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Remediation of deteriorating steel-reinforced concrete structures is a multi-billion dol- lar global problem. Corrosion of embedded steel reinforcing members is the primary cause of the deterioration of these structures. Many .er1.he corrosion products are .. ferrimagnetic and exhibit ferromagnetic resonance (FMR). This thesis describes the design, implementation and testing of two impulse radar systems that exploit FMR to detect and locate ferrimagnetic materials and differenti- ate them from other targets: a free-space system and a transmission line analogue. A novel data processing software solution that interprets data acquired with the hardware systems is also explained. The software allows unequivocal detection and location of ferrimagnetic materials and, in principle, the extraction of intrinsic materials parame- ters from radar signals. The efficacy of the technique and the software and hardware solutions are demonstrated using several synthetic samples. The free space system proves the concept of non-destructive detection and location of ferrimagnetic materials while the transmission line analogue provides a powerful tool for ultra-wideband FMR metrology. Finally improvements to both systems are suggested along with additional potential applications.

Current industrial requirements for nondestructive testing demand defect quantification rather than simple defect detection. This is not a simple task as defects in components, such as cracks, rarely have a simple geometrical shape. Therefore, the influence of defect shape and orientation and its effect on the inspection results needs to be addressed to avoid misinterpretation of the response signals and for a quantitative characterisation of defects. Finite element method (FEM) numerical simulations for eddy current non-destructive evaluation (ECNDE) can provide information on how the induced eddy current interacts with defects and the effect of defect shape and geometry towards the results. Through the analysis of the simulation results, links can be established between the measurements and information relating to the defect, such as 3-D shape, size and location, which facilitates not only forward problem but also inverse modelling involving experimental system specification and configuration; and pattern recognition for 3-D defect information. This work provides a study of the characterisation of angular defects through the technique of visualisation and mapping of magnetic field distribution for pulsed eddy current (PEC) and temperature distribution for PEC thermography. 3-D FEM simulations are utilised to provide the guidelines for experimental designs and specifications; understanding of the underlying physics surrounding a particular defect; and means for features extraction from the acquired responses. Through the study, defect Quantitative Non-destructive Evaluation (QNDE) has been established using the features extracted from the mapping by taking into consideration the angular characteristic of defect in the inspection results. Experimental investigations are then performed to verify the simulation results and the feasibility of the proposed techniques and extracted features to be used in acquiring information about the angular defect. The work concludes that the technique of mapping the resultant distribution from the interaction of eddy currents and defects has provided the vital information needed for defect characterisation. Features extracted from the mapping via numerical investigations have provided the means for the QNDE of angular defects. The work shows that the technique and features introduced has provided an alternative way for defect characterisation and QNDE, which also can be extended its application to other industrial components and research field.

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The sensitivity of acoustic emission (AE) testing coupled with its need for relatively few sensors make it an attractive candidate for structural health monitoring (SHM). The vast majority of reported AE testing is case-specific making it difficult to apply results in a practical manner. This thesis describes a novel quantitative framework which links AE source characterisation experiments and AE-based industrial monitoring systems. The framework is split into two schemes to encompass both types of AE testing.

This thesis reports a comprehensive literature survey on Electromagnetic Non-destructive Evaluation (ENDE) and the investigation of forward problems and inverse problems of Sweep-frequency and Pulsed Eddy Current NDE using numerical and analytical modelling in collaboration with an experimental approach. Firstly, Finite Element simulations have been conducted to (1) evaluate and assess the commercial Finite Element simulation packages, COMSOL and ANSOFT MAXWELL EM in terms of feasibility for simulation of ENDE forward problems including Eddy Current and Magnetic Flux Leakage; (2) apply Finite Element modelling as a comparative approach to verify the proposed analytical methods for forward models and inverse schemes. In parallel with the numerical simulations, much more effort is put into implementation of efficient magnetic-field-based Eddy Current modelling, particularly for Sweep-frequency Eddy Current and Pulsed Eddy Current inspections on multilayered structures. The Extended Truncated Region Eigenfunction Expansion (ETREE) method has been proposed and verified. The formulation of closed-form expressions, which are in series of expansions of eigenfunctions, is useful to rapidly predict signals from solid-state magnetic field sensors rather than the traditional impedance signals measured using induction coils, as the dimension of sensors is taken into account in the model.

In recent years the expectations of non-destructive testing and evaluation (NDT&E) service users have increased from simple defect detection and dimension estimation to the provision of quantitative information about material properties including microstructure, stresses, hardness, etc. Although there are many techniques available to NDT&E service providers, each have their own limitations when used in isolation. For example, magnetic Barkhausen emission measurement has good microstructure and stress characterisation capabilities, but has a limited measurement depth. which is problematic where the property of interest varies with depth, i.e. case hardening. Magnetic flux leakage can detect defects on both the surface under inspection and the opposite surface, but it is very difficult to discriminate between them. However, if two or more inspection techniques are combined in a single system, it is thought that it may be possible to overcome these limitations.

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