The presented innovative magnetic testing method utilises the fact, that each commercially available electromagnet can not only be used as an actuator, but also comprises internal sensor functions. This allows a huge application variety in the fields of non-destructive testing and condition monitoring of electromagnetic systems during production and within the application in the field.

Volvo Group Truck Technology has the ambition to automate parts of their routine service. Therefore a project was launched to investigate which parts of the routine that could be automated. The idea of this project is to lower the time spent on the service and also improve the working environment for the personnel. The purpose of this thesis is to develop and build a conceptional prototype for a low-cost crack detecting sensor. This thesis is a part of a larger proof of concept project which Volvo GTT runs in cooperation with Robotdalen and Robot Application Center (RAC). The work done in this thesis has been based on literature studies, interviews and company visits. The gathered knowledge and observations was translated into what would be required to fit the needs. This thesis covers different techniques that could be used to detect flaws in braking discs. However, this thesis is mostly focused on one non-destructive method technique based on induced eddy currents. Several non-destructive techniques and conceptual designs has been tested and evaluated with varying results during this project. The result of this thesis was a design that reacts to discontinuities in conductive materials, such as the grey cast iron material used in the Volvo trucks braking discs. The results are represented as a voltage drop change and can be visualized by an oscilloscope. This study shows that the method of choice has the potential to be used as a crack detecting system and that the system can be built reliable with rather cheap components. Further development should aim towards making the design even cheaper and the components should be assembled on a PCB instead of a breadboard in order to make the system less sensitive to noise and easier to assemble alongside the trucks braking discs.

The aim of this study has been to investigate the possibilities to identify lack of glue in finger joints by checking different non-destructive techniques. Specifically, this study puts emphasis on finding a method suitable for an automated and fast industry production line of home furnishing products. The methods investigated are of three main varieties: Sound/vibration Thermography Tomography The most promising method was the high-power ultrasound thermography. This method is fast and reliable, but more research is needed. It is necessary to find out if the thermography waves can penetrate deep enough. Another possible method is computed tomography. This method can take a lot of time, but the speed of scanning depends on the accuracy demanded. / Uppgiften har varit att granska möjligheterna att identifiera bristfälliga trälimningar eller helt avsaknad av lim i fingerskarvar med hjälp av olika metoder som inte förstör materialet, NDT (non-destructive testing). Undersökningen syftar speciellt till att finna en metod som är anpassad till ett effektivt produktionsflöde i industrin. Det måste där med vara en metod som med stor snabbhet kan hitta eventuella fel på produkterna. De metoder som mer omfattande har granskats är ljud/vibration, termografi och tomografi. Den metod som visat sig mest lovande är high-power ultrasound thermography. Tester måste dock utföras för att säkerställa att metoden är passande för ändamålet. Framför allt om de termografiska vågorna tränger in tillräckligt djupt. En annan möjlighet är datortomografi. Denna metod kan vara tidskrävande, men skanningshastigheten beror på hur noggrant mätresultat som erfordras. Här finns också en säkerhetsaspekt som måste beaktas, eftersom röntgenstrålar används.

The focus of this thesis is to derive analytical tools for the design of infrared nondestructive tests in single and multi layer material bodies. This requires the predetermination of the parameters of the experiment such that the infrared image has the required resolution for defect detection. Inverse heat conduction in single and multi-layer materials is investigated to determine the required frequency of excitation in order to obtain a desired temperature at the observation point. We use analytical quadrupole representation to derive a polynomial relation to estimate the frequency of the periodic excitation as a function of the temperature amplitude at a given observation point within the body. The formula includes characteristic geometric and material parameters of the system. The polynomial formula can be an e ective design tool for quick frequency predetermination in the design of non-destructive testing experiments with infrared thermography. The convergence and accuracy of the formula is assessed by comparison with the analytical thermal quadrupole solution and experimental results. We also investigate the e ect of the nite length of the material domain in order to establish the range of applicability of a simpli ed formula based on semi-in nite domain assumption. The e ect of nite length is investigated analytically by using (i) Fourier series which accounts for transients and (ii) Time varying solution associated to the steady state solution when a purely periodic excitation is applied. These results are also compared with numerical solution obtained with commercial nite element software ANSYSTM.

The List is a collection of short stories focusing on the inability to adapt, or learn from self-destructive patterns, and the bizarre ways people reach out for one another when they don't know what else to do.

Free vibrations of a thin elastic circular cylindrical panel localized near the rectilinear edge, propagating along the edge and decaying in its circumferential direction, are investigated in the framework of the two-dimensional equations in the Kircho↵-Love theory of shells. At first the panel is assumed to be infinite longitudinally and semi-infinite along its length of curvature (of course not realistically possible), followed by the assumption that the panel is then finite along its length of curvature and fixed and free conditions are imposed on the second resulting boundary. Using the comprehensive asymptotic analysis detailed in Kaplunov et al. (1998) “Dynamics of Thin Walled Elastic Bodies”, leading order asymptotic solutions are derived for three types of localized vibration, they are bending, extensional, and super-low frequency. Explicit representation of the exact solutions cannot be obtained due to the degree of complexity of the solving equations and relevant boundary conditions, however, computational methods are used to find exact numerical solutions and graphs. Parameters, particularly panel thickness, wavelength, poisson’s ratio, and circumferential panel length, are varied, and their e↵ects on vibration analyzed. This analysis is further extended to investigate localized vibration on the interface (perfect bond) of two cylindrical panels joined at their respective rectilinear edges, propagating along the interface and decaying in the circumferential direction away from the interface. An earlier, similar, localized vibration problem presented in Kaplunov et al. (1999) “Free Localized Vibrations of a Semi-Infinite Cylindrical Shell” and Kaplunov and Wilde (2002) “Free Interfacial Vibrations in Cylindrical Shells” is replicated for comparison with all cases. The asymptotics are similar, however in this problem the numerics highlight the stronger e↵ect of curvature on the decay of the super-low frequency vibrations, and to some extent on the leading order bending vibration.

Acoustic source localization (ASL) is pinpointing an acoustic source. ASL can reveal the point of impact of a foreign object or the point of crack initiation in a structure. ASL is necessary for continuous health monitoring of a structure. ASL in an anisotropic plate is a challenging task. This dissertation aims to investigate techniques that are currently being used to precisely determine an acoustic source location in an anisotropic plate without knowing its material properties. A new technique is developed and presented here to overcome the existing shortcomings of the acoustic source localization in anisotropic plates. It is done by changing the analysis perspective from the angular dependent group velocity of the wave and its straight line propagation to the wave front shapes and their geometric properties when a non-circular wave front is generated. Especially, 'rhombic wave front' and 'elliptical wave front' are dealt with because they are readily observed in highly anisotropic composite plates. Once each proposed technique meets the requirements of measurement, four sensor clusters in three different quadrants (recorded by 12 sensors) for the rhombus and at least three sensor clusters (recorded by 9 sensors) for the ellipse, accurate Acoustic Source Localization is obtained. It has been successfully demonstrated in the numerical simulations. In addition, a series of experimental tests demonstrate reliable and robust prediction performance of the developed new acoustic source localization technique.

La technique du contrôle non destructif (CND) par courants de Foucault (CF) est une solution envisageable pour caractériser l’état de contraintes dans un matériau magnétique. En effet, les propriétés magnétiques d’un matériau magnétique dépendent sensiblement de l’état de contraintes et, par ailleurs, les CF dépendent de la perméabilité magnétique. La technique des CF est potentiellement intéressante comparée à d’autres méthodes de CND, telles que la diffraction des rayons X, car elle est simple à mettre en œuvre, automatisable et peu coûteuse. Dans l'objectif de permettre in fine l’identification inverse de l’état de contraintes, un modèle prédisant l'évolution du signal fourni par un capteur à CF en fonction de l’état de contraintes du matériau ferromagnétique contrôlé a été élaboré dans cette thèse. Ceci implique la mise en place d’une double modélisation. D’une part, l’effet des contraintes sur la perméabilité magnétique a été modélisé par un modèle de comportement magnéto-élastique simplifié dérivé d'une approche multi-échelle. Cette approche permet de décrire la perméabilité magnétique d’un matériau soumis à un chargement multiaxial, en incluant notamment les effets d'anisotropie induite. D’autre part, un modèle reposant sur la méthode des éléments finis a été développé afin de prédire le signal fourni par un capteur à CF en fonction de la perméabilité anisotrope du matériau inspecté. Afin de valider la démarche de modélisation, un protocole expérimental de caractérisation magnétique et par CF a été mis en place. Les résultats de mesure obtenus présentent un bon accord qualitatif avec la modélisation, en l’absence de tout étalonnage. Une procédure d’étalonnage s'appuyant sur une mesure sous contraintes est nécessaire pour atteindre un accord quantitatif. Le modèle développé pourrait être utilisé pour concevoir des sondes à CF idoines et identifier les conditions opératoires optimales pour l'estimation de contraintes dans les matériaux magnétiques. Les procédures d'inversion à mettre en œuvre restent cependant un défi à relever / The non-destructive evaluation (NDE) technique by eddy current (EC) is a conceivable solution to characterize the stress state in magnetic materials. The approach relies on the high sensitivity of eddy current (EC) signals to the magnetic permeability, itself highly dependent on stress. The EC technique is potentially attractive compared to other NDE methods such as X-ray diffraction, due to its simple practical implementation, easiness of automation and low cost. In order to allow eventually the inverse identification of stress states in magnetic materials, a predictive model for the evolution of an EC probe signal as a function of stress has been developed during this thesis. The modelling is done in two steps. First, the effect of stress on the magnetic permeability is described using a simplified version of a multiscale model for magneto-elastic behaviour. This approach allows describing the effect of multiaxial mechanical loadings on the magnetic behaviour of materials including induced anisotropy effects. Then, the EC probe signal is determined as a function of the anisotropic permeability of the stressed material using the finite element method (FEM). In order to validate the modelling approach, an experimental setup for magnetic characterisation and EC measurements was developed. The measurements show a good qualitative accordance with the modelling results, in absence of any calibration. A calibration procedure based on a measurement under stress is necessary to obtain a quantitative agreement. The proposed model can be used to design efficient EC probes and to define optimal operating conditions to evaluate stress in magnetic materials. The development of inversion procedures, however, remains a challenge.

Over the past decade, research into computer vision has proliferated with the goal to incorporate artificial intelligence into a wide range of applications. These applications can be as sophisticated as intelligent assistants in smartphones and self-driving cars or as mundane as text and face recognition. While most of these applications are software based, they represent unique challenges when it comes to industrial implementation. This thesis concentrates on an optical non-destructive testing (NDT) and automatic classification methodology using customized image processing techniques. In contrast to conventional spatial analyses, which are highly susceptible to noise and human perception, our proposed transform domain approach provides a high degree of robustness and flexibility in feature selection and hence a better classification efficiency. Our presented algorithm classifies the Part-Under-Test (PUT) into two bins of either acceptable or faulty using transform domain techniques in conjunction with a classifier. Because the classification is critically dependent on the features extracted from these images, a sophisticated scalable database was created. This thesis applies transform domain techniques such as Discrete Wavelet Transform (DWT) and Rotated Wavelet Transform (RWT) for feature extraction and then classifies the PUT based on those features. Although, this approach achieves promising classification efficiency, it does not meet industrial standards. It was concluded that in order to achieve those standards, the effect of emissivity fluctuations of the PUT should be negated. The research was then extended to apply an image acquisition algorithm in the form of shape from polarization. The approach exploits the partially linearly polarization of reflected light from the PUT surface. It was observed that this method could not only detect if the PUT is faulty or fault free, but also highlight the locations of the flaws.

Guided Wave Testing (GWT) is a relatively new development in non-destructive testing. Conventional Ultrasonic Testing (UT) methods are operated at high frequencies (MHz) and are capable of detecting very small (down to micrometre-scale) flaws within a range of millimetres from a transducer. GWT, however, is carried out at lower frequencies (kHz) and is capable of highlighting the position of volumetric structural detail and discontinuities, such as gross corrosion at a minimum of 9% of the cross-sectional area, tens of metres from a test location. Conventional ultrasonic testing relies on the transmission of bulk waves whereas GWT employs so-called ultrasonic guided waves (UGW). To simplify UGW inspections, several tests are conducted sequentially at a range of different excitation frequencies. The frequency bandwidth of each of these tests needs to be controlled to avoid complexities caused by the frequency dependent nature of the propagation of guided waves. This gives rise to the current GWT inspection procedure, where a number of different narrowband tests are conducted at several distinct frequencies. It is also found that different test circumstances (such as pipe coating or defect type) are inspected more easily with certain excitation frequencies than with others - and the optimum frequency can not always be predicted ahead of time. Thus, where time allows it is often beneficial to carry out a frequency sweep, whereby a large range of excitation frequencies are incrementally generated - for example, from 20 to 80kHz in 1kHz steps. This research proposes a novel approach to the existing pipeline inspection procedure by utilising the information contained within a broadband response. The overarching proposition given by this research is that the current collection procedure be entirely rewritten. This thesis will present ideas related to every area of the inspection procedure beginning with the tuning of excitation signals and concluding with recommendations on how tooling and excitation configuration can be modified to further optimise the technique for broadband excitation.