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research-article

Rotordynamic Energy Expressions for General Anisotropic Finite Element Systems

[+] Author and Article Information
Manoj Settipalli

Honeywell Technology Solutions Lab Pvt. Ltd, Mechanical COE, Devarabisanahalli, Bangalore, India
saikrishnamanoj@gmail.com

Venkatarao Ganji

Honeywell Technology Solutions Lab Pvt. Ltd, Mechanical COE, Devarabisanahalli, Bangalore, India
venkatarao.ganji@honeywell.com

Theodore Brockett

Honeywell Aerospace, Mechanical Systems, Structures, and Dynamics, 111 S. 34th Street, Phoenix, Arizona 85034 USA
theodore.brockett@honeywell.com

1Corresponding author.

ASME doi:10.1115/1.4037722 History: Received July 06, 2017; Revised July 17, 2017

Abstract

It is often desirable to identify the critical components that are active in a particular mode shape or an operational deflected shape (ODS) in a complex rotordynamic system with multiple rotating groups and bearings. The energy distributions can help identify the critical components of a rotor bearing system that may be modified to match the design requirements. Although the energy expressions have been studied by researchers in the past under specific limited conditions, these expressions require computing the displacements and velocities of all degrees of freedom over one full cycle. They do not address the overall time-dependency of the energies and energy distributions, and their effect on the interpretation of a mode shape or an ODS. Moreover, a detailed finite element formulation of these energy expressions including the effects of anisotropy, skew-symmetric stiffness, viscous and structural damping have not been identified by the authors in the open literature. In this article, a detailed account of orbit characteristics and planarity for isotropic and anisotropic systems is presented. An elegant approach to obtaining time-dependent kinetic and strain energies of a mode shape or an ODS directly from the structural matrices and complex eigenvectors/displacement vectors is presented. The expressions for energy contributed per cycle by various types of damping and the destabilizing skew-symmetric stiffness is also shown. The conditions under which the energies and energy distributions are time-invariant are discussed. An alternative set of energy expressions for an isotropic system is also presented.

Copyright (c) 2017 by ASME
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