ELECTRICAL AND COMPUTER ENGINEERING SEMINAR SERIES
Dr. Steven Shepard
Thermal Wave Imaging, Inc.
Thursday, March 21, 2019
3:00 p.m. - 4:00 p.m.
“Advances in Active Thermography for Nondestructive Testing”
Thermography has traditionally been used as a qualitative Nondestructive Test (NDT) method for finding subsurface flaws based on identification of localized anomalous cooling response in an infrared image sequence. However, NDT performance is significantly enhanced by treating the acquired thermographic data as a set of independent time histories, rather than a collection of images. In the Thermographic Signal Reconstruction (TSR) method, a noise-free replica of each time history is created, and its logarithmic derivatives are analyzed to identify deviations from 1-dimensional cooling behavior. Using the TSR approach, a single pixel time history can indicate the presence and spatial extent of an interface, and its thermophysical properties relative to the layer closest to the surface. The individual pixel time histories can be combined to create a map of thickness, thermal diffusivity or porosity. The derivative results are significantly more sensitive to material properties characteristics, and immune to extrinsic artifacts, than direct viewing of the infrared image. TSR is widely used in the aerospace and power generation industries for both flaw detection and material characterization applications. Fundamentals of thermography and examples of enhanced detection using TSR will be presented.
After receiving his Ph.D. in Physics from Wayne State University in 1987, Dr. Shepard joined the US Army Tank-Automotive Command (TACOM), where he received the 1991 Army R&D Achievement Award for his work in synchronous high-speed IR imaging. He founded Thermal Wave Imaging, Inc. (TWI) 1993, where he now serves as President and continues to play a leading role in the development and implementation of NDE technology based on thermography. Dr. Shepard is the inventor of the widely used Thermographic Signal Reconstruction (TSR) and has been awarded over 20 domestic and international patents. He is the recipient of the ASNT 2014 Research Innovation Award and the 2016 ASNT Mehl—Lester Honor Award, and is the author of over 100 technical papers, including NDT handbook chapters for ASNT, ASM and Elsevier.
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