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Title: Simulation of ultrasonic monitoring data to improve corrosion characterisation within high temperature environments
Author: Jarvis, Andrew John Christopher
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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Practical applications which involve analyzing how waves scatter from objects with complex shapes span countless scienti c and engineering disciplines. Having been the focal point of much research over the past century, many di erent techniques for simulating such interactions are in common use throughout literature; however there is still an opportunity to improve upon the balance between accuracy and e - ciency o ered by the most commonly implemented methods. A simulation based on the scalar wave distributed point source method is proposed, exhibiting a large im- provement in computational e ciency when compared to the nite element method, and providing greater accuracy than the Kirchho approximation by including phe- nomena such as multiple scattering, surface self-shadowing and edge di raction. The technique is applied to the problem of simulating how ultrasonic pulses re- ect from rough surfaces; the practical application being wall thickness monitoring in high temperature and corrosive environments. Results show that the re ected pulse can take any number of forms, depending on the speci c shape of the scat- tering surface, which can have a dramatic impact on the accuracy of the thickness measurement. Conclusions are drawn about the stability of various time of ight algorithms under conditions of increasing surface roughness. Potential thickness er- ror metrics are also proposed with the aim of estimating measurement uncertainty based on signal shape change. The great e ciency of the simulation technique is further demonstrated by applying it to three dimensional scattering scenarios which would be impossible to carry out using any other method, leading to the proposal of a correction procedure capable of converting results gained in two dimensional geometries to more closely resemble three dimensional results based on the speci c transducer and rough surface characteristics. Simulation validation is carried out by comparison to experimental results in both two dimensional and three dimensional scattering scenarios, showing agreement within the experimental error bounds of the shear horizontal ultrasonic waveguide transducers used by the wall thickness sen- sor. Alternative high temperature structural degradation monitoring applications are also proposed and experimentally veri ed using an array of waveguide transduc- ers, providing monitoring solutions for thermal fatigue crack growth and hydrogen attack.
Supervisor: Cawley, Peter ; Cegla, Frederic Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available