Estimation of Rotational Degrees of Freedom by EMA and FEM Mode Shapes

  • A. Sestieri
  • W. D’Ambrogio
  • R. Brincker
  • A. Skafte
  • A. Culla
Conference paper
Part of the Conference Proceedings of the Society for Experimental Mechanics Series book series (CPSEMS)

Abstract

In this paper a new technique is presented to estimate the rotational degrees of freedom of a flexural structure, using only a limited number of sensors that measure the translational DoFs of the system. A set of flexural mode shapes in a limited number of nodes is obtained by modal testing, while a different set of approximated mode is calculated by a Finite Element Model (FEM) at all the nodes and degrees of freedom of the structure. The technique is based on the classical assumption that the response can be determined by a linear combination of the structure’s mode shapes. The structure’s mode shapes are approximated by using the local correspondence principle for mode shapes, i.e. by using an optimally selected set of finite element mode shapes as Ritz vectors for the true mode shapes. This allows to obtain the rotational response at unmeasured DoFs. The technique is validated by comparing predicted and experimental results.

Keywords

Experimental mode shapes FE mode shapes Rotational DoFs Expansion 

Notes

Acknowledgements

This research is supported by grants from University of Rome La Sapienza and University of L’Aquila.

References

  1. 1.
    Ewins DJ, Gleeson PT (1975) Experimental determination of multidirectional mobility data for beams. Shock Vib Bull 45:153–173Google Scholar
  2. 2.
    Sattinger SS (1980) A method for experimentally determining rotational mobilities of structures. Shock Vib Bull 50:17–27Google Scholar
  3. 3.
    Sestieri A, Salvini P, D’Ambrogio W (1991)Reducing scatter from derived rotational data to determine the frequency response function of connected structures. Mech Syst Signal Process 5(1):25–44CrossRefGoogle Scholar
  4. 4.
    Bello M, Sestieri A, D’Ambrogio W, La Gala F (2003) Development of PZT’s as rotational transducers. Mech Syst Signal Process 17(5): 1069–1081CrossRefGoogle Scholar
  5. 5.
    D’Ambrogio W, Sestieri A (2004) A unified approach to substructuring and structural modification problems. Shock Vib 11(3–4):295–310Google Scholar
  6. 6.
    Brincker R, Skafte A, Lpez-Aenlle M, Sestieri A, D’Ambrogio W, Canteli A (2012) A local correspondence principle for mode shapes in structural dynamics. Mech Syst Signal ProcessGoogle Scholar
  7. 7.
    Skafte A, Brincker R (2012) Estimation of unmeasured dof?s using the local correspondence principle. In: Caicedo JM, Catbas FN, Cunha A, Racic V, Reynolds P, Salyards K, Proulx T (eds) Topics on the dynamics of civil structures, vol 1. Volume 26 of conference proceedings of the society for experimental mechanics series. Springer, New York, pp 265–271. doi: 10.1007/978-1-4614-2413-0_26
  8. 8.
    O’Callahan J, Avitabile P, Riemer R (1989) System equivalent reduction expansion process. Proceedings 7h IMAC, Las Vegas, pp 29–37Google Scholar
  9. 9.
    D’Ambrogio W, Fregolent A (2003) Higher order MAC for the correlation of close and multiple modes. Mech Syst Signal Process 17(3): 599–610CrossRefGoogle Scholar
  10. 10.
    Allemang RL, Brown DJ (1982) A correlation coefficient for modal vector analysis. Proceedings of the 1st International Modal Analysis Conference, November 8-10, Orlando, FL USA, Society for Experimental Mechanics, Inc., Bethel, CT USA, pp. 110–116Google Scholar

Copyright information

© The Society for Experimental Mechanics, Inc. 2013

Authors and Affiliations

  • A. Sestieri
    • 1
  • W. D’Ambrogio
    • 2
  • R. Brincker
    • 3
  • A. Skafte
    • 3
  • A. Culla
    • 1
  1. 1.Dipartimento di Ingegneria Meccanica e AerospazialeUniversit di Roma La SapienzaRomeItaly
  2. 2.Dipartimento di Ingegneria Industriale e dell’Informazione e di EconomiaUniversit dell’AquilaL’Aquila (AQ)Italy
  3. 3.Department of EngineeringAarhus UniversityAarhus CDenmark

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