Дисертації з теми "Buildings Thermal properties Testing"

The Bridge House is a steel building structure located in Poly Canyon, a rural area inside the campus of California Polytechnic State University, San Luis Obispo. The Bridge House is a one story steel structure supported on 4 concrete piers with a lateral force resisting system (LFRS) composed of ordinary moment frames in the N-S direction and braced frames in the E-W direction and vertically supported by a pair of trusses. The dynamic response of the Bridge House was investigated by means of system identification through ambient and forced vibration testing. Interesting findings such as diaphragm flexibility, foundation flexibility and frequency shifts due to thermal effects were all found throughout the mode shape mapping process. Nine apparent mode shapes were experimentally identified, N-S and E-W translational, rotational and 6 vertical modes. A computational model was also created and refined through correlation with the modal parameters obtained through FVTs. When compared to the experimental results, the computational model estimated the experimentally determined building period within 8% and 10% for both N-S and E-W translational modes and within 10% for 4 of the vertical modes.

Little has been published concerning the thermal properties of existing unbaked earth walls. In order to model the thermal behaviour of a building constructed using traditional cob walls, the thermal conductivity and thermal diffusivity need to be established. The Centre for Earthen Architecture (CEA), based at the University of Plymouth's School of Architecture has carried out research into various aspects of cob architecture typical to the Devon area. This study supplements other work concerning the moisture content, structure and pathology of cob as a building material. This research concentrates upon the development of a time dependent probe technique for the measurement of the thermal conductivity and thermal diffusivity of cob. The literature concerning the technique is reviewed. Methods of obtaining thermal data from the results are discussed. Particular emphasis is placed upon the measurement of the probe's thermal contact conductance with the test material. A series of laboratory tests and results from specific test materials are described. From this work, a link between the improvement of the thermal contact between the probe and the specimen and the accuracy of the thermal diffusivity values is established. The development of field test apparatus is described and the results from three field tests are examined. Values for thermal conductivity, diffusivity and the probe thermal contact conductance are established. These results are used in a thermal simulation of a cob dwelling. The output from the simulation is compared with results from a modern timberframe house of identical dimensions and use. The thermal response of the modern timber-frame house was found to be similar to that of the cob dwelling. However, generally, the range of internal air temperature was found to be higher in the interior spaces of the timber framed dwelling than the cob dwelling.

We are coming to realize that there is an urgent need to reduce energy usage in buildings and it has to be done in a sustainable way. This thesis focuses on the performance of the building envelope; more precisely thermal performance of walls and super insulation material in the form of vacuum insulation. However, the building envelope is just one part of the whole building system, and super insulators have one major flaw: they are easily adversely affected by other problems in the built environment.  Vacuum Insulation Panels are one fresh addition to the arsenal of insulation materials available to the building industry. They are composite material with a core and an enclosure which, as a composite, can reach thermal conductivities as low as 0.004 W/(mK). However, the exceptional performance relies on the barrier material preventing gas permeation, maintaining a near vacuum into the core and a minimized thermal bridge effect from the wrapping of barrier material round the edge of a panel. A serpentine edge is proposed to decrease the heat loss at the edge. Modeling and testing shows a reduction of 60% if a reasonable serpentine edge is used. A diffusion model of permeation through multilayered barrier films with metallization coatings was developed to predict ultimate service life. The model combines numerical calculations with analytical field theory allowing for more precise determination than current models. The results using the proposed model indicate that it is possible to manufacture panels with lifetimes exceeding 50 years with existing manufacturing. Switching from the component scale to the building scale; an approach of integrated testing and modeling is proposed. Four wall types have been tested in a large range of environments with the aim to assess the hygrothermal nature and significance of thermal bridges and air leakages. The test procedure was also examined as a means for a more representative performance indicator than R-value (in USA). The procedure incorporates specific steps exposing the wall to different climate conditions, ranging from cold and dry to hot and humid, with and without a pressure gradient. This study showed that air infiltration alone might decrease the thermal resistance of a residential wall by 15%, more for industrial walls. Results from the research underpin a discussion concerning the importance of a holistic approach to building design if we are to meet the challenge of energy savings and sustainability. Thermal insulation efficiency is a main concept used throughout, and since it measures utilization it is a partial measure of sustainability. It is therefore proposed as a necessary design parameter in addition to a performance indicator when designing building envelopes. The thermal insulation efficiency ranges from below 50% for a wood stud wall poorly designed with incorporated VIP, while an optimized design with VIP placed in an uninterrupted external layer shows an efficiency of 99%, almost perfect. Thermal insulation efficiency reflects the measured wall performance full scale test, thus indicating efficiency under varied environmental loads: heat, moisture and pressure. The building design must be as a system, integrating all the subsystems together to function in concert. New design methodologies must be created along with new, more reliable and comprehensive measuring, testing and integrating procedures. New super insulators are capable of reducing energy usage below zero energy in buildings. It would be a shame to waste them by not taking care of the rest of the system. This thesis details the steps that went into this study and shows how this can be done.
QC 20120228

As electronic packages and their thermal solutions become more complex the reliability margins in the thermal solutions diminish and become less tolerant to errors in reliability predictions. The current method of thermally stress testing thermal solutions can be over or under predicting end of life thermal performance. Benefits of accurate testing and modeling are improved silicon yield in manufacturing, improved performance, lower cost thermal solutions, and shortened test times. The current method of thermally stress testing is to place the entire unit in an elevated isothermal temperature and periodically measure thermal performance. Isothermally aging is not an accurate representation of how the unit will be used by the customer and does not capture the thermal gradients and mechanical stresses due to different coefficients of thermal expansion of the materials used in the thermal solution. A new testing system, CITRAM which is an acronym for Constant Interface Temperature Reliability Method, has been developed that uses an electronic test board. The approach captures the thermal and mechanical stresses accurately and improves test time by 20-30% as a result of automation. Through this study a difference in the two methods has been identified and the new CITRAM method should be adopted as current practice.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.
Includes bibliographical references (leaves 42-43).
A process known as mutational spectrometry allows the detection of both single and multiple mutations that appear to be spontaneous, using a technique known as constant denaturing capillary electrophoresis (CDCE). CDCE requires a region of constant temperature and concentration of denaturant. A massively parallel, fully automated instrument, capable of handling as many as 10,000 DNA samples simultaneously, is suited to this technique. A modular structure of such a mutational spectrometer was designed to remain water-tight, provide an array to hold the capillaries for electrophoretic excitation, and modulate the flow of a heat transfer fluid. Six such modules were manufactured and assembled. As the heat transfer fluid passed through the assembled structure, the natural thermal loss was determined.
by Michael R. Del Zio.
S.B.

Among the many efforts to improve the IC test process are tests that attempt to differentiate between healthy and defective or low reliability ICs by manipulating the operating conditions of the IC being tested. This thesis attempts to improve the common understanding of multiple and targeted temperature testing by evaluating work published on the subject to date and by presenting previously unpublished empirical observations. The empirical observations are made from SCAN and LBIST based MinVDD measurements, Static IDD measurements, as well as parametric measurements of transistor characteristics. The test vehicles used are 0.25μm and 0.18μm CMOS ASICs fabricated by LSI Logic. An IC’s performance is bound by a three dimensional space defined by VDD, frequency, and temperature. A model is presented to explain the boundaries of the performance region in terms of the ability of the IC’s constituent transistors to provide power and the Zero-Temperature-Coefficient (ZTC). Also, it is determined that multiple temperature testing can add new tests to current test suites to improve the resolution between healthy and defective ICs.

At present there are concerns that new housing in the UK under-performs in terms of energy-efficiency. In research studies where the thermal performance of the building fabric has been measured, post-construction, significant gaps between design predictions and the as-built performance of new housing have been found. This thesis is concerned with how thermography may be used to assess the thermal performance of new housing during the construction process. The practical utility of this testing approach, which has not been investigated in-depth by previous research, is to identify performance issues at a stage when undertaking remedial work is less costly and disruptive. Moreover, by identifying issues that could reduce the energy-efficiency of the building fabric, these tests could help address the observed "performance gap". An approach for using thermography at different stages of construction has been developed through practical case studies and experimental work. The complementary use of heat transfer modelling and thermography is also explored. Finally, through interviews with industry professionals, the context of implementing tests within UK housing development practices is examined. The results of applying the testing approach demonstrate that beneficial feedback can be obtained without significant interruption to construction activities. However, test procedures need to be modified according to the stage and method of construction. It is proposed that heat transfer modelling can inform the interpretation of test results and analysis of defect severity. For the testing approach to be implemented more widely, there would need to be further development and trials on different types of construction and the oversight of an independent body to establish its credibility. In conclusion, thermography has the potential alongside other testing and inspection practices to help improve standards of site construction. However, there are limitations to its use which need to be considered if such tests are to be implemented effectively.

Green roofs can be an effective and appealing way to increase the energy efficiency of buildings by providing active insulation. As plants in the green roof transpire, there is a reduction in heat flux that is conducted through the green roof. The R-value, or thermal resistance, of a green roof is an effective measurement of thermal performance because it can be easily included in building energy calculations applicable to many different buildings and situations. The purpose of this study was to determine if an increase in ambient temperature would cause an increase in the R-value of green roofs. Test trays containing green roof materials were tested in a low speed wind tunnel equipped to determine the R-value of the trays. Three different plant species were tested in this study, ryegrass (Lolium perenne), sedum (Sedum hispanicum), and vinca (Vinca minor). For each test in this study the relative humidity was maintained at 45% and the soil was saturated with water. The trays were tested at four different ambient temperatures, ranging from room temperature to 120ºF. The resulting R-values for sedum ranged from 1.37 to 3.28 ft²h°F/BTU, for ryegrass the R-values ranged from 2.15 to 3.62 ft²h°F/BTU, and for vinca the R-values ranged from 3.15 to 5.19 ft²h°F/BTU. The average R-value for all the tests in this study was 3.20 ft²h°F/BTU. The results showed an increase in R-value with increasing temperature. Applying an ANOVA analysis to the data, the relationship between temperature and R-value for all three plant species was found to be statistically significant.

This research consists of experimental load tests and numerical simulations of structural steel connections with various filler materials to study the effect of non-steel fillers on the connection strength. Non-steel fillers are used in the steel connections to provide thermal insulation by reducing thermal bridging. Eight specimens having steel and polypropylene filler plates of various thicknesses were tested in the laboratory. The collected data were compared to a Finite Element Analysis (FEA) using ABAQUS to validate the numerical results. After validation, three parametric studies were conducted using ABAQUS to provide insight into general behavior of connections with a variety of fillers that could be used as thermal breaks. In addition, an extreme case of having air gaps instead of alternative fillers was also considered. The Research Council on Structural Connections (RCSC 2014) suggests a reduction in the bolt shear strength when undeveloped fillers with a thickness of more than 0.25 inch are used while using any non-steel material is prohibited due the limited research available. Most research studies have investigated the mechanical behavior of thermal breaks in either end-plate moment connections or slip-critical connections. No data is available for thermal breaks in bearing-type connections up to failure. This research aims to study the effects of filler material properties such as modulus of elasticity and strength on bolt strength, as well as investigate whether the current equation in RCSC 2014 is applicable for alternative filler materials like polypropylene that has less than 0.5% of the steel modulus of elasticity and less than 10% of steel strength.

This study describes a simulation-based approach for informing the incorporation of Phase Change Materials (PCMs) in buildings designed to the "Passive House" standard. PCMs provide a minimally invasive method of adding thermal mass to a building, thus mitigating overheating events. Phase change transition temperature, quantity, and location of PCM were all considered while incrementally adding PCM to Passive House simulation models in multiple climate zones across the United States. Whole building energy simulations were performed using EnergyPlus from the US Department of Energy. A prototypical Passive House with a 1500 Watt electric heater and no mechanical cooling was modeled. The effectiveness of the PCM was determined by comparing the zone-hours and zone-degree-hours outside the ASHRAE defined comfort zone for all PCM cases against a control simulation without PCM. Results show that adding PCM to Passive Houses can significantly increase thermal comfort so long as the house is in a dry or marine climate. The addition of PCM in moist climates will not significantly increase occupant comfort because the majority of discomfort in these climates arises due to latent load. For dry or marine climates, PCM has the most significant impact in climates with lower cooling degree-days, reducing by 93% the number of zone-hours outside of thermal comfort and by 98% the number of zone-degree-hours uncomfortable in Portland, Oregon. However, the application of PCM is not as well suited for very hot climates because the PCM becomes overcharged. Only single digit reductions in discomfort were realized when modeling PCM in a Passive House in Phoenix, Arizona. It was found that regardless of the climate PCM should be placed in the top floor, focusing on zones with large southern glazing areas. Also, selecting PCM with a melt temperature of 25°C resulted in the most significant increases in thermal comfort for the majority of climates studied.

Thesis (M. Tech. (Mech. Eng.)) -- Central University of Technology, Free state, 2010
The purpose of this research is to minimize the use of active systems in providing thermal comfort in single-family detached, middle to high income residential buildings in Bloemfontein. The typical case study house was selected according to the criteria as reviewed by Mathews et al., (1999). Measurements were taken for seven days (18 – 24 May 2009). The measurements were carried out in the winter period for Bloemfontein, South Africa. Ecolog TH1, humidity and temperature data logger was used in doing the measurements. These measurements included indoor temperatures and indoor relative humidity. Temperature swings of 8.43 ºC and thermal lag of 1 hour were observed. For the period of seven days (168 hours), the house was thermally comfortable for 84 hours. Thermal analysis for the base case house was done using Ecotect™ (building analysis software) and the simulated results were compared with the measured results. A mean bias error (MBE) of between 10.3% ≤≤11.5% was obtained on the initial calibration. The final calibration of the model yielded error between0.364% ≤≤0.365%. The final calibration model which presented a small error was adopted as the base case. Passive strategies were incorporated to the Ecotect™ model (final calibrated model) singly and in combination; then both thermal and space load simulations were obtained and compared to simulations from the original situation (base case) for assessing improvements in terms of thermal comfort and heating, ventilation and air conditioning (HVAC) energy consumption. Annual HVAC electricity savings of up to 55.2 % were obtained from incorporating passive strategies in combination. Incorporating passive strategies resulted in small improvements in thermal comfort.

The in-situ examination of historical structures for diagnostic and monitoring purposes is a troublesome work that necessitates the use of non-destructive investigation (NDT) techniques. The methods of quantitative infrared thermography (QIRT) and ultrasonic testing have distinct importance in this regard. The key concern of the study was developing the in-situ use of QIRT for assessment of stone masonry wall sections having different sublayer(s) and failures. For that purpose, the non-destructive in-situ survey composed of QIRT and ultrasonic testing was conducted on a 16th century monument, Cenabi Ahmet PaSa Camisi, suffering from structural cracks, dampness problems and materials deterioration. The combined use of these two methods allowed to define the thermal inertia characteristics of structural cracks in relation to their depth. The temperature evolution in time during the controlled heating and cooling process was deployed for the cracks/defects inspection. The superficial and deep cracks were found to have different thermal responses to exposed conditions which made them easily distinguishable by QIRT analyses. The depth of cracks was precisely estimated by the in-situ ultrasonic testing data taken in the indirect transmission mode. The inherently good thermal resistivity of the wall structure was found to have failed due to entrapped moisture resulting from incompatible recent plaster repairs. The IRT survey allowed to detect the wall surfaces with different sublayer configurations due to their different thermal inertia characteristics. The knowledge and experience gained on the experimental set-ups and analytic methods were useful for the improvement of in-situ applications of QIRT and ultrasonic testing.

O presente trabalho apresenta uma análise numérica do desempenho térmico de painéis construídos utilizando o sistema light steel framing (LSF) submetido a ação térmica decorrente de um incêndio. O objeto de estudo foram painéis utilizados na construção de duas casas modelo localizadas na Universidade Tecnológica Federal do Paraná campus Curitiba, construídas com materiais disponíveis comercialmente no Brasil e as análises utilizaram propriedades disponibilizadas pelos fabricantes e pela norma brasileira. A análise numérica foi realizada no software ANSYS, com base no método dos elementos finitos em análise térmica transiente. O modelo foi validado com base em comparação com análises experimentais pesquisadas na literatura. Quatro painéis obtidos das casas modelo foram analisados. Os painéis que utilizaram lã de PET para preenchimento da cavidade foram também analisados com preenchimento de lã de vidro. Um painel simples, com a cavidade preenchida por ar foi analisado para ser usado como referência. Por fim, com a utilização de coeficientes de redução da resistência ao escoamento propostos pela ABNT NBR 14323:2001, determinou-se a redução da resistência do aço do perfil de acordo com o tempo de exposição ao incendio e o tempo de resistência ao fogo dos perfis. Com base nos resultados obtidos é possível afirmar que mesmo para os paneis com pior desempenho, a proteção obtida pode ser suficiente, a depender do carregamento aplicado ao montante e do Tempo requerido de resistência ao fogo necessário. O presente trabalho apresenta informação relevante sobre o desempenho térmico em situação de incêndio do sistema LSF constituído com materiais brasileiros.
The thermal performance of light steel framing (LSF) panels was the objective of this study. The study subject was panels used in the construction of two model houses located at Federal Technology University – Parana, built with materials commercially available in Brazil. The analysis was set with material properties from the manufacturer and in compliance with the Brazilian regulation, using the finite element method for a transient thermal analysis. The model validation was based on experimental tests available in the literature. Based on the validated model, the four panels have been analyzed. Two of the panels used PET wool in the cavity for insulation and the analysis was repeated with them replacing it for glass wool. A panel with no insulation was also analyzed to be used as reference. Based on the analysis results and the resistance reduction coefficients proposed by ABNT NBR 14323:2001, the resistance decrease of the studs due to the fire exposure and the panels resistance to fire were determined. Based on the obtained results, it can be affirmed that, depending on the applied load and the required Equivalent time of fire exposure, even the less protective configuration of the panels presented can be viable. The current study presented relevant information about the performance of LSF manufactured in Brazil when exposed to fire.

La littérature scientifique révèle que les résultats in vitro sur les matériaux dentaires ont une faible corrélation avec le comportement clinique. Les tests standardisés aux normes fournissent des informations précieuses et pertinentes sur les propriétés des matériaux dentaires, et permettent aussi de comparer les résultats de différents instituts. Cependant, le développement de nouveaux matériaux à partir de nouvelles formulations chimiques nécessite une amélioration des méthodes d'évaluation. Ce travail de recherche est réalisé dans le but d'approfondir les connaissances sur les méthodes d'évaluation des matériaux dentaires avant insertion dans la cavité buccale. Une grande importance a été donnée au choix des matériaux à tester ; nous nous sommes basés sur les dernières tendances actuelles et les derniers développements de composition de matériaux dentaires. La même importance a été donnée à des méthodes et des techniques d'essai au laboratoire ; leur corrélation avec les résultats cliniques a été mise en évidence. Les modifications apportées à la méthodologie de ces tests ont exploré davantage les aspects cachés des différentes interactions de paramètres. La caractérisation et l'évaluation des matériaux dentaires nécessitaient une meilleure compréhension de l'interaction entre les différentes propriétés pour expliquer le vieillissement des matériaux. Notre travail a consisté à combiner de nombreuses études pour répondre à ce sujet. Les études ont porté sur les propriétés mécaniques et physiques, le composite fibré et Bulk, les matériaux CAM CAD, les adhésifs dentaires, le choc thermique et le cyclage thermique, le bisphénol A. L'objectif final était de développer un simulateur oral qui permettrait la reproduction de différents paramètres chimiques, physiques et mécaniques de l'environnement buccal, permettant ainsi de combler l'écart entre les tests in vitro et in vivo de matériaux dentaires
Scientific literature reveals that in vitro results are poorly correlated to materials clinical behavior. ISO standardized testing provides valuable information about the dental materials properties, and enables result comparison between different institutes. Conversely, new materials chemistry and formulations requires improved methodology and testing methods. Throughout our studies included in this work, the main objective was to reach a more global knowledge of the way dental materials are evaluated before being inserted into the oral cavity. A great deal of emphasis was given to the choice of materials to be tested, and that it would represent the current trends in dental practice and the latest developments in material composition. Equal highlight was given to the choice of testing methodology and laboratory testing techniques and their correlation to the clinical outcome. The modifications made to the methodology of these tests explored further the concealed aspects of different parameter interactions. Dental materials characterization and assessment required more understanding about the interaction between different properties to explain material aging; our work was to combine numerous studies to answer this topic. The studies included mechanical and physical properties, bulk and fiber composite, CAD CAM block materials, dental resin adhesive, thermal shock and thermal cycling, Bisphenol A. The final objective was to develop an oral simulator that would enable the reproduction of different chemical, physical and mechanical parameters of the oral environment, thus permitting to bridge the gap between in vitro and in vivo testing of dental materials

Presented work deals with the study progressive heat-reflecting foil thermal insulating materials and defines their thermal insulation properties. The work describes a transport mechanism of thermal energy in the structure of heat-reflecting materials, their physical properties, especially heat resistance, compared to the conventional thermal insulating materials available on Czech market. The main applications ways and installation methods of these materials (especially in low-energy and passive buildings) are also shown. The practical part is focused on asembling the measuring device HOT BOX in accordance with the valid standards, to determine the heat resistance of heat-reflecting materials. In next step the measurement of reflection of aluminum foils (an integral part of the structural arrangement heat-reflecting foil insulations) was performed.

The theme of the diploma thesis is the study of physical properties of various building materials in buildings in low-energy construction. The work is mainly focused on the influence of the thermal accumulation properties of building materials used in buildings in order to achieve low energy consumption for heating. The thesis compares the energy characteristics of five different constructional material variants of the house.

The theoretical part of the thesis is devoted to the issue thermal insulation plasters which can be applied in the remediation of buildings. The practical part deals with optimizing the composition of thermal insulation plaster-based lightweight aggregate of the foam glass and with possible substitution of cement for other binders with latent hydraulic properties. The resultant plaster should meet the best ratio of mechanical and thermal insulating properties.

Dissertation (Ph.D.)-- Worcester Polytechnic Institute.
Keywords: temperature measurement; heat flux maps; Cone Calorimeter; three-dimensional heat conduction; fire growth models; retainer frame; ceramic fiberboard; edge effect; one-dimensional heat conduction; heat flux mapping procedure; infrared camera; specimen preparation; edge frame; one-dimensional heat conduction model; thermal properties. Includes bibliographical references (p.202-204).

Ces travaux traitent de l'utilisation de la thermographie infrarouge dans le cadre du contrôle non destructif des ouvrages de génie civil.Une première partie, traite de l’étude des paramètres influençant la mesure in situ, de la capacité de la technique à détecter la variation de propriétés intrinsèques au matériau, et de la détection de délaminations. Les résultats présentés sont issus de mesures expérimentales appuyées par une approche numérique aux éléments finis. Dans un premier temps, une étude sur la capacité de la thermographie infrarouge à détecter des variations de porosité ou de teneur en eau a été réalisée. Dans un second temps, des travaux sont menés sur la détermination des seuils de détection des délaminations en fonction des conditions d’exposition. Ils ont montré un seuil de détection correspondant à un rapport de 2, entre l’extension latérale du défaut et sa profondeur, pour un ensoleillement direct, et à un rapport de 3,3 pour un ouvrage soumis uniquement aux variations de température de l’air. La réalisation d’un suivi temporel combiné à l’étude de l’évolution des gradients temporels de température permet d’améliorer ces seuils de détection. Enfin, une étude originale sur le pontage présent au niveau des délaminations, a montré la prédominance de l’influence de celui‐ci sur la profondeur des délaminations.Une deuxième partie porte sur les travaux réalisés dans le cadre du projet ANR‐SENSO. Ils traitent de la combinaison des résultats issus de différentes techniques de CND dans le cadre plus large de l'amélioration des diagnostics pour la gestion du patrimoine
This thesis focuses on the use of infrared thermography as a tool for non destructive testing ofbuildings. Mainly, the application is on civil engineering projects.The first part includes identifying the parameters that can affect this in situ technique. Thisparticularly deals with the infrared thermography capacity to detect intrinsic property variations, anddelamination detection. Combination of experiments on concrete slabs and numerical simulationsare used. In a first step, a study on the capacity of thermography to detect porosity and watercontent variation was conducted. In a second step a study on the thresholds for detectingdelaminations based on exposure conditions is carried out. As an outcome, the threshold that hasbeen detected corresponds to a ratio of 2 between the lateral extension of the defect and its depthto direct sunlight; while a ratio of 3,3 if it is exposed to air temperature variations. This studysuggests that a time monitoring combined with the study of the evolution of temporal temperaturegradients can improve the detection limits. Finally, an original study showed the predominance ofthe influence of bridging on the depth of delamination.The second part tackles the works carried out during the ANR project SENSO. Results fromdifferent non destructive tools were coupled for the purpose of improving diagnosis in the assetmanagement

Le travail présenté dans ce document vise à mettre en évidence et à comprendre l'effet de la taille nanométrique des renforts sur les propriétés des nanocomposites avec une approche expérimentale. Des nanocomposites de PMMA et particules de silice (15nm, 25nm, 60nm, 150nm et 500nm) de fractions volumiques 2 0/0, 40/0 et 6 0/0 ont été fabriqués. Des analyses multi-échelles (MET et DRX-WAXS) ont montré que les paramètres caractéristiques de la microstructure des nanocomposites varient avec la taille des nanoparticules. En effet, la diminution de la taille des nanoparticules à fraction volumique constante a entrainé une diminution de la distance intermoléculaire. Cette diminution a induit une densification de la matrice et une réduction de la mobilité des chaînes de la matrice. Des essais mécaniques (traction, DMA) ont montré que les modules de Young (E) et de conservation (E') des nanocomposites augmentent avec la diminution de la taille des nanoparticules à fraction volumique constante. Et que l'augmentation de E' est conservée avec l'augmentation de la température. Une augmentation des températures de transition vitreuse (Tg) et de dégradation (Td) a également été observée avec les essais DSC, DMA et ATG. Le modèle de la borne inférieure d'Hashin-Shtrikman étendue aux nanocomposites à renforts sphériques proposé par Brisard a été utilisé. La modélisation des modules élastiques des nanocomposites a montré que pour reproduire les données expérimentales, il faut que d'une part que les modules surfaciques caractérisant l'interface soient dépendants de la taille des nanoparticules. Et d'autre part, tenir compte de l'état de dispersion des nanoparticules
The work presented in this paper aims to highlight and to understand the size effect of nano-reinforcements on nanocomposite properties With an experimental approach. Nanocomposites of PMMA and silica particles With different sizes (15nm, 25nm, 60nm, 150nm and 500nm) and volume fractions (20/0, 4 0/0 and 60/0) were manufactured. Multiscale analysis (MET and DRX-WAXS) have shown that the characteristic parameters of the microstructure of nanocomposites vary With the size of the nanoparticles. Indeed, the decrease in the size of nanoparticles at a given volume fraction implies a decrease of the intermolecular distance. This decrease has induced a densification of the matrix and a decrease of the matrix chain mobility. Mechanical tests (tensile, DMA) have shown that the young (E) and the conservation (E') moduli of the nanocomposites increase With the decrease in the size of the nanoparticles With a constant volume fraction. And the increase of E l is kept when temperature growing. An increase in glass transition (Tg) and degradation temperature (Td) was also observed With the DSC, DMA and ATG tests. Experimental elastic properties of the nanocomposites were used to assess the relevance of size effect micromechanical models, particularly the Hashin-Shtrikman bounds With interface effects proposed by Brisard. The modeling has shown that to reproduce the experimental elastic moduli of nanocomposites, the elastic coefficients of the interface must be dependents on particle sizes. And the state of dispersion of particles must be taken into account

Master´s thesis deals with an assessment of investment return in saving precurations. The issue is used on an ordinary detached family house. The assessment is done in more variants to reach an objective comparison of the most advantageous investments. In the first part there is a comprehensive theory explaining the connections of the procedures and the algorithms of the calculations. The second part is calculation, especially from the thermal engineering, energy rating of buildings and the economic return on investment. The third part is an evaluation which, on the basis of the experiences and the results from the thesis, offers a proces show to think in case of intended reconstruction and how to evaluate the efficiency of the investments in the saving precurations.

L'arc-fil est un nouveau procédé de fabrication additive utilisant une cellule desoudage robotisée pour la fabrication, couche par couche, de pièces de grandes dimensions. Ilpermet de réaliser des ébauches de pièces unitaires ou de petites séries avec des coûts et desdélais de fabrication réduits. Les premiers développements se sont principalement orientés sur laréalisation de pièces à forte valeur ajoutée en alliage de titane et d’aluminium pour le secteuraéronautique et aérospatial, et intéressent maintenant d’autres secteurs tels que les industriesnavales, pétrolières, ferroviaires et mécaniques utilisant des aciers. Ce travail propose uneméthodologie de sélection des paramètres et des stratégies de dépôts, avec le contrôle final despièces fabriquées. Il porte sur deux matériaux : un acier C-Mn à haute limite d’élasticité(ER100) et un acier inoxydable austénitique (316LSi). Le résultat des caractérisations permetd’établir le lien entre les conditions de fabrication, les dimensions géométriques et les propriétésmicrostructurales et mécaniques des pièces obtenues, ce qui conduit au final à une démarchepermettant de faire évoluer le procédé vers l’industrialisation
Wire-arc additive manufacturing is a new process using a common weldingrobotic cell to build large parts layer by layer. It allows building rough single pieces orsmall series parts with a low cost and a short delay. First developments were done ontitanium and aluminum parts for aeronautic and space applications, but more industriessuch as maritime, oil and gas, railway…are now interested into it. In this work, amethodology is proposed to define suitable process parameters and deposit’s strategies,with the final control of the elaborated parts. Developments are done on both highstrength steel ER100 and austenitic stainless steel 316LSi. The results of theexperimental characterisation enable to show the relations between the manufacturingconditions, the dimensions, the microstructure and the mechanicals properties of theparts, and finally lead to guidelines to evolve the wire-arc additive manufacturingtowards industrialisation

La thermographie infrarouge est une méthode largement employée pour la caractérisation des propriétés thermophysiques des matériaux. L’avènement des diodes laser pratiques, peu onéreuses et aux multiples caractéristiques, étendent les possibilités métrologiques des caméras infrarouges et mettent à disposition un ensemble de nouveaux outils puissants pour la caractérisation thermique et le contrôle non desturctif. Cependant, un lot de nouvelles difficultés doit être surmonté, comme le traitement d’une grande quantité de données bruitées et la faible sensibilité de ces données aux paramètres recherchés. Cela oblige de revisiter les méthodes de traitement du signal existantes, d’adopter de nouveaux outils mathématiques sophistiqués pour la compression de données et le traitement d’informations pertinentes. Les nouvelles stratégies consistent à utiliser des transformations orthogonales du signal comme outils de compression préalable de données, de réduction et maîtrise du bruit de mesure. L’analyse de sensibilité, basée sur l’étude locale des corrélations entre les dérivées partielles du signal expérimental, complète ces nouvelles approches. L'analogie avec la théorie dans l'espace de Fourier a permis d'apporter de nouveaux éléments de réponse pour mieux cerner la «physique» des approches modales.La réponse au point source impulsionnel a été revisitée de manière numérique et expérimentale. En utilisant la séparabilité des champs de température nous avons proposé une nouvelle méthode d'inversion basée sur une double décomposition en valeurs singulières du signal expérimental. Cette méthode par rapport aux précédentes, permet de tenir compte de la diffusion bi ou tridimensionnelle et offre ainsi une meilleure exploitation du contenu spatial des images infrarouges. Des exemples numériques et expérimentaux nous ont permis de valider dans une première approche cette nouvelle méthode d'estimation pour la caractérisation de diffusivités thermiques longitudinales. Des applications dans le domaine du contrôle non destructif des matériaux sont également proposées. Une ancienne problématique qui consiste à retrouver les champs de température initiaux à partir de données bruitées a été abordée sous un nouveau jour. La nécessité de connaitre les diffusivités thermiques du matériau orthotrope et la prise en compte des transferts souvent tridimensionnels sont complexes à gérer. L'application de la double décomposition en valeurs singulières a permis d'obtenir des résultats intéressants compte tenu de la simplicité de la méthode. En effet, les méthodes modales sont basées sur des approches statistiques de traitement d'une grande quantité de données, censément plus robustes quant au bruit de mesure, comme cela a pu être observé
Infrared thermography is a widely used method for characterization of thermophysical properties of materials. The advent of the laser diodes, which are handy, inexpensive, with a broad spectrum of characteristics, extend metrological possibilities of infrared cameras and provide a combination of new powerful tools for thermal characterization and non destructive evaluation. However, this new dynamic has also brought numerous difficulties that must be overcome, such as high volume noisy data processing and low sensitivity to estimated parameters of such data. This requires revisiting the existing methods of signal processing, adopting new sophisticated mathematical tools for data compression and processing of relevant information.New strategies consist in using orthogonal transforms of the signal as a prior data compression tools, which allow noise reduction and control over it. Correlation analysis, based on the local cerrelation study between partial derivatives of the experimental signal, completes these new strategies. A theoretical analogy in Fourier space has been performed in order to better understand the «physical» meaning of modal approaches.The response to the instantaneous point source of heat, has been revisited both numerically and experimentally. By using separable temperature fields, a new inversion technique based on a double singular value decomposition of experimental signal has been introduced. In comparison with previous methods, it takes into account two or three-dimensional heat diffusion and therefore offers a better exploitation of the spatial content of infrared images. Numerical and experimental examples have allowed us to validate in the first approach our new estimation method of longitudinal thermal diffusivities. Non destructive testing applications based on the new technique have also been introduced.An old issue, which consists in determining the initial temperature field from noisy data, has been approached in a new light. The necessity to know the thermal diffusivities of an orthotropic medium and the need to take into account often three-dimensional heat transfer, are complicated issues. The implementation of the double singular value decomposition allowed us to achieve interesting results according to its ease of use. Indeed, modal approaches are statistical methods based on high volume data processing, supposedly robust as to the measurement noise

A thesis submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy
The cracking of mass and structural concrete due to thermal stress is a major problem in the concrete construction industry. Concrete will crack when the thermal stress exceeds tbe tensile strength of the concrete, Decisions on the type of concrete mix, cooling facilities and construction techniques to be used in the erection of a concrete structure can only be made if the thermal behaviour and strength of the concrete can be predicted during hydration. This thesis describes the development of a low cost, computer controlled, adiabatic calorimeter to determine tlte heat of hydration and a probe to determine the thermal conductivity or concrere samples. The main thrust of this thesis is the development of the thermal conductivity probe which, for the first time, can measure the thermal conductivity of concrete through all stages of hydration. A thermal model was also developed to verify the results, and the use of the calorimeter for temperature matched curing tests is also discussed. Results, obtained from the test procedures described, will provide far more accurate predictions of the temperatures in concrete structures than was possible in the past.
Andrew Chakane 2018

Cheng Bo-ki.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.
Includes bibliographical references (leaves 150-153).
Abstracts in English and Chinese.
Chapter chapter 1 --- Introduction --- p.10
Chapter chapter 2 --- Background & Literature --- p.15
Chapter 2.1 --- Why Environmental Design? --- p.15
Comfort and Energy --- p.15
"Our Problems: Energy, Environment, and Health" --- p.19
Chapter 2.2 --- Knowledge in Environmental Design --- p.27
What is Environmental Design? --- p.27
Current knowledge in Environmental Design: Thermal Performance --- p.30
Thermal Studies in Hong Kong --- p.37
Chapter 2.3 --- Summary and Propositions --- p.42
Chapter chapter 3 --- Scale Model Study --- p.47
Chapter 3.1 --- Test Modules Application --- p.47
Chapter 3.2 --- Research Methodology & Experimental Setup --- p.54
Testing Facility in CUHK --- p.54
Solarimeter Substitute --- p.58
Chapter 3.3 --- Experimental Series --- p.61
Chapter 3.3.1 --- Envelope Colour --- p.61
Chapter 3.3.2 --- Windows --- p.73
Chapter 3.3.3 --- Shading --- p.75
Chapter 3.3.4 --- Thermal Mass --- p.80
Chapter 3.3.5 --- Orientations --- p.83
Chapter 3.3.6 --- "Combined Effects ofThermal Mass, Windows and Orientations" --- p.85
Chapter 3.3.7 --- "Combined Effects ofThermal Mass, Shading and Orientations" --- p.88
Chapter 3.4 --- Summary of Experiments --- p.90
Chapter 3.5 --- Predicting Indoor Air Temperature --- p.93
Chapter 3.5.1 --- Development of Predictive Formulas --- p.93
Chapter 3.5.2 --- Parametric Study of Envelope Colour --- p.97
Chapter 3.5.3 --- Parametric Study of Window Shading --- p.100
Chapter chapter 4 --- Field Study --- p.104
Chapter 4.1 --- Description of Housing Unit: Concord-I Block --- p.104
Chapter 4.2 --- Experimental Setup --- p.105
Chapter 4.3 --- Result of Field Measurement --- p.108
Chapter 4.3.1 --- Perform ance of top-most floor --- p.108
Chapter 4.3.2 --- Performance of Individual Rooms --- p.109
Chapter 4.3.3 --- Effect of Orientation --- p.110
Chapter 4.3.4 --- Indoor Thermal Comfort --- p.113
Chapter 4.4 --- Summary of Field Measurement --- p.116
Chapter chapter 5 --- Thermal Performance Prediction --- p.118
Chapter chapter 6 --- Conclusion --- p.126
Appendix 1 --- p.131
Appendix 2 --- p.133
Appendix 3 --- p.140

碩士
國立臺北科技大學
土木工程系土木與防災碩士班
107
The inorganic mineral powder coating materials have the functions of reflection and insulation, which can be divided into two types: Cement (UU620) and Geopolymer (UU500). The coated materials have six colors of white, red, blue, green, yellow and gray which are capable of reflecting and blocking part of the radiation heat into the concrete building. The reflectivity and thermal conductivity of inorganic mineral powder materials were measured by spectrometers and heat conduction instrument, respectively; and measurement of adhesion according to ASTM D3359. Notably, the obtained results show that the coating materials have high reflectivity values, excellent thermal conductivity, and the adhesion of different colors is quite good. Through the visible light and infrared radiation concrete plate specimens, the result of turning the light on and off, the upper and lower heat flux, surface and environmental temperature were measured to explore the insulation and cooling effect in different colors. Moreover, it possesses the excellent thermal insulation. Finally, the coated concrete plate has better thermal insulation ability than the uncoated concrete plate in situ test. Through the above-mentioned heat flux experimental data and the formula set by the Green Building Technical Specification, the heat transmission rate of the coated specimen has calculated.

碩士
國立高雄科技大學
土木工程系
107
The research objective was to assess the mechanical properties, shrinkage, thermal expansion and conductivity, and chloride penetration of concrete containing reclaimed asphalt pavement materials. Rich and lean concrete mixtures were blended by water to cementitious materials (w/c) ratio of 0.5 and the RAP materials were replacing both coarse and fine aggregates by 0, 20, 40, 60, 80, and 100-%. The concrete cylinders and specimens were cast and cured in the water tank for 7, 28, 56, and 90 days. The test results demonstrate as follows: the mixing temperatures of all concrete mixtures increased among 24.5 and 26.8, from 20-°C; the unit weight, compressive strength, pulse velocity, and shrinkage decreased, when more percentage of RAP were incorporated; thermal conductivity increased when more percentage of RAP were added. However, thermal conductivity decreased when longer curing time of concrete were given; thermal expansion also increased when more percentage of RAP were blended; lastly, the coulombs or charge pass indicating the chloride penetration increased on 90-day moisture-cured concrete specimens, when more RAP were replaced.

Indiana University-Purdue University Indianapolis (IUPUI)
A constant-volume combustor is used to investigate the ignition initiated by a traversing jet of reactive hot gas, in support of combustion engine applications that include novel wave-rotor constant-volume combustion gas turbines and pre-chamber IC engines. The hot-jet ignition constant-volume combustor rig at the Combustion and Propulsion Research Laboratory at the Purdue School of Engineering and Technology at Indiana University-Purdue University Indianapolis (IUPUI) was used for this study. Lean premixed combustible mixture in a rectangular cuboid constant-volume combustor is ignited by a hot-jet traversing at different fixed speeds. The hot jet is issued via a converging nozzle from a cylindrical pre-chamber where partially combusted products of combustion are produced by spark- igniting a rich ethylene-air mixture. The main constant-volume combustor (CVC) chamber uses methane-air, hydrogen-methane-air and ethylene-air mixtures in the lean equivalence ratio range of 0.8 to 0.4. Ignition delay times and ignitability of these combustible mixtures as affected by jet traverse speed, equivalence ratio, and fuel type are investigated in this study.

Indiana University-Purdue University Indianapolis (IUPUI)
Fused deposition modeling (FDM) represents one of the most common techniques for rapid proto-typing in additive manufacturing (AM). This work applies image based thermography to monitor the FDM process in-situ. The nozzle temperature, print speed and print orientation were adjusted during the fabrication process of each specimen. Experimental and numerical analysis were performed on the fabricated specimens. The combination of the layer wise temperature profile plot and temporal plot provide insights for specimens fabricated in x, y and z-axis orientation. For the x-axis orientation build possessing 35 layers, Specimens B16 and B7 printed with nozzle temperature of 225 C and 235 C respectively, and at printing speed of 60 mm/s and 100 mm/s respectively with the former possessing the highest modulus, yield strength, and ultimate tensile strength. For the y-axis orientation build possessing 59 layers, Specimens B23, B14 and B8 printed with nozzle temperature of 215 C, 225 C and 235 C respectively, and at printing speed of 80 mm/s, 80 mm/s and 60 mm/s respectively with the former possessing the highest modulus and yield strength, while the latter the highest ultimate tensile strength. For the z-axis orientation build possessing 1256 layers, Specimens B6, B24 and B9 printed with nozzle temperature of 235 C, 235 C and 235 ➦C respectively, and at printing speed of 80 mm/s, 80 mm/s and 60 mm/s respectively with the former possessing the highest modulus and ultimate tensile strength, while B24 had the highest yield strength and B9 the lowest modulus, yield strength and ultimate tensile strength. The results show that the prints oriented in the y-axis orientation perform relatively better than prints in the x-axis and z-axis orientation.

Indiana University-Purdue University Indianapolis (IUPUI)
Ignition of a combustible mixture by a transient jet of hot reactive gas is important for safety of mines, pre-chamber ignition in IC engines, detonation initiation, and in novel constant-volume combustors. The present work is a numerical study of the hot-jet ignition process in a long constant-volume combustor (CVC) that represents a wave-rotor channel. The mixing of hot jet with cold mixture in the main chamber is first studied using non-reacting simulations. The stationary and traversing hot jets of combustion products from a pre-chamber is injected through a converging nozzle into the main CVC chamber containing a premixed fuel-air mixture. Combustion in a two-dimensional analogue of the CVC chamber is modeled using global reaction mechanisms, skeletal mechanisms, and detailed reaction mechanisms for four hydrocarbon fuels: methane, propane, ethylene, and hydrogen. The jet and ignition behavior are compared with high-speed video images from a prior experiment. Hybrid turbulent-kinetic schemes using some skeletal reaction mechanisms and detailed mechanisms are good predictors of the experimental data. Shock-flame interaction is seen to significantly increase the overall reaction rate due to baroclinic vorticity generation, flame area increase, stirring of non-uniform density regions, the resulting mixing, and shock compression. The less easily ignitable methane mixture is found to show higher ignition delay time compared to slower initial reaction and greater dependence on shock interaction than propane and ethylene. The confined jet is observed to behave initially as a wall jet and later as a wall-impinging jet. The jet evolution, vortex structure and mixing behavior are significantly different for traversing jets, stationary centered jets, and near-wall jets. Production of unstable intermediate species like C2H4 and CH3 appears to depend significantly on the initial jet location while relatively stable species like OH are less sensitive. Inclusion of minor radical species in the hot-jet is observed to reduce the ignition delay by 0.2 ms for methane mixture in the main chamber. Reaction pathways analysis shows that ignition delay and combustion progress process are entirely different for hybrid turbulent-kinetic scheme and kinetics-only scheme.

Mu Jun.
Thesis submitted in: December 2005.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2006.
Includes bibliographical references (leaves 181-183).
Abstracts in English and Chinese.
Chapter 1. --- Introduction --- p.1
Chapter 2. --- Issues and Background --- p.5
Chapter 2.1. --- Why Ecological Architecture? --- p.5
Chapter 2.1.1. --- Fossil Fuels and Environmental Issues --- p.5
Chapter 2.1.2. --- The Buildings' Role in the Issues --- p.9
Chapter 2.2. --- Knowledge in Ecological Design --- p.11
Chapter 2.2.1. --- About Ecological Architecture --- p.11
Chapter 2.2.2. --- Thermal Study ~ A Significant Way to Ecological Architecture --- p.13
Chapter 2.2.3. --- What is Suitable Ecological Architecture for Loess Plateau areas of China --- p.16
Chapter 3. --- Defining the Future Ecological Architecture in Loess Plateau Areas --- p.20
Chapter 3.1. --- Economy for Building --- p.20
Chapter 3.1.1. --- Situation --- p.20
Chapter 3.1.2. --- Technological Strategies towards a Cost-effective Ecological Approach --- p.22
Chapter 3.1.3. --- Alternative-Technological Approach --- p.24
Chapter 3.2. --- Climate --- p.25
Chapter 3.2.1. --- Climatic Characteristics --- p.25
Chapter 3.2.2. --- A climatically Responsive Approach ~ Selective Environmental Design --- p.32
Chapter 3.2.3. --- Climatic Response of Thermal Design Guidelines --- p.33
Chapter 3.2.3.1. --- Minimizing Heat loss through Building Fabrics --- p.34
Chapter 3.2.3.2. --- Utilization of Available Natural Energy --- p.37
Chapter 3.3. --- Benefits from Vernacular Architecture --- p.45
Chapter 3.3.1. --- Earth ArchitecturéؤVernacular Architecture on Loess Plateau --- p.45
Chapter 3.3.1.1. --- Classification --- p.46
Chapter 3.3.1.2. --- Environmental Performance --- p.53
Chapter 3.3.2. --- Literature Review of Studies on Earth Architecture --- p.58
Chapter 3.3.2.1. --- Properties of Earth-based Materials --- p.58
Chapter 3.3.2.2. --- Literature on Earth Architecture --- p.60
Chapter 3.3.3. --- Issues and Development --- p.76
Chapter 3.3.3.1. --- Limitation in Existing Earth Architecture of Loess Plateau --- p.76
Chapter 3.3.3.2. --- Recent Research on Developing Earth Architecture in Loess Plateau Areas --- p.77
Chapter 3.3.3.3. --- Considerations --- p.81
Chapter 3.4. --- Conclusion --- p.82
Chapter 4. --- Making of the Classroom as Designed for the Thermal Study --- p.84
Chapter 4.1. --- Why a Classroom? --- p.84
Chapter 4.2. --- The School Project and the Classroom Simulated --- p.85
Chapter 5. --- Thermal Study by Simulating Experiments --- p.88
Chapter 5.1. --- Research Methodology --- p.88
Chapter 5.2. --- Program Validation --- p.89
Chapter 5.3. --- Experimental Series of Simulation and Model Setup --- p.93
Chapter 5.4. --- Thermal Mass and Insulation --- p.95
Chapter 5.4.1. --- External Wall --- p.95
Chapter 5.4.2. --- Roof Study --- p.97
Chapter 5.4.3. --- "Windows, Doors and Glazing" --- p.100
Chapter 5.4.4. --- Incorporated Performance --- p.103
Chapter 5.5. --- Passive system for natural energy use --- p.106
Chapter 5.5.1. --- Passive Solar System Study --- p.106
Chapter 5.5.1.1. --- Wall-based Passive Solar System --- p.106
Chapter 5.5.1.2. --- Roof-based Passive Solar System --- p.125
Chapter 5.5.1.3. --- System Comparison in Thermal Performance --- p.135
Chapter 5.5.2. --- Natural Ventilation System with the Heat Exchanger --- p.137
Chapter 5.5.2.1. --- Pre-warming Effect of the Solar Space --- p.139
Chapter 5.5.2.2. --- Effect of the Earth-air-tunnel --- p.142
Chapter 5.5.2.3. --- Incorporation with the Chimney --- p.153
Chapter 5.5.2.4. --- Comparison in Performance --- p.158
Chapter 5.6. --- Summary --- p.159
Chapter 6. --- Design Improvement and Performance Prediction --- p.162
Chapter 6.1. --- System Incorporation and Design Improvement --- p.161
Chapter 6.2. --- Thermal Performance Prediction --- p.167
Chapter 7. --- Conclusion --- p.174
Appendix --- p.179

Current research on thermal effects on guideways has addressed many aspects of the behavior of guideways using two-dimensional models. The two-dimensional models are acceptable for existing guideway designs, in which cross sectional shapes are uniform along the length of the guideway. However, three-dimensional models are necessary for a modular design, in which the track structures that interact with Maglev vehicles are made separately and are assembled into the support structure, and in which the cross sectional shapes are not uniform. A three-dimensional numerical model of the thermal environment, in which the effect of partial shading is taken into account, is implemented for the study of guideway behavior under various thermal environments. The numerical model of the thermal environment is calibrated to the experimental results under the thermal environment at Austin, Texas, and is extrapolated to predict the behaviors of guideways under the thermal environment in Las Vegas, Nevada, which is one of the candidate sites for the implementation and deployment of the high speed Maglev transportation system. This study addresses the suitability of a modular steel guideway design under such a thermal environment. Characteristics of the behavior of guideways under various thermal environments are identified, and the behavior of guideways under the effect of partial shading is summarized.
text

Indiana University-Purdue University Indianapolis (IUPUI)
Zirconia (ZrO2) is an important ceramic material with a broad range of applications. Due to its high melting temperature, low thermal conductivity, and high-temperature stability, zirconia based ceramics have been widely used for thermal barrier coatings (TBCs). When TBC is exposed to thermal cycling during real applications, the TBC may fail due to several mechanisms: (1) phase transformation into yttrium-rich and yttrium-depleted regions, When the yttrium-rich region produces pure zirconia domains that transform between monoclinic and tetragonal phases upon thermal cycling; and (2) cracking of the coating due to stress induced by erosion. The mechanism of erosion involves gross plastic damage within the TBC, often leading to ceramic loss and/or cracks down to the bond coat. The damage mechanisms are related to service parameters, including TBC material properties, temperature, velocity, particle size, and impact angle. The goal of this thesis is to understand the structural and mechanical properties of the thermal barrier coating material, thus increasing the service lifetime of gas turbine engines. To this end, it is critical to study the fundamental properties and potential failure mechanisms of zirconia. This thesis is focused on investigating the structural and mechanical properties of zirconia. There are mainly two parts studied in this paper, (1) ab initio calculations of thermodynamic properties of both monoclinic and tetragonal phase zirconia, and monoclinic-to-tetragonal phase transformation, and (2) image-based finite element simulation of the indentation process of yttria-stabilized zirconia. In the first part of this study, the structural properties, including lattice parameter, band structure, density of state, as well as elastic constants for both monoclinic and tetragonal zirconia have been computed. The pressure-dependent phase transition between tetragonal (t-ZrO2) and cubic zirconia (c-ZrO2) has been calculated using the density function theory (DFT) method. Phase transformation is defined by the band structure and tetragonal distortion changes. The results predict a transition from a monoclinic structure to a fluorite-type cubic structure at the pressure of 37 GPa. Thermodynamic property calculations of monoclinic zirconia (m-ZrO2) were also carried out. Temperature-dependent heat capacity, entropy, free energy, Debye temperature of monoclinic zirconia, from 0 to 1000 K, were computed, and they compared well with those reported in the literature. Moreover, the atomistic simulations correctly predicted the phase transitions of m-ZrO2 under compressive pressures ranging from 0 to 70 GPa. The phase transition pressures of monoclinic to orthorhombic I (3 GPa), orthorhombic I to orthorhombic II (8 GPa), orthorhombic II to tetragonal (37 GPa), and stable tetragonal phases (37-60 GPa) are in excellent agreement with experimental data. In the second part of this study, the mechanical response of yttria-stabilized zirconia under Rockwell superficial indentation was studied. The microstructure image based finite element method was used to validate the model using a composite cermet material. Then, the finite element model of Rockwell indentation of yttria-stabilized zirconia was developed, and the result was compared with experimental hardness data.

PtNiAl bond coats are diffusion aluminide coatings deposited on superalloy based turbine blades for oxidation resistance and improved adhesion between the substrate and the YSZ thermal barrier coating on top. They are deposited by pack aluminisation, which makes their microstructure inherently graded and heterogeneous as well as replete with a variety of precipitates and second phase particles. The microstructure also continuously evolves during thermal cycling, because of interdiffusion with the substrate and the continuous loss of Al to the thermally grown oxide scale on top. During service, the bond coats are exposed to impact, thermal expansion mismatch, thermo-mechanical fatigue and inter-diffusion accompanied by phase transformation, which become leading causes of their failure. The bond coats being B2 crystal structures are known to be brittle at room temperature, due to which they are expected to fail during cooling, although they undergo plastic relaxation by creep above the BDTT. Little attention has been paid to the mechanical response of the bond coats, while a number of studies focus on optimizing their composition for oxidation resistance. The fracture properties of these coatings, in particular, are not very well understood due to the several different length scales of their complex microstructure playing a part. In this context, there is an interest in determination of the fracture toughness of bond coats under different loading and temperature conditions. In the present work, the fracture properties of bond coats is measured with micron-scale resolution using edge notched doubly clamped microbeam structures positioned at individual zones of the graded bond coat, subjected to bending. In order to extract the stress intensity factor for this new configuration and to determine the stress distribution and stability of this geometry under different loading conditions, extended finite element analysis (XFEM) is carried out. After establishing the microbeam geometry as a viable fracture toughness testing configuration, the contribution of different microstructural variables to toughening at room temperature is studied using SEM based in-situ testing. Since the exact composition and structure of the coating depends principally on the elements constituting the matrix-Pt, Ni and Al content, which themselves depend on the deposition parameters, we have examined in detail, coatings aluminised at different temperatures (increasing coating thickness), varying Al content in the pack mixture and starting Pt thicknesses during electro-deposition. These parameters are by no means exhaustive and there is wide scope to investigate the effect of other processing variables as well as their synergistic effects on the mechanical behavior of these coatings. Following this, the high temperature fracture behavior of the stand-alone coatings in tension is also studied to determine their brittle to ductile transition mechanism in the presence of a notch. While this covers the average behavior of the entire coating cross-section, such a study is important to establish the BDTT unambiguously since there are chances of under-estimation of these temperatures in the absence of a notch. Also free¬standing coatings without the underlying substrate offer respite from residual stresses influencing the results of such tests. The present study essentially consists of two distinct parts, one focused on the development of the testing technique to cover multiple length scales of any graded thin film or coating and the other on the determination of fracture properties of the bond coat using these methods. The thesis reads in the following way: Chapter 1 gives an introduction to the diffusion aluminised bond coats, with a focus on the failure mechanisms associated with them while underlying the need for small scale testing in these systems. The conditions driving failure in bond coats can be vast and varied and it is extremely difficult to pin-point a single important cause and also to develop predictive capabilities regarding their failure. This is described as the motivation for the present work, with an objective of finding the variation in fracture toughness values for PtNiAl bond coats of different coating thicknesses and Pt content across the temperature range spanning the BDTT of the sample. Chapter 2 describes in detail all the available literature on thermal barrier coatings in general, and diffusion aluminide bond coats in particular, while specifically highlighting its mechanical response to loads during service. The deposition parameters during pack aluminizing and the graded microstructure which develops as a consequence of the diffusion process are described. The material’s microstructure dictates its properties, but there has been limited work on the mechanical behavior of the coatings themselves due to the difficulty in preparation and testing of free-standing films of the same. Since the base matrix is that of β¬NiAl, and there has been extensive work reported on bulk NiAl in the literature, which is discussed next. This would serve as a benchmark for comparison with the properties of the bond coats themselves, which are expected to respond differently due to their continuously evolving and complex microstructure. A summary of the known mechanical properties of the coatings themselves is given next along with the failure mechanisms that have been proposed. Since the study deals with fracture properties, a short introduction of linear elastic fracture mechanics follows before elaborating on the various small scale fracture testing geometries that have been developed. There are specific differences between testing geometries, stress states as well as in the instrumentation between small scale and bulk fracture toughness tests, which are highlighted. Since these configurations are material and device specific, each group has worked out its own instrument capabilities and mechanics required to extract the mechanical properties of interest from these testing techniques. Due to these differences in addition to the differences in the size scales of the samples tested, the reported properties show a wide variation. Lack of standards add to the difficulty in interpretation of the data; moreover add to the controversy on whether a size effect exists for fracture, as it does for strength. All the non-standard small scale testing configurations require modeling and simulation to extract the desired properties from them, and the present study applies the XFEM to determine the stress distribution and calculate the stress intensity factors corresponding to the fracture loads recorded from experiments. An introduction to the XFEM method is given in the last part. Chapter 3 gives all the experimental and simulation procedures that were carried out in the present work. Since the bond coat properties need to be compared with their bulk counterparts, both the samples are characterized. The exact material compositions chosen for the study were plain NiAl, 2PtAl and 5PtAl among the pack aluminized coatings and bulk arc-melted PtNiAl samples with varying concentrations of Ni and Pt which matched the bond coat matrix compositions. The choice of the three coatings was made depending on the previously known information regarding their microstructure. The deposition conditions, temperature and times of annealing are listed, followed by a brief summary of the general characterization techniques used to study the microstructure of the bond coats before and after fracture testing. Since the micro-beams under bending were fabricated using a focused ion beam, and the micro-tensile specimen were machined by electro-discharge machining, both the micro-machining procedures are described. At such small length scales, conventional testing methods cannot be used and several modifications were incorporated to the testing geometries which are described in the next section which covers two principal fracture testing methods-microbeam bending and mini-tensile testing, along with the advantages and limitations of each. Modeling is an indispensable tool for determining stress distributions in such new geometric configurations involving material property variations, and details of the exact XFEM procedure that was implemented in ABAQUS is given in the last part of this chapter. Chapter 4 summarises the microstructure and indentation properties of the bond coat and bulk NiAl samples characterised using X-ray diffraction, electron microscopy and nanoindentation. XRD was used for phase identification, texture and determination of lattice parameters of the specimen, which confirmed β-NiAl (with no texture) as the matrix with the lattice parameter varying as a function of composition. The SEM-EPMA combination was used for probing the compositional and microstructural gradients, grain size and precipitate distribution across the coating cross-sections. The bond coat was found to have 4 distinct zones with the Ni:Al ratio gradually rising across its thickness. In addition to this, the four zones had very different grain sizes, precipitate type and distributions. Hardness and modulus values were reported from nanoindentation measurements across the coating thickness over a temperature range from 25 to 400˚C and were seen to follow the composition gradients in different ways based on the effect of the off-stoichiometric defects on these properties. The hardness was found to be a minimum for the zone with stoichiometric composition, as was the case in the bulk sample, while the modulus dropped continuously with increasing Ni content in the matrix. These are important to develop a one-to-one correlation with the fracture properties and to understand the micro-mechanisms of the same. Chapter 5 gets on with the specifics of the testing geometry. Since most of the variables of the testing technique were studied using simulation procedures, a large part of this chapter deals with the results from the modeling technique using XFEM. The XFEM is introduced in detail and its applicability in modeling of cracks and discontinuities and advantages over conventional FEM are explained. The material properties are taken from the nanoindentation data and the modeling assumes linear elastic fracture mechanics. As a validation measurement, a conventional three point beam is modeled in bending and the results compared with analytical solutions of the same. The three point beam bending geometry is also used as a benchmark to study the stability of the new geometry, now with fixed boundaries in place of a free ends. This is followed by the results from the modeling for different variables like mesh density, notch root radius, loading offsets, beam dimensions and crack length (a)/specimen width (W) ratios where both the stress distribution as well as KI are captured in 3-D for stationary cracks while crack trajectories are obtained for propagating cracks. The notch root radius is seen to not affect KI below ~300 nm and such notch radii are easily machinable in the FIB at lower currents. The crack trajectory from the experiments is seen to follow the direction of maximum tangential stress, which is also modeled very well in the XFEM. The contribution of KII to the measured stress intensity factor with increasing offsets is also calculated from the model. Stable cracking is seen for the clamped beam geometry, with KI dropping off beyond a critical a/W ratio. This was true even for a model assuming homogeneous, elastic properties with a flat R-curve under load control. This makes the clamped beam structure require higher loads for continued propagation of cracks. This critical ratio is dimension dependent, making a shorter thicker beam stable in comparison to a longer, slender one. This is unusual, especially in comparison to the three point bend geometry which shows stable cracking only in displacement control, specifically for large a/W ratios alone. Also superimposition of the load-displacement curves from simulations with those of experiments gives a good-fit. The experimental results are shown next to back¬up the claims made on geometric stability of such clamped structures. Digital Image Correlation is introduced as a means for direct measurement of crack opening displacements (COD) and fracture toughness without the aid of KI formulations. This also served as a cross¬check on the assumptions of linear elastic fracture mechanics (LEFM) made in the simulation and a good correlation is seen between the CODs measured experimentally and that obtained from the FEM analysis. Fracture toughness measurements of brittle materials with known KIC values, like fused silica glass and single crystal Si film from this proposed geometry are reported as additional validation of this geometry. Further the capabilities of in-situ testing using this geometry to measure R-curve and fatigue properties along with the initiation KIC values are shown via results from monotonic and cyclic loading under different conditions. Chapter 6 returns to address bond coat fracture at room temperature, which is the main objective of the present study. Fracture toughness is evaluated both ex-situ and in-situ, using clamped microbeam bending experiments across individual zones of the 5PtAl bond coat and for different initial Pt contents in the zone 2. KIC is seen to rise sharply with increasing Ni content of the matrix in the former case, from 5 to 15 MPam1/2 which is attributed to the change in defect chemistry with changing stoichiometry. Al rich NiAl is found to be more brittle due to vacancy hardening while Ni rich NiAl is known to increase the metallic character of the NiAl bond. Both Ni rich and Pt rich (Pt,Ni)Al give higher toughnesses among the coatings studied while the crack trajectories and toughening mechanisms distinctly depend on the precipitate morphology in individual zones. Alloying additions are seen to add to the complexity of the fracture behavior of bond coats by strengthening the matrix or by improving its ductility. Micro-kinking, grain boundary and precipitate bridging are seen in the crack wake as contributing factors to partial closure of the crack on unload. The influence of each of the microstructural variable on the fracture mode is dissected in detail before coming to an overall conclusion. The microbeams show controlled, stable cracking, which enable following of the crack trajectories across micron-length scales and make R-curve measurements possible. Both 2PtAl and 5PtAl compositions show a rising R-curve within the length scale of an individual microbeam tested. Size and geometric effects on real vs apparent R-curve behavior are discussed at the end of the chapter. Chapter 7 addresses a different area of high temperature fracture of bond coats, which becomes relevant in terms of determination of brittle to ductile transition temperature (BDTT) in notched specimen and in evaluating topography after failure across this temperature range. This set of tests is designed to measure fracture toughness and study the fracture mode along the temperature scale to exactly identify the BDTT for a given bond coat composition and strain rate, below which the coating undergoes brittle catastrophic fracture and beyond which it creeps and relaxes plastically at very low stresses. Notched free¬standing bond coat specimens are pulled in uni-axial tension to fracture and the stress at failure is used to calculate the average fracture toughness of the bond coat. The stress-strain curve shows linear elastic behavior upto the BDTT of the bond coat as expected, beyond which it becomes increasingly plastic. The KIC is seen to rise marginally upto 750˚C beyond which it showed a significant increase, from which the BDTT was calculated to be ~775˚C for notched samples. The KIC is not reported beyond the BDTT due to irrelevance of LEFM after macroscopic plasticity sets in. Fracture mode is seen to change from transgranular cleavage below the BDTT to void coalescence and ductile rupture beyond it. The experimental challenges, differences in the through thickness KIC’s obtained from tensile tests vis a vi bend tests (due to changing stress states and size scales), as well as mechanisms of ductile to brittle transition in the context of previously available literature are discussed. Chapter 8 gives the closure and important conclusions from the present work. It summarises the key results from the testing technique and highlights the proposed mechanisms which bring about a rising fracture toughness with both increasing Ni:Al ratio across the bond coat cross-section and across individual micro-beams themselves. Some new techniques and geometries which can be adopted for fracture property determination, on which work was initiated but not complete, are also proposed. The last part of the chapter deals with the future implications of the results found and some open threads and challenges on bond coat optimisiation for different properties, which are yet to be dealt with.