Research On The Effects Of Viscoelastic Damper To The Dynamics Of Helicopter Drive Shaft System

Vibration and noise reduction is one of the important researches in the helicopter drive shaftsystem. Viscoelastic damper with silicon fluids has an important application in helicopter drive shaftsystem with the simple structure and stable performance, etc. Therefore, the damper’s material,stiffness, damping and effects to the dynamics of helicopter drive shaft system were studied in thispaper.Firstly, the viscoelastic damper’s working principle was studied according to the structure of thehelicopter drive shaft system’s damping support. Feasible material was chose for the viscoelasticdamper with silicon fluids. Outer was polyurethane rubber ring, filled with dimethyl silicon fluidsinside.Secondly, based on the structure of the viscoelastic damper, the stiffness and damping model wasbuilt for the damper. The effects of the dimensional parameters to the rubber’s stiffness were analyzedby the radial formula of rubber bushing. The stiffness model of the silicon fluids ring was set upaccording to the isothermal secant bulk modulus. Based on the friction law of the liquid, the dampingmodel of the silicon fluids ring was studied. The effects of the size parameters and physical materialparameters to total stiffness of the damper were analyzed. In order to improve the life of dampers andthe elastic properties of rubber, the loss factor of the rubber was minimized by vulcanizing. Therefore,the elastic was provided by the rubber and silicon fluids, and the viscous was provided by the siliconfluids only.Finally, based on the Bernoulli-Euler beam, the inertia of axis, shear deformation and gyroscopicmoment were considered in this paper, the free vibration differential equation of the helicopter driveshaft was built for the model. The beam’s transfer matrix was set up according to the bending andshears formula. The model calculated accurately and was suitable for analyzing the single-axisdynamics. The effects of the viscoelastic damper’s stiffness, damping and distribution to thesupercritical drive shaft system’s critical speed, steady-state unbalance response and transientresponse were studied by the transfer matrix method. The analysis results showed that viscoelasticdamper reduced the shaft system’s first-order critical speed, lowered the first-order resonance peak.Therefore viscoelastic damper not only improved the safety margin, but also reduced the transversedisplacement at the first resonance.