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.