Novel Frame Model for Mistuning Analysis of Bladed Disk Systems

Abstract

The work investigates the application of a novel frame model to reduce computational cost of the mistuning analysis of bladed disk systems. A full-scale finite element (FE) model of the bladed disk is considered as benchmark. The frame configuration for a single blade is identified through structural identification via an optimization process. The individual blades are then assembled by three-dimensional (3D) springs, whose parameters are determined by means of a calibration process. The dynamics of the novel beam frame assembly is also compared to those obtained from three state-of-the-art FE-based reduced order models (ROMs), namely: a lumped parameter approach, a Timoshenko beam assembly, and component mode synthesis (CMS)-based techniques with free and fixed interfaces. The development of these classical ROMs to represent the bladed disk is also addressed in detail. A methodology to perform the mistuning analysis is then proposed and implemented. A comparison of the modal properties and forced response dynamics between the aforementioned ROMs and the full-scale FE model is presented. The case study considered in this paper demonstrates that the beam frame assembly can predict the variations of the blade amplitude factors, and the results are in agreement with full-scale FE model. The CMS-based ROMs underestimate the maximum amplitude factor, while the results obtained from beam frame assembly are generally conservative. The beam frame assembly is four times more computationally efficient than the CMS fixed-interface approach. This study proves that the beam frame assembly can efficiently predict the mistuning behavior of bladed disks when low-order modes are of interest.