Stiffening Effect and Dry-Friction Damping of Bladed Wheel Model with “Tie-Boss” Couplings - Numerical and Experimental Investigation

Bladed wheel model with tie-boss couplings for numerical and experimental investigation of stiffening and friction damping between tie-bosses is introduced. The modal behavior of FE numerical models of the wheel for two contact limit states, i.e. open and bonded contacts, was ascertained. The experimental modal analysis of the wheel both for open and pre-stressed contacts were performed, too. For detail stiffening and damping effect investigation the physical model of three-blade-bundle was elaborated. The experiments were performed for different excitation forces, excitation frequencies and contact pre-stresses. The dynamics of the bundle with respect to different contact states was evaluated from vibration attenuation after short resonant excitation. It was observed that if the macroslips arise in contacts that eigen-frequencies of the bundle are very close to the eigen-frequencies of open contact model bundle and high damping effect is achieved. If the microslips arise in contacts the eigen-frequencies are close to eigen-frequencies of the bond contact model and low damping is achieved. Hence the stiffening effect is high only in the case of microslips. The slip transition is conditioned by the level of adhesion that must be exceeded by excitation force. The FE model of the wheel and blade triple model with dynamic frictional contacts in the tie-boss couplings were developed and calculated results are compared with experiment.