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The laser treatment of surfaces enables the alteration of their morphology and makes them suitable for various applications. This paper discusses the use of a laser beam to develop surface features that enhance pool boiling heat transfer. Two types of structures (in the 'macro' and 'micro' scale) were created on the samples: microfins (grooves) and surface roughness. The impact of the pulse duration and scanning velocity on the height of the microfins and surface roughness at the bottom of the grooves was analyzed with a high precision optical profilometer and microscope. The results indicated that the highest microfins and surface roughness were obtained with a pulse duration of 250 ns and scanning velocity of 200 mm/s. In addition, the influence of the 'macro' and 'micro' scale modifications on the boiling heat transfer of distilled water and ethyl alcohol was studied on horizontal samples heated with an electric heater. The largest enhancement was obtained for the highest microfins and roughest surfaces, especially at small superheats. Heat flux dissipated from the samples containing microfins of 0.4 mm height was, maximally, over three times (for water) and two times (for ethanol) higher than for the samples with smaller microfins (0.2 mm high). Thus, a modification of a selected model of boiling heat transfer was developed so that it would be applicable to laser-processed surfaces. The correlation proved to be quite successful, with almost all experimental data falling within the ±100% agreement bands. [ABSTRACT FROM AUTHOR]

Analysis of the geometrical structure of the surface of materials is an issue already widely recognised and included in international standards. The authors present the possibilities of extending the analysis of the coatings' geometrical structure through X-ray nanotomography imaging, three-dimensional image processing, and stereological methods. Analysis of the state of the art reveals that there are no scientific rapports (indexed by Scopus) on the application X-ray nanotomography for analysis of the geometry of a coating. The presented study shows that this imaging technique can be applied and provide additional information on the quality of the layer. The comparative tests were carried out on samples with a cermet coating before and after laser treatment, including standard tests of the surface geometry and the analysis of three-dimensional images obtained from nanotomography. A set of parameters describing the compactness and thickness distribution of the applied coating is proposed, which facilitates the qualitative assessment of the application process and improvements through the additional processing of technological layers. The obtained results show that although the average thickness values before and after laser treatment did not differ significantly, their distribution on the sample surface was different, as presented in the visualisation. The determined stereological parameter NV (number of objects per unit volume) allowed for the assessment of the layer compactness, and as the analyses showed, this value decreased by more than two times after laser treatment. The analysis of the degree of sample coverage by the cermet layer showed that it increased from 70% to 95% after laser treatment, which confirms the treatment's positive effect on the layer's quality. This research shows that three-dimensional analysis significantly enriches the information about the geometry of the surface layer, providing data which other research techniques are unable to acquire. [ABSTRACT FROM AUTHOR]

This paper deals with importance of executing maintenance activities of rolling stocks by the example of the electric multiple unit EN96 series and with influence of repairing rolling stocks on the transport safety. It also discusses Poland's Supreme Audit Office report for the 2017 year that concerns the condition of safety of the rail transport in Poland. It describes the way in which the maintenance operations are performed with a division of the maintenance levels that depend of time of utilization and distance travelled by a vehicle. [ABSTRACT FROM AUTHOR]

This paper presents results of the experimental research aimed at fire and smoke properties of rolling stock coating system. The overriding research task was to meet current European requirements in the field of fire properties with maintaining the desired performance parameters, such as protective and decorative properties. The research determined parameters such as flame spreading over the surface and heat emission of coating system prepared on steel substrate. Research was carried out to find the optimum thickness of intumescent layer. The tests have shown the effectiveness of use of a protective paint that allows meeting the requirements in the field of fire safety. [ABSTRACT FROM AUTHOR]

This paper experimentally analyses an indoor environment assessment of a large group of respondents regarding their subjective perception of overall comfort, indoor air quality and humidity. The questionnaire survey was applied as a testing method together with measurements of the physical parameters conducted with a microclimate meter. Two types of environment were analysed: educational rooms and the climate chamber. The comparative analysis of the sensations experienced within them indicates that they generate quite similar responses; however, some discrepancies have been identified. The overall comfort of the climate chamber was typically assessed as being higher than that of the educational rooms at the same air temperature. The most favourable air temperature in the climate chamber was ca. 20.7 °C, while in the educational rooms it was ca. 22.3 °C. The most preferable conditions in the climate chamber occurred at a thermal sensation vote of −0.4 ("pleasantly slightly cool"), while in the educational rooms it occurred at +0.2 ("neutral/pleasantly slightly warm"). Quite strong correlations between overall comfort and indoor air quality as well as between humidity assessment and humidity preference votes were observed, which did not seem to depend on the type of environment. These findings are important because results from the simulated conditions are often used in the analyses of actual living/working environments. [ABSTRACT FROM AUTHOR]

People tend to spend considerable amounts of time in buildings; thus the issue of providing proper indoor environmental quality is of significant importance. This paper experimentally analyses the subjective sensations of the occupants of intelligent and traditional buildings with the focus on possible differences between these two types of buildings. The study is based on a large database of 1302 questionnaires collected in 92 rooms where simultaneous measurements of the indoor environment physical parameters (air and globe temperature, relative humidity, carbon dioxide concentration, and illuminance) were carried out. Their impact on the subjective assessment of the indoor environment has been presented and analysed. The results show that the occupants seemed to be more favourable towards the indoor conditions in the intelligent building; however, the differences in comparison to the traditional buildings were not considerable. Similarly, self-reported productivity proved to be higher in the intelligent building, while the optimal range of air temperature, which ensured highest productivity, was 22–25 °C. Moreover, a strong correlation between the occupants' overall comfort and their perception of the air quality has been found. [ABSTRACT FROM AUTHOR]

The paper analyses thermal comfort in intelligent and traditional buildings in Poland. It provides a comprehensive study on the subjective assessment of indoor environment conditions as well as on parameters that influence human thermal sensations and preferences. Direct measurements of physical parameters (e.g., air and globe temperature, relative humidity) as well as simultaneously conducted anonymous questionnaire studies were used to provide the necessary data. The study covered all seasons and a large number of participants representing various age groups and body build types, who completed a total of 1778 questionnaires. The results indicate that typically smart buildings offer higher levels of thermal comfort than the traditional ones and that people tend to prefer warmer environments. Moreover, it has been observed that the BMI index, air movement and the number of people per surface area can have an impact on the perceived thermal sensations. [ABSTRACT FROM AUTHOR]

A characteristic feature of sintered stainless steel (SSS) is its porosity. Porosity results in a lower density of steel, making attractive components for producing lightweight structures and materials used in industry (e.g., the automotive industry or aerospace). Scientists also observe that porosity adversely affects steel's properties, especially its strength properties. One of the proposals for improving the discussed properties is the use of surface treatment of sintered stainless steels, e.g., with the use of concentrated energy sources such as plasma beams or laser beams. However, this proposal is an incidental subject of research, which is not justified from the point of view of the obtained research results presented by a few research groups. In this study, the surface modification (surface treatment) of sintered stainless steel was presented. The authors proposed the use of two surface treatments in order to compare them and obtain the best results. The first treatment was the deposit of Cr3C2–NiCr coatings on SSS surfaces using the atmospheric plasma spraying (APS) method. The second treatment was to create surface layers on SSSs by laser alloying the surface with a CO2 laser. Due to high precision and ease of automation, the most common methods in surface alloying treatment are laser technologies. This research's main aim was to analyze the microstructure and strength properties of the SSS surface layer. The research confirms that applying the Cr3C2–NiCr coating and modifying the surface layer through the laser alloying method improves the mechanical properties of SSSs. [ABSTRACT FROM AUTHOR]

The main objective of the present work is to determine the effects of laser processing on properties of WC-Co electro-spark deposited (ESD) coatings on steel substrates. Tungsten carbide coatings have been applied to steel substrates using a manual electrode feeder, model EIL-8A. The laser beam processing (LBP) of electro-spark coatings was performed using an Nd:YAG fiber laser. The microstructure and properties of laser treated/melted coatings were evaluated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), surface geometric structure (SGS) and roughness measurements and adhesion, microhardness, residual stresses, corrosion resistance and application tests. The obtained experimental data were subjected to statistical analysis and multidimensional numerical and visual exploratory techniques. It has been shown conclusively that the laser-treated ESD WC-Co coatings are characterized by lower microhardness, higher resistance to corrosion, increased roughness and better adhesion to the substrate. LBP homogenizes the chemical composition, refines the microstructure and heals microcracks and pores of ESD coatings. The laser treated ESD WC-Co coatings can be used in frictional sliding nodes (e.g., on the front seal rings used in pumps) and as protective layers. [ABSTRACT FROM AUTHOR]

Many armies around the world showed an increasing interest for the technology of renewable energy sources for military applications. However, to profit fully from solar or wind energy, an energy storage system is needed. In this article, we present an energy storage system based on acid-lead batteries as a component of a modular generation-storage as a model of military "smart camp". We proposed a technical approach to study four different types of batteries: DEEP CYCLE, AGM, WET and VRLA in laboratory and real conditions typical for military equipment. It was observed that the best performance was observed for AGM battery in terms of the highest cold cracking amperage equal to 1205 A combined with the most compact construction and resistance to varying thermal conditions from −25 °C, 25 °C and 50 °C. Additionally, a 12-month long-term testing in real conditions revealed that AGM and VRLA showed decrease in capacity value maintaining only approx. 80% of initial value. [ABSTRACT FROM AUTHOR]

Enhancement of pool boiling heat transfer can be attained with a number of passive and active techniques. The paper experimentally analyses the impact of laser treatment of the copper surfaces on pool boiling heat transfer of distilled water and ethyl alcohol. The samples were modified with a laser beam to produce longitudinal grooves of highly developed microstructures in the laser textured area. Specimens of different groove depths, groove widths and micro-fin widths were produced. The results indicate a significant influence of laser processing on heat flux dissipated from the surfaces and heat transfer enhancement for all the samples tested. The experimental results have been generalized in the form of a heat flux correlation based on a modified model of enhanced pool boiling heat transfer. [ABSTRACT FROM AUTHOR]

Electro-spark deposition (ESD) and laser beam machining (LBM) are the technologies using the concentrated energy flux. This paper deals with the issue of the impact of laser modification on the morphology and mechanical properties of carbide/copper coatings produced by electro-spark treatment. The coatings were applied to C45 carbon steel samples using the EIL-8A device. The following three types of electrodes made using the powder metallurgy (PM) hot pressing technique, from copper and tungsten carbide powders of different percentage compositions, were used for the coatings: 25% WC and 75% Cu; 50% WC and 50% Cu; and 75% WC and 25% Cu. Laser modification of the surface layers was performed with an Nd:YAG laser. The research focused on the analysis of the morphology of coatings applied by electro-spark technology before and after laser processing. The analysis of the morphology of electro-spark coatings revealed that the coatings had microcracks and pores. The laser beam machining of ESD coatings led to the homogenization of chemical composition, fragmentation of the structure, and elimination of microcracks. In addition, measurements of porosity, microhardness, adhesion, and analysis of XRD phase composition of the electro-spark coatings were performed. Laser processing proved to have a positive effect on improving the adhesion of coatings and reducing their porosity. This paper also presents a simulation model of heat transfer processes for the case of laser radiation impact on a WC-Cu coating. The developed numerical model, describing the influence of laser treatment on the distribution of temperature fields in the heated material (at a given depth) is of significant importance in the development of treatment technologies. Laser-modified ESD coatings perform anti-wear and protective functions, which enable their potential application in means of transport such as rolling stock. [ABSTRACT FROM AUTHOR]

This study concentrates on comparing effects of conventional and laser-assisted machining (LAM) of laser-borided Monel 400 alloy. For this purpose, the shaft made from Monel 400 was covered with 200-µm thick boron layer and surface melted using diode laser. For determining the influence of laser beam scanning velocity on final microstructure, microhardness, and depth of melting, four laser beam scanning velocities were set: 5, 6, 8. and 10 m/min. Obtained microstructures are typical for laser-melted metal and are composed of fine crystals. Microhardness increased significantly due to enriching Monel 400 with boron and the level of this increase depends on the laser beam scanning velocity carried out for the process. During both conventional and laser-assisted turning, cutting forces were measured for comparison. Other compared parameters after carrying out these processes were obtained surface roughness and tool life. It was found that it is possible to form laser-borided surface of Monel 400 alloy by machining and using additional laser-assist has a positive impact on the efficiency of the process. Laser-assisted machining allows to lower cutting forces during machining and this leads to extended tool life. On the other hand, this method provides lower values of roughness parameters on the machined surface due to the effect of softening the surface during the process. The paper is the first description of effects obtained by laser-assisted machining of laser-borided surface. [ABSTRACT FROM AUTHOR]

A new method of surface modification based on the method of electrospark alloying (ESA) using carburizer containing nitrogen—carbon components for producing coatings is considered. New processes have been proposed that include the step of applying saturating media in the form of paste-like nitrogenous and nitrogenous-carbon components, respectively, onto the surface without waiting for those media to dry, conducting the ESA process with the use of a steel electrode-tool, as well as with a graphite electrode-tool. Before applying the saturating media, an aluminium layer is applied onto the surface with the use of the ESA method at a discharge energy of Wp = 0.13–6.80 J. A saturating medium in the form of a paste was applied to the surfaces of specimens of steel C22 and steel C40. During nitriding, nitrocarburizing and carburization by ESA (CESA) processes, with an increase in the discharge energy (Wp), the thickness, micro hardness and continuity of the "white layer" coatings, as well as the magnitude of the surface roughness, increase due to saturation of the steel surface with nitrogen and/or carbon, high cooling rates, formation of non-equilibrium structures, formation of special phases, etc. In the course of nitriding, nitrocarburizing and CESA processing of steels C22 and C40, preliminary processing with the use of the ESA method by aluminum increases the thickness, microhardness and continuity of the "white layer", while the roughness changes insignificantly. Analysis of the phase composition indicates that the presence of the aluminum sublayer leads to the formation of the aluminum-containing phases, resulting in a significant increase in the hardness and, in addition, in an increase in the thickness and quality of the surface layers. The proposed methods can be used to strengthen the surface layers of the critical parts and their elements for compressor and pumping equipment. [ABSTRACT FROM AUTHOR]

Influence of laser power on the corrosive resistance of WC–Cu electrospark deposition (ESD) coatings on the C45 carbon steel surface in acidic chloride solution was examined. Potentiodynamic polarization technique was used. Scanning electron microscope (SEM) was employed for the observation the surface of materials. The structure of coatings was dependent on the composition of electrospark electrodes. The WC25–Cu75 coating the largest corrosion resistance was showed. The laser treatment of 70 W laser power caused the homogenization of the structure, and the healing of microcracks and pores of ESD coatings. After laser irradiation a decrease of the microhardness of WC25–Cu75 coating was observed. The corrosion rate of sample for the laser treatment of WC25–Cu75 coating was approximately one-fifth that of coating without laser irradiation. [ABSTRACT FROM AUTHOR]

Abstract: The study analyses the tribological properties of a composite plasma sprayed with Al2O3–3TiO2 mixed in various proportions with CaF2, which is known as a solid lubricant. The coatings were plasma-sprayed in air and were tested using a pin-on-disc tribological set-up. The tests enabled to study their wear resistance and determine the coefficient of friction on the basis of friction force obtained in the course of continuous measurement at a set load. Experiments were optimized by the use of the two-level experiment design aimed at finding the optimal content of CaF2 in the composite. The influence of the spraying parameters on the coefficient of friction, hardness and surface roughness was determined by means of regression analysis. Metallographical studies of the plasma-sprayed composite were conducted with the use of a scanning microscope with an energy dispersion spectrometer (EDS). [Copyright &y& Elsevier]

The paper analyses the indoor environment in two modern intelligent buildings located in Poland. Measurements of air and globe temperatures, relative humidity and carbon dioxide concentration in 117 rooms carried out in the space of 1.5 years were presented. Thermal comfort of the occupants has been investigated using a questionnaire survey. Based on 1369 questionnaires, thermal sensation, acceptability and preference votes were analysed in view of their interdependency as well as their dependency on operative temperature, which proved to be very strong. It has been found that the respondents did not completely rate thermal comfort and indoor environment quality as very high, although the overwhelming sensations were positive. Apart from the operation of heating, ventilation and air conditioning (HVAC) systems, this might have also been the cause of individual human factors, such as body mass index, as tested in the study, or the finding that people were generally in favour of a warmer environment. Moreover, thermal environment proved to be the most important element for ensuring the well-being of the occupants. [ABSTRACT FROM AUTHOR]