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EN
The aim of this article was to perform a practical measurement of the braking properties of a selected Škoda Yeti vehicle on a wet and dry asphalt road and then evaluate and compare the measured data using a decelerograph and a mobile application mSTK. It is a new application for measuring driving dynamics, which was developed for the needs of technical inspection stations in Slovakia. The subject was the intensive braking of a Škoda Yeti passenger car with a fully compressed service brake from different velocities and on different surfaces. A total of 18 measurements were performed, of which 9 on the dry and 9 on the wet surface. This is a new alternative method for recording vehicle driving dynamics. The developed application in conjunction with modern smartphones can thus compete with the current decelographer, both in terms of technical parameters, measurement accuracy (total average deviation 2.11%) and ease of use. The results and data processed in this way are presented in the final part of the paper.
EN
The correct information, including the full braking deceleration of a vehicle, is an essential factor of the road accident process analysis. The aim of the paper was to define and compare the braking properties of the tested Tesla model S electric vehicle by means of the XL MeterTM Pro decelograph and a smartphone as a new alternative method. The measured procedure was the intensive vehicle braking by means of a fully pressed-down operation brake from the different initial velocities. Altogether, 32 measurements were carried out, out of which 16 on the dry surface and 16 on the wet surface. This paper contains the methodology and the results of the performed measurements. The data obtained by an XL Meter TM Pro measuring device were processed by means of the XL Visionä and PC Crash 11.0. software, whereas the data from the smartphone was analysed using the Diagram software. The results and data processed herewith can be useful for the forensic practice.
EN
The objective of this study is to analyse the effect of tool-work interface temperature observed during the turning of AISI 4340 cylindrical steel components in three machining conditions, namely flooded, near-dry and dry conditions with three separate CNMG-PEF 800 diamond finish Titanium Nitride (TiN) coated carbide cutting tool. The machining parameters considered in this study are cutting velocity, feed rate and depth of cut. The experimentswere planned based on full factorial design (33) and executed in an All Geared Conventional Lathe. The toolwork interface temperature was observed using a K-type tool-work thermocouple,while the machining of steel, and subsequently, a mathematical model was developed for the tool-work interface temperature values through regression analysis. The significance of the selected machining parameters and their levels on tool-work interface temperature was found using analysis of variance (ANOVA) and F-test. The results revealed that machining under near-dry condition exhibited lesser temperature at the tool-work interface, which is the sign of producing better quality products in equivalence with the machining under flooded condition.
EN
The cooling and lubricating liquids widely used in metal machining are more and more often considered to be harmful to the natural environment and human health. For economic and ecological reasons the industry and research institutions are searching for methods and measures to limit or eliminate them. This is naturally determined by the conditions that the quality of machined surfaces has to be the same or at least comparable to that obtained with conventional cooling methods. The article presents the results of research into the influence of cooling and lubrication on surface layer physical properties -microhardness and microstructure changes, after turning the C45 and X2CrNiMo 17-12-2 steel dry, with minimal quantity lubrication (MQL) and emulsion in a wide range of cutting parameters. Significant differences in the microhardness parameter HV0,02 and surface layer microstructure depending on the cutting zone cooling and lubrication conditions have been observed. The research has also shown that despite difficulty in turning X2CrNiMo 17-12-2 steel, properly selected cutting parameters help to limit or eliminate fluids used in conventional cooling and lubrication and still obtain comparable or even better surface layer quality.
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