Experimental Study on Static and Dynamic Characteristics of Multi-leaf Air Foil Bearings

Gas foil bearings are widely used because of their high speed, no pollution, and long operating life. Today’s gas foil bearings have developed into the fourth generation multi-leaf air foil bearings. Multi-leaf air foil bearings have good characteristics due to the mutual overlap of the top foils to generate preload force, the bump foil provides elastic support, and combined with the surface coating. This paper studied the static and dynamic characteristics of multi-leaf air foil bearings through experimental methods, static characteristics and dynamic characteristics experimental benches were designed and built, respectively. The static characteristics experiment analyzed the static loading force and displacement hysteresis curves of the multi-leaf air foil bearing to obtain the stiffness characteristics of the bearing. The dynamic characteristics experiment obtained the stiffness and damping characteristics of the bearing through two methods: time domain and frequency domain analysis. In addition, the effects of different frequencies, different amplitudes and different preload forces on the dynamic characteristics of multi-leaf air foil bearings were studied, as well as the effects of the hysteresis curve on dynamic loading force and displacement. Experimental results showed that during the static characteristic experiment, the static loading force and displacement hysteresis curves did not coincide with each other. The static stiffness increased with the increase in displacement and presented a nonlinear distribution. When push-pull loading reached the maximum load, the loading direction was reversed, and the stiffness would also mutate. During dynamic characteristics experiments, the bearing stiffness and damping characteristics obtained by the two methods in the time domain and frequency domain were similar, proving the accuracy of the data processing method. Frequency had little effect on stiffness and hysteresis curves. The higher the frequency, the smaller the damping. Frequency had the most obvious effect on damping. The larger the amplitude, the smaller the dynamic characteristics of the bearing and the larger the hysteresis curve. The greater the external preload force, the greater the bearing dynamic characteristics and hysteresis curve. Amplitude and external preload had a certain influence on bearing stiffness and damping as well as hysteresis curve. The presented experimental data could provide a valuable reference.