Improvements to Flaw Mapping with Ultrasonic Guided Waves through Signal Control and Spectral Processing

Background

Ultrasound is used to find flaws in man-made structures to assure their structural integrity. Sometimes this involves the use of relatively low frequency ultrasound that is transmitted over tens of meters to rapidly screen for flaws in large volumes that could otherwise be inaccessible to other techniques. These are commonly called guided wave techniques because of the way the sound is constrained by and propagated within the boundaries of the structure. The sound is transmitting through a structure and the responses are recorded as digital waveforms. The processing of the resultant signals is the basis of a large number of ultrasonic techniques and a key area for developing new capability. These inspections can be used to prevent serious incidents of structural failure, such as oil spills, and to prolong the operational life of engineering infrastructure.

The controlled transmission of these waves allows for techniques where sound is focused on one location or where multiple tests at different frequencies are combined to gain more detailed information. Signal processing techniques are involved to both construct the signals to be transmitted and to process the signals that are received. Research has been published on topics such as focusing, spectral processing, de-noising and ultrasonic imaging. There is a need to develop these techniques further and design new techniques to improve the reliability of the detection of discontinuities and for automating data analysis to reduce the burden on the operator.

Project Outline

The PhD programme initially involves a review of the field of ultrasonic guided waves and relevant areas of signal processing. There should be an emphasis on spectral techniques. It is likely to include a review of signal processing in other fields to identify what technology can be transferred to ultrasonic guided wave inspection. Signal processing techniques must be studied, developed and employed to create a means of improving the reliability of detection and for automating data analysis. Then a process of evaluation and validation is required to demonstrate the utility of the techniques.

The techniques must be applied to both simulated and experimental multi-modal signals from complex structures for quantitative performance assessment. The techniques must be quantitatively validated to provide useful information such as time of arrival, propagation distance and wave velocity information. Furthermore, a quantitative comparison is expected to be provided between the novel techniques developed during the PhD programme and the techniques previously employed in supporting literature for both broadband and narrowband waveforms. The outcome of the PhD programme is expected to clarify the advantages and disadvantages of the novel techniques developed during the programme over other existing techniques (found in the literature).

Candidates should have a relevant degree at 2.1 minimum, or an equivalent overseas degree in Computer Science, Electrical Engineering or another scientific field that includes digital signal processing. Candidates with suitable work experience and strong capacity in programming or signal processing are particularly welcome to apply. Overseas applicants should also submit IELTS results (minimum 6.5) if applicable.

About NSIRC

NSIRC is a state-of-the-art postgraduate engineering facility established and managed by structural integrity specialist TWI, working closely with top universities and a number of leading industrial partners. NSIRC aims to deliver cutting edge research and highly qualified personnel to its key industrial partners.

For more information about The National Structural Integrity Research Centre, visit www.nsirc.co.uk