Abstract
In this paper, a sensing methodology to detect and characterize early damages such as loose bolts in a joint is developed. The proposed sensing system consists of PZT patches attached on the structural surface, one of which acts as a transmitter of ultrasonic harmonic wave. The incident harmonic wave is scattered by the damage and received by the other patches. When the structure is subjected to the operational or ambient load, it vibrates, and the inherent damages introduce some nonlinear effects into the structural dynamics. This nonlinearity is observed as the phase- and amplitude-modulation of the scattered waves due to the changes in the scattering characteristics synchronous with the structural vibration. By investigating the modulated phase or amplitude of the scattered wave, the nonlinear characteristics of the damages can be specified. Some experiments using a bolted beam are conducted for illustrative purposes.
