Heat flux evaluation in high temperature ring-on-ring contacts

A comprehensive methodology to investigate heat flux in a ring-on-ring tribometer is presented. Thermal fluxes under high contact pressures and temperature differences were evaluated through an experimental campaign and by a numerical procedure of inverse analysis applied to surface temperature measurements. An approximation of a two-dimensional time-dependent analytical solution for the temperature distribution was first developed and subsequently adapted to mimic the specific testing configuration characteristics; the problem was finally simplified to enable further inverse analysis. Experiments were performed using an innovative high temperature ring-on-ring tribometer. The evaluated contact heat transfer rates were reported as a function of normal load and temperature difference between the discs under steady-state conditions; the results reported here show that, in the present test configuration, the temperature difference has stronger influence than the applied load in terms of heat transfer induced by contact

Diferencias en las propiedades reológicas de suspensiones de cal calcítica y dolomítica: influencia de las características de las partículas e implicaciones prácticas en la fabricación de morteros de cal

The study of the rheological properties of lime suspensions is a useful means to evaluate the workability of lime mortars. In this work, we studied the flow behaviour of two industrial hydrated limes, one of calcitic and the other of dolomitic composition, by means of two types of rheometer with different geometry and setup mode. The obtained results were interpreted taking into account the differences in microstructure and surface properties of the suspended particles. Calcitic lime dry particles are formed by angular and polydisperse clusters and, once dispersed in water, they behave like thixotropic materials. On the other hand, the dolomitic lime is formed by nanoparticles and small round cluster and it shows a pronounced plastic behaviour in suspension. This fundamental difference between the two materials explains the traditional preference for dolomitic lime mortars for plastering and rendering applications.El estudio de las propiedades reológicas de suspensiones de cal es una herramienta muy útil para evaluar la trabajabilidad de morteros de cal. En este trabajo se ha estudiado el comportamiento en suspensión de dos cales hidratadas, de composición calcítica y dolomítica, mediante dos tipos de reómetros con geometría y modalidades distintas de medida. Los resultados obtenidos se han interpretado teniendo en cuenta las diferencias en la microestructura y las propiedades de superficie de las partículas en suspensión. Las partículas de cal calcítica están formadas por aglomerados angulares y polidispersos y, una vez dispersadas en agua, presentan un comportamiento tixotrópico. Por su parte, la cal dolomítica está formada por nanopartículas y pequeños agregados redondeados y muestra en suspensión un pronunciado comportamiento plástico. Esta importante diferencia entre las dos cales explica la preferencia tradicional de morteros de cal dolomítica para aplicaciones en revocos

Influence of Surface Finishes and a Calcium Phosphate-Based Consolidant on the Decay of Sedimentary Building Stones Due to Acid Attack

Natural stone has long been used as a building material because of its physical-mechanical resistance and its esthetic appeal. However, over the last century increasing industrial activity has produced more acidic environments, such as polluted urban areas, that can cause serious damage to many buildings and historic monuments, and in particular those made with carbonate rocks, which are most prone to decay. In order to mitigate the physicochemical processes that degrade these buildings, a number of phosphate-based consolidants have been developed, which are highly compatible with the carbonated substrate. Research about the role of the surface and its different possible finishes in the transmission of the agents that damage or protect the stone would therefore be very useful, both when choosing the most suitable stone for new constructions and when restoring historic buildings. The main objective of this research was to determine whether the roughness of three types of surface finish (saw-cut, honed and bush-hammered) influences the durability of four types of natural stone (two calcarenites, one travertine and one sandstone) widely used in Andalusia (Spain). The efficacy of a calcium phosphate-based consolidant as a mitigator of deterioration in polluted urban environments was also studied and to this end the physical properties of untreated and treated samples were measured and compared. The samples were exposed to artificial atmospheres with SO2 pollution in order to assess the damage caused to each surface finish. The results indicate that all the surface finishes were vulnerable to the decay caused by acidic atmospheres, although the saw-cut finish was less affected, perhaps because it did not require additional industrial processing. The mineral composition and texture of the rocks were critical factors in terms of the amount and type of decay they suffered, and the travertine and sandstone were more resistant to deterioration than the calcarenites. Similarly, the pore system of each rock was decisive in the penetration of the consolidant. Application of the consolidant improved the behavior of the treated samples by making them more resistant to acid attack without significantly altering the water vapor permeability, the color or the roughness of the surface

Estudio mineralógico, textural y físico-mecánico de morteros de cal hidráulica curados en distintas condiciones de humedad relativa

This work focuses on the chemical-mineralogical, textural and physical-mechanical properties of hydraulic lime mortars made with siliceous and calcareous aggregate. Mortars were cured at 60% and 90% of relative humidity, so as to assess the variability of mortar petrophysical properties in the hardened state due to the moisture conditions. The final aim was to determine the most adequate moisture conditions to be maintained during application and hardening of hydraulic mortars intended for repair interventions. We found out that using a calcareous aggregate and curing mortar at 90% of relative humidity give place to better textural and mechanical properties. However, these characteristics mostly depend on the maximum size of the aggregate grains, which should be smaller than 6 mm, in order to avoid the occurrence of mechanical discontinuities in the mortar.En este trabajo se han estudiado las propiedades químico-mineralógicas, texturales y físico-mecánicas de morteros de cal hidráulica elaborados con áridos silíceo y calcítico. Estos morteros se han curado al 60% y 90% de humedad relativa, con el fin de evaluar las eventuales diferencias en las propiedades petrofísicas de los morteros una vez endurecidos y así establecer cuál de los dos ambientes es recomendable durante la aplicación y fraguado de morteros de cal hidráulica destinados a obras de restauración. Se ha encontrado que el uso de un árido de composición calcítica y el curado al 90% de humedad relativa dan lugar a morteros hidráulicos con mejores características texturales y propiedades mecánicas. De todas formas, estas características dependen principalmente del tamaño máximo del árido empleado, que debería ser inferior a 6 mm para evitar discontinuidades mecánicas en el mortero

Estudio mineralógico, textural y físico-mecánico de morteros de cal hidráulica curados en distintas condiciones de humedad relativa

This work focuses on the chemical-mineralogical, textural and physical-mechanical properties of hydraulic lime mortars made with siliceous and calcareous aggregate. Mortars were cured at 60% and 90% of relative humidity, so as to assess the variability of mortar petrophysical properties in the hardened state due to the moisture conditions. The final aim was to determine the most adequate moisture conditions to be maintained during application and hardening of hydraulic mortars intended for repair interventions. We found out that using a calcareous aggregate and curing mortar at 90% of relative humidity give place to better textural and mechanical properties. However, these characteristics mostly depend on the maximum size of the aggregate grains, which should be smaller than 6 mm, in order to avoid the occurrence of mechanical discontinuities in the mortar.En este trabajo se han estudiado las propiedades químico-mineralógicas, texturales y físico-mecánicas de morteros de cal hidráulica elaborados con áridos silíceo y calcítico. Estos morteros se han curado al 60% y 90% de humedad relativa, con el fin de evaluar las eventuales diferencias en las propiedades petrofísicas de los morteros una vez endurecidos y así establecer cuál de los dos ambientes es recomendable durante la aplicación y fraguado de morteros de cal hidráulica destinados a obras de restauración. Se ha encontrado que el uso de un árido de composición calcítica y el curado al 90% de humedad relativa dan lugar a morteros hidráulicos con mejores características texturales y propiedades mecánicas. De todas formas, estas características dependen principalmente del tamaño máximo del árido empleado, que debería ser inferior a 6 mm para evitar discontinuidades mecánicas en el mortero.This study was financially supported by the Spanish research group RNM179 of the Junta de Andalucía, by the research project MAT-2012-34473 and by the Institute of Conservation and Restoration of Cultural Heritage of the CICOP foundation (ICON-CICOP)

Spectral spatiality in the acousmatic listening context

Sounds are often experienced as being spatially higher or lower in congruence with their frequency ‘height’ (i.e. pitch register). The term ‘spectral spatiality’ refers to this impression of spatial height and vertical depth as evoked by the perceived occupancy of evolving sound-shapes (spectromorphologies) within the continuum of audible frequencies. Chapters One and Two draw upon a diverse body of literature to explore the cognitive and physiological processes involved in human spatial hearing in general, and spectral spatiality in particular. Thereafter the potential pertinence of a spectral space consciousness in the acousmatic listening experience is highlighted, particularly with regard to more abstract acousmatic contexts where sounds do not directly invoke familiar source identities. Chapters Three and Four further elaborate aspects of spectral space consciousness and propose a terminological framework for discussing musical contexts in terms of their spectral space design. Consequently, it is argued that in acousmatic music, spectral spatiality must be considered as an inseparable aspect of spatiality in general, although its pertinence only becomes directly highlighted in particular musical contexts. The recurring theme in this thesis is that, in acousmatic music, 'space' is not a parameter but a multifaceted quality that is inherent to all sounds. As well as providing an analytical framework for discussing spatiality in acousmatic music, this thesis highlights the compositional potentials offered by spectral spatiality, particularly in relation to the creation of perspectival image in multichannel works. For instance, the possibility of (re)distributing the spectral components of a sound around the listener (circumspectral image) is discussed in context, and a software tool is presented that enables an intuitive and experimental approach to the composition of circumspectral sounds for 6 and 8 channel loudspeaker configurations. This thesis is useful for both composers and analysts interested in aspects of spatiality in acousmatic music. It also offers some insight into spectral space consciousness in non-acousmatic music, and may therefore contribute towards a more general understanding of the nature of our spatial experience in music.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Evaluation of air lime and clayish earth mortars for earthen wall renders

CIAV2013 – International Conference on Vernacular Architecture, 7º ATP, VerSus, 16-20 october 2013An experimental rammed earth wall was traditionally made with local earth and characterized in terms of superficial hardness, compactness, thermal conductivity and water absorption, in exterior environmental conditions. Two mortars were made with an air lime and a mixture of three washed graduated siliceous sands, with volumetric proportions of 1:2 and 1:3 (air lime:sand). A clayish earth was characterized and applied as partial substitutions of air lime on 1:2 mortars and as partial substitutions of the finest sand on 1:3 mortars. Mortars were formulated and characterized in terms of constitution and consistency and samples of mortars applied on ceramic brick were prepared. For each volumetric proportion, mortars without earth and the ones with earth that presented the best workability were applied as renders on panels on the experimental rammed earth wall; also prismatic samples were made. The mortar samples and the renders on the wall were characterized at 90 days of age. This paper presents and discusses some of the results obtained with the characterization of the rammed earth wall, the fresh mortars and its application on the bricks and on the wall. Differences between the mortars are highlighted while their compatibility with traditional rammed earth wall is verified

Modelling the freezing and thawing behaviour of saturated soils

This thesis presents an investigation of the thermo / hydro / mechanical behaviour of saturated soils with cryogenic suction effects. The flow relationships accommodate a number of mechanisms: i) heat transfer by conduction, convection, and latent heat transfer and ii) moisture transfer in the liquid phase due to pressure head, elevation head, and thermal gradients. The mechanical behaviour of the soil is modelled by an elasto-plastic work hardening modified Cam- Clay constitutive model. A numerical solution for the theoretical formulation is presented. Standard finite element methods are used for spatial discretisation and finite difference methods are used for temporal discretisation. Verification of the model is achieved by means of programme of tests to check the following cryogenic components i) coupled thermo-hydraulic response, ii) deformation behaviour of the fully coupled thermo-hydro-mechanical model, iii) transient coupled liquid flow and deformation behaviour, and iv) latent heat of fusion. Validation focused on the impact of the cryogenic related processes included within the proposed theoretical formulation. In particular the development of ice lenses and the movement of moisture under cryogenic suction were investigated. The performance of the proposed model with respect to a number of variables was subsequently explored in order to determine their effect on the magnitude and growth of ice lenses in a freezing soil. The model was then applied to a large scale freezing experiment, namely a fully coupled thermo / hydro / mechanical simulation. The simulated results show a good correlation with the experimental results by predicting the patterns and trends of experimentally observed behaviour and the cryogenic processes that occur during the freezing and thawing of frost susceptible soils. It was therefore concluded that the proposed model is capable of providing a good representation of the fully coupled THM behaviour of saturated soils with cryogenic effects.EThOS - Electronic Theses Online ServiceGBUnited Kingdo