The UK Royal Navy Submarine fleet is powered by Nuclear Steam Raising Plants (NSRP). Due to the alternating levels of power needed during the operation of the submarines, the pipes in the NSRP are prone to mechanical and thermal fatigue. These safety critical components are currently inspected and/or replaced based on very conservative estimates about the level of fatigue damage that exists in them.

This project proposes the development of an ultrasonic technique that penetrates into the fatigue region and characterizes the fatigue state of the components as a whole. This will be achieved by measuring the change in speed and amplitude of Rayleigh waves, as they travel through the fatigued region. The changes in speed and amplitude occur due to the fatigue altering the microstructure of the material, by generating dislocations,microcracs and other defects. This change can be therefore linked to a specific microstructural state and hence a point in the fatigue life of the component -  providing a guidline as to whether a component needs further inspection or replacing. 

Georgios 1
Rayleigh Wave (in red) as it travels along the bottom surface of a plate.