Guided Lamb wave tomography using angle beam transducers and inverse Radon transform for crack image reconstruction

In this work, guided wave testing (GWT) and computed tomography (CT) imaging were combined to extract relevant information about the location and size of cracks in an aluminum plate. The GWT signals were obtained with two angle beam transducers mounted in pitch-catch configuration. Signal processing techniques (such as Hilbert and Wavelet transforms) and statistical functions (such as skewness and kurtosis) were implemented to extract relevant features from the GWT signals. Parallel- beam projections of six different features were obtained and applied as input in computed tomography imaging reconstruction using inverse Radon transform. The obtained results, using the projections of each individual feature, show that five of the six selected features contain information about the defect location. From the five reconstructed images with relevant information about the crack, image fusion techniques were applied to get complementary information from multiple source images into one single image. The fusion of the five reconstructed CT images provided an approximate location of the crack as well as an approximate angle of orientation of the crack.