Technique to combine images produced by different propagation modes of guided waves for damage detection and contrast improvement in plate-like structures

• Autor(a) principal: Prado, Vander Teixeira [UNESP]
• Data de Publicação: 2012
• Outros Autores: Higuti, Ricardo Tokio [UNESP], Kitano, Claudio [UNESP], Martinez-Graullera, Oscar, Adamowski, Julio Cezar
• Tipo de documento: Artigo de conferência
• Idioma: eng
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://dx.doi.org/10.1109/ULTSYM.2012.0360; http://hdl.handle.net/11449/73834
• topic: Acoustic radiation; Apodization function; Artificial defects; Compounding techniques; Contrast improvements; Different resolutions; Plate-like structure; Specific interaction; Damage detection; Defects; Plates (structural components)

This paper describes an image compounding technique based on the use of different apodization functions, the evaluation of the signals phases and information from the interaction of different propagation modes of Lamb waves with defects for enhanced damage detection, resolution and contrast. A 16 elements linear array is attached to a 1 mm thickness isotropic aluminum plate with artificial defects. The array can excite the fundamental A0 and S0 modes at the frequencies of 100 kHz and 360 kHz, respectively. For each mode two synthetic aperture (SA) images with uniform and Blackman apodization and one image of Coherence Factor Map (CFM) are obtained. The specific interaction between each propagation mode and the defects and the characteristics of acoustic radiation patterns due to different apodization functions result in images with different resolution and contrast. From the phase information one of the SA images is selected at each pixel to compound the final image. The SA images are multiplied by the CFM image to improve contrast and for the dispersive A0 mode it is used a technique for dispersion compensation. There is a contrast improvement of 47.5 dB, reducing the dead zone and improving resolution and damage detection. © 2012 IEEE.