Robust Design of Friction Interfaces of Bladed Disks With Respect to Parameter Uncertainties

Friction damping is a well-known technology in the field of turbomachinery. The design of friction contacts is subject to various uncertainties in the contact parameters and operating conditions. In order to obtain a robust design, it is thus necessary not only to optimize the design for a specific set of parameters but also to assess the performance of the design regarding sensitivities with respect to changes in the parameters. An optimization method for the design of friction interfaces for bladed disks subject to uncertainties has been developed. The nonlinear forced vibrations are computed by efficiently solving the equation of motion using the Multi-Harmonic Balance Method. Coulomb friction and unilateral normal contact constraints are enforced employing an analytical formulation of the Dynamic Lagrangian method. Resonance response levels and frequencies are directly computed with respect to design parameters. Analytically derived sensitivities are then used to obtain the probability for that a certain response level is not exceeded. The method is applied to a tuned blisk in order to obtain the optimum normal preload in the nonlinear shroud coupling subject to a given uncertainty in the level of excitation, for example.