Papers by Keyword: Surface

Abstract: It is known that the surface of a solid body and its volume part are different forms of the same substance. There is a hypothesis about the presence of a transition fractional-dimensional layer, which is the "limiter" of the volume from the surface. It is assumed that this layer is able to store information about changes in the surface and internal structures of the solid. The origin of defects, leading to destruction, in most cases begins in the surface and surface layers of the metal. In this regard, the existence of fractional-dimensional layer as a subsurface structure, which has information about the properties of the whole solid, is of particular importance in the detection of possible critical defects. In order to test this hypothesis, an experiment was conducted based on measuring the magnetic field strength of a steel plate (25x25x2 mm) when its thickness was changed. With the help of sandpaper, one side of the plate was swamped, and the second remained unchanged. The measurements of the magnetic field strength components were carried out on both sides with the plate thickness decreasing by 0.08-0.1 mm from 2.0 to 0.3 mm. Applying a linear approximation to the obtained dependence of the average tangential component of the magnetic field on the plate thickness, it was found that the extrapolated approximation line comes to a point close to zero (0.01 mm). It was assumed that the value 0.01 determines the preliminary value of the fractional-dimensional layer. Such an experiment was carried out for the first time, so the results obtained so far will undoubtedly become the basis for further research in this area.

Abstract: The comparative analysis of quality indicators of asphalt concrete and methods of their control is discussed in the present article. Classifications of modifiers for improving the quality of asphalt concrete are given. Novel nanoscale modifier for the improvement the resistance to climatic influences on asphalt is developed. The nanomodifier is based on sols of iron hydroxide and silicic acid. Nanomodification consists in processing of the mineral component by nanomodifier; such processing leads to the formation of nanoscale layer on the surface of the mineral carrier. As a mineral carrier we propose a highly porous mineral diatomite powder. The influence of the nanomodifier on the weathering resistance of asphalt concrete is investigated. Resistance to climatic influences was estimated by loss of strength after one nominal year of exposure. To simulate environmental impacts, an environmental chamber was used. The specimens were held in conditions that correspond to combination of summer and winter climate. One nominal year of exposure included 10 cycles of variable water saturation-drying at a temperature of 20 °C and 10 cycles of freezing-thawing (freezing was performed at –20 °C, thawing – at 20 °C). Saturation-drying and freezing-thawing duration was four hours. It was shown that by means of nanomodification the weathering resistance can be increased by 36 %.

Abstract: The paper considers the mathematical model of liquid motion in straight-line capillaries. The proposed mathematical model shows the liquid motion in slit-like capillaries, with regard to the density, viscosity and surface tension of liquids, the capillary size, and the angle of capillary inclination to the horizontal. The modeling results are proved by full-scale experiments.

Abstract: Nondestructive penetrant testing is effective, and in some cases, it is the only possible method of accidents prevention at high-risk sites. But in nowadays liquid-filled discontinuity model has not been adequately studied. Hydrodynamics in the open-end capillaries characterize the flow of liquids using the methods of leak detection. To detect surface discontinuities that are capillary, capillary flaw detection methods are used. Until now, the theoretical relation l = l (t) has not been find out. This relation makes it possible to calculate the absorption kinetics in any capillary at all its stages, which would coincide with experimental data with high accuracy. The studies show that the time of filling the capillaries by liquid is usually higher than the theoretically predicted one. Therefore, revealing the regularities of filling capillaries with liquids to the maximum depth and the duration of filling the capillary with liquid by a given depth is an actual task. The authors suggest a model for determining the velocity of fluid in dead-end and open-end and through capillaries, which take into account the fractal topology of the surface.

Abstract: During machining any material, vibrations play a major role in deciding the life of the cutting tool as well as machine tool. The magnitude acceleration of vibrations is directly proportional to the cutting forces. In other words, if we are able to measure the acceleration experienced by the tool during machining, we can get a sense of force. There are many commercially available, pre-calibrated accelerometer sensors available off the shelf. In the current work, an attempt has been made to measure vibrations using ADXL335 accelerometer. This accelerometer is interfaced to computer using Arduino. The measured values are then used to optimize the machining process. Experiments are performed on Brass. During machining, it is better to have lower acceleration values. Thus, the first objective of the work is to minimize the vibrations. Surface roughness is another major factor which criterion “lower is the better” applies. In order to optimize the values, a series of experiments are conducted with three factors, namely, tool type (2 levels), Depth of cut (3 levels) and Feed are considered (3 levels). Mixed level optimization is performed using Taguchi analysis with L18 orthogonal array. Detailed discussion of the parameters shall be given in the article.

Abstract: The possibility of modification of mineral extenders with a specific surface of 350 m²/kg with ultraviolet irradiation is considered. Infrared spectroscopy confirmed that under the influence of ultraviolet irradiation, the bonds of OH-groups with SiO₂ tetrahedra are weakened, that contributes to the formation of extenders of the acid centers of Lewis and Bronsted on the surface. The optimum time of ultraviolet exposure is determined, at which the concentration of active Lewis and Bronsted acid sites on the extenders surface increases by more than 100%. It was found that replacing 10% of cement mass with a modified extenders makes it possible to produce concretes with strength values 20-30% higher than for composites without extenders. Obtaining equal strength concrete is possible with replacing 20% of cement with modified extenders.

Abstract: Recent years have highly been productive in terms of development of both conventional machining technology, but in workpiece surfaces finishing, as well. The overall trend is heading towards increasing accuracy and quality of the manufactured components for machinery and equipment. In a range of finishing abrasive technologies there has been known the introduction of microcrystalline corundum, modification of tools with these abrasive grains, including sintered tools. This development continues and the latest trend is the development of pyramidal grain the Cubitron II. How individual grains behave during operation and how we can use their properties in comparison to classic white corundum still remains complicated matter. The behaviour of selected abrasives has been described in the submitted article.

Abstract: Laser-structured metal surfaces in combination with thermoplastic compression mould processes allow intrinsic hybrid structures with high-strength connections. Suitable process parameters are still to be identified to provide optimised assembly parameters. Therefore, laser structures with different configurations are applied to steel sheets and compressed with textile reinforced thermoplastic composites to manufacture hybrid structures. Laser processing parameters, such as pulse duration or energy as well as laser scanning strategies and therefore structure dimensions are analysed.After manufacturing, specimens are extracted and characterized in single-lap shear tests comparing different configurations to identify boundary conditions for the laser structuring with optimal bonding characteristics.

Abstract: Megaplastic deformation has been realized by sliding friction (or high-pressure torsion) on ion-plasma-nitrided surface of austenitic Fe-Cr-Ni steel. The deformation-induced dissolution of iron and chromium nitrides, the formation of secondary chromium nitride phases and the increase of depth of gradient-composition matrix pseudo-layer have been achieved under friction and subsequent annealing. A quasi-bimetallic foil with the largest dimension of deflection has been produced with the use of friction and subsequent annealing of the nitrided surface.

Abstract: The paper is aimed at the problematics of environmental simulations as one of the efficient methods of behavioural research for exploring the reactions of respondents to certain environmental settings. It explores the contemporary situation of the development of simulation at different levels within the environment, serving as visualizations of designed spaces, for games and simulation /testing of subjective and objective responses to different environmental stimuli. In our long-term research at the BCDlab, we are focused on body conscious design, which means exploring relationships: body/nervous system and the environment with an aim to design human friendly solutions through spatial design. To gain our own experiences with environmental simulations and their impact, in 2015, the Faculty of Architecture BCDlab, developed an interactive application, BCD-APP, which works as a web interface and also in virtual reality. The paper presents the process of setting research methods and results of the first pilot tests of the app as a research tool, with a small controlled group of respondents. They were confronted with pre-selected settings of materials, colours and surface finishing, and with the setting of their own choice, the subjective and objective physiological reactions (brain waves and respiration) were measured by EEG sensors and evaluated in a Labchart environment.