Improved Defect Characterisation Using Ultrasonic Arrays

Abstract

There has been a rapid increase in the use of ultrasonic arrays for non-destructive evaluation with the aim of detecting and characterising defects which are detrimental to structural integrity. In parallel with this development, a variety of methods have been introduced to characterise defects using ultrasonic arrays, for example, by using imaging techniques or by extracting the scattering coefficient matrices of the defect. The aim of this thesis is to develop a methodology for improving defect characterisation using ultrasonic phased arrays, which consists of two key parts. The first part is to assess how a characterisation method performs by evaluating its spatial performance against a range of key variables including defect size and orientation. This is done by introducing a mapping approach and taking advantage of computer power and fast hybrid modelling techniques to simulate defects at different locations on a mesh-grid in front of the array and applying the characterisation methods to each simulated defect separately. The second part of the development of the methodology is to study the optimisation of arrays for defect characterisation by exploring the effect of array parameters and parameters associated with the sample and defect on characterisation. These parameters include; aperture size, centre frequency, material noise, defect type and geometric reflectors such as the back-wall. It is shown that different optimal arrays emerge, depending on how the optimal is defined, e.g. the optimal array might be the one that most accurately characterises the defect or produces a given level of characterisation accuracy using the minimum number of elements. It is also shown that the optimal array design varies depending on the size and orientation of the defect as well as its location.

Date of Award	23 Jun 2020
Original language	English
Awarding Institution	University of Bristol
Supervisor	Bruce W Drinkwater (Supervisor)