SIMULATION STUDY ON ULTRASONIC GUIDED WAVE PROPAGATION ACROSS CONTACT INTERFACE

Jointed structures such as bolted and rivet connections are very common in engineering structures. Ultrasonic guided waves are widely used in damage detection of thin wall jointed structures. However, the guided wave propagation at rough interface in the jointed structure is still not fully understood. To this end, this paper theoretically studied the propagation of guided waves across a single contact area by finite element simulation. A finite element model of a lapped aluminium plate with a single contact area was established. The mode transitions at two ends of the contact area was obtained. Then the change of transmission coefficients of A0 and S0 waves at different frequencies with real contact areas were obtained. It was observed that transmission coefficient does not change monotonically with contact area. Carrier modes at the contact area were analysed. Then interference caused by the mode conversion was analysed, and the calculation method of the interference fringes interval was proposed. It was found that one of the main reason for the change of transmission coefficients is the interference. The results of the analysis is helpful to understand the propagation of guided waves at the interface, and is also helpful for the selection of the guided mode and frequency in damage detection of thin-walled joint structures.