Study On The Vibration Characteristics Of The Tail Transmission System Of A Helicopter

With its excellent performance of vertical lifting,hovering and high mobility,helicopters are widely used in military and civil fields.As a very important subsystem of the helicopter drive system,the vibration characteristics of the tail drive system directly affect the flight safety of the helicopter.The research on the vibration characteristics of the tail drive system of the helicopter has a certain significance for improving the reliability of the helicopter.In this paper,the vibration characteristics of the tail drive system of a helicopter are studied.The main research work and conclusions are as follows:(1)The finite element modeling of helicopter tail transmission system.According to the geometric model of the actual structure,this paper establishes the finite element simulation model of the helicopter tail transmission system under the condition of service considering the complex nonlinear boundary conditions such as contact and deformation,and verifies the accuracy of its dynamic simulation,which proves the feasibility and reliability of using this more accurate finite element modeling analysis method in the study of the helicopter tail transmission system It lays a foundation for the analysis of the transient dynamics of the wake system.(2)The natural vibration characteristics and its influencing factors of the helicopter tail drive shafting are studied.Based on the analysis of the free mode and the actual constrained mode of the important components of the tail transmission system,such as the tail transmission shaft,the natural frequency and the vibration mode are determined;on this basis,the critical speed of the tail transmission shaft is calculated,and the influence of the support stiffness,the membrane elastic modulus and the prestress on the tail transmission shaft mode is explored;finally,the excitation load of a certain frequency is applied to the tail transmission system,and the different excitation loads are explored The harmonic response of the tail shaft system under frequency torque and axial force.(3)The transient vibration characteristics of the tail drive system and its influencing factors are studied.Through the transient dynamic analysis of the helicopter tail drive system,the stress distribution of the tail drive shaft,the axial and radial vibration,and the relative movement of the tail drive splines are obtained.The paper also studies the influence of the different elastic modulus of the diaphragm on the transient vibration characteristics of the tail drive system,which provides a certain reference value for the design of the diaphragm coupling.It also studies the effect of the larger backlash on the tail drive system after the wear of the splines The simulation results show that the wear of the spline will significantly increase the vibration of the tail shaft and seriously affect the stability of the transmission.