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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Quantifying the cracking behaviour of strain hardening cement-based composites

Nieuwoudt, Pieter Daniel 03 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Strain Hardening Cement Based Composite (SHCC) is a type of High Performance Fibre Reinforced Cement-based Composite (HPFRCC). SHCC contains randomly distributed short fibres which improve the ductility of the material and can resist the full tensile load at strains up to 5 %. When SHCC is subjected to tensile loading, fine multiple cracking occurs that portrays a pseudo strain hardening effect as a result. The multiple cracking is what sets SHCC aside from conventional Reinforced Concrete (RC). Conventional RC forms one large crack that results in durability problems. The multiple cracks of SHCC typically have an average crack width of less than 80 μm (Adendorff, 2009), resulting in an improved durability compared to conventional RC. The aim of this research project is to quantify the cracking behaviour of SHCC which can be used to quantify the durability of SHCC. The cracking behaviour is described using a statistical distribution model, which represents the crack widths distribution and a mathematical expression that describes the crack pattern. The cracking behaviour was determined by measuring the cracks during quasi-static uni-axial tensile tests. The cracking data was collected with the aid of a non-contact surface strain measuring system, namely the ARAMIS system. An investigation was performed on the crack measuring setup (ARAMIS) to define a crack definition that was used during the determination of the cracking behaviour of SHCC. Several different statistical distributions were considered to describe the distribution of the crack widths of SHCC. A mathematical expression named the Crack Proximity Index (CPI) which represents the distances of the cracks to each other was used to describe the crack pattern of SHCC. The Gamma distribution was found to best represent the crack widths of SHCC. It was observed that different crack patterns can be found at the same tensile strain and that the CPI would differ even though the same crack width distribution was found. A statistical distribution model was therefore found to describe the CPI distribution of SHCC at different tensile strains and it was established that the Log-normal distribution best describes the CPI distribution of SHCC. After the cracking behaviour of SHCC was determined for quasi-static tensile loading, an investigation was performed to compare it to the cracking behaviour under flexural loading. A difference in the crack widths, number of cracks and crack pattern was found between bending and tension. Therefore it was concluded that the cracking behaviour for SHCC is different under flexural loading than in tension. / AFRIKAANSE OPSOMMING: “Strain Hardening Cement-based Composite” (SHCC) is ‘n tipe “High Performance Fibre Reinforced Cement-based Composite” (HPFRCC). SHCC bevat kort vesels wat ewekansig verspreid is, wat die duktiliteit van die material verbeter en dit kan die maksimum trekkrag weerstaan tot en met ‘n vervorming van 5 %. Wanneer SHCC belas word met ‘n trekkrag, vorm verskeie fyn krake wat ‘n sogenaamde vervormingsverharding voorstel. Die verskeie krake onderskei SHCC van normale bewapende beton. Normale bewapende beton vorm een groot kraak met die gevolg dat duursaamheidsprobleme ontstaan. Die gemiddelde kraakwydte van SHCC is minder as 80 μm (Adendorff, 2009) en het dus ‘n beter duursaamheid as normale bewapende beton. Die doel van die navorsingsprojek is om die kraak gedrag van SHCC te kwantifiseer en wat dan gebruik kan word om die duursaamheid van SHCC te kwantifiseer. Die kraak gedrag is beskryf deur ‘n statistiese verspreiding model wat die kraak wydtes se verspreiding voorstel en ‘n wiskundige uitdrukking wat die kraak patroon beskryf. Die kraak gedrag was bepaal deur die krake te meet tydens die semi-statiese een-asige trek toetse. Die kraak data was met behulp van ‘n optiese vervormings toestel, naamlik die ARAMIS, versamel. ‘n Ondersoek is gedoen op die kraak meetings opstelling (ARAMIS), om ‘n kraak definisie te definieer wat gebruik is om die kraak gedrag te bepaal. Daar is gekyk na verskeie statistiese verdelings om die kraak wydtes van SHCC te beskryf. Die kraak patroon van SHCC is beskryf met ‘n wiskundige uitdrukking genoem die “Crack Proximity Index” (CPI) wat die krake se afstande van mekaar voorstel. Dit is bevind dat die Gamma verdeling die kraak wydtes van SHCC die beste beskryf. Daar is waargeneem dat verskillende kraak patrone by dieselfde vervorming verkry kan word en dat die CPI kan verskil al is die kraak wydte verdeling dieselfde. ‘n Statistiese verdelingsmodel is dus gevind om die CPI verdeling van SHCC te beskryf by verskillende vervormings, en daar is vasgestel dat die Log-normaal verdeling die CPI verdeling van SHCC die beste beskryf. Nadat die kraak gedrag van SHCC bepaal is vir semi-statiese trek-belasting, is ‘n ondersoek gedoen waar die trek-kraak gedrag vergelyk is met buig-kraak gedrag. ‘n Verskil in die kraak wydtes, aantal krake en kraak patroon is gevind tussen buiging en trek. Dus is die gevolgtrekking gemaak dat die kraak gedrag van SHCC verskillend is in buiging as in trek.
2

The time-dependent cracking behaviour of strain hardening cement-based composite

Adendorff, Christo Johan 12 1900 (has links)
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Strain Hardening Cement-based Composite (SHCC) is part of the High Performance Fibre Reinforced Cement-based Composite (HPFRCC) family and is a relative new concrete composite. This Fibre Reinforced Cement-based Composite (FRCC) contains randomly distributed short fibres and when subjected to a uni-axial tensile load multiple cracking occurs. The multiple cracking generates fine cracks which are normally smaller than 100 μm and achieve a strain capacity of more than 5 %. There are limited publications regarding the research of sustained tensile tests on SHCC and especially the cracking behaviour of SHCC under quasi-static uni-axial as well as sustained tensile loads. The cracking behaviour is described as the average crack width, number of cracks and descriptive statistical properties which could be used to represent the distribution of the multiple fine cracks under uni-axial tension. There are two types of tests that were under consideration to determine the cracking behaviour of SHCC. The first is quasi-static uniaxial tensile tests and the second is sustained tensile tests. The latter was dependant on the uni-axial tensile tests in terms of the sustained load applied. The sustained loads ranged from 40 % to 80 % of the ultimate tensile resistance recorded from the uni-axial tensile tests that correspond with a strain rate of 0.001 /s. Different strain rates were used for the uni-axial tensile tests to determine the effect on the cracking behaviour. The cracking behaviour was determined with the aid of a non-contact optical 3D digital deformation measuring device called ARAMIS. The content of this thesis gives a background study of the cracking behaviour and relevant research performed on SHCC under certain loads as well as some literature about the timedependant effects of a cement-based composite. The functioning of the device called ARAMIS is explained as well as the resulting effects of this device on the preparation of the test specimens. The experimental framework for the uni-axial and sustained tensile tests is discussed. Thereafter, the experimental results of the tests are depicted and discussed. The results shed some light on the basic material properties such as the average ultimate stress and average ultimate strain, Young’s modulus, etc. for the quasi-static tensile tests as well as shrinkage and creep of SHCC. The cracking behaviour such as the average crack width, number of cracks, the variance and skewness of the distribution of the crack widths in the test specimens for the quasi-static uni-axial and sustained tensile tests are depicted and discussed. The cracking behaviour when subjected to uni-axial tensile tests with different strain rates is significantly governed by the formation of new cracks and the average crack width remains small with increase in strain. There is no significant difference for the cracking behaviour found when subjected to different strain rates. However, when SHCC is subjected to a sustained load then the average crack width is dependant on the number of cracks that form over time as well as the load level. The formation of fewer and wider cracks was observed for specimens loaded at average 40 % of the ultimate tensile resistance stress, however at loading percentages of higher than 65 % more cracks developed which resulted in a smaller average crack width. / AFRIKAANSE OPSOMMING: Vervorming Verharding Sement gebaseerde samestelling “Strain Hardening Cement-based Composite” (SHCC) is deel van die familie van “High Performance Fibre Reinforced Cement-based Composite” (HPFRCC) en is ʼn relatiewe nuwe beton samestelling. Hierdie vesel versterkte sement gebaseerde beton bevat willekeurig verspreide kort vesels en veelvoudige klein krake vorm onder monotoniese trekkragte. Hierdie veelvoudige klein krake is minder as 100 μm wyd en lei tot ʼn vervorming van meer as 5 %. Daar is ʼn tekort aan navorsing oor die kruip van SHCC sowel as die kraak gedrag van hierdie sement gebaseerde samestelling onderhewig aan trek. Die kraak gedrag word beskryf as die gemiddelde kraakwydte, aantal krake en ʼn paar beskrywende statistiese parameters. Hierdie kraak gedrag parameters kan gebruik word om ʼn verdeling te kan weergee van die veelvoudige klein krake onder ʼn trek belasting. Twee tipes toetse was uitgevoer om die kraak gedrag te beskryf. Die eerste tipe toets was monotoniese trek toetse en die tweede tipe was kruip toetse. Die tweede toets was afhanklik van die monotoniese trek toetse in terme van die belasting wat gebruik was vir die kruip toetse. Die belasting was gevarieer vanaf 40 % tot 80 % van die breekbelasting wat bepaal is met die monotoniese trektoetse wat ooreenstem met ʼn vervorming tempo van 0.001 /s. Verskillende vervorming tempo’s vir die monotoniese trektoetse was uitgevoer om te bepaal wat die effek is op die kraak gedrag. Die kraak gedrag was bepaal met behulp van ʼn geen-kontak optiese 3D digitale deformasie meet instrument genoem ARAMIS. Die inhoud van die tesis bevat ʼn kort opsoming oor ʼn agtergrond studie van die kraak gedrag en relevante navorsing oor vesel versterkte sement gebaseerde beton, sowel as literatuur oor die tydafhanklike effekte van ʼn sement gebaseerde samestelling. Die beheer en gebruik van die meet instrument ARAMIS word verduidelik, sowel as die effek van hierdie masjien op die voorbereiding vir die eksperimente. Die eksperimentele uiteensetting vir die monotoniese en kruip toetse word beskryf. Daarvolgens is die resultate van die eksperimentele toetse getoon en verduidelik. Die resultate verduidelik die basiese materiaal eienskappe, byvoorbeeld die gemiddelde breekspanning met die ooreenkomstige breekvervorming, Young’s modulus en so voorts vir die monotoniese trektoetse, sowel as eienskappe met betrekking tot krimp en kruip van SHCC. Die kraak gedrag naamlik die gemiddelde kraakwydte, aantal krake per meter, variansie en die skuinsheid van die ontwikkelde krake met die toets proefstukke vir die monotoniese en kruip trek toetse word weergegee en verduidelik. Die kraak gedrag van SHCC wanneer getoets word met verskillende monotoniese trektoets tempo’s word beheer deur die ontwikkeling van nuwe krake en die gemiddelde kraakwydte is beduidend laag met toenemende vervorming. Daar is geen beduidende verskil in die kraak gedrag ten opsigte van die verskillende monotoniese trek tempo’s nie. In teendeel, wanneer SHCC belas word met ʼn konstante las oor tyd word die gemiddelde kraakwydte beheer deur die ontwikkeling van nuwe krake sowel as die belasting wat aangewend is. Onder ʼn belasting van so laag as 40 % van die breekbelasting vorm daar minder krake, maar met ʼn groter gemiddelde kraakwydte. Wanneer belas word met meer as 65 % van die breekbelasting vorm meer krake wat lei tot ʼn kleiner gemiddelde kraakwydte.
3

Aproveitamento do resíduo do coco verde para produção de compósitos destinados à construção rural / Use of green coconut residue for composites production for rural construction

Pereira, Camila Lúcio 09 April 2012 (has links)
A presente tese apresenta a utilização da fibra da casca do coco verde como reforço de matriz cimentícia para produção de fibrocimentos. Embora orgânico, o resíduo do coco verde apresenta difícil degradação e diminuí da vida útil de aterros sanitários e lixões. Para viabilizar o uso do resíduo do coco verde (fibra), como reforço de compósitos, optou-se por realizar tratamentos físico-químicos nas fibras e, substituir parcialmente o cimento Portland por material pozolânico de alta reatividade (cinza da casca de arroz (CCA)) para diminuir o ataque alcalino da matriz sobre a fibra vegetal. O experimento foi dividido em duas etapas, a primeira avaliou a fibra de coco verde com e sem tratamentos e os compósitos produzidos com elas. A segunda etapa analisou a influência de diferentes níveis de substituição do cimento Portland pela cinza da casca de arroz (CCA). Para preparação dos compósitos foi utilizada a técnica de dispersão das matérias-primas em solução aquosa, seguida de drenagem e prensagem, como uma simulação simplificada do processo Hatschek de fabricação industrial. Os compósitos foram analisados aos 28 dias (período de cura úmida) e após os processos de envelhecimento, 100 ciclos de imersão-secagem e 28 dias em banho térmico (65°C). Ensaios físicos e mecânicos avaliaram o desempenho, a resistência e a ductilidade dos compósitos. A termogravimetria permitiu observar o consumo da portlandita e a queda da alcalinidade da matriz com 50% de substituição do cimento Portland pela CCA, sem afetar a resistência do material. Os resultados obtidos indicam que a fibra do coco verde tem grande potencial para ser utilizada como reforço de fibrocimentos, desde que seja incorporada a uma matriz de alcalinidade reduzida. / This thesis studies the use of green coconut fiber as a reinforcer in the matrix cement for the production of fibre-cement. Besides being an organic material, the green coconut residues are not easily degradable, but can reduce the landfills lifespan. To evaluate the possibility of use of coconut residue fiber, as reinforcer in composites, physical-chemical treatments were carried out on the fibers, and partially replacing Portland cement with pozzolanic materials for high reactivity (rice husk ash (RHA)) was also added to decrease the alkaline attack matrix on the plant fiber. The experiment was divided into two stages: the first assessed the green coconut fiber with and without treatment and the composites produced with them. The second stage examined the influence reinforcer high reactivity to allow the use of coconut fiber as reinforcement in cementitious matrix. In the preparation of the composites, the technique of dispersing the materials in aqueous solution was used, followed by draining and pressing, as a simplified simulation Hatschek process of industrial manufacture. The composites were analyzed after 28 days and after an aging process, with 100 cycles of immersion-drying or heating in water for 28 days at 65°C). Physical and mechanical tests were used to e valuated the performance, traction resistance and ductility of the composites. A thermogravimetry test allowed the observation of the use of portlandita and the alkalinity reduction of the matrix with the addition of RHA, without affecting the resistance of the material. The results obtained indicate that the green coconut fiber has great potential to be used as a fibre-cement reinforcer, as long it is included in a matrix with reduced alkalinity.
4

Aproveitamento do resíduo do coco verde para produção de compósitos destinados à construção rural / Use of green coconut residue for composites production for rural construction

Camila Lúcio Pereira 09 April 2012 (has links)
A presente tese apresenta a utilização da fibra da casca do coco verde como reforço de matriz cimentícia para produção de fibrocimentos. Embora orgânico, o resíduo do coco verde apresenta difícil degradação e diminuí da vida útil de aterros sanitários e lixões. Para viabilizar o uso do resíduo do coco verde (fibra), como reforço de compósitos, optou-se por realizar tratamentos físico-químicos nas fibras e, substituir parcialmente o cimento Portland por material pozolânico de alta reatividade (cinza da casca de arroz (CCA)) para diminuir o ataque alcalino da matriz sobre a fibra vegetal. O experimento foi dividido em duas etapas, a primeira avaliou a fibra de coco verde com e sem tratamentos e os compósitos produzidos com elas. A segunda etapa analisou a influência de diferentes níveis de substituição do cimento Portland pela cinza da casca de arroz (CCA). Para preparação dos compósitos foi utilizada a técnica de dispersão das matérias-primas em solução aquosa, seguida de drenagem e prensagem, como uma simulação simplificada do processo Hatschek de fabricação industrial. Os compósitos foram analisados aos 28 dias (período de cura úmida) e após os processos de envelhecimento, 100 ciclos de imersão-secagem e 28 dias em banho térmico (65°C). Ensaios físicos e mecânicos avaliaram o desempenho, a resistência e a ductilidade dos compósitos. A termogravimetria permitiu observar o consumo da portlandita e a queda da alcalinidade da matriz com 50% de substituição do cimento Portland pela CCA, sem afetar a resistência do material. Os resultados obtidos indicam que a fibra do coco verde tem grande potencial para ser utilizada como reforço de fibrocimentos, desde que seja incorporada a uma matriz de alcalinidade reduzida. / This thesis studies the use of green coconut fiber as a reinforcer in the matrix cement for the production of fibre-cement. Besides being an organic material, the green coconut residues are not easily degradable, but can reduce the landfills lifespan. To evaluate the possibility of use of coconut residue fiber, as reinforcer in composites, physical-chemical treatments were carried out on the fibers, and partially replacing Portland cement with pozzolanic materials for high reactivity (rice husk ash (RHA)) was also added to decrease the alkaline attack matrix on the plant fiber. The experiment was divided into two stages: the first assessed the green coconut fiber with and without treatment and the composites produced with them. The second stage examined the influence reinforcer high reactivity to allow the use of coconut fiber as reinforcement in cementitious matrix. In the preparation of the composites, the technique of dispersing the materials in aqueous solution was used, followed by draining and pressing, as a simplified simulation Hatschek process of industrial manufacture. The composites were analyzed after 28 days and after an aging process, with 100 cycles of immersion-drying or heating in water for 28 days at 65°C). Physical and mechanical tests were used to e valuated the performance, traction resistance and ductility of the composites. A thermogravimetry test allowed the observation of the use of portlandita and the alkalinity reduction of the matrix with the addition of RHA, without affecting the resistance of the material. The results obtained indicate that the green coconut fiber has great potential to be used as a fibre-cement reinforcer, as long it is included in a matrix with reduced alkalinity.
5

[en] PULP REINFORCED CEMENT-BASED COMPOSITES: PHYSICAL, MECHANICAL AND MICROSTRUCTURES CHARACTERIZATION / [pt] COMPÓSITO À BASE DE CIMENTO REFORÇADO COM POLPA DE BAMBU: CARACTERIZAÇÃO FÍSICA, MECÂNICA E MICROESTRUTURAL

MARCOS ALYSSANDRO SOARES DOS ANJOS 11 July 2002 (has links)
[pt] Ainda hoje, no Brasil, o fibrocimento à base de matriz cimentícia reforçados com amianto permanecem como o principal compósito fibroso utilizado em larga escala de produção, apesar da constatação dos seus malefícios, como doenças respiratórias e câncer, causados por esta fibra durante o processo de extração, fabricação e instalação. Nos EUA, União Européia e Canadá a produção de materiais reforçados com amianto foi proibida ou sofreu sérias restrições ao seu uso. No Brasil há uma promessa do governo federal de se iniciar a diminuição da extração do amianto a partir de 2005 até sua completa extinção. Frente a inadequação do uso do amianto para produção de materiais de construção sem riscos à saúde da sociedade, surge a necessidade de se encontrar um substituto com propriedades físicas e mecânicas adequadas que seja ecológico e de custo adequado. Neste trabalho é analisado o uso de polpas celulósicas de bambu, com dois estágios de tratamento diferentes, quais sejam polpas antes do processo de refino e após este processo, para reforço de matrizes cimentícias, utilizando o processo de produção Hatschek em escala laboratorial. As polpas celulósicas foram utilizadas nas porcentagens de 4, 6, 8, 10, 12, 14 e 16% em relação a massa do cimento, sendo utilizada a matriz plena como referência. Foi estudado ainda a substituição parcial do cimento por um resíduo de fábrica de tijolos na proporção de 20, 30 e 40% em relação a massa do cimento e o uso de dois tipos de equipamentos de produção diferentes. O objetivo deste trabalho é determinar a porcentagem ideal de reforço para os dois tipos de polpas utilizadas, discutindo as propriedades físicas, mecânicas e microestruturais de cada um destes compósitos. / [en] Still today, in Brazil, the fibre cement to the base amianthus is the main fibrous composite to the base of main cement with wide production scale, despite verification of its damages, as breathing diseases and cancer, caused by this fiber during the extraction process, production and installation. In the USA, European Union and Canada the production of materials to the base of amianthus are prohibited or they suffered serious restrictions. In Brazil, the federal government wile begin to extinguish the amianthus extraction in 2005 due to the problems used for amianthus writer allow, it is necessary to get a new material with appropriate physical and mechanical properties, that is ecofriendly and of appropriate cost. In this work the use of pulps bamboo cellulose`s is analyzed, with two types of treatment, which are pulps before the process of I refine and after this process, for reinforcement of main cimentícias, using the production process Hatschek in scale laboratories. The pulps cellulose`s was used in the percentages of 4, 6, 8, 10, 12, 14 and 16% in relation to mass of the cement, being used the full head office as reference. In addition, it was substitution of the cement by a residue of the it manufactures of bricks in the proportion of 20, 30 and 40% in relation to mass of the cement and two types of equipment of different production. The aim of this work is to determine the ideal percentage of reinforcement for the two used types of pulps used, discussing the physical properties, mechanics and microstructure of each one of these composites.
6

Stanovení únavových charakteristik betonu s využitím lomově-mechanických parametrů / Determination of Fatigue Characteristics of Concrete Using Fracture-Mechanics Parameteres

Šimonová, Hana January 2013 (has links)
The topic of this PhD. thesis is the issue of determining fatigue characteristics of selected cement-based composites. First, the history of fatigue of metal is mentioned, and some basic notions related to fatigue are clarified. The thesis also summarizes current research in the field of cement-based composites fatigue, and failure mechanisms of plain concrete during static and dynamic tests are described. Furthermore, the thesis deals with the evaluation of static and dynamic experiments’ results with extensive series of C30/37 and C45/55 class concrete specimens. In order to achieve relevant fatigue test evaluation which takes into account the age of the specimens, a new correction procedure of the data measured based on the approximation of the basic fracture-mechanics parameters of tested materials over time was suggested and verified. The annexes of this thesis present complete data obtained during static and dynamic experiments.
7

Lomové testy vybraných těles se speciálním plnivem: experimenty a numerická simulace / Fracture tests of selected specimens with special aggregates: experiments and numerical simulation

Majda, Tomáš January 2019 (has links)
The diploma thesis deals with selected fracture tests and evaluation of fracture parameters of cement-based composite. One part of the thesis deals with cement-based composite with glass spherical aggregate of a single fraction of 2 mm. After production, the beams with dimensions of 20×40×200mm exposed to temperatures in the range from 100 to 1000 °C for one hour. Using the non-destructive ultrasonic pulse method, the degree of damage caused by termal load was determined. Selected specimen with central edge notch were then tested in three-point bending and fragments after these tests were tested in compression. In the second part, attention was paid to the evaluation of fracture tests conducted on specimen from drill-cores taken from selected objects located at the former Transgas Gas Control Center in Prague. The specimen were provided with a chevron notch before being tested in three-point bending. The measured data was modified by the GTDiPS program and in the case of the glass composite the StiCrack program was used to evaluate fracture parameters.
8

Ermüdungsverhalten von hochduktilem Kurzfaserbeton

Junger, Dominik, Mechtcherine, Viktor 09 November 2022 (has links)
Aufgrund seines hervorragenden Verhaltens gegenüber verschiedenen Beanspruchungen ist hochduktiler Beton (engl.: Strain-hardening cement-based composite, SHCC) ein vielversprechender Baustoff für eine Vielzahl an Anwendungen unter statischen, stoßartigen und zyklischen Belastungen. Für einen sicheren Materialeinsatz ist ein tieferes Verständnis des zyklischen Verhaltens erforderlich. Dazu wurden zyklische Belastungsversuche an hochfestem SHCC mit Polyethylen (PE)- Fasern unter Variation des Belastungsregimes durchgeführt. Anhand der Versuche und der morphologischen Analysen konnte gezeigt werden, dass PE-SHCC eine große Sensitivität gegenüber der Variation der mechanischen Einwirkung zeigt.
9

[pt] CARACTERIZAÇÃO DE COMPÓSITOS CIMENTÍCIOS REFORÇADOS COM FIBRAS: APRENDIZAGEM PROFUNDA, MICROTC DE RAIO X INSITU, CORRELAÇÃO DIGITAL DE VOLUME / [en] CHARACTERIZATION OF STRAIN-HARDENING CEMENT-BASED COMPOSITES: DEEP LEARNING, IN-SITU X-RAY MICROCT AND DIGITAL VOLUME CORRELATION

RENATA LORENZONI 29 December 2021 (has links)
[pt] entendimento do macro comportamento dos materiais, este trabalho apresenta soluções inovadoras para a análise de imagens 3D obtidas por microtomografia computadorizada de raios-X (microCT). O material estudado conhecido pelo termo em inglês “strain-hardening cement-based composites” ou pela abreviação SHCC é um compósito cimentício reforçado com fibras que atinge deformações significativas através da formação de múltiplas fissuras, estabelecendo um material cimentício com característica pseudo-dúctil. O primeiro desafio deste trabalho foi reconhecer e quantificar as fases constituintes nas imagens 3D de SHCC obtidas por microCT. Materiais com estruturas complexas podem apresentar imagens em que as fases internas não podem ser distinguidas pela técnica de limiarização clássica, exigindo o uso de outra técnica como a segmentação por Deep Learning (DL). Portanto, este trabalho utilizou DL como solução para esta tarefa. Desta forma, as características de cada fases puderam ser correlacionadas ao comportamento mecânico macro do material em ensaios de microCT in-situ. Outro método moderno de análise de imagens 3D utilizado foi a correlação digital de volume (em inglês, digital volume correlation - DVC). O DVC é uma técnica que estima o campo de deformação sobre todo o volume da amostra, correlacionando as imagens 3D nos estados descarregado e carregado. Assim, as imagens obtidas nos ensaios de tração e compressão in-situ puderam ter seus deslocamentos internos medidos e deformações calculadas. Em síntese, este trabalho trouxe avanços ao campo do processamento digital e análise de imagens 3D, aplicadas a materiais cimentícios, mas que também podem se adaptar à análise de diversos materiais. / [en] Considering the importance of micro and mesoscale analyses to understand the macro behavior of materials, this work brings innovative solutions for analyzing 3D images obtained by X-ray micro-computed tomography (microCT). The studied material was the strain-hardening cement-based composites (SHCC), a fiber reinforced cementitious composite that achieves significant deformations through multiple cracks formation, resulting in a cementitious material with pseudo ductile features. The first challenge of this work was to recognize and quantify the constituent phases in the 3D images of SHCC obtained by microCT. Materials with complex structures may present images in which the internal phases cannot be distinguished by the classical thresholding technique, requiring the use of another technique such as segmentation by Deep Learning (DL). Therefore, this work used DL as a solution for this task. Then, the features of each phase could be correlated to the macro mechanical behavior of the material in in-situ microCT tests. Another modern method for analyzing 3D images used was the digital volume correlation (DVC). DVC is a technique that estimates full-field strain in 3D over the entire volume of the specimen by correlating imaging volumes of the specimen in unloaded and loaded states. Thus, the images obtained from tensile and compression in-situ tests could have their internal displacements measured and strain calculated. In summary, this work brought advances to the 3D image processing and analysis field, applied to cementitious materials, but which could also adapt for the analysis of various materials.

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