IDENTIFICATION OF MECHANICAL PROPERTIES OF STRUCTURES WOUND FLEXIBLE COUPLINGS

Tato bakalářská práce se zabývá především sestavením návrhových výpočtů pro inovativní model pružné spojky. Získané vztahy mohou posloužit k předběžnému dimenzování částí spojky, umožní odhad budoucího chování spojky v závislosti na jejích parametrech a srovnání s již dostupnými typy pružných spojek.This bachelor thesis deals primarily with definition of calculation formulas to be used for an innovational type of flexible coupling. Acquired formulas can be used for preliminary dimensioning of coupling parts, might help to estimate behavior of the coupling depending on its parameters and will allow comparison with already existing types of couplings

FEM simulation of the deformation behavior of foam and honeycomb sandwich cores

Práce je zaměřena na problematiku tvorby numerických modelů jader sendvičů. Je popsána stavba sendvičových struktur, mechanické charakteristiky materiálů tvořících voštinová a pěnová jádra a jsou poskytnuty analytické vztahy pro výpočty. Dále je pro dvojici vybraných vzorků materiálů, voštiny a pěny, zpracován metodický postup MKP simulace při snaze nalézt efektivní způsob tvorby a kalibrace numerických modelů. Jsou popsány teoretické úvahy a je vedena diskuze nad výsledky.The thesis is focused on issues regarding creation of numerical models of sandwich cores. A composition of a sandwich is described as well as mechanical properties of the cores materials. Analytical solutions of sandwich stuctures are provided. A procedure of a finite element analysis of selected honeycomb and foam specimens is described, being focused on finding an efficient way of creating and calibrating numerical models. Theoretical assumptions and results are discussed

EFFECT OF SANDSTONE ANISOTROPY ON ITS HEAT AND MOISTURE TRANSPORT PROPERTIES

Each type of natural stone has its own geological history, formation conditions, different chemical and mineralogical composition, which influence its possible anisotropy. Knowledge in the natural stones anisotropy represents crucial information for the process of stone quarrying, its correct usage and arrangement in building applications. Because of anisotropy, many natural stones exhibit different heat and moisture transport properties in various directions. The main goal of this study is to analyse several anisotropy indices and their effect on heat transport and capillary absorption. For the experimental determination of the anisotropy effect, five types of sandstone coming from different operating quarries in the Czech Republic are chosen. These materials are often used for restoration of culture heritage monuments as well as for other building applications where they are used as facing slabs, facade panels, decoration stones, paving, etc. For basic characterization of studied materials, determination of their bulk density, matrix density and total open porosity is done. Chemical composition of particular sandstones is analysed by X-Ray Fluorescence. Anisotropy is examined by the non-destructive measurement of velocity of ultrasonic wave propagation. On the basis of ultrasound testing data, the relative anisotropy, total anisotropy and anisotropy coefficient are calculated. Then, the measurement of thermal conductivity and thermal diffusivity in various directions of samples orientation is carried out. The obtained results reveal significant differences between the parameters characterizing the heat transport in various directions, whereas these values are in accordance with the indices of anisotropy. Capillary water transport is described by water absorption coefficient measured using a sorption experiment, which is performed for distilled water and 1M NaCl water solution.  The measured data confirm the effect of anisotropy which is qualitatively the same as for the heat transport parameters. Summarizing the obtained results, it can be concluded that the anisotropy of sandstone should always be considered in planning the restoration works on the architectural heritage, in order to ensure compatibility between the original and replacement material.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7202</p

EVALUATION OF THE APPLICATION OF A THERMAL INSULATION SYSTEM: INSITU COMPARISSON OF SEASONAL AND DAILY CLIMATIC FLUCTUATIONS

The current outdated state of many institutional and administrative buildings in the EU region poses a significant burden from the energy sustainability point of view. According to the contemporary EU requirements on the energy efficiency of buildings maintenance, an evaluation of performed improvements is essential for the assessment of expended investments. This paper describes the effect of building envelope reconstruction works consisting in the installation of a thermal insulation system. Here, a long-term continuous monitoring is used for the extensive assessment of the seasonal and daily temperature and relative humidity fluctuations. The obtained results include temperature and relative humidity profiles in the wall cross-section as a response to the changing exterior climatic conditions. The analysis of measured data reveals substantial improvements in thermal stability of the analyzed wall during temperature peaks. While the indoor temperatures exceeding 28 °C are recorded during summer before application of the thermal insulation layer, the thermal stability of the indoor environment is distinctly upgraded after performed improvements. Based on the complex long-term monitoring, a relevant experience is gained for the future work on energy sustainability and fulfilment of the EU directives

Thermal tuning of spectral emission from optically trapped liquid-crystal droplet resonators

Surfactant-stabilized emulsion droplets of liquid crystals (LCs) suspended in water and labeled with a fluorescent dye form active, anisotropic optofluidic microresonators. These microresonators can host whispering gallery modes (WGMs), high-quality morphology-dependent optical resonances that are supported due to the contrast of refractive index between the LC droplets and the surrounding aqueous medium. In addition, owing to the refractive index contrast, such LC emulsion droplets can be stably trapped in three dimensions using optical tweezers, enabling long-term investigation of their spectral characteristics. We explore various combinations of fluorescently dyed LC droplets and host liquid-surfactant systems and show that the WGM emission spectra of optical resonators based on optically trapped LC emulsion droplets can be largely and (almost) reversibly tuned by controlled changes of the ambient temperature. Depending on the actual range of temperature modulation and LC phase of the studied droplet, thermally induced effects can either lead to phase transitions in the LC droplets or cause modifications of their refractive index profile without changing their LC phase. Our results indicate feasibility of this approach for creating miniature thermally tunable sources of coherent light that can be manipulated and stabilized by optical forces

Service Life Assessment of Historical Building Envelopes Constructed Using Different Types of Sandstone: A Computational Analysis Based on Experimental Input Data

Service life assessment of three historical building envelopes constructed using different types of sandstone is presented. At first, experimental measurements of material parameters of sandstones are performed to provide the necessary input data for a subsequent computational analysis. In the second step, the moisture and temperature fields across the studied envelopes are calculated for a representative period of time. The computations are performed using dynamic climatic data as the boundary conditions on the exterior side of building envelope. The climatic data for three characteristic localities are experimentally determined by the Czech Hydrometeorological Institute and contain hourly values of temperature, relative humidity, rainfalls, wind velocity and direction, and sun radiation. Using the measured durability properties of the analyzed sandstones and the calculated numbers of freeze/thaw cycles under different climatic conditions, the service life of the investigated building envelopes is assessed. The obtained results show that the climatic conditions can play a very significant role in the service life assessment of historical buildings, even in the conditions of such a small country as the Czech Republic. In addition, the investigations reveal the importance of the material characteristics of sandstones, in particular the hygric properties, on their service life in a structure

Preparation and Characterization of Novel Plaster with Improved Thermal Energy Storage Performance

Thermal energy storage systems based on latent heat utilization represent a promising way to achieve building sustainability and energy efficiency. The application of phase change materials (PCMs) can substantially improve the thermal performance of building envelopes, decrease the energy consumption, and support the thermal comfort maintenance, especially during peak periods. On this account, the newly formed form-stable PCM (FSPCM) based on diatomite impregnated by dodecanol is used as an admixture for design of interior plasters with enhanced thermal storage capability. In this study, the effect of FSPCM admixture on functional properties of plasters enriched by 8, 16 and 24 wt.% is determined. On this account, the assessment of physical, thermal, hygric, and mechanical properties is done in order to correlate obtained results with applied FSPCM dosages. Achieved results reveal only a minor influence of applied FSPCM admixture on material properties when compared to negative impacts of commercially produced PCMs. The differential scanning calorimetry discloses variations of the phase change temperature, which ranging from 20.75 &deg;C to 21.68 &deg;C and the effective heat capacity increased up to 15.38 J/g accordingly to the applied FSPCM dosages