Dynamic analysis of a bladed disk with friction and fretting-wear in blade attachments

Assembled bladed disks have many contact interfaces (blade-disk joint, blade shrouds, friction dampers...). Because of relative displacements at these interfaces, fretting-wear occurs, which affects negatively the lifetime of the structure. Methods exist to predict fretting-wear in quasi-static analysis. However they don’t predict all the phenomena observed in blade attach-ments on real industrial plants. This paper studies the assumption of a responsibility of dynamics for fretting-wear damage.
A numerical treatment of fretting-wear under vibratory load-ing is proposed. The method is based on the Dynamical La-grangian Frequency Time method. It models unilateral contact through Coulomb’s friction law. The basic idea is to separate time in two scales, slow scale for tribological phenomena and fast scale for dynamics. For a chosen number of periods of vibration, a steady state is assumed and the variables are decomposed in Fourier series. An Alternating Frequency Time procedure is per-formed to calculate the non-linear forces. Then, a Hybrid Pow-ell’s algorithm is used as solver. A quasi-analytical expression of the Jacobian matrix decreases the duration of calculations. This expression is also used to predict new relative displacement at the interfaces due to the increase of wear depth. This method is similar to a prediction-correction method, with wear depth as the term of continuation. Numerical investigations on a bladed-disk with friction contact interfaces illustrate the performances of this method and show the coupling between dynamical and tribological phenomena.