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Reducing effects of boundary condition in modal testing of flexible structures

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Abstract

In ground modal testing, soft suspensions are usually employed to simulate the free-free boundary condition for flexible structures, the suspension system will introduce additional stiffness to structures, which causes the measured frequency response functions (FRFs) to deviate from the true value. To obtain the exact FRFs, a novel method is proposed to eliminate the additional effect of the boundary condition based on the Sherman-Morrison-Woodbury formula. Taking account of the position of suspensions and the number of response points, the effects can be eliminated by selecting sufficient measured FRFs. A spring-mass system is adopted to verify the method through simulated numerical experiments, and a flexible beam is employed to verify the additional stiffness elimination in ground modal testing. Results show that the natural frequency of the structure under test has different sensitivities with respect to the suspension effects, and the first-order mode is the most susceptible. When FRFs relevant to the suspension, excitation, and response points are measured, the additional effects of the boundary condition can be removed from measured FRFs.

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Acknowledgments

This work is supported by the National Natural Science Foundation of China (11602112, 52202445), the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (20KJB460003), Qinglan Project of Jiangsu Province of China (2020).

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Authors and Affiliations

  1. School of Mechanical and Electronic Engineering, Nanjing Forestry University, Nanjing, 210037, China

    Dong Jiang, Zhixiang Huang, Yusheng Wang & Xiaochen Hang

  2. COMAC Shanghai Aircraft Design and Research Institute, Shanghai, 200000, China

    Guilun Wang

  3. School of Engineering and Design, Technical University of Munich, Munich, 80539, Germany

    Rui Zhu

  4. Jiangsu Engineering Research Center of Aerospace Machinery, Southeast University, Nanjing, 211189, China

    Rui Zhu

Authors
  1. Dong Jiang
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  2. Zhixiang Huang
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  3. Guilun Wang
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  4. Yusheng Wang
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  5. Rui Zhu
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  6. Xiaochen Hang
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Corresponding author

Correspondence to Dong Jiang.

Additional information

Dong Jiang is an Associate Professor at the College of Mechanical and Electronic Engineering, Nanjing Forestry University. He received his Ph.D. in Mechanics from Southeast University. His research interests including structural dynamics and nonlinear vibration.

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Jiang, D., Huang, Z., Wang, G. et al. Reducing effects of boundary condition in modal testing of flexible structures. J Mech Sci Technol 38, 89–99 (2024). https://doi.org/10.1007/s12206-023-1208-9

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  • DOI: https://doi.org/10.1007/s12206-023-1208-9

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