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(21 - 40 of 315)
Pages
- Title
- The thermal conductivity of various forms of tile and their value as fireproofing materials
- Creator
- Anderson, S. W., Chamberlin, J. F.
- Date
- 2009, 1915
- Publisher
- Armour Institute of Technology
- Description
-
http://www.archive.org/details/thermalconductiv00ande
Thesis (B.S.)--Armour Institute of Technology
- Title
- The study of an air washer
- Creator
- Armspach, Otto W., Haines, E. Wilfred
- Date
- 2009, 1917
- Publisher
- Armour Institute of Technology
- Description
-
http://www.archive.org/details/studyofairwasher00arms
Thesis (B.S.)--Armour Institute of Technology
- Title
- B-SPLINE BASED ROBUST FORMULATION IN TOPOLOGY OPTIMIZATION
- Creator
- Gu, Yu
- Date
- 2014, 2014-12
- Description
-
In this thesis, we extend the B-spline based density representation to robust topology optimization. The B-spline based representation has...
Show moreIn this thesis, we extend the B-spline based density representation to robust topology optimization. The B-spline based representation has been shown to have the ability of preventing checker-boards. With separate analysis and design mesh, the B-spline based filter is also competitive on computation storage compared with usual density filter. However, the current B-spline based representation is not robust where gray transitions exist. The recent proposed robust formulation highlights the manufacturability that simulates under- or over- etching designs compared with intermediate design. The robustness is demonstrated through three test cases. The minimum length control for quadratic B-splines is analytically derived with respect to knot span size and threshold. Our study about the characteristics of rectangular domain of B-spline based representation, shows that the optimized designs are comparable to those by density filter.
M.S. in Mechanical and Aerospace Engineering, December 2014
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- Title
- Transmission efficiencies of belting
- Creator
- Marks, Robert Edward
- Date
- 2009, 1919
- Publisher
- Armour Institute of Technology
- Description
-
http://www.archive.org/details/transmissioneffi00mark
Thesis (B.S.)--Armour Institute of Technology; Bibliography: leaf 29
- Title
- SUSTAINABLE, CONTROLLED, REACTION SYNTHESIS OF METALLIC WIRES AND STRIPS
- Creator
- Chen, Xin
- Date
- 2014, 2014-05
- Description
-
The main purpose of this work is to investigate bi and tri-metallic metal com- binations as initiators which require an ability to have a self...
Show moreThe main purpose of this work is to investigate bi and tri-metallic metal com- binations as initiators which require an ability to have a self-sustaining exothermic reaction. Through the reaction, the initiator should achieve a temperature in excess of 500 C when in contact with a thermally conducting surface. Also the initiator must be in the form of a exible wire or strip of the order of one millimeter radius. There are four phases in my MS research project. First was identifying the potential candidate compounds for exothermic reaction. During this phase, I wrote a program using Mathematicar (Appendix A) to calculate the adiabatic temperature resulting from the reaction of di erent binary or ternary elemental combinations. The calculation took into account the speci c heats and any enthalpies of transformation occurring between room temperature and the adiabatic temperature. Based on the results of this program several suitable compositions were selected from three hun- dred candidates. The second phase was determining a methodology to manufacture selfCpropagating thin strips or wires. We attempted several methods including plate rolling, wire twisting, mechanical coating, chemical coating, and powder metallurgy. We successfully obtained self-propagating thin metal strips and wires using powder metallurgy methods. In the third phase, a transparent reaction box was constructed in order to provide a protective atmosphere (Ar gas) and connect to a data acqui- sition system to obtain the reaction temperature, initiation temperature and video materials of reactions. In the last phase, the reacted samples were characterized using Scanning Electron Microscope (SEM), Backscattered Electron detector (BSE), X-ray Di raction (XRD), Di erential scanning calorimeter (DSC), etc.
M.S. in Mechanical, Materials, and Aerospace Engineering, May 2014
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- Title
- CONSTITUTIVE BEHAVIOR AND MODELING OF AL-CU ALLOY SYSTEMS
- Creator
- Turkkan, Omer Anil
- Date
- 2013-05-07, 2013-05
- Description
-
High speed deformation events such as caused by projectile penetration, fragment impact and shock/blast loading are of great importance in...
Show moreHigh speed deformation events such as caused by projectile penetration, fragment impact and shock/blast loading are of great importance in designing materials and structures for army applications. In these events, materials are subjected to large strains, high strain rates and rapid increase in temperature due to thermoplastic heating. In such severe conditions, overall performance is determined by the evolution of flow stress, failure initiation and propagation, and commonly in the form of adiabatic shear banding. Some of 2XXX series aluminum-copper (Al-Cu) alloys are recognized for their decent ballistic properties, and therefore they have been used as an armor material for lightweight U.S. Army vehicles. Most recently, an Al-Cu-Mg-Mn-Ag alloy labeled as Al 2139-T8 has been developed and is evaluated by the U.S. Army Research Labs. because of its better ballistic properties and higher strength than its predecessors. The underlying microstructure is believed to be the key element for this superior performance. The goal of this study is to explore the effect of composition and microstructural features on overall dynamic material behavior by examining mechanical and deformation behavior of different Al-Cu material systems. Starting from the pure single crystal and polycrystalline Al structures, and adding a different element to chemical composition in each step (i.e., Cu, Mg, Mn, Ag), mechanical response of these different systems has been investigated. For all alloy systems with the exception of single crystal Al, mechanical tests have been performed at room and elevated temperatures covering quasi-static ( to ) and dynamic ( to strain rate regimes. xiv Shear-compression specimens promoting localized shear deformation have been used to explore tendency of each one of these materials to failure by adiabatic shear banding. In addition to phenomenological Johnson-Cook Model (JCM), physics based Zerrilli-Armstrong and Mechanical Threshold Models have been studied to model the constitutive response of Al-Cu alloys over a wide range of strain rates and temperatures.. An improved ZA model has been developed to better capture the trends in experimental data.
M.S. in MECHANICAL, MATERIALS, AND AEROSPACE ENGINEERING, May 2013
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- Title
- NATURAL AGING EFFECT ON DOUBLE AGED ALUMINUM ALLOY AA7075
- Creator
- Kara, Baris
- Date
- 2012-04-27, 2012-05
- Description
-
The effect of natural aging (NA) on mechanical properties in double aged aluminum alloys, AA7075, was studied by means of hardness tests,...
Show moreThe effect of natural aging (NA) on mechanical properties in double aged aluminum alloys, AA7075, was studied by means of hardness tests, tensile tests and stress corrosion cracking (SCC) tests. Natural aging can strengthen AA7075 alloys after solution heat treatment, and reaching the stable condition can take years for the alloy. Double aging (DA) is very beneficial method in terms of energy savings and productivity because this method provides the peak hardness in a much shorter time compared to single aging, and DA treatment produces hardness, yield stress and tensile stress which are comparable with those produced by SA. In this study, the alloys were naturally aged for different times before double aging treatment, and the relationship between double aging treatment and natural aging treatment was observed. The results show that different natural aging times do not significantly affect the final mechanical properties of double aged alloys. Consequently, the loading time to aging furnace after solution heat treatment does not play an important role in the double aging treatment of AA7075 alloys.
M.S. in Materials Science and Engineering, May 2012
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- Title
- THE CORRELATION BETWEEN FATIGUE PROPERTY AND PORE MORPHOLOGY OF POWDER METALLURGY TI6AL4V
- Creator
- Yan, Yingjie
- Date
- 2012-12-12, 2012-12
- Description
-
The microstructure and fatigue properties of sintered Ti-6Al-4V were investi- gated as a function of sintered density and pore morphology. A...
Show moreThe microstructure and fatigue properties of sintered Ti-6Al-4V were investi- gated as a function of sintered density and pore morphology. A quantitative analysis of microstructure was conducted to correlate with tensile and fatigue properties to understand the in uence of sintering density and pore morphology. Low cycle fatigue (LCF) using constant strain control was conducted at room temperature, R=-1 and sine waveform. High cycle fatigue (HCF) using constant stress control was conducted at room temperature, R=0.1 and sine waveform. It was found that there was no signi cant di erence in tensile strength but the fatigue endurance limit was increased by 20% when the sintering density was increased from 95% to 99%. Moreover, fatigue endurance limit was increased when the shape factor increased among three di er- ent sintering conditions(1010 -60min-690MPa, 1130 -90min-410MPa, 1250 -30min- 550MPa). Fracture surface analysis indicated that the fatigue crack initiated from the cluster of pore either at surface or at the sub-surface. The implication of pore morphology and porosity on mechanical behaviour and fatigue fracture of P/M Ti- 6Al-4V were discussed. It was estimated that the shape factor was 0.05 for A-50 and 0.07 for A-100, respectively. A polynomial relationship was found between the fatigue endurance limit and shape factor among three sintering con gurations. It was found that the PM parts with a higher shape factor had a higher fatigue endurance limit.
M.S. in Materials Science and Engineering, December 2012
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- Title
- Test of slender wooden struts for aeroplanes
- Creator
- Smith, M. A,, Kellener, W. A., Stevens, W. A.
- Date
- 2009, 1910
- Publisher
- Armour Institute of Technology
- Description
-
http://www.archive.org/details/testofslenderwoo00smit
Thesis (B.S.)--Armour Institute of Technology
- Title
- Study of the action of a four inch grinnell variable pressure alarm valve
- Creator
- Hotchkin, E. W., Pfaelzer, F. M
- Date
- 2009, 1910
- Publisher
- Armour Institute of Technology
- Description
-
http://www.archive.org/details/studyofactionoff00hotc
Thesis (B.S.)--Armour Institute of Technology, 1910 B.S. in Fire Protection Engineering,...
Show morehttp://www.archive.org/details/studyofactionoff00hotc
Thesis (B.S.)--Armour Institute of Technology, 1910 B.S. in Fire Protection Engineering, 1910
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- Title
- COATING OF BORON NITRIDE THIN FILM ON TITANIUM
- Creator
- Huang, Mairui
- Date
- 2013, 2013-12
- Description
-
To improve the wear resistance of titanium and extend its service life, coating boron nitride thin films on the surface of titanium matrix was...
Show moreTo improve the wear resistance of titanium and extend its service life, coating boron nitride thin films on the surface of titanium matrix was studied in this work. To obtain surface property enhancement, the samples were coated by isothermal sintering at 1000°C – 1400°C in a vacuum furnace for 2h, 4h or 6h. The microstructure of the thin film was investigated employing X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). To identify the composition of interlayers between BN and Ti, EDS analysis was run through the whole reaction zone. It showed that the BN was being consumed, titanium borides (TiB and TiB2), titanium nitride (TiN1-x), and solid solution of nitrogen in titanium (α-Ti (N)) layers formed at the interface between the BN coating and Ti matrix. Correspondingly, the XRD analysis indicated that TiB, TiB2, TiN, and α-Ti(N) phases were presented in good agreement with the EDS result. The layers grew fast in the sintering process which benefited from the fine grain size and highly oriented layers grown in the reaction zone. However, the well-known parabolic diffusional growth is only part of mechanisms for explaining the reactiondiffusion kinetics. The diffusion paths were obtained from the phase sequences at the interface between BN and Ti and thus could be represented on the isothermal section of the B-N-Ti ternary diagram. Moreover, the influence of the sintering temperature and the length of the actual sintering period on the layer sequences and thickness of the reaction zone were investigated. The micro-hardness test results showed that the Ti matrix with deposited BN thin films exhibited significant increased surface hardness. Obviously, the surface hardness xiii rose along with sintering temperature and holding time, and the hardness could be improved over 50%.
M.S. in Materials Science and Engineering, December 2013
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- Title
- DIRECT DIFFEOMORPHIC REPARAMETERIZATION FOR CORRESPONDENCE OPTIMIZATION IN STATISTICAL SHAPE MODELING
- Creator
- Li, Kang
- Date
- 2015, 2015-05
- Description
-
This dissertation proposes an efficient optimization approach for obtaining shape correspondence across a group of objects for statistical...
Show moreThis dissertation proposes an efficient optimization approach for obtaining shape correspondence across a group of objects for statistical shape modeling. With each shape represented in a B-spline based parametric form, the correspondence across the shape population is cast as an issue of seeking a reparametrization for each shape so that a quality measure of the resulting shape correspondence across the group is optimized. The quality measure is the description length of covariance matrix of the shape population, with landmarks sampled on each shape. The movement of landmarks on each B-spline shape is controlled by the reparameterization of the B-spline shape. The reparameterization itself is also represented with B-splines and B-spline coefficients are used as optimization parameters. We have developed formulations for ensuring the bijectivity of the reparameterization. A gradient-based optimization approach is developed, including techniques such as constraint aggregation and adjoint senstivity for efficient, direct di↵eomorphic reparameterization of landmarks to improve the group-wise shape correspondence. Numerical experiments on both synthetic and real 2D and 3D data sets demonstrate the efficiency and e↵ectiveness of the proposed approach.This dissertation proposes an efficient optimization approach for obtaining shape correspondence across a group of objects for statistical shape modeling. With each shape represented in a B-spline based parametric form, the correspondence across the shape population is cast as an issue of seeking a reparametrization for each shape so that a quality measure of the resulting shape correspondence across the group is optimized. The quality measure is the description length of covariance matrix of the shape population, with landmarks sampled on each shape. The movement of landmarks on each B-spline shape is controlled by the reparameterization of the B-spline shape. The reparameterization itself is also represented with B-splines and B-spline coefficients are used as optimization parameters. We have developed formulations for ensuring the bijectivity of the reparameterization. A gradient-based optimization approach is developed, including techniques such as constraint aggregation and adjoint senstivity for efficient, direct di↵eomorphic reparameterization of landmarks to improve the group-wise shape correspondence. Numerical experiments on both synthetic and real 2D and 3D data sets demonstrate the efficiency and e↵ectiveness of the proposed approach.
Ph.D. in Mechanical and Aerospace Engineering, May 2015
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- Title
- Vacuum jacketing vs. steam jacketing
- Creator
- Gentry, T. E., Wernick, F. E.
- Date
- 2009, 1910
- Publisher
- Armour Institute of Technology
- Description
-
http://www.archive.org/details/vacuumjacketingv00gent
Thesis (B.S.)--Armour Institute of Technology
- Title
- ASYMPTOTIC SIMILARITY IN TURBULENT BOUNDARY LAYERS
- Creator
- Duncan, Richard D.
- Date
- 2011-05-10, 2011-05
- Description
-
The turbulent boundary layer is one of the most fundamental and important applications of fluid mechanics. Despite great practical interest...
Show moreThe turbulent boundary layer is one of the most fundamental and important applications of fluid mechanics. Despite great practical interest and its direct impact on frictional drag among its many important consequences, no theory absent of significant inference or assumption exists. Numerical simulations and empirical guidance are used to produce models and adequate predictions, but even minor improvements in modeling parameters or physical understanding could translate into significant improvements in the efficiency of aerodynamic and hydrodynamic vehicles. Classically, turbulent boundary layers and fully-developed turbulent channels and pipes are considered members of the same “family,” with similar “inner” versus “outer” descriptions. However, recent advances in experiments, simulations, and data processing have questioned this, and, as a result, their fundamental physics. To address a full range of pressure gradient boundary layers, a new approach to the governing equations and physical description of wall-bounded flows is formulated, using a two variable similarity approach and many of the tools of the classical method with slight but significant variations. A new set of similarity requirements for the characteristic scales of the problem is found, and when these requirements are applied to the classical “inner” and “outer” scales, a “similarity map” is developed providing a clear prediction of what flow conditions should result in self-similar forms. An empirical model with a small number of parameters and a form reminiscent of Coles’ “wall plus wake” is developed for the streamwise Reynolds stress, and shown to fit experimental and numerical data from a number of turbulent boundary layers as well as other wall-bounded flows. It appears from this model and its scaling using the free-stream velocity that the true asymptotic form of u′2 may not become self-evident until Re ≈ 275, 000 or δ+ ≈ 105, if not higher. A perturbation expansion made possible by the novel inclusion of the scaled streamwise coordinate is used to make an excellent prediction of the shear Reynolds stress in zero pressure gradient boundary layers and channel flows, requiring only a streamwise mean velocity profile and the new similarity map. Extension to other flows is promising, though more information about the normal Reynolds stresses is needed. This expansion is further used to infer a three layer structure in the turbulent boundary layer, and modified two layer structure in fully-developed flows, by using the classical inner and logarithmic profiles to determine which portions of the boundary layer are dominated by viscosity, inertia, or turbulence. A new inner function for U+ is developed, based on the three layer description, providing a much more simplified representative form of the streamwise mean velocity nearest the wall.
Ph.D. in Mechanical and Aerospace Engineering, May 2011
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- Title
- MECHANICAL PROPERTIES AND SINTERING MECHANISMS OF POWDER METALLURGY TI6AL4V
- Creator
- Xu, Xiaoyan
- Date
- 2013, 2013-05
- Description
-
Titanium has been identified as one of the key materials with a high strength to weight ratio that can reduce the weight of components and...
Show moreTitanium has been identified as one of the key materials with a high strength to weight ratio that can reduce the weight of components and thereby reduce energy consumption. Single press and sinter as a powder metallurgy technique has the potential to provide cost effective components. Armstrong prealloyed Ti6Al4V, HDH prealloyed Ti6Al4V, HDH blended Ti6Al4V powder and their mixtures were pressed and sintered at different conditions. The chemistry, mechanical and microstructural properties have been investigated to establish optimum processing parameters. Sintered parts were sent to Oshkosh Truck to test and compared with aluminum and steel parts. The Titanium and Ti6Al4V parts were successfully applied and tested. All the specimens passed the load test without failures. The sintering mechanisms of Armstrong prealloyed Ti6Al4V powder were investigated. At relative sintered densities of 75% to 90% (around 900°C), surface diffusion cooperate with grain boundary diffusion, which leads to densification of the powder compact. Around 900°C, grain boundary diffusion controls the sintering process. At 1000°C, boundary diffusion made little contribution to the densification of the Ti6Al4V powder compact. Above 900°C and below 91% sintered density, boundary diffusion controls sintering. Lattice diffusion dominates the densification process at higher temperatures (1100°C~1300°C). The sintering of master alloy blended Ti6Al4V powder has been investigated in order to elucidate the mechanism of sintering. Both blended powder compacts and diffusion couples were investigated using backscattered imaging and energy xvi dispersive analysis to determine the phases present and diffusion path on sintering at 1000ºC and 1100ºC. It is shown that transient liquid phase sintering does not occur and the reason for the rapid sintering of this material is due to enhanced diffusion kinetics resulting from a combination of the concentration gradient and stress induced by a phase transformation in the ternary system.
PH.D in Materials Science and Engineering, May 2013
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- Title
- EUTECTIC γ(NI)/γ′(NI3AL)-δ(NI3NB) POLYCRYSTALLINE NICKEL-BASE SUPERALLOYS: CHEMISTRY, PROCESSING, MICROSTRUCTURE AND PROPERTIES
- Creator
- Xie, Mengtao
- Date
- 2012-12-03, 2012-12
- Description
-
Directionally solidified γ(Ni)/γ′(Ni3Al)-δ(Ni3Nb) eutectic alloys possess attrac- tive high temperature mechanical properties and were...
Show moreDirectionally solidified γ(Ni)/γ′(Ni3Al)-δ(Ni3Nb) eutectic alloys possess attrac- tive high temperature mechanical properties and were considered as candidate tur- bine blade materials. Currently, the properties of polycrystalline γ/γ′-δ alloys are of interest as they inherit many advantageous attributes from the directionally solidi- fied γ/γ′-δ alloys, including high volume fraction of reinforcing phases, exceptional thermal stability and resistance to segregation-induced defect formation. If these at- tributes are properly harnessed, these γ/γ′-δ eutectic alloys might provide a unique solution to the problems experienced by traditional γ/γ′ polycrystalline Ni-base su- peralloys. This thesis is therefore dedicated towards the development of a funda- mental understanding of this novel class of eutectic alloys from several important perspectives. To enrich our understanding of this alloy system, this thesis will first be focused on quantifying the specific effect of individual alloying element on this γ/γ′-δ eutectic system. A set of quaternary Ni-Cr-Al-Nb alloy compositions with increasing levels of Chromium(Cr) was designed to investigate the detailed influence of this element on the primary phase formation, solidus and liquidus temperatures and γ-δ eutectic morphology. The alloying effect of Tantalum(Ta), which shares many similarities to Niobium(Nb), was studied by designing a matrix of multi-component γ/γ′-δ alloy compositions with nominally the same overall (Ta+Nb) content but varying Ta/Nb ratios. Here, different solidification segregation and solid state partitioning behaviors of Ta and Nb in this γ/γ′-δ eutectic system will be discussed, as well as the influ- ence of Ta/Nb ratio on solidification characteristics and equilibrium/non-equilibrium phase volume fractions. Thermodynamic calculations using the Computherm Pandat database (PanNi7) were compared to experimental results in these investigations. The second part of this thesis will aim to provide a more general understand- xvii ing of the effect of various alloying elements, including Cr, Co, Al, Ti, Mo, W, Ta and Nb, on this γ/γ′-δ system. A large number of experimental γ/γ′-δ alloys covering a broad range of compositions was selected for the analysis in this study. Important alloy attributes, such as primary phase formation, overall δ volume fraction, phase transformation temperatures and ternary eutectic initiation, were quantitatively char- acterized as a function of individual alloying element concentrations or combined con- tent of more elements. Linear regression analysis was performed to reveal the relative effectiveness of these elements on this eutectic system. Meanwhile, an extensive com- parison between the experimental observations and Pandat predictions was provided to critically evaluate the strength and weakness of existing thermodynamic database model in predicting trends in this eutectic alloy system with substantially higher Nb content compared to traditional γ/γ′ superalloys. The last part of this thesis emphasizes the development of cast and wrought manufacturing processes for cast γ/γ′-δ eutectic alloys as a cost effective alternative to the powder metallurgy route. Hot rolling of workpieces encapsulated within a steel can was performed on a simple model cast γ/γ′-δ alloy (897) to stimulate the ingot to billet. The influence of different deformation levels on breaking down the dendritic structure and promoting fine and homogenized microstructure was investi- gated. The mechanical soundness associated with different microstructures generated by different hot rolling processes was compared via compression and creep testing. Microstructural parameters that contribute to better mechanical properties will be discussed.
PH.D in Materials Science and Engineering, December 2012
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- Title
- Tests on a four-cycle automobile engine
- Creator
- Barrett, D. O., Morgan, C. W.
- Date
- 2009, 1908
- Publisher
- Armour Institute of Technology
- Description
-
http://www.archive.org/details/testsonfourcycle00barr
Thesis (B.S.)--Armour Institute of Technology; Bibliography: leaves 1-3
- Title
- Study of ideal dry pipe valve
- Creator
- Hepp, A. A., Smith, E. J. L.
- Date
- 2009, 1906
- Publisher
- Armour Institute of Technology
- Description
-
http://www.archive.org/details/studyofidealdryp00hepp
Thesis (B.S.)--Armour Institute of Technology
- Title
- LASER MICROMACHINING, SINTERING, AND LASER-INDUCED PLASMA DEBURRING
- Creator
- Gao, Yibo
- Date
- 2013, 2013-12
- Description
-
Lasers can provide non-mechanical-contact, localized and concentrated energy input to materials with controlled durations and high spatial...
Show moreLasers can provide non-mechanical-contact, localized and concentrated energy input to materials with controlled durations and high spatial resolutions down to a few microns or less. Therefore, lasers have more and more applications in manufacturing and materials processing, such as laser micromachining (which is to create micro-scale features through laser-induced material removal) and laser sintering. Despite the previous research work in the literature, many laser-based manufacturing and materials processing areas still require lots of further research work. Specifically, the following topics will be investigated in the research work in this thesis: nanosecond-pulsed laser ablation of silicon carbide at an infrared wavelength, nanosecond laser-induced plasma deburring, two-step nanosecond laser surface texturing, and the fabrication of carbon nanotube (CNT)-ceramic composites through the laser sintering process.
PH.D in Mechanical and Aerospace Engineering, December 2013
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- Title
- Steam jet ash conveyors
- Creator
- Himelblau, Harry
- Date
- 2009, 1919
- Publisher
- Armour Institute of Technology
- Description
-
http://www.archive.org/details/steamjetashconve00hime
Thesis (B.S.)--Armour Institute of Technology