Strain and dynamic measurements using fiber optic sensors embedded into graphite/epoxy tubes

Graphite/epoxy tubes were fabricated with embedded optical fibers to evaluate the feasibility of monitoring strains with a fiber optic technique. Resistance strain gauges were attached to the tubes to measure strain at four locations along the tube for comparison with the fiber optic sensors. Both static and dynamic strain measurements were made with excellent agreement between the embedded fiber optic strain sensor and the strain gauges. Strain measurements of 10(exp -7) can be detected with the optical phase locked loop (OPLL) system using optical fiber. Because of their light weight, compatibility with composites, immunity to electromagnetic interference, and based on the static and dynamic results obtained, fiber optic sensors embedded in composites may be useful as the sensing component of smart structures

フィラメントワインディングプロセスの最適制御系の設計と実装化に関する研究

豊橋技術科学大学200

A Tesla-Blumlein PFL-Bipolar pulsed power generator

A Tesla-Blumlein PFL-Bipolar pulsed power generator, has been successfully designed, manufactured and demonstrated. The compact Tesla transformer that it employs has successfully charged capacitive loads to peak voltages up to 0.6 MV with an overall energy efficiency in excess of 90%. The Tesla driven Blumlein PFL generator is capable of producing a voltage impulse approaching 0.6 MV with a rise time close to 2 ns, generating a peak electrical power of up to 10 GW for 5 ns when connected to a 30 Ω resistive load. Potentially for medical application, a bipolar former has been designed and successfully implemented as an extension to the system and to enable the generation of a sinusoid-like voltage impulse with a peak-to-peak value reaching 650 kV and having a frequency bandwidth beyond 1 GHz. This thesis describes the application of various numerical techniques used to design a successful generator, such as filamentary modelling, electrostatic and transient (PSpice) circuit analysis, and Computer Simulation Technology (CST) simulation. All the major parameters of both the Tesla transformer, the Blumlein pulse forming line and the bipolar former were determined, enabling accurate modelling of the overall unit to be performed. The wide bandwidth and ultrafast embedded sensors used to monitor the dynamic characteristics of the overall system are also presented. Experimental results obtained during this major experimental programme are compared with theoretical predictions and the way ahead towards connecting to an antenna for medical application is considered

Dipole magnets above 20 tesla: Research needs for a path via high-temperature superconducting rebco conductors

To enable the physics research that continues to deepen our understanding of the Universe, future circular colliders will require a critical and unique instrument—magnets that can generate a dipole field of 20 T and above. However, today’s maturing magnet technology for low-temperature superconductors (Nb-Ti and Nb3 Sn) can lead to a maximum dipole field of around 16 T. High-temperature superconductors such as REBCO can, in principle, generate higher dipole fields but significant challenges exist for both conductor and magnet technology. To address these challenges, several critical research needs, including direct needs on instrumentation and measurements, are identified to push for the maximum dipole fields a REBCO accelerator magnet can generate. We discuss the research needs by reviewing the current results and outlining the perspectives for future technology development, followed by a brief update on the status of the technology development at Lawrence Berkeley National Laboratory. We present a roadmap for the next decade to develop 20 T-class REBCO accelerator magnets as an enabling instrument for future energy-frontier accelerator complex

Encapsulating soldered electronic components for electronically functional yarn

E-Textiles are fabrics with embedded electronic functions that can be used in many fields, such as clothing, medicine, furniture, safety and many others. The integration of electronics with textiles requires a flexible structure that keeps the garment flexible to ensure the textile retains its physical characteristics and feel. E-textiles in wearable applications are subject to human activities. The integrated electronic components are vulnerable to these stresses, such as bending, torsion, and tensile. These forces can potentially damage the components or their interconnection. Electronics can be integrated into textiles in one of three approaches described as generations of E-Textiles. The Thesis will introduce the three generations of E-textiles through a comprehensive literature review in chapter 2. It will then discuss developing the electronically functional yarn (EFY) as a third generation in E-textiles and garments. The production process of this yarn has three main steps: soldering the semi-conductor on the copper wire, encapsulating it within a micro pod of resin, and covering the micro pod within the filament of the yarn. A detailed study of the encapsulation process and the unit's design is then introduced in the Thesis, where a novel method for packaging electronics using a UV-curable resin was introduced. The design process for the automated encapsulation of soldered semi-conductor has been investigated in Chapter 3 of this Thesis. The novel approach has been evaluated on various electronics and then extended to thin Kapton strips with embedded electronics. The resulting EFY then can be later used in woven or knitted textile. Finite element analysis (FEA) of the soldered semi-conductor on the wire is presented in chapter 4. FEA simulations are used to evaluate the mechanical performance of different electronics and how stresses are distributed after adding the resin and creating the micro pod. This FEA investigation of the materials and micro pod dimensions will understand the packaging method's reliability. The final part of the Thesis included further development added to the design of the encapsulation unit and the electronically functional yarn manufacturing. Developing a reliable, repeatable, and automated electronic packaging method for electronics embedded in the electronically functional yarn (EFY) was achieved in this project. The results were promising for further research

Hybrid Optical Fiber Sensors for Smart Materials and Structures

There has been a rapid growth in the use of advanced composite materials in a variety of load-bearing structures, for example in aviation for structures such as rotor blades, aircraft fuselage and wing structures. Composite materials embedded with fiber-optic sensors (FOS) have been recognized as one of the prominent enabling technologies for smart materials and structures. The rapid increase in the interest in composite materials embedded with FOS has been driven by numerous applications, such as intelligent composite manufacturing/processing, and safety-related areas in aircrafts. Research has been focused recently on using several optical sensor types working together to form so called “hybrid optical fiber sensors” in order to overcome the limitations of the individual sensor technologies. The main aim of the research described in this thesis is to investigate a hybrid sensing scheme that utilizes polarimetric sensors and FBG sensors working in a complimentary fashion to measure multiple physical parameters in a composite material, with a particular focus on measuring the complex indirect parameters thermal expansion and vibration. The research described in this thesis investigates the performance of a hybrid sensing scheme based on polarimetric sensors and FBG sensors after embedding in a composite material. It is shown that the influence of thermal expansion within a composite material on embedded polarimetric sensors is the main source of errors for embedded fiber sensor strain measurements and that for practical strain sensing applications buffer coated PM-PCF are more suitable for embedding in composite. Further, using a buffer stripped PM-PCF polarimetric sensor, a measurement scheme to measure a composite material\u27s thermal elongation induced strain is proposed. A novel hybrid sensor for simultaneous measurement of strain, temperature and thermal strain is demonstrated by integrating polarimetric sensors based on acrylate coated high bi-refringent polarization maintaining photonic crystal fiber (HB-PM-PCF), and a coating stripped HB-PM-PCF sensor together with an FBG sensor. Flexible demodulation modules that can be embedded or surface attached is a challenge for composite materials containing fiber-optic sensors. In this thesis an interrogation method that allows intensity domain operation of hybrid sensor is demonstrated. Further focusing towards the miniaturization of the hybrid sensor interrogator, a miniaturized flexible interrogator for the demonstrated hybrid sensing scheme embedded in a composite material is also designed. Low frequency vibration measurements are performed for glass fibre-reinforced composite material samples with two different strain-sensitive polarimetric sensor types embedded. It is shown that the strain sensitivity of polarimetric sensors limits the vibration measurements to a certain range of vibration amplitudes. A polarimetric sensor based buffer stripped HB-PM-PCF is demonstrated for monitoring the different stages of the curing process for a Mageneto-Rheological composite material. By providing information about multiple parameters such as strain, temperature, thermal strain, vibration amplitude and vibration frequency the proposed and demonstrated hybrid sensing approach has a high potential to change the paradigm for smart material design in the future

Study of oil/pressboard progressive creeping discharge under highly divergent electric field

As one of the most dangerous failure modes of transformers, the oil/pressboard progressive creeping discharge, as well as the corresponding insulation failure mechanisms, have thus far not been fully understood. The present thesis aims to gain a sound fundamental knowledge of the progressive creeping discharge, their influential factors, and the relevant failure mechanisms, as well as to contribute to an effective monitoring and diagnostic methodology. This study explored the progressive creeping discharges under highly divergent AC and DC voltages, respectively. The tests conditions were configured to investigate the impacts of critical influential factors, including ageing, voltage level, temperature, stress waveform, and oil flowing, on creeping discharges. The discharge processes were systematically evaluated using tools such as partial discharge, gas analysis, temperature monitoring, and finite-element simulation. Comparative analyses and theoretical examinations were made to the insulation faults as well as their correlated physicochemical phenomena. A conventional techniques-based monitoring framework was proposed for the dangerous creeping discharges, and the applicability of a new detection technique based on synchronous PD and dielectric measurements was tested as well. The characteristics of damage-free AC progressive creeping discharge, as well as the influences of pressboard ageing and field intensity, were investigated. It was found the progressive creeping discharge is a compound discharge that comprises mainly oil corona discharge and surface discharge. Pressboard ageing affected the discharge inception but had no influence on the interface breakdown strength. The damage-free discharge exhibited a constant PRPD pattern but had a diminishing PD intensity, where the pressboard ageing and voltage level jointly determine whether the discharges can be sustained or not. The damage-free discharge generated hydrogen principally and was located between D1/ D2 fault zones in the classical Duval’s Triangle. The insulation failures due to dangerous creeping discharges were comparatively studied. It was found the AC progressive creeping discharge could generate two faults to the pressboard, i.e., internal treeing (internal treeing) and surface tracking (surface tracking). The faults exhibited distinct electrical as well as physicochemical characteristics, and their occurrences were subject to pressboard ageing, voltage level, and pressboard density. A four-staged model was proposed to illustrate the development of internal treeing. The model highlighted the central role of the filament-like carbonization tracks in the pressboard interior, of which the onset and growth were theoretically expounded as well. A detection methodology was proposed for internal treeing, which was mainly based on continuous PD measurement, online temperature monitoring, and gas analysis. However, it was found still hard to detect a severe surface tracking fault due to the PD disappearance. The influences of temperature and voltage waveforms on AC progressive creeping discharge were studied. Temperature affected the short-time electric strength of either interface or oil gap and could form a synergistic effect with a strong field in exacerbating the dissipation factor of pressboard. Moreover, it was found temperature can determine the fault types and discharge severity under either constant or step-wise stress, whereas the stress waveform had an obvious effect on the fault type only at high temperatures. Depending on the test temperature and stress waveforms, the test specimens failed due to tracking-free interface flashover, surface tracking, and internal treeing, respectively. Their PD quantities were comparatively evaluated. Moreover, it was found the synchronous PD and dielectric measurement is highly indicative of the internal treeing process, and it exhibited both high detection sensitivity and discharge identification capability. The DC progressive creeping discharge was evaluated against temperatures and forced oil flows. Temperature affected the DC conductivity of both oil and pressboard, the resistivity ratio of pressboard to oil, and the oil/pressboard interface charge relaxation time. Accordingly, the interface field distributions were evaluated against temperatures using the finite-element method. Moreover, both oil flow speed and temperatures affected the short-time DC interface electric strength as well as the progressive creeping discharge. Two types of discharges were found under static oil condition. They exhibited distinct PD characteristics and showed different responses to temperature changes. They were presumably associated with discharges in oil and pressboard, respectively. Furthermore, it was found that forced oil flows can alter the behaviors of DC creeping discharges drastically and generated a peculiar PD type (Pulse Train). The occurrence of the pulse train was subject to applied voltage level, temperature, and oil flowing velocity. A theoretical model was proposed to elucidate the pulse train, in which the interactions between space charges from different sources were discussed against voltage levels, oil flows, and temperatures. The present thesis extends the knowledge of the oil/pressboard progressive creeping discharges. The research results are expected to serve as a base for future scientific studies and a piece of reference information for practical applications pertinent to progressive creeping discharges.Eine der gefährlichsten Fehlerarten in Transformatoren, die fortschreitende Kriechentladung in Öl/Feststoff Anordnungen sowie der dazugehörige Mechanismus des Isolationsfehlers sind noch nicht völlig geklärt. Die vorliegende Arbeit zielt auf die Erreichung einer soliden fundamentalen Kenntnis der fortschreitenden Kriechentladung, ihrer Einflussfaktoren und der entsprechenden Fehlermechanismen ab. Weiterhin soll sie einen Beitrag zur effektiven Überwachung und diagnostischen Methoden liefern. Die Untersuchungen beinhalten die fortschreitenden Kriechentladungen bei stark inhomogenen elektrischen Feldern unter Wechsel- und Gleichspannung. Die Versuchsbedingungen wurden so konfiguriert, dass die Wirkung der kritischen Einflussfaktoren auf die Kriechentladungen wie Alterung, Höhe der Spannung, Temperatur, Beanspruchungsform und Ölfluss, untersucht werden konnte. Die Entladungsvorgänge wurden systematisch ausgewertet unter Verwendung von Methoden wie Teilentladung, Gasanalyse, Temperaturerfassung und Simulation mit Finiten Elementen. Vergleichende Analysen und theoretische Prüfungen wurden im Hinblick auf Isolierungsfehler und der dazugehörigen physio-chemischen Erscheinungen durchgeführt. Ein auf konventioneller Technik basierendes Monitoring Konzept wurde für die gefährlichen Kriechentladungen vorgeschlagen und die Anwendung neuer Detektionstechniken basierend auf synchroner Teilentladungserfassung und dielektrischen Messungen geprüft. Die Eigenschaften von beschädigungsfreien fortschreitenden Kriechentladungen bei Wechsel-spannung und der Einfluss der Alterung des Pressspan sowie der Feldstärke wurden untersucht. Es wurde herausgefunden, dass die fortschreitende Kriechentladung eine zusammengesetzte Entladung ist, bestehend aus Korona-Entladungen in Öl und Oberflächenentladungen. Die Alterung von Pressspan beeinflusst den Einsatz der Entladung aber hat keinen Einfluss auf die Durchschlagsfestigkeit der Grenzfläche. Die beschädigungsfreie Entladung zeigt ein konstantes PRPD Muster aber mit abnehmender Teilentladungs-Aktivität, wobei die Alterung des Pressspans und die Spannungshöhe gemeinsam bestimmen, ob die die Entladungen unterbrochen werden oder nicht. Die beschädigungsfreie Entladung erzeugt grundsätzlich Wasserstoff und ist den Fehlerzonen D1/D2 des klassischen Duval Dreiecks zugeordnet. Die Fehler der Isolierung infolge der gefährlichen Kriechentladungen wurden vergleichend untersucht. Es wurde herausgefunden, dass die fortschreitende Kriechentladung bei Wechselspannung zwei Fehlerarten im Pressspan erzeugen kann, die schnelle Kriechwegbildung (internes Treeing) und die langsame Kriechwegbildung (Oberflächen Kriechweg). Die Fehler weisen deutlich elektrische als auch physio-chemische Eigenschaften auf und ihr Erscheinen war abhängig vom Alterungszustand des Pressspans, Spannungshöhe und Dichte des Pressspans. Ein vierstufiges Modell wurde vorgeschlagen um die Entwicklung der schnellen Kriechwegbildung darzustellen. Das Modell betont die zentrale Rolle der faserähnlichen karbonisierten Kriechwege im Inneren des Pressspans, wobei Einsatz und Wachstum theoretisch erklärt werden. Eine Erkennungsmethode für die Schnelle Kriechwegbildung wurde vorgeschlagen, die im Wesentlichen auf Teilentladungsmessungen, online Temperaturerfassung und Gas Analyse basiert. Es war dennoch schwierig eine langsame Kriechwegbildung zu erfassen, da Teilentladungen verschwanden. Die Einflüsse von Temperatur und Spannungsform auf fortschreitende Kriechwegentladungen wurden untersucht. Die Temperatur beeinflusste die kurzzeitige elektrische Feldstärke der Grenzschicht und der Ölstrecke und kann eine synergetische Auswirkung mit einem starken Feld auslösen, indem sich der Verlustfaktor des Pressspans erhöht. Es wurde weiterhin herausgefunden, dass die Temperatur die Fehlertypen und Entladungsstärke unter konstanter oder stufenweise Beanspruchung beeinflussen kann, wobei die Art der Beanspruchung einen klar erkennbaren Einfluss auf die Fehlerart nur bei hohen Temperaturen hat. Abhängig von der Prüftemperatur und der Beanspruchungsforme versagten die Prüflinge durch Grenzschichtüberschlag ohne Kriechwegspuren, langsame Kriechwegbildung und schnelle Kriechwegbildung. Ihre Teilentladungsgrößen wurden vergleichend ausgewertet. Darüber hinaus wurde herausgefunden, dass synchrone Teilentladungen und dielektrische Messungen eine gute Kennzeichnung für schnelle Kriechwegbildungsprozesse sind und es zeigt die Fähigkeit einer hohen Erkennungsempfindlichkeit und Entladungserkennung. Die fortschreitenden Kriechentladungen bei Gleichspannung wurden in Abhängigkeit der Temperatur und der Ölflussstärke ermittelt. Die Temperatur beeinflusst die Gleichspannungsleitfähigkeit von beiden, Öl und Pressspan, das Widerstandsverhältnis von Pressspan und Öl, und die Relaxationszeit der Grenzschichtladungen Öl/Pressspan. Dementsprechend wurde die Grenzschichtfeldverteilung in Abhängigkeit der Temperatur mit Hilfe der Finite-Elemente Methode ausgewertet. Außerdem beeinflussten die Geschwindigkeit des Ölflusses und die Temperaturen die kurzzeitige Grenzflächenfeldstärke bei Gleichspannung und fortschreitenden Kriechwegentladung. Zwei Arten von Entladungen wurde bei ruhendem Öl gefunden. Sie zeigen deutliche Teilentladungsmerkmale und unterschiedliches Verhalten bei Temperaturänderungen. Sie waren vermutlich verbunden mit Entladungen im Öl und Pressspan. Es wurde weiterhin herausgefunden, dass forcierte Ölströmung das Verhalten der Kriechentladungen bei Gleichspannung drastisch verändert und einen besonderen Typ von Teilentladungen erzeugt (Pulsfolge). Die Erscheinung dieser Pulsfolge war abhängig von der Höhe der angelegten Spannung, der Temperatur und der Geschwindigkeit des Ölflusses. Es wurde ein theoretisches Modell zur Verdeutlichung der Pulsfolge vorgeschlagen, bei dem die Wechselwirkungen zwischen Raumladungen von verschiedenen Quellen behandelt wurden in Abhängigkeit der Spannungshöhe, des Ölflusses und der Temperatur. Die vorliegende Arbeit erweitert die Kenntnis der fortschreitenden Kriechentladungen in der Anordnung Öl/Pressspan. Es wird erwartet, dass die Untersuchungsergebnisse als Basis für zukünftige wissenschaftliche Studien dienen und einen Beitrag mit hinweisenden Informationen für die praktische Anwendung zur Thematik fortschreitender Kriechentladungen liefern

Clean filament winding: industrial site trials and product evaluation

During wet-filament winding, fibre bundles are impregnated using a drum-based resin bath. The impregnated bundles are then directed to a traversing-arm prior to being over-wound onto a rotating mandrel. Once the required number of layers of the impregnated fibres has been deposited on the mandrel, the assembly is transferred to an oven to cure the thermosetting resin. After this, the composite is cooled to ambient temperature and extracted from the mandrel. There are a number of issues with the conventional manufacturing method including the generation of waste resin, utilisation of significant volumes of solvent for cleaning the equipment at the end of each shift, contamination of the factory floor due to resin drips from the impregnated tows and the cost of waste disposal. This thesis reports on the integration of a modified wet-filament winding process, which is referred to as "clean fi lament winding", into an industrial filament winding manufacturing operation. It was demonstrated that the clean filament can be utilised to address the above-mentioned issues associated with the conventional wet-filament winding. For example, an 88.12% and 87.5% reduction in solvent consumption and the generation of waste resin respectively was verified when compared to conventional wet-filament winding. Hence, it can be concluded that the clean filament winding technique is capable of producing industrially relevant filament wound composites with marginally superior or equivalent properties when compared to conventional wet-filament winding. However, the environmental benefits of the clean filament winding technique are significant