Problem: A lot of attention is given to the safety of the driving and the possibility to register fatigue of the drivers. Driving cars is monotony and static. Vibration loading, which causes changes in the axial system. This causes discomfort and fatigue to drivers after some time of exposure to the loading. Hypothesis: It is possible to prove the changes of mechanical characteristics (indicators) of the axial system using the TVS (transfer vibration through spine) method. By using TVS method before and after different types of loading or before and after relaxation it is possible to detect changes of the viscoelastic properties. This can be done by checking changes in the way of waves transfer through the axial system of the observed participants. Objective: Verify the possibility of use of TVS method to register changes of the viscoelastic characteristics of the axial system. Method: The TVS was chosen as a detection method. The method is based on the use of five-msec semi-bandwidth γ pulse stimuli and consequent application of continuously changing harmonic stimuli which periodically differ between 5Hz and 160Hz to the vertebrae C7 and L5. This wave is carried through the axial system and its acceleration on the spinous processes between C7 and S1 is scanned with the help of accelerometric...

Este trabalho teve como objetivo analisar o comportamento do concreto leve com pérolas de poliestireno expandido (expanded polystyrene – EPS), para posterior utilização em estruturas pré-moldadas constituídas, por exemplo, por painéis de paredes e lajes sujeitas a ações mecânicas. Também foram considerados parâmetros de durabilidade e mecanismos de redução da porosidade. Dentre um universo de solicitações a que as estruturas de concreto leve podem estar submetidas, analisaram-se, para diferentes dosagens: resistência à compressão axial, módulo de elasticidade, absorção de água, resistência à tração na compressão diametral e na flexão. Foram incorporadas pérolas de EPS como componente para proporcionar redução do peso do concreto. Esse concreto leve pode, também, conter sílica ativa para reduzir a porosidade e melhorar a durabilidade das estruturas confeccionadas com esse material. As dosagens de concreto leve com EPS estudadas foram compostas basicamente por: cimento CPV-ARI, agregado miúdo (areia), pérolas de EPS, água e aditivo superplastificante. Ao final da pesquisa, após análise de 45 misturas, observaram-se ganhos de desempenho mecânico com a adição de sílica ativa, adição de fibras de aço, ajuste na granulometria do agregado miúdo e redução do teor de EPS nas misturas, obtendo-se resistência à compressão na ordem de 16 MPa e massa aparente de 1370 kg/m³, com fator de equivalência (FE) correspondente ou superior ao de um concreto convencional de 20 MPa e 2400 kg/m³. Deve-se ressaltar que o emprego de EPS no concreto reduz o peso dos elementos de construção, estruturais ou não, e o consumo de agregados (areia e brita ou seixo), do mesmo modo que o uso de adições minerais reduz o consumo de cimento. / This study aimed to analyse the lightweight concrete behavior with expanded polystyrene beads (EPS beads) for later use in precast structures made of walls panels and slabs, for example, structures under mechanical actions. Durability parameters and mechanisms of porosity reduction were also considered. Among a universe of requests which structures of lightweight concrete can be submitted, were analysed to different mix designs: compressive strength, modulus of elasticity, water absorption, tensile strength in the splitting and in the flexure tests. EPS beads were incorporate as raw material to provide weight reduction to the concrete. This lightweight concrete can also have silica fume to reduce its porosity and to improve durability of structures made with this material. The lightweight concrete mix designs studied were basically composed by: high initial strength cement, small aggregate (sand), EPS beads, water and superplasticizer additive. At the end of the research, after 45 mixtures analysis, mechanical performance gains were observed with the addition of silica fume, addition of steel fibers, adjusting in the fine aggregate\'s particle size and reducing of EPS content in the mixtures, obtaining compressive strength in the order of 16 MPa and apparent mass of 1370 kg/m³, with equivalence factor (EF) corresponding to or higher than that of an ordinary concrete of 20 MPa and 2400 kg/m³. It should be emphasized that the use of EPS in the concrete reduces the weight of the building members, whether structural or not, and the aggregates consumption (sand and gravel or pebble), in the same way as the employment of mineral additions reduces the consumption of cement.

Le réchauffement climatique et le coût élevé des matériaux de construction conventionnels (ciment, chaux, acier) nous obligent à recourir aux matériaux locaux, disponibles et sans effet négatif sur l’atmosphère. Il s’agit de blocs de terre comprimée (BTC) stabilisés par de la gomme arabique et renforcés avec de la paille de riz. L’objectif principal de ce travail est la valorisation des matériaux locaux et écologiques pour la construction des habitations durables. L’étude concerne la caractérisation mécanique, thermique et la durabilité des éprouvettes fabriquées avec de l’argile, du sable, de la gomme arabique, de la paille de riz et de l’eau en des différentes proportions. A cet effet, les pourcentages massiques de gomme arabique sont de 5%, 10% et 15%. Ceux de la paille de riz sont de 0,5%, 1%, 1,5% et 30% de sable sont retenus pour ce travail de recherche. Des briques en BTC de 30 x 15 x 8 cm et des éprouvettes de dimension 4 x 4 x 16 cm sont fabriquées pour réaliser les essais mécaniques. Une méthode « fil chaud » adaptée sur les éprouvettes cylindriques de 16 cm de diamètre sur 32 cm de hauteur est utilisée pour la détermination des conductivités thermiques. L’utilisation de la gomme arabique comme liant dans la construction a donné des résultats satisfaisants. A un taux de 15% de gomme arabique associée à une contrainte de compactage beaucoup plus élevée, nous permettent d’obtenir des BTC ayant une résistance mécanique acceptable ainsi qu'une meilleure résistance à l’eau de pluie. Les résultats mécaniques montrent que la gomme arabique améliore la résistance mécanique de même que la contrainte de compactage. Par contre l’utilisation de paille de riz dans le mélange fait chuter sa résistance mécanique et allège le matériau. Les valeurs de conductivité thermique mesurées, montrent que les différents échantillons ne peuvent pas être considérées comme étant des matériaux isolants. Les éprouvettes exposées aux aléas climatiques (pluie et humidité) pendant un mois montrent que les blocs de terre non stabilisés se sont détériorés sous la pluie. Par contre les éprouvettes stabilisées par la gomme arabique ont conservé leurs bonnes tenues. De même, des éprouvettes stabilisées et non stabilisées sont immergées dans l’eau. A partir de 15 min, toutes les éprouvettes sont détériorées. Les matériaux argileux stabilisés par la gomme arabique ne pourront pas servir en fondation dans la construction. Ce travail de recherche sera complété par des essais de vieillissement du matériau sur des différents échantillons pour sa validation comme nouveau matériau de construction durable / Global warming and the high cost of conventional building materials (cement, lime, steel) force us to use local, available materials with no negative effect on the atmosphere. These are compressed earth blocks (BTC) stabilized with arabic gum and reinforced with rice straw. The main objective of this work is the valorization of local and ecological materials for the construction of sustainable homes. The study concerns the mechanical, thermal and durability characterization of specimens made of clay, sand, arabic gum, rice straw and water in different proportions. For this purpose, the percentages of gum Arabic are 5%, 10% and 15%. Those of rice straw are 0.5%, 1%, 1.5% and 30% of sand are retained for this research work. BTC bricks measuring 30 x 15 x 8 cm and specimens measuring 4 x 4 x 16 cm are manufactured to perform the mechanical tests. A "hot wire" method adapted to cylindrical specimens 16 cm in diameter and 32 cm in height is used for the determination of thermal conductivities. The use of arabic gum as a binder in the construction has given satisfactory results. At a rate of 15% gum Arabic associated with a much higher compressive stress, allow us to obtain BTCs having an acceptable mechanical strength as well as a better resistance to rainwater. Mechanical results show that gum Arabic improves mechanical strength. As is the compaction constraint. By cons the use of rice straw in the mixture reduces its mechanical strength and lightens the material. The measured thermal conductivity values show that the different formulations cannot be considered as insulating materials. The specimens exposed to the climatic hazards (rain and moisture) for a month show that the unstabilized earth blocks have deteriorated in the rain. On the other hand, samples stabilized by gum Arabic have retained their good habits. Similarly, stabilized and unstabilized specimens are immersed in water. From 15 min, all test pieces are deteriorated. The clay materials stabilized by gum Arabic can not be used as a foundation in construction. This research work will be completed by aging tests on the various formulations for validation as a new sustainable building material

Problem: A lot of attention is given to the safety of the driving and the possibility to register fatigue of the drivers. Driving cars is monotony and static. Vibration loading, which causes changes in the axial system. This causes discomfort and fatigue to drivers after some time of exposure to the loading. Hypothesis: It is possible to prove the changes of mechanical characteristics (indicators) of the axial system using the TVS (transfer vibration through spine) method. By using TVS method before and after different types of loading or before and after relaxation it is possible to detect changes of the viscoelastic properties. This can be done by checking changes in the way of waves transfer through the axial system of the observed participants. Objective: Verify the possibility of use of TVS method to register changes of the viscoelastic characteristics of the axial system. Method: The TVS was chosen as a detection method. The method is based on the use of five-msec semi-bandwidth γ pulse stimuli and consequent application of continuously changing harmonic stimuli which periodically differ between 5Hz and 160Hz to the vertebrae C7 and L5. This wave is carried through the axial system and its acceleration on the spinous processes between C7 and S1 is scanned with the help of accelerometric...

Este trabalho teve como objetivo analisar o comportamento do concreto leve com pérolas de poliestireno expandido (expanded polystyrene – EPS), para posterior utilização em estruturas pré-moldadas constituídas, por exemplo, por painéis de paredes e lajes sujeitas a ações mecânicas. Também foram considerados parâmetros de durabilidade e mecanismos de redução da porosidade. Dentre um universo de solicitações a que as estruturas de concreto leve podem estar submetidas, analisaram-se, para diferentes dosagens: resistência à compressão axial, módulo de elasticidade, absorção de água, resistência à tração na compressão diametral e na flexão. Foram incorporadas pérolas de EPS como componente para proporcionar redução do peso do concreto. Esse concreto leve pode, também, conter sílica ativa para reduzir a porosidade e melhorar a durabilidade das estruturas confeccionadas com esse material. As dosagens de concreto leve com EPS estudadas foram compostas basicamente por: cimento CPV-ARI, agregado miúdo (areia), pérolas de EPS, água e aditivo superplastificante. Ao final da pesquisa, após análise de 45 misturas, observaram-se ganhos de desempenho mecânico com a adição de sílica ativa, adição de fibras de aço, ajuste na granulometria do agregado miúdo e redução do teor de EPS nas misturas, obtendo-se resistência à compressão na ordem de 16 MPa e massa aparente de 1370 kg/m³, com fator de equivalência (FE) correspondente ou superior ao de um concreto convencional de 20 MPa e 2400 kg/m³. Deve-se ressaltar que o emprego de EPS no concreto reduz o peso dos elementos de construção, estruturais ou não, e o consumo de agregados (areia e brita ou seixo), do mesmo modo que o uso de adições minerais reduz o consumo de cimento. / This study aimed to analyse the lightweight concrete behavior with expanded polystyrene beads (EPS beads) for later use in precast structures made of walls panels and slabs, for example, structures under mechanical actions. Durability parameters and mechanisms of porosity reduction were also considered. Among a universe of requests which structures of lightweight concrete can be submitted, were analysed to different mix designs: compressive strength, modulus of elasticity, water absorption, tensile strength in the splitting and in the flexure tests. EPS beads were incorporate as raw material to provide weight reduction to the concrete. This lightweight concrete can also have silica fume to reduce its porosity and to improve durability of structures made with this material. The lightweight concrete mix designs studied were basically composed by: high initial strength cement, small aggregate (sand), EPS beads, water and superplasticizer additive. At the end of the research, after 45 mixtures analysis, mechanical performance gains were observed with the addition of silica fume, addition of steel fibers, adjusting in the fine aggregate\'s particle size and reducing of EPS content in the mixtures, obtaining compressive strength in the order of 16 MPa and apparent mass of 1370 kg/m³, with equivalence factor (EF) corresponding to or higher than that of an ordinary concrete of 20 MPa and 2400 kg/m³. It should be emphasized that the use of EPS in the concrete reduces the weight of the building members, whether structural or not, and the aggregates consumption (sand and gravel or pebble), in the same way as the employment of mineral additions reduces the consumption of cement.

Polyurethane and the analogous ‘polyurethane-urea’ are high performance polymeric materials having remarkable properties such as high stiffness, abrasion and tear strengths. In many studies, the low strength rubbers have been blended with various types of polyurethanes for new and improved materials. However, until now, the reported heterogeneous blends offer only a narrow temperature range of application due to the high temperature softening of their polyurethane (-urea) phase. In addition, the conventional solution-or melt-blending methods are time and energy intensive, which tend to forfeit the economical realization of the reported blends. In contrast to earlier studies, a simplified reactive blending process is suggested to synthesize polyurethane-urea via a prepolymer route during blending with rubbers to obtain novel elastomeric materials having extended performance characteristics. The reactive blending process is opted to prepare blends based on nitrile butadiene rubber (NBR) and in-situ synthesized polyurethane-urea (PUU). The blending is carried out in an internal mixer at a preset temperature of 100°C. The critical temperatures of the reactive blending process are determined from the chemo-rheological analysis of a premix, composed of a 4,4′-diphenylmethane diisocyanate (MDI)/polyether (PTMEG) based prepolymer admixed with 1,3-phenylene diamine (mPD). The prepared NBR/PUU blends exhibit highly improved mechanical properties. Contrary to previous reports, the reinforced dynamic-mechanical responses of the novel blends remain stable till very high temperatures (≥180°C). The influence of diamine type on the in-situ synthesized polyurethane-urea and the performance of prepared blends are investigated. Four different diamines, namely 1,3-Phenylene diamine, 1,4-Bis(aminomethyl)benzene, 4,4′-Methylene-bis(2-chloroaniline) and 4,4ʹ-(1,3-Phenylenediisopropylidene)bisaniline, are selected to chain extend the prepolymer to PUU during blending with NBR. The chemical and domain structure of the PUUs are found to greatly influence the reinforced tensile and dynamic-mechanical responses of the NBR/PUU 70/30 blends. The PUU (based on MDI/PTMEG prepolymer and mPD) is blended with polar (CR, XNBR) and nonpolar (NR, EPDM, sSBR) rubbers. PUU compatibilizes with all the rubbers irrespective of their polarity and reinforces their tensile and dynamic-mechanical characteristics. The use of blends in industrial applications, for example, in a truck tire tread compound and as a roller covering material, is examined. In a simplified tire tread formulation, the carbon black for NR-CB composite is partially replaced with an equivalent quantity of PUU for NR/PUU-CB composite of similar hardness. The dynamic mechanical investigations reveal that the energy dissipation and strain dependent softening is high in NR-CB as compared to the NR/PUU-CB composite. In another application, NBR/PUU blend is successfully tested as a rubber roller covering material. The tested blend-covered roller retains its structural integrity and develops less heat build-up as compared to the silica filled NBR-covered roller. This shows a substantial suitability of the blend-covered rollers for film, printing and textile processing machinery. These novel blends are considered to be the promising new materials for many commercial applications including wheels, rubber rollers, belts or pump impellers.

Polyurethane and the analogous ‘polyurethane-urea’ are high performance polymeric materials having remarkable properties such as high stiffness, abrasion and tear strengths. In many studies, the low strength rubbers have been blended with various types of polyurethanes for new and improved materials. However, until now, the reported heterogeneous blends offer only a narrow temperature range of application due to the high temperature softening of their polyurethane (-urea) phase. In addition, the conventional solution-or melt-blending methods are time and energy intensive, which tend to forfeit the economical realization of the reported blends. In contrast to earlier studies, a simplified reactive blending process is suggested to synthesize polyurethane-urea via a prepolymer route during blending with rubbers to obtain novel elastomeric materials having extended performance characteristics. The reactive blending process is opted to prepare blends based on nitrile butadiene rubber (NBR) and in-situ synthesized polyurethane-urea (PUU). The blending is carried out in an internal mixer at a preset temperature of 100°C. The critical temperatures of the reactive blending process are determined from the chemo-rheological analysis of a premix, composed of a 4,4′-diphenylmethane diisocyanate (MDI)/polyether (PTMEG) based prepolymer admixed with 1,3-phenylene diamine (mPD). The prepared NBR/PUU blends exhibit highly improved mechanical properties. Contrary to previous reports, the reinforced dynamic-mechanical responses of the novel blends remain stable till very high temperatures (≥180°C). The influence of diamine type on the in-situ synthesized polyurethane-urea and the performance of prepared blends are investigated. Four different diamines, namely 1,3-Phenylene diamine, 1,4-Bis(aminomethyl)benzene, 4,4′-Methylene-bis(2-chloroaniline) and 4,4ʹ-(1,3-Phenylenediisopropylidene)bisaniline, are selected to chain extend the prepolymer to PUU during blending with NBR. The chemical and domain structure of the PUUs are found to greatly influence the reinforced tensile and dynamic-mechanical responses of the NBR/PUU 70/30 blends. The PUU (based on MDI/PTMEG prepolymer and mPD) is blended with polar (CR, XNBR) and nonpolar (NR, EPDM, sSBR) rubbers. PUU compatibilizes with all the rubbers irrespective of their polarity and reinforces their tensile and dynamic-mechanical characteristics. The use of blends in industrial applications, for example, in a truck tire tread compound and as a roller covering material, is examined. In a simplified tire tread formulation, the carbon black for NR-CB composite is partially replaced with an equivalent quantity of PUU for NR/PUU-CB composite of similar hardness. The dynamic mechanical investigations reveal that the energy dissipation and strain dependent softening is high in NR-CB as compared to the NR/PUU-CB composite. In another application, NBR/PUU blend is successfully tested as a rubber roller covering material. The tested blend-covered roller retains its structural integrity and develops less heat build-up as compared to the silica filled NBR-covered roller. This shows a substantial suitability of the blend-covered rollers for film, printing and textile processing machinery. These novel blends are considered to be the promising new materials for many commercial applications including wheels, rubber rollers, belts or pump impellers.

The diploma thesis is focused on the verification of the parameters of thin lightweight mineral plasters with modified composition. As alternative raw materials are used expanded perlite Vapex, calcined diatomite Celite and powder waste glass of fluorescent lamps. In the theoretical part is summarized knowledge from completed studies dealing with the issue of compensation porous filler component. In the experimental part is tested consistency of fresh mixture, physical-mechanical, sorption and thermal insulating characteristics. It is compared the appearance of the surface and summarized the results of measuring.

The determination of strain properties of masonry in the direction parallel to bed joints is a fundamental pre-requisite for designing structures, where masonry is subjected to horizontal stresses (e. g. strengthening with prestressing). The diploma thesis summarized techniques of determination of masonry modulus of elasticity presented in available literature. The goal is to suggest suitable methodology of determination of masonry modulus in direction parallel to the bed joints. In the practical part of the diploma thesis is that methodology verified by experimental test and results of tests are analyzed and discussed.