Identification of free-free modes from constrained vibration data for flexible multibody models

Research output: Chapter in Book/Report/Conference proceedingConference contribution


This paper presents a method for identifying the free-free modes of a structure by utilizing the vibration data of the same structure with boundary conditions. In modal formulations for flexible body dynamics, modal data are primary known quantities that are obtained either experimentally or analytically. The vibration measurements may be obtained for a flexible body that is constrained differently than its boundary conditions in a multibody system. For a flexible body model in a multibody system, depending upon the formulation used, we may need a set of free-free modal data or a set of constrained modal data. If a finite element model of the flexible body is available, its vibration data can be obtained analytically under any desired boundary conditions. However, if a finite element model is not available, the vibration data may be detennined experimentally. Since experimentally measured vibration data are obtained for a flexible body supported by some form of boundary conditions, we may need to determine its free-free vibration data. The aim of this study is to extract, based on experimentally obtained vibration data, the necessary free-free frequencies and the associated modes for flexible bodies to be used in multibody formulations. The available vibration data may be obtained for a structure supported either by springs or by fixed boundary conditions. Furthermore, the available modes may be either a complete set; i.e., as many modes as the number of degrees of freedom of the associated FE model is available, or it can be an incomplete set.

Original languageEnglish (US)
Title of host publication17th Biennial Conference on Mechanical Vibration and Noise
PublisherAmerican Society of Mechanical Engineers (ASME)
Number of pages10
ISBN (Electronic)9780791819777
StatePublished - 1999
EventASME 1999 Design Engineering Technical Conferences, DETC 1999 - Las Vegas, United States
Duration: Sep 12 1999Sep 16 1999

Publication series

NameProceedings of the ASME Design Engineering Technical Conference


ConferenceASME 1999 Design Engineering Technical Conferences, DETC 1999
Country/TerritoryUnited States
CityLas Vegas

ASJC Scopus subject areas

  • Mechanical Engineering
  • Computer Graphics and Computer-Aided Design
  • Computer Science Applications
  • Modeling and Simulation


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