Research On Dynamics Of A Drive Shaft With Multi-Supports

A drive shaft with multi-supports is used in the tail drive system of a helicopter. Dynamic characteristics of a drive shaft are concerned with the stability, design of rotational speed, test and dynamic balance. The bending vibration and longitudinal vibration of a drive shaft, the torsional vibration of a drive shaft system with multi-supports are studied in this thesis.Under non-inertia movement coordinate system and nonlinear system, bending vibration of a tilting drive shaft with two supports is studied. Then, bending vibration of a tilting drive shaft with rigid multi-supports and that of elastic multi-supports are respectively analyzed. The bending motion equations, amplitude-frequency response equations of main resonance, approximate steady-state solutions of main resonance and non-main resonance, maximum amplitude of steady-state solutions, topology structure of amplitude-frequency response curves, displacement of bending vibration are derived. The amplitude-frequency response of main resonance, motion stability, amplitude jump, and topology structure of amplitude-frequency response curves are analyzed. Experiments of bending vibration of a drive shaft are done. The results show that a bending motion equation of a drive shaft with rigid multi-supports and that of a drive shaft with elastic multi-supports are respectively similar to that of a drive shaft with two supports. When a drive shaft is in main resonance, perhaps the amplitude jumps and the bifurcation of main resonance appears. When decreasing the eccentric distance and the order of main resonance, increasing damping in a drive shaft, the amplitude of bending resonance can be decreased, and the amplitude jump and bifurcation of main resonance are removed. In condition of increasing damping in the place of larger deflection of a shaft, the effect of the damping is fully brought into play and weight of the shaft is optimized. There is larger energy to avoid bifurcation of main resonance in a system of a composite shaft with rigid multi-supports.Based on testing longitudinal vibration of a drive shaft, the longitudinal vibration is analyzed. The inertial force of eccentric mass and gravity produce longitudinal vibration of a drive shaft. The longitudinal vibration is passive. There is little possibility that the longitudinal vibration of a drive shaft will threaten the safety. Longitudinal vibration of a helicopter drive shaft can be not removed.Simplifying a structural of a tail helicopter drive system and using the boundary conditions of cylinder elements and disks, torsional vibration of a drive shaft system with multi-supports is studied by the variable separation method, the transfer function method, superposition principle of vibration mode and moment of momentum theorem. The torsional vibration mode, orthogonality condition, natural frequency and analytical solution are obtained. A measure method of the frequency response function of a drive shaft system with multi-supports is given.