In this thesis, a monitoring system using circumferential guided waves is developed to detect axial cracking in piping and pipe components. Guided waves inspection is attractive as it is much faster than current slow manual inspection methods deployed in nuclear reactors however it is traditionally less sensitive. The use of guided waves in a monitoring configuration as a Structural Health Monitoring (SHM) technique has the potential to boost the traditionally low sensitivity of the technique while retaining the large volumetric coverage. If the guided wave transducers are fixed to the inspection geometry and take continuous measurements; a dataset can be developed that can be analysed using recently developed signal processing techniques to increase the sensitivity.
In this project, a novel guided wave monitoring technique was developed based on a pitch-catch configuration of two transducers offset circumferentially and a defect detection technique based on multiple revolutions of the guided waves. This technique was shown to be a viable monitoring technique with commercially relevant sensitivity. The addition of a second pair of transducers circumferentially offset from the first pair was shown to significantly increase the sensitivity of the SHM system and give full volumetric coverage for the detection of axial defects. Defect detection capability was then demonstrated on a complex component containing several pipe features and a long duration monitoring experiment was performed which highlighted to need to improve the stability of the amplification for the SHM system before commercial adoption is possible. The aid this, two viable calibration techniques based were developed to improve the stability of the system based.
This work has demonstrated the real-world viability of circumferential guided waves to detect axial cracks at industrially relevant sensitivity when used as a monitoring technique.