This project is focussed on the ultrasonic phased array inspection of complex welds – specifically looking at a dual phased array setup. This seeks to address the current challenge faced in ultrasonic NDT when inspecting austenitic, course grained welds. These materials are widely used in critical welds within the oil and gas industry in offshore pipe components and corrosion-resistant cladding, as well as in numerous other industries including nuclear and defence .
The figure below shows a simulated TFM image comparison between fine-grain and coarse grain steel samples containing three ø2 mm side-drilled holes. In the coarse steel sample, the acoustic path is skewed due to inconsistent velocities between grains, and coupled with scattering from grain boundaries provides unreliable defect detection.
Figure 1: CIVA simulated steel (left) and coarse-grained steel (right) TFM image for sample containing 3 ø2mm SDH using 0° 5 MHz probe. Grain size in order of 1 mm.
This research will consider signal processing techniques, as well as the setup configuration to be explored in order to reduce grain noise within these materials.
Numerous imaging techniques and their effectiveness for this application, such as the total focussing method (TFM) and its various adaptations, plane wave imaging (PWI), and phase coherence imaging (PCI). A MATLAB imaging algorithm has been designed and tested for FMC datasets, with the expectation that this will evolve to provide an accompanying imaging platform to a dual array setup.