Design, fabrication, calibration, and testing of a centrifugal ice adhesion test rig with strain rate control capability

To develop technologies for mitigating ice accretion on aircraft, a test rig to quantify the shear adhesion strength of impact ice is sought. One of the most effective methods of measuring ice adhesion strength without manually handling any accreted ice is through instrumented centrifuge adhesion tests (ICAT). One of the drawbacks of most ICAT rigs is the inability to perform controllable strain rate variations on the accreted ice. A new test rig has been designed, built, and calibrated for installation in the NASA Icing Research Tunnel. The unit can also be installed in a walk-in freezer using an icing nozzle to generate impact icing clouds. The unit can perform all the same functions as modern ICAT stands, with the added capability of varying the motor acceleration to introduce controllable strain rates on accreted ice. This allows strain rate to be isolated and investigated as a parameter that affects ice adhesion strength. The design of the new test rig is documented, and preliminary adhesion and liquid water content (LWC) test results are presented. The LWC of the impact icing cloud in the freezer configuration was found to be approximately 1.1. Preliminary impact ice adhesion tests suggest that higher impact velocity and higher surface roughness cause higher ice adhesion strength on isotropic metals. Adhesion strength values range between 6.5 psi to 9.5 psi for the roughest samples, with a standard deviation of approximately 1.5 psi. For the same samples, freezer ice yielded a much higher adhesion strength of 35 psi. A procedure for future testing of strain rate effects on ice adhesion strength is also outlined.