Ústav strojírenské technologie

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Study of micro structural material changes after WEDM based on TEM lamella analysis
(MDPI, 2020-06-07) Mouralová, Kateřina; Zahradníček, Radim; Beneš, Libor; Prokeš, Tomáš; Hrdý, Radim; Fries, Jiří
Wire electrical discharge machining is an unconventional machining technology that is crucial in many industries. The surface quality of the machined parts is carefully monitored, but the condition of the subsurface layer also plays a crucial role, especially in case of defects occurrence such as cracks or burnt cavities. The subsurface layer of individual materials is affected differently due to wire electrical discharge machining. For this reason, this study was carried out focusing on a detailed analysis of transmission electron microscope (TEM) lamellae made of Ti-6Al-4V titanium alloy, AlZn6Mg2Cu aluminium alloy, pure molybdenum, Creusabro 4800 steel, and Hardox 400 steel. The attention was first of all paid to the concentration and distribution of individual elements in the recast layer and also in the base material, which was often affected by Wire electrical discharge machining. Further, a diffraction analysis was performed for each TEM lamella in the adhesive area and in the area of the base material. In order to assess the macro-effects on the machined material, the analysis of the topography of the machined surfaces and the morphology analysis were performed using electron microscopy.
High-Temperature Creep Resistance of FeAlOY ODS Ferritic Alloy
(MDPI, 2024-10-01) Dymáček, Petr; Jarý, Milan; Bártková, Denisa; Luptáková, Natália; Gamanov, Štěpán; Bořil, Petr; Georgiev, Vjačeslav; Svoboda, Jiří
A significant effort in optimizing the chemical composition and powder metallurgical processing led to preparing new-generation ferritic coarse-grained ODS alloys with a high nano-oxide content. The optimization was aimed at high-temperature creep and oxidation resistance at temperatures in the range of 1100-1300 degrees C. An FeAlOY alloy, with the chemical composition Fe-10Al-4Cr-4Y2O3 (wt. %), seems as the most promising one. The consolidation of the alloy is preferably conducted by hot rolling in several steps, followed by static recrystallization for 1 h at 1200 degrees C, which provides a stable coarse-grain microstructure with homogeneous dispersion of nano-oxides. This represents the most cost-effective way of production. Another method of consolidation tested was hot rotary swaging, which also gave promising results. The compression creep testing of the alloy at 1100, 1200, and 1300 degrees C shows excellent creep performance, which is confirmed by the tensile creep tests at 1100 degrees C as well. The potential in such a temperature range is the target for possible applications of the FeAlOY for the pull rods of high-temperature testing machines, gas turbine blades, or furnace fan vanes. The key effort now focuses on expanding the production from laboratory samples to larger industrial pieces.
Quantification and Verification of Swingarm Structural characteristics through Numerical Simulation and Photogrammetry
(Jan Evangelista Purkyne Univ, 2024-11-28) Gregor, Lukáš; Zouhar, Jan; Kupčák, Radim
This article examines the torsional and vertical stiffness of a carbon fiber reinforced polymer (CFRP) single-sided swingarm for motorcycles. Using finite element analysis (FEA) and experimental measurements, the study evaluates the accuracy of stiffness simulations. Custom fixtures and a TRITOP photogrammetric system were employed to assess deformations under static loads. The results highlight discrepancies between simulation and reality, emphasizing the complexity of modeling CFRP components and the necessity of experimental validation.
Change in Dimensions and Surface Roughness of 42CrMo4 Steel after Nitridation in Plasma and Gas
(MDPI, 2022-10-06) Dobrocký, David; Pokorný, Zdeněk; Joska, Zdeněk; Sedlák, Josef; Zouhar, Jan; Majerík, Jozef; Studený, Zbyněk; Procházka, Jiří; Barényi, Igor
The influence of plasma nitriding and gas nitriding processes on the change of surface roughness and dimensional accuracy of 42CrMo4 steel was investigated in this paper. Both processes almost always led to changes in the surface texture. After plasma nitriding, clusters of nitride ions were formed on the surface of steel, while gas nitriding very often led to the new creation of a formation of a “plate-like” surface texture. In both cases of these processes, a compound layer in specific thickness was formed, although the parameters of the processes were chosen with the aim of suppressing it. After the optimizing of nitriding parameters during nitriding processes, it was found that there were no changes in the surface roughness evaluated using the Ra parameter. However, it turned out that when using a multi-parameter evaluation of roughness (the parameters Rz, Rsk and Rku were used), there were presented some changes in roughness due to nitriding processes, which affect the functional behavior of the components. Roughness changes were also detected by evaluating surface roughness profiles, where nitriding led to changes in peak heights and valley depths. Nitriding processes further led to changes in dimensions in the form of an increase of 0.032 mm on average. However, the magnitude of the change has some context on chemical composition of material. A larger increase in dimensions was found with gas nitriding. The change in the degree of IT accuracy is closely related to the change in dimension. For both processes, there was a change of one degree of IT accuracy compared to the ground part (from IT8 to IT9). On the basis of the achieved dimensional accuracy results, a coefficient of change in the degree of accuracy IT was created, which can be used to predict changes in the dimensional accuracy of ground surfaces after nitriding processes in degrees of accuracy IT3–IT10. In this study, a tool for predicting changes in degrees of accuracy of ground parts after nitriding processes is presented.
Study of dynamic behaviour via Taylor anvil test and structure observation of M300 maraging steel fabricated by the selective laser melting method
(Elsevier, 2024-07-20) Kolomý, Štěpán; Jopek, Miroslav; Sedlák, Josef; Zouhar, Jan
This paper deals with the M300 high strength maraging steel fabricated via selective laser melting method. Mechanical properties especially microhardness and compressive yield strength of maraging steel in as-printed state were observed. The acquired data was implemented in Johnson-Cook constitutive equation used for numeric simulation, which showed the satisfactory correlation with the observed experiment. Dynamic behaviour under high strain rate (impact velocity reached 185 m.s-1)- 1 ) was investigated via Taylor Anvil Test. The experiment revealed structure and geometrical changes accompanied with the creation of characteristic funnellike and cylindrical areas on the deformed sample. Impacted sample forehead featured the increase of micro- hardness (465 HV) accompanied with structure changes. The structure in the funnel-like area exhibited the decrease of average grain size, which reached the minimum (3.1 mu m) in the vicinity of the impacted forehead. Closer analysis revealed that the high strain rate caused the increase of high fraction high-angle grain boundaries (50,8 %) and higher geometrically necessary dislocation density (52.77 1.m-- 2 ) in the funnel-like area.

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