Dynamic characteristics analysis and the identification signal of the horizontal tail drive shaft system with the ballistic impact damage of a helicopter

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.