Disertační práce se zabývala vlivem adheze mezi vláknovým (FRC) a částicovým (PFC) kompozitem a složením obou komponent na mechanické vlastnosti a způsob porušování modelových bi-materiálových kompozitních těles při statickém namáhání. Zkoumán byl také vliv způsobu přípravy bi-materiálového kompozitního tělesa na pevnost adheze mezi jeho kompozitními komponentami. K hodnocení mechanických vlastností bi-materiálových PFC/FRC těles byl použit jak 3 tak 4-bodový ohybový test za pokojové teploty a relativní vlhkosti 70%. Modifikovaný vytrhávací test byl použit k měření smykové pevnosti adheze mezi vláknovým a částicovým kompozitem. Tyto výsledky byly korelovány s výsledky ze strukturní a fraktografické analýzy (TGA, SEM). Experimentální data byla poté analyzována pomocí existujících mikromechanických modelů a byl nalezen vztah mezi tuhostí modelových bi-materiálových těles, složením a geometrií uspořádání jejich komponent a pevností adheze mezi těmito komponentami. Na základě těchto výsledků byl navržen optimální způsob vrstvení a přípravy PFC/FRC bimateriálových těles. Navržené postupy byly použity k přípravě a pre-klinickým testům nosných konstrukcí zubních můstků.

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Auf der Basis der Bemessungsgrundlagen (DAfStb-Richtlinie „Stahlfaserbeton“, DBV-Merkblatt „Stahlfaserbeton“ und DIN 1045-1) wurden ausgewählte Bauteilversuche mit entsprechenden rechnerischen Überprüfungen der experimentell ermittelten Ergebnisse durchgeführt. Die Untersuchungen konzentrierten sich auf die Ermittlung der Effizienz von ausgewählten Stahlfasern in Betonen mit und ohne Betonstahlbewehrung in durch Biegung ohne Längskraft belasteten Versuchskörpern unter Betrachtung der Grenzzustände der Gebrauchstauglichkeit (GZG) und Tragfähigkeit (GZT). Das Versuchsprogramms umfasste neben der Prüfung ausgewählter Frischbetoneigenschaften die Bestimmung von Festbetonparametern an standardisierten Probekörpern. Des Weiteren wurden 4-Punkt-Biegezugversuche an Balken mit den Abmessungen l/h/b = 70/15/15 cm aus reinem Stahlfaserbeton sowie stahlfaserbewehrtem Stahlbeton, in Anlehnung an das DBV-Merkblatt „Stahlfaserbeton“ und die Richtlinie „Stahlfaserbeton“ vom DAfStb, durchgeführt. Aufbauend auf den Erkenntnissen aus den Materialversuchen im Labormaßstab wurden anschließend Untersuchungen an großformatigen Biegebalken (l/h/b = 420/40/20 cm) durchgeführt. Im Weiteren erfolgten Prüfungen und Auswertungen von Einzelfaserausziehversuchen mit ausgewählten Stahldrahtfasern in Verbindung mit Betonen unterschiedlicher Druckfestigkeit unter Berücksichtigung des Einflusses der Einbindelänge sowie des Einbindewinkels. Im Rahmen des Versuchsprogramms wurden die auf der Grundlage der 4-Punkt-Biegezugversuche ermittelten Ergebnisse analysiert und mit dem derzeit gültigen Bemessungsmodell nach DAfStb-Richtlinie „Stahlfaserbeton“ rechnerisch überprüft. Auf der Basis dieser Ergebnisse erfolgte die Entwicklung eines Ansatzes zur Optimierung der bestehenden Bemessungsansätze. Gegenstand dieser Forschungsarbeit war ebenfalls die Entwicklung eines Fasermodells, mit dem man auf der Grundlage des eingesetzten Fasergehaltes und der Faserart Rückschlüsse auf die Faseranzahl in einer rechteckigen Bruchfläche ziehen kann. Hierbei wurde ein Modell für Rechteckquerschnitte entwickelt, welches es ermöglicht, die durchschnittliche Faseranzahl in einer Bruchfläche, auf der Basis vereinfachter Annahmen, abzuschätzen. Die Verifizierung des Modells erfolgte durch den Vergleich der errechneten Faseranzahl mit zahlreichen experimentellen Versuchsergebnissen. Im letzten Abschnitt dieser Arbeit wurde die Herleitung bzw. Generierung von Bemessungshilfsmitteln zur Biegebemessung von Stahlfaserbeton mit und ohne Betonstahlbewehrung behandelt. Die Ausführungen beziehen sich dabei auf dimensionslose Bemessungstafeln und Interaktionsdiagrammen für Rechteckquerschnitte.

Internal combustion engines are used in many applications. The same engine type may have different components mounted to it depending upon its use. These engine mounted components need to be designed against fatigue in order to withstand the engine vibrations. Measured engine vibrations are commonly used as input data for fatigue estimation. The focus in this thesis is set on heavy-duty diesel engines, typically used in trucks, buses and industrial applications. All of the appended papers use engine vibration measurements to evaluate the proposed methods. In Paper A, the engine block motion is described with a seven degree of freedom kinematic model. These degrees of freedom consist of six rigid body modes and one assumed twisting degree of freedom. With this description, measured engine block vibrations can be used to accurately predict the vibration in positions that have not been measured. Relating the measured vibrations of an engine mounted component with the projected motion of the engine block at that same position, makes it possible to identify local dynamic phenomena. In Paper B, the kinematic model of Paper A is extended with three assumed bending deformation mode shapes. For the current engine type, all of the assumed deformation modes are ranked within the 10-300 Hz frequency range. The deformation mode of highest importance is the engine block twist. Including bending deformation increases the accuracy of the engine block vibration description but it also increases the demands on instrumentation. In Paper C, the possibility to modify measured engine vibration signals, for addition or removal of engine mounted components, is investigated. For this purpose, engine vibration measurements were performed with and without a 29 kg brake air compressor mounted to the engine. For the task of removing the effect that this engine mounted component has on the engine block, the two cases of knowing, and not knowing the vibration of the component are both considered. The proposed methodology successfully predicts the changes in engine vibration due to system modification. The proposed method can also be used to estimate the time response of a component's centre of gravity. In this study the component's dynamic properties are derived from measurements but they could also be produced using finite element analysis. This can be useful early in the design process to find critically stressed areas due to base excitation. / <p>QC 20171222</p>

Aerospace research for next-generation travel increasingly focuses on the use of advanced composites to reduce weight and cost while retaining strength. One subset of materials with great potential is based on the combination of resin matrix and glass-fiber reinforcement. This research explores the application of a candidate nanopaper coating with a given composite. Prior research applied a set of given heat fluxes to the top surface of the composite for a set of given periods of time, and subsequently performed a 3-point flexural test to determine the elastic modulus for both the coated and uncoated composite for all of the combinations of heat flux and time. A finite element (FE) model is developed using the ANSYS general purpose finite element analysis (FEA) software that models the degradation in strength/stiffness properties based on heating condition and with the goal of predicting cracking using the element death feature in ANSYS. This thesis describes the prior research suggesting both the need for and novelty of this model, and the procedures used to form the model. The loading conditions of the 3-point flexural test are replicated, and four measures of accuracy are developed based on the force versus displacement curve of the test and the FE model. It is envisioned that continuum-level models developed as a part of these research be applied for design of next-generation space components These measurements are used to verify the FE model, and this model is then employed to extrapolate beyond the context of experimental conditions.

Combining the most recent technologies in concrete, Ultra-High-Performance Fibre-Reinforced Concrete (UHPFRC) arises as a promising material for the near future. UHPFRC have shown how flexible concrete can be to adapt to the ever-changing social and environmental demands. With its high flexibility composition and its mechanical properties, UHPFRC is full of both unexplored and unexploited possibilities. Engineers should take responsibility for this task. However, it is fair to acknowledge that this is not an easy task and it requires the development of reliable and widely accepted design standards provided by the scientific community. A major concern about durability, long-lasting structures and reduction of maintenance cost, as well as the development of new concrete technologies, improved knowledge of fibre effect and a huge growth in the fibre industry accompanied by fibre price reduction have led, among other factors, to the development of new types of concrete whose mechanical behaviour substantially differs from conventional fibre-reinforced concrete. This is why current characterisation methodologies and design standards must be reviewed and adjusted to these newer materials. However, design standard revision cannot disregard former milestones achieved thanks to decades of hard work. It must offer an integrated view in which new types of concrete comprise existing ones in a broader group, because at the end of the day and despite having newer and improved properties, new types of concrete are still concrete. That is how it should be understood and how it must be reflected in newer codes and standards. The work presented herein is focused on one of these recently developed materials that embraces major advanced technologies in concrete: Ultra-High-Performance Fibre-Reinforced Concrete (UHPFRC). This work is specifically focused on those crucial requirements for the development and widespread use of it, such as constitutive tensile characterisation and classification. This work includes a deep revision of the uniaxial tensile behaviour of concrete and its development as fibre technology has evolved. In addition, traditional characterisation standard methods as well as those recently developed for its specific use on UHPFRC are reviewed and called into question. Throughout the document, the development of different methodologies to determine the uniaxial constitutive tensile behaviour of UHPFRC from bending tests are shown, together with a simplified characterisation proposal specially developed for being included in a standard. All developed methodologies presented herein are checked and validated. These methods are specifically designed for their application on experimental results obtained from a special type of four-point bending test, whose standardisation proposal for UHPFRC is also shown. Finally, a classification proposal is presented as a function of more relevant UHPFRC tensile parameters necessary for design that can be directly obtained from the standard characterisation test method suggested. Proposed classification encompasses the existing classification for conventional reinforced and fibre-reinforced concrete. In it, both plain concrete and fibre-reinforced concrete are presented as a particular case of a more general tensile constitutive response for concrete. Standard methodology and classification proposed are in accordance with the evolution of concrete and unify historic milestones achieved by the international research community. / El Hormigón de Muy Alto Rendimiento (HMAR) combina los últimos avances tecnológicos en hormigón y se erige como un material prometedor para el futuro. El HMAR ha demostrado su gran capacidad para adaptarse a las cada vez más exigentes demandas sociales y medioambientales. Con un gran abanico de posibilidades en su dosificación para conseguir las propiedades mecánicas deseadas, el HMAR es un material lleno de posibilidades aún sin explorar y sin explotar. Los ingenieros tienen la responsabilidad de esta tarea. Sin embargo, es justo reconocer que no se trata de una tarea fácil y que requiere de un desarrollo previo de códigos de diseño adecuados y ampliamente aceptados por parte de la comunidad científica. La aparición de nuevas tecnologías, el mayor conocimiento sobre la aportación de las fibras así como su industrialización y bajada de precios, las mayores preocupaciones sobre la durabilidad estructural, incremento de la vida útil o la reducción de los costes de mantenimiento, entre otros factores, han derivado en el desarrollo de nuevas tipologías de hormigones cuyo comportamiento mecánico difiere de manera sustancial de los tradicionales hormigones con fibras. Es por ello que tanto la readaptación de las metodologías de caracterización como las metodologías de diseño deben ser reformuladas. Y esto debe hacerse de manera no disruptiva, es decir, manteniendo la línea de los hitos alcanzados en los hormigones con fibras convencionales de manera que queden integrados en metodologías de caracterización y de diseño que los engloben, porque al fin y al cabo, y aunque con nuevas y mejores propiedades mecánicas, los nuevos hormigones siguen siendo hormigones. Así debe ser entendido y así debe quedar reflejado en las nuevas normativas. El presente trabajo se centra en uno de esos nuevos materiales desarrollados con el avance de las nuevas tecnologías como es el HMAR. En especial, este documento se centra en ese aspecto tan fundamental para el desarrollo de nuevos hormigones como es la caracterización mecánica y la tipificación. Este trabajo incluye una revisión del comportamiento mecánico uniaxial a tracción del hormigón y de su evolución con la aparición de las diferentes tecnologías. Además, se revisan y se ponen en cuestión los sistemas tradicionales de caracterización, así como los nuevos sistemas desarrollados en los últimos años para su empleo específico en el HMAR. A lo largo del documento se desarrollan diferentes metodologías para la obtención del comportamiento constitutivo a tracción del HMAR, así como la propuesta de una metdología simplificada de caracterización especialmente diseñada para ser incluida en una norma, todas ellas debidamente validadas. Estas metodologías son de aplicación específica a los resultados experimentales obtenidos mediante un ensayo a cuatro puntos sin entalla, cuya propuesta de estandarización para el HMAR ha sido también desarrollada. Finalmente, se presenta una propuesta de tipificación de acuerdo a los parámetros más relevantes del comportamiento a tracción del HMAR que son necesarios para el diseño y que pueden ser directamente obtenidos del ensayo de caracterización propuesto. Esta clasificación engloba a la clasificación existente para el hormigón armado convencional y los actuales hormigones con fibras, de manera que se presenta la actual definición de hormigón con fibras como un caso particular de estos nuevos hormigones, respetando al máximo la evolución de este material y aunando los logros conseguidos por la comunidad científica. / Dins de les combinacions de les tecnologies més recents en el formigó, el formigó de molt alt rendiment (UHPFRC) sorgeix com un material prometedor per al futur pròxim. L'UHPFRC ha demostrat poder ser un formigó flexible per adaptar-se a les sempre canviants demandes socials i mediambientals. Amb una gran flexibilitat en la seua composició i les seues propietats mecàniques, l`UHPFRC està ple de possibilitats de ser explorades i explotades. Els enginyers han de prendre la responsabilitat d'aquesta tasca. No obstant això, és just reconèixer que això no serà fàcil i requerirà el desenvolupament de normes de disseny fiables i àmpliament acceptades per la comunitat científica. Hi ha una gran preocupació al voltant de la durabilitat, la vida útil de les estructures i la reducció del cost de manteniment, juntament amb el desenvolupament de noves tecnologies de formigó, un millor coneixement de l'efecte de la fibra i un enorme creixement en la indústria de la fibra acompanyat per la reducció del preu de la fibra, han conduït, entre altres factors, al desenvolupament de nous tipus de formigons, el comportament mecànic dels quals es diferencia substancialment dels formigons reforçats amb fibres convencionals. És per això que les metodologies de caracterització actuals i les normes de disseny han de ser revisades i ajustades a aquests nous materials. No obstant això, la revisió del codis de disseny no pot prescindir de les antigues fites aconseguides gràcies a dècades de treball dur. S'ha d'oferir una visió integrada en la qual els nous tipus de formigons integren els ja existents en un grup més ampli, ja que, al cap i la fi i malgrat tenir propietats noves i millorades, els nous tipus de formigons són encara un tipus de formigó. Així es com s'hauria d'entendre i reflectir-se en els nous codis i normes. El treball presentat en aquest document es centra en un d'aquests materials que s'han desenvolupat recentment i que abasta les principals tecnologies avançades en el formigó: el Formigó de Molt Alt Rendiment Reforçat amb Fibres (UHPFRC). Aquest treball se centra específicament en els requisits fonamentals per al desenvolupament i l'ús generalitzat d'aquest, com ara la caracterització i classificació del comportament constitutiu a tracció. Aquest treball inclou una revisió profunda del comportament a tracció uniaxial del formigó i els seus canvis al temps que la tecnologia de les fibres ha evolucionat. A més, els mètodes tradicionals estàndard de caracterització, així com els recentment desenvolupats per al seu ús específic en l'UHPFRC són revisats i qüestionats. Al llarg del document, es mostra el desenvolupament de diferents metodologies per a determinar el comportament constitutiu a tracció uniaxial de l'UHPFRC, juntament amb una proposta de caracterització simplificada especialment desenvolupada per poder ser inclosa en normativa. Totes les metodologies desenvolupades presentades en aquest document han estat comprovades i validades. Aquests mètodes estan dissenyats específicament per a la seva aplicació en els resultats experimentals obtinguts a partir d'un tipus especial d'assaig de flexió a quatre punts, a més també s'inclou una proposta d'estandardització per a l'UHPFRC. Finalment, es presenta una proposta de classificació en funció dels paràmetres més rellevants del comportament a tracció de l'UHPFRC que són necessaris per al disseny i que es poden obtindre directament del mètode d'assaig estàndard suggerit per a la caracterització de l'UHPFRC. La classificació proposada té amb compte la classificació existent per al formigó armat convencional i el reforçat amb fibres. En ella, tant el formigó en massa com el formigó reforçat amb fibres es presenten com un cas particular d'una resposta constitutiva a tracció més general per al formigó. La metodologia estàndard i la classificació proposada estan d'acord amb l'evolució de formigó i unifica l / López Martínez, JÁ. (2017). CHARACTERISATION OF THE TENSILE BEHAVIOUR OF UHPFRC BY MEANS OF FOUR-POINT BENDING TESTS [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/79740

Presented in this work are the results of twelve flexural tests conducted on small-scale coupons to establish the load-deflection behavior of UNS S32003 (ATI 2003®) hot-rolled duplex stainless steel flat plates. All specimens were tested as simply supported beams loaded at the midspan. Test specimens had nominal width and thickness of 1 in. and 0.25 in., respectively. Four different span lengths of 4 in., 6 in., 9 in., and 12 in. were investigated. Analysis of the results showed that the non-linear deflection behavior can be estimated reasonably well by adopting the conventional deflection equation pertaining to an assumed linear elastic material, but after replacing the modulus of elasticity with a secant modulus corresponding to the maximum tension strain resulting from the applied load.

Intensive competition on the global market puts great pressure on manufacturing companies to develop and produce products that meet requirements from customers and investors. One key factor in meeting these requirements is the efficiency of the product development and the production preparation process. Design automation is a powerful tool to increase efficiency in these two processes. The benefits of automating the production preparation process are shortened led-time, improved product performance, and ultimately decreased cost. Further, automation is beneficial as it increases the ability to adapt products to new product specifications with production preparations done in few or in a single step. During the automation process, knowledge about the production preparation process is collected and stored in central systems, thus allowing full control over the design of production equipments. Three main topics are addressed in this thesis: the flexibility of design automation systems, knowledge bases containing conflicting rules, and the automation of the finite element analysis process. These three topics are discussed in connection with the production preparation process of rotary draw bending. One conclusion drawn from the research is that it is possible to apply the concept of design automation to the production preparation process at different levels of automation depending on characteristics of the implemented knowledge. In order to make design automation systems as flexible as possible, the concept of object orientation should be adapted when building the knowledge base and when building the products geometrical representations. It is possible to automate the process of setting up, running, and interpreting finite element analyses to a great extent and making the automated finite element analysis process a part of the global design automation system.

This study investigates the mechanical differences between old and newly produced slatted floors through a four-point bending test. To understand to what extent the actual environment has affected the slatted floors, the carbonation depth and corrosion will be examined. The tests showed no mechanical differences between slatted floors which had been in service for a certain amount of years and newly produces ones. Corrosion could be observed on some of the samples but it was not because of the carbonation process. When comparing the calculations of reinforced and pre-stressed concrete slatted floors, the result showed that the pre-stressed floor could carry up to double the load of what the reinforced slatted floor could. The conclusion of this study is, that the pre-stressed slatted floors will certainly hold for at least thirty years and will most likely hold for many years to come.

Carbon fabric-reinforced polymer (CFRP) composites are widely used in aerospace, automotive and construction structures thanks to their high specific strength and stiffness. They can also be used in various products in sports industry. Such products can be exposed to different in-service conditions such as large bending deformations caused by quasi-static and dynamic loading. Composite materials subjected to such bending loads can demonstrate various damage modes - matrix cracking, delamination and, ultimately, fabric fracture. Damage evolution in composites affects both their in-service properties and performance that can deteriorate with time. Such damage modes need adequate means of analysis and investigation, the major approaches being experimental characterisation and numerical simulations. This work deals with a deformation behaviour and damage in carbon fabric-reinforced polymer (CFRP) laminates caused by quasi-static and dynamic bending. Experimental tests are carried out first to characterise the behaviour of a CFRP material under tension, in-plane shear and large-deflection bending in quasi-static conditions. The dynamic behaviour of these materials under large-deflection bending is characterised by Izod-type impact tests employing a pendulum-type impactor. A series of impact tests is performed on the material at various impact energy levels up to its fracture, to obtain a transient response of the woven CFRP laminate. Microstructural examination of damage is carried out by optical microscopy and X-ray micro computed tomography (Micro-CT). The damage analysis revealed that through thickness matrix cracking, inter-ply delaminations, intra-ply delamination such as tow debonding, and fabric fracture was the prominent damage modes. These mechanical tests and microstructural studies are accompanied by advanced numerical models developed in a commercial code Abaqus. Among those models are (i) 2D FE models to simulate experimentally observed inter-ply delamination, intra-ply fabric fracture and their subsequent interaction under quasi-static bending conditions and (ii) 3D FE models based on multi-body dynamics used to analyse interacting damage mechanisms in CFRP under large-deflection dynamic bending conditions. In these models, multiple layers of bilinear cohesive-zone elements are placed at the damage locations identified in the Micro CT study. Initiation and progression of inter-laminar delamination and intra-laminar ply fracture are studied by employing cohesive elements. Stress-based criteria are used for damage initiation while fracture-mechanics techniques are employed to capture its progression in composite laminates. The developed numerical models are capable to simulate the studied damage mechanisms as well as their subsequent interaction observed in the tests and microstructural damage analysis. In this study, a novel damage modelling technique based on the cohesive-zone method is proposed for analysis of interaction of various damage modes, which is more efficient than the continuum damage mechanics approach for coupling between failure modes. It was observed that the damage formation in the specimens was from the front to the back at the impact location in the large-deflection impact tests, unlike the back-to-front one in drop-weight tests. The obtained results of simulations showed a good agreement with experimental data, thus demonstrating that the proposed methodology can be used for simulations of discrete damage mechanisms and their interaction during the ultimate fracture of composites in bending. The main outcome of this thesis is a comprehensive experimental and numerical analysis of the deformation and fracture behaviours of CFRP composites under large-deflection bending caused by quasi-static and dynamic loadings. Recommendations on further research developments are also suggested.