Data fusion for combining techniques to detect and size surface and near-surface defects

In NDT it is important to have a high probability of detection and reliable sizing of defects in a sample. This can be gained by using several techniques, which leads to an increase in cost and time for testing. Another option is to use several techniques combined into a single probe, in which case data fusion for the techniques is possible. We report measurements using a dual probe containing a pair of electro-magnetic acoustic transducers generating and detecting low frequency broadband ultrasonic surface waves, combined with a pulsed eddy current probe. These two techniques are complementary but can be combined to work as competitive or cooperative sensors depending on the type of defect being investigated. Our work gives the depth of surface breaking defects by performing data fusion on certain features of data from each technique in a competitive sense, with data fusion by mathematical algorithm. Further analysis of the results using cooperative data fusion can give details of the depth and type of defect, for example surface breaking or near surface. The dual probe has been demonstrated on several samples, including aluminium and steel samples with several simulated defects on each side.