Search results

Title: INVESTIGATION OF BI-IN-SN AND BI-IN-SN-GA AS PHASE CHANGE MATERIALS
Creator: Huynh, Hong Trang
Date: 2012-05-02, 2012-07
Description: Phase change energy storage is one of the most effective ways to store thermal energy. The difference between metallic phase change materials ...
Show morePhase change energy storage is one of the most effective ways to store thermal energy. The difference between metallic phase change materials (PCMs) and organic and inorganic PCMs is discussed. Bi-In-Sn and Bi-In-Sn-Ga alloys with near eutectic compositions were analyzed using DSC, X-Ray, EDS and metallography to establish the alloy properties. An attempt was made to package the alloy in metallic and non-metallic foams and various tests such as infiltration and cycling tests were conducted to test the feasibility of various containment materials. These PCM alloys were applied in a prototype cooling system of electronic devices for better heat dissipation than conventional heat sinks. Tests were conducted to measure the effectiveness of the alloys. Different designs were suggested for the containment of the alloy.
M.S. in Mechanical, Materials, and Aerospace Engineering, July 2012
Show less

Title: Computing transition and flow development in turbulent channel flows
Creator: Sallot, Thomas
Date: 2012-12-05, 2012-12
Description: A zero pressure gradient (ZPG) boundary layer in a wind-tunnel test section was computed using two-dimensional CFD simulations utilizing two...
Show moreA zero pressure gradient (ZPG) boundary layer in a wind-tunnel test section was computed using two-dimensional CFD simulations utilizing two RANS models, Spalart-Allmaras (SA) and k􀀀! (SST), and two di erent software suites; i.e., Fluent and STAR-CCM+. These computations have been compared and they revealed that the SST model yields better agreement with experimental data than the SA. They also demonstrate that STAR-CCM+ has very little sensitivity to small pressure gradients, and that is why its computation for the ZPG are not exactly matching the reference data (experiment and DNS). Further analysis of the two softwares leads to the conclusion that the transition is dealt with di erently. These di erent approaches can also contribute to the discrepancies observed in the results. The second part of this study is aimed at analyzing the SA model and proposing an approach to improve its results. Tests on the various options proposed in STAR-CCM+ led us to understand how crucial it is to know the e ect of each setup. In addition, several DNS pro les have been used as in ow conditions for the ZPG problem in order to show that this model can be signi cantly improved by using the appropriate in ow conditions past the transition of the boundary layer. Alternatively, incorporating a transition model into the SA computations based on an approach like the en model, or more advanced transition codes, can result in much better agreement with experiments and recent DNS results. The third part of this work is focused on one of the most computed ows in turbulence: the channel ow. The rst goal was to con rm that an implementation of transition similar to that in the ZPG case can be e ectively used for the channel. The second focus was to nd a criterion to establish the required fetch for the fully developed region in a channel. The criterion found here is based on the asymptotic trend of the centerline velocity and its result indicates a longer distance than the usual xi 100 to 150 full channel heights found in the literature, especially at low Reynolds numbers. Finally, this study reveals the three dimensionality of the channel which appears to be impossible to avoid even for extremely high aspect ratios. Using the RSM model, the results document how the channel ow contains secondary motions, sidewall boundary layers and streamwise vortices that exchange energy and momentum between the center and the side walls. Therefore, channel ows need to be calculated as a 3D problem in order to be modeled properly or to be representative of any physical laboratory experiment.
M.S. in Mechanical and Aerospace Engineering, December 2012
Show less

Title: DEVELOPMENT OF ACTIVE RESPONSE TECHNOLOGY FOR SAFETY APPLICATIONS IN POWER SAWS
Creator: Assaliyski, Marin I.
Date: 2014, 2014-05
Description: This thesis presents a study of kickback occurrences on table saws, as well as the development and evaluation of a system designed to mitigate...
Show moreThis thesis presents a study of kickback occurrences on table saws, as well as the development and evaluation of a system designed to mitigate health and property hazards due to kickbacks. A kickback is an unwanted situation during the cutting process of many powered circular saw tools, during which the operator of the tool loses control, potentially resulting in severe property and bodily harm. Multiple safety devises exist to prevent this type of situation from occurring; however, all of these devices are passive and often become a burden by decreasing e ciency, and are therefore often removed by the users. This thesis seeks to study the occurrence of kickbacks and to present an active electronic detection system that is able to aid in mitigation of potential damage to property or persons by developing responsive, robust, and practical methods of kickback detection. Implemented detection methods are presented and evaluated for performance. Concepts are also developed, presented, and discussed with the purpose of generating topics for future work. An experimental brake is used to evaluate the performance of the detection methods with an integrated system.
M.S. in Mechanical and Aerospace Engineering, May 2014
Show less

Title: ENERGY SAVINGS FOR UAV FLIGHT IN UNSTEADY GUSTING CONDITIONS THROUGH TRAJECTORY OPTIMIZATION
Creator: Grimaud, Lou
Date: 2014, 2014-07
Description: The purpose of this thesis is to show how micro unmanned aerial vehicles can extract energy from periodic wind gusts and how this energy...
Show moreThe purpose of this thesis is to show how micro unmanned aerial vehicles can extract energy from periodic wind gusts and how this energy extraction is a ected by the e ects of unsteady aerodynamics and the spatial structure of the gust component. The trajectory of a small UAV ying through wind gusts is simulated with a two degree of freedom model. The non-dimensional model is set to include vertical and horizontal gusts of varying amplitudes and durations. From this model an optimization routine is performed in order to obtain the minimum gust amplitude needed to obtain a neutral energy trajectory. With these results, it is shown that neutral energy ight is possible through gusts speeds of only 10 to 30% of the ying speed of the aircraft. Analysis of the results shows that the lift coe cient has to be changed very rapidly in order to perform these maneuvers in short duration gusts. Moreover high lift values are often required. To achieve this kind of rapid change in the lift and drag forces, fast variations of the angle of attack are needed. The high lift values also require high angles of attack that are likely to cause separation of the ow over the airfoil. These fast variations at high angle of attack are shown to cause unsteady non linear aerodynamic responses. Traditional CFD simulations are far too computationally expensive to be implemented into the optimization routine. To solve this issue a low order model based on a paper by Goman and Khrabrov [7] (GK) is developed and validated against experimental results. This model produces accurate predictions of the lift and drag coe cients for a wide range of angles of attack and for di erent type of pitch inputs. With this GK model the in uences of the unsteady aerodynamics on the energy extraction problem are highlighted. The main di erence with quasi-steady aerodynamics model was found to be for gusts at a reduced frequency (k = cf u ) higher than 0.07. Around these values the potential performance is improved by introducing the unsteady model. The trajectories obtained include more violent changes in angle of attack in order to take full advantage of the unsteady e ects.
M.S. in Mechanical, Materials, and Aerospace Engineering, July 2014
Show less

Title: DEVELOPMENT OF MULTI-NOZZLE MICRO-EXTRUDER FOR LAYERED MANUFACTURING OF MULTI-MATERIAL ENERGY STORAGE DEVICES
Creator: Mohamed Ayub, Shaik Mohamed Imran
Date: 2014, 2014-05
Description: Additive Manufacturing is critical in the development of high energy density storage devices for its flexibility to manufacture complex parts...
Show moreAdditive Manufacturing is critical in the development of high energy density storage devices for its flexibility to manufacture complex parts with different discrete compositions like cathodes, anodes and electrolytes. Such storage devices under sub- millimeter scale with micro-structured interdigitated layout could significantly improve its power and energy density. Over the past few years, scientific communities in Rapid Prototyping technology have been mainly focusing on various methods of Modeling and representing Multi-Material Object under single CAD data structure which would enable post processing and rapid prototyping of Multi-Material Object (MMO). This thesis will address the processes involved in the development of Multi-Material Micro Extrusion (M3E) device for manufacturing high density energy storage devices through discrete composition control in Solid Freeform Fabrication (SFF). The primary goal of the research is to develop a rectilinear motion platform with a multi-extrusion system and an open loop control interface to regulate the unreliable extrusion of slurries of different discrete composition. The dissertation will also address the software methodology to discretize 3D-CAD models to represent multiple material composition followed by slicing it into 2.5D layers, which will enable to create Computer Numeric Control (CNC) path program. The scope of this research is further extended to study and optimize various mechanical process inputs with respect to extrusion output parameters.
M.S. in Mechanical and Aerospace Engineering, May 2014
Show less

Title: RELATIVE RECEIVER AUTONOMOUS INTEGRITY MONITORING FOR FUTURE GNSS-BASED AIRCRAFT NAVIGATION
Creator: Gratton, Livio Rafael
Date: 2011-05-15, 2011-05
Description: The Global Positioning System (GPS) has enabled reliable, safe, and practical aircraft positioning for en-route and non-precision phases of...
Show moreThe Global Positioning System (GPS) has enabled reliable, safe, and practical aircraft positioning for en-route and non-precision phases of flight for more than a decade. Intense research is currently devoted to extending the use of Global Navigation Satellite Systems (GNSS), including GPS, to precision approach and landing operations. In this context, this work is focused on the development, analysis, and verification of the concept of Relative Receiver Autonomous Integrity Monitoring (RRAIM) and its potential applications to precision approach navigation. RRAIM fault detection algorithms are developed, and associated mathematical bounds on position error are derived. These are investigated as possible solutions to some current key challenges in precision approach navigation, discussed below. Augmentation systems serving large areas (like the Wide Area Augmentation System (WAAS) covering the North American continent) allow certain precision approach operations within the covered region. More and better satellites, with dual frequency capabilities, are expected to be in orbit in the mid-term future, which will potentially allow WAAS-like capabilities worldwide with a sparse ground station network. Two of the main challenges in achieving this goal are (1) ensuring that navigation fault detection functions are fast enough to alert worldwide users of hazardously misleading information, and (2) minimizing situations in which navigation is unavailable because the user‟s local satellite geometry is insufficient for safe position estimation. Local augmentation systems (to be implemented at individual airports, like the Local Area Augmentation System or LAAS) have the potential to allow precision approach and landing operations by providing precise corrections to user-satellite range measurements. An exception to these capabilities arises during ionospheric storms (caused by solar activity), when hazardous situations can exist with residual range errors several orders of magnitudes higher than nominal. Until dual frequency civil GPS signals are available, the ability to provide integrity during ionospheric storms, without excessive loss of availability, will be a major challenge. For all users, with or without augmentation, some situations cause short duration losses of satellites in view. Two examples are aircraft banking during turns and ionospheric scintillation. The loss of range signals can translate into gaps in good satellite geometry, and the resulting challenge is to ensure navigation continuity by bridging these gaps, while simultaneously maintaining high integrity. It is shown that the RRAIM methods developed in this research can be applied to mitigate each of these obstacles to safe and reliable precision aircraft navigation.
Ph.D. in Aerospace Engineering, May 2011
Show less

Title: SHORT AND ULTRASHORT-PULSED LASER-MATERIAL INTERACTIONS: MODELING AND COMPARISONS WITH EXPERIMENTS
Creator: Tao, Sha
Date: 2013, 2013-07
Description: Lasers have wide applications in numerous areas. Laser-based applications and technologies often involve certain types of laser-material...
Show moreLasers have wide applications in numerous areas. Laser-based applications and technologies often involve certain types of laser-material interactions, many of which have not been sufficiently understood. In this thesis, through the development of the corresponding physics-based models and the comparisons of modeling results with relevant experiments (when available), the laser-material interaction mechanisms during the following processes will be studied: i) laser ablation of semiconductors; ii) laser-material interactions inside microholes; and iii) laser-induced plasma evolution (more detailed conditions of the studied processes are given in the thesis). This research work is expected to improve the understanding of laser-material interaction mechanisms in the above investigated processes, which may provide information that is useful for the improvement of many related existing laser-based applications or technologies and for the development of novel ones.
PH.D in Mechanical and Aerospace Engineering, July 2013
Show less

$THE CHARACTERIZATION FOR B2 STRUCTURE AND L2\ STRUCTURE IN THE AG-MG AND AG-MG-IN SYSTEM$

Title: THE CHARACTERIZATION FOR B2 STRUCTURE AND L2\ STRUCTURE IN THE AG-MG AND AG-MG-IN SYSTEM
Creator: Kim, Do Hyung
Date: 2013, 2013-05
Description: The concentration of point defects and the long range order for ordered B2 AgMg alloys, quenched from 973K, was investigated by statistical...
Show moreThe concentration of point defects and the long range order for ordered B2 AgMg alloys, quenched from 973K, was investigated by statistical thermodynamic modeling, powder X-Ray Diffractometery and diffraction simulation as a function of composition. The lattice parameter behavior on the Ag rich side are expectably having constitutional and thermal anti-site defects on both Ag and Mg sub-lattices, corresponding to the literature data. On the other hand, the Mg rich side has substantially thermal vacancy defects based on the lattice parameter data which shows lower, compared with previously reported data. Concentration of the equilibrium point defects at 973K was calculated from two thermodynamic models, where the Ag rich side was based on the constitutional and thermal anti-site defect formation and the Mg rich side was based on the hybrid defect formation consisting of vacancy, Mg and Ag anti-site defects The experimental long range order at 973K, determined from the integrated intensity ratio of (100) super-lattice reflection to (200) fundamental reflection, is in quite good agreement with the theoretical long range order at 973K based on the calculated integral intensities from the diffraction simulation with the equilibrium concentration of each point defect, obtained by two thermodynamic models. Furthermore, point defect hardening coefficients on both sides of stoichiometry were determined by the measurement of the Vickers hardness as a function of the equilibrium concentration of the main point defects deduced from two thermodynamic models. The hardening coefficient is G/16 for the Ag rich side with respect to Ag anti-site defects and G/3.1 for the Mg rich side with respect to vacancy defects. Also, two hardening coefficients are corresponding to the empirical correlation for the several binary B2 intermetallic compounds with anti-site defects (G/9 to G/85) xvi and vacancy defects (G/3 to G/4). This suggests that the elastic size effect on the Ag rich side is the primary hardening mechanism due to constitutional and thermal Ag anti-site defects while the Mg rich side is likely to have the elastic modulus effect due to constitutional and thermal vacancy defects. It is also indicated that the vacancy defect is more significant hardener than Ag anti-site defects for the ordered B2 AgMg intermetallic system. The partial liquidus projection in the Ag-Mg-In ternary system was established by the primary phase and liquidus temperature, using the Scanning Electron Microscopy, Energy Dispersive Spectroscopy and Differential Scanning Calorimetry. The results showed that the AgMg1-xInx phase of the Ag-Mg-In ternary system has a large primary solidification field up to 90 at.% of In, so that most ternary invariant reactions of the In rich field must be formed beyond 90 at.% of In. The liquid-solid schematic reactions in the Ag rich field were experimentally confirmed, but those of the In rich side have not been established. Furthermore, the ordering phase transition and melting temperature of the Heusler phase AgMg1-xInx alloys were investigated using Differential Scanning Calorimetry, Scanning Electron Microscopy, and powder X-Ray Diffractometery. The DSC results indicated that the melting temperature decreased with increasing the In composition, but a thermal peak for the ordering phase transition was not detected due to either a very small heat of transition or a second order transformation. The XRD results showed that the L21 structure of the Heusler phase was observed for the 15 at.% of In alloy and the degree of order of L21 structure continuously increased with the In composition, resulting from the (111) super-lattice intensity with respect to the In composition. The L21 structure ordering of the 15 at.% of In and 20 at.% of In system xvii was gradually decreased with increasing the annealing temperature, corresponding to decreasing the (111) super-lattice intensity and the long rang order parameters of the L21 structure. These XRD behaviors suggest that the L21/B2 ordering transformation phenomena is a second order transformation with respect to temperature.
PH.D in Material Science and Engineering, May 2013
Show less

Title: HYBRID ELECTROSTATIC AND MICRO-STRUCTURED ADHESIVES FOR ROBOTIC APPLICATIONS
Creator: Ruffatto, Donald F., Iii
Date: 2015, 2015-07
Description: Current adhesives and gripping mechanisms used in many robotics applica- tions function on very speci c surface types or at de ned attachment...
Show moreCurrent adhesives and gripping mechanisms used in many robotics applica- tions function on very speci c surface types or at de ned attachment locations. A controllable, i.e. ON-OFF, adhesive mechanism that can operate on a wide range of surfaces would be very advantageous. Such a device would have applications ranging from robotic gripping and climbing to satellite docking and inspection/service mis- sions. The main goal of the research presented here was to create such an attachment mechanism through the use of a new hybrid adhesive technology. The newly devel- oped adhesive technology is a hybridization of electrostatic and micro-structured dry adhesion. The result provides enhanced robustness and utility, particularly on rough surfaces. There were challenges not only in the integration of these two adhesive elements but also with its application in a complete gripping mechanism. Electrostatic and directional dry adhesives were both individually investigated. The electrode geometry for an electrostatic adhesive was optimized for maximum ad- hesion force using nite element analysis software. Optimization results were then veri ed through experimental testing. New manufacturing techniques were also de- veloped for electrostatic adhesives that utilized a metalized mesh embedded in a sili- cone polymer and Kapton lm based construction, greatly improving adhesion. The micro-structured dry adhesive used was provided by Dr. Parness, from the NASA Jet Propulsion Lab (JPL), and consists of an array of vertical stalks with an angled front face, referred to as micro-wedges. The hybrid electrostatic dry adhesive (EDA) was created by fabricating the electrostatic adhesive directly on top of a dry adhesive mold. This process created an array of dry adhesive micro-wedges directly on the surface of the electrostatic adhesive. In operation the electrostatic adhesive provides a normal force which serves to pull the dry adhesive into the surface substrate. With greater surface contact more of the dry adhesive is able to engage, bring the electro-static adhesive even closer to the surface and increasing its e ectiveness. Therefore, the combination of these two technologies creates a positive feedback cycle whose whole is often greater than the sum of its parts. An interface mechanism is needed to transmit applied loads from a rigid struc- ture to the exiable adhesive while still maintaining its conformability. This is es- pecially important for strong adhesion on rough surfaces, such as tile and drywall. Di erent concepts such as a structured brillar hierarchy and a uid- lled backing pouch have been explored. Additionally, nite element analysis was used to evaluate di erent fribrillar shapes and geometry for the structured hierarchy. The goal was to equalize the load distribution across the adhesive while still maintaining surface compliance. A gripper mechanism was also created which used a servo for actuation and three rigid tiles with a directional dry adhesive. It was tested on a perching Micro Air Vehicle (MAV) as well as in the RoboDome facility at NASA's Jet Propulsion lab to simulate a satellite docking/capture maneuver.
Ph.D. in Mechanical and Aerospace Engineering, July 2015
Show less

Title: IDENTIFY AND IMPROVE OBSTACLE AVOIDANCE CAPABILITY OF UNMANNED GROUND VEHICLE
Creator: Nie, Chenghui
Date: 2015, 2015-05
Description: An Unmanned Ground Vehicle (UGV), incorporating a high level of obstacle avoidance capability, benefits from field operations. Such a UGV...
Show moreAn Unmanned Ground Vehicle (UGV), incorporating a high level of obstacle avoidance capability, benefits from field operations. Such a UGV would be better able to travel at a high average speed to quickly finish tasks, as well as quickly alter its trajectory to avoid getting into hostile situation. However, avoiding obstacles at high speed is challenging, since the danger of collisions with obstacle is increased with vehicle speed. This thesis developed novel metrics to mathematically identify the obstacle avoidance capability of ground vehicles. The theory is applied to demonstrate the characteristics of the obstacle avoidance capability of generalized rigid bodies and three types of wheeled ground vehicles: Ackermann steered, differential steered and omni-directional vehicle. The design guidelines are provided in the final chapters to improve obstacle avoidance capabilities of these three types of wheeled ground vehicles. I demonstrated in this thesis that the Ackermann steered vehicle's obstacle avoidance capability is related to the location of its center of mass. I utilized the obstacle avoidance theory to create a novel Variable Inertial Vehicle (VIV), an unmanned ground vehicle with a capability to control the location of its center of mass during locotion. Experimental results are presented to demonstrate the improved obstacle avoidance capability at the end. This thesis also experimental evaluates the characteristics of the obstacle avoidance capability of an omni-directional unmanned ground vehicle. This omnidirectional vehicle is comprised of four independent differential steered units, Active Split Offset Caster (ASOC). Both the characteristics of the vehicle system and ASOC kinematics are demonstrated. Experimental results are presented at the end to validate its distinct obstacle avoidance capability in challenging outdoor terrains.
Ph.D. in Mechanical and Aerospace Engineering, May 2015
Show less

Title: INVESTIGATION AND MODELING OF PRESSURE DEPENDENT YIELD BEHAVIOR OF 3D STOCHASTIC AND PERIODIC FOAMS
Creator: Ayyagari Venkata S, Ravi Sastri
Date: 2013, 2013-07
Description: With growing potential of cellular solids in a multitude of diverse engineering applications including but not limited to automotive,...
Show moreWith growing potential of cellular solids in a multitude of diverse engineering applications including but not limited to automotive, aerospace, naval and biomed- ical industries as lightweight alternatives and space lling cores in sandwich struc- tures, need for predictive yield/failure criteria for these load bearing members under multiaxial stress states becomes critical. Although there exist several yield criteria proposed in the literature for highly porous solid foams, they are all phenomenolog- ical in nature, rely on relatively long list of model parameters that require di cult experimentation not readily available to end user, and none of them can handle the anisotropy observed in the majority of commercially available solid foams. Further, it is by now well established that, unlike commonly used engineering bulk solids, the yield behavior of highly porous solid foams is signi cantly in uenced by the hydro- static component of stress. In majority of phenomenological yield criteria proposed for solid foams this dependence is expressed by a quadratic pressure term. The scope of this study is quite comprehensive in the sense that it integrates analytical and computational investigation of yield behavior in solid foams along with extensive validation by recent experimental results produced in our lab. Present study proposes a physics based approach by hypothesizing that the yielding of stochastic foams is governed by the total elastic strain energy density, which leads to an energy based yield criterion for transversely isotropic foams and also provides a physical basis for the quadratic pressure dependence commonly adopted in existing phenomenolog- ical models. An added bene t of the analytical framework proposed in this work is that it introduces new scalar measures of stress and strain, which are referred to as characteristic stress and characteristic strain, that function in an analogous way to e ective (von Mises) stress and strain commonly used in analyzing the yield and post- yield behavior of bulk metals. Besides accommodating anisotropy, this energy-based xii yield criterion renders a unique advantage by relying only on the elastic properties and uniaxial yield strengths of the material, which makes the proposed yield criterion extremely practical for end user. Results from experimental data obtained from multiaxial testing of Divinycell H100 and H130 foams (Sha q, 2009; Ehaab, 2011) as well as a series of extensive com- putational simulations performed in this study on: a) periodic Kelvin foam models (both isotropic and transversely isotropic) of varying relative densities, b) stochastic Voronoi foams (both isotropic and transversely isotropic), point out to an additional linear pressure dependence in the yield behavior of solid foams, from a load-sharing viewpoint. This dependence is observed to be more pronounced at lower relative den- sities. A simple quantitative technique which is based on the partition of elastic strain energy into bending and stretch components is used to identify the distribution of deformation modes at microstructural level, along with its in uence on load sharing as a function of stress path. Furthermore, a plasticity model that incorporates a ow rule and hardening law are presented which allows the analysis of inelastic deforma- tions in solid foams in a continuum framework. Such models facilitate development of user de ned material model (UMAT) that allow evaluating the performance of proposed yield criterion under complex loading scenarios, such as indentation and punch loading.
PH.D in Mechanical and Aerospace Engineering, July 2013
Show less

Title: EFFECTS OF FUEL PROPERTIES ON THE COMBUSTION PROCESS OF AN ADVANCED DIESEL ENGINE
Creator: Ramos Silva, Cedric Zacarias
Date: 2015, 2015-12
Description: Internal combustion engines are encountered in our everyday lives in passenger cars and heavy-duty vehicles such as trucks and buses. While...
Show moreInternal combustion engines are encountered in our everyday lives in passenger cars and heavy-duty vehicles such as trucks and buses. While conventional compression ignition engines burn diesel fuel with an oxidizer (generally air) in a combustion chamber, much recent research has focused on improving the efficiency of combustion and reducing vehicle pollutant output through the usage of fuels with properties which differ from those of diesel fuel. In particular, this study focuses on a dual fuel engine in which two fuels (usually gasoline or diesel fuel mixed with an alternate fuel) are separately injected and combusted. Results from an Argonne National Laboratory test cell utilizing a 13 Liter (L) heavy duty dual fuel engine running in a combustion mode known as Reactivity Controlled Compression Ignition (RCCI) were leveraged in this work. In a RCCI engine, two fuels of different reactivities (low reactivity and high reactivity) are used in order to control in-cylinder fuel reactivity and allow for the optimization of combustion phasing and duration. In addition, RCCI combustion has been shown to produce low amounts of nitrogen oxides (NOx) as well as particulate matter (PM) emissions which may eliminate the need for expensive after-treatment systems. The combustion shaping capabilities and low emissions of RCCI dual fuel engines enable reductions in heat transfer losses and as such the increase of fuel efficiency. In order to understand the dynamics of such engines, a detailed simulation model of a RCCI dual fuel engine was constructed and developed using the Gamma Technologies (GT) simulation suite in particular GT-POWER and GT-SUITE. Modeling of the complex gas exchange process as well as the combustion process of the 13L RCCI dual fuel engine were both undertaken. This model was then leveraged to examine the effect of fuel properties on the combustion process using GT simulation suite. Experimental data from the 13L engine at Argonne was used to validate the models of the gas exchange and combustion processes. For the gas exchange process as well as the combustion process, the results from the simulation model fairly accurately match the experimental data from the Argonne engine. To achieve RCCI, the engine is equipped with a complex air handling system which includes two turbochargers as well as exhaust gas recirculation (EGR). To ensure that the gas exchange process was accurately captured, the experimental intake pressure, EGR fraction (EGR mass flow rate divided by the sum of EGR mass flow rate and air mass flow), fresh airflow rate, maximum in-cylinder pressure, IMEP and exhaust pressure were compared with the simulation results given by GT-POWER and GT-POST. By modeling the engine components in GT-POWER and adding additional control algorithms, the previously mentioned parameters predictions were within 10% of the engine data. The combustion process was modeled using a Direct-Injection Jet (DI-Jet) combustion model. The DI-Jet model is a predictive combustion model which predicts the burn rate, combustion rate and NOx emissions. This model was calibrated by comparing the experimental and simulation heat release curves. Particular attention is given to accurately capturing the start of combustion and ignition delay period because they affect the combustion process the most.
M.S. in Mechanical and Aerospace Engineering, December 2015
Show less

Title: CHARACTERIZATION OF THE FRICTION VELOCITY BASED ON THE BEHAVIOR OF AN OIL DROPLET IN A CHANNEL FLOW
Creator: Bonnavion, Guillaume
Date: 2015, 2015-05
Description: The study of oil films can be an approach to determine the friction velocity of turbulent channel flows. In experimentation, the oil film...
Show moreThe study of oil films can be an approach to determine the friction velocity of turbulent channel flows. In experimentation, the oil film motion and the shear stresses can be measured using oil film interferometry. Similarly, these techniques can be set up to obtain the equivalent numerical simulation of these kinds of flows, also displaying the evolution of an oil droplet in such configurations. A two-dimensional simulation had been obtained using the Nek5000 code provided by Argonne National Laboratory. In this work, it was aimed to check the accuracy of such a simulation and to extend it to a uniform three-dimensional case to see whether the solver could be used to solve such problems. A new two-dimensional simulation was set up and gave preliminary results. A better achievement was made using tuned inputs that allowed comparing it with an available theory. The simulation and its accuracy were justified in specific cases. It was then extended to two uniform three-dimensional cases and compared with the previously obtained two-dimensional results. This allowed an extension of the use of the solver in specific cases and therefore provides an easy-to-implement method to determine the friction velocity in a flow and also to access some flow information such as velocity profiles or by extension pressure gradients.
M.S. in Mechanical and Aerospace Engineering, May 2015
Show less

Title: THERMAL AND MECHANICAL ANALYSIS OF ELECTRON BEAM ADDITIVE MANUFACTURED TI-6AL-4V BUILD PLATE
Creator: Cao, Jun
Date: 2017, 2017-07
Description: Electron Beam Additive Manufacturing (EBAM), used to fabricate net or nearnet- shaped components based on a sliced CAD model, offers a...
Show moreElectron Beam Additive Manufacturing (EBAM), used to fabricate net or nearnet- shaped components based on a sliced CAD model, offers a potential alternative solution for the processing of titanium components, especially for large parts. However, the components fabricated using EBAM exhibit significant difficulties in quality control and quality assurance due to lack of knowledge of thermo-mechanical-metallurgical relationship. In this work, the thermo-mechanical behavior of wire-feed EBAM for largescale Ti-6Al-4V build plates has been investigated computationally and experimentally, with special attention to the distortion and residual stress, as well as the microstructural evolution. A 3D transient fully coupled thermo-mechanical finite element (FE) model was built, calibrated, and rigorously validated. To ensure the accuracy of the model, the bulk residual strain distribution was measured using neutron diffraction (ND), and the numerically simulated thermal profiles were physically simulated using a Gleeble® 3500, in addition to the conventional model validation methods. Good agreement was found between the simulation results and experimental measurements. A series of simulations were performed to determine the optimum process conditions. The simulation results indicated that preheating, increasing deposition power and scan rate, and decreasing interval cooling time effectively mitigates the distortion and residual stress. For EBAM Ti-6Al-4V build plates, increasing the energy input and reducing the heat loss renders smaller temperature difference and thermal expansion mismatch, consequently, leading to a lower level of distortion and residual stress. The deposited cladding was characterized by large columnar grains growing across layers, a bottom region with repeated macroscopic bands and a top region without these bands. The band structure exhibits mostly colony α. A fine basket-weave structure is observed above the band structure, and a coarse basket-weave structure is observed below the band structure. The simulated thermal profiles were used to understand the observed microstructure. It was found that the microstructure variation in the cladding of EBAM Ti-6Al-4V build plates is strongly dependent on the peak temperature within the (α+β) phase region, and heating rate and cooling rate have insignificant effects on it. The non-equilibrium solid-solid phase transformation of Ti-6Al-4V under continuous heating/cooling were experimentally investigated. The kinetics of phase transformation was quantitively studied and modeled using a non-isothermal JMAK (Johnson-Mehl-Avrami-Kolmorgorov) model, with the activation energy QA=123.9 kJ/mole, JMAK exponent n=1.8, and the calculated ln (k0) varied between 9.15 to 10.6 for different heating rate.
Ph.D. in Materials Science and Engineering, July 2017
Show less

Title: REAL-TIME ARAIM USING GPS, GLONASS, AND GALILEO
Creator: Cassel, Ryan
Date: 2017, 2017-05
Description: Since the inception of GPS, satellite navigation has been a widely used means of navigation for both military and civilian users on the ground...
Show moreSince the inception of GPS, satellite navigation has been a widely used means of navigation for both military and civilian users on the ground and in the air. GPS is capable of providing highly accurate positioning and timing information to users around the globe. However, for certain applications, providing high-accuracy position estimates is not sufficient. Because satellites are susceptible to faults, the safety, or integrity, of the position estimates is also of concern, especially in civilian aviation where safety is critical. As such, receiver autonomous integrity monitoring (RAIM) can be used in order to detect and potentially exclude these faults and guarantee the safety of the position estimate. RAIM has been capable of supporting horizontal aircraft navigation using GPS for decades and has proven to be a useful tool. Now, as more global navigation satellite systems (GNSS) become available, the potential for advanced RAIM (ARAIM) to support vertical guidance for aircraft using multiple constellations has become an area of great interest. In this work, the ARAIM methodology is discussed, and the procedure is outlined, including protection level calculation, fault detection, and exclusion. The procedure is then implemented in a real-time ARAIM prototype. While GPS and Galileo aim to provide worldwide coverage for vertical guidance by 2020 when Galileo is fully operational, ARAIM performance can be examined at present using the current full-strength GPS and GLONASS constellations. This prototype performs position estimation and ARAIM using measurements from the current GPS, GLONASS, and partial Galileo constellations. ARAIM results in a variety of different GNSS scenarios are examined. Furthermore, this work investigates two methods of improving the computational efficiency of the ARAIM algorithm: satellite selection and fault mode grouping.
M.S. in Mechanical and Aerospace Engineering, May 2017
Show less

Title: GRAIN BOUNDARY ENGINEERING OF POWDER-PROCESSED NI-BASE SUPERALLOY RR1000
Creator: Detrois, Martin
Date: 2016, 2016-05
Description: Grain boundary engineering (GBE) has been used to improve the properties of various polycrystalline materials by optimization of their grain...
Show moreGrain boundary engineering (GBE) has been used to improve the properties of various polycrystalline materials by optimization of their grain boundary network. Traditional processing routes for GBE often require multiple iterations of cold work followed by short annealing cycles where each iteration imparts a modest increase in the fraction of special grain boundaries. Multiple iterations are then required to achieve sufficiently high fractions (>50%) that result in the improved properties. Thus, this GBE approach is not suitable for the fabrication of large, complex-shaped structures and leads to added manufacturing lead time and cost. In this investigation, the Ni-base superalloy RR1000 used as turbine discs in gas turbine engines manufactured by Rolls-Royce, was considered for GBE using alternative processing routes more suitable to the forging of Ni-base superalloy components. A preliminary study of the e↵ects of hot deformation parameters closer to typical industrial processing revealed that the length fraction of ⌃3 boundaries increased from 35% to 52% following a single deformation/anneal cycle. Deformation parameters that resulted in strain accommodation via superplastic flow did not enhance the formation of ⌃3 boundaries upon annealing. Whereas deformation parameters that resulted in a dominant dislocation-based plasticity flow mechanism promoted the formation of annealing twins. Using misorientation maps and by estimating the stored strain energy from deformation, equations for the length fraction and density of ⌃3 boundaries were generated for high-temperature GBE of RR1000. The grain boundary characters obtained via high-temperature deformation, however, are less ideal than those resulting from traditional cold rolling. The underlying mechanisms responsible for the formation of ⌃3n boundaries during high-temperature GBE were further investigated. A larger starting grain size prior to deformation was found to be unfavorable to the formation of twin boundaries from twin-reorientation and annihilation of preexisting twins. While recrystallization was found to populate the microstructure with grains that contained very few twin boundaries, post-deformation texture was found to promote the formation of ⌃3 boundaries and triple junctions when Goss texture was present. A final consideration of larger scale forgings was used to raise an outlook on the current issues and the potential of high-temperature GBE for turbine engines.
Ph.D. in Materials Science and Engineering, May 2016
Show less

Title: TWO-DIMENSIONAL AND AXISYMMETRIC BUBBLE RISE USING THE LEVEL SET METHOD
Creator: Dominik S, Michael
Date: 2013, 2013-07
Description: Gas bubbles in liquids are important in many industries, including power gen- eration, steel making, as well as chemical and waste water...
Show moreGas bubbles in liquids are important in many industries, including power gen- eration, steel making, as well as chemical and waste water treatment. A fundamen- tal understanding of the bubble rising physics is helpful in many practical applica- tions. A new level set code for incompressible, multiphase ows using the vorticity- streamfunction formulation in both two-dimensional and axisymmetric cases has been developed. The level set method is well suited to treating multiphase ows having complex interface shapes that may undergo topological changes such as merging and splitting of bubbles. Previous numerical and experimental results for single and mul- tiple bubbles are used to determine the numerical parameters that should be used for the new code and to demonstrate the accuracy of the model. The shape and ter- minal velocities of air bubbles in mineral oil and water are found to duplicate other experimental and calculated results very closely. Results have been compared from two-dimensional and axisymmetric versions of the code for bubbles merging with var- ious surface tension. It is found that prior to merging of the bubbles, the results for velocities and bubble shapes are very similar. However, surface tension is found to have a greater in uence on the axisymmetric results. Once the bubbles merge, the combined bubble evolves toward the same shape and terminal velocity of a single bub- ble having the same volume. The initial acceleration of a single air bubble in water is analyzed and found to be approximately 3:3g, not 2g, which is the predicted value from added mass analysis based on potential ow theory. When the liquid density is increased, the acceleration is also found to increase.
PH.D in Mechanical and Aerospace Engineering, July 2013
Show less

Title: The design and application of apparatus for determining the distribution of water from automatic sprinkler heads
Creator: Rietz, Walter H., Pfafflin, Theo K.
Date: 2009, 1915
Publisher: Armour Institute of Technology
Description: http://www.archive.org/details/designapplicatio00riet
Thesis (B.S.)--Armour Institute of Technology

Title: ACOUSTICALLY FORCED EXTERNAL PULSED COMBUSTION
Creator: Karuppiah, Manikandan
Date: 2011-04-25, 2011-05
Description: Pulsed combustion is one of the most energy-efficient and less polluting ways to produce a hot gas stream for heating purposes. It is usually...
Show morePulsed combustion is one of the most energy-efficient and less polluting ways to produce a hot gas stream for heating purposes. It is usually limited, however, by the need to confine the combustion within a resonant tube. In the experiments presented here, pulsed combustion was achieved in the open air by means of upstream acoustic forcing of a porous matrix burner. Using metal matrices at least 20 mm thick, with pore densities of 60 pores per inch, a stoichiometric mixture of air and natural gas at a constant rate of 217.5 standard cubic feet per hour was forced by a speaker mounted on the plenum upstream of the matrix by means of sinusoidal waves of variable amplitude, at 10 to 150 Hz. Instantaneous surface temperature, as well as pressures upstream and downstream of the matrix were acquired. Phase-locked photographs of the combustion zone were acquired by means of a mechanical stroboscope synchronized to the forcing signal. It was found that, as the forcing amplitude increases, the mode of combustion switches from continuous to oscillating flame, to pulsed combustion consisting of a series of ignitions and extinctions. The change of combustion mode was accompanied by substantial changes in matrix surface temperature, with the pulsed mode reaching temperatures 170°C higher than steady-state combustion and 70% increase in radiant heat flux emitted. This was usually accompanied by a contraction in the size of the hot part of the matrix, resulting in an overall increase in radiant heat output of 5%, for our experiments. Maximum surface temperature was reached for a 35 mm thick matrix, which is hereby recommended for practical radiant heaters using this process. The mechanism hypothesized earlier was nearly proved with pending confirmation from reverse velocity measurements.
M.S. in Mechanical and Aerospace Engineering, May 2011
Show less

Title: AUTOMATED MANIPULATION OF NANOSCALE STRUCTURES VIA AN ATOMIC FORCE MICROSCOPE
Creator: Xu, Kangmin
Date: 2013, 2013-05
Description: As a useful tool for both imaging and modifying nanoscale structures, atomic force microscopes (AFM) have drawn many researchers’ attention,...
Show moreAs a useful tool for both imaging and modifying nanoscale structures, atomic force microscopes (AFM) have drawn many researchers’ attention, but there are still many challenges such as lack of visual feedback during manipulation. In this dissertation, an AFM based nano manipulation system has been developed to modify the nanoscale structures including manipulation of nano particles, carbon nanotubes (CNTs) and indentation of the polymer substrate. These operations have been further assisted by real-time feedback such that AFM can be used to image, sense and manipulate nanoscale objects simultaneously. To address critical issues in AFM based nano manipulation, several methods have been developed to enhance the process of manipulation. In nano particle manipulation, a method called sequential parallel pushing (SPP) is presented for efficient and automated nano particle manipulation. Instead of using tip scanning to fully locate the particle center, this method uses contact loss detection to get the longitudinal position of particle and one scan line perpendicular to the pushing direction to determine the lateral position of the particle center. In nano indentation, computer-aided design (CAD) geometry processing has been integrated with an AFM based nano indentation process which enables the fabrication of complex geometric features. Machining parameters have been investigated and procedure to determine them have been demonstrated. In the localization of deformable nanoscale objects, two localization methods for localizing CNTs and nanowires have been introduced. They can perform accurate positioning and reconstruction of sample shapes while being manipulated. Successive manipulation strategies thus can be developed based on the developed fast localization schemes.
PH.D in Mechanical Engineering, May 2013
Show less

repository.iit

Search the repository

Pages

Pages

Enabled Filters

Refine Results

Type

Date

Academic status of creator

Subject

Creator

Rights