No description available.

The main objective of the thesis „Electronic noise temperature dependence of piezoceramic sensors“ is to design the measuring set-up for the measurement of the piezoceramic sensor noise temperature dependence. The application for the control of the measurement process is realized. The theoretic chapter is focused on the properties of materials for the production of piezoceramic sensors. The basic effects related to the piezoceramic properties and the material structure is described in this part. Next chapter is focused on the technology of production of used piezoceramic. The properties of solid solutions as PbZrO3 – PbTiO3, and the non-destructive methods of the material testing are discussed. Our attention is concentrated to methods of acoustic emission. The next chapter is concerned on the realization of the measuring set-up and program equipment. The tested sample is the acoustic emission sensor made of piezoceramic material PCM-51. It is placed in the cylinder chest which is heated by the DC current source. The temperature measurement is realized by the data acquisition switch unit. The results of measurements are saved in PC and they are analyzed using MATLAB program. As a result we receive the frequency spectra of the electric noise voltage spectral density SU. The temperature dependencies of resonant peak value and frequency are determined from these spectra.

Elektromagnetisk provning (ECT) har blivit en av de mest använda metoderna för attkvalitetssäkra produkter där icke-destruktiv testning av material krävs. Vid provning av ståltrådinteragerar utrustningen med det testade materialet och upptäcker ytdefekter och, i vissomfattning, om strukturen skiljer sig från det kalibrerade provet. Om produkten befinner sigutanför specifikationen, skrotas den eller ombearbetas. Denna Mastersuppsats undersökerkalibreringsförfarandet för elektromagnetisk provning som utförs av Suzuki Garphyttan, som är enav de största tillverkarna i världen av ventil- och transmissionsfjädrar för bilindustrin. Genom deslutsatser som framgår av denna rapport, som baseras på undersökningar gjorda i vetenskapligaartiklar och genom att analysera den data som inhämtats från produktionen, presenteras enstandardisering av kalibreringsförfarandet. Detta är nödvändigt för att säkerställa såväl testernastillförlitlighet, såväl som minimering av risken för att skrota ut material på grund av felaktigainställningar, till exempel på grund av otillräckligt signal-brus (S/N)-förhållande. Fokus ligger påsond-baserad, roterande testning, i denna avhandling kallad circografen, eftersom den är manuelltkalibrerad.Några av de konstaterade resultaten i rapporten är:● Standard Operating Procedures (SOP)-baserade instruktioner implementeras i företagetskvalitetssystem. Detta för att minska variationer i kvalitet mellan olika operatörer ochmaskiner.● Ett förslag på intervaller för värden (fasvinkel, förstärkning, korrigering av filter och såvidare) presenteras. Detta är baserat på insamlad unik produktionsdata från operatöreroch utförda test.● Fasvinklarna som används varierar inom specifika intervaller och bestäms av materialval iallmänhet och frekvensval i synnerhet.● Konduktivitets- och permeabilitetsvärdena för oljehärdad tråd, liksom penetrationsdjupetför tre olika frekvenser presenteras.● Härdningsfel kan inte detekteras i roterande provning● Ökat kolinnehåll minskar den elektriska ledningsförmågan och ger ökad resistivitet, vilketgör att fasen flyttar sig och resulterar i ett minskande gap mellan brussignal ochspricksignal. / Eddy current testing (ECT) has become one of the most extensively used methods to secure theproducts and constructions when non-destructive testing is required. In typical cases of steel wiretesting, the equipment interacts with the tested material and discovers surface defects and, to alimited extent, if the inner structure is differing from the calibration sample. If the product isfound to be outside specification, it is either scrapped or reworked. This master thesis investigatesthe Eddy current testing calibration procedures performed by steel wire manufacturer SuzukiGarphyttan, which is one of the largest producers in the world of valve and transmission springwire for the automotive industry. By the research shown in this thesis, based on the investigationmade in scientific papers and by analyzing data extracted from production, a standardization ofthe calibration procedure is being presented. This is to secure both the testing reliability, andminimizing the risk of scrapping material due to inaccurate settings, for example due toinsufficient signal to noise (S/N) ratio. The focus is on probe-based, rotating testing, in this thesiscalled the circograph, since it is manually calibrated.Some of the findings established in the report: Standard Operating Procedures (SOP) based instructions is being implemented in thecompany's Quality system. This is to decrease the process variations between differentoperators and machines. Suggestions of intervals for values (Phase angle, gain, filter correction and so forth) arepresented. These values are based on collected unique production data from operators andmachines, as well as performed tests. The phase angles used are ranging between specific value intervals, and set by materialchoice in general and choice of frequency in particular. The conductivity and permeability values for oil-tempered wire, as well as penetrationdepth for three different frequencies, are presented. Hardening error cannot be detected in the circograph. Increased carbon content is decreasing conductivity and increasing resistivity, causing thephase to move slightly and decreasing the gap between noise signal and crack signal.

There is a need to monitor the existence and effects of damage in structural materials. Aircraft components provide a much publicized example, but the need exists in a variety of other structures, such as layered materials used in food packaging industries. While several techniques and models have been proposed for material characterization and condition monitoring of bulk materials, less attention has been devoted to thin sheets having no flexural rigidity. This study is therefore devoted to the development of a new method for acoustic Non-Destructive Testing (NDT) and material characterization of thin sheets used in food packaging materials or similar structures. A method for assessing the strength in the presence of crack of thin sheets used in food packaging is first presented using a modified Strip Yield Model (SYM). Resonance frequency measurement is then introduced and it is shown, at low frequency range (less than 2kHz), that a change in the physical properties such as a reduction in stiffness resulting from the onset of cracks or loosening of a connection causes detectable changes in the modal properties, specifically the resonance frequency. This observation leads to the implementation of a simple method for damage severity assessment on sheet materials, supported by a new theory illustrating the feasibility of the detection of inhomogeneity in form of added mass, as well as damage severity assessment, using a measurement of the frequency shift. A relationship is then established between the resonance frequency and the material’s elastic property, which yields a new modality for sheet materials remote characterization. The result of this study is the groundwork of a low-frequency vibration-based method with remote acoustic excitation and laser detection, for nondestructive testing and material characterization of sheet materials. The work also enhances the feasibility of the testing and condition monitoring of real structures in their operating environment, rather than laboratory tests of representative structures. The sensitivity of the new experimental approach used is liable to improvement while being high because the frequency measurement is one of the most accurate measurements in physics and metrology.

This work deals with the possibility of use of intelligent methods in construction machines control. These methods are based on GPS in combination with using laser and ultrasonic technology. There is in detail described especially control by robotic total station and 3D control, which includes digital model of construction site. The new trends of control are especially applied on the vibratory rollers. There are taken into consideration: achievement of sufficient degree of compaction on the basis of on-line information about conditions of subsoil.

L’objectif de ce travail est de positionner l’imagerie terahertz comme un nouvel outil dédié à la métrologie et au contrôle non destructif. Ses propriétés étonnantes à la fois de forte pénétration dans les matériaux diélectriques et de longueur d’onde de dimension millimétrique voire submillimétrique en font un outil très enthousiasmant pour des applications comme le contrôle non destructif (CND).En premier lieu, nous avons présenté deux techniques d’imagerie : une consistant à déplacer l’objet, point par point, dans un faisceau terahertz focalisé pour reconstruire, pixel par pixel, une image en deux dimensions. L’autre technique repose sur l’utilisation d’un objectif et d’un capteur matriciel à l’état de l’art fonctionnant à température ambiante. Ainsi nous avons imagé des objets d’intérêts, sans déplacement mécanique. Bien que cette dernière technique soit beaucoup plus rapide que l’imagerie point par point, la qualité des images obtenues n’est pas comparable et ceci à cause de deux verrous. Ainsi, une partie du travail a consisté en l’étude des stratégies d’éclairage pour limiter les effets optiques interférentiels induits par la cohérence de la source. De plus, en déployant des simulations de toute la chaine optique avec le logiciel Zemax, de nombreuses images de qualité permettent d’envisager des applications en imagerie 2D (métrologie, CND) et en imagerie 3D. Ainsi, deux techniques complémentaires de reconstruction tomographique sont expérimentées sur des images obtenues en temps réel ; une technique inspirée de l’imagerie par rayon X et une technique utilisée en microscopie optique 3D qui exploite la profondeur de champ réduite de l’objectif. Enfin, plusieurs études spectroscopiques et métrologiques sont menées afin d’évaluer le comportement des matériaux et la dimension des objets à partir de leurs images THz en 2D ou avec leur reconstruction tomographique 3D. Les travaux effectués constituent les briques de base au déploiement de l’imagerie terahertz vers le domaine applicatif grâce à une qualité d’image incomparable et des acquisitions en temps réels. / The aim of this work is to position terahertz imaging as a new tool dedicated to metrology and non-destructive testing. Its astonishing properties of both high penetration in dielectric materials and wavelength millimeter or even submillimetric make it a very exciting tool for applications such as non-destructive testing (NDT).First, we presented two imaging techniques: one to move the object, point by point, in a focused terahertz beam to reconstruct, pixel by pixel, a two-dimensional image. The other technique is based on the use of a lens and a matrix sensor in the state of the art operating at room temperature. Thus we have imaged objects of interest, without mechanical displacement. Although this last technique is much faster than point-by-point imaging, the quality of the images obtained is not comparable and this because of two drawbacks. Thus, part of the work consists in the study of lighting strategies to limit the interferential optical effects induced by the coherence of the source. In addition, by deploying simulations of the entire optical chain with Zemax software, numerous quality images make it possible to consider applications in 2D (metrology, NDT) and 3D imaging. Thus, two complementary tomographic reconstruction techniques are tested on images obtained in real time; a technique inspired by X-ray imaging and a technique used in 3D optical microscopy that exploits the reduced depth of field of the lens. Finally, several spectroscopic and metrological studies are carried out in order to evaluate the behavior of the materials and the dimension of the objects starting from their THz images in 2D or with their 3D tomographic reconstruction. The work done is the foundation for deploying terahertz imagery to the application domain with unmatched image quality and real-time acquisition.

Le collage suscite un intérêt important pour remplacer les techniques traditionnelles d’assemblage, car il permet d’alléger les structures via une meilleure répartition des contraintes, et également de limiter les contraintes liées à l’assemblage de matériaux différents. Cependant, l’absence de technique de contrôle non destructive robuste de la qualité du collage et plus particulièrement de l’adhésion freine son développement en particulier dans le domaine aéronautique. Dans ce travail une méthode d’inspection ultrasonore d’interfaces collées qui doit révéler des défauts d’adhésion est proposée. Cette technique est validée sur un système représentatif d’applications industrielles, à savoir une liaison entre substrats métalliques liés par un adhésif époxy en film de faible épaisseur. Des défauts ont été introduits au sein de l’interface adhésive (dans l’adhésif ou à l’interface adhésif/substrat) de façon à simuler des défauts rencontrés en environnement industriel. Afin d’améliorer les capacités de détection des méthodes ultrasonores linéaires usuelles, des algorithmes de reconstruction des courbes de dispersion optimisés ont été développés. Cependant, les ondes guidées ne se sont pas montrées suffisamment sensibles à des interfaces faibles dans cette configuration, pour des adhésifs de faible épaisseur et lorsqu’une incertitude des épaisseurs des matériaux est tolérée. Dès lors, des méthodes de contrôle reposant sur l’interaction non-linéaire entre une onde ultrasonore de forte amplitude et un défaut sont proposées car moins système dépendant. Pour détecter et quantifier ces nonlinéarités, des ultrasons suffisamment énergétiques doivent être générés, ce qui implique généralement l’usage de dispositifs électroniques de puissance potentiellement intrinsèquement non-linéaires. Pour contourner ces limitations technologiques, un dispositif dédié est proposé, utilisant des traducteurs alimentés sous tension faible et placés sur un objet réverbérant. L’émission de signaux complexes préalablement établis par étalonnage permet par retournement temporel de concentrer l’énergie acoustique temporellement et spatialement, pour générer des déplacements particulaires ultrasonores de fortes amplitudes à la surface de l’échantillon contrôlé. Pour valider cette approche, le dispositif est utilisé pour contrôler des interfaces collées au sein desquelles différents types de défauts de collage ont été introduits : pollutions (particules de PTFE, démoulant, trace de doigt, etc.), insert. Les échantillons sont finalement testés mécaniquement pour évaluer la sensibilité de la résistance des interfaces à la présence de ces défauts. / Bonding is of great interest to replace traditional assembly techniques, as it makes it possible to lighten structures, through a better distribution of stresses but also to limit the stresses associated with assembling different materials. However, the lack of a robust non-destructive control technique for bonding quality and more particularly adhesion slows down its development, particularly in the aeronautical field. In this work an ultrasonic inspection method of glued interfaces which should reveal defects in adhesion is proposed. This technique is validated on a system representative of industrial applications, metal substrates bonded by a thin film epoxy adhesive. Defects have been introduced into the adhesive interface (in the adhesive or at the adhesive/substrate interface) in order to simulate defects encountered in an industrial environment. In order to improve the detection capabilities of conventional linear ultrasonic guided waves methods, algorithms for reconstructing optimized dispersion curves have been developed. However, the guided waves were not sufficiently sensitive to low interfaces in this configuration, where adhesives are thin, and an uncertainty of material thickness is tolerated. Therefore, control methods based on the non-linear interaction between a high amplitude ultrasonic wave and a defect are proposed. To detect and quantify these non-linearities, sufficiently energetic ultrasound must be generated, which generally involves the use of potentially intrinsically non-linear electronic power devices. To overcome these technological limitations, a dedicated device is proposed, using transducers powered under low voltage and placed on a reverberant object. The emission of complex signals previously established by calibration makes it possible to concentrate acoustic energy temporally and spatially, to generate after time reversal ultrasonic particle movements of high amplitude on the surface of the controlled sample. To validate this approach, the device is used to control glued interfaces in which different types of gluing defects have been introduced: pollution (PTFE particles, release agent, fingerprints, etc.), insert. The samples are finally mechanically tested to assess the sensitivity of the interface resistance to the presence of these defects.

Ground penetrating radar (GPR) technology has existed for many decades, but it has only been in the last 20 to 30 years that it has undergone great development for use in near surface ground investigations. The early 1980's saw the first major developments in the application of GPR for pavements (i.e. engineered structures designed to carry traffic loads), and it is now an established investigation technique, with generic information included in several national standard guidance documents. Analysis of GPR data can provide information on layer depths, material condition, moisture, voiding, reinforcement and location of other features. Assessing the condition of pavements, in order to plan subsequent maintenance, is essential to allow the efficient long-term functioning of the structure and GPR has enhanced and improved the range and certainty of information that can be obtained from pavement investigations. Despite the recent establishment of the technique in pavement investigation, the current situation is one in which GPR is used routinely for pavement projects in only a minority of countries, and the specialist nature of the technique and the sometimes variable results that are obtained can mean that there is both a lack of appreciation and a lack of awareness of the potential information that GPR can provide. The fact that GPR is still a developing technique, and that many aspects of its use are specialised in their nature, means that there are also several technical aspects of GPR pavement investigations which have not been fully researched, and knowledge of the response of GPR to some material conditions has not been fully established. The overall aim of this EngD research project was to provide improved pavement investigation capabilities by enhancing the methodologies and procedures used to obtain information from GPR. Several discrete research topics were addressed through various research methods including a literature review, fieldwork investigations, experimental laboratory investigations and a review of previously collected data. The findings of the research allowed conclusions and recommendations to be made regarding improved fieldwork methodologies, enhancing information and determining material condition from previously collected GPR data, assessing the effect of pavement temperature and moisture condition on GPR data and also on managing errors and uncertainty in GPR data. During the EngD project, a number of documents and presentations have been made to publicise the findings both within the EngD sponsoring company (Jacobs) and externally, and an in-house GPR capability has been established within Jacobs as a direct result of the EngD project.

As the capabilities of autonomous vehicles increase, their use in situations that are dangerous or dull for humans is becoming more popular. Autonomous systems are currently being used in several military and civilian domains, including search and rescue operations, disaster relief coordination, infrastructure inspection and surveillance missions. In order to perform high level mission autonomy tasks, a method is required for the vehicle to localize itself, as well as generate a map of the environment. Algorithms which allow the vehicle to concurrently localize and create a map of its surroundings are known as solutions to the Simultaneous Localization and Mapping (SLAM) problem. Certain high level tasks, such as drivability analysis and obstacle avoidance, benefit from the use of a dense map of the environment, and are typically generated with the use of point cloud data. The point cloud data is incorporated into SLAM algorithms with scan registration techniques, which determine the relative transformation between two sufficiently overlapping point clouds. The Normal Distributions Transform (NDT) algorithm is a promising method for scan registration, however many issues with the NDT approach exist, including a poor convergence basin, discontinuities in the NDT cost function, and unreliable pose estimation in sparse, outdoor environments. This thesis presents methods to overcome the shortcomings of the NDT algorithm, in both 2D and 3D scenarios. To improve the convergence basin of NDT for 2D scan registration, the Multi-Scale k-Means NDT (MSKM-NDT) algorithm is presented, which divides a 2D point cloud using k-means clustering and performs the scan registration optimization over multiple scales of clustering. The k-means clustering approach generates fewer Gaussian distributions when compared to the standard NDT algorithm, allowing for evaluation of the cost function across all Gaussian clusters. Cost evaluation across all the clusters guarantees that the optimization will converge, as it resolves the issue of discontinuities in the cost function found in the standard NDT algorithm. Experiments demonstrate that the MSKM-NDT approach can be used to register partially overlapping scans with large initial transformation error, and that the convergence basin of MSKM-NDT is superior to NDT for the same test data. As k-means clustering does not scale well to 3D, the Segmented Greedy Cluster NDT (SGC-NDT) method is proposed as an alternative approach to improve and guarantee convergence using 3D point clouds that contain points corresponding to the ground of the environment. The SGC-NDT algorithm segments the ground points using a Gaussian Process (GP) regression model and performs clustering of the non ground points using a greedy method. The greedy clustering extracts natural features in the environment and generates Gaussian clusters to be used within the NDT framework for scan registration. Segmentation of the ground plane and generation of the Gaussian distributions using natural features results in fewer Gaussian distributions when compared to the standard NDT algorithm. Similar to MSKM-NDT, the cost function can be evaluated across all the clusters in the scan, resulting in a smooth and continuous cost function that guarantees convergence of the optimization. Experiments demonstrate that the SGC-NDT algorithm results in scan registrations with higher accuracy and better convergence properties than other state-of-the-art methods for both urban and forested environments.

Longitudinal joints are one of the critical factors that cause premature pavement failure. Poor-quality joints are characterized by a low density and high permeability; which generates surface distresses such as ravelling or longitudinal cracking. Density has been traditionally considered as the primary performance indicator of joint construction. Density measurements consist of taking cores in the field and determining their density in the laboratory. Although this technique provides the most accurate measure of joint density, it is destructive and time consuming. Nuclear and non-nuclear gauges have been used to evaluate the condition of longitudinal joint non-destructively, but did not show good correlation with core density tests. Consequently, agencies are searching for other non-destructive testing (NDT) options for longitudinal joints evaluation. NDT methods have significantly advanced for the evaluation of pavement structural capacity during the past decade. These methods are based either on deflection or wave velocity measurements. The light weight deflectometer (LWD) is increasingly being used in quality control/quality assurance to provide a rapid determination of the surface modulus. Corresponding backcalculation programs are able to determine the moduli of the different pavement layers; these moduli are input parameters for mechanistic-empirical pavement design. In addition, ultrasonic wave-based methods have been studied for pavement condition evaluation but not developed to the point of practical implementation. The multi-channel analysis of surface waves (MASW) consists of using ultrasonic transducers to measure surface wave velocities in pavements and invert for the moduli of the different layers. In this study, both LWD and MASW were used in the laboratory and in the field to assess the condition of longitudinal joints. LWD tests were performed in the field at different distances from the centreline in order to identify variations of the surface modulus. MASW measurements were conducted across the joint to evaluate its effect on wave velocities, frequency content and attenuation parameters. Improved signal processing techniques were used to analyze the data, such as Fourier Transform, windowing, or discrete wavelet transform. Dispersion curves were computed to determine surface wave velocities and identify the nature of the wave modes propagating through the asphalt pavement. Parameters such as peak-to-peak amplitude or the area of the frequency spectrum were used to compute attenuation curves. A self calibrating technique, called Fourier transmission coefficient (FTC), was used to assess the condition of longitudinal joints while eliminating the variability introduced by the source, receivers and coupling system. A critical component of this project consisted of preparing an asphalt slab with a joint in the middle that would be used for testing in the laboratory. The compaction method was calibrated by preparing fourteen asphalt samples. An exponential correlation was determined between the air void content and the compaction effort applied to the mixture. Using this relationship, an asphalt slab was prepared in two stages to create a joint of medium quality. Nuclear density measurements were performed at different locations on the slab and showed a good agreement with the predicted density gradient across the joint. MASW tests were performed on the asphalt slabs using different coupling systems and receivers. The FTC coefficients showed good consistency from one configuration to another. This result indicates that the undesired variability due to the receivers and the coupling system was reduced by the FTC technique. Therefore, the coefficients were representative of the hot mix asphalt (HMA) condition. A comparison of theoretical and experimental dispersion curves indicated that mainly Lamb waves were generated in the asphalt layer. This new result is in contradiction with the common assumption that the response is governed by surface waves. This result is of critical importance for the analysis of the data since MASW tests have been focusing on the analysis of Rayleigh waves. Deflection measurements in the field with the LWD showed that the surface modulus was mostly affected by the base and subgrade moduli, and could not be used to evaluate the condition of the surface course that contains the longitudinal joints. The LWDmod software should be used to differentiate the pavement layers and backcalculate the modulus of the asphalt layer. Testing should be performed using different plate sizes and dropping heights in order to generate different stress levels at the pavement surface and optimize the accuracy of the backcalculation. Finally, master curves were computed using a predictive equation based on mix design specifications. Moduli measured at different frequencies of excitation with the two NDT techniques were shifted to a design frequency of 25 Hz. Design moduli measured in the field and in the laboratory with the seismic method were in good agreement (less than 0.2% difference). Moreover, a relatively good agreement was found between the moduli measured with the LWD and the MASW method after shifting to the design frequency. In conclusion, LWD and MASW measurements were representative of HMA condition. However, the condition assessment of medium to good quality joints requires better control of the critical parameters, such as the measurement depth for the LWD, or the frequency content generated by the ultrasonic source and the coupling between the receivers and the asphalt surface for the MASW method.