Ultrasonic Guided Wave Field Modeling in a One-Side Water-Immersed Steel Plate

Abstract

Guided wave testing is one of the most reliable structural health monitoring techniques to identify and evaluate damage in structures. However, guided waves in submerged structures often strongly attenuate that challenges their practicability for safety inspection. This paper presents a numerical study of guided wave propagation in a steel plate that has one side immersed in water. A three-dimensional (3D) finite element (FE) model is employed to provide a visualization of the ultrasonic field in both the plate and the water. It is found that at low frequency range, normal vibrations on the water-free surface of the one side water immersed steel plate predominantly generate quasi-Scholte wave which is an interface mode with low attenuation,. In addition, the fundamental anti-symmetric wave (leaky A0) and fundamental symmetric wave (leaky S0) are too weak to be observed at low frequency but become discernible when the excitation frequency increases. It seems that the interface wave at low frequency range dominating the measured signal from the water free surface can be a promising wave mode to detect damage in storage tanks and pipes filled with water. To further verify the accuracy of the FE simulation, the group and phase velocity of quasi-Scholte wave have been calculated from the simulated out-of-plane displacements measured on the water free surface. Good agreement has been observed between the numerical simulation and analytical solutions. Therefore, it is concluded that the FE model can accurately simulate guided wave propagation for the water immersed plate.KeywordsNon-destructive testingGuided wavesQuasi-Scholte waveFinite element methodFluid-solid interface