Experimental investigation for the dynamic mechanical properties of a vertical anisotropically supported rotor

The dynamic mechanical properties of rotors with anisotropic supporting stiffness have been intensively studied in recent decades. However, the transient unbalance response and the whirl motion when passing through backward critical speeds have not been adequately performed. In addition, there is little published experimental data on the influence of the support stiffness anisotropy. This paper attempts to investigate the steady-state and transient unbalance response of the rotor with anisotropic supports. Response characteristics are summarized based on a modified Jeffcott model first. Next, A vertical Jeffcott rotor test rig with anisotropic elastic supports is established, and the stiffness property of different supports is measured. The steady-state unbalance response and the transient response when accelerating are measured accurately and investigated thoroughly. The influence of stiffness anisotropy and the sensor mounting inclination are investigated experimentally, and whirl modes are observed and explained. The results reveal that due to the stiffness anisotropy in the supports, the amplitude and the number of peaks of the steady-state unbalance response in the x and y directions are different, and backward whirl motions can be aroused both in the steady-state and transient unbalance response. The diversity of critical speeds and range of backward whirl regions reduce for the decreasing of stiffness anisotropy. Then we found that the number of peaks and the amplitude of transient unbalance response are relevant to the sensor mounting inclination. Moreover, the experimental results confirm the appearance of straight-line orbits and the alternations of the whirl modes when passing through critical speeds, and the mechanism are specified using the beat vibration theory as well.