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Experimental Determination of Continuous Cooling Transformation Diagram for High Strength Steel X155CrMoV12
(Hrvatsko Metalursko Društvo, 2022-01-10) Krbaťa, Michal; Majerík, Jozef; Barényi, Igor; Eckert, Maroš; Čep, Robert; Sedlák, Josef; Samardžić, Ivan
The article is a result of investigations which deals with the phase transformations of tool steel X155CrMoV12. The experimental data obtained was used to evaluate the resulting Continuous Cooling Transform (CCT) diagram, which consists of seven dilation curves. All experimental samples from dilatometric analyzes were then subjected to microstructural analyzes and hardness measurements to characterize the microstructure and hardness for each heat treatment mode tested. Atomic Force Microscopy (AFM) microscopy was also used to study the carbides present in steels and their size and shape for all selected cooling modes.
Analysis of the Mechanical Properties of 3D-Printed Plastic Samples Subjected to Selected Degradation Effects
(MDPI, 2023-04-21) Sedlák, Josef; Joska, Zdeněk; Jánský, Jiří; Zouhar, Jan; Kolomý, Štěpán; Slaný, Martin; Švásta, Adam; Jiroušek, Jan
The Fused Filament Fabrication (FFF) method is an additive technology that is used for the creation of prototypes within Rapid Prototyping (RP) as well as for the creation of final components in piece or small-series production. The possibility of using FFF technology in the creation of final products requires knowledge of the properties of the material and, at the same time, how these properties change due to degradation effects. In this study, the mechanical properties of the selected materials (PLA, PETG, ABS, and ASA) were tested in their non-degenerate state and after exposure of the samples to the selected degradation factors. For the analysis, which was carried out by the tensile test and the Shore D hardness test, samples of normalized shape were prepared. The effects of UV radiation, high temperature environments, high humidity environments, temperature cycles, and exposure to weather conditions were monitored. The parameters obtained from the tests (tensile strength and Shore D hardness) were statistically evaluated, and the influence of degradation factors on the properties of individual materials was assessed. The results showed that even between individual manufacturers of the same filament there are differences, both in the mechanical properties and in the behavior of the material after exposure to degradation effects.
Dilatometric Analysis of Cooling Curves for High Strength Steel X155CrMoV12
(Hrvatsko Metalursko Društvo, 2022-01-10) Krbaťa, Michal; Majerík, Jozef; Barényi, Igor; Eckert, Maroš; Čep, Robert; Sedlák, Josef; Samardžić, Ivan
The article deals with phase transformations and austenitizing behavior of the X155CrMoV12 tool steel. Dilatation analyses of a series of samples were performed at various cooling rates, chosen in the range from 10 °C/s to 0,1° C/s. Acquired experimental data were used for evaluation of dilatometric curves in order to map the temperature ranges of phase transformations of the austenite to pearlite, bainite or martensite. All experimental samples from dilatometric analyses were then subjected to microstructural analyses and hardness measurements to characterize the microstructure and hardness for each tested heat treatment regime.
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
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.

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