The aim of the thesis is to suggest a comprehensive and inexpensive method of diagnosing the solar cell quality via a conventional digital camera. The following questions are answered, Can a conventionaldigital camera be used for diagnosing the quality of solar cells?; If so,is the experimental setup for the quality diagnosing constrained to a laboratory and single solar cells or can it be done in a private home for a full-sized solar panel?; What are the defects that can be observed in this experiment? A conventional digital camera has been modified to acquire the electroluminescence (EL) images and dark thermography(RevEL) images. The experiment has been done in two locations with different types of samples. Multi-crystalline p-type single solar cells are used during the laboratory experiment. In the experiment set up at the private home, a conventional solar panel with 36 quadraturemulti crystalline silicon solar cells, that are equivalent to 9 full solarcells, is used. The EL imaging has been performed under the forward bias whereas the dark thermography imaging has been performed under reverse bias. The contrast in EL images is due to the radiativeand non-radiative recombination of injected excess minority charge carriers. A large non-radiative recombination site produces a large dark area in the EL image. Similarly, the contrast in RevEL images is due to the generation of charge carriers that are associated with the non-radiative recombination sites in the depletion layer. A large defect area produces a large bright area in the RevEL image. Hence,the EL image and the RevEL image are some what inverted images of each other. It is also found that the IV characteristics and the semi-log curves are in a good agreement with the EL and the RevEL images. When the EL image is combined with the hand-on devices like a mobile camera and a macro lens, it reveals defected areas like finger-interruptions, microcracks, grain boundaries and planar defects. Whereas the RevEL images, when combined with the image processing software tool, reveal the morphology of the defected sites. This justifies the beauty and the simplicity of using an every day digitalcamera as a diagnostic tool for the quality control of the solar cell

Hintergrund: Im Rahmen intrakranieller Operationen kann die intraoperative Darstellung der Gehirndurchblutung die intraoperative Entscheidungsfindung unterstützen. Eine Alternative zu den etablierten Methoden der fluoreszenzgestützten Techniken und der Duplex-Sonographie stellt die intraoperative Perfusionsbildgebung auf Grundlage der Thermographie dar. Hiermit wird die temperaturabhängige, infrarote Strahlung des Gehirns gemessen, die annehmbar abhängig von der zerebralen Perfusion ist. Das Verfahren vereint die Vorteile des nebenwirkungsarmen, kontaktlosen, wiederholten und ökonomischen Einsatzes mit einem verhältnismäßig geringen apparativen Aufwand. Fragestellung/Hypothese: In der vorliegenden Arbeit sollen die intraoperativen Temperaturvariationen des Kortex thermographisch untersucht werden. Durch die intravenöse Applikation eines kalten Flüssigkeitsbolus kann ein systemischer Kältereiz erzeugt werden, der als thermographisches Kontrastmittel agiert. Die Untersuchung der Sensitivität der kortikalen Kältesignalerfassung in Abhängigkeit der Injektionsparameter des Flüssigkeitsbolus und anderer intraoperativer Variablen soll für die Etablierung eines robusten und klinisch nutzbaren Messaufbaus genutzt werden. Die gewonnenen Informationen sollen darüber hinaus zur Entwicklung eines Auswertungsalgorithmus für die automatisierte, thermographische Erfassung des kortikalen Kältesignals dienen. Abschließend werden potenzielle, klinische Anwendungsszenarien beschrieben. Material und Methoden: Die thermographischen Aufnahmen wurden mit ungekühlten Focal-Plane-Array-Kameras mit einer thermischen Auflösung von bis zu 20 mK durchgeführt. Es wurden 97 Patienten intraoperativ untersucht und insgesamt 210 Kältebolusinjektionen appliziert. Die zugrundeliegenden Pathologien waren größtenteils Glioblastome und zerebrale Metastasen sowie Gliome II°/III°, Hirninfarkte, arteriovenöse Malformationen und Aneurysmen. Nach chirurgischer Exposition des zerebralen Kortex wurde die thermographische Messung des Kortex gestartet. Es folgte die intravenöse Injektion der Kälteboli mit einer Temperatur von etwa 4°C aus physiologischer Kochsalzlösung und einem Volumen von 20 ml (59 % der Fälle) oder 50 ml (41 % der Fälle) über einen peripheren (76 % der Fälle) oder zentralen Venenkatheter (24 % der Fälle). Es wurden die Injektionsgeschwindigkeit und Vitalparameter registriert. Nachfolgend wurden die thermographischen Sequenzen einer Datenvorverarbeitung unterzogen, um das Signal-Rausch-Verhältnis zu verbessern. Es folgte die Auswertung der resultierenden Temperatur-Zeit-Reihen zur Kältesignaldetektion mit der Hauptkomponentenanalyse nach Steiner et al., dem Bigauss-Algorithmus nach Hollmach und einer manuellen Analyse (Steiner et al., 2011; Hollmach, 2016). Die Qualität der Auswertungsalgorithmen wurden auf Basis von 10 parallelen Kältebolus-ICG-Injektionen überprüft. Die ICG-Signale wurden als Referenz für die Kältesignaldetektionen genutzt. Die Beschreibung der Kältesignale erfolgte anhand der Parameter twash-in, tmin(T), trise, ttransit und ΔT. Ergebnisse: Die Thermographie kann kleinste Temperaturvariation des Kortex von bis zu 20 mK aufzeichnen. Periodische Temperaturänderungen können zum Teil durch physiologische Prozesse wie Atmung und Herzaktion erklärt werden, während andere spontane Temperaturschwankungen bisher keinen pathophysiologischen Äquivalenten zugewiesen werden können. Das systemische Kältesignal in Form des intravenösen Kältebolus kann bei der kortikalen Passage thermographisch als Temperatursenke registriert werden. Die Sensitivität der Kältesignalerfassung wird wesentlich durch die Injektionsparameter Bolusvolumen, Applikationsort und -geschwindigkeit bestimmt und lässt sich durch eine periphervenöse, 50 ml umfassende Bolusinjektion mit einer Geschwindigkeit von ≥ 5,4 ml/s auf über 70 % steigern. Die Vitalparameter beeinflussen die Kältesignaldetektion nicht. Die Validierung der Kältesignaldetektionen mittels paralleler Kältebolus-ICG-Injektionen offenbarte, dass die präexistenten Auswertungsalgorithmen der Hauptkomponentenanalyse und des Bigauss-Algorithmus eine hohe Sensitivität von 90 % hinsichtlich anteilig richtig-positiver Kältesignaldetektionen erzielen. Jedoch wurden in 90 % der Referenzfälle falsch-positive Kältesignale erkannt, sodass eine geringe Spezifität und ein geringer positiv-prädiktiver Wert resultiert. Beide Algorithmen weisen eine hohe Fehleranfälligkeit auf und sind ungeeignet, um intraoperativ das systemische Kältesignal zuverlässig zu erfassen. Aus den gewonnenen Erkenntnissen der manuellen Analyse der ICG-Kältebolus-Referenzfälle konnte der optimierte AKE-Auswertungsalgorithmus (Automatisierte Kältesignaldetektion nach Empirischem Vorwissen) entwickelt werden. Der AKE-Algorithmus besitzt in den Referenzfällen eine Sensitivität von 100 % und eine qualitativ deutlich verbesserte Spezifität. Der AKE-Algorithmus ist in der Lage, im intraoperativen Einsatz die Kältesignale innerhalb weniger Minuten nach der Kältebolusinjektion zuverlässig in Form zweidimensionaler Parameterkarten zu visualisieren. Auf Basis des AKE-Algorithmus wurden die Kältesignalerfassungen in verschiedenen intrakraniellen Pathologien untersucht. Die Kältesignalparameter in Glioblastomen präsentieren neben einer großen Heterogenität eine durchschnittlich erhöhte Perfusion im Vergleich zum peritumoralen Gewebe in Form einer verminderten twash-in und einer erhöhten ttransit. Jedoch ist eine Identifizierung der Tumorgrenzen anhand der Kältesignaldetektionen nicht möglich, weil die Kältesignalparameter intra- und peritumoralen Gewebes nicht signifikant differieren. Bei der thermographischen Untersuchung maligner Hirninfarkte können die Infarktkerne bereits als hypotherme Kortexregionen und durch eine negative Kältesignaldetektion erfasst werden. Kollateralkreisläufe werden registriert und die Kältesignalparameter korrelieren mit dem postoperativen NIHSS. Die Kältesignalerfassung gelingt zunehmend im Übergang von CT-morphologisch demarkierten zu nicht-demarkierten Hirnarealen und zeigt begleitend eine kürzere twash-in. Damit besteht potenziell die Möglichkeit, in weiteren Untersuchungen die Penumbra zu untersuchen und prognostische Informationen zu gewinnen. Die Kältesignalerkennung bei AVMs konnte sicher erfolgen und die Perfusion der pathologischen Gefäßanteile nachweisen. Somit kann die Thermographie die vollständige Ausschaltung oberflächlicher AVMs unterstützen und ist des Weiteren in der Lage, die Perfusion des umgebenden Parenchyms zu beurteilen. Ebenso kann die Kältesignaldetektion bei der Operation von Aneurysmen zur Erfolgskontrolle und zur Erfassung Clip-bedingter kortikaler Minderperfusionen dienen. Schlussfolgerungen: Die thermographische Detektion eines systemischen Kältereizes ist möglich und kann intraoperativ zusätzliche Informationen generieren, die in operative Entscheidungen oder wissenschaftliche Untersuchungen einfließen können. Um einen robusten und zuverlässigen, intraoperativen Einsatz der thermographischen Kältesignaldetektion zu ermöglichen, sollten zukünftig ausschließlich 50 ml Boli, periphervenöse Injektionen und eine Injektionsgeschwindigkeit ≥ 5,4 ml/s verwendet werden. Für eine schnelle und zuverlässige, intraoperative Ergebnisgenerierung und -darstellung sollte der AKE-Algorithmus bevorzugt werden. Die thermographische Kältesignaldetektion eignet sich insbesondere für die Untersuchung primär vaskulärer Pathologien, wie Hirninfarkte, AVMs oder Aneurysmen.:Inhaltsverzeichnis A Abbildungsverzeichnis B Tabellenverzeichnis C Abkürzungsverzeichnis 1 Einleitung 2 Medizinische Grundlagen 2.1 Präoperative Bildgebung in der Neurochirurgie 2.1.1 Konventionelles MRT, CT und Angiographie 2.1.1 Dynamisch-funktionelle MRT-Sequenzen 2.1.2 Neuronavigation 2.2 Intraoperative Bildgebung zur zerebralen Perfusionsvisualisierung 2.2.1 Fluoreszenzgestützte Techniken 2.2.2 Ultraschall 3 Thermographie 3.1 Physikalische Grundlagen 3.2 Anwendung der Thermographie in der Medizin 4 Zielstellung 5 Material und Methoden 5.1 Thermographische Messung 5.1.1 Messaufbau 5.1.2 Messinstrumentarium 5.1.3 Ablauf der Kältebolus-Messung 5.1.4 Simultane Erfassung des Infrarot- und ICG-Signals 5.2 Methoden der Datenverarbeitung 5.2.1 Vorverarbeitung der Daten 5.2.2 Hauptkomponentenanalyse 5.2.3 Bigauss-Algorithmus 5.3 Auswahl des Patientenkollektivs 6 Ergebnisse 6.1 Patientenkollektiv 6.2 Ergebnisse der Hauptkomponentenanalyse 6.3 Ergebnisse des Bigauss-Algorithmus 6.4 Manuelle Analyse und ICG-Fälle 6.4.1 Schlussfolgerungen der manuell analysierten ICG-Kälteboli 6.4.2 Ergebnisse aller manuell analysierten Kälteboli 6.5 Entwicklung des AKE-Algorithmus 6.6 Ergebnisse des AKE-Algorithmus 6.6.1 Allgemeine Kälteboluscharakteristik 6.6.2 Kältesignalparameter in Abhängigkeit der Injektionsparameter 6.6.3 Kältesignaldetektion als interpathologischer Vergleich 6.6.4 Kältesignaldetektion als intrapathologische Analyse 7 Diskussion 7.1 Vergleich der Verfahren der Kältesignaldetektion 7.2 Einflussfaktoren 7.2.1 Vitalparameter 7.2.2 Injektionsparameter 7.3 Bedeutung der Kältesignalparameter 7.4 Potential der Kältebolusdetektion in Pathologien mittels AKE-Algorithmus 7.4.1 Glioblastom 7.4.2 Maligner Hirninfarkt 7.4.3 Neurovaskuläre Pathologien 7.5 Thesen 8 Zusammenfassung / Summary 9 Literaturverzeichnis 10 Danksagung 11 Anlage 1 12 Anlage 2 / Background: In intracranial surgery, intraoperative imaging of cerebral blood flow can support intraoperative decision making. An alternative to established methods of fluorescence-based techniques and duplex sonography is intraoperative perfusion imaging based on thermography. It receives temperature-dependent, infrared radiation, which depends on cerebral perfusion. Thermography combines the advantages of low-side-effects, contactless, repeated and economical use with a relatively low outlay on equipment. Objective/Hypothesis: In the present work the intraoperative temperature variations of the cortex are to be examined thermographically. The intravenous application of a cold fluid bolus creates a systemic cold stimulus that acts as a thermographic contrast agent. By examining the sensitivity of the cortical cold signal acquisition depending on the injection parameters of the fluid bolus and other intraoperative variables, a robust and clinically usable measurement setup is to be established. The information obtained should also be used to develop an evaluation algorithm for the automated, thermographic detection of the cortical cold signal. Finally, potential clinical application scenarios are described. Material and Methods: The thermographic recordings were made with uncooled focal plane array cameras with a thermal resolution of up to 20 mK. 97 patients were examined intraoperatively and a total of 210 cold bolus injections were administered. The underlying pathologies were mostly glioblastomas and cerebral metastases as well as gliomas II° / III°, brain infarctions, arteriovenous malformations and aneurysms. After surgical exposure of the cerebral cortex, the thermographic measurement of the cortex was started. This was followed by intravenous injection of the cold 0,9% saline boluses with a temperature of about 4 °C and a volume of 20 ml (59% of cases) or 50 ml (41% of cases) via a peripheral (76% of cases) or central venous line (24% of cases). The injection rate and vital parameters were registered. The thermographic sequences were subsequently subjected to data preprocessing in order to improve the signal-to-noise ratio. The resulting temperature-time series are evaluated to find cold signals using the principal component analysis according to Steiner et al., the Bigauss algorithm according to Hollmach and a manual analysis (Steiner et al., 2011; Hollmach, 2016). The results were checked based on 10 parallel cold bolus ICG injections. The ICG signals were used as a reference for the cold signal detection. The cold signals were described by the parameters twash-in, tmin(T), trise, ttransit and ΔT. Results: Thermography can record smallest temperature variations of the cortex up to 20 mK. Periodic changes in temperature can be explained in part by physiological processes such as breathing and heart rate, while other spontaneous temperature fluctuations cannot yet be assigned to any pathophysiological equivalents. The systemic cold signal in the form of the intravenous cold bolus can be thermographically registered as a temperature drop during the cortical passage. The sensitivity of the cold signal detection is essentially determined by the injection parameters bolus volume, injection site and injection rate. It can be increased to more than 70% with a peripheral venous line, 50 ml bolus volume and an injection rate of ≥ 5.4 ml/s. The vital parameters do not influence the cold signal detection. The validation of the cold signal detection using parallel cold bolus and ICG injections revealed that the pre-existent evaluation algorithms of the principal component analysis and the Bigauss algorithm achieve a high sensitivity of 90 % with regard to proportionally correct-positive cold signal detection. However, false-positive cold signals were detected in 90% of the reference cases, resulting in low specificity and low positive-predictive value. Both algorithms are highly susceptible to errors and are unsuitable for reliably detection of the systemic cold signal intraoperatively. From the knowledge obtained from the manual analysis of the ICG - cold bolus reference cases, the optimized AKE evaluation algorithm (Automated Cold signal detection based on Empirical prior knowledge) was developed. In the reference cases, the AKE algorithm has a sensitivity of 100% and a qualitatively significantly improved specificity. The AKE algorithm is able to reliably visualize the cold signals in two-dimensional parameter maps within a few minutes after the cold bolus injection during intraoperative use. Based on the AKE algorithm, the cold signal recordings in various intracranial pathologies were examined. The cold signal parameters of glioblastomas showed a high degree of heterogeneity and on average an increased cerebral perfusion by reduced twash-in and increased ttransit compared to peritumoral tissue. However, an identification of the tumour borders based on the cold signal detection is not possible because the cold signal parameters of intra- and peritumoral tissue do not differ significantly. In the thermographic examination of malignant brain infarctions, the infarct cores can be detected as hypothermic cortex regions and by negative cold signal detection. Collateral circuits are registered thermographically and the cold signal parameters correlate with the postoperative NIHSS. The cold signal acquisition succeeds increasingly in the transition from CT-morphologically infarcted to non-infarcted brain areas and shows a smaller twash-in. Therefore, the cold bolus detection has the potential to investigate the penumbra and to obtain prognostic information. Cold signal detection in AVMs was carried out safely and the perfusion of the pathological vessels were demonstrated. Thus, thermography can support the complete elimination of superficial AVMs and is also able to assess the perfusion of the surrounding parenchyma. Cold signal detection can also be used in the operation of aneurysms to monitor complete elimination and clipping-related cerebral perfusion changes. Conclusions: The thermographic detection of the systemic cold stimulus is possible and can generate additional information intraoperatively, which can be incorporated into intraoperative decision making or scientific studies. In order to enable robust and reliable, intraoperative use of thermographic cold signal detection, further cold bolus examinations should be standardized with intravenous injection of 50 ml boluses via peripheral venous line and an injection rate ≥ 5.4 ml/s. The AKE algorithm should be preferred for fast and reliable, intraoperative result generation. Thermographic cold signal detection is particularly suitable for the investigation of primarily vascular pathologies such as brain infarctions, AVMs or aneurysms.:Inhaltsverzeichnis A Abbildungsverzeichnis B Tabellenverzeichnis C Abkürzungsverzeichnis 1 Einleitung 2 Medizinische Grundlagen 2.1 Präoperative Bildgebung in der Neurochirurgie 2.1.1 Konventionelles MRT, CT und Angiographie 2.1.1 Dynamisch-funktionelle MRT-Sequenzen 2.1.2 Neuronavigation 2.2 Intraoperative Bildgebung zur zerebralen Perfusionsvisualisierung 2.2.1 Fluoreszenzgestützte Techniken 2.2.2 Ultraschall 3 Thermographie 3.1 Physikalische Grundlagen 3.2 Anwendung der Thermographie in der Medizin 4 Zielstellung 5 Material und Methoden 5.1 Thermographische Messung 5.1.1 Messaufbau 5.1.2 Messinstrumentarium 5.1.3 Ablauf der Kältebolus-Messung 5.1.4 Simultane Erfassung des Infrarot- und ICG-Signals 5.2 Methoden der Datenverarbeitung 5.2.1 Vorverarbeitung der Daten 5.2.2 Hauptkomponentenanalyse 5.2.3 Bigauss-Algorithmus 5.3 Auswahl des Patientenkollektivs 6 Ergebnisse 6.1 Patientenkollektiv 6.2 Ergebnisse der Hauptkomponentenanalyse 6.3 Ergebnisse des Bigauss-Algorithmus 6.4 Manuelle Analyse und ICG-Fälle 6.4.1 Schlussfolgerungen der manuell analysierten ICG-Kälteboli 6.4.2 Ergebnisse aller manuell analysierten Kälteboli 6.5 Entwicklung des AKE-Algorithmus 6.6 Ergebnisse des AKE-Algorithmus 6.6.1 Allgemeine Kälteboluscharakteristik 6.6.2 Kältesignalparameter in Abhängigkeit der Injektionsparameter 6.6.3 Kältesignaldetektion als interpathologischer Vergleich 6.6.4 Kältesignaldetektion als intrapathologische Analyse 7 Diskussion 7.1 Vergleich der Verfahren der Kältesignaldetektion 7.2 Einflussfaktoren 7.2.1 Vitalparameter 7.2.2 Injektionsparameter 7.3 Bedeutung der Kältesignalparameter 7.4 Potential der Kältebolusdetektion in Pathologien mittels AKE-Algorithmus 7.4.1 Glioblastom 7.4.2 Maligner Hirninfarkt 7.4.3 Neurovaskuläre Pathologien 7.5 Thesen 8 Zusammenfassung / Summary 9 Literaturverzeichnis 10 Danksagung 11 Anlage 1 12 Anlage 2

Lorsqu'une structure est soumise à un chargement thermique hétérogène, des dilatations empêchées génératrices de contraintes surviennent. Lorsque ces sollicitations sont répétées un grand nombre de fois, un endommagement puis une fissuration du matériau peuvent apparaître. On parle alors de fatigue thermique du matériau. Ce phénomène, jugé responsable de différents incidents rencontrés dans les zones de mélange entre fluides chaud et froid des centrales nucléaires a fait l'objet de nombreuses études lancées au sein de projets successifs pilotés par EDF. Ces études portaient sur la détermination des chargements thermo-hydrauliques dans les zones de mélange, le transfert de chaleur à la structure, la résolution du problème thermomécanique permettant de connaître les champs de contrainte et de déformation en tout point de la structure et enfin la résistance du matériau (un acier inoxydable austénitique AISI 304L)soumis à de telles sollicitations. Concernant ce dernier aspect, plusieurs types d'essais ont été réalisés : d'une part, des essais de fatigue uniaxiaux et isothermes pour construire une courbe de fatigue mécanique du matériau et, d'autre part, des essais sur plusieurs dispositifs expérimentaux de fatigue thermique développés au sein d'organismes de recherche (CEA, EDF, JRC, JAEA,…) pour s'approcher des conditions de service. L'interprétation de ces derniers essais passe par l'estimation des champs de température et de déplacement dans la structure à partir de quelques mesures ponctuelles de température par thermocouples. On constate alors que les premières fissures s'amorcent en fatigue thermique pour un nombre de cycles sensiblement inférieur à celui estimé à partir des courbes de fatigue mécanique du matériau et de l'amplitude maximale de déformation équivalente estimée dans les essais de fatigue thermique. L'objet de ce travail de thèse consiste donc à concevoir et à réaliser des chocs thermiques sur un matériau de structure couplés à des mesures synchrones et sans contact de champs de température et de déplacement au niveau de la surface endommagée. Les chocs thermiques seront réalisés à l'aide d'un laser de puissance dont la longueur d'onde sort du spectre utilisé par la caméra infrarouge qui mesure le champ de température de surface de telle manière que le dépôt d'énergie n'affecte pas les mesures de température. Plusieurs pistes sont envisagées selon que les champs sont mesurés uniquement avec la caméra infrarouge ou en utilisant deux caméras, l'une travaillant dans l'infrarouge et l'autre dans le visible. Dans les deux cas de figure, l'absorptivité et l'émissivité de la surface soumise au choc thermique doivent être optimisées pour permettre d'avoir à la fois un dépôt d'énergie homogène par laser et une mesure précise des champs thermomécaniques. Une difficulté qu'il conviendra de surmonter est d'obtenir un champ d'émissivité de surface représentant un compromis acceptable entre une émissivité forte et homogène dans l'infrarouge pour des mesures de température et une émissivité hétérogène (dans l'infrarouge ou le visible selon la caméra utilisée) pour créer un contraste de niveau de gris indispensable aux mesures de déplacement par corrélation d'images. Parallèlement aux essais,des simulations numériques thermomécaniques seront également réalisées pour compléter ces champs en volume et tester l'influence des conditions aux limites. L'objectif final de la thèse est d'obtenir pour la première fois une mesure fiable des quantités d'intérêt dans une zone d'amorçage en fatigue thermique et ainsi pouvoir quantifier convenablement un éventuel effet aggravant des sollicitations de fatigue thermique. / Thermal fatigue occurs in nuclear power plant pipes. The temperature variations are due to the turbulent mixing of fluids that have different temperatures. Many experimental setups have been designed but the measured temperatures have only been punctual and out of the zone of interest (e.g., via thermocouples). The equivalent strain variation in the crack initiation region is calculated with numerical thermomechanical simulations. In many cases, the comparisons between numerical and experimental results have shown that the crack initiation predictions in thermal fatigue are non-conservative. A new testing setup is proposed where thermal shocks are applied with a pulsed laser beam while the thermal and kinematic fields on the specimen surface are measured with infrared (IR) and visible cameras, respectively. Experimental testings are performed and different measurement techniques for temperature and kinematic fields are used. IR camera and pyrometers allow to measure the temperature variations in the zone impacted by the laser beam. To estimate the absolute temperature, the surface emissivities at the respective wavelengths are determined by different methods. The absolute temperature field is then used to apply the actual thermal loading in a decoupled FE model after an identification process of the parameters of the laser beam. Once the thermal loading is generated based upon the experimental data, the stress and strain fields can be computed in the region of interest with an elastoplastic law.The experimental strain variations calculated from the DIC measurements are compared with the predictions obtained with the FE simulation.

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Aspekte zur klinischen Anwendung der Infrarot-Thermographie in der Zoo- und Wildtiermedizin. Die Infrarot-Thermographie ist eine nichtinvasive Methode. Mit einer Infrarot-Kamera wird eine Messung der Körperoberflächen-Temperatur aus der Distanz durchgeführt und das Thermoprofil des Tieres als Thermogramm dargestellt. Es bedarf keines direkten Tierkontaktes und keiner Immobilisation. Viele Fallbeispiele belegen, dass die Infrarot-Thermographie eine erfolgversprechende neue Methode in der Zoo- und Wildtiermedizin ist. Schwerpunkte der Arbeit waren: - Erforschung artspezifischer Thermoregulation, besonders im Hinblick auf Tierhaltung und krankheitsauslösende Faktprem bei Zoo- und Wildtieren, - Reproduktionsforschung mittels Infrarot-Thermographie und - Entzündungsdiagnostik mittels Infrarot-Thermographie. Die meisten hier vorgestellten Ergebnisse sind Erstuntersuchungen weltweit. / Aspects of the clinical application of Infrared-Thermography in Zoo- and Wildlife Medicine Infrared-thermography is a non-invasive method. With an infrared-camera, the body surface temperature of an animal is measured from a distance and the thermoprofile of this animal is then displayed as a therogram. No direct animal contact or immobilization is necessary. Many case reports show that infrared-thermography is a promising new method in zoo and wildlife medicine. In this thesis threee topics are emphasized: - research in species-specific thermoregulation with regard to animal keeping and disease predisposing factors, - research in reproduction using infrared-thermography, and - inflammation diagnosis using infrared-thermography. Most of the presented results are from primary investigations worldwide.

[pt] A termografia infravermelha tem sido usada como uma técnica de avaliação não destrutiva para detectar falhas nos componentes estruturais, desempenhando um papel importante nos programas de inspeção de fabricação, inspeção em serviço e manutenção. Um programa de investigação foi lançado com o objetivo de apresentar combinações de métodos analíticos, experimentais e numéricos para prever e monitorar o início da fadiga e a progressão dos danos à fadiga em equipamentos como vasos de pressão, tanques, tubulações e dutos com mossas ou anomalias complexas. O monitoramento do início e propagação da fadiga nas amostras reais utilizou técnicas de inspeção por infravermelho não destrutivo. Análise termoelástica de tensão (TSA), correlação tridimensional de imagem digital (3D-DIC) e strain gages de fibra óptica Bragg (FBSG) foram utilizados para determinar deformações em locais de fadiga em pontos críticos. Os campos de deformação determinados a partir das medições experimentais e do método de elementos finitos (MEF) foram combinados com a equação de vida-de-fadiga de Coffin-Manson e a regra de dano por fadiga de Miner para prever a vida de fadiga (N). Os resultados das amostras tubulares testadas de 3 m de comprimento contendo mossas de formato complexo foram relatados e analisados completamente. Este trabalho confirmou que os métodos infravermelhos de avaliação rápida de fadiga são ferramentas práticas e eficientes que podem fornecer resultados confiáveis, não destrutivos e rápidos acerca do comportamento à fadiga dos materiais. Uma boa concordância entre as estimativas de vida em fadiga e a vida real de mossas com geometria complexas em dutos só pode ser atingida se medições precisas ou determinações numéricas das deformações circunferenciais que atuam nos pontos de interesse forem acopladas a curvas de fadiga deformação-vida adequadas. Acoplando uma técnica experimental para determinar com precisão a geometria das mossas com uma técnica de análise numérica de deformações fará com que sejam obtidas boas estimativas de deformação das posições críticas que serão combinadas com as curvas de fadiga baseadas na relação deformação-vida. As presentes conclusões podem ser aplicadas a outras estruturas que podem apresentar mossas, como tanques e vasos de pressão. / [en] Infrared thermography has been used as a nondestructive evaluation (NDE) technique to detect flaws in structural components, playing an important role in manufacturing inspection, in-service inspection and maintenance programs. An investigation program was launched with the objective of presenting combinations of analytical, experimental and numerical methods to predict and monitor fatigue initiation and fatigue damage progression in equipment such as pressure vessels, tanks, piping and pipelines with dents or complex-shaped anomalies. The monitoring of fatigue initiation and propagation in the actual specimens used nondestructive inspection techniques such as thermoelastic stress analysis (TSA), three-dimensional digital image correlation (3D-DIC) and fiber optic Bragg strain gages (FBSG) to determine strains at fatigue hot spots locations. Strain fields determined from the experimental measurements and from the finite element method (FEM) were combined with the fatigue Coffin-Manson strain-life equation and the Miner s fatigue damage rule to predict fatigue life (N). Results from tested 3m long tubular (with nominal dimensions: 324mm external diameter and 6.35mm wall thickness) specimens containing complex-shaped dents were reported and fully analyzed. This work confirmed that infrared rapid fatigue assessment methods are practical and efficient tools that can provide a reliable, non-destructive and faster results about the fatigue behavior of materials. Good agreement among fatigue life estimations and actual fatigue lives of complex dent shapes in pipeline specimens can only be achieved if accurate measurements or numerical eterminations of the circumferential strains actuating at the dent hot-spots were coupled with suitable fatigue strain-life curves. Coupling an experimental technique for accurately determining dent shapes to a numerical strain analysis technique will lead to good hot-spot strain estimations to be combined with the strain-life fatigue curves. The present conclusions can be applied to other structures that may present dents such as tanks and pressure vessels.

[pt] O presente trabalho introduz duas técnicas de medição da emissividade da superfície de três materias comumente utilizados nas plataformas offshore: cobertura de Thermal Sprayed Aluminum (TSA), cobertura de Jotatemp1000 e uma superfície crua de aço naval. Foram investigadas metodologias de medição de emissividade e os conceitos básicos de radiação e convecção natural. A partir disso, determina-se a modelagem do problema em questão para as estimativas de calor e emissividade. O primeiro experimento consistiu na medição da emissividade com o auxílio de um termógrafo, nesse foi realizada a comparação de medição sobre uma placa plana e um tubo revestido para o TSA e o Jotatemp1000. No segundo experimento, realizou-se a medição da emissividade através da medição das transferencias de calor por convecção natural e radiação em um espaço anular. As medições neste experimento foram realizadas para diferentes pressões, para que se quantifique o efeito da convecção natural. No primeiro experimento, nota-se uma discrepância significativa entre os valores medidos nos tubos e nas placas. Constatou-se também que a emissividade de todos os materiais permaneceu praticamente constante para os valores acima de 100 Graus C. Observou-se uma disparidade considerável nos valores de emissividade encontradas no primeiro experimento em comparação com o segundo para o Jotatemp e aço naval. A partir dos dados, constata-se que emissividade medida com termógrafo possui uma precisão maior, por ser uma medida direta. Dentre as medições no espaço anular, o mais confiável para pequenos intervalos de temperatura é a parametrização pela superfície dada pelo matlab. Ainda que os resultados apresentem tais discrepâncias, pode-se observar que o Jotatemp100 obteve os maiores valores de emissividade em todos os experimentos e o TSA os menores valores, mesmo com a incerteza experimental. / [en] The present work introduces two techniques for measuring the surface emissivity of three materials commonly used in offshore platforms: Thermal Sprayed Aluminum (TSA) coating, Jotatemp1000 coating and a raw marine steel surface. Emissivity measurement methodologies and the basic concepts of radiation and natural convection were investigated. From this, the modeling of the problem in question for the heat and emissivity estimates is determined. The first experiment consisted of measuring the emissivity with the aid of a thermographic camera, in which the measurement comparison was performed on a flat plate and a coated tube for TSA and Jotatemp1000. In the second experiment, emissivity was measured by gauging heat transfers by natural convection and radiation in an annular space. The measurements in this experiment were carried out for different pressures, in order to quantify the effect of natural convection. In the first experiment, there was a significant discrepancy between the values measured in the tubes and in the plates. It was also found that the emissivity of all materials remained practically constant for values above 100 C Degrees. A considerable disparity was observed in the emissivity values found in the first experiment compared to the second for Jotatemp and marine steel. From the data, is verified that emissivity measured with a thermographic camera has greater precision, as it is a direct measure. Among the measurements in the annular space, the most reliable for small temperature intervals is the surface parameterization given by matlab. Although the results show such discrepancies, it can be observed that Jotatemp100 obtained the highest emissivity values in all experiments and the TSA the lowest values, even with experimental uncertainty.

The use of infrared thermography for boundary layer detection was evaluated for use in the Cal Poly Low Speed Wind Tunnel (LSWT) and recommendations for the successful use of this technique were developed. In cooperation with Joby Aviation, an infinite wing model was designed, manufactured and tested for use in the LSWT. The wing was designed around a custom airfoil profile specific for this project, where the nearly-flat pressure gradient at a zero pitch angle would delay the chordwise onset of boundary layer transition. Steady-state, RANS numerical simulations predicted the onset of transition to occur at 0.75 x/c for the design Reynolds Number condition of 6.25x105. The wing was manufactured from 3D printed aluminum, with a wall thickness of 0.125 inches and a chord length of 13.78 inches. Two central rows of static pressure taps were used, each with 12 functional chordwise locations. The taps were able to generate strong correlation to the numerically predicted pressure coefficient distribution. The use of an infrared camera visualized and confirmed the presence of boundary layer transition at the chordline location anticipated by the early simulations. To do so, the model was pre-heated such that the differential cooling properties of laminar and turbulent flow would generate a clear temperature gradient on the surface correlating to boundary layer transition. Adjustment of the model’s pitch angle demonstrated a change in the onset location of boundary layer transition during the infrared testing. The change of onset location was seen to move forward along the chordline as the aerodynamic angle of attack was increased. Testing with a Preston Tube system allowed for the interpolation of local skin friction coefficient values at each static tap location. Application of both laminar and turbulent empirical assumptions, when compared to numerical expectations, allowed for the qualitative assessment of boundary layer transition onset. Overall, the wing model developed for this research proved capable of producing quality and repetitive results for the experimental goals it was designed to meet. The model will next be used in continued tests which will further explore the use of infrared thermography.

The goal of the research conducted for this master's thesis is to understand if active thermography is a suitable technique to detect (identify) and measure (approximate depth and or size) defects in additive manufacturing (AM) processes. Although other non-destructive measurement techniques exist, active thermography is an attractive option for AM applications because of the short measurement times that could be implemented between each layer of a print, and because of the relatively inexpensive equipment required. However, pulse thermography is typically applied to detect larger defects (>1 mm) in materials with high thermal conductivity. It was uncertain if active thermography was sensitive enough to detect the small defects (μm) commonly introduced during AM. Defects of this size are common in AM, and their presence significantly impacts the mechanical properties of the final part. For this reason, the detection limits of active thermography in common AM materials were investigated. Numerical models were created to simulate the heat transfer during active thermography in AM structures (polymer and stainless steel) with defects of varying size. The models included non-ideal conditions such as spectral in-depth absorption of the irradiative pulse and free convection from the object's surface. The spectral properties of acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), and polyamide 12 (PA 12) were measured (see chapter 2) and used in the numerical models. The numerical data indicates that active thermography is sensitive enough to detect the existence of defects smaller than 100 μm in AM materials (see chapter 3). Furthermore, it demonstrates that the defect aspect ratio (defect diameter divided by defect depth) for which traditional 1D thermography models may be used to approximate the depth of defects in 3D systems is approximately 6 (see chapter 4). In addition, the depth of defects with lower aspect ratios (~4) may also be approximated with relatively low error (~10% error). Non-ideal systems (those with convection and spectral in-depth absorption) were simulated, and figures are provided which facilitate the approximation of defect depth using simple, ideal thermography models. Active thermography has shown potential as being an efficient technique for detecting and measuring small defects common in AM.