Mass Mistuning Reduced Order Models for Bladed Disks With Shroud Friction Joints

Abstract This paper introduces a new reduced order model (ROM) for nonlinear forced response analysis of mistuned bladed disks with localized contact nonlinearities. The developed technique is based on a component mode synthesis (CMS) approach and introduces small frequency mistuning into the final ROM as deviations in the mass matrix. Critical to the development of CMS-based ROMs for mistuned systems is the construction of a reduction basis that remains invariant to mistuning parameters, ensuring the ROM's suitability for statistical analyses. Traditionally, CMS-based reduction techniques for small mistuned systems fall into two major groups: (1) System-level approaches: in which mistuned system modeshapes are represented as a linear combination of tuned modes, typically overlooking mistuning impact on static constraint modes. (2) Component-level approaches: in which mistuning is confined to individual components (or superelements), preserving the independence of the reduction basis from mistuning patterns, typically overlooking mistuning impact on interface degrees-of-freedom (DOFs). The proposed technique combines the strengths of both methods. It adopts a system-level approach, utilizing modeshapes of the fully stuck system within the reduction basis. Furthermore, it eliminates common assumptions on static constraint modes by incorporating mistuning effects directly into the mass matrix. As a result, the constraint modes employed in the reduction basis are precise and remain unaffected by mistuning, ensuring their invariance. A comprehensive comparison between ROMs constructed using the new approach and the full model demonstrates the method strengths through modal and forced response analyses. The proposed approach presents a promising solution for accurate and efficient nonlinear dynamic analysis of mistuned bladed disk systems with shroud friction contacts.