RESUMEN
The aircraft flight safety and efficiency are largely affected by the aircraft icing, whose characterization is of great significance to guiding the de-icing operation. This study targets a robust and quantitative characterization of icing with ultrasonic guided wave (UGW) of selective frequency-mode pair. Firstly, the frequency domain finite element (FDFE) model is developed to quantitatively analyze the reflection, transmission, and mode conversion of UGW with icing aluminum plate of different lengths and thickness, in order to pick the UGW with appropriate frequency-mode pair sensitive to icing. With the candidate UGW frequency-mode pair, the time domain finite element (TDFE) analysis is further performed to validate the effectiveness of FDFE and to optimize the pulse duration cycle for icing detection. Finally, based on the performed FDFE and TDFE analysis, experimental icing characterization is carried out with the UGW of the selected frequency-mode pair. Results show that the selected UGW at (1239 kHz, mode A1) with ice (0.5 mm thick) has achieved a high detection sensitivity based on the time-of-flight and good robustness against the random error, showing the great potential for the application of UGW to aircraft icing characterization.
RESUMEN
This study proposes an ultrasonic pulse-echo technique to examine the freezing characteristics of a thin film of water over ice, and uses it to develop a method to measure the thickness of glaze ice. A multilayer model is first introduced to simulate ultrasonic transmission through multiple media. A transition layer is then inserted between the layers of ice and water, and its properties were in gradient form along the direction of thickness. Following this, a high-frequency ultrasonic experimental device is developed to dynamically measure variations in the thickness of the layers of ice and water. The accuracy of the proposed model of the transition layer was validated by showing that its numerical results agreed well with those of experiments. The results show that the amplitude of echo from the top of the ice layer was at its minimum when the thickness of the film of water was in the range of [40, 45] µm, and increased when the film of water was thinner than 40⯵m. A delay in echo from the top of the layer of ice was observed when measuring its thickness because the film of water froze, which yielded a relative error of 3.34%. The proposed numerical model can thus efficiently measure the thickness of glaze ice.