Moiré interferometry at high temperatures

The objective of this study was to provide an optical technique allowing full-field in-plane deformation measurements at high temperature by using high-sensitivity moiré interferometry. This was achieved by a new approach of performing deformation measurements at high temperatures in a vacuum oven using an achromatic interferometer. The moiré system setup was designed with particular consideration for the stability, compactness, flexibility, and ease of control. A vacuum testing environment was provided to minimize the instability of the patterns by protecting the optical instruments from the thermal convection currents. Also, a preparation procedure for the high-temperature specimen grating was developed with the use of the plasma-etched technique. Gold was used as a metallic layer in this procedure. This method was demonstrated on a ceramic block, metal/matrix composite, and quartz. Thermal deformation of a quartz specimen was successfully measured in vacuum at 980 degrees Celsius, with the sensitivity of 417 nm per fringe. The stable and well-defined interference patterns confirmed the feasibility of the developments, including the high-temperature moiré system and high-temperature specimen grating. The moiré system was demonstrated to be vibration-insensitive. Also, the contrast of interference fringes at high temperature was enhanced by means of a spatial filter and a narrow band interference filter to minimize the background noise from the glow of the specimen and heater. The system was verified by a free thermal expansion test of an aluminum block. Good agreement demonstrated the validity of the optical design. The measurements of thermal deformation mismatch were performed on a graphite/epoxy composite, a metal/matrix composite equipped with an optical fiber, and a cutting tool bit. A high-resolution data-reduction technique was used to measure the Strain distribution of the cutting tool bit.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Engineering Mechanics

Department dc:contributor.department

Engineering Mechanics

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1992

Author dc:creator

• Wu, Jau-Je

Chair dc:contributor.committeechair

• Czarnek, Robert

Committee members dc:contributor.committeemember

• Smith, Charles W.
• Morton, John
• Plaut, Raymond H.
• Claus, Richard O.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

etd-05042006-164510

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/37687