Development of a New Ice Crystal Icing Shear Adhesion Rotary Test Rig and Method

This paper discusses the development and implementation of a new ice crystal icing (ICI) ice adhesion test system and technique. It is based on the state of the art rotary shear adhesion test rig developed at the NRC altitude icing wind tunnel (AIWT) used for supercooled liquid water (SLW) ice accretion adhesion testing. This rig was modified to use strain gauged arms for shed force measurements and implemented into the NRC ICI cascade rig at its research altitude test facility (RATFac). This permitted the exposure to a wide range of ICI conditions both in supercooled and wetbulb below freezing ICI conditions. The result is a standalone system that can be run remotely thus improving the testing efficiency by avoiding the need for accretion calibration points previously required to correlate accreted mass to icing exposure time. This technique was shown to be very repeatable with adhesion results for repeat points generally being within ±4 kPa and being highly sensitive in being able to measure shear adhesion strengths in the range of 8 to 200 kPa, with adhesion strengths down to 2 kPa measured but with increased noise levels. ICI accretion adhesion shear strengths are lower than typical SLW adhesion strengths and this new method proved to be effective in covering the full range.