Browsing by Author "Dr. Ron Scattergood, Committee Member"

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Design of Reflective Optical Systems
(2007-01-22) Wanna, Nadim George; Dr. Thomas Dow, Committee Chair; Dr. Ron Scattergood, Committee Member; Dr. Jeffrey Eischen, Committee Member
The primary objective of this research is to develop optical and opto-mechanical design procedures for reflective optical systems. Challenges in fabrication and testing have limited the choice of surfaces used in the design of reflective optical systems to rotationally symmetric surfaces. Freeform surfaces or non-rotationally symmetric surfaces are necessary to meet challenging performance and packaging requirements. To gain familiarity with optical and opto-mechanical design techniques, two systems were considered: a two mirror Ritchey-Chrétien telescope and a Three Mirror Anastigmat. The two mirror Ritchey-Chrétien optical system using rotationally symmetric hyperbolic surfaces is designed. The opto-mechanical design incorporates the use of radial and axial fiducial surfaces to locate the two mirrors onto a tube relating the optical surfaces to each other and to the detector through a spacer plate. Optical performance improvement over the two mirror telescope is achieved with the addition of a third mirror. The Three Mirror Anastigmat (TMA) optical design uses off-axis conic sections of a rotationally symmetric system. Further improvement to the optical performance is achieved with a freeform TMA optical system and optical surface fabrication feedback to the designer. Opto-mechanical design of the TMA incorporates the use of a telescope frame to constrain each mirror in six degrees of freedom and relate the optical surfaces to each other and to the detector. The mirrors are held in place through independent mounting clamps to sustain high gravitational acceleration with minimum optical surface distortion. The two mirror telescope optical performance is limited by optical aberrations especially at high field angles. Locating the mirrors on a tube over-constrains the components and distorts the optical surfaces. Multiple assembly configurations or non-repeatability is due to symmetry of mounting screws. Impressive optical performance, 58 times wavefront error improvement over the two mirror system, is achieved with an unobstructed TMA optical system using freeform surfaces. A snap-together repeatable assembly without adjustments is designed using conventional fiducial techniques and independent mounting clamps minimizing optical surface distortion.
Mechanical Characterization and Morphology Study of a Novel Class of Carbon Nanotube Textiles and Composites
(2007-07-23) Bradford, Philip David; Dr. Sam Hudson, Committee Co-Chair; Dr. Russell Gorga, Committee Co-Chair; Dr. Ron Scattergood, Committee Member
Carbon nanotube yarns are an emerging class of carbon nanotube materials that show great promise in composite applications. This research study was conducted to gain insight into the morphological structure of the yarns and to correlate their structure to the mechanical properties of both dry yarns and composites. Complex 3-D braided nanotube yarn structures were provided to determine the mechanical properties of macroscopic samples and to determine the effect of processing on the yarns. To accomplish these goals, baseline samples of carbon fiber were tested, a microscopical study was conducted, the cross sectional area of the samples were properly determined, composites were fabricated, and samples of the dry nanotube yarn structures as well as their composites were tested in tension. The results of this study showed that in composite structures with low viscosity resin, the nanotube yarns did not act as the constituent reinforcement. Due to resin penetration through the yarns structures, the individual nanotubes that make up the yarns acted as the constituent reinforcement. In addition, the testing of the 3-D braided yarn structures showed that this process did not significantly weaken the structure and could be useful in making macroscopic preforms of carbon nanotube yarns.
Metrology of Reflective Optical Systems
(2007-01-03) Woodside, Robert M Jr; Dr. Thomas Dow, Committee Chair; Dr. Greg Buckner, Committee Member; Dr. Ron Scattergood, Committee Member
A functioning reflective optical system requires designing, fabricating, and assembling complicated optical surfaces. However, once these surfaces have been fabricated, an accurate metrology process must be available to ensure the fabricated optical and fiducial surfaces conform to the designed surfaces. The goal of this research is to apply metrology techniques to reflective optical systems and their components. A two mirror Ritchey-Chretién telescope was designed and fabricated as a vehicle to test these metrology techniques. This system involves two rotationally symmetric conic mirrors. A conic mirror is much more difficult to measure than a simple flat or spherical mirror because of the added variable of a second focusing location. Measuring the Ritchey-Chretién telescope components is intended to provide a knowledge base to build metrology techniques for more complicated systems such as a three mirror anastigmatic optical system. Techniques must be available to measure the individual optical surfaces, the fiducial surfaces used for assembly and the complete system. The available techniques to measure an optical system include interferometry, profilometry, optical targets and coordinate measuring machines. The Zygo GPI Fizeau interferometer was used in a dual-pass setup to measure optical surface form error and the assembled optical system performance. The GPI can produce three dimensional form error maps and also measures wavefront error and modulation transfer function (MTF). The Zygo NewView White Light Interferometer was used to measure the surface finish of an optical surface. Profilometry with the Taylor-Hobson Talysurf Profilometer and a unique rotational profilometer were used to measure the form error of the optical surface as well as the fiducial surface errors. Profilmoetry was also applied to the primary optical surface to verify measurements made on the GPI and as an alternative to measure the secondary mirror. Measuring the flatness of the fiducial surfaces required profilometry because the fiducial surface diameters are larger than the aperture of the GPI. Optical targets were used to measure the MTF of the assembled optical system and to measure the image producing ability of the system. Coordinate measuring machines were necessary to measure the height of the fiducial surfaces used for assembly. This measurement is necessary to determine the location of the mirror apexes upon assembly. The metrology techniques were shown to be robust for any rotationally symmetric optical system while simultaneously uncovering the advantages and shortcomings inherent in the individual metrology techniques. The process also uncovered flaws in the component and system design that reduced the available metrology options. The optical component measurement showed that the optical mirrors possessed a surface finish that is expected for the material and fabrication process. The secondary mirror showed form error as expected near λ/4 while the primary mirror had a large form error of over 3λ. The system measurement showed 1.5 μm of wavefront error at its best focus point. The wavefront aberrations present in the system caused spot sizes double the magnitude predicted by Code V and MTF values that are approximately 10-20% of the theoretical values.
Wire Electro-Discharge Machining of Advanced Engineering Materials
(2003-04-09) Miller, Scott Franklin; Dr. Ron Scattergood, Committee Member; Dr. Albert Shih, Committee Chair; Dr. John Strenkowski, Committee Member
The goal of this research was to create models and guidelines for Wire Electrical Discharge Machining (WEDM) of new advanced engineering materials and for truing of metal bond diamond grinding wheels. The development of new advanced engineering materials and the need to meet demand for precise and flexible prototype and low-volume production of components has made WEDM an important manufacturing process. One goal of this research is to investigate the effect of spark on-time duration and spark on-time ratio, two critical WEDM process parameters, on truing of metal bond diamond grinding wheels and machining of three types of new advanced engineering materials; porous metal foams, sintered Nd-Fe-B magnets, and carbon-carbon composite fuel cell bipolar plates. An envelope of feasible process parameters for material removal rate is developed for each material, according to machine, tooling, and physical limitations. This envelope is then applied to cut sections of carbon-carbon bipolar plate and sintered Nd-Fe-B magnet to minimum thickness. Effect of process parameters on limit of thickness of the sintered Nd-Fe-B magnet is discussed. The surfaces machined by WEDM were qualitatively studied using Scanning Electron Microscopy to observe surface features and characteristics. Experiments were conducted to measure temperatures generated during the EDM process using infrared spectrometry on three different materials; 1. metal bond diamond grinding wheel, 2. WC-Co, and 3. copper.