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Recent Developments in the Use of Liquid Crystal Coatings for Full-Surface Shear Stress Vector MeasurementsUnder normal white-light illumination and oblique observation, liquid crystal coating (LCC) color-change response to shear depends on both shear stress magnitude as well as the direction of the applied shear relative to the observer's line of sight. These color-change responses were quantified by subjecting a LCC to a wall-jet shear flow and measuring scattered-light spectra using a fiber optic probe and spectrophotometer. At any fixed shear stress magnitude, the maximum color change was measured when the shear vector was aligned with and directed away from the observer; changes in the relative in-plane view angle to either side of this vector/observer aligned position resulted in symmetric Gaussian reductions in measured color change. For this vector/observer aligned orientation, color change was found to scale linearly with increasing shear stress magnitude over an eight-fold range. Based on these results, a surface shear stress vector measurement methodology, involving multiple oblique-view observations of the test surface, was formulated. In the present paper, the experimental approach and data analysis procedure required to extend this vector measurement methodology to full-surface applications will be outlined and progress towards demonstrating this areal capability will be reviewed.
Document ID
20020038222
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Reda, D. C.
(NASA Ames Research Center Moffett Field, CA United States)
Wilder, M. C.
(NASA Ames Research Center Moffett Field, CA United States)
Zilliac, G.
(NASA Ames Research Center Moffett Field, CA United States)
Hu, K. C.
(NASA Ames Research Center Moffett Field, CA United States)
Whitney, D. J.
(NASA Ames Research Center Moffett Field, CA United States)
Deardorff, D. G.
(NASA Ames Research Center Moffett Field, CA United States)
Moffat, R. J.
(Stanford Univ. Stanford, CA United States)
Farina, D. J.
(Stanford Univ. Stanford, CA United States)
Danek, C.
(Stanford Univ. Stanford, CA United States)
Martinez, R.
(Stanford Univ. Stanford, CA United States)
Davis, Sanford S.
Date Acquired
August 20, 2013
Publication Date
January 1, 1995
Subject Category
Structural Mechanics
Meeting Information
Meeting: 34th Aerospace Sciences Meeting
Location: Reno, NV
Country: United States
Start Date: January 15, 1996
End Date: January 18, 1996
Sponsors: American Inst. of Aeronautics and Astronautics
Funding Number(s)
PROJECT: RTOP 505-59-54
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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