Component-Mode-Based Reduced Order Modeling Techniques for Mistuned Bladed Disks—Part II: Application

R Bladh,C Pierre,M P Castanier

doi:10.1115/1.1338948

Abstract

In this paper, the component-mode-based methods formulated in the companion paper (Part I: Theoretical Models) are applied to the dynamic analysis of two example finite element models of bladed disks. Free and forced responses for both tuned and mistuned rotors are considered. Comprehensive comparisons are made among the techniques using full system finite element solutions as a benchmark. The accurate capture of eigenfrequency veering regions is of critical importance for obtaining high-fidelity predictions of the rotor’s sensitivity to mistuning. Therefore, particular attention is devoted to this subject. It is shown that the Craig–Bampton component mode synthesis (CMS) technique is robust and yields highly reliable results. However, this is achieved at considerable computational cost due to the retained component interface degrees of freedom. It is demonstrated that this problem is alleviated by a secondary modal analysis reduction technique (SMART). In addition, a non-CMS mistuning projection method is considered. Although this method is elegant and accurate, it is seen that it lacks the versatility and efficiency of the CMS-based SMART. Overall, this work shows that significant improvements on the accuracy and efficiency of current reduced order modeling methods are possible.

Highlights

W HEN modeling the dynamics of a complex structure, it is often impractical to perform a nite element analysis of the entire structure
In Component mode synthesis (CMS), the dynamics of a structure are described by selected sets of normal modes of the individual component structures, plus a set of static vectors that account for the coupling at each interface where component structures are connected
This paper introduceda techniquefor reducingthe size of a Craig– Bampton CMS2,5 model by improving the representation of the interface between component structures

Summary

Characteristic Constraint Modes for Component Mode Synthesis

To cite this version: Matthew Castanier, Yung-Chang Tan, Christophe Pierre. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. Yung-Chang Tan, and Christophe Pierre University of Michigan, Ann Arbor, Michigan 48109-2125. When the characteristic constraint modes are truncated, a CMS model with a highly reduced number of degrees of freedom may be obtained. It is shown that relatively few characteristic constraint modes are needed to yield accurate approximationsof the lower natural frequencies. This method yields physical insightinto the mechanisms of vibration transmission in complex structures, and it provides an excellent framework for the ef cient calculation of power ow.

Introduction

Component Mode Synthesis and Constraint Modes

NC N

Findings

Conclusions