The Implementation And Analysis Of Wide Dynamic Range Imaging Methods

This dissertation presents the implementation and analysis of wide dynamic range (WDR) imaging methods. It covers the study of wide dynamic range imaging, its applications and techniques

INVESTIGATION INTO THE EFFECTS OF SUPERCRITICAL CARBON DIOXIDE EXPOSURE ON WELL-BORE CEMENT INTEGRITY

Current subterranean injection of anthropogenic Carbon Dioxide (CO2), or CO2 resulting from human activity, is occurring at multiple locations in both the domestic United States and abroad. It involves the capture of CO2 from stationary industrial sources such as power plants and processing facilities, and subsequent injection into suitable subsurface environments. Injection is an alternative to the release of CO2 and reduces the environmental impact of increased atmospheric carbon levels. The three scenarios for CO2 injection are: the sequestration of captured anthropogenic CO2, the re-injection of produced CO2, and the use of CO2 for tertiary hydrocarbon recovery. If injected at conditions allowing for supercritical behavior, CO2 can interact with the near wellbore environment. The result of that interaction is of interest to the longevity of injection operations. Produced oil and gas are accompanied by some level of CO2 production. This CO2 is often separated and is sometimes re-injected near its source, reducing the percentage of CO2 in the transported product. In contrast, tertiary hydrocarbon recovery introduces injected CO2 for a distinctly different reason. Tertiary injection, also called Enhanced Oil Recovery (EOR), utilizes injected CO2 to recover entrained oil. Tertiary CO2 injection has been historically successful in the Permian Basin of West Texas and New Mexico and is currently being utilized in many other mature fields in the western US. Whether injection occurs for sequestration, disposal, or production, captured CO2 is transported down existing wellbores into in-situ reservoir environments where it may theoretically stay for perpetuity. In light of the increasing injection of CO2, recent reservoir completion methods often involve the use of CO2 resistant cements. These cements contain fluid loss additives, dispersants, and fly ash to improve strength and reduce permeability. The effect of CO2 on these resistant forms of cements is still being empirically studied. However, many injection environments utilize older wellbores in mature fields. The ability of these older cement sheaths to structurally contain and segregate the wellbore and rock structure during and after the exposure to CO2 is uncertain. To what extent CO2 injection destabilizes these environments impacts global injection projects and the practicality of CO2 injection in general. These potential issues are elevated when it is considered that because of geothermal temperatures and injection pressures, CO2 will be supercritical in nature, where distinct liquid and gas phases do not exist. Supercritical CO2 possesses the dissolving properties of a strong solvent, the ability to transport mass like a liquid, and the ability to permeate small pores and fissures with the diffusivity of a gas. It is possible that when exposed to the destructive properties of supercritical CO2, cement may be chemically altered. Resulting increases in permeability and porosity may lead to breaches in the wellbore’s ability to control the injected CO2 and the surrounding reservoir fluids. Alternately, it is possible that the chemical changes in the cement induced by supercritical CO2 will strengthen the wellbore and increase the containment longevity. This research investigates the effects of supercritical CO2 on laboratory prepared cement core samples by replicating an elevated pressure and temperature flow environment like that of CO2 injection efforts. The resulting permeability, porosity, and strength changes were recorded and analyzed allowing for conclusions regarding the resilience of well-bore cements in the presence of CO2 injection. Despite lower quantities of successfully exposed samples, results indicate that the presence of supercritical CO2 in a dynamic reservoir environment caused an anecdotal change in porosity and permeability. During subsequent unconfined strength analysis, the experimental values of maximum strength of unexposed experimental controls were found to be greater than almost all exposed cores. Exposed cores were separately examined for statistical significance under the experimental criteria of Young’s Modulus, max stress, and Yield Point. Utilizing a two sample unpaired t-test analysis performed with a significance level of α = 0.095, it can be shown that the experimentally observed decreases in the unconfined stress criteria likely correlate to the presence of super critical CO2 under dynamic reservoir conditions

Application of 3D laser scanner, optical transducers and digital image processing techniques in physical modelling of mining-related strata movement

A physical testing protocol for modelling mining-related problems has been presented. • A new method for monitoring fracture propagation pattern has been introduced. • Laser based and optical devices have been used for physical modelling of subsidence. • Multiple-seam subsidence has been measured by photogrammetry, DIC analysis, optoNCDT and 3D TLS

Effect Of Impact Damage On Compression-Compression Fatigue Behavior Of Sandwich Composites

The aim of this research work was to investigate the effect of impact damage on in-plane buckling and compression-compression fatigue behavior for a new sandwich structure made from E-glass/epoxy face sheets over end-grain balsa wood core. Low velocity impact tests were carried out using a drop-weight impact tower by impacting the sandwich beam at the center with energy level slightly higher than threshold energy level of 8.8 J. Edge-wise compression static tests were conducted for impacted and non-impacted samples to address energy absorption characteristics of these composites. Analytical and experimental investigations were carried out to measure critical buckling loads and study the response and failure modes of debonded composite sandwich beams under compressive loads. These composite sandwich beams with local delamination caused by low velocity impact were utilized to evaluate the compression fatigue performance. Compression-Compression fatigue tests were conducted for specimens with and without impact damage. Compressive residual strengths were obtained and the growth of delamination was monitored during fatigue tests. Although fatigue performance was adversely affected due to the presence of impact induced damage, it was observed that delamination growth does not occur in fatigue for in-plane stress levels below 40% of compression-after-impact (CAI) values for this class of sandwich composites. Results showed that there was significant degradation of fatigue life due to impact damage in relation to undamaged composite. Also, it was observed that any appreciable stiffness loss in fatigue does not occur below 50% CAI value. The combined damage consisting of delamination, core shear and skin failure was found to be the dominant failure mode under compression fatigue. The finite element analysis (ABAQUS) was utilized to predict the interfacial stress and stress distribution along thickness of the undamaged composite beam. The normal compressive stress distribution along thickness was plotted. The results showed very good agreement for facing and core stress values obtained by the analytical and numerical solutions. The predicted interfacial stress value was found to be between the facing and core stresses. These micromechanics results provide a clear understanding of the local behavior and how they influence the overall composite behavior. A unique contribution of the thesis work is compressive fatigue response characteristics of glass fiber sandwich composites subjected to lateral impact. These results are likely to be integrated into design of lightweight decks in automotive and truck applications

Development and optimisation of two-line planar laser induced fluorescence technique for combustion measurements

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This study has focused on development, optimisation and implementation of the 2-line Planar Laser Induced Fluorescence (2-line PLIF) technique for combustion measurements on a single cylinder optical Gasoline Direct Injection (GDI) engine with both Spark Ignition (SI) and Controlled Auto Ignition (CAI) combustion operations. The CAI combustion was achieved by employing Negative Valve Overlap (NVO). Two excitation wavelengths at 308 nm (directly from a XeCl laser) and 277 nm (via Raman shifting a KrF laser output at 248 nm) were exploited for the measurements. A calibration curve of fluorescence signal intensity ratio of the two laser beams as a function of temperature was obtained by conducting a series of static tests on a specially designed Constant Volume Chamber (CVC). The developed technique was validated by measurements of in-cylinder charge temperature during the compression stroke for both motoring and firing cycles and comparing the PLIF values with the temperature values calculated from in-cylinder pressure data assuming a polytropic compression. Following the validation measurements, the technique was applied to study of fuel spray characteristics and simultaneous measurements of in-cylinder charge temperature and mole fraction of Exhaust Gas Residuals (EGR). Further optimisation of the thermometry technique by enhancing the fluorescence Signal to Noise Ratio (SNR) and improving both the temporal and spatial resolutions as well as measurements precision provided the opportunity to apply the technique to other combustion measurements. The thesis presents the first application of the 2-line PLIF diagnostic in study of direct injection charge cooling effects and study of flame thermal stratification in IC engines

In-situ Grain Scale Strain Measurements using Digital Image Correlation

Materials used in engineering structures fatigue and ultimately fail due to the various applied loads they are subject to, a process which compromises structural performance and potentially poses threats to society. Commonly employed theoretical models capable of describing and predicting deformation and failure are typically validated by relevant experimental results obtained from laboratory testing. However, such models are also often based on simplifying assumptions including for example homogeneous composition and isotropic behavior, since available experimental information relates primarily to bulk behavior.Metals are crystalline in nature and their failure depends on several parameters that span a wide range of time and length scales. Therefore, significant efforts have been made over the past decades to investigate the mechanical behavior of polycrystalline metals by formulating important microstructure-properties relations. In this context, this thesis presents a framework to obtain reliable, non-destructive, non-contact, full field measurements of deformation and strain at the grain-scale of polycrystalline materials to assist the understanding of materials phenomena and contribute in the development of realistic mechanics models. To this aim, the method of Digital Image Correlation is used, adapted and expanded.Digital Image Correlation relies on images of the surface of tested specimens, components or structures and the identification of surface contrast patterns which are tracked as a function of deformation and are subsequently used to define displacements and strains. To quantify stains at the grain-scale, three different approaches based on Digital Image Correlation are described. The first involves the use of a commercial system adapted to make grain-scale measurements at the meso-scale (~4mm). A magnesium AZ31alloy was observed for this purpose and full field strain maps are reported. The second employs the same commercial system augmented with a long distance optical microscope to in-situ quantify strains at the tip of a propagating crack in a Compact Tension specimen of an Al2024 aluminum alloy subjected to Mode I loading and using a field of view of ~870 x 730 μm. Finally, the third approach uses an image series acquired from loading a stainless steel sample inside a scanning electron microscope equipped with a micro-tensile stage. Such information was post processed ex-situ and strains were obtained. The advantages and limitations of the proposed approaches are critically evaluated and future work is described to further enhance the reliability and repeatability of grain scale strain measurements using Digital Image Correlation.M.S., Mechanical Engineering -- Drexel University, 201

Characterization of Stresses and Strains Involved in the Martensitic Phase Transformations

Transformation-induced plasticity (TRIP) steels are an example of steels used in the automotive industry, where strain-induced martensitic transformations, associated plasticity and work hardening, enhance both the strength and ductility of the material. This has enhanced both the passenger safety (improved crash-performance) and fuel efficiency as less material is consumed (lighter structure). To gain insights into these strain-induced transformations, it is crucial to understand the impact the applied stress/strain on the martensitic transformation and how the resulting strain fields affect the further deformation and transformations. This PhD dissertation reports a series of experimental measurements on how the applied deformation affects strain-induced transformations, using three techniques, namely: electron backscatter diffraction (EBSD), high-resolution digital image correlation (HRDIC) and in situ neutron diffraction. It is shown here that applied stress favours the formation of strain-induced martensite in certain orientations of austenite. Crystallographic information gathered by EBSD and HRDIC indicates that the formation of martensite is governed by prior slip in the parent austenite. HRDIC measurements showed that strain heterogeneity is found not only between different grains within the microstructure, but even within individual austenite grains, suggesting that input parameters of macro stress strain properties are inadequate for variant selection models. EBSD, HRDIC and neutron diffraction measurements at ambient temperature confirm that the transformation is preceded by plastic deformation of the austenite crystal lattice and subsequent formation of nucleation sites. Here, it was shown that the intensity of those diffraction peaks from austenite grain families most affected by plastic deformation, decreased most due to martensitic transformation. Whereas, at the lower temperature deformation regimes, slip is suppressed, this is not the case. This dissertation illustrates how the above-mentioned techniques may be used to probe material phenomenon at various length scales, stress states and temperature regimes of interest

Smart optical imaging systems with automated electronics

In this dissertation, proposed and demonstrated are several novel smart electronically automated optical designs to efficiently solve existing real-world problems in the field of shape sensing and imaging. First half of the thesis proposes shape sensing techniques that use an Electronically Controlled Variable Focus Lens (ECVFL) within a smart optical design suitable for a wide range of applications including shape sensing and projection displays. The second part of this dissertation involves the use of the Digital Micromirror Device (DMD) deployed within several smart optical designs including an embedded laser beam profiler and a new camera idea which is inspired by the Telecommunication science field. Specifically, proposed and demonstrated is the design and implementation of the novel imaging device called Coded Access Optical Sensor (CAOS) where CAOS is able of operating with different application dependent working modes. Experimentally and successfully demonstrated for the first time are its use for coherent light laser imaging as well as for incoherent imaging of a high dynamic range white light scenario. It is also shown how its design can be further extended for multispectral and hyperspectral imaging applications

Air Force Institute of Technology Research Report 2012

This report summarizes the research activities of the Air Force Institute of Technology’s Graduate School of Engineering and Management. It describes research interests and faculty expertise; lists student theses/dissertations; identifies research sponsors and contributions; and outlines the procedures for contacting the school. Included in the report are: faculty publications, conference presentations, consultations, and funded research projects. Research was conducted in the areas of Aeronautical and Astronautical Engineering, Electrical Engineering and Electro-Optics, Computer Engineering and Computer Science, Systems and Engineering Management, Operational Sciences, Mathematics, Statistics and Engineering Physics

Aeronautical engineering: A continuing bibliography with indexes (supplement 295)

This bibliography lists 581 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System in Sep. 1993. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics