Diss. (sammanfattning) Stockholm : Karolinska institutet, 2006. / Härtill 5 uppsatser.

Os parâmetros obtidos nos resultados de ensaios triaxiais de módulo de resiliência em solos têm sido cada vez mais utilizados no dimensionamento de pavimentos. Estes parâmetros são fundamentais em análises estruturais e mecanísticas de pavimentos. Pelas normas atuais o ensaio pode ser realizado em diversos tamanhos de corpo-de-prova contanto que respeite a relação entre diâmetro por altura 1:2 e a relação tamanho máximo de partícula por diâmetro do corpo-de-prova 1:5. O objetivo deste trabalho é compreender como variam os resultados de módulo de resiliência quando os ensaios são realizados em diferentes tamanhos de corpode- prova. Para realizar esta pesquisa foram utilizados quatro solos distintos ensaiados em corpos-de-prova de 7,5 x 15 cm, 10 x 20 cm e 15 x 30 cm. Os solos escolhidos foram uma areia, um solo arenoso fino laterítico, um solo argiloso e um solo residual de granito (saibro). Todos os quatro solos são utilizados como materiais para pavimentação e são provenientes do estado do Rio Grande do Sul. Os materiais foram caracterizados por ensaios de granulometria, peso específico real dos grãos e limites de liquidez e plasticidade. Foram realizados ensaios de compactação nas energias normal e intermediária obtendo-se assim os parâmetros de compactação para os ensaios triaxiais. Em dois dos quatro solos da pesquisa ainda se realizou ensaios de classificação MCT. Os ensaios triaxiais foram realizados com os quatro solos, em três tamanhos e com duas energias de compactação, totalizando 24 ensaios. Após revisão bibliográfica sobre modelos matemáticos de regressão, decidiu-se interpretar os resultados pelos modelos Tensão Confinante, Tensão Desvio, Modelo Teta e Modelo Composto. Dentre os quatro modelos utilizados, o Modelo Composto obteve os melhores resultados de ajuste. Realizaram-se análises dos parâmetros obtidos nos modelos pela variação do tamanho de corpo-de-prova, onde se observou um pequeno aumento dos valores de MR quando ensaiados em corpos-de-prova maiores. Realizou-se ainda uma comparação estatística entre os resultados dos ensaios triaxiais em que a principal conclusão foi de que a areia, dentre os quatro solos estudados, é considerada o único material que não varia seus módulos conforme o ensaio é realizado em diferentes tamanhos de corpo-de-prova. / The results of resilient modulus test of soils have been increasingly used in pavement design, once they are fundamental in structural and mechanistic analysis of pavements. By the current standards/protocols, the test may be performed in various sizes of test specimens as long as it respects the relationship between diameter and height ratio 1:2 and the relationship between maximum particle size and diameter of the test specimen 1:5. The aim of this study is to understand how the results of resilient modulus vary when the tests are conducted in different sizes of test specimen. In order to conduct this research, four different types of soil were used and tested in specimens of 7.5 x 15 cm, 10 x 20 cm and 15 x 30 cm. The soils chosen were sand, fine sandy lateritic soil, clayey soil and residual soil of granite (gravel). All the four soils are used for pavement materials and are original from the state of Rio Grande do Sul, Brazil. The tests carried out for characterization of the materials include: grain size distribution, physical characterization and Atterberg limits. Proctor compaction test were performed in two different energies, thus obtaining the compression parameters for the compaction of the specimen. Additionally, in two of the four soils of the research, experiments of MCT classification were carried out. The resilient modulus tests were performed with the four soils in three sizes and in two compaction energies, totalizing 24 experiments. After reviewing the literature on regression mathematical models, it was decided to interpret the results from models of Confining Pressure, Deviation Stress, Teta Model and Composted Model. Among the four models used, the Composted Model showed the best fitting results. Analysis were performed considering coefficients obtained in the models versus the size of the specimen. A small increase in resilient modulus values was noticed for experiments performed with larger samples. A statistical comparison between the results of the resilient modulus tests was performed, and the main conclusion was that the sand is considered the only material among the four soils that do not vary its modules as the test is performed on different sizes of specimen.

Os parâmetros obtidos nos resultados de ensaios triaxiais de módulo de resiliência em solos têm sido cada vez mais utilizados no dimensionamento de pavimentos. Estes parâmetros são fundamentais em análises estruturais e mecanísticas de pavimentos. Pelas normas atuais o ensaio pode ser realizado em diversos tamanhos de corpo-de-prova contanto que respeite a relação entre diâmetro por altura 1:2 e a relação tamanho máximo de partícula por diâmetro do corpo-de-prova 1:5. O objetivo deste trabalho é compreender como variam os resultados de módulo de resiliência quando os ensaios são realizados em diferentes tamanhos de corpode- prova. Para realizar esta pesquisa foram utilizados quatro solos distintos ensaiados em corpos-de-prova de 7,5 x 15 cm, 10 x 20 cm e 15 x 30 cm. Os solos escolhidos foram uma areia, um solo arenoso fino laterítico, um solo argiloso e um solo residual de granito (saibro). Todos os quatro solos são utilizados como materiais para pavimentação e são provenientes do estado do Rio Grande do Sul. Os materiais foram caracterizados por ensaios de granulometria, peso específico real dos grãos e limites de liquidez e plasticidade. Foram realizados ensaios de compactação nas energias normal e intermediária obtendo-se assim os parâmetros de compactação para os ensaios triaxiais. Em dois dos quatro solos da pesquisa ainda se realizou ensaios de classificação MCT. Os ensaios triaxiais foram realizados com os quatro solos, em três tamanhos e com duas energias de compactação, totalizando 24 ensaios. Após revisão bibliográfica sobre modelos matemáticos de regressão, decidiu-se interpretar os resultados pelos modelos Tensão Confinante, Tensão Desvio, Modelo Teta e Modelo Composto. Dentre os quatro modelos utilizados, o Modelo Composto obteve os melhores resultados de ajuste. Realizaram-se análises dos parâmetros obtidos nos modelos pela variação do tamanho de corpo-de-prova, onde se observou um pequeno aumento dos valores de MR quando ensaiados em corpos-de-prova maiores. Realizou-se ainda uma comparação estatística entre os resultados dos ensaios triaxiais em que a principal conclusão foi de que a areia, dentre os quatro solos estudados, é considerada o único material que não varia seus módulos conforme o ensaio é realizado em diferentes tamanhos de corpo-de-prova. / The results of resilient modulus test of soils have been increasingly used in pavement design, once they are fundamental in structural and mechanistic analysis of pavements. By the current standards/protocols, the test may be performed in various sizes of test specimens as long as it respects the relationship between diameter and height ratio 1:2 and the relationship between maximum particle size and diameter of the test specimen 1:5. The aim of this study is to understand how the results of resilient modulus vary when the tests are conducted in different sizes of test specimen. In order to conduct this research, four different types of soil were used and tested in specimens of 7.5 x 15 cm, 10 x 20 cm and 15 x 30 cm. The soils chosen were sand, fine sandy lateritic soil, clayey soil and residual soil of granite (gravel). All the four soils are used for pavement materials and are original from the state of Rio Grande do Sul, Brazil. The tests carried out for characterization of the materials include: grain size distribution, physical characterization and Atterberg limits. Proctor compaction test were performed in two different energies, thus obtaining the compression parameters for the compaction of the specimen. Additionally, in two of the four soils of the research, experiments of MCT classification were carried out. The resilient modulus tests were performed with the four soils in three sizes and in two compaction energies, totalizing 24 experiments. After reviewing the literature on regression mathematical models, it was decided to interpret the results from models of Confining Pressure, Deviation Stress, Teta Model and Composted Model. Among the four models used, the Composted Model showed the best fitting results. Analysis were performed considering coefficients obtained in the models versus the size of the specimen. A small increase in resilient modulus values was noticed for experiments performed with larger samples. A statistical comparison between the results of the resilient modulus tests was performed, and the main conclusion was that the sand is considered the only material among the four soils that do not vary its modules as the test is performed on different sizes of specimen.

Métodos acurados de avaliação de tenacidade à fratura, incluindo curvas de resistência ao rasgamento dúctil de juntas soldadas de dutos e risers rígidos, tornam-se essenciais em procedimentos de avaliação de defeitos em regiões de soldas e zonas termicamente afetadas, nas quais defeitos não detectados podem se propagar devido às grandes tensões e deformações envolvidas na instalação e/ou operação dessa classe de estruturas. Este trabalho apresenta uma investigação experimental da tenacidade à fratura de uma junta soldada de um duto rígido de aço API 5L X80 (curvas J-Ãa). A motivação para este trabalho decorre da demanda crescente na aplicação de dutos de alta resistência na indústria de óleo e gás, em particular dutos submarinos e risers rígidos em catenária. Para tal, foram empregados corpos de prova de tração SE(T) fixados por garras, e flexão três pontos SE(B) contendo entalhe no centro da solda, para determinação das curvas J-R pelo método do corpo de prova único utilizando a técnica da flexibilidade no descarregamento, além das funções de flexibilidade e fatores n referentes aos corpos de prova SE(T) e SE(B) em função do nível de dissimilaridades mecânicas, o que permite obter valores mais assertivos das propriedades de tenacidade à fratura de juntas soldadas. / Accurate measurements of fracture resistance properties, including crack growth resistance curves for pipeline girth welds, become essential in defect assessment procedures of the weldment region and the heat affected zone, where undetected crack-like defects (such as lack of penetration, deep undercuts, root cracks, etc.) may exhibit further crack extension due to high tensile stresses and strains during installation and in-service operation. This work presents an investigation of the ductile tearing properties for a girth weld made of an API 5L X80 pipeline steel using experimentally measured crack growth resistance curves (J-Ãa curves). Use of these materials is motivated by the increasing demand in the number of applications for manufacturing high strength pipes for the oil and gas industry including marine applications and steel catenary risers. Testing of the pipeline girth welds utilized sidegrooved, clamped SE(T) specimens and 3P bend SE(B) specimens with a weld centerline notch to determine the crack growth resistance curves based upon the unloading compliance (UC) method using a single specimen technique. Recently developed compliance functions and n-factors applicable for SE(T) and SE(B) fracture specimens with homogeneous material and overmatch welds are introduced to determine crack growth resistance data from laboratory measurements of load-displacement records. This experimental characterization provides additional toughness data which serve to evaluate crack growth resistance properties of pipeline girth welds using SE(T) and SE(B) specimens with weld centerline cracks.

Os parâmetros obtidos nos resultados de ensaios triaxiais de módulo de resiliência em solos têm sido cada vez mais utilizados no dimensionamento de pavimentos. Estes parâmetros são fundamentais em análises estruturais e mecanísticas de pavimentos. Pelas normas atuais o ensaio pode ser realizado em diversos tamanhos de corpo-de-prova contanto que respeite a relação entre diâmetro por altura 1:2 e a relação tamanho máximo de partícula por diâmetro do corpo-de-prova 1:5. O objetivo deste trabalho é compreender como variam os resultados de módulo de resiliência quando os ensaios são realizados em diferentes tamanhos de corpode- prova. Para realizar esta pesquisa foram utilizados quatro solos distintos ensaiados em corpos-de-prova de 7,5 x 15 cm, 10 x 20 cm e 15 x 30 cm. Os solos escolhidos foram uma areia, um solo arenoso fino laterítico, um solo argiloso e um solo residual de granito (saibro). Todos os quatro solos são utilizados como materiais para pavimentação e são provenientes do estado do Rio Grande do Sul. Os materiais foram caracterizados por ensaios de granulometria, peso específico real dos grãos e limites de liquidez e plasticidade. Foram realizados ensaios de compactação nas energias normal e intermediária obtendo-se assim os parâmetros de compactação para os ensaios triaxiais. Em dois dos quatro solos da pesquisa ainda se realizou ensaios de classificação MCT. Os ensaios triaxiais foram realizados com os quatro solos, em três tamanhos e com duas energias de compactação, totalizando 24 ensaios. Após revisão bibliográfica sobre modelos matemáticos de regressão, decidiu-se interpretar os resultados pelos modelos Tensão Confinante, Tensão Desvio, Modelo Teta e Modelo Composto. Dentre os quatro modelos utilizados, o Modelo Composto obteve os melhores resultados de ajuste. Realizaram-se análises dos parâmetros obtidos nos modelos pela variação do tamanho de corpo-de-prova, onde se observou um pequeno aumento dos valores de MR quando ensaiados em corpos-de-prova maiores. Realizou-se ainda uma comparação estatística entre os resultados dos ensaios triaxiais em que a principal conclusão foi de que a areia, dentre os quatro solos estudados, é considerada o único material que não varia seus módulos conforme o ensaio é realizado em diferentes tamanhos de corpo-de-prova. / The results of resilient modulus test of soils have been increasingly used in pavement design, once they are fundamental in structural and mechanistic analysis of pavements. By the current standards/protocols, the test may be performed in various sizes of test specimens as long as it respects the relationship between diameter and height ratio 1:2 and the relationship between maximum particle size and diameter of the test specimen 1:5. The aim of this study is to understand how the results of resilient modulus vary when the tests are conducted in different sizes of test specimen. In order to conduct this research, four different types of soil were used and tested in specimens of 7.5 x 15 cm, 10 x 20 cm and 15 x 30 cm. The soils chosen were sand, fine sandy lateritic soil, clayey soil and residual soil of granite (gravel). All the four soils are used for pavement materials and are original from the state of Rio Grande do Sul, Brazil. The tests carried out for characterization of the materials include: grain size distribution, physical characterization and Atterberg limits. Proctor compaction test were performed in two different energies, thus obtaining the compression parameters for the compaction of the specimen. Additionally, in two of the four soils of the research, experiments of MCT classification were carried out. The resilient modulus tests were performed with the four soils in three sizes and in two compaction energies, totalizing 24 experiments. After reviewing the literature on regression mathematical models, it was decided to interpret the results from models of Confining Pressure, Deviation Stress, Teta Model and Composted Model. Among the four models used, the Composted Model showed the best fitting results. Analysis were performed considering coefficients obtained in the models versus the size of the specimen. A small increase in resilient modulus values was noticed for experiments performed with larger samples. A statistical comparison between the results of the resilient modulus tests was performed, and the main conclusion was that the sand is considered the only material among the four soils that do not vary its modules as the test is performed on different sizes of specimen.

A large-area electronics (LAE) strain sensor, termed soft elastomeric capacitor (SEC), has shown great promise in fatigue crack monitoring. The SEC is capable to monitor strain changes over a large structural surface and undergo large deformations under cracking. Previous tests verified that the SEC can detect and localize fatigue cracks under low-cycle fatigue loading. In this paper, we further investigate the SEC's capability for monitoring high-cycle fatigue cracks, which are commonly seen in steel bridges. The peak-to-peak amplitude (pk-pk amplitude) of the SEC measurement is proposed as an indicator of crack growth. This technique is is robust and insensitive to long-term capacitance drift. To overcome the difficulty of identifying the pk-pk amplitude in time series due to high signal-to-noise ratio, a signal processing method is established. This method converts the measured SEC capacitance and applied load to power spectral densities (PSD) in the frequency domain, such that the pk-pk amplitudes of the measurements can be accurately extracted. Finally, the performance of this method is validated using a fatigue test of a compact steel specimen equipped with a SEC. Results show that the crack growth under high-cycle fatigue loading can be successfully monitored using the proposed signal processing method.

The first part of the diploma thesis with name „Evaluation of dynamic damage of composite structure“ focuses on designing device for impact experiments and suitable laminate samples made from prepregs. The conditions and problems of impact tests are also demonstrated here. The second part of the thesis deals with non-destructive control of damaged specimens based on thermography. This is mainly the extent of defects in the impaired area and the evaluation of results using the pulse infrared thermography method. Finally, the relative deviation in the crack size comparison between the visual method and thermographic are compared. Consequently, the residual strength of the damaged samples against undamaged specimens are compared using bending tests.

The problems with the crack length determination by the unloading compliance method are well known for Charpy size specimens. The final crack lengths calculated for bent specimens do not fulfil ASTM 1820 accuracy requirements. Therefore some investigations have been performed to resolve this problem. In those studies it was considered that measured compliance should be corrected for various factors, but satisfying results were not attained. In the presented work the problem was attacked from the other side, the measured specimen compliance was taken as a correct value and what had to be adjusted was the calculation procedure. On the basis of experimentally obtained compliances of bent specimens and optically measured crack lengths the investigation was carried out. Finally, a calculation procedure enabling accurate crack length calculation up to 5mm of plastic deflection was developed. Applying the new procedure, out of investigated 238 measured crack lengths, more than 80% of the values fulfilled the ASTM 1820 accuracy requirements, while presently used procedure provided only about 30% of valid results. The newly proposed procedure can be also prospectively used in modified form for the specimens of different than Charpy size.

The embrittlement of reactor pressure vessel (RPV) steels due to neutron irradiation restricts the operating lifetime of nuclear reactors. The reference temperature 𝑇0, obtained from fracture mechanics testing using the Master Curve concept, is a good indicator of the irradiation resistance of a material. The measurement of the shift in 𝑇0 after neutron irradiation, which accompanies the embrittlement of the material, using the Master Curve concept, enables the assessment of the reactor materials. In the context of worldwide life time extensions of nuclear power plants, the limited availability of neutron irradiated materials (surveillance materials) is a challenge. Testing of miniaturized 0.16T C(T) specimens manufactured from already tested standard Charpy-sized specimens helps to solve the material shortage problem. In this work, four different reactor pressure vessel steels with different compositions were investigated in the unirradiated and in the neutron-irradiated condition. A total number of 189 mini-C(T) samples were fabricated and tested. An important component of this study is the transferability of fracture mechanics data from mini-C(T) to standard Charpy-sized specimen. Our results demonstrate good agreement of the reference temperatures from the mini-C(T) specimens with those from standard Charpy-sized specimens. RPV steels containing higher Cu and P contents exhibit a higher increase in 𝑇0 after irradiation. The fracture surfaces were investigated using SEM in order to record the location of the fracture initiators. The fracture modes were also determined. A large number of test results formed the basis for a censoring probability function, which was used to optimally select the testing temperature in Master Curve testing. The effect of the slow stable crack growth censoring criteria from ASTM E1921 on the determination of 𝑇0 was analysed and found to have a minor effect. Our results demonstrate the validity of mini-C(T) specimen testing and confirm the role of the impurity elements Cu and P in neutron embrittlement. We anticipate further research linking microstructure to the fracture properties of materials before and after neutron irradiation and the optimization of Master Curve testing using the results from our statistical analysis.

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