## 2 Materials and Methods
### Experimental Validation of Integral Squeeze Film Bearing Damper Treatment  
Vibration control of an unbalanced single-side cantilevered rotor system is achieved by mounting ISFBDs at the bearing housings. The structural parameters of the integral squeeze film bearing damper will significantly affect the vibration control effect of the unbalanced single-side cantilevered rotor system. In order to verify the damping performance of the damper, a vibration control platform was established as shown in Figure 9.  
Figure 8: ISFBD stress contour.  
Figure 7: Displacement contour: (**a**) Shaft displacement contour; (**b**) ISFBD displacement contour.  
The platform is mainly composed of an unbalanced single-side cantilevered rotor system and a vibration monitoring part. The vibration monitoring part of the hardware mainly includes:  
1. Sensor: The sensors used in this paper include photoelectric and eddy current sensors. The photoelectric sensor is used for speed measurement, and its measurement range is from 0.3 Hz to 10 kHz, output current is less than 30 mA, the resolution film number is greater than 0.5, the application distance is 1-2000 mm, and the rotational speed measurement is stable. The eddy current sensor is used to measure the vibration displacement of the shaft. The measuring range is up to 2 mm, the sensitivity is high (it has a sensitivity of 8 mV/\(\upmu\)m, a resolution of 1 \(\upmu\)m, and a linearity of 1.5%), and the measurement is accurate.
2. Proximitor: The proximity is an electronic signal processor. The internal coil of the eddy current sensor provides high-frequency alternating current. And changes of the sensor parameter due to changes of displacement can be detected.
3. Signal acquisition system: The signal acquisition system consists of a signal collector and a computer. The system is used to measure and analyze the received vibration signals. The signal collector has eight channels and can change the sampling frequency and sampling points as needed. It has many analysis modules, such as time domain and frequency domain spectra.  
In this experiment, the photoelectric sensor was used for speed acquisition, and the eddy current sensor was used to monitor the displacement vibration of the shaft near the unbalanced single-side cantilevered disk. We set the number of sampling points to 512 and the sampling frequency to 1 KHz in the software. Channels 1 and 2 were used for selecting and receiving signals. The time domain and the frequency domain spectrum are analyzed to explore the vibration control of the integral squeeze film bearing damper.  
As shown in Figure 10, the integral squeeze film bearing damper was mounted between the bearing outer ring and the bearing housing. Experimental comparisons were made by replacing the integral squeeze film bearing damper and the rigid support. The rigid support is a rigid ring of the same size and material as the damper.  
The set of experiments consisted of four working conditions, corresponding to the finite element model in Section 2.3. Before the experiment, the rotor system was dynamically balanced. And an unbalanced mass of 0.15 g-m was applied on the cantilevered disk.  
Figure 9: Schematic diagram of vibration control test platform for an unbalanced single-side cantilevered system with IGFBPD.