There has been much discussion about the beneficial uses of lamellar graphite iron in piston rings–cylinder liner systems, where a good combinations of both thermal and tribological properties are essential. The excellent tribological performance of lamellar iron under such sliding conditions is principally associated with lubrication behaviour of the graphite particles which are distributed as lamellas throughout the matrix. During sliding, graphite particles are extruded and smeared onto the counterfaces, act as solid lubricating agents and form a thin graphite film between the sliding surfaces. Although this process especially, during the running-in period significantly changes the sliding wear response of the components, the exact mechanism behind of this phenomenon has rarely been discussed in previous studies. It is tribologically beneficial to keep the graphite open, particularly in applications where the scuffing issues do matter. In this thesis, the main causes involved in closing the graphite lamellas are discussed, with a focus on matrix plastic deformation that occurs during sliding. In first step, the relationship between graphite lamellae orientation and plastic deformation was investigated. To do so, two piston rings, belonging to the same two-stroke marine engine operated for different periods of time, were selected and compared to the unworn sample. The worn piston rings displayed a substantial decrease in both frequency and area fraction of the graphite lamellas. Most of the lamellas were closed as a result of plastic deformation of matrix. This happening was caused mainly by the interaction between abrasive particles and metallic matrix. Additionally, it was found that graphite lamellas parallel or near-parallel to the sliding direction exhibited maximum closing tendency under sliding condition. In next step, to have a better understanding of the graphite film formation mechanism and matrix deformation role in closing the graphite lamellas, microindentation and microscratch testing were performed on typical lamellar iron. The qualitative results showed a similar mechanism involving in graphite contribution to lubricate the sliding surfaces. Moreover, microindentations made nearby the graphite lamellas demonstrated that the deformation of the matrix causes the formation of cracks in the centre of the graphite lamellas, compressing and then extruding the graphite from its natural position, irrespective of the lamellas′ size. Furthermore, it was found that subsurface graphite orientation had a large influence on the extrusion behaviour, in that, for graphite lamellas oriented towards the indenter, the effect was observed more pronounced. Furthermore, an improved fully ferritic solution strengthened compacted graphite iron was produced for future wear studies. The effects of different Si levels and section thicknesses on tensile properties and hardness were investigated as well. The influence of Si content and section thickness on mechanical properties was revealed by improving the materials strength and slightly enhancing the hardness through increasing Si content. Besides, Si addition up to 4.5 wt% significantly affected the strength and elongation to failure of cast samples. / Helios / FFI

Cette thèse concerne la caractérisation expérimentale d’un sable limoneux provenant du barrage de Livet – Gavet (38) dans le cadre du projet ANR TerreDurable avec plusieurs objectifs : 1- Caractériser au travers d’essais de laboratoire le comportement hydromécanique d’un sable fin limoneux (sol A1 dans la classification GTR) en fonction de son état de saturation. Lors de cette étude, un accent particulier est porté sur la caractérisation de ce comportement dans le domaine proche de la saturation. 2- Interpréter le comportement hydrique du matériau sur chemin de drainage – imbibition en relation avec l’analyse de sa microstructure. 3- Fournir d’un point de vue général une base de données et d’analyses exhaustive permettant le développement et la calibration de modèles de comportement des sols fins proches de la saturation, en particulier en considérant des chemins de chargement hydromécanique complexes. Pour l’ensemble de cette étude, le matériau est considéré sous deux états : soit à l’état de pâte (matériau normalement consolidé) préparée à une teneur en eau proche de la limite de liquidité, soit sous forme compactée (matériau sur-consolidé) à différentes énergies de compactage et différentes teneurs en eau initiales. / This thesis concerns the experimental characterization of a silty sand from the Livet - Gavet dam (38) as part of the ANR TerreDurable project, for following objectives: 1- Through laboratory tests, characterize the hydro-mechanical behaviour of a fine silty sand (Type A1 in the GTR classification) according to its saturation state. In this study, particular emphasis is placed on the characterization of this behaviour in the near-saturated domain. 2- Interpret the water behaviour of material on the drainage - imbibition cycles, in relation to the analysis of its microstructure. 3- From a general point of view, provide a comprehensive database and analysis allowing the development and calibration of models of near-saturated fine soil's behaviour, in particular, by considering complex hydro-mechanical loading paths. For all tests in this study, the material is considered in two states: either in the state of paste (normally consolidated material) prepared at water content close to the limit of liquidity, or in compacted state (over consolidated material) at different compaction energies and different initial water contents.

Master thesis and building technology solutions transshipment point in Prostejov covers technological studies throughout the construction, distribution structures on buildings, machinery equipment, time and financial plan. Furthermore, the thesis further focuses on one main structures of the whole building, object transshipment point. On this construction project is further developed such documentation and other documents that complement and prescribe requirements for faster, easier, safer, better and more technologically correct implementation of this phase.

Esta Tesis de investigación estudia la propuesta de aplicación de un sistema de mejoramiento de suelos para un proyecto inmobiliario de nueve niveles que se proyecta ejecutar en el distrito de San Juan Bautista, en la región Loreto, la cual colinda con el distrito de Iquitos. Bajo esta premisa, se desarrolla la idea de cómo introducir un sistema de mejoramiento para suelos de baja resistencia, el cual reemplazará el sistema de cimentaciones profundas propuesto inicialmente, en el terreno del proyecto se realizó el estudio de suelos y se concluyó que las capas superficiales son de material orgánico, en la capa intermedia con alta potencia se clasifico a las arenas y finalmente se encontró arcilla dura a una profundidad promedio de 8 a 9 metros. A continuación se procedió a estudiar conceptualmente los diferentes tipos de cimentación profunda y sistemas de reforzamiento de suelos. Finalmente nos centramos en el sistema de Pilas de grava compactada, la cual ya registra eficientes antecedentes en diversos proyectos realizados en la ciudad de Lima, y en el norte del país. Es así, que debido a las características desfavorables de los suelos de la ciudad de San Juan Bautista, se optó a dar inicio con la realización del diseño, luego a la evaluación del proceso constructivo, el análisis de los recursos a emplear; siendo la etapa de exploración de canteras, el proceso más determinante para el inicio de la viabilidad del sistema en términos de diseño, costo y tiempo de ejecución. Finalmente se concluye que el sistema de Pilas de grava compactada tiene la capacidad de incrementar la presión admisible del suelo, y disminuir los costos de construcción de la cimentación. / This Research Thesis studies the proposal for the application of a soil improvement system for a nine-level real estate project that is planned to be executed in the San Juan Bautista district, in the Loreto region, which borders the Iquitos district. Under this premise, the idea of how to introduce an improvement system for highly compressible soils is developed, which will replace the system of deep foundations initially proposed, in the field of the project the soil study was carried out and it was concluded that the surface layers are of organic material, in the intermediate layer with high power the sands were classified and finally hard clay was found at an average depth of 8 to 9 meters. Next, the different types of deep foundations and soil reinforcement systems were conceptually studied. Finally, we focus on the system of Piles of compacted gravel, which already records efficient records in various projects carried out in the city of Lima, and in the north of the country. Thus, due to the unfavorable characteristics of the soils of the city of San Juan Bautista, it was decided to begin with the realization of the design, then to the evaluation of the construction process, the analysis of the resources to be used; being the quarry exploration stage, the most decisive process for the beginning of the viability of the system in terms of design, cost and execution time. Finally, it is concluded that the system of compacted gravel piles has the capacity to increase the admissible pressure of the soil, and decrease the construction costs of the foundation / Tesis