Martin Zeller
U.S. patent 5,199,305
from NASA's Ames Research Center provides a simple mechanical
means for quantifying strain in coated surfaces under realistic
thermal and mechanical loading conditions. The method and apparatus
described in this patent were originally developed by Ames to
measure strain in infrared optical coatings. A cantilevered beam
is coated on the upper surface and a downward force is applied
to the free end of the beam until the coating fails. The strain
is then determined based on the dimensions of the beam, the point
along the beam where the coating failure occurs and the amount
of deflection of the beam. Advantages of this device include:
-
Ability
to measure coating strain without destroying substrate material,
as occurs with mandrel bend test methods of attached coatings
specified in ASTM D-522
-
Capability
of determining strain in coatings over a wide temperature
range, from -325 to +825 degrees Fahrenheit
-
Quantitative
determination of coating strain is made by simple direct measurement
and calculations that are independent of the substrate material
and any temperature effects of the instrumentation itself
-
Applicability
to both pliable and brittle substrates and independent of
substrate Young's modulus
-
Inexpensive
to fabricate
The device is suited
to any application where mechanical properties of a surface coating
or its bonding strength need to be determined. Some examples include:
- Automotive paints
and coatings
- Special purpose
reflective or emissive coatings
- Conformal coatings
on integrated circuit boards
- Coatings for reducing
friction or preventing sticking
- Sealants
- Mechanical means
for calibrating strain gages
For more info: Martin
Zeller, NASA Far West RTTC, 213-743-2927 or zeller@usc.edu.
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