Enhancement in Defect Detection, Location and Sizing in Hollow Axis Rotors, an Innovative Method to Improve Ultrasonic Image Quality: the Multi-SAFT & Multi-Probe Approach.

In this work an innovative system for the non- destructive testing of rotors of turbine is proposed. It allows to identify, to size and to classify discontinuities located inside the volume of the inspectable material. Starting by a data set acquired by UT probes with different angle beams and from different measurement points, the defects of the inspected material are detected and the relative acoustic images are created by applying the multi-SAFT technique. The advantages of this technique lies in the increasing of the detection capability for small discontinuities and in a great precision in the defect location and sizing. By means of this approach, acoustic images representing the detected defects are obtained with high quality. This improvement is mainly due to the spatial and temporal correlations of the measures. The evaluation of the capability of the new system are assessed by means of several experimental results. In particular, the accuracy of the detection is evaluated in terms of the signal-to-noise ratio and of the obtained azimuth/range spatial resolution.