Obtaining Linear FRFs for Model Updating in Structures with Multiple Nonlinearities Including Friction

Conference paper
Part of the Conference Proceedings of the Society for Experimental Mechanics Series book series (CPSEMS, volume 35)


Most of the model updating methods used in structural dynamics are for linear systems. However, in real life applications structures may have nonlinearity. In order to apply model updating techniques to a nonlinear structure, linear FRFs of the structure have to be obtained. The linear dynamic behavior of a nonlinear structure can be obtained experimentally by using low forcing level excitations, if friction type of nonlinearity does not exist in the structure. However when the structure has multiple nonlinearities including friction type of nonlinearity, nonlinear forces due to friction will be more pronounced at low forcing level excitations. Then it will not be possible to measure linear FRFs by using low level forcing. In this study a method is proposed to obtain linear FRFs of a nonlinear structure having multiple nonlinearities including friction type of nonlinearity by using experimental measurements made at low and high forcing levels. The motivation is to obtain FRFs of the linear part of the system that can be used in model updating of a nonlinear system. The method suggested can also be used as a nonlinear identification method for nonlinear systems. The proposed method is validated with different case studies using SDOF and lumped MDOF systems and simulated experimental data. The effect of the excitation frequency, at which experiments are carried out, on the accuracy of the proposed method, is also demonstrated.


Nonlinear identification Nonlinearity Friction nonlinearity Model updating Nonlinear structures 


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Copyright information

© The Society for Experimental Mechanics, Inc. 2013

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringMiddle East Technical UniversityAnkaraTurkey
  2. 2.MGEO DivisionASELSAN Inc.AnkaraTurkey
  3. 3.Department of Mechanical EngineeringMiddle East Technical UniversityAnkaraTurkey

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