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    Exquisite Energy Savings at Cold Metal Forming of Threads through the Application of Polymers
    (MDPI, 2022-03-08) Píška, Miroslav; Sliwková, Petra; Vnuková, Zuzana; Petrenec, Martin; Sedláková, Eva
    One of the global problems today is energy—its production and distribution. As the human population grows, the consumption of energy rises simultaneously. However, the natural sources are limited, and so the focus on power savings becomes more and more important. One of the ways to reduce consumption is the use of effective lubricants and tribological fluids in industry, especially in processes with high demands on energy but high quality of products as well. Forming is a typical example of such technology, and the application of polymers seems to be a very important challenge, because the application of straight oils or lubricant with extreme pressure additives seems to be prevailing in that field. Nevertheless, the polymer lubricant should fulfill all European standards as well as the environmental and ecological limitations with respect to health and the natural environment and its recycling and disposal. This paper is focused on the forming technology of threads and the application of selected polymers to the forming process. The measured and quantified criteria are torque and force loadings, energy consumption, and quality of the produced surfaces. Kistler dynamometers, scanning electron microscopy, and advanced surface topography with the use of Alicona IF-G5 were applied to assess all aspects of the tribological and energy aspects of six modern process fluids, three lubricating pastes, and two fluid modifications. The results show that the polymer synthetic lubricant (at volume concentration 20% in water) can reduce the total energy consumption by up to 40% per forming cycle (in mean values) at average surface roughness below 0.8 m
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    Cyclic Fatigue of Dental NiTi Instruments after Plasma Nitriding
    (MDPI, 2021-04-23) Bumbálek, Michal; Joska, Zdeněk; Pokorný, Zdeněk; Sedlák, Josef; Majerík, Jozef; Neumann, Vlastimil; Klíma, Karel
    This study investigated the possibility of nitride NiTi instruments using low-temperature plasma nitriding technology in a standard industrial device. Changes in the properties and fatigue life of used NiTi instruments before and after low-temperature nitriding application were investigated and compared. Nontreated and two series of plasma-nitrided NiTi instruments, designed by Mtwo company with tip sizes of 10/.04 taper, 15/.05 taper, and 20/.06 taper, were experimentally tested in this study. All these instruments were used and discarded from clinical use. The instruments were tested in an artificial canal made of stainless steel with an inner diameter of 1.5 mm, a 60° angle of curvature, and a radius of curvature of 3 mm. A low-temperature plasma nitriding process was used for the surface treatment of dental files using two different processes: 550 °C for 20 h, and 470 °C for 4 h. The results proved that it is possible to nitride dental instruments made of NiTi with a low-temperature plasma nitriding process. Promising results were achieved in trial testing by NiTi instruments nitrided at a higher temperature. Plasma-nitrided files were found to have, in some cases, significantly higher values than nontreated files in terms of fatigue life. The results showed that the nitriding process offers promising possibilities for suitably modified surface properties and quality of surface layer of NiTi instruments. Within the limitations of the present study, the cyclic fatigue life of plasma-nitrided NiTi dental files can be increased using this surface technology.
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    Material and Dimensional Analysis of Bimetallic Pipe Bend with Defined Bending Radii
    (Strojarski fakultet u Slavonskom Brodu, 2021-06-05) Slaný, Martin; Sedlák, Josef; Zouhar, Jan; Zemčík, Oskar; Chladil, Josef; Jaroš, Aleš; Kouřil, Karel; Varhaník, Matúš; Majerík, Jozef; Barényi, Igor; Čep, Robert
    This paper deals with material and dimensional bending analysis of bimetallic pipes with defined bending radii. Basic characteristics of selected nickel superalloys with analysis of Inconel 625 and 16Mo3 steel in terms of primary mechanical properties and chemical composition are presented. The practical part where the bimetallic tube is analyzed in terms of material properties is also performed geometric dimensional analysis, for which test specimens with different bending radii are made.
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    The design of a device for testing the tribological properties of knee endoprostheses
    (UJEP, 2021-09-18) Dobrovolná, Lucie; Varhaník, Matúš; Sedlák, Josef; Polzer, Aleš; Studený, Zbyněk
    The presented paper deals with the design of a knee simulator that uses pin-on-ball configuration, ie cartilage and CoCrMo head. The translational motion consists of the cartilage and the rotating head when the load of the articulating pair is derived. The simulator meets the predetermined kinematic conditions according to the ISO 14243-3 standard, including dynamic loading.
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    Application of Linear Optimization on Parameters of 3D FDM Print
    (Strojarski fakultet u Slavonskom Brodu, 2019-07-25) Zemčík, Oskar; Sedlák, Josef
    Nowadays, a fused deposition modelling (also called “FDM”) belongs to one of the most widespread additive methods of 3D print. It allows producing both models for functional verification or casts and functional components. The main advantage of this technology is an option to produce complex components of a difficult shape independent of their outer and inner surfaces. Moreover, this mentioned technology brings the decreasing of production costs in comparison with the other well-known additive methods. The final quality of a product depends on the used material and on technological conditions at the same time. The number of parameters and limits of the complete printing process is enormous. The choice of the individual parameters by a trial-and-error procedure is very time-consuming. Therefore, a use of linear optimization for finding of optimal values of chosen print parameters can be offered. For forming of the required procedures, it seems to be necessary to choose structural variables, find an appropriate objective function and deduce properly limiting conditions in a linear shape, which relates to a linear measurement. The final solution enables, on the basis of the selected initial conditions, to choose optimal parameters of the 3D print for a given material and production equipment in a relatively short period.