EngD student, 2011 intake
Research: Auto-focus algorithms for the ultrasonic inspection of austenitic stainless steel welds
Sponsoring company: Rolls-Royce plc (Submarines)
Background: Masters in Physics degree (with Honours), University of Warwick, June 2011.
My route to the EngD began with an internship at Rolls-Royce Submarines in 2010. The internship introduced me to the field of Non-Destructive Evaluation and its fundamental importance in the safe operation of the UK’s fleet of nuclear submarines. Shortly after, I secured my place on the EngD programme, and after completion of my Physics degree, I began doctoral research at the University of Bristol. After one year, I moved to permanent placement at Rolls-Royce Submarines in Derby.
Accurate ultrasonic imaging of defects relies upon precise knowledge of the wave-speed within the material under inspection. However, many materials exhibit highly anisotropic and heterogeneous structures post-welding, due to their inherent crystallographic properties and the features of the welding process itself. The resulting coarse grain-structure of the weld gives rise to ‘steering’ of the ultrasonic beam during inspection; a phenomenon occurring due to the directional dependence of wave-speed in a single-crystal. This can lead to a range of inspection difficulties including mis-location of defects, poor weld coverage (i.e. regions where ultrasound does not propagate) and a lower probability of detection.
The aim of the EngD is to develop ‘Auto-focus’ algorithms to correct upon degraded images due to the inherent anisotropy of austenitic steel welds. Austenitic steel welds are prevalent throughout the submarine nuclear plant due to their high fracture toughness and corrosion resistance. Improved images will allow better detection and sizing of defects in welds. Following development and validation of the Autofocus algorithm, the code will be implemented into in-house Rolls-Royce software for deployment on manufacture and in-service inspections of submarines. Anticipated benefits include a reduction in frequency of in-service inspection and whole-life cost of ownership of the submarine fleet.
- Nowers, D. J. Duxbury, J. Zhang and B. W. Drinkwater, ‘Novel ray-tracing algorithms in NDE: Application of Dijkstra and A* algorithms to the inspection of an anisotropic weld’, NDT & E International, 61, p58-66, 2014