Bayesian restoration of crack images in welds from incomplete and noisy X-ray data

The restoration of crack images in welds calculated from few x-ray projections only is connected with uncertainties which may corrupt the final images, namely: lack of admissible x-ray projections, lack on the projections of data, which definitely indicate the presence of crack, the crack appearance in the projection is frequently hidden by the images of other defects like undercuts, lack of fusion, etc. A complete Bayesian based technique was developed for a multi-step reconstruction of 3D crack images from limited number of 2D projections and checked using simulated and experimental data. A specific equipment for simultaneous circular rotation and out-of-plane tube positioning in connection with a photo diode line camera was developed and tested for in-field inspection and used for measuring the x-ray projections. The Bayesian quasi-3D restoration with Gibbs prior is applied at the last step being preprocessed by the following procedure: estimate the noise level in the 2D images of the object and select...