IWSHM 2017: Structural health monitoring of the loosening in a multi-bolt structure using linear and modulated nonlinear ultrasound acoustic moments approach

Research output: Contribution to journalArticle

12 Citations (Scopus)


Applying highly accurate clamp loads in bolted joints during assembly and inspections is essential for estimation of the integrity of a joint and reduction of disastrous failures. Non-destructive post-assembly and in-service inspections of joint integrity are vital and significantly reduce maintenance and associated repair costs. Therefore, a bolt control technology able to provide precise direct measurement of bolt loosening state during assembly and in-service is needed. This work proposes an in situ structural health monitoring approach based on the evaluation of linear and nonlinear modulated acoustic moments for the assessment of the loosened state of bolts in a multi-bolted structure. Linear and nonlinear ultrasound methods’ detection accuracy and robustness can be highly dependent on correct frequency selection. The structural health monitoring method suggested uses material resonance and a frequency sweep methodology coupled with a cross-correlation method which identifies significant frequency pairs or higher harmonics used to determine bolt loosening. The proposed approach was tested and successfully validated on three different bolted structures showing that loosening of the structure can be identified accurately with a limited number of transducers. The solution provides a qualitative solution, which identifies degradation in the torque of a bolted structure; furthermore, the developed structural health monitoring method has the potential to become an automatic tool for monitoring the loosened state of bolts in critical complex structural components.

Original languageEnglish
Pages (from-to)1349-1364
Number of pages16
JournalStructural Health Monitoring
Issue number6
Early online date18 Oct 2018
Publication statusPublished - 1 Nov 2018


  • acoustic moments
  • array
  • Bolted structure
  • defect resonance
  • modulation
  • nonlinear ultrasound
  • structural health monitoring
  • ultrasound

ASJC Scopus subject areas

  • Biophysics
  • Mechanical Engineering

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