| Popis: |
This paper presents the use of wavelet-based wavenumber filtering for damage detection and thickness estimation with Laser-scanning sensing. A piezoelectric transducer provides an excitation at a fixed, single frequency to a structure. Laser Doppler Vibrometer (LDV) with a mirror-tilting device measures subsequent steadystate structural responses, resulting in the full standing wavefield of the structure at the excitation frequency. After then, wavelet-based wavenumber filtering is performed to obtain dominant wavenumber components, which could be used for indicative of structural damage. Mapping processes based on the dominant wavelet-based wavenumber is carried out for damaged area visualization. To estimate the depth of damages, Lamb wave equation is transformed into the wavenumber-thickness equation with the known structural parameters. With this process, the thickness and the thickness reduction by corrosion was accurately identified. Several experiments are performed on thin walled structures, including pipes and plates, with different types of damage, including corrosion and cracks. The experimental investigation into quantitative assessment of welded joints are also performed. The results show that the techniques are very effective in damage size and depth estimation with improved speed. |
