Rozprawy doktorskie na temat „Thermal and optical stress”
Kliknij ten link, aby zobaczyć inne rodzaje publikacji na ten temat: Thermal and optical stress.
Utwórz poprawne odniesienie w stylach APA, MLA, Chicago, Harvard i wielu innych
Sprawdź 50 najlepszych rozpraw doktorskich naukowych na temat „Thermal and optical stress”.
Przycisk „Dodaj do bibliografii” jest dostępny obok każdej pracy w bibliografii. Użyj go – a my automatycznie utworzymy odniesienie bibliograficzne do wybranej pracy w stylu cytowania, którego potrzebujesz: APA, MLA, Harvard, Chicago, Vancouver itp.
Możesz również pobrać pełny tekst publikacji naukowej w formacie „.pdf” i przeczytać adnotację do pracy online, jeśli odpowiednie parametry są dostępne w metadanych.
Przeglądaj rozprawy doktorskie z różnych dziedzin i twórz odpowiednie bibliografie.
1
Kylner, Carina. "Light scattering for analysis of thermal stress induced deformation in thin metal films". Doctoral thesis, KTH, Fysik, 1997. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2547.
Pełny tekst źródłaStreszczenie:
Today, thin film based devices are found in a wide field of applications. The main reasons are that thin film technology enables access to unique physical properties and possibilities to miniaturize devices. Thin film devices are generally described in terms such as electrical, optical and magnetical properties. However, the lifetime of these devices is often limited by mechanical stresses causing plastic deformation. An effect of the plastic deformation is hillocking where isolated features are created on the film surface. The continual need to improve performance, reduce size as well as cost is pushing thin film structures close to or beyond present fundamental understanding. Further progress requires better understanding of basic phenomena where analytical methods for characterization of thin film deformation play a crucial role. To follow the initial hillock formation during thermal treatments it is essential to have a suitable tool for achieving real-time measurements with high sensitivity over a relatively large area that does not considerably affect the film surface. Methods based on light scattering are generally very sensitive to changes in the surface topography and allow contact free measurements at high speed. In this thesis light scattering methods are investigated as tools for stress analysis of thin metal films. Detection and characterization of isolated surface features using angular resolved scattering has been investigated by simulations. Results were used in development of an optical instrument for simultaneous measurements of initial hillocking and changes in overall film stress. The instrument combines light scattering and laser beam deflection techniques. It is shown how the onset of initial hillocking in aluminum films is accompanied by stress relaxation. Real-time dark field microscopy was demonstrated as a technique for analysis of the lateral hillock distribution. Analysis of the distribution show clustering of hillocks which is supposed to be related to the microstructure of the film. It is demonstrated that copper inclusion can be used to strengthen aluminum films to withstand higher stress before hillocking occurs. The copper content also reduces the grain size and thereby the surface roughness, which results in good or even better optical performance than for pure aluminum films.NR 20140805
2
Amazirh, Abdelhakim. "Monitoring crops water needs at high spatio-temporal resolution by synergy of optical/thermal and radar observations". Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30101.
Pełny tekst źródłaStreszczenie:
L'optimisation de la gestion de l'eau en agriculture est essentielle dans les zones semi-arides afin de préserver les ressources en eau qui sont déjà faibles et erratiques dues à des actions humaines et au changement climatique. Cette thèse vise à utiliser la synergie des observations de télédétection multispectrales (données radar, optiques et thermiques) pour un suivi à haute résolution spatio-temporelle des besoins en eau des cultures. Dans ce contexte, différentes approches utilisant divers capteurs (Landsat-7/8, Sentinel-1 et MODIS) ont été developpées pour apporter une information sur l'humidité du sol (SM) et le stress hydrique des cultures à une échelle spatio-temporelle pertinente pour la gestion de l'irrigation. Ce travail va parfaitement dans le sens des objectifs du projet REC "Root zone soil moisture Estimates at the daily and agricultural parcel scales for Crop irrigation management and water use impact: a multi-sensor remote sensing approach" (http://rec.isardsat.com/) qui visent à estimer l'humidité du sol dans la zone racinaire (RZSM) afin d'optimiser la gestion de l'eau d'irrigation. Des approches innovantes et prometteuses sont mises en place pour estimer l'évapotranspiration (ET), RZSM, la température de surface du sol (LST) et le stress hydrique de la végétation à travers des indices de SM dérivés des observations multispectrales à haute résolution spatio-temporelle. Les méthodologies proposées reposent sur des méthodes basées sur l'imagerie, la modélisation du transfert radiatif et la modélisation du bilan hydrique et d'énergie et sont appliquées dans une région à climat semi-aride (centre du Maroc). Dans le cadre de ma thèse, trois axes ont été explorés. Dans le premier axe, un indice de RZSM dérivé de LST-Landsat est utilisé pour estimer l'ET sur des parcelles de blé et des sols nus. L'estimation par modélisation de ET a été explorée en utilisant l'équation de Penman-monteith modifiée obtenue en introduisant une relation empirique simple entre la résistance de surface (rc) et l'indice de RZSM. Ce dernier est estimé à partir de la température de surface (LST) dérivée de Landsat, combinée avec les températures extrêmes (en conditions humides et sèches) simulée par un modèle de bilan d'énergie de surface piloté par le forçage météorologique et la fraction de couverture végétale dérivée de Landsat. La méthode utilisée est calibrée et validée sur deux parcelles de blé situées dans la même zone près de Marrakech au Maroc. Dans l'axe suivant, une méthode permettant de récupérer la SM de la surface (0-5 cm) à une résolution spatiale et temporelle élevée est développée à partir d'une synergie entre données radar (Sentinel-1) et thermique (Landsat) et en utilisant un modèle de bilan d'énergie du sol. L'approche développée a été validée sur des parcelles agricoles en sol nu et elle donne une estimation précise de la SM avec une différence quadratique moyenne en comparant à la SM in situ, égale à 0,03 m3 m-3. Dans le dernier axe, une nouvelle méthode est développée pour désagréger la MODIS LST de 1 km à 100 m de résolution en intégrant le SM proche de la surface dérivée des données radar Sentinel-1 et l'indice de végétation optique dérivé des observations Landsat. Le nouvel algorithme, qui inclut la rétrodiffusion S-1 en tant qu'entrée dans la désagrégation, produit des résultats plus stables et robustes au cours de l'année sélectionnée. Dont, 3,35 °C était le RMSE le plus bas et 0,75 le coefficient de corrélation le plus élevé évalués en utilisant le nouvel algorithmeOptimizing water management in agriculture is essential over semi-arid areas in order to preserve water resources which are already low and erratic due to human actions and climate change. This thesis aims to use the synergy of multispectral remote sensing observations (radar, optical and thermal data) for high spatio-temporal resolution monitoring of crops water needs. In this context, different approaches using various sensors (Landsat-7/8, Sentinel-1 and MODIS) have been developed to provide information on the crop Soil Moisture (SM) and water stress at a spatio-temporal scale relevant to irrigation management. This work fits well the REC "Root zone soil moisture Estimates at the daily and agricultural parcel scales for Crop irrigation management and water use impact: a multi-sensor remote sensing approach" (http://rec.isardsat.com/) project objectives, which aim to estimate the Root Zone Soil Moisture (RZSM) for optimizing the management of irrigation water. Innovative and promising approaches are set up to estimate evapotranspiration (ET), RZSM, land surface temperature (LST) and vegetation water stress through SM indices derived from multispectral observations with high spatio-temporal resolution. The proposed methodologies rely on image-based methods, radiative transfer modelling and water and energy balance modelling and are applied in a semi-arid climate region (central Morocco). In the frame of my PhD thesis, three axes have been investigated. In the first axis, a Landsat LST-derived RZSM index is used to estimate the ET over wheat parcels and bare soil. The ET modelling estimation is explored using a modified Penman-Monteith equation obtained by introducing a simple empirical relationship between surface resistance (rc) and a RZSM index. The later is estimated from Landsat-derived land surface temperature (LST) combined with the LST endmembers (in wet and dry conditions) simulated by a surface energy balance model driven by meteorological forcing and Landsat-derived fractional vegetation cover. The investigated method is calibrated and validated over two wheat parcels located in the same area near Marrakech City in Morocco. In the next axis, a method to retrieve near surface (0-5 cm) SM at high spatial and temporal resolution is developed from a synergy between radar (Sentinel-1) and thermal (Landsat) data and by using a soil energy balance model. The developed approach is validated over bare soil agricultural fields and gives an accurate estimates of near surface SM with a root mean square difference compared to in situ SM equal to 0.03 m3 m-3. In the final axis a new method is developed to disaggregate the 1 km resolution MODIS LST at 100 m resolution by integrating the near surface SM derived from Sentinel-1 radar data and the optical-vegetation index derived from Landsat observations. The new algorithm including the S-1 backscatter as input to the disaggregation, produces more stable and robust results during the selected year. Where, 3.35 °C and 0.75 were the lowest RMSE and the highest correlation coefficient assessed using the new algorithm
3
Schulze, Christopher A. [Verfasser]. "Minimizing Thermal Stress in Glass Production Processes : Model Reduction and Optimal Control / Christopher A Schulze". Aachen : Shaker, 2007. http://d-nb.info/1166509206/34.
Pełny tekst źródła
4
Åberg, Jonas. "On the Experimental Determination of Damping of Metals and Calculation of Thermal Stresses in Solidifying Shells". Doctoral thesis, KTH, Materialvetenskap, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4038.
Pełny tekst źródłaStreszczenie:
This thesis explores experimentally and theoretically two different aspects of the properties and behaviour of metals: their ability to damp noise and their susceptibility to crack when solidifying. The first part concerns intrinsic material damping, and is motivated by increased demands from society for reductions in noise emissions. It is a material’s inherent ability to reduce its vibration level, and hence noise emission, and transform its kinetic energy into a temperature increase. To design new materials with increased intrinsic material damping, we need to be able to measure it. In this thesis, different methods for measurement of the intrinsic damping have been considered: one using Fourier analysis has been experimentally evaluated, and another using a specimen in uniaxial tension to measure the phase-lag between stress and strain has been improved. Finally, after discarding these methods, a new method has been developed. The new method measures the damping properties during compression using differential calorimetry. A specimen is subjected to a cyclic uniaxial stress to give a prescribed energy input. The difference in temperature between a specimen under stress and a non-stressed reference sample is measured. The experiments are performed in an insulated vacuum container to reduce convective losses. The rate of temperature change, together with the energy input, is used as a measure of the intrinsic material damping in the specimen. The results show a difference in intrinsic material damping, and the way in which it is influenced by the internal structure is discussed. The second part of the thesis examines hot cracks in solidifying shells. Most metals have a brittle region starting in the two-phase temperature range during solidification and for some alloys this region extends as far as hundreds of degrees below the solidus temperature. To calculate the risk of hot cracking, one needs, besides knowledge of the solidifying material’s ability to withstand stress, knowledge of the casting process to be able to calculate the thermal history of the solidification, and from this calculate the stress. In this work, experimental methods to measure and evaluate the energy transfer from the solidifying melt have been developed. The evaluated data has been used as a boundary condition to numerically calculate the solidification process and the evolving stress in the solidifying shell. A solidification model has been implemented using a fixed-domain methodology in a commercial finite element code, Comsol Multiphysics. A new solidification model using an arbitrary Lagrange Eulerian (ALE) formulation has also been implemented to solve the solidification problem for pure metals. This new model explicitly tracks the movement of the liquid/solid interface and is much more effective than the first model.QC 20100929
5
Lankford, Maggie E. "Measurement of Thermo-Mechanical Properties of Co-Sputtered SiO2-Ta2O5 Thin Films". University of Dayton / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1627653071556618.
Pełny tekst źródła
6
Kravchenko, Grygoriy A. "Crack patterns in thin films and X-ray optics thermal deformations". [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002770.
Pełny tekst źródła
7
Yi, Duo. "Intégration de capteurs à fibre optique par projection thermique pour des applications de contrôle de structures intelligentes". Thesis, Belfort-Montbéliard, 2016. http://www.theses.fr/2016BELF0285/document.
Pełny tekst źródłaStreszczenie:
Ce mémoire présente la modélisation, la simulation, l’expérimentation et la conception d’une structure composite intelligente pour des mesures de haute température (jusqu’à 300 °C). Pour ce faire, une fibre à revêtement métallique, particulièrement résistante pour de tels niveaux thermiques, a été considérée et intégrée au sein d’un revêtement d'alumine. La structure composite intelligente se compose alors du substrat, du dépôt et d’un capteur à fibre optique à modulation d’intensité. Pour mener cette étude, une estimation des flux thermiques basée sur le thermogramme expérimental s’est révélée nécessaire afin d’alimenter un modèle numérique. Différents modèles ont ensuite été construits afin d’évaluer les niveaux de températures atteints en surface ainsi que les niveaux de contraintes au sein même du composite. La simulation a montré que le dépôt pouvait thermiquement être considéré comme une couche mince et que la diffusion de la chaleur au sein du dépôt et du substrat était rapide et pouvait être estimée à l'échelle de la milliseconde. La répartition des contraintes est comme on pouvait s'y attendre dépendante du flux incident mais aussi de la géométrie globale du composite. Les contraintes restent relativement uniformes lors de l'échauffement et durant leur propagation mais s’intensifient après le refroidissement. Il s'avère également que les contraintes résultantes ne sont pas symétriques dans la fibre et sont dépendantes de la position de la fibre par rapport au substrat. Après une phase de modélisation des niveaux thermiques et des contraintes susceptibles d’être atteints au sein du matériau, une phase expérimentale consistant à intégrer une fibre optique non fonctionnalisée dans un dépôt d’alumine a donc été réalisée. Les observations microscopiques en surface et en coupe ont été effectuées afin de vérifier l’intégrité de la fibre intégrée. L’adhérence mécanique des fibres a ensuite été mesurée ainsi que l’atténuation optique pendant le processus d’intégration et le comportement thermique de l’ensemble durant des cyclages thermiques. Enfin, un capteur à fibre optique à modulation d’intensité a été conçu par intégration dans un dépôt céramique réalisé par projection thermique. Un système de mesure de la température a donc été construit et les premiers essais de réponse thermique ainsi que le cyclage thermique du capteur de température ont été effectués et analysés. En concluision, cette étude démontre la faisabilité d’une structure composite intelligente par intégration d'un capteur à modulation d’intensité à fibre optique dans un dépôt céramique élaboré par projection thermique susceptible de pouvoir travailler jusqu’à des températures de 300 °CThis paper presents the modeling, simulation, experimentation and design of a smart composite structrure for high temperature measurements (up to 300 °C). In order to achieve this goal, a high temperature resistant metal coated optical fiber was considered and integrated into alumina coating. The smart composite structure consists of a substrate, a coating and an intensity modulated optical fiber temperature sensor. Firstly, an estimation of heat flux based on a experimental thermogram was firstly carried out in order to feed a numerical modeling. Then, different modelings were built to evaluate the surface temperature levels as well as the composite stress levels. The simulation showed that the composite (substrate and coating) could be considered as a thermally thin medium, the heat propagation within the composite was fast and could be estimated at a scale of millisecond. The stresses remained relatively uniform during the heating process but intensified during the cooling process. The modeling also showed that the stresses are not symmetrical in the fiber and depend on the position of the fiber relative to the substrate. After a modeling evaluation of the thermal levels as well as the stresses that may be achieved in the composite, an experimental step integrating a optical fiber into a thermal coating was carried out. Microscopic observation of surface and cross section were conducted in order to analyze the characteristics of the integrated fiber. The mechanical strength of the integrated fiber was then measured and the optical attenuation during the integration process as well as the thermal behavior of the integrated fiber during the thermal cycling were evaluated. Finally, an intensity modulated optical fiber temperature sensor was designed and integrated into ceramic coating by thermal spraying. A temperature measuring system was designed and the first tests of the thermal response as well as thermal cycling of temperature sensor were carried out. This study demonstrates the feasibility of designing a high temperature resistant smart composite structure by integrating an intensity modulated optical fiber temperature sensor in a ceramic coating elaborated by thermal spraying
8
Zhang, Bufa. "Optical methods of thermal diffusivity measurement". Thesis, London South Bank University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336374.
Pełny tekst źródła
9
Vuppala, Archana. "Thermal and thermal stress analyses of the state-changing tooling". abstract and full text PDF (free order & download UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1460787.
Pełny tekst źródła
10
Sun, Mengyue SUN. "Optical sensor for normal stress distribution". University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1525432600494617.
Pełny tekst źródła
11
Koetniyon, Saiprasit. "Thermal stress analysis of automotive disc brakes". Thesis, University of Leeds, 2000. http://etheses.whiterose.ac.uk/2938/.
Pełny tekst źródłaStreszczenie:
A brake disc rotor forms pan of a foundation brake and rotates with the wheel hub assembly. The main function of a foundation brake is to generate a retarding torque by converting mechanical energy to thermal energy by virtue of the frictional work done in relative sliding at the rotor-pad interface. In practice, most brake discs arc made from cast iron and in use arc sometimes subjected to high thermal stresses which can lead to permanent plastic deformation and occasionally rotor cracking. The aim of the present work is to investigate the thermal response of such a cast iron brake disc using the finite element (FE) method. One particular existing brake disc design for a medium passenger car was chosen for the investigation. This is a "back-vented" disc designed to minimise disc coning but the present work also includes an investigation of a conventional "frontvented" disc similar in dimension to the back-vented disc but with different detailed geometry. Experimental work was undertaken to derive the rotor material properties in tension and compression as a function of temperature. This data was used to generate suitable FE material model routines which accurately allow for the different temperature-dependent yield properties of cast iron in tension and compression. The modelling work highlights the role of the rotor geometry in controlling the thermal response of the structure but. more importantly, the necessity for an accurate material model is illustrated, particularly with regard to its ability to predict the accumulation of plastic strain which may lead to rotor cracking. Using the most accurate user developed material subroutine, the thermal response of the back-and front-vented disc designs are compared: the back-vented disc suffers lower thermal distortion but at the expense of higher plastic strain accumulation, particularly near the point of attachment of the vanes.
12
Hu, Yajie. "Thermal Barrier Coating Modeling for Stress Analysis". Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42668.
Pełny tekst źródłaStreszczenie:
Thermal barrier coatings (TBCs) have been used widely in aerospace and land-based gas turbines. The TBC system consists of a top coat layer, a thermally grown oxide (TGO), a bond coat layer and a substrate. The growth kinetics of the TGO significantly affects the durability of TBCs. At a critical TGO thickness, the growth stresses exceed the ceramic-bond coat interface strength, resulting in TBC system failure. Regardless of the deposition method used, it is vitally important to accurately predict the TBC lifetime by investigating the determinants of the failure. The main objective of this study was to investigate the effect of oxidation stress induced by TGO layer in high temperature cycling environment through a series of reliable numerical simulations. Indeed, this oxidation stress is a known factor of interface degradation, and may result in failure of the ceramic-metal interface.
A 2-D finite element model of the TBC was built via ANSYS APDL software, to conduct parametric studies of increasing complexity. The model accounted for elasticity first, before creep was integrated. Then, the model included swelling induced by phase transformation associated with oxidation, incorporating the effect of volumetric expansion of the newly grown TGO. This coupled oxidation constitutive approach was implemented for a typical air plasma spray deposited TBC coating. The interfacial radial stresses induced by the gradual oxidation were investigated. Different morphologies of the TBC interface were also considered to analyze the roughness effect on interface stresses. A complete model including swelling, creep, aging effects on the TBC layers at a given roughness was finally investigated.
13
Hosie, Andrew. "Differentiating thermal from non-thermal eccrine sweating during exercise and heat stress". Access electronically, 2002. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20041105.114628/index.html.
Pełny tekst źródła
14
Liang, L. H., i Y. G. Wei. "Ultralow Thermal Conductivity and Thermal Stress of Ceramics with Surface Nanowire-structures". Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34880.
Pełny tekst źródłaStreszczenie:
An analytical model on the size and fraction dependent thermal conductivity, elastic modulus and
thermal stress of nanowire-composites are developed, and the theoretical prediction agrees with the experimental
results of Si nanowires. And the model proposes that the high thermal shock strength of ceramics
can be achieved by surface nanostructurization, which is related to the low thermal conductivity and thermal
stress of the nanostructures and voids. The theory will be helpful to guide design of thermal barrier
coatings.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34880
15
Moon, Il Kweon. "Optical performance of bimetallic mirrors in thermal environments". Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/279805.
Pełny tekst źródłaStreszczenie:
Evaluation of the optical performances of bimetallic mirrors with various substrate shapes was conducted using the finite element analysis program, SDRC-IDEAS. In these analyses, two different plating materials, nickel and aluminum were considered for an aluminum and a beryllium mirror substrate. Thermal environments used in this study are: a unit thermal soak (temperature difference), an axial temperature distribution, and radial temperature distributions on the mirror substrate. The goal of this study is to optimize the optical surface quality for various plating thicknessess. Surface errors, individual aberration terms, such as piston, tilts, focus and other aberrations were obtained by the program PCFRINGE. It was found that the optical performances of bimetallic mirrors depend on the plating material, plating thickness, and the mirror substrate materials. The optimum plating thickness combinations were determined based on plating material and mirror substrate with variation of temperature distributions. The results were compared with the optical surface errors and the corrected surface errors. The results indicate that there does not exist a definite common rule for the optimum, but a detailed analysis such as presented herein is generally needed to design bimetallic mirrors in a thermal environment.
16
Roshan, Fekr Masoud. "Stress analysis of an optical ground wire". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0034/NQ64657.pdf.
Pełny tekst źródła
17
Pandhari, Abhijit. "Modeling of thermal stress cycling in refractory materials". Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/62359.
Pełny tekst źródłaStreszczenie:
In metallurgical reactors, the thermal stress field of refractories always changes with the heat transfer conditions at the hot-face. It is suggested that ‘thermally induced refractory cracking’ is often the primary cause of in-service refractory failure but quantitative support for this is lacking. The current work is focussed on studying this aspect by developing an experimentally validated thermomechanical model that considers refractory strength degradation under repeated thermal cycling.
A thermo-mechanical model has been developed with ABAQUS to predict thermal stress and damage in a refractory specimen subjected to thermal cycling. An experiment based on the “contact-conduction method” that uses a hot/cold metal block to heat/cool a refractory specimen was carried out to validate the model. The experiments were run for up to 3-cycles starting from cold- and hot-refractory specimens. Thermocouples were used to gather temperature data from refractory and steel block. An inverse heat conduction model was developed to predict the heat flux applied to the refractory specimen by the steel block based on the temperature history from the steel block. Ultrasonic testing was carried out on the refractory specimens before and after the thermal cycling tests.
The contact-conduction method was successful in creating significant thermal gradients in the refractory specimens. Thermocouples on refractory located at 1cm from the
steel-refractory show temperature variation of about 500°C and 575°C for cold- and
hot-refractory specimen, respectively after 3-cycles.
The model was capable of predicting the temperature changes and damage in the refractory material after multiple cycles. Ultrasonic velocity tests show significant change in the sound velocities in the areas experiencing thermal cycling, indicating significant micro-cracking damage in those areas. It was seen that with multiple cycles the damage penetrated further into the specimen, however the magnitude of the damage does not increase significantly.
Application to an example tundish operation indicated that the model was capable of analyzing an ideal preheating schedule and was capable of predicting the effect of idle time and multiple thermal cycles on the damage in refractories. However, to predict thermal spalling more precisely, an integrated model that considers the effect of thermal gradients, chemical reactions and mechanical loads is needed.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
18
Abedian, Ali. "Thermal stress analysis of unidirectional fiber reinforced composites". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0026/NQ32776.pdf.
Pełny tekst źródła
19
Rao, Hejamadi Dhananjay. "Thermal stress in concrete slabs under different constraints". Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4752.
Pełny tekst źródłaStreszczenie:
Thesis (M.S.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains viii, 127 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 123-126).
20
Walker, Breanna E. "The Effects of Thermal Stress on Balanus glandula". Scholarship @ Claremont, 2013. http://scholarship.claremont.edu/scripps_theses/189.
Pełny tekst źródłaStreszczenie:
Global climate change has become an increasing source of concern due to the recent build-up of greenhouses gases in the atmosphere. The rocky intertidal zone, as the interface between land and sea, is particularly vulnerable to climate change. Many inhabitants of the intertidal zone are sessile and thus experience both terrestrial and aquatic lifestyles at low and high tides, respectively. When emersed at low tide, organisms experience a number of abiotic stresses including heat stress, desiccation stress, and low oxygen availability. Most intertidal organisms have evolved from marine animals and respire most efficiently in water. Barnacles are one such type of intertidal organism. At low tide barnacles face a tradeoff between access to oxygen and loss of water through evaporation. In this study, individuals of the species Balanus glandula, a common intertidal barnacle, were exposed to temperatures of 16°C, 24°C, 30°C, and 35°C for four hours in simulated low tide to determine when aerial respiration occurred. Oxygen levels were measured over the four hours of the exposure and oxygen consumption rates were calculated. Oxygen consumption occurred at all temperatures studied, but the rates at different temperatures were not significantly different from each other. The results showed that barnacles can conduct aerial respiration over the entire course of the low tide exposure despite the risk of desiccation. This indicates that ATP demand remains substantial throughout the low tide and that resorting to anaerobic respiration is not sufficient to meet metabolic needs during low tide exposure.
21
BRAGA, LEDA MARIA PASSOS FARIA. "STRESS ANALYSIS OF THERMAL NATURE UNDER VISCOELATIC BEHAVIOR". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1988. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=19060@1.
Pełny tekst źródłaStreszczenie:
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOEste trabalho apresenta a modelagem teórica e correspondentes soluções numéricas, associadas ao problema de tensões e deformações num cilindro longo de material viscoelástico, submetido a resfriamento em meio homogêneo. Apresentam-se as hipóteses adotadas na caracterização térmica e mecânica do material, bem como procedimentos e resultados experimentais obtidos na aplicação destas suposições e técnicas para a resina poliéster.
The problem of computing stress and strain histories under viscoelastic behaviour in a long cylinder subjected to rapid cooling is considered. The theoretical formulation is presented together with the assumptions made in both thermal and mechanical material characterization. Experimental techniques and results obtained to polyester resin are also presented.
22
URURAHY, MARCELO FERREIRA PINTO. "THEORETICAL-EXPERIMENTAL THERMAL STRESS ANALYSIS IN VISCOELASTIC CYLINDERS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1991. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=19375@1.
Pełny tekst źródłaStreszczenie:
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORApresenta-se neste trabalho o desenvolvimento de um modelo teórico-numérico baseado na Teoria da Viscoelasticidade Linear capaz de prever as distribuições transientes e residuais das componentes de tensão e de deformação de um cilindro polimérico longo submetido a resfriamento brusco. Descrevem-se, ainda, os procedimentos experimentais adotados como intuito de se determinarem algumas propriedades térmicas e mecânicas do sistema epóxi DER331/XG0103/XB81215. Finalmente, comparam-se os resultados fornecidos pelo modelo teórico-numérico com resultados experimentais obtidos através da utilização de uma técnica extensométrica conhecida como Método de Sachs.
This work presents the development of a theoretical and numerical model based on the Linear Viscoelastic Theory able to predict the transient and residual stress and deformation distributions in a long polymeric cylinder subject to a rapid cooling. The work describes the experimental procedures adopted aiming to determine some thermal and mechanical properties of the epoxy system DER331/XG0103/XB81215. Finally, the results from the theoretical numerical model are compared to the ones obtained experimentally by na extensometric technique known as Sachs’ Method.
23
Ntsoane, T. P. "Residual stress in Pt coatings under thermal influence". Master's thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/8778.
Pełny tekst źródłaStreszczenie:
Includes bibliographical references.Resistance thermometers are commonly employed when accurate temperature measurements are required. The detection part consists of a thin metallic film deposited on a ceramic substrate. In this work, commercially manufactured Pt-Al₂O₃ composites annealed at 0°C, 300°C, 600°C and 1170°C above room temperature were investigated for residual stress using the non-destructive X-ray diffraction technique. The apparatus used for the investigation was a Ψ-goniometer with a scintillation detector. The measured data were analysed with "sin²Ψ"-method. The total stress yielded was found to be a superposition of both the thermal and intrinsic stress in the layer. Analytical model, following the method of Tsui and Clyne, was used to resolve the two stress contributions. With the thermal component being constant, the variation of the observed total stress was attributed to the relaxing intrinsic components. Further investigations of the samples included the microstructure studies using Scanning Electron Microscopy (SEM).
24
Morris, Nathan Bradley. "Physical and physiological considerations for mitigating thermal stress". Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/17916.
Pełny tekst źródłaStreszczenie:
To determine the type of intervention which best mitigates thermal stress within a given context, two important factors need to be taken into account: the specific characteristics of the ambient environment (temperature, humidity, air speed and mean radiant temperature) and how the thermoregulatory control system will detect and potentially physiologically compensate the applied intervention. The purpose of the present thesis was to further explore these concepts and apply newly generated knowledge to the presently pressing context of human adaptation to heatwaves. The purpose of Studies 1-3 was to further mechanistically explore and characterise how the body detects and counteracts exogenous cooling and heating loads applied internally. Specifically, study 1 sought to confirm the existence of visceral thermoreceptors, which limit the effectiveness of cold fluid ingestion to defend against heat stress, by investigating whether hot and cold fluid ingestion modifies cold-defense thermoeffectors, independently of differences in core and skin temperature. The aim of Study 2 was to determine whether these thermoreceptors could adequately detect and counteract the relatively large internal heat sink provided by ice slurry ingestion by reducing whole-body heat loss responses during exercise. Study 3, investigated whether hot and cold fluid ingestion prior to a bout of exercise could delay the onset of sweating and vasodilation responses, independently of differences in core and skin temperature. Next, study 4 examined how ambient temperature, humidity and air speed interact to modify heat balance in distinctly different, but commonly experienced, simulated heatwave conditions. Finally, study 5 combined the information from studies 1-4 in order to determine the optimal cooling strategies during hot-dry heatwave conditions which could be applied in isolation or in conjunction with electric fan use and readily-available tap water.
25
Radhakrishnan, Sadhana. "Stress Analysis of Embedded Devices Under Thermal Cycling". PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4075.
Pełny tekst źródłaStreszczenie:
Embedded active and passive devices has been increasingly used by in order to integrate more functions inside the same or smaller size device and to meet the need for better electrical performance of the component assemblies.
Solder joints have been used in the electronic industry as both structural and electrical interconnections between electronic packages and printed circuit boards (PCB). When solder joints are under thermal cyclic loading, mismatch in coefficients of thermal expansion (CTE) between the printed circuit boards and the solder balls creates thermal strains and stresses on the joints, which may finally result in cracking. Consequently, the mechanical interconnection is lost, leading to electrical failures which in turn causes malfunction of the circuit or whole system.
When a die is embedded into a substrate, Young's modulus of the die is larger than one of the core of the substrate and the CTEs of the die is smaller than those of the substrate. As a result, mismatch in coefficients of thermal expansions (CTE) between the substrate with the embedded device and the solder balls may increase.
In the present study, finite element method (FEM) is employed to find out the stress and strain distribution of ball grid array(BGA) solders under thermal cycling. The ANAND model for viscoplasticity is employed for this purpose.
26
Daniel, Gwenaelle Monique. "Optical and thermal transport modelling of laser-tissue interaction". Thesis, University of the West of England, Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392811.
Pełny tekst źródła
27
Wolters, Stephen D. "Thermal infrared and optical observations of near-Earth asteroids". Thesis, Open University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437781.
Pełny tekst źródła
28
Johnson, Jeremy A. (Jeremy Andrew). "Optical characterization of complex mechanical and thermal transport properties". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68543.
Pełny tekst źródłaStreszczenie:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2011.Page 176 blank. Cataloged from PDF version of thesis.
Includes bibliographical references (p. 163-175).
Time-resolved impulsive stimulated light scattering (ISS), also known as transient grating spectroscopy, was used to investigate phonon mediated thermal transport in semiconductors and mechanical degrees of freedom linked to structural relaxation in supercooled liquids. In ISS measurements, short optical pulses are crossed to produce a periodic excitation profile in or at the surface of the sample. Light from a probe beam that diffracts off the periodic material response is monitored to observe the dynamics of interest. A number of improvements were put into practice including the ability to separate so-called amplitude and phase grating signal contributions using heterodyne detection. This allowed the measurement of thermal transport in lead telluride and gallium arsenide-aluminum arsenide superlattices, and also provided the first direct observation of the initial crossover from diffusive to ballistic thermal transport in single crystal silicon and gallium arsenide at room temperature. Recent first-principles calculations of the thermal conductivity accumulation as a function of phonon mean free path allowed direct comparison to our measured results. In an effort to test theoretical predictions of the prevailing first principles theory of the glass transition, the mode coupling theory (MCT), photoacoustic measurements throughout much of the MHz acoustic frequency range were conducted in supercooled liquids. Longitudinal and shear acoustic waves were generated and monitored in supercooled liquid triphenyl phosphite in order to compare the dynamics. An additional interferometric technique analogous to ISS was developed to probe longitudinal acoustic waves at lower frequencies than was typically accessible with ISS. Lower frequency acoustic data were collected in supercooled tetramethyl tetraphenyl trisiloxane in conjunction with piezotransducer, ISS, and picosecond ultrasonics measurements to produce the first truly broadband mechanical spectra of a viscoelastic material covering frequencies continuously from mHz to hundreds of GHz. This allowed direct testing of the MCT predicted connection between fast and slow relaxation in supercooled liquids. Measurements of the quasi-longitudinal speed of sound in the energetic material cyclotrimethylene trinitramine (RDX) were also performed with ISS and picosecond ultrasonics from 0.5 to 15 GHz in order to resolve discrepancies in published low and high frequency elastic constants.
by Jeremy A. Johnson.
Ph.D.
29
Magnabosco, Marina. "Self localization and mapping using optical and thermal imagery". Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/6704.
Pełny tekst źródłaStreszczenie:
Given a mobile robot starting from an unknown position in an unknown environment, with
the task of explores the surroundings, it has to be able to build an environmental map and
localize itself inside that map. Achieving a solution of this problem allows the exploration of
area that can be dangerous or inaccessible for humans.
In our implementation we decide to use two primary sensors for the environment
exploration: an optical and a thermal camera. Prior work on the combined use of optical and
thermal sensors for the Simultaneous Localization And Mapping (SLAM) problem is limited.
The innovative aspect of this work is based on this combined use of a secondary thermal
camera as an additional visual sensor for navigation under varying environmental conditions.
A secondary innovative aspect is that we focus our attention on both cameras, using them as
two separate and independent sensors and combine the information in the final stage of
environmental mapping.
During the mobile robot navigation the two cameras capture images on the environment
and SURF feature points are extracted and matched between successive scenes. Using a prior
work on bearing-only SLAM approach as a reference, a feature initialization method is
implemented and allows each new good candidate feature (optical or thermal) to be
initialized with a sum of Gaussians that represents a set of possible spatial positions of the
detected feature. Using successive observations, is possible to estimate the environment
coordinates of the feature and adding it to the Extended Kalman Filter (EKF) dynamic state
vector. The EKF state vector contains the information about the position of the 6 degree of
freedom mobile robot and the environmental landmark coordinates. The update of this
information is managed by the EKF algorithm, a statistical method that allows a prediction of
the state vector and it updates based on sensor information available.
The final methodology is tested in indoor and outdoor environments with several different
light conditions and robot trajectories producing results that are robust in terms of noise in the
images and in other sensor data (i.e. encoders and GPS). The use of the thermal camera
improves the number of landmarks detected during the navigation adding useful information
about the explored area.
30
Evans, Craig A. "The optical and thermal properties of quantum cascade lasers". Thesis, University of Leeds, 2008. http://etheses.whiterose.ac.uk/5079/.
Pełny tekst źródłaStreszczenie:
The optical and thermal properties of quantum cascade lasers (QCLs) are investigated through the development of comprehensive theoretical models. The optical properties of various multilayer quantum cascade laser waveguides are investigated by solving Maxwell’s equations using a transfer-matrix method. The complex material refractive indices are calculated using a Drude-Lorentz model which takes into account both phonon and plasma contributions to the material properties. A Caughey-Thomas-like mobility model is used to estimate the temperature dependence of the electron mobility which is found to have a significant effect on the optical waveguide properties. The incorporation of this effect leads to better agreement with experimentally measured threshold current densities. In order to investigate the thermal properties of QCLs, a multi-dimensional anisotropic heat diffusion model is developed which includes temperature-dependent material parameters. The model is developed using finite-difference methods in such a way that is can be solved in both the time-domain and in the steady-state. Various heat management techniques were compared in the time-domain in order to extract the heat dissipation time constants. In the steady-state, the model is used to extract the temperature dependence of the cross-plane thermal conductivity of a GaAs-based THz QCL and compare the thermal properties of THz and InP-based mid-infrared QCL optical waveguides. In addition, fully self-consistent scattering rate equation modelling of carrier transport in short-wavelength QCLs is carried out in order to understand the internal carrier dynamics. This knowledge is then used to optimise the device design and the model predicts significant improvements in the performance of the optimised device.
31
Šumić, Mersiha. "Thermal Performance of a Solarus CPC-Thermal Collector". Thesis, Högskolan Dalarna, Energi och miljöteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:du-14526.
Pełny tekst źródłaStreszczenie:
The aim of this master thesis is an investigation of the thermal performance of a thermal compound parabolic concentrating (CPC) collector from Solarus. The collector consists of two troughs with absorbers which are coated with different types of paint with unknown properties. The lower and upper trough of the collector have been tested individually. In order to accomplish the performance of the two collectors, a thorough literature study in the fields of CPC technology, various test methods, test standards for solar thermal collectors as well as the latest articles relating on the subject were carried out. In addition, the set‐up of the thermal test rig was part of the thesis as well. The thermal performance was tested according to the steady state test method as described in the European standard 12975‐2. Furthermore, the thermal performance of a conventional flat plate collector was carried out for verification of the test method. The CPC‐Thermal collector from Solarus was tested in 2013 and the results showed four times higher values of the heat loss coefficient UL (8.4 W/m²K) than what has been reported for a commercial collector from Solarus. This value was assumed to be too large and it was assumed that the large value was a result of the test method used that time. Therefore, another aim was the comparison of the results achieved in this work with the results from the tests performed in 2013. The results of the thermal performance showed that the optical efficiency of the lower trough of the CPC‐T collector is 77±5% and the corresponding heat loss coefficient UL 4.84±0.20 W/m²K. The upper trough achieved an optical efficiency of 75±6 % and a heat loss coefficient UL of 6.45±0.27 W/m²K. The results of the heat loss coefficients are valid for temperature intervals between 20°C and 80°C. The different absorber paintings have a significant impact on the results, the lower trough performs overall better. The results achieved in this thesis show lower heat loss coefficients UL and higher optical efficiencies compared to the results from 2013.
32
Boussoufi, Félix. "Nanocristaux semi-conducteurs colloïdaux pour dispositifs opto-électroniques : synthèse et stabilité sous contraintes thermiques et optiques". Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS231.
Pełny tekst źródłaStreszczenie:
Les nanocristaux semi-conducteurs colloïdaux sont devenus durant ces trente dernières années une classe de matériaux pouvant adresser de nouvelles solutions technologiques pour un grand nombre d’applications : diodes électroluminescentes, panneaux solaires, photodétecteurs infrarouges, systèmes d’imagerie médicale, etc. Néanmoins ces nanocristaux sont confrontés à une faible stabilité de leurs propriétés opto-électroniques face à des contraintes externes (chaleur, lumière, humidité, oxygène), limitant leur utilisation dans de nombreuses applications. Il est donc aujourd’hui nécessaire d’étudier les phénomènes physico-chimiques à l’origine des dégradations des nanocristaux sous contraintes externes et de proposer des solutions pour améliorer leur stabilité. L’objectif premier de cette thèse a été de développer une encre de quantum dots de sulfure de plomb (QDs PbS) pour une intégration dans un photodétecteur proche infrarouge, avec des propriétés opto-électroniques stables sous contrainte thermique (150 °C pendant 3 h). Une étude sur des films de QDs PbS stabilisés par des ligands halogénés, NH4I et PbX2 (X = I, Br), a d’abord été réalisée. Les propriétés optiques et de photoconductions se dégradent rapidement sous l’effet de la chaleur, principalement à cause de la formation d’une phase parasite de Pb5S2I6 et à la coalescence des nanocristaux. Une encre de QDs PbS stabilisés par des précurseurs de pérovskite de CsPbI3 a par la suite été développée. Cette formulation permet d’obtenir des films de nanocristaux plus stables thermiquement, avec des propriétés optiques, structurales et de photoconductions mieux conservées. Ces films de QDs PbS-CsPbI3 ont pu être intégrés dans un photodétecteur proche infrarouge (940 nm) type photodiode, démontrant une efficacité quantique externe de près de 49 % et un courant d’obscurité de 10-5 A/cm2, après avoir subi le traitement thermique de 150 °C pendant 3 h. En dernier lieu, une méthode d’encapsulation par atomisation-séchage de nanocristaux de pérovskite CsPbBr3 dans des billes de polymère acrylates est présentée. Les billes composites possèdent un rendement quantique de photoluminescence de 35 % avec un pic de fluorescence à 518 nm et une largeur à mi-hauteur de 22 nm. L’encapsulation des nanocristaux permet une amélioration de leur photostabilité, avec une émission stable après 200 h sous illumination continue dans un dispositif convertisseur de lumière LED/nanocristauxColloidal semiconductor nanocrystals have become during the last thirty years a class of materials that can address new technological solutions for many applications, such as light emitting diodes, solar cells, infrared photodetectors, medical imaging systems, etc. Nevertheless, these nanocrystals suffer from poor stability against external stress (heat, light, humidity, oxygen), limiting their use in many applications. Today, it is therefore necessary to study the physicochemical phenomena at the origin of their degradation and to propose new solutions to improve their stability. The main objective of this thesis was to develop an ink of lead sulfide quantum dots (PbS QDs) for a near-infrared photodetector, with stable optoelectronic properties under thermal stress (150 °C for 3 h). The manuscript first presents a study of nanocrystals films made of PbS QDs capped with halide ligands, NH4I and PbX2 (X = I, Br). The optical and photoconductive properties degrade rapidly under the effect of heat, mainly because of the formation of a Pb5S2I6 parasitic phase and of the coalescence of the nanocrystals. An ink of PbS QDs stabilized by CsPbI3 perovskite precursors was subsequently developed. This formulation provides more thermally stable nanocrystal films with better preserved optical, structural and photoconductive properties. These PbS-CsPbI3 QDs films were integrated into a near-infrared (940 nm) photodiode-type photodetector, demonstrating an external quantum efficiency of nearly 49% and a dark current of 10-5 A/cm2, after undergoing the thermal treatment of 150 °C for 3 h. Finally, a spray-drying polymer encapsulation method for CsPbBr3 perovskite nanocrystals is presented. The composite beads, made of acrylate-based polymers, possess a photoluminescence quantum yield of 35% with a fluorescence peak at 518 nm and a half-value width of 22 nm. The encapsulation of the nanocrystals allows an improvement of their photostability, with a stable green emission after 200 h under continuous illumination in an LED/nanocrystal downconverter device
33
Lu, Kaichang. "Design problems in infra-red optical systems". Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339522.
Pełny tekst źródła
34
Mallick, Vishal. "Stress analysis of metal/CFRP adhesive joints subjected to the effects of thermal stress". Thesis, University of Bristol, 1989. http://hdl.handle.net/1983/4b861d50-c290-4ea9-a3ac-94d9b39dfaa6.
Pełny tekst źródła
35
Cockcroft, Steven Lee. "Thermal stress analysis of fused-cast Monofrax-S refractories". Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/30991.
Pełny tekst źródłaStreszczenie:
Mathematical models of heat flow and elastic stress generation based on the finite-element method have been developed and utilized to analyze the Epic-3 Monofrax-S casting process (Monofrax-S is primarily composed of 47-57% A1₂O₃, 34-41% ZrO₂ and 10-15% SiO₂). The results of the mathematical analysis, in conjunction with information obtained from a comprehensive
industrial study, has led to the development of mechanisms for the formation of the various
crack types found in this casting process. Thermal stresses have been predicted to be generated early in the solidification process in association with rapid cooling of the refractory surface as it contacts the initially cool mould and again later in the solidification process in conjunction
with the tetragonal-to-monoclinic phase transformation which occurs in the zirconia component of Monofrax-S. The mathematical analysis has also helped to identify indirectly a potential mechanism for the generation of mechanical stresses. Based on an understanding of the generation of tensile stresses, recommendations have been made for modifications to the moulding
and casting procedures in order to reduce the propensity for the formation of cracks. The modifications have included changes to the mould construction and geometry to reduce the generation of mechanical stresses and changes to the moulding materials to impact on the flow of heat at key times during solidification and cooling. With the recommendations in place, the casting
process has been re-examined with the mathematical models to verify the impact of the modifications.
The predictions show that the modifications have acted to reduce tensile stresses associated with the formation of Type-A and -B cracks. Preliminary industrial trials with the modified mould have yielded blocks free of these defects.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
36
Bosomworth, P. A. "Thermal stress damage resistance of gel-bonded magnesia refractories". Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371841.
Pełny tekst źródła
37
Soomro, A. B. "The generation of thermal stress and strain during quenching". Thesis, Sheffield Hallam University, 1986. http://shura.shu.ac.uk/20385/.
Pełny tekst źródłaStreszczenie:
A viscoelastic-plastic mathematical model was used to calculate the thermal stress and strain generated during the quenching of an infinite plate of high hardenability steel (835M30) in water, oil and Polymer. In the present work the mathematical model was modified to include the effect of initial stress on the rate of stress relaxation, which has been found to be significant. The data required to incorporate this effect into the calculations, were obtained experimentally during the-.present investigation. The effect of an applied stress during transformation (transformation plasticity) was also introduced in the mathematical model. The new model produced a marked improvement in the degree of agreement between the calculated and experimental residual stress, although the corresponding level of agreement in the case of residual strain was less good. In particular, strains after water quenching agreed less well with experiment as a consequence of the change in the model, although this drawback was not found after oil and polymer quenching. The new mathematical model was used to investigate the effect of martempering, section size and transformation temperature range on the generation of thermal stress and strain. A salt bath treatment above the Ms temperature followed by air cooling prevented residual stress development, but an oil quench after the salt bath treatment generated a level of residual stress at the end of cooling that was similar to that obtained after a direct oil quench from 850°C. Neither martempering process was successful in reducing residual strain. With an increase in section size a reduction in the residual stress and an increase in the distortions was obtained after a water quench. However, after oil quenching the overall effect of section size on residual stress and strain was small. The effect of variation in the transformation temperature range was found to be small in the case of residual stress but an increase in Ms temperature produced a significant increase in the level of residual strain.
38
Chen, Chung-Yu, i 陳忠佑. "Thermal Stress Analysis for Multi-Channel MT Ferrule and Optical Design for Optical Fiber Package". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/80989919504515166430.
Pełny tekst źródłaStreszczenie:
碩士國立臺灣科技大學
機械工程系
92
In recent years, the global communication and internet have been more and more popular. In order to support high fiber count and dense optical connection demand for high-power optical fiber delivery system, multi-fiber with SFF (Small Form Factor) will for sure be the optical fiber connectors in the future and the development of MT connectors will especially become the main trend. The end face cracking of multimode optical fiber will likely be created in epoxy-curing, cleaving and polishing during the assembly process of connector and there will be problems of optical coupling and loss. The aim of this research is focused on the optical fiber in epoxy-cured ferrule module of MT connectors, which has been rarely discussed so far. This study applies FEA to investigate optical fiber stress in epoxy-curing ferrule module. In addition, the Taguchi Method can help in understanding the effects of design factors in the process and finding the optimal factor combinations to reduce the rate of defected connector. The optimal results will be verified by the connector assembly experiment. It is found that the thermal stress of optical fiber is in direct proportion to the heating temperature. It is better to keep the heating temperature under 120℃. Residual stress of optical fiber stays constant after cooling for a certain time. The larger size of ferrule or the less optical fiber count in the same size of ferrule, the bigger stress optical fiber will produce. In addition, the Taguchi Method provides a optimal epoxy-curing process parameter to successfully reduce the stress of optical fiber and decrease the time of fabrication. The stress of optical fiber is influenced by a collocation of optical fiber diameter, heating temperature, and cooling time.
39
張振裕. "The thermal stress analysis of the forming mold of glass optical elments". Thesis, 1993. http://ndltd.ncl.edu.tw/handle/23338637118457629891.
Pełny tekst źródła
40
Lin, Chi-Chau, i 林啟超. "The Study on the Stress and Fatigue Life in Ferrule-Epoxy-Fiber Module of Optical Fiber Connector under Thermal Cycling". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/17859809882357740553.
Pełny tekst źródłaStreszczenie:
碩士國立中山大學
機械與機電工程學系研究所
91
The effects of different ferrule length and epoxy layer thickness of the module of optical fiber connector under thermal cycling are investigated in this thesis. The finite element method package, MSC. MARC, is used in this study and the coupled thermal-elastic-plastic model is employed in the analysis. The mechanical behavior and life prediction with different length of ferrule and thickness of epoxy layer are considered. It is shown that the thickness of epoxy layer has the major effect on the life of the module. The stress and strain in the fiber and epoxy layer are decreasing with increasing of ferrule length, and the life of the module is increasing with increasing of thickness of epoxy layer. Finally, we recommend the ferrule length can be designed between 7.89mm ~10.5mm.
41
Mow-Lowry, Conor Malcolm. "Thermal noise and optical cooling". Phd thesis, 2011. http://hdl.handle.net/1885/150253.
Pełny tekst źródłaStreszczenie:
Thermal noise and optical quantum noise place fundamental limits on the displacement sensitivity of interferometric gravitational wave detectors. Projects such as Advanced LIGO employ a wide range of techniques to reduce thermal noise and use very high optical powers to reduce quantum noise. Thermal noise is Brownian motion caused by the thermal energy in each mode of oscillation. It is fundamentally linked with mechanical loss via the fluctuation-dissipation theorem. The thermal energy of, for example, the fundamental resonance of the suspension of a mirror can be concentrated into the resonant peak by using a very high-Q oscillator. This reduces the spectral density of the fluctuations away from resonance. The shape of the thermal noise spectrum depends on the mechanical loss mechanisms, and can have important implications for interferometer design
This thesis presents, to the best of my knowledge, the first off-resonance thermal noise measurement of a high-Q suspension which includes both above-and below-resonance regions. The measurements do not conform to the accepted 'structural' damping model, but rather seem to suit a model with both structural and viscous damping. A number of potentially spurious loss mechanisms were investigated, but none were found to substantially alter the spectral shape of the measured noise. A lower quality factor suspension material was then employed to see if structural damping was dominant, but again a mixed damping model fitted the data better than structural damping. A coating-free mirror was designed and experimentally characterised. Removing the optical coating removes a significant source of mechanical loss from the mirror, potentially improving thermal noise.
The combination of high optical powers and high-Q oscillators can lead to strong opto-mechanical interactions. The light inside an optical resonator can act as a complex spring, modifying both rigidity and damping. For a very low-loss mechanical system, a small amount of optical anti-damping can lead to instability. Conversely, it is possible to optically damp, or 'cool', an oscillator by extracting thermal energy. Results are presented showing optical cooling of the fundamental mode of a mirror suspension down to an effective temperature of 70 mK. This cooling is measured by the direct observation of the thermal noise spectrum. The measured traces are in agreement with a prediction of the thermal noise spectrum based on the input laser power, optical configuration, and feedback control system used. Results from the suspended gravitational wave detector prototype, the Caltech 40m interferometer, show how a strong optical spring creates an opto-mechancial resonance which alters the frequency response of the interferometer.
42
"Stress-engineered optical elements". UNIVERSITY OF ROCHESTER, 2008. http://pqdtopen.proquest.com/#viewpdf?dispub=3300620.
Pełny tekst źródła
43
Hong, C. C., i 洪志強. "INTERLAMINAR STRESS AND THERMAL STRESS ANALYSES OF LAMINATED PLATES". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/18164329162890659488.
Pełny tekst źródłaStreszczenie:
博士國立中興大學
應用數學系
87
In the part of the interlaminar stresses analyses, a stress-function-based variational approach is used to determine the interlaminar stresses in a multilayered strip of laminate subject to arbitrary combinations of axial extension, bending, the steady and the unsteady aerodynamic loading of fluid flow over the upper surface of laminated composite plate. The finite difference method for determining the interlaminar stresses in a laminated strip is used. Symmetric four-layer, cross-ply and angle-ply laminates are considered in detail. Some numerical solutions by using a personal computer are obtained. The present results for four-layer laminates show that the aerodynamic loading has significant effects on the interlaminar stresses near the free-edge regions. In the part of thermal stress analyses, a GDQ (Generalized Differential Quadrature) method is presented for the thermal bending of numerical interlaminar stress and displacement in eight-layer of orthotropic plate with unidirectional, cross-ply and angle-ply laminate under thermally expansion load and uniform transverse load. When the moderately thick of orthotropic, anisotropic, laminated plate is considered, the transverse shear deformation in thermal stress and deflection of bending analysis should be involved.
44
Wen-TungYang i 楊文通. "Analogies between optical and thermal propagation". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/rjwt9f.
Pełny tekst źródłaStreszczenie:
碩士國立成功大學
光電科學與工程學系
105
A analogy between optical and thermal propagation in heterogeneous anisotropic media had been proposed recently. All thermal parameters are related to optical ones in artificial metallic media, thus making possible to use numerical codes developed for optics. Our develops and analyzes a metamaterial for heat dissipation. Similar photonic crystal, some frequency of photonic can penetrate, another frequency of photonic can’t penetrate. Electromagnetic and heat diffusion simulations based on the finite element method (FEM) are accomplished to verify that the design of the proposed film. A decrease of frequency can be achieved high penetration rate.
45
Wang, Jenq-Chyi, i 汪正祺. "Thermal stress analysis of semiconductor wafers in rapid thermal processing". Thesis, 1998. http://ndltd.ncl.edu.tw/handle/88438136622610522548.
Pełny tekst źródłaStreszczenie:
碩士國立成功大學
機械工程學系
86
Thermal stresses are an important consideration in production processes involving large temperature changes. Recently, Thermal stresses have also become significant in semiconductors related to wafers. To calculate the thermal stresses, we analysis four kinds of boundary conditions. This article investigates the thermal stress in a 8 inch wafer with its surfaces subjected to heat radiation. In order to obtain the solution of the governing equation, which is a partial differential equation, the following procedures of analysis are used. 1. Normalize the governing partial differential equation of temperature subject to appropriate initial and boundary conditions. Use finite-difference method to transform the governing equation, initial and boundary conditions. 2. Normalize the governing partial differential equation of stress subject to appropriate initial and boundary conditions. 3. Substitute the temperature distribution into the governing equation of thermal stresses. Then use Simpson， s method to obtain the thermal stress distribution as a function of time and position of the wafer.
46
Abdo, Amr Yehia. "Modeling of the thermal response and the thermal distortion of optical mask during optical lithography exposure process". 1999. http://catalog.hathitrust.org/api/volumes/oclc/44731843.html.
Pełny tekst źródła
47
Huang, Chih-Hung, i 黃志宏. "Thermal Stress Analysis of Electronic Packages". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/83014860367136633742.
Pełny tekst źródłaStreszczenie:
碩士國立交通大學
機械工程系
88
The aim of this study is to investigate the failure behavior induced by thermal cyclic loading of the Thermal -Enhanced PBGA. In this study, thermal stress analyses of Au wire, interfaces of different materials and solder balls are carried out by using ANSYS finite element simulation code. In addition, local heat transfer coefficients distribution is used to simulate conjugate heat transfer problem on the package surfaces. Results show that there are defects happed in some positions contacted with heat spreader. Cracks in the chip corner points and fatigue failure in the edge balls are also predicted by increasing thermal cyclic loading times.
48
Chen, Yao-Shing, i 陳耀星. "Thermal Stress Measurements in Electronics Packages by Piezoresistive Stress Sensor". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/76763367609882783074.
Pełny tekst źródłaStreszczenie:
碩士中正理工學院
電機工程研究所
87
ABSTRACT The purpose of this article is quantitatively extracting the stress distribution in microelectronics packages through in-situ and non-destructive measurements. To this end, the P-type and N-type piezoresistive stress sensors were first designed and manufactured by conventional IC process. Secondly, the stress sensors were packaged and the resistance variations of the sensors were measured at different temperature so that the relationship between stress distribution and temperature were extracted according to the piezoresistive theorem. The experiment results showed that the resistance of the sensors increased with temperature in the range of 30~130℃. For N-type sensors, linear relationships were derived between stress and temperature. However, since unreasonable results were derived from P-type sensors, further study on P-type sensors will be needed. Experiments on power dissipation from the test chips in package were finally performed, and linear curves were derived between stress and the distance from heater to the sensors. It is concluded that N-type piezoresistive stress sensors are able to extract stress in microelectronics packages with good accuracy.
49
Liu, Kun-I., i 劉坤一. "Transient Thermal Stress and Residual Stress analysis in Plate Welding". Thesis, 1993. http://ndltd.ncl.edu.tw/handle/18338594692718581054.
Pełny tekst źródła
50
Liu, Kun-Yi, i 劉坤一. "ransient thermal stress and residual stress analysis in plate welding". Thesis, 1993. http://ndltd.ncl.edu.tw/handle/03654790707247342621.
Pełny tekst źródła