Identification of Local Debonding in Bolted Panels Using Nonlinear Pseudo-forces

Wei Xu, Mincong Ji, Maosen Cao, Zhongqing Su, Wiesław Ostachowicz

Research output: Chapter in book / Conference proceedingConference article published in proceeding or bookAcademic researchpeer-review


Bolt looseness can occur subject to long-term structural service. With this concern of structural integrity and safety, there is a huge demand to identify bolt-looseness-caused local debonding in connected structural components such as bolted panels. With the aid of non-contact laser scanning, transverse operating deflection shapes (ODSs) of a bolted panel can be measured with high spatial resolutions. Perturbation to the linear transverse dynamic equilibrium of the panel can be regarded as the linear pseudo-force (LPF), which is applied to the debonding region only and vanishes at undamaged locations. However, nonlinearities caused by contact of debonding interfaces during vibrations are not taken into consideration in the LPF model. As a consequence, only linear damage features can be contained in the LPFs which are established on linear ODSs, leading to incompleteness of damage features. Addressing this problem, this study establishes a nonlinear pseudo-force (NPF) model from the nonlinear transverse motion of equation of a beam-type bi-layer panel model with local debonding. Superior to LPFs, NPFs can extract linear and nonlinear damage features from linear and nonlinear ODSs, respectively. Similar to LPFs, NPFs concentrate in the debonding regions to form local peaks. Therefore, the NPF can be utilized as an ideal nonlinear indicator for the identification of local debonding in bolted panels. The applicability of the NPF is experimentally validated by identifying width-through debonding in a steel panel connected by bolts, whose ODSs at linear and nonlinear (higher) harmonics are acquired through non-contact laser scanning measurement. Experimental results reveal that the NPF can extract complete linear and nonlinear damage features, and hence has a higher-dimensional capacity for identifying local debonding in connected structural components such as bolted panels, whose occurrence, location, and size can be graphically characterized.

Original languageEnglish
Title of host publicationHealth Monitoring of Structural and Biological Systems XVIII
EditorsZhongqing Su, Kara J. Peters, Fabrizio Ricci, Piervincenzo Rizzo
ISBN (Electronic)9781510672086
Publication statusPublished - Mar 2024
EventHealth Monitoring of Structural and Biological Systems XVIII 2024 - Long Beach, United States
Duration: 25 Mar 202428 Mar 2024

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceHealth Monitoring of Structural and Biological Systems XVIII 2024
Country/TerritoryUnited States
CityLong Beach


  • bolted panel
  • laser scanning measurement
  • local debonding identification
  • nonlinear harmonics
  • nonlinear ODS
  • nonlinear pseudo-force

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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