Continuous Monitoring of Residual Torque of Loose Bolt in a Bolted Joint

Zhen Zhang, Menglong Liu, Zhongqing Su, Yi Xiao

Research output: Journal article publicationConference articleAcademic researchpeer-review

14 Citations (Scopus)


Bolted joints are ubiquitous in engineering assets, performing a critical role of transferring loads among interconnecting components. Effectual inspection and monitoring of loosening of the bolts throughout their intended service life warrants a reliable service of the joints. In this study, identification of bolt loosening and quantitative estimate of the residual torque for three types of joints was attempted, theoretically and experimentally, using two approaches in a comparative manner: a wave energy dissipation (WED)-based linear acoustic approach and a contact acoustic nonlinearity (CAN)-based vibro-acoustic modulation (VM) method. In the former, an analytical model, residing on the Hertzian contact theory, was established to link the WED to the residual torque of a loose bolt. In the latter, the contact stiffness at the interconnecting interface, when a pumping vibration introducing perturbation to probing waves, was calibrated in terms of a Tayler series, on which basis a modulation index was constructed. With the index, nonlinear signal spectral features were quantitatively associated with residual torque. The two approaches were validated experimentally, to find a good agreement between theoretical prediction and experimental estimate. The comparison between two approaches reveals that the nonlinear VM-based method offers enhanced accuracy and sensitivity to bolt loosening than a linear WED-based approach, with additional capacity of detecting bolt loosening in multi-type joints.
Original languageEnglish
Pages (from-to)278-285
Number of pages8
JournalProcedia Engineering
Publication statusPublished - 1 Jan 2017
Event6th Asia Pacific Workshop on Structural Health Monitoring, APWSHM 2016 - Hobart Function and Conference Center, Hobart, Australia
Duration: 7 Dec 20169 Dec 2016


  • bolt loosening
  • Bolted joint
  • contact acoustic nonlinearity
  • vibro-acoustic modualtion
  • wave energy dissipation

ASJC Scopus subject areas

  • General Engineering


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