of composition by Near-UV-Visible range spectroscopy. Radiation detectors were manufactured from produced crystals. Their electrical properties, such as resistivity, photosensitivity and charge carrier mobility, were measured and, finally, detection performance was estimated.
M.S. in Mechanical and Aerospace Engineering, July 2016
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Title: PROCESSING OF IRON BASED OXIDE DISPERSION STRENGTHENED ALLOYS
Creator: Siddhanthi, Rohan Ashok
Date: 2011-12-19, 2011-12
Description: In this research the Oxide Dispersion Strengthened (ODS) Steel alloy 14 YWT with composition Fe- 14 Cr – 3 W – 0.4 Ti – 0.25 Y2O3 was...
Show moreIn this research the Oxide Dispersion Strengthened (ODS) Steel alloy 14 YWT with composition Fe- 14 Cr – 3 W – 0.4 Ti – 0.25 Y2O3 was consolidated using liquid phase sintering method and it’s mechanical properties were tested and compared with standard materials. Initially the standard composition was prepared by mechanical alloying and cold compacted in to compression samples and then sintered. The consolidated sample density was determined and their compression tests were performed at various temperatures. To improve the strength aluminum powder was added into the mechanically alloyed samples via milling for 15 minutes with the aim to enhance diffusion by liquefying at higher temperatures. Initially specimens with different weight percentage of aluminum were prepared and it was discovered that 2.5% aluminum addition gave the best results; further testing was carried out at this alloy composition. The tests were carried out for 2 different post sintering processes. Tests were also carried out with copper as the sintering agent. A significant increase in yield strength with the addition of 2.5% Al and 10% cold working was observed.
M.S. in Material Science, December 2011
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Title: Computational Techniques for Wind Turbine Power Prediction
Creator: Goyal, Udit
Date: 2011-11-28, 2011-12
Description: Wind energy is expected to play an important role in meeting the ever- increasing energy requirements and reducing our dependence on...
Show moreWind energy is expected to play an important role in meeting the ever- increasing energy requirements and reducing our dependence on conventional sources of energy. Wind turbines are broadly classfied as horizontal-axis and vertical-axis depending upon the orientation of the rotor shaft relative to the wind direction. Considerable research has been carried out on horizontal-axis wind turbines, which today are sophisticated and efficient electro-mechanical systems. Continuous research and development in areas of electronics, controls and instrumentation aids in the advancements of this technology. From an aerodynamic point of view the Betz limit is known to impose theoretical limit on the power extraction of propellers. The momentum balance equations show that the maximum of 59.3 percent of free-stream energy can be extracted by propellers. This limit, however is not well de fined, particularly when considering diff user and nozzle-augmented wind turbines with local flow accelerations. In this study the actuator disk approach is used to model the momentum loss across a wind turbine rotor and simulate the Betz limit using Fluent software. This approach is subsequently applied to study the coefficient of performance expected from dif user and nozzle-augmented wind turbines. Vertical-axis wind turbines, on the other hand, are still not completely understood in terms of blade aerodynamics and are the focus of various research studies. Large variations in angle of attack and wake evolution downstream of the blade have a time-dependent e ffect on the blade forces, instantaneous torque and hence the coefficient of power of the turbine. Since Navier-Stokes solutions for vertical- axis wind turbines are expensive and complicated, various low-cost models have been developed based on momentum balance such as single, double and double multiple- streamtube formulations. These models, however, use static lift and drag data for the airfoils as inputs, neglecting the unsteady e ffects on aerodynamic coefficients. In the present study, an alternative approach based on the panel method is explored further for developing a low-cost computational method for simulating the aerodynamics of vertical-axis wind turbines. At each time step an airfoil is represented as a combination of source and vortex distributions which induce a potential in the flow fi eld. A time-stepping mechanism is implemented satisfying the Kutta and the Kelvin Helmholtz condition for the wake evolution behind the rotating blades. The e ffect of this vortex evolution on the aerodynamic forces on the airfoil is studied, focusing on the coefficient of performance (Cp) of the blade. Results show a decrease in Cp values till the wake attains a quasi steady state. A comparison study is performed with other computational models, showing the importance of the wake evolution in time. An optimization of the blade pitch angle is also performed by defi ning a composite variable pitch function in order to improve the torque and hence the instantaneous power from the blades.
M.S. in Mechanical and Aerospace Engineering, December 2011
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Title: DESIGN AND FABRICATION OF AN UNMANNED GROUND VEHICLE UTILIZING VARIABLE INTERNAL INERTIAL PROPERTIES
Creator: Ruffatto Iii, Donald
Date: 2011-11-27, 2011-12
Description: Mobility of an Unmanned Ground Vehicle (UGV) is highly dependent upon the maximum lateral and longitudinal forces that can be generated at the...
Show moreMobility of an Unmanned Ground Vehicle (UGV) is highly dependent upon the maximum lateral and longitudinal forces that can be generated at the tire/ground interface. These forces are a function of a number of di erent vehicle properties such as suspension geometry, actuators and the tire/terrain interaction mechanics. Typically these properties are xed imposing general limits to the vehicle's maximum achievable lateral and longitudinal accelerations. If you were instead able to modify these parameters dynamically during vehicle operation substantial improvements in robot mobility can be realized. This thesis presents the design a fabrication of the Variable Inertial Vehicle (VIV) which is capable of realizing this. It uses a shifting mass mechanism to vary the normal load distribution among the front and rear tire based upon the desired operating conditions. The shifting mass mechanism is capable of moving a substantial amount of the vehicle along it longitudinally. This provides direction control of the tire normal forces during operation. Described in this thesis is the design of this unique element and its e ects on the rest of the vehicle design. The other main elements di erentiating the VIV from common UGV's such as the electronics, suspension, chassis, and powertrain are also detailed. Finally, a number of experiments utilizing the VIV are presented. These experiments were devised and performed my Chenghui Nie but are presented here to demonstrate the functionality and capabilities of the VIV.
M.S. in Mechanical Engineering, December 2011
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Title: THE EFFECT OF RUTHENIUM ADDITION ON THE PHASE EQUILIBRIA, MECHANICAL PROPERTIES AND OXIDATION RESISTANCE OF TIAL-BASED ALLOYS
Creator: Liu, Qizheng
Date: 2012-05-11, 2011-12
Description: The high temperature phase equilibria in the Ti-Al-Ru ternary system have been investigated but there remain some ambiguous regions. In this...
Show moreThe high temperature phase equilibria in the Ti-Al-Ru ternary system have been investigated but there remain some ambiguous regions. In this work arc-melted alloys were studied using scanning electron microscopy, X-ray diffraction and optical microscopy to determine the isothermal section of Ti-Al-Ru system at 1200°C. The lattice parameters were calculated from X-ray diffraction pattern for some compounds, including LI, 8-Ruso(TixAlso-x) and (AI6o-xTix)Ru4o. The lattice parameter of these three phases generally increases with Ti content. Enthalpy of formation was also measured for LI and 8-Ruso(TixAlso_x) with direct synthesis calorimeter to compare with the lattice parameter change. The enthalpy of formation of LI matches its lattice parameter change, but 8-Ruso(TixAlso_x) shows a reversed trend. It suggests that addition of Ti introduces a stronger bonding in the 8-B2 phase super-lattice. The phase equilibria are discussed in comparison with published research work. A new three phase region was detected for L t, Y and Til_xAl 1+x by X-ray diffraction. The homogeneity region of (AI6o-xTix)RU4o was found to be much higher than previously reported, with almost constant Ru content. The results from the ternary isothermal section also help to clarify the uncertain parts of the binary Ti-Al phase diagram. Three ternary eutectic reaction temperatures were measured with differential scanning calorimetry and the results were compared with the published liquidus projection. The high temperature compression behavior of TiAl-Ru alloys was studied at different temperatures and strain rates. Ru was found to have a strong strengthening effect on TiAI alloys. However the Ru addition amount was limited by its low solubility in y-TiAI and U2-Ti3AI, and the detrimental effect of excessive ternary phase precipitation. Furthermore, the melting temperature decreases when Ru 2:0.6at% as the alloy composition approaches a ternary eutectic point. The strengthening mechanism is discussed and two separate mechanisms are proposed, viz. solid solution strengthening and refined colony strengthening. Intergranular cracks were found in the alloys with low Ru or no Ru addition, but were barely detected as Ru content increased to above 0.6 at.%. It was suggested that Ru showed a beneficial effect on both strength and ductility of TiAI alloys due to the refined colony size. Three-point bend test results showed that the Ru addition can also improve the room temperature ductility of TiAl alloys. Hot workability was increased according to the compression tests. Thermal-mechanically treated TiAI-Ru had much smaller grain size than the heat-treated samples due to dynamic recrystallization. But it did not show superior strength in the compression test compared to the heat-treated samples. The Zener-Hollomon parameter was calculated from the compression strength of heat-treated TiAI-Ru alloys. Its relationship with dynamic recrystallization and hot work is discussed. The mechanical properties of TiAI-Ru alloys are compared with TiAI-Nb samples and demonstrate a promising combination of strength and ductility. The high-temperature oxidation resistance ofTiAI alloys with constant AI content and different alloying elements was tested with thermogravimetric calorimeter. Both Ru and Nb additions were found to have beneficial effect on the oxidation resistance ofTiAI alloys. While TiAI-Ru showed a slight improvement on the oxidation behavior, TiAI-Nb alloys had much better performance in comparison with TiAI alloys. Complicated oxide scale structure was characterized with the assistance of X-ray diffraction, scanning electron microscopy and Energy-dispersive X-ray spectroscopy analysis. The different oxide scale structure among the TiAl, TiAl-Ru and TiAl-Nb alloys were discussed with respect to their thickness, spatial pattern and composition gradient. The poor oxidation resistance of TiAI alloys at the testing temperature was determined to be attributed to the competition growth between Ah03 as well as Ti02, and the lack of a thick continuous Ah03 layer. The outward diffusion of Ti was found to be the controlling factor and the growth of Ti02 on top level of the oxide scale destroyed the initial Ah03 protection. RU02 was found to be the natural marker of the oxidation process in TiAl-Ru alloys due to its slow diffusion. The repartitioning of Ru in the oxide/substrate boundary was revealed to be the reason of its slight beneficial effect. Nb20 S layer was observed in the oxide scale of TiAl-Nb alloys and it played the role of blocking the outward diffusion of Ti. Thus Nb addition can suppress the growth of Ti02 and promote the formation of a continuous AI 20 3 layer. Treating the TiAI alloys by dipping in hydrofluoric (HF) acid was found to have a dramatic beneficial effect on TiAI alloys. Alloying elements have reversed effect on the HF dipping due to the reduced reaction rate with HF acid. The oxidation rate constant and activation energy were calculated for TiAI alloys with/without alloying addition. They were compared with the published data and the trend with composition change was discussed.
Ph.D. in Materials Science and Engineering, December 2011
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Title: LOCALIZATION OF WIND TURBINE NOISE USING A COMPACT MICROPHONE ARRAY WITH ADVANCED BEAMFORMING ALGORITHMS
Creator: Ramachandran, Rakesh Chandran
Date: 2014, 2014-12
Description: The knowledge of noise source location on a wind turbine is crucial for de- signing low noise wind turbines. Even though there has been...
Show moreThe knowledge of noise source location on a wind turbine is crucial for de- signing low noise wind turbines. Even though there has been considerable e ort to theoretically predict the noise from wind turbines in the past, very few experimental investigations have been performed to validate these models. Currently, compliance standards for wind turbine noise are based on single microphone measurements at various designated locations around a wind turbine. This only provides amplitude and frequency data of the overall wind turbine noise. However, it is impossible to locate noise sources, and to understand the dominant noise generation mechanism, using single microphone measurements. A sophisticated method, namely, the use of a microphone phased array with beamforming is necessary to locate the noise sources. Even though microphone arrays have been widely used to study aircraft yover and jet noise, it has just recently found application in locating wind turbine noise. Typical microphone arrays that have been used in the past for monitoring aircraft noise and wind turbine noise are very large ranging up to 270 m2 in area with about 148 mi- crophones. The setup is xed for a particular wind turbine and takes a considerable amount of time. In this thesis it is shown that a compact microphone array (with 24 microphones spread over 1.5 m2) is su cient to locate and separate wind turbine noise sources successfully. It is also shown that in order to use a compact micro- phone array, advanced deconvolution based beamforming methods such as DAMAS, CLEAN-SC, LP, and TIDY are necessary. However, before attempting to validate our idea, it is necessary to understand the concept of array resolution and di erent methods to improve it. We start with an in-depth study on the microphone array resolution and the e ect of di erent beamforming algorithms on it. This study has resulted in several interesting results: (i) The resolution limits that govern the resolution of the imaging system in optics also govern the resolution of microphone array. (ii) The resolution is a function of source frequency, diameter of the array, separation distance between sources, and the distance between the array and the sources. (iii) The resolution lost due to the compact microphone array can be recovered by using deconvolution algorithms. (iv) Di erent algorithms are useful for di erent scenarios; CLEAN-SC is most e cient in extracting the dominant noise source from the source map, LP is e cient in locating multiple or extended noise sources, and TIDY is e cient in locating moving sources. (v) LP and DAMAS show superresolution. (vi) The dynamic range of source maps could be improved by eliminating the diagonal elements of CSM or CCM but care should be take as this could also eliminate weak sources. Following this study, we discuss the results from the full scale large wind tur- bine noise measurements. Our study focuses on the ability of a compact microphone array to successfully locate both mechanical and aerodynamic noise sources on the wind turbine. Several interesting results have emerged from this study: (i) A compact microphone array is su cient to perform a detailed study on wind turbine noise if advanced deconvolution methods are applied. (ii) Noise sources on the blade and on the nacelle can clearly be separated. (iii) Noise of the blades is dominated by trailing edge noise which is frequency dependent and is distributed along the length of the blade with the dominant noise source closer to the tip of the blade. (iv) The LP and DAMAS algorithms represent the distributed trailing edge noise source better than CLEAN-SC and conventional beamforming. (v) Additional tonal noise produced dur- ing yawing operation is believed to be radiating from the tower of the wind turbine that acts like a resonator. (vi) Ground re ection is not believed to have a signi cant e ect on noise source location estimates in this study. (vii) The asymmetry in the aerodynamic noise is attributed to the Doppler ampli cation e ect. Finally, the noise measurements made on the small scale wind turbine showed that the compact array was successfully able to separate out the mechanical and aerodynamic noise. The mechanical noise from the nacelle was found to be the dominant noise source below 3000 Hz and the aerodynamic noise from the blades was found to be dominant above 3000 Hz. The asymmetry in the aerodynamic noise was also present in this case. The study on mechanical noise found that gear box was the dominant noise source. It is hoped that the work presented in this thesis will serve as a guide to researchers who intend to use compact microphone arrays with advanced beamforming algorithms in the future and also to those who intend to validate theoretical models of wind turbine noise.
Ph.D. in Mechanical and Aerospace Engineering, December 2014
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Title: MINIATURE SHOCK TUBE ACTUATORS FOR HIGH SPEED FLOW CONTROL APPLICATIONS
Creator: Ramachandran, Rakesh Chandran
Date: 2011-04-11, 2011-05
Description: In the field of aero-acoustics, one of the primary areas of interest has always been centered around the resonant flows. The fluid structure...
Show moreIn the field of aero-acoustics, one of the primary areas of interest has always been centered around the resonant flows. The fluid structure interactions gives rise to a reverberant field, which results in high amplitude fluctuating pressures associated with the resonant tones that could lead to sonic fatigue failure of sensitive components in the vicinity of such flows. One such fluid structure interaction is the cavity flow problem. Several flow control technologies exist to suppress cavity tones but most of them lose efficacy at off-design conditions and particularly at higher subsonic and supersonic flows. It is due to this fact that there is a high demand for high control authority flow control actuators. In order for an actuator to have higher control authority, one must be able to use a mechanism that has sufficient energy to disrupt the cavity tone generation mechanism at higher subsonic Mach numbers. One such mechanism is the shock tube generating high strength shock waves. To the best of our knowledge, there does not appear to be any use of shock waves to suppress noise emitted by cavity in aircrafts. The main challenge lied in developing the miniature shock tubes that could produce high intensity shock waves. In the present work, we designed, developed and tested these miniature shock tube flow control actuators. The initial part of this work involved a detailed study of the theory behind producing shock waves using a shock tube. The designing and development part included a lot of trial and error adjustments to produce shock waves as predicted by the 1D shock wave theory. Two shock tube actuators were developed, one having a single shock tube and another with three shock tubes but with the same exit area as the previous one. We carried out various characterization experiments measuring the unsteady pressure at the exit of these shock tubes and also the walls of the shock tube. The experimental investigation of the shock tubes revealed that miniature version of the shock tubes indeed produced high intensity shock waves as predicted by the shock wave theory. Apart from the shock tube actuators, fast acting solenoid valves which does not produce any shock were also tested, to compare the efficacy of both types of actuators. The later part of the work focuses on the actual application of these actuators as flow control devices. First, we delve into the acoustic suppression results which show the amount of tonal noise suppression achieved by using these actuators. For the M = 0.6 case the valves produced very good suppression up to 20 dB but the mass flow rate of these valves were about 26% of the main jet mass flow rate. In the M = 0.8 flows the valves produced negligible suppression. The multiple shock tube performed better than the single shock tube in both cases with a tonal noise suppression of up to 12 dB and 10 dB for M = 0.6 and M = 0.8 flows, respectively. The effect of the shock wave on the cavity tone was evident from the results and had a memory effect on the cavity tone suppression. Due to this the mass flux and the momentum coefficient for the shock tube actuators were considerably low. In order to better understand the mechanism through which the actuators suppress cavity tones, mean velocity measurements and phase averaged pressure measurements were carried out. Based on these results, it was observed that the lifting of the shear layer was the dominant mechanism behind steady and pulsed mass injection. In addition to this beamforming, used for locating the noise sources, was also used to study the cavity tones. Detailed discussion of the results are presented in this report.
M.S. in Mechanical and Aerospace Engineering, May 2011
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