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Title: A NOVEL METHOD FOR THE IMPLEMENTATION OF STRUCTURAL CONTACT IN FINITE ELEMENT METHODS OFFERING SIMPLIFIED TREATMENT OF ENERGY DISSIPATION
Creator: Grudzinski, James John
Date: 2012-04-24, 2012-05
Description: A novel method for implementing contact/impact in an implicit nite element formulation is presented. The method uses the ideas of buoyancy to...
Show moreA novel method for implementing contact/impact in an implicit nite element formulation is presented. The method uses the ideas of buoyancy to enforce the normal contact constraint and a velocity dependent force to model energy dissipation. Upon contact (penetration) a normal force equal to the depth of penetration times a target weight density (di erent and much larger than the actual material weight density) creates a normal pressure on the contacting body. In addition to the buoyancy force, the penetrating surface area is subjected to a drag-like force that acts in a direction opposite the velocity vector of the penetrating node of the contacting body . This rate dependence is broken up into components tangential and normal to the target surface. The normal component of the drag performs two functions. First it provides for an energy absorbing mechanism similar to a coe cient of restitution for modeling non-conservative systems. Secondly, it can provide damping (analogous to mathematical damping) which can aid in solution convergence. The tangential component of the damping force serves the function of modeling friction in a simpli ed manner. The method applies contact forces in the manner of external forces and as such lends itself well to simpli ed contact detection schemes which rely on functional representation of bodies. The method is described and demonstrated through several examples including a comparison to experimental data.
Ph.D. in Mechanical and Aerospace Engineering, May 2012
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Title: MESOSCALE DEFORMATION IN A 9310 STEEL AND 2139 ALUMINUM ALLOY
Creator: Snyder, David
Date: 2012-09-10, 2012-12
Description: As technology continues to develop, the need for materials with superior structural performance grows. In recent years, the design of such...
Show moreAs technology continues to develop, the need for materials with superior structural performance grows. In recent years, the design of such high integrity alloys has led to a need for a more fundamental understanding of the deformation response of materials under various loading conditions. In this study, the deformation response of two high performance, high stacking fault metallic alloys are investigated. It has long been known that deformation in high stacking fault metals is a complex process of dislocation interactions that vary substantially with the loading conditions of strain, strain rate and temperature, as well as the chemistry and processing history of the alloy. The flow behavior and recrystallization response of a 9310 steel alloy deformed in the ferrite temperature range were studied in this work. Samples were compressed under various conditions of strain, strain rate and temperature using a Gleeble thermo-mechanical simulator. Deformation was characterized by both qualitative and quantitative means, using standard microscopy, electron backscatter diffraction (EBSD) analysis and flow stress modeling. The results indicate that deformation is primarily accommodated through dynamic recovery in sub-grain formation. EBSD analysis shows a continuous increase in sub-grain boundary misorientation with increasing strain, ultimately producing recrystallized grains from the sub-grains at high strains. This suggests that a sub-grain rotation recrystallization mechanism predominates in this temperature range. Demonstrated trends include a decreasing mean dynamically recrystallized grain size with increasing strain and Zener-Hollomon parameter, and an increasing recrystallized fraction with increasing strain. Another high stacking fault metal that has garnered a great deal of attention for its possible high performance structural applications is the 2139 aluminum alloy. In this study, the effect of chemistry and strain on the deformation response of the alloy system is investigated. 2139 aluminum is a very complex alloy, with multiple strengthening phases and mechanisms contributing to its overall high structural integrity compared to other aluminum alloys in its class. While the structural performance and TEM-scale deformation behavior of this alloy have been extensively analyzed, grain-scale microstructural features of deformation have not been well characterized. In addition, the contributions of each strengthening mechanism in the alloy are not well established. To characterize the deformation response of the alloy, alloys of various chemistries were produced and subjected to room temperature compression testing, in order to isolate and establish the effects of the major strengthening mechanisms on the overall behavior. Through electron backscatter diffraction analysis, the microstructural features of deformation generated in the alloys under these conditions were characterized, and the evolution and distribution of strain on a grain-scale was analyzed. Differences in deformation behavior with alloy chemistry were established by tracking differences in the evolution of lattice rotations with strain in the several alloys. It was determined that, for alloys subjected to artificial aging, the refinement in scale and distribution of the precipitate structure represents the greatest decrease in the development of lattice rotations with strain. This represents a first study into the room temperature, grain-scale deformation response of a heavily alloyed aluminum alloy, and the effect of alloy chemistry and precipitate structure on the deformation behavior of a 2139 aluminum alloy. As a preface to this study, a thorough review of the current state of literature on the deformation response of aluminum alloys was compiled as well.
M.S. in Materials Science and Engineering, December 2012
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Title: The time factor in the operation of dry pipe sprinkler system
Creator: Metz, F. W., Moore, W. W., Schultz, W. E.
Date: 2009, 1911
Publisher: Armour Institute of Technology
Description: http://www.archive.org/details/timefactorinoper00metz
Thesis (B.S.)--Armour Institute of Technology

Title: KILOMETER-SPACED GNSS ARRAY FOR IONOSPHERIC IRREGULARITY MONITORING
Creator: Su, Yang
Date: 2017, 2017-05
Description: This dissertation presents automated, systematic data collection, processing, and analysis methods for studying the spatial-temporal...
Show moreThis dissertation presents automated, systematic data collection, processing, and analysis methods for studying the spatial-temporal properties of Global Navigation Satellite Systems (GNSS) scintillations produced by ionospheric irregularities at high latitudes using a closely spaced multi-receiver array deployed in the northern auroral zone. The main contributions include 1) automated scintillation monitoring, 2) estimation of drift and anisotropy of the irregularities, 3) error analysis of the drift estimates, and 4) multi-instrument study of the ionosphere. A radiowave propagating through the ionosphere, consisting of ionized plasma, may su↵er from rapid signal amplitude and/or phase fluctuations known as scintillation. Caused by non-uniform structures in the ionosphere, intense scintillation can lead to GNSS navigation and high-frequency (HF) communication failures. With specialized GNSS receivers, scintillation can be studied to better understand the structure and dynamics of the ionospheric irregularities, which can be parameterized by altitude, drift motion, anisotropy of the shape, horizontal spatial extent and their time evolution. To study the structuring and motion of ionospheric irregularities at the sub-kilometer scale sizes that produce L-band scintillations, a closely-spaced GNSS array has been established in the auroral zone at Poker Flat Research Range, Alaska to investigate high latitude scintillation and irregularities. Routinely collecting lowrate scintillation statistics, the array database also provides 100 Hz power and phase data for each channel at L1/L2C frequency. In this work, a survey of seasonal and hourly dependence of L1 scintillation events over the course of a year is discussed. To efficiently and systematically study scintillation events, an automated low-rate scintillation detection routine is established and performed for each day by screening the phase scintillation index. The spaced-receiver technique is applied to cross-correlated phase and power measurements from GNSS receivers. Results of horizontal drift velocities and anisotropy ellipses derived from the parameters are shown for several detected events. Results show the possibility of routinely quantifying ionospheric irregularities by drifts and anisotropy. Error analysis on estimated properties is performed to further evaluate the estimation quality. Uncertainties are quantified by ensemble simulation of noise on the phase signals carried through to the observations of the spaced-receiver linear system. These covariances are then propagated through to uncertainties on drifts. A case study of a single scintillating satellite observed by the array is used to demonstrate the uncertainty estimation process. The distributed array is used in coordination with other measuring techniques such as incoherent scatter radar and optical all-sky imagers. These scintillations are correlated with auroral activity, based on all-sky camera images. Measurements and uncertainty estimates made over a 30-minute period are made and compared to a collocated incoherent scatter radar, and show good agreement in horizontal drift speed and direction during periods of scintillation for cases when the characteristic velocity is less than the drift velocity. The methods demonstrated are extensible to other zones and other GNSS arrays of varying size, number, ground distribution, and transmitter frequency.
Ph.D. in Mechanical and Aerospace Engineeering, May 2017
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Title: SYNTHESIS OF NANOPLATE STRUCTURES IN NI-BASED ALLOYS VIA DISCONTINUOUS PRECIPITATION
Creator: Zhou, Yang
Date: 2017, 2017-07
Description: Nanostructured materials are of increasing interest due to their potential for use in numerous applications including catalysis and filtration...
Show moreNanostructured materials are of increasing interest due to their potential for use in numerous applications including catalysis and filtration. Methods of synthesizing nanomaterials often include chemical techniques producing individual particles, which gives rise to issues of agglomeration and containment, and the processes are difficult to scale-up. This work is directed at addressing issues of the occurrence and kinetics of self-assembly and structural alignment of nanostructures, which involves the discontinuous precipitation transformation followed by selective dissolution. This synthesis method has been demonstrated using a Ni-49at.%Co-12at.%Al alloy. A complete discontinuous transformation in the Ni 49-12 alloy can be achieved in times as short as 30min. Thus, the large-scale production of such structures is feasible using conventional heat treatment facilities. The synthesis technique is generally applicable to any alloy system in which DP goes to completion and one phase can be selectively removed. The nanoplates are self-assembled, self-supported and well aligned if the precipitate is coherent with the matrix. In order to control the process it is necessary to understand the phase equilibria involving γ, γ′ and β phases in the Al-Co-Ni system. This has been investigated both experimentally and computationally. The isothermal sections at 1100°C and 800°C as well as a partial liquidus projection were determined which result in modifications to previously published work. Comparing the experimental results with the calculated results using Thermo-Calc (TCNI8), there is reasonable agreement. The predicted separation of the γ phase into a two-phase ferromagnetic and paramagnetic region has never been observed experimentally in this or other published work. Future work should explore the ferromagnetic and paramagnetic phase separation as predicted using Thermo-Calc to verify its occurrence in this system. The nanostructured material produced by complete DP transformation may have interesting mechanical properties and these have been studied to a limited extent in this work. The hardness tests show that with decreasing annealing temperature to 600°C, the hardness of certain samples increases significantly due to the precipitation of second phase. The tensile and creep properties of alloy samples with DP phase present were also investigated. The results imply that the occurrence of DP will have a favorable effect on the tensile strength of the sample while lowering the ductility at the same time. A method to generate serrated grain boundaries based on the DP transformation is proposed. Such structures are expected to increase the creep resistance. This was found to be the case in a limited temperature and loading range. Higher temperature or stress levels lead to DP occurrence and cause negative effects on the creep resistance compared to conventionally processed material. The Curie temperature in the Al-Co-Ni alloy system was also studied and determined using a combined magnetic TG and DSC method. A ternary contour map of the Curie temperature has been constructed. From the contour map, the Curie temperature was seen to decrease from high Co, low Al content samples to low Co, high Al samples bypassing a platform at mid Co content. A nonlinear surface fitting was made through a Exponential2D model, the function is helpful for the prediction of Curie temperature of γ phase in Al-Co-Ni alloy system. This method also provides a novel idea of detecting phase transformation and precipitation through thermo-magnetically analyzing the magnetic behavior of the alloys.
Ph.D. in Materials Science and Engineering, July 2017
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Title: Analysis of Maltese Cross Specimens to Determine Three-Dimensional Yield Surfaces
Creator: Chaudesaygues, Ludwig
Date: 2011-11-29, 2011-12
Description: Yield behavior of extremely porous solid foams under multiaxial states of stress is of significant importance because, unlike pressure...
Show moreYield behavior of extremely porous solid foams under multiaxial states of stress is of significant importance because, unlike pressure independent yield response of the majority of engineering materials, solid foams exhibit quadratic as well as linear dependence on hydrostatic stress component in their yield behavior. Therefore, there exists a critical need to analyze and use specimen geometries that allow biaxial and triaxial experiments through which yield surface can be probed under varying amounts of mean stress. This study investigates, through FE analysis, the feasibility of Maltese-Cross (MC) specimen geometry as a potential candidate for using in biaxial and triaxial experiments. Although solid foams have a pressure dependent yield behavior, the current study adopted a linear elastic-hardening J2 flow rule to keep the analysis reasonably simple and focus on the fundamental effect of specimen geometry on strain field and, more importantly, the extraction of yield point from multiaxial force-displacement data. One must recognize that in multiaxial experiments, particularly in triaxial loading, forces and displacements experienced by the nominal gage section cannot be directly measured for practical reasons. Instead, far field forces and displacements have to be used to calculate average measures of stress and strain within the gage section. This study shows through FE analyses that MC specimens can be used to determine the onset of macroscopic yielding under varying amount of mean stress component, provided that certain stress/strain paths, which cause premature deformation localization out of the gage section, are avoided.
M.S. in Mechanical and Aerospace Engineering, December 2011
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Title: DELAYING THE ONSET OF ROTATING STALL IN AN AXIAL COMPRESSOR
Creator: Thomas, Seth
Date: 2011-04-12, 2011-05
Description: The optimal performance of axial compressors is crucial in a number of appli- cations, including power plants and gas turbine engines. Their...
Show moreThe optimal performance of axial compressors is crucial in a number of appli- cations, including power plants and gas turbine engines. Their efficiency is limited by the onset of stall, when the pressure rise across the compressor drops suddenly and destructive flow patterns emerge. Because of this, all compressors operate at conditions away from the stall point, but with an accompanying penalty in efficiency. The objective of this study is to examine the detailed fluid dynamic processes lead- ing to stall and devise a scheme of active flow control to delay stall onset, allowing compressors to operate safely much closer to the stall point and at greater efficiency. This is done on the low speed axial compressor rig in the Fluid Dynamics Research Center at the Illinois Institute of Technology. Results indicated that the stall cell appears at a flow coefficient, φ = 0.292 and that it is small, located close to the casing, rotating with the rotor blade row, but at 55% of the rotor rotation rate. Detailed stall inception investigation revealed that small amplitude modal waves instigated flow breakdown upstream of the rotor blade row, causing a spike stall cell to develop. This spike cell rotates very quickly (70%) and grows rapidly into a finite stall cell, slowing its rotation rate as it becomes fully developed. Stagnation pressure in the wake of the rotor blades was phase locked to both the rotor and stall cell rotation, allowing phase-averaging techniques to reveal the averaged stall cell structure. A new actuator was designed for rotating stall control. Based on the stall inception results, a disturbance rejection scheme was devised to interact with the incipient stall cell, preventing its growth into a finite stall cell. The single blade was studied in a number of open loop control experiments, which indicated that pulsing at 2psi over a range of frequencies can inhibit stall inception, extending the operating range by 0.4% mass flow, thus stabilizing a previously unstable operating point.
M.S. in Mechanical and Aerospace Engineering, May 2011
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Title: A study of the retardation of combustion on passing thru wire screens place in a closed pipe
Creator: Mcdiarmid, E. Wallace
Date: 2009, 1916
Publisher: Armour Institute of Technology
Description: http://www.archive.org/details/studyofretardati00mcdi
Thesis (B.S.)--Armour Institute of Technology

Title: EFFECT OF STRAWBERRY ANTIOXIDANTS ON OXIDATIVE STRESS IN INSULIN RESISTANT INDIVIDUALS: A DOSE RESPONSE STUDY
Creator: Vijayakumar, Lakshmi Prabha
Date: 2014, 2014-05
Description: Oxidative and inflammatory stress is associated with chronic disease development and progression. Recent studies suggest that consumption of...
Show moreOxidative and inflammatory stress is associated with chronic disease development and progression. Recent studies suggest that consumption of fruits and vegetables rich in antioxidant compounds attenuate oxidative stress and inflammation. Strawberries are abundant in polyphenolic compounds with antioxidant properties, which have attracted research attention for their possible health benefits. The aim of the project was to determine whether the antioxidant properties of strawberries formulated in a beverage would dose-dependently restore oxidative stress induced by a high fat/ high carbohydrate meal in insulin resistant individuals. Plasma was collected from insulin resistant individuals (n=25) every 30-60 min over 6 h after ingestion after a 650 kcal high fat/ high carbohydrate meal accompanied with a beverage containing 0, 10, 20 or 40 g freeze-dried strawberry powder. The antioxidant capacity of test beverages containing 10, 20 and 40 g strawberry powder were 9.31± 0.66, 19.10 ± 0.60 and 33.57 ± 1.75 μmol Trolox equivalents/mL based on the Oxygen Radical Absorbance Capacity (ORAC) assay. The ORAC value for the placebo (0 g) was below the detectable limits. Biologically relevant oxidative stress was determined using the ORAC assay to estimate antioxidant capacity of the plasma and oxidation of low density lipoprotein (ox-LDL) using an ELISA assay to determine the oxidative damage. Assessment of ox-LDL over 6 hr revealed a significant effect of time (p<0.0001), however no significant difference between the treatment dosages was evident (p>0.05). A marginal treatment by time interaction suggested possible time specific differences between treatments. The evaluation of antioxidant capacity of the plasma was split into assessment of the hydrophilic and lipophilic fractions. Hydrophilic ORAC results showed ix no significant differences between test beverages over 6 hr (p>0.05), including effects of time or treatment by time interactions (p>0.05). The lipophilic ORAC also did not reveal significant differences between treatments (p>0.05). Overall, it appears that beverages with different “doses” of antioxidant capacity did not result in dose-dependent changes in oxidative stress in insulin resistant individuals. There was a trend for protection of ox-LDL by the 20 g strawberry beverage revealed by differences among treatments at 240 min compared to the placebo/0 g strawberry beverage. The findings suggest that antioxidant food properties do not translate directly to plasma antioxidant capacity as measured by ORAC and alternative mechanisms are likely responsible for biological antioxidant effects of strawberry.
M.S. in Mechanical and Aerospace Engineering, May 2014
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Title: SYNTHESIS, PURIFICATION AND CRYSTAL GROWTH OF INDIUM IODIDE SEMICONDUCTORS
Creator: Bertorello, Charles
Date: 2012-04-23, 2012-05
Description: The indium monoiodide (InI) semiconductor is a promising candidate for Gamma-ray and X-ray radiation detector devices. The high atomic number...
Show moreThe indium monoiodide (InI) semiconductor is a promising candidate for Gamma-ray and X-ray radiation detector devices. The high atomic number of indium (In) and iodine (I), along with high density, give the InI detector a higher photon stopping power (attenuation coe cient) compared to germanium based detectors and comparable to that of CdT e. Based on the previous research on melt synthesis and vapor synthesis by Dr. Ostrogorsky at Rensselaer Polytechnic Institute (RPI) and Dr. Burger at Fisk University from 2006 to 2009, the present work improves the purity of indium monoiodide by demonstrating the e ciency of zone re ning of this material. A segregation coe cient study is presented based on a Glow Discharge Mass Spectrometry (GDMS) and an Instrumental Gas Analysis (IGA) analyses performed by Evans Analytical Group (EAG). Two indium monoiodide crystals were grown using the Vertical Bridgman technique and analyses done on one of the crystals shown a resistivity of 3 109 .cm which is the second highest value reported. Indium monoiodide synthesized and puri ed in this current study was used to grow several Czochralski crystals.
M.S. in Mechanical, Materials, and Aerospace Engineering, May 2012
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Title: NOVEL METHOD OF MANUFACTURING HYDROGEN STORAGE MATERIALS COMBINING WITH NUMERICAL ANALYSIS BASED ON DISCRETE ELEMENT METHOD
Creator: Xuzhe, Zhao
Date: 2015, 2015-07
Description: High efficiency hydrogen storage method is significant in development of fuel cell vehicle. Seeking for a high energy density material as the...
Show moreHigh efficiency hydrogen storage method is significant in development of fuel cell vehicle. Seeking for a high energy density material as the fuel becomes the key of wide spreading fuel cell vehicle. LiBH4 + MgH2 system is a strong candidate due to their high hydrogen storage density and the reaction between them is reversible. However, LiBH4 + MgH2 system usually requires the high temperature and hydrogen pressure for hydrogen release and uptake reaction. In order to reduce the requirements of this system, nanoengineering is the simple and efficient method to improve the thermodynamic properties and reduce kinetic barrier of reaction between LiBH4 and MgH2. Based on ab initio density functional theory (DFT) calculations, the previous study has indicated that the reaction between LiBH4 and MgH2 can take place at temperature near 200°C or below. However, the predictions have been shown to be inconsistent with many experiments. Therefore, it is the first time that our experiment using ball milling with aerosol spraying (BMAS) to prove the reaction between LiBH4 and MgH2 can happen during high energy ball milling at room temperature. Through this BMAS process we have found undoubtedly the formation of MgB2 and LiH during ball milling of MgH2 while aerosol spraying of the LiBH4/THF solution. Aerosol nanoparticles from LiBH4/THF solution leads to form Li2B12H12 during BMAS process. The Li2B12H12 formed then reacts with MgH2 in situ during ball milling to form MgB2 and LiH. Discrete element modeling (DEM) is a useful tool to describe operation of various ball milling processes. EDEM is software based on DEM to predict power consumption, liner and media wear and mill output. In order to further improve the milling efficiency of BMAS process, EDEM is conducted to make analysis for complicated ball milling process. Milling speed and ball’s filling ratio inside the canister as the variables are considered to determine the milling efficiency. The average and maximum speed of balls is critical to affect the collision force among balls. High collision force can be achieved by applying large torque on the milling shaft. The high milling speed and large ball’s filling ratio increase the torque and average speed of balls. However, the high average speed and large torque lead to non-uniformed milled material. Therefore, appropriate milling speed and ball’s filling ratio are ought to be selected to have better milled materials. The results of this study lead to the feasibility of LiBH4 + MgH2 system for reversible hydrogen storage application near ambient temperature. Applying appropriate ball’s filling ratio and milling speed can improve the milling efficiency of BMAS method.
M.S. in Material Science Engineering, July 2015
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Title: NON-NEWTONIAN EFFECTS IN HEMODYNAMIC SIMULATIONS OF THE CEPHALIC VEIN IN END STAGE RENAL DISEASE PATIENTS
Creator: Mahmoudzadeh Akherat, Seyed Mohammad Javid
Date: 2013, 2013-12
Description: The objective of this research is the determination of Hemodynamic Parame- ters (HDP) in End Stage Renal Disease (ESRD) patients which is done...
Show moreThe objective of this research is the determination of Hemodynamic Parame- ters (HDP) in End Stage Renal Disease (ESRD) patients which is done via implemen- tation of Computational Fluid Dynamics (CFD) in a two dimensional computational domain which provides a non-invasive and cost e ective means of studying the pa- tient population. The medical procedure needed for these patients is essential for the success of chronic hemodialysis. The most common medical procedure currently in this eld for creating vascular access (VA) are arteriovenous stulae (AVF). However, there are many access failures reported in these patients mainly due to Cephalic Arch Stenosis (CAS), which is related to the progression of intimal hyperplasia. Although various access techniques have been developed to address this issue, still hemodialysis access dysfunctions remains one of the main causes of mortality in the hemodialysis patient population. The expense of providing medical care to this patients population for the placement and maintenance of the vascular access was estimated to be 23.9 billion dollars in 2007 in the United States alone according to United States Renal Database System (USRDS). As stated above, it is our intention to observe a cohort of ESRD patients who received VA and simulate their blood ow through their cephalic vein with their spe- ci c HDP and characteristics. In order to perform these simulations, proper viscosity models have to be taken into consideration to increase the accuracy of the outcome of the numerical solution to Navier-Stokes equations. Many articles have been published to address the proper use of constitutive functions in simulation of blood ow. However, the choice of adequate viscosity function for CFD blood ow simulation in ESRD patients receiving AVF and a ma- nipulated vascular system in general has not received proper attention. Furthermore, it was discerned that the correct choice of viscosity function to capture the non- xii Newtonian behavior of blood is of utmost importance in this context since the ESRD patient population experience drastic alteration in blood viscosity throughout the hemodialysis treatment. Various viscosity functions have been tested for this pur- pose, namely, Quemada, Walburn-Schenck and Modi ed Cross. The results exhibit no major di erences in the velocity eld and general ow characteristics compared to a corresponding identical Newtonian blood ow simulation for Reynolds of 500. The results indicate that the choice of Newtonian viscosity to simulate the blood ow in ESRD patients with VA is acceptable. However, the Newtonian simulation of these ows may over predict the sites prone to stenosis and Intimal Hyperplasia (IH) since these simulations tend to exhibit lower Wall Shear Stress (WSS) values in the recircu- lation regions compared to non-Newtonian simulations. Sites of low WSS are thought to be contributory factors to IH. Hence, the use of proper non-Newtonian constitu- tive models is suggested in this context. The di erences between non-Newtonian and Newtonian assumptions are further ampli ed when unsteady cases with Reynolds of 1000 are concerned. Navier-Stokes solutions obtained from CFD simulations re- vealed that the discrepancies between the two assumptions are very appreciable for unsteady cases. In light of the results for unsteady cases, it was concluded that for non-physiological ows in curved vessels that are encountered in this study, the non-Newtonian assumptions is the correct choice. Further investigation is required to simulate the blood ow in a three di- mensional domain. In addition, a more thorough comprehension has to be obtained regarding the correlation of HDP with the onset and progression of CAS, particu- larly in unsteady hemodynamic ows. The etiology of stenosis in cephalic veins is of scienti c and clinical importance and needs to be separately investigated.
M.S. in Mechanical and Aerospace Engineering, December 2013
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Title: THE VAPORIZATION PHENOMENA OF FUEL DROPLETS EXPOSED TO ASYMMETRIC RADIANT HEATING USING PLANAR LASER-INDUCED FLUORESCENCE
Creator: Ammigan, Kavin
Date: 2012-04-17, 2012-05
Description: Droplet vaporization under asymmetric conditions is prevalent in many combustion related devices where fuel droplets may either experience...
Show moreDroplet vaporization under asymmetric conditions is prevalent in many combustion related devices where fuel droplets may either experience asymmetric thermal radiant heating or travel in velocity and temperature gradients. Asymmetric radiant heating is particularly common in spray flames, counter-flow diffusion flames, regions close to the walls of conventional combustion chambers and more importantly in liquid-fueled microcombustors. In this study, experiments are carried out to observe how droplets vaporize when exposed to asymmetric radiant heating. The experimental set-up consists of applying radiant heating, through a radiant panel heater, to one face of a monodisperse droplet stream while using the planar-laser induced fluorescence (PLIF) diagnostic tool to reveal the spatial vapor distribution around vaporizing droplets. Since most fuels are made up of multiple components, bicomponent droplets are also investigated. Pure acetone droplets as well as mixtures of acetone/alkanes (octane and hexane) and acetone/alcohols (ethanol and 2-propanol) droplets are investigated. Results in the form of PLIF images, reveal asymmetric vapor distributions around the droplets with the apparent induction of Stefan flow from the irradiated droplet surface. Such phenomena have not previously been reported in the literature and have relevance to the overall fuel vaporization process as well as subsequent ignition and pollutant formation processes. To further investigate the experimental results, a convective and radiative heat transfer model is employed to simulate the droplets under corresponding experimental conditions. Results from the model show convective cooling and a strong thermal radiation absorption near the droplets’ surface. The induced asymmetric Stefan flow observed experimentally is therefore a consequence of the high thermal radiation absorption at the droplets’ surface. This study gives both experimental and theoretical results of the vaporization phenomena of asymmetrically irradiated fuel droplets with varying compositions, diameters and irradiation temperatures.
Ph.D. in Mechanical and Aerospace Engineering, May 2012
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Title: ANALYSIS AND CONTROL OF COMPRESSION-IGNITION AND SPARK-IGNITED ENGINES OPERATING WITH DUAL-FUEL COMBUSTION STRATEGY
Creator: Kassa, Mateos
Date: 2017, 2017-07
Description: In recent years, the implementation of a dual-fuel combustion strategy has been explored as a means to improve the thermal efficiencies of...
Show moreIn recent years, the implementation of a dual-fuel combustion strategy has been explored as a means to improve the thermal efficiencies of internal combustion engines while simultaneously reducing their emissions. The dual-fuel combustion strategy was introduced in compression ignition engines to control the combustion phasing by varying the proportion of two simultaneously injected fuels, and altering the combustion timing. The dual-fuel injection strategy also allowed to extend the load limitation of advanced combustion engines, since the two injected fuel ignite in succession reducing the high peak pressures that generally act as a limiting factor. In spark-ignited (SI) engine, the implementation of a dual-fuel combustion strategy serves as an alternative approach to avoid knock (the inadvertent auto-ignition of the fuel mixture). Although conventional engines rely on delaying spark timing to avoid knocking cycles (which significantly reduces the thermal efficiency), the dual-fuel SI engine rely on the simultaneous injection of a low knock resistance and high knock resistance fuel to dynamically adjust the fuel resistance to knock as required. The dual-fuel SI engine thereby successfully suppresses knock without compromising the engine efficiency. Despite the benefits of the dual-fuel combustion strategy, several challenges arise in its implementation, especially when it is implemented along with other advanced combustion strategy leveraging variable valve timing, exhaust gas recirculation, turbocharging, and so forth. This study explores some of these challenges and addresses them from a control standpoint. Cylinder-to-cylinder variations is identified as one of the main challenges. An in-cylinder oxygen estimation strategy and modification to the conventional fueling strategy are proposed as approaches to reduce the combustion variations. In SI engines, the valve dynamics in transient operations are shown to negatively impact the dual-fuel control strategy. The effect of the valve timing on knock propensity and the resulting effect on the fueling strategy is investigated. Finally, the dual-fuel SI engine relies on measurements of the combustion intensity to adjust the fuel split between the low RON and high RON fuel. The implementation of a conventional knock control is shown to be counterintuitive for dual-fuel SI engines due to the highly reactive nature of the controller and the deterministic approach that assumes cycle-to-cycle correlation of the combustion intensity. Statistical investigation of the combustion intensity metric is conducted to identify key properties that can be leveraged for more effective control strategy.
Ph.D. in Mechanical, Material and Aerospace Engineering
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Title: POWDER CHARACTERIZATION AND PROCESS OPTIMIZATION FOR COLD COMPACTION AND SINTER APPLICATIONS OF COMMERCIALLY PURE TITANIUM POWDERS
Creator: Araci, Kerem
Date: 2011-08, 2011-07
Description: Near net shape manufacturing using powder metallurgy (P/M) technology and processes can significantly reduce material waste and cost during...
Show moreNear net shape manufacturing using powder metallurgy (P/M) technology and processes can significantly reduce material waste and cost during component fabrication. This study includes all the efforts to evaluate near net shape consolidation processes utilizing several different commercially pure titanium (CP-Ti) powders, focusing on the one produced by Armstrong Process® technology. Powder characteristics were studied in terms of morphology, particle size distribution, apparent and tap densities, and chemistry. Desired particle size distributions and higher powder densities were observed for HDH powders, while unique coral-like morphology was examined for the Armstrong Process® powder. Ball milling of the Armstrong Process® powder was systematically investigated by evaluating the impact on the particle size distribution, powder density and chemistry. Cold-uniaxial compaction of the milled powders was also evaluated in terms of theoretical density and green strength as a function of compaction pressure and lubrication techniques. Green densities were varied from 79 % to 91% for different powder compacts in different compaction conditions. Excellent green compaction of 145 MPa was approached by green compacts of Armstrong Process® powder. Sinter processing of the green compacts was investigated to approach relatively advanced tensile and flexural properties as a function of process temperature, time and heating rate. Near net-shape components which were fabricated by pressing and sintering were shown to achieve near-full densification with up to 97% of the theoretical density. Properties of P/M materials after the consolidation process were characterized and compared to those of conventionally produced materials.
M.S. in Materials Science and Engineering, July 2011
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Title: CLOSED-LOOP CONTROL GUST SUPPRESSION AT OF LIFT FOR LONGITUDINAL LOW REYNOLDS NUN4BERS
Creator: Kerstens, Wesley
Date: 2011-07-26, 2011-07
Description: Experiments are conducted to investigate the ability of variable pressure, pulsed-blowing actuators and zero-net-mass-flux actuators to...
Show moreExperiments are conducted to investigate the ability of variable pressure, pulsed-blowing actuators and zero-net-mass-flux actuators to maintain a constant lift force on a low aspect ratio, semi-circular wing in a longitudinally gusting flow. Dynamic models of the lift response to actuation and the lift response to longitudinal gusting are obtained through modern black-box system identification methods. Robust, H∞, closed-loop controllers are synthesized using a mixed sensitivity, loopshaping approach. An additional feed-forward disturbance compensator is designed based on a model of the unsteady aerodynamics. The controllers show suppression of lift fluctuations at low gust frequencies, f < 1Hz (reduced frequency, k < 0.09). At higher frequencies, the control performance degrades due to limitations related to the time for a disturbance, created by the actuators, to convect over the wing and establish the flow field that leads to enhanced lift on the wing. Similar limitations are observed for both wings even though the bandwidth of the zero-net-mass-flux actuators is an order of magnitude higher than that of the pulsed-blowing actuators.
M.S. in Mechanical and Aerospace Engineering, July 2011
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Title: Effect on entrapped air on the action of wet pipe alarm valves
Creator: Ahern, A. J., Mckarahan, E. V., Oberfelder, W. S., Tregay, Jno
Date: 2009, 1909
Publisher: Armour Institute of Technology
Description: http://www.archive.org/details/effectonentrappe00aher
Thesis (B.S.)--Armour Institute of Technology

Title: The floor distribution of water from automatic sprinkler heads
Creator: Goppelsroeder, Roy A. C., Peterson, Leonard A, Grasse, C. A.
Date: 2009, 1916
Publisher: Armour Institute of Technology
Description: http://www.archive.org/details/floordistributio00gopp
Thesis (B.S.)--Armour Institute of Technology

Title: Floor distribution of standard automatic sprinkler heads
Creator: Kula, J. S., Foschinbaur, L. A., Schreiner, R. F.
Date: 2009, 1917
Publisher: Armour Institute of Technology
Description: http://www.archive.org/details/floordistributio00kula
Thesis (B.S.)--Armour Institute of Technology

Title: CYCLIC THERMAL TREATMENT
Creator: Gu, Sijie
Date: 2015, 2015-12
Description: Cyclic thermal treatment has the potential to improve energy efficiency of thermal processing. It has been shown that in some cases, the...
Show moreCyclic thermal treatment has the potential to improve energy efficiency of thermal processing. It has been shown that in some cases, the productivity was enhanced by the cyclic thermal treatment operation. In order to investigate the cyclic thermal treatment effect, Copper-Nickel interdiffusion couples were investigated. When the Cu-Ni interdiffusion couple showed positive results, the cyclic thermal treatment was applied to pack carburization and gas carburization of steel. The Cu-Ni interdiffusion couples were annealed with different time-temperature profiles for 5 days. There are three types of time-temperature profile; isothermal, symmetric, and asymmetric cyclic thermal treatment. After thermal treatment, concentration-distance profiles were. Based on the concentration-distance profile, the interdiffusion coefficients of different time-temperature profiles were calculated. The interdiffusion coefficient of the diffusion couple with a ramp rate of 1°C/min had a higher diffusion coefficient than that of the diffusion couple annealed isothermally at the equivalent temperature, 863°C, which means that cyclic thermal treatment has the effect of accelerating diffusion. When the ramp rate was 5ºC/min interdiffusion coefficients were higher than that of the diffusion couple annealed isothermally at the maximum temperature. However, when the ramp rate was increased to 10°C/min, the diffusion coefficient decreased to almost the same as the interdiffusion coefficient of the diffusion couple at the equivalent temperature. After achieving a promising result for the Cu-Ni diffusion couples, we expanded the cyclic thermal treatment to carburizing. The temperature range for cyclic pack carburization was 850° to 950°C. Increasing the cyclic ramp rate resulted in an increase in the case depth. Due to the setup of the pack carburization, the maximum cooling rate achievable is 5°C/min. In order to reach a higher ramp rate, an induction heating gas carburization system was setup. The temperature range for the cyclic induction heat gas carburization was 850°C to 950°C. For the cyclic induction heat gas carburization with increase in ramp rate, the case depth increased. The sample induction gas carburized at a ramp rate of 20°C/min had a deeper case depth than the sample induction gas carburized isothermally at 904.4°C, the equivalent temperature. The first test showed the sample induction gas carburized with a ramp rate of 20°C/min had a deeper case depth than the sample induction gas carburized isothermally at 950° C. With this we draw the conclusion that the cyclic induction gas carburization can achieve a deeper case depth than the isothermal at equivalent temperature induction gas carburization.
Ph.D. in Materials Science and Engineering, December 2015
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