Instantaneous De-Icing of Freezer Ice via Ultrasonic Actuation

A low-power, nonthermal, ultrasonic de-icing system is introduced as a potential de-icing system for helicopter rotor blades. In this research effort, ultrasonic actuators excite isotropic plates and airfoil-shaped structures that are representative of helicopter leading-edge protection caps. The system generates delaminating ultrasonic transverse shear stresses at the interface of accreted ice, debonding thin ice layers (less than 3 mm thick) as they form on the isotropic host structure. A finite element model of the proposed actuator and the isotropic structures with accreted ice guides the selection of the actuator prototypes. Several actuator-isotropic plate structures are fabricated and tested under freezer ice conditions. Test results demonstrate that radial resonance disk actuators (28-32 kHz) create ultrasonic transverse shear stresses capable of instantaneously delaminating ice layers. The finite element modeling predicts the delamination patterns of the accreted ice layers. Models also predict (within 15%) the required input voltage to promote instantaneous ice debonding. At environment temperatures of -20 degrees C, the system delaminates 2.5-mm-thick ice layers with power input densities as low as 0.07 W/cm(2) (0.5 W/in.(2)).