Study of Guided Wave Propagation in Water Immersed Samples with Protective Coating

Abstract

The paper presents a study of related to structural health monitoring (SHM) in the maritime environment. The research is focused on thin-walled structural parts. The used phenomena is the guided elastic wave propagation. This type of waves can be used in or- der to obtain information about structural condition and possibly damaged areas. Guided elastic waves can travel in the medium with relatively low attenuation, therefore they en- able monitoring of relatively large parts of structures. In this particular research we focus on objects that are partially immersed in water. In reported investigation piezoelectric transducer was used to excite guided waves and laser vibrometer was used for sensing of the response. The change of wave behaviour is studied by frequency-wavenumber characteristics. The analysis is made by comparing measurements from a dry sample with those from a sample immersed in water. Moreover, samples with protective coat- ings are investigated. Two types of layers were considered that differ with the thickness. In this way it was able to learn about differences in wave propagation for the coated and uncoated samples, both in immersion and in dry conditions. The study provides guide- line on the application of wave-based SHM method for inspecting maritime structures in which the inspected element can be immersed in water and covered with protective coating