# Effect of Ultrasonic Vibration on the Surface Adhesive Characteristic of Iced Aluminum Alloy Plate
## 2 Simulation of the Location of Vibration Source  
For the large-scale wind turbine, the blade surface can be simplified into two kinds of shapes--the curved surface and the plane surface, which are shown in Figure 2. For the blade body, the curvature of it is small. In the scope of a small area, we simplified the surface into a piece of the plane. In contrast, the leading edge of the blade has large curvature. It can be simplified into a volume surface in the scope of a small area. By this simplification method, the research process can be simplified, and fundamental research on the adhesive characteristics of icing on the plate and volume can also be carried out. In the present study, a plate element, not from the exact position of a real blade body, was selected as a research object characterizing part of the blade body, to carry out studies on the ultrasonic vibration deicing technology. The formation of ice is a phase change of water from liquid to solid as the temperature falls below zero degrees Celsius. After phase change, the ice is frozen together with the substrate material. Therefore, the iced body is similar to a composite material. In general, there are three basic categories of deicing systems, which are the mechanical deicing system, the thermal deicing system, and the chemical deicing system. For the mechanical deicing system, the principle of the deicing system is to break the adhesive bond [22]. Many years ago, researchers found that the adhesion strength of ice is lower in shear than in tension [23]. Similarly, in a previous study, it was also validated that the key factor of breaking the adhesive bond is shear stress [24]. Therefore, researchers selected shear stress as the deicing parameter for the mechanical deicing system. In this paper, the ultrasonic deicing method used is a mechanical deicing system. Its principle is shown in Figure 3a. As shown in Figure 3a, when the PZT patch (piezoelectric ceramic) is excited by alternative voltage, it alternatively extends and contracts in ultrasonic frequency, which excites the iced aluminum alloy plate to vibrate and deform. Then, the mechanical shear stress generates due to bending deformation at the adhesive interface. When mechanical shear stress is higher than the adhesive shear stress of ice, the ice can be removed. Figure 2: Simplification model of the wind turbine blade. In this paper, an aluminum alloy was selected as the substrate material, because metals have the characteristics of isotropies in elasticity and heat transfer. Aluminum alloys have lower elastic moduli lower than other materials. They easily deform under the excitation of ultrasonic vibration, which is suited to conduct the basic research on ultrasonic deicing. In addition, many scholars have carried out studies on the adhesive characteristic of ice on aluminum alloy surfaces. The adhesive shear stress of ice covering on the aluminum alloy surface can be referenced and compared. In the present study, an aluminum alloy plate with the size of 60 mm \(\times\) 60 mm \(\times\) 2 mm was initially selected as a plate element, and the thickness of the ice is 2 mm. The model of the iced aluminum alloy plate is shown in Figure 3b. According to the principle of the ultrasonic deicing method, while an iced aluminum alloy substrate deforms under the excitation of ultrasonic vibration, shear stress generates at the adhesive interface between the ice and the aluminum alloy plate. When the shear stress is higher than the adhesive shear stress of ice, which is the adhesive shear force in the unit area, the ice layer can be removed from the substrate plate. Therefore, in the present study, the bend deformation of the iced aluminum alloy plate was selected, which leads to higher shear stress at the adhesive interface between the ice and the aluminum alloy plate. To determine the location of the piezoelectric ceramic (PZT-4), which is the ultrasonic vibration source, the first-order bending vibration mode of the iced aluminum alloy plate was calculated by ANSYS software.