9 March 2014 Monitoring bolt torque levels through signal processing of full-field ultrasonic data
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Using full-field ultrasonic guided wave data can provide a wealth of information on the state of a structure through a detailed characterization of its wave propagation properties. However, the need for appropriate feature selection and quantified metrics for making rigorous assessments of the structural state is in no way lessened by the density of information. In this study, a simple steel bolted connection with two bolts is monitored for bolt loosening. The full-field data were acquired using a scanning-laser-generated ultrasound system with a single surface-mounted sensor. Such laser systems have many advantages that make them attractive for nondestructive evaluation, including their high-speed, high spatial resolution, and the ability to scan large areas of in-service structures. In order to characterize the relationship between bolt torque and the resulting wavefield in this specimen, the bolt torque in each of the bolts is independently varied from fully tightened to fully loosened in several steps. First, qualitative observations about the changes in the wavefield are presented. Next, an approach to quantifying the wave transmission through the bolted joint is discussed. Finally, a method of monitoring the bolt torque using the ultrasonic data is demonstrated.
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Colin Haynes, Colin Haynes, Michael Yeager, Michael Yeager, Michael Todd, Michael Todd, Jung-Ryul Lee, Jung-Ryul Lee, } "Monitoring bolt torque levels through signal processing of full-field ultrasonic data", Proc. SPIE 9064, Health Monitoring of Structural and Biological Systems 2014, 906428 (9 March 2014); doi: 10.1117/12.2045024; https://doi.org/10.1117/12.2045024

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