Extension of Moire interferometry into the ultra-high sensitivity domain

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dc.contributor.authorHan, Bongtaeen
dc.contributor.committeechairPost, Daviden
dc.contributor.committeememberSmith, Charles W.en
dc.contributor.committeememberDowling, Norman E.en
dc.contributor.committeememberDillard, David A.en
dc.contributor.committeememberKohler, Werner E.en
dc.contributor.departmentEngineering Mechanicsen
dc.date.accessioned2014-03-14T21:10:52Zen
dc.date.adate2006-05-11en
dc.date.available2014-03-14T21:10:52Zen
dc.date.issued1991-03-05en
dc.date.rdate2006-05-11en
dc.date.sdate2006-05-11en
dc.description.abstractThe objective of this research was to provide means for the experimental analysis of deformations encountered in micromechanics. Whole field contour maps of U and V displacements in a microscopic field of view were desired. Since displacements within a small field can be very small even when strains are large, ultra-high sensitivity is required. The specific objective was displacement sensitivity of 50 nm per fringe contour, which corresponds to that of moire with 20,000 lines per mm, in combination with spatial resolution of the optical microscope (2-5 μm). The objective was achieved by the following developments. First, the basic sensitivity of moire interferometry was increased beyond the previously conceived theoretical limit. This was accomplished by creating the virtual reference grating inside a refractive medium instead of air, thus shortening the wavelength of light. A very compact four beam moire interferometer in a refractive medium was developed for microscopic viewing, which produced a basic sensitivity of 208 nm per fringe order. Its configuration made it inherently stable and relatively insensitive to environmental disturbances. An optical microscope was employed as the image recording system to obtain the desired spatial resolution. Secondly, a fringe multiplication scheme was implemented. Here, an automatic fringe shifting and fringe sharpening scheme was developed, wherein very thin fringe contours of order N* = βN were produced, where N is the fringe order in the basic moire pattern and β is a fringe multiplication factor. A factor of 12 was achieved, providing a sensitivity of 17 nm per fringe contour. This corresponds to moire with 57,600 lines per mm (1,463,000 lines per in.), which exceeds the sensitivity objective. The mechanical and electronic systems implemented here are remarkably robust and quick. The method was demonstrated with three practical applications: interface strains in a thick 0°/90° graphite/epoxy composite, fiber/matrix deformations of metal/matrix composites, and thermal deformation around a solder joint in a microelectronic subassembly.en
dc.description.degreePh. D.en
dc.format.extentxi, 99 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-05112006-154755en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-05112006-154755/en
dc.identifier.urihttp://hdl.handle.net/10919/37748en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V856_1991.H359.pdfen
dc.relation.isformatofOCLC# 24073334en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V856 1991.H359en
dc.subject.lcshMicromechanics -- Researchen
dc.subject.lcshMoiré method -- Researchen
dc.titleExtension of Moire interferometry into the ultra-high sensitivity domainen
dc.typeDissertationen
dc.type.dcmitypeTexten
thesis.degree.disciplineEngineering Mechanicsen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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