Mixed-Boundary Component Mode Substitution for Nonlinear Dynamics of Mistuned Shrouded Bladed Disks

摘要

A new mixed-boundary model reduction technique is presented for nonlinear forced response analysis of mistuned bladed disks with shroud friction contacts. In contrast to conventional fixed- or free-mode component mode synthesis (CMS) techniques, blades are reduced in a mixed-boundary fashion. Accordingly, blade component normal modes with a more realistic mixed boundary condition (fixed at blade-disk interface and free at shroud contacts) are incorporated into the reduction basis. Afterward a modal synthesis based on loaded interface modeshapes of the disk is performed to reduce the disk component and the previously retained blade-disk interface degrees of freedom (DOFs). This results in a compact reduced order model (ROM) in which retained physical DOFs contain only shroud contact nodes. During the reduction steps, sector-level frequency mistuning is efficiently introduced into the ROM. In addition, the reduction basis is invariant of the mistuning pattern, which makes the ROM suitable for statistical characterization of nonlinear response levels. The final ROM is computed using one single sector only and with minimal computational effort. Numerical simulations revealed an improved accuracy of the ROM based on the mixed-boundary model in predicting the nonlinear forced response levels of a mistuned bladed disk with shroud friction contacts.