Conference Papers (RTI)
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Item Vliv technologií a parametrů svařování na opravy forem určených pro práci za tepla(Západočeská univerzita v Plzni, 2025) Prokop, Jiří; Němeček, StanislavTato práce se zabývá vlivem technologických parametrů aditivních oprav a následného tepelného zpracování na výsledné mechanické vlastnosti a mikrostrukturu zhotovených návarů a přechodové oblasti návaru. Hlavním cílem je optimalizace oprav forem a nástrojů z nástrojové oceli H13 určených pro práci za tepla, a to pomocí metod WAAM a LMD. Práce zahrnuje experimentální porovnání navařovacích procesů s využitím přídavných materiálů Capilla 66, Capilla 733 a H13 následné tepelné zpracování a destruktivní testování pro vyhodnocení odolnosti proti opotřebení povrchu návaru. Výsledky přispívají k efektivnějším metodám opravy forem s ohledem na jejich životnost a mechanické vlastnosti.
Item Experiments to support the improvement of the integrity and resistance of the bus bodywork in a rollover accident(Elsevier Science BV, 2023) Kepka, Miloslav; Volák, Josef; Minich, Radovan; Martinů, Michal; Pavlata, Petr; Dopierala, Lukasz; Walczak, BartlomiejThe article provides an overview of mechanical tests carried out at the Regional Institute of Technology, a research center of the Faculty of Mechanical Engineering of the University of West Bohemia in Pilsen, in cooperation with other organizations. They aimed to obtain input data for the computational simulation of bus overturns according to prescribed standards and experimentally validate these calculations. The specific results of these tests are not given, as they are subject to trade secrets.
Item Simple and Advanced Technologies to Improve the Properties of Metal Additive Manufacturing Products(Scisynopsis LLC, 2023) Nozar, MartinThis contribution describes the experience with metal additive manufacturing of difficult-to-manufacture industrial components, prototypes, and topologically optimized cutting tools which were manufactured using the EOS M290 machine and from Maraging Steel MS1 or Inconel 718 nickel-chromium alloy. In addition to that, there are several experiments presented here that were conducted to investigate the usefulness of methods like time and energy input homogenization and possibilities of process parameters optimization which, on the one hand, could prevent printed parts from warping, overheating, non-uniform shrinking, and excessive residual stress, and on the other hand, could ensure better surface quality even for down-faced surfaces inclined at relatively small angles printed without support structures.Finally, this contribution describes the utilization of software simulation and an advanced In-situ process monitoring system which were used to examine the suitability of the modified process parameters, observe their effect in real-time and enables early detection and correction of any process faults and defects.Item Adhesion of selected thermally sprayed coatings on additive manufactured maraging steel(IOP Publishing Ltd, 2023) Dlouhá, Žaneta; Vostřák, Marek; Duliškovič, Josef; Zetková, Ivana; Mařík, TomášAdditive manufacturing (AM) technology is increasingly expanding into different types of industries. Still, many potential applications are restricted due to the limited choice of materials used in AM. A suitable solution could be a combination of AM and thermal spraying of functional parts of the surface to achieve superior surface properties. This work aims to study the possibility to prepare the surface with AM technology to direct application of coating by thermal spraying without any additional surface preparation. To verify this possibility, the parameters of the 3D printing technology were adjusted to achieve suitable surface structures for the following thermal spraying. Several variants of modifications with different surface properties were selected. The samples were printed from maraging steel using the DMLS technology. The coatings chosen for testing were WC – CoCr and Stellite 6 sprayed by HVOF and further NiAl and Al2O3-TiO2 sprayed by APS. The adhesion of the coating was tested by an adhesion test performed under the ASTM C633-79 standard. The bonding of the coating on the surface was studied by metallographic analysis. The achieved results indicate that the adhesion of HVOF sprayed WC-CoCr coating on 3D printed surfaces is excellent for most surface modifications. The Stellite 6 exhibits good adhesion on several surface modifications. The APS sprayed coating shows significantly lower adhesion, the NiAl and Al2O3-TiO2 coatings can be successfully sprayed only on selected surface modificationsItem Parametric predictions of fatigue life of printed samples from MS1 and 316L materials(Elsevier Science BV, 2024) Štěpánek, Martin; Zetek, Miroslav; Zetková, Ivana; Kepka, Miloslav; Margetin, Matus; Chmelko, Vladimir; Kepka, MiloslavThe conference paper presents the activities carried out within the framework of Czech-Slovak cooperation in order to obtain data and improve knowledge for predicting the fatigue life of multiaxially loaded components, printed from MS1 and 316L materials using DMLS technology. Techsim Engineering Ltd., SME company from Prague, distributor of Siemens software, mainly dealt with topological optimization of components and project management. The researchers of the Regional Technological Institute, which is a research center of the University of West Bohemia in Pilsen, were mainly responsible for printing test samples and specific components, they also dealt with topological optimization and experimental verification of the properties of functional samples of the developed components. The Faculty of Mechanical Engineering of the Slovak University of Technology in Bratislava ensured fatigue tests of the materials under uniaxial and combined loading. The contribution describes the basic technical conditions of the project and the chosen methodological procedure.Item Characterization of Flame Sprayed Abradable Seal NiCrAl-Bentonite Coatings(Tanger, 2018) Houdková, Šárka; Schubert, Jan; Česánek, Zdeněk; Lukáč, František; Bystrianský, MartinThe NiCrAl-21% Bentonite abradable coating, deposited by flame spraying, was exposed to 720 degrees C / 1 hour air-annealing to evaluate its resistance against heat-induced changes. The SEM and XRD microstructure evaluation was done. After the air-annealing, the increase of HR15Y surface hardness was recorded and accompanied with decrease of abradability evaluated by Progressive Readability Hardness (PAH) test, although no demonstrable microstructural changes was recorded by SEM. XRD analyses evidenced the formation of nickel oxides and ordered Ni3Al phase during the air-annealing. Besides the abradable coating evaluation, this work brings the verification of the potential of PAH for scratch hardness testing. The measurement provides the results with low scatter, compared to usual surface hardness testing, and enables to distinguish between the depth of indentation in loaded and unloaded state, pointing out to the elastic/plastic deformation ratio.Item Degradation Mechanism Study of Selected Thermally Sprayed Coatings in the Environment of Steam Turbine(Tanger, 2019) Houdková, Šárka; Prantnerová, Michaela; Bystrianský, Martin; Lukáč, FrantišekIn the paper, the influence of high temperature and hot pressure steam on the microstructure and phase composition of HVOF sprayed wear resistant Cr3C2-NiCr coating and flame sprayed NiCrAl-Bentonite abradable coating is studied. Both the results of laboratory oxidation tests and the long-term exposition tests in the steam turbine are presented. The mechanism of selective carbide oxidation was observed in both laboratory test and long-term oxidation test in the case of HVOF Cr3C2-NiCr coating. The oxidation of NiCrAl matrix of flame spray abradable coating is described. Both coatings suffered from oxidation, but their integrality was not disrupted even after 5.5 years of exposition in steam turbine environment.Item Cyclic strain rate dependent behaviour of Alloy 617(Elsevier B.V., 2024) Dewa, Rando Tungga; Kepka, Miloslav; Kim, Seon-JinThis paper investigates the effect of strain rate on the properties of Alloy 617 under low-cycle fatigue (LCF) at room temperature (RT). The LCF life properties and damage mechanism are studied for this alloy over a range of strain rates (5E-4 ~ 1E-2 s-1) under a fully-reversed controlled total strain range of 1.2%. It is found that the LCF life of Alloy 617 is strongly influenced by time-dependent mechanisms, in terms of slow strain rate testing (SSRT). The relationship between total strain, plastic strain, and time to failure with strain rates is established and expressed by means of a power law function to describe fatigue life. Metallographic examination is carried out on the fractured specimens with the help of an electron microscope, and fractography is discussed to distinguish the effect of SSRT on the physical damage characteristics under LCF loadingItem Applications of additive technologies in the maintenance of machinery and equipment(Elsevier B.V., 2024) Kepka, Miloslav; Zetek, Miroslav; Zetková, Ivana; Bakir, Yusuf; Chval, Zdeněk; Zahálka, Martin; Kalina, Tomáš; Křížek, MichalRegional Technological Institute, the research center of the Faculty of Mechanical Engineering at the University of West Bohemia in Pilsen, operates some technologies for additive manufacturing. This is powder bed fusion technology for metal printing and some technologies for printing composite materials and plastics. The necessary tools for reverse engineering, support calculations, in-service measurements, laboratory tests and material analysis are available. The contribution presents the potential of additive technologies in the maintenance of machines and equipment. Examples of printed spare parts are shown and commented on.Item Advances in the computational-experimental assessment of fatigue life of welded joints of bus bodyworks(University of West Bohemia, 2024) Kepka, Miloslav; Kepka, Miloslav; Minich, RadovanAdvances are described in the computational-experimental assessment of fatigue life of welded joints of bus bodyworks.Item Thermally Sprayed HVOF Coatings for Steam Turbine Applications(INEGI-Instituto de Ciência e Inovação em Engenharia Mecânica e Engenharia Industrial, 2020) Houdková, Šárka; Prantnerová, Michaela; Bystrianský, Martin; Lukáč, FrantišekThe demands imposed on the coated components differ according to their purpose. Nevertheless, all the used materials have to resist degradation due to the influence of the surrounding environment. In the most challenging areas of applications, such as the power industry, the high temperature is often accompanied by a corrosive-aggressive environment, further increasing the materials requirements. In such conditions, the superior thermally sprayed coatings can be applied to increase the components wear resistance simultaneously to oxidation protection. The paper is focused on the evaluation of HVOF (High Velocity Oxygen Fuel) sprayed Co and Ni superalloy coatings behavior at room and high temperature under different types of mechanical loading and their resistance to high temperature oxidation, in comparison with CrC-based hardmetal coatings. The heat-induced microstructure changes are discussed, together with the potential of intentional heat-treatment for performance improvement. In general, the superalloy coatings proved its superior properties and performance in the demanding environment despite of being less wear resistant compare to hardmetals.Item Knowledge base for fatigue life evaluation of bodyworks of buses, trolley-buses, and battery-buses(Elsevier B.V., 2024) Minich, Radovan; Kepka, Miloslav; Kepka, MiloslavOver the last thirty years, Research and Testing Institute Pilsen (former SKODA RESEARCH) has been developing a complex methodology of computational and experimental investigation of strength and fatigue life of bodyworks of road vehicles for mass passenger transport (buses, trolleybuses, currently battery electro-buses). The methodology continues to be developed in cooperation with the Regional Technological Institute, which is a research center of the Faculty of Mechanical Engineering of the University of West Bohemia in Pilsen. Research and development are carried out in cooperation with various domestic and foreign manufacturers of city road vehicles. The amount of collected results already allows the creation of a knowledge base for the quantitative evaluation of the fatigue strength of newly developed bodyworks.Item Poznatky z experimentálního výzkumu únavové pevnosti a životnosti svařenců s aplikací vysokofrekvenčního mechanického zpevňování(Západočeská univerzita v Plzni, 2024) Kepka, Miloslav; Kepka, MiloslavPro zvyšování únavové pevnosti a životnosti svařovaných spojů, vyrobených zejména z vy-sokopevnostních ocelí, se ukazuje jako perspektivní aplikace metody HFMI (High Frequency Mechanical Impact). Doporučení IIW (International Institute of Welding) bylo v posledních letech předmětem intenzivního experimentálního výzkumu v Regionálním technologickém in-stitutu (RTI), výzkumném centru Fakulty strojní ZČU v Plzni. Příspěvek tyto výsledky prezen-tuje. Hodnotí také přínos metody HFMI při aplikaci na opravné svary a doporučuje další směry výzkumu.Item Experience with high-frequency mechanical impact method for weldments of sheets of different thicknesses(Elsevier B.V., 2024) Kepka, Miloslav; Tittel, Jan; Kepka, Miloslav; Žlábek, Pavel; Jansa, Zdeněk; Minár, JanThe interim results of two projects of the Technology Agency of the Czech Republic are presented, the subject of which is the verification of the potential of the industrial use of the high-frequency mechanical impact (HFMI) method for increasing the load-bearing capacity and fatigue of the material. The fatigue life of welds of steel sheets of various thicknesses and in a wide range of strengths of welded steels for the construction of rolling stock and steel bridges are experimentally verified. The authors have already presented partial results, Kepka jr. et al. (2022). The new results are based on a larger number of test samples. First findings on the application of the HFMI method to thin (4 mm) and very thick (90 mm) sheet welds are included. The results are compared with the general recommendation of the International Institute of Welding (2016). Partial attention was also paid to the endurance of compressive stresses introduced into the weld area by the application of HFMI. The fatigue tests were completed by measuring residual stresses by X-ray diffraction on selected test specimens with the application of HFMI before and after the completion of 10 million loading cycles.Item Opportunities and partial problems of HFMI implementation in design of welded structures of rail vehicles(Elsevier Science BV, 2022) Kepka, Miloslav; Kepka, Miloslav; Tittel, JanThis paper highlights the main impacts of HFMI (High Frequency Mechanical Impact) technology on increasing the fatigue resistance and extending the fatigue life of welded joints. In the case study there are SN curves of T-welded joints made of two different steels (conventional steel S235JR and high-strength steel S460MC). For both materials there is a comparison of SN curves with and without HFMI treatment. Both samples are loaded by bending for cycle asymmetry R = 0. The failure criterion is a decrease in stiffness caused by the formation of a macrocrack. The results of fatigue testing are then applied in a parametric study, which assumes a random loading of a selected structural detail in a railway application. Opportunities and barriers of the implementation of HFMI in practice are mentioned and documented according to results of laboratory experiments, which take place in cooperation with the university research center and the manufacturer of railway vehiclesItem Strength calculations and fatigue tests of welded bus bodywork nodes(Elsevier Science BV, 2022) Kepka, Miloslav; Kepka, Miloslav; Minich, RadovanLaboratory fatigue life tests were performed for several structural variants of welded nodes of thin-walled profiles of a bus bodywork. The laboratory fatigue tests were supported by FEM calculation and strain gauge experimental stress analysis. S-N curves were evaluated and used to predict the fatigue life of these structural nodes under random operational loading of the vehicle bodywork. Measuring systems for on-line monitoring of stresses in the vehicle bodywork have been developed and applied.Item Improving of mechanical properties of printed maraging steel(Elsevier B.V., 2024) Zetková, Ivana; Thurnvald, Petr; Bohdan, Petr; Trojan, Karel; Čapek, Jiří; Ganev, Nikolaj; Zetek, Miroslav; Kepka, Miloslav; Kepka, Miloslav; Houdková, ŠárkaThis contribution investigates the effects of process parameter changes on residual stresses in printed maraging steel X3NiCoMoTi18-9-5. A series of samples was produced using direct metal laser sintering (DMLS) on an EOS M290 machine. Printed components typically exhibit undesirable tensile residual stresses (RS), which can lead to deformations and cracks. To reduce RS, different parameter sets were tested. The following parameters were tested: change of the build strategy from stripes to chessboard, time homogenization, change of the complex VED parameter, thermal treatment modification, and building platform preheating change. Residual stress evaluation was performed using the drilling method in subsurface area and X-ray diffraction in the surface area.Item Optimization of 3D Printing Parameters to Minimize Residual Stresses in Maraging Steel(2024) Trojan, Karel; Zetková, Ivana; Čapek, Jiří; Thurnvald, Petr; Ganev, Nikolaj; Kepka, MiloslavDuring additive manufacturing using the selective laser melting technology, a complex residual stress distribution is created that can significantly affect the printing itself and also the mechanical properties of the final product. Thus, this research has been carried out to optimize 3D printing parameters to minimize residual in maraging steel. It was found that the preheating temperature of the build platform significantly affects both the residual stresses and microstructure parameters as well as the mechanical properties.Item Návrh komplexního procesu indukčního zpracování rychlořezné oceli pro výrobu kovářských svarů(Asociace pro tepelné zpracování kovů, z.s., ECOSOND s.r.o., 2023) Opatová, Kateřina; Benešová, Soňa; Jeníček, Štěpán; Němeček, StanislavCílem článku bylo navrhnout a popsat komplexní postup pro získání tepelně zpracovaného nástroje na soustružení s navařenou břitovou destičkou vyrobenou z rychlořezné oceli (HSS) a to celé za pomoci indukčního ohřevu. Tento postup nahradil původní dlouhou sekvenci operací, která původně zahrnovala ohřev sestavy lůžka soustružnického nože a břitové destičky na teplotu 1200 °C v prostoru komorové pece před kováním. Následně bylo provedeno kování pomocí hydraulického lisu, a po ochlazení na RT samostatný režim tepelného zpracování. Nový postup byl navržen tak, aby se kování uskutečnilo současně s tepelným zpracováním, což eliminovalo potřebu mezioperačních kroků při použití komorové pece. Zkrácení procesu bylo dosaženo instalací indukčního ohřevu do prostoru hydraulického lisu. Induktor cíleně ohřál konkrétní část lůžka nože s HSS břitovou destičkou, a ihned poté proběhlo kování pro svaření a tepelné zpracování bez ochlazení.Vývoj této technologie vedl k výrobě soustružnického nože vhodného pro speciální obráběcí operace, jako je obrábění s přerušovaným řezem. Tato obráběcí operace vyžaduje nástroje s vysokou houževnatostí, kterou mohou poskytnout oceli HSS, na rozdíl od nástrojů vyrobených ze slinutých karbidů. HSS ocel byla po tepelném zpracování podrobena metalografické analýze a měření tvrdosti. Výsledky výzkumu byly ověřeny testy opotřebení během obrábění, které zkoumaly funkční vlastnosti kované a tepelně zpracované oceli HSS po kování.Item Topological optimization of the milling head(Springer Singapore, 2022) Ráž, Karel; Štěpánek, Martin; Chval, ZdeněkTento článek popisuje využití topologické optimalizace v procesu návrhu frézovací hlavy. Byla zvolena moderní frézovací hlava (inovativní design s prutovou konstrukcí) s vnitřním přívodem chladicí kapaliny. Užitné vlastnosti hlavy byly zvýšeny pomocí topologické optimalizace. Životnost nebyla snížena a změny hmotnosti jsou popsány v příspěvku. Hlava je vyrobena aditivní technologií DMLS (Direct Metal Laser Sintering) z oceli MS1. Pro simulaci byl použit software Siemens NX a jeho funkce (řešič topologie Frustum a strukturální řešič NX Nastran). Pro ověření výsledků byla porovnána tuhost několika konstrukcí frézovací hlavy s původním řešením. Další výzkum bude zaměřen na samotné testování optimalizované hlavy
