Keywords and Phrases
Digital Micromirror Device (DMD); Heat Transfer; Non Destructive Testing (NDT)
"Thermography is a Non-Destructive Testing (NDT) method that has found increasing use in industry and research. It has the advantages of being non-contact and be able to interrogate a large surface simultaneously. Active thermography using flash lamps as heat source has been demonstrated for identifying blind holes and delamination in composites. Despite these advancements, active thermographic approach fails to defects like cracks. Under uniform illumination heat flow is predominantly 1D and can easily circumvent a narrow feature. This can be overcome by using a focused light/laser source onto the surface to impose a 3D heat flux. The disadvantage is that thermography is now a point-by-point proposition, because the focused heat source interrogates only a localized region. This work investigates the use of a Digital Micro mirror Device (DMD) to modulate the illumination both spatially and temporally. This allows multiple point or line sources to simultaneously illuminate a surface at independent frequencies. The use of frequency modulation maps the results to phase space, which permits data to be extracted even when the thermal camera is not precisely calibrated, in combination with the low cost of the DMDs. This thesis describes the construction of the experiment, the theory behind the technique, demonstrates the setup for conventional thermographic methods (pulse/flash and lock-in) before demonstrating the ability to demodulate a locally varying heat flux. The thesis also presents the use of the setup for rudimentary system identification which is similar to Photo Thermal Radiometry, and extends the use of the setup to distinguish films from the underlying substrate, in addition to crack detection. Numeric simulations in ANSYS used to guide this work are also presented along with suggestions for future improvement of the setup and scale-up to larger systems."--Abstract, page iii.
Kinzel, Edward C.
Mechanical and Aerospace Engineering
M.S. in Mechanical Engineering
Missouri University of Science and Technology
xi, 60 pages
© 2015 Arvindvivek Ravichandran, All rights reserved.
Thesis - Open Access
Library of Congress Subject Headings
Heat -- Transmission -- Mathematical models
ANSYS (Computer system)
Electronic OCLC #
Link to Catalog Record
Ravichandran, Arvindvivek, "Spatial and temporal modulation of heat source using light modulator for advanced thermography" (2015). Masters Theses. 7411.