Numerical simulation and experimental validation of tailored wave guides for ultrasonic de-icing on aluminum plates

Tailored waveguides (TWG) are introduced to locally concentrate ultrasonic transverse shear stresses at the interface between an Aluminum plate and accreted ice. This concept can effectively maximize delaminating stresses via the introduction of discontinuities on the plate structure. These discontinuities, introduced to the backside of an aluminum panel where ice accretes, allow the shear stresses at the ice/substrate interface to be focused on specific regions, thus locally improving the shear stress concentrations, facilitating low power ultrasonic de-icing. Finite element analysis results demonstrate that the introduction of tailored waveguides can generate more than 300% larger interface stresses compared to those of equivalent mass structures without tailored waveguides (i.e. uniform plates). Furthermore, parametric study indicates that the interfacial shear stresses (ice/aluminum) can be doubled by reducing the spacing between the tailored waveguides. A series of de-icing experiments on Aluminum plates was conducted to validate the numerical simulation. A piezoelectric disk actuator with radial resonance frequency of 28.5 kHz was operated at the ultrasonic vibration modes to successfully delaminate the ice layers on the aluminum panel. Several different waveguide and ice accretion configurations were examined. Experimental trends and power measurements correlated very well (within 15%) with numerical predictions over a wide range of test conditions. Required input power for instantaneous delamination of ice was reduced from 25W to 6 W for an ideal TWG configuration. Ice was successfully delaminated at locations both collocated and dislocated from the TWG geometric nonuniformities.