Session: 18: Student poster competition

Paper Number: 118528

118528 - Comprehensive Monitoring of Bolt Loosening Covering Entire Torque Range via Nonlinear Electromechanical Impedance Spectroscopy (Nemis) 

This poster proposes a Nonlinear Electro-Mechanical Impedance Spectroscopy (NEMIS) methodology for the comprehensive monitoring of bolt looseness covering the entire torque range. Distinctive from the conventional Electro-Mechanical Impedance Spectroscopy (EMIS) implemented in the frequency domain, NEMIS utilizes a temporal interrogating signal to obtain the developed nonlinear impedance spectrum. It is capable of evaluating the structural resonance information as the conventional EMIS does, and capturing the Contact Acoustic Nonlinearity (CAN) features simultaneously with only a single Piezoelectric Wafer Active Sensor (PWAS). To have an insight into the mechanism behind NEMIS, a comparative illustration among the conventional EMIS, nonlinear ultrasonic techniques, and the proposed NEMIS was conducted. Subsequently, a reduced-order analytical model was established to simulate the variable rough contact interfaces of the bolted joints at different looseness states. Parametric studies were carried out on the model to demonstrate the higher harmonics and vibro-acoustic modulation features resulting from the bolt looseness. Ultimately, the experimental implementation of NEMIS for the whole lifespan monitoring of the bolt loosening was performed compared with the conventional EMIS method. It was proved that NEMIS could detect both the incipient bolt loosening at an embryo stage and severe loosening of the bolted joints at the terminal period, combining the merits of the conventional EMIS and the nonlinear ultrasonic methodology. Quantification on the severity of the bolt loosening was conducted via both linear and nonlinear damage indices, which presented a consistent trend with the bolt looseness level. The poster finishes with summary, concluding remarks, and suggestions for future work.

Presenting Author: Runye Lu University of Michigan-Shanghai Jiao Tong University Joint Institute,

Presenting Author Biography: Runye Lu is a PhD candidate working on SHM and NDT&E.