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Sensing & Measurement

Peter Cawley: Transition from Nondestructive Testing (NDT) to Structural Health Monitoring (SHM): Potential and Challenges

A plenary talk from SPIE Smart Structures/NDE 2014

31 March 2014, SPIE Newsroom. DOI: 10.1117/2.201403.27

There is a gradual shift in emphasis from periodic inspection with detachable transducers (NDT) to permanently installed monitoring systems giving information about the structural integrity at pre-programmed intervals or on demand (SHM). The drivers of this change are discussed, together with the requirements of successful SHM systems. Particular issues are that NDT often involves scanning and this is not possible with typical SHM configurations; it therefore becomes important to cover a significant area of structure from each transducer position. Guided waves provide a possible solution to this problem and permanently installed guided wave pipe inspection systems are now available. The sensitivity obtained with a permanently installed system is significantly better than that in a one-off test as baseline subtraction can be employed. However, this is far from trivial as it is necessary to compensate for benign changes such as temperature. The guided wave technique does not provide accurate remaining thickness information and is best complemented by point measurements at selected locations. Another issue is that the SHM transducers must survive in operational conditions, which is particularly difficult at high temperatures. Recent work at Imperial College and associated spin-out companies on solutions to these problems is discussed.

Peter Cawley received BSc and PhD degrees in Mechanical Engineering from University of Bristol in 1975 and 1979 respectively. He worked in industry from 1979-1981 and then joined the Mechanical Engineering Department at Imperial College, London, initially as a lecturer and then successively senior lecturer, reader and professor. He is now head of the Imperial College Mechanical Engineering department and leads the NDE research group; he is also the principal investigator of the UK Research Centre for NDE (RCNDE) that has its head office at Imperial College. He has published over 160 refereed journal papers and a similar number of conference papers in this field and holds 4 current patents. Peter Cawley is a fellow of the Royal Academy of Engineering and of the Royal Society. He is a director of two spin-out companies set up to exploit technology developed in his research group (Guided Ultrasonics Ltd and Permasense Ltd), and he is a consultant to a variety of industries.