To suppress the excessive transcritical vibration of a supercritical rotor, dry friction damper is a popular choice especially in rotorcraft and aero-engine design. In the current work, we focus on the nonlinear dynamics of asymmetrically supported supercritical rotor equipped with a dry friction damper and the influence of support asymmetry on damper’s performance. Governing equations of the rotor/damper system, which fully consider the nonlinear rub-impact and side dry friction effects, are derived. Typical results of symmetrically supported rotor/damper systems are firstly demonstrated and quantitatively compared with experimental counterparts to confirm the predicting capability of the nonlinear dry friction damper model. Afterward, influences of asymmetric direct stiffness and skew-symmetric cross-coupling stiffness are discussed. It is found that direct stiffness asymmetry deteriorates the transcritical vibration attenuation capability of the damper but reduces the width of transcritical region. For system with a severer direct stiffness asymmetry, a larger pre-tightening force is suggested to be imposed. Besides, unstable self-excited vibration induced by skew-symmetric cross-coupling stiffness is found to be well-limited by the dry friction damper within entire interested rotational speed range. Moreover, during critical speed transition, the self-excited frequency component is completely suppressed.
The ballistic impact damage (BID) will change the dynamic characteristics of the horizontal tail drive shaft system (HTDSS) and will directly affect the flight safety of the helicopter. Aiming at the problem of how the BID affects the dynamic characteristics of the HTDSS and how to identify the BID in time, the dynamic characteristics of the HTDSS with the BID are studied in this paper. The BID is simplified as the ideal geometric damage, and the calculation method of the BID is given. The finite element dynamic equation of the HTDSS with the BID is established, and the effect mechanism of the ballistic impact parameters on the dynamic characteristics is revealed. The result shows: the BID causes the mass loss and the stiffness asymmetric of the ballistic impact position of the TDS; the eccentric excitation introduced by the BID leads to the obvious increase of the system response, and the stiffness asymmetry leads to the super-harmonic resonance of the system. The obvious increase of system response and the appearance of 2Ω frequency component can be used as the identification signal of the BID. Finally, the experiment was carried out, which verified the correctness of the established dynamic model, and explained the reliability of the proposed identification signal of the BID.
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