The Significance of Nonlinear Normal Modes for Forced Responses

  • T. L. Hill
  • S. A. Neild
  • A. Cammarano
  • D. A. W. Barton
Conference paper
Part of the Conference Proceedings of the Society for Experimental Mechanics Series book series (CPSEMS)


Nonlinear normal modes (NNMs) describe the unforced and undamped periodic responses of nonlinear systems. NNMs have proven to be a valuable tool, and are widely used, for understanding the underlying behaviour of nonlinear systems. They provide insight into the types of behaviour that may be observed when a system is subjected to forcing and damping, which is ultimately of primary concern in many engineering applications. The definition of an NNM has seen a number of evolutions, and the contemporary definition encompasses all periodic responses of a conservative system. Such a broad definition is essential, as it allows for the wide variety of responses that nonlinear systems may exhibit. However, it may also lead to misleading results, as some of the NNMs of a system may represent behaviour that will only be observed under very specific forcing conditions, which may not be realisable in any practical scenario. In this paper, we investigate how the significance of NNMs may differ and how this significance may be quantified. This is achieved using an energy-based method, and is validated using numerical simulations.


Nonlinear normal modes Nonlinear structural dynamics Backbone curves Energy balancing Nonlinear beam 


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Copyright information

© The Society for Experimental Mechanics, Inc. 2017

Authors and Affiliations

  • T. L. Hill
    • 1
  • S. A. Neild
    • 1
  • A. Cammarano
    • 2
  • D. A. W. Barton
    • 3
  1. 1.Department of Mechanical EngineeringUniversity of BristolBristolUK
  2. 2.School of EngineeringUniversity of GlasgowGlasgowUK
  3. 3.Department of Engineering MathematicsUniversity of BristolBristolUK

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