Browsing by Author "Nováková, Iva"
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- ItemApplication of Numerical Simulations on 10GN2MFA Steel Multilayer Welding(SPRINGER INTERNATIONAL PUBLISHING AG, GEWERBESTRASSE 11, CHAM, CH-6330, SWITZERLAND, 2019-09-27) Kik, Tomasz; Moravec, Jaromír; Nováková, Iva10GN2MFA steel is used to produce wire and manufacturing of steam generators, pressure compensators, collectors and other equipment for nuclear power plants. In this area, there is no place to do any mistakes during manufacturing or carrying out extensive tests and producing a lot of prototypes. It is the main reason whywe usedmodern software for numerical simulation ofwelding and heat treatment processes also on the very early stage of development. The aim of this paper is to describe how can welding processes be optimized by means of the numerical simulations mainly with respect to the structural changes, stresses and hardness distribution in the Heat Affected Zone (HAZ). On the real multilayer weld how to arrange whole experiment in order to obtain not only relevant input data but also verification data will be described. Additional aim of this paper is to propose mathematical description of the computational model that is usable for simulation computations of welding and heat treatment of real structure components.
- ItemApplication possibilities of the low-temperature repairs on creep-resistance turbine components from material GX23CrMoV12-1(2018) Moravec, Jaromír; Nováková, Iva; Sobotka, Jiří; Kik, TomaszPapers deals with the problems of repairs at new and also already loaded components of steam and gas turbines. Generally, it is about welding repairs at valve and turbine chambers, transmitters, vane carriers, tripping valve body and so on. There are both technological defects caused by casting (e.g. shrinkage cavities, misruns, porosity and cracks) and defects caused by operation (thermal-stress fatigue, incorrect method of operation, etc.). Many of the mentioned defects take effect not until the final technological method - mostly at machining. However, in this production phase it is not possible to get form the supplier new production elements due to economical and also delivery time reasons. All of that results in delay of production and penalty. As the major aim of this paper, there was to find such repairs techniques which can ensure serviceability of mentioned devices under the standard regime. In these cases is needed to use much lower tempering temperature than under the standard production, mainly because of necessity to eliminate deformation caused by heating of part that is not possible to be subsequently removed by machining.
- ItemDetermination of Grain Growth Kinetics and Assessment of Welding Effect on Properties of S700MC Steel in the HAZ of Welded Joints(2019-06-24) Moravec, Jaromír; Nováková, Iva; Sobotka, Jiří; Neumann, HeinzThe welding of fine-grained steels is a very specific technology because of the requirement for the heat input limit value. Applying temperature cycles results in an intense grain growth in a high-temperature heat-affected zone (HAZ). This has a significant effect on the changing of strength properties and impact values. The intensity of grain coarsening in the HAZ can be predicted based on the experimentally determined activation energy and material constant, both of which define grain growth kinetics. These quantities, together with real measured welding cycles, can be subsequently used during experiments to determine mechanical properties in a high-temperature HAZ. This paper shows a methodical procedure leading to the obtainment of the material quantities mentioned above that define the grain growth, both at fast and slow temperature cycles. These data were used to define the exposure temperature and the soaking time in a vacuum furnace to prepare test samples with grain sizes corresponding to the high-temperature HAZ of welded joints for the testing procedures. Simultaneously, by means of the thermo-mechanical simulator Gleeble 3500, testing samples were prepared which, due to a temperature gradient, created conditions comparable to those in the HAZ. The experiments were both carried out with the possibility of free sample dilatation and under a condition of zero dilation, which happens when the thermal expansion of a material is compensated by plastic deformation. It has been found that shape of the temperature cycle, maximal achieved cycle temperature, cooling rate, and, particularly, the time in which the sample is in the austenite region have significant effects on the resulting change of properties.
- ItemInfluence of the welding process on the change of mechanical properties in the HAZ of welds at alloy AW 6005 and possibilities of their renewal by heat treatment(J. E. Purkyne University in Usti nad Labem, 2019) Nováková, Iva; Moravec, Jaromír; Švec, Martin; Kik, Tomáš; Koreček, DavidThis paper deals with monitoring the influence of welding on the mechanical properties degradation in HAZ of welds at aluminium alloy AW 6005 and also with assessing the possibility of utilization the heat treatment to minimize these effects. Workpieces from alloy AW 6005 are mostly supplied in aged state. After application of the temperature cycles during welding, there is a very intensive decrease of the mechanical properties in HAZ. The mechanical properties of the weld metal, HAZ and parent material were evaluated by means of the Vickers hardness. Moreover, influence of annealing and artificial aging on the final mechanical properties of the parent material was also evaluated. Based on the results, there were chosen the relevant heat treatment parameters, which were subsequently applied in order to recover the mechanical properties of welds in the HAZ.
- ItemMarketingová komunikace vybraných sportovních klubů v Liberci(Technická Univerzita v Liberci, 2008) Nováková, Iva; Martinec, Jindřich
- ItemMetalurgické zásady a možnosti výroby odlitků ze slitin hořčíku(Technická Univerzita v Liberci, 2010) Černoch, Adam; Nováková, IvaThis thesis is concerning about the problems of production of casting from magnesium alloys. As the way of elaboration was selected literature retrieval. The main attention is paid to the preparing and removal of the molten and also to the possibilities of the different production of castings. In the end of this thesis is mentioned the heat-treating process and surface-removal process, which are the most important part of each produced casting from magnesium alloys.
- ItemNekonvenční způsob chlazení kritických oblastí tvarových částí tlakových licích forem(Technická Univerzita v Liberci, 2015-10-19) Nováková, Iva; Katedra strojírenské technologieOptimální teplotní podmínky tlakové licí formy zajišťuje v průběhu licího cyklu temperanční systém. Ve většině českých sléváren se používá temperanční systém tvořený soustavou navzájem propojených kanálů převážně rovnoběžných s dělící rovinou, kterými proudí temperanční médium. Tento systém umožňuje před začátkem výroby tlakovou licí formu předehřát na provozní teplotu a během lití udržovat tepelnou rovnováhu mezi odlitkem a formou. Neumožňuje však odvádět teplo z tvarových částí malých průřezů. U těchto míst dochází k přehřívání formy. To vede jednak k porezitě odlitku v dané oblasti a jednak k nedostatečnému ošetření kritických míst formy, které způsobí snížení jejich životnosti. Jednou z nových možností chlazení těchto kritických míst je jejich chlazení pomocí kapalného CO2. V rámci řešení byla ověřována aplikace tohoto způsobu chlazení do jádra tlakové licí formy, dále byla sledována a vyhodnocena kvalita odlitků.
- ItemA new type of ductile iron for the automotive industry(Technická univerzita v Liberci, Česká republika, 2009) Nová, Iva; Nováková, Iva; Machuta, JiříPříspěvek se zabývá výrobou litiny s kuličkovým grafitem s vyšším obsahem křemíku. Byl hledán konstrukční materiál, který by vykazoval homogenitu mechanických vlastností v různých stěnách odlitku. To splňuje feritická litina s kuličkovým grafitem typu 400 – 15, pevností Rm 400 MPa. Tento materiál má lepší obrobitelnost než tradiční typy litiny s kuličkovým grafitem. V současné době se zabýváme na Katedře strojírenské technologie Fakulty strojníTechnické univerzity v Liberci metalurgickou výrobou litiny s kuličkovým grafitem s vyšším obsahem křemíku a v tomto příspěvku prezentujeme naše výsledky.
- ItemNUMERICAL SIMULATIONS OF X22CrMoV12-1 STEEL MULTILAYER WELDING(POLSKA AKAD NAUK, POLISH ACAD SCIENCES, INST METALL & MATER SCI PAS, PL, 00-901 WARSZAWA, POLAND, 2019) Kik, Tomasz; Moravec, Jaromír; Nováková, IvaThe aim of this paper is to present the procedure test for calibration and validation of the numerical model for X22CrMoV12-1 steel multilayer welding. On the real multilayer weld was described how to arrange the whole experiment in order to obtain not only relevant input data but also verification data. Tests on a specially prepared specimen, welded with 8 beads in 4 layers, allows to determine the actual geometry of the single welded beads, registration of welding thermal cycles and the hardness distribution in successively deposited beads together with determining the heat influence of subsequent layers. The results of the real welding tests were compared with the results obtained from the numerical simulations and extended by the calculated stresses and distortions distributions of the tested specimen. A new, improved hardness prediction algorithm for high-alloy martensitic and bainitic steels was also proposed.
- ItemOpravy tlakových licích forem pro výrobu odlitků ze slitin hliníku(Technická Univerzita v Liberci, 2013) Beranová, Dita; Nováková, IvaCílem experimentální části této bakalářské práce bylo navrhnout parametry renovačního procesu u poškozených částí tlakové licí formy, v našem případě jádra. Experimentální práce byly realizovány s firmou DGS Druckguss Systeme, s. r. o. v Liberci. Místa návaru byla vybrána tak, aby reprezentovala obdobná místa v poškozených oblastech formy. Při vyhodnocování návarů v laboratořích katedry strojírenské metalurgie TUL byla pozornost soustředěna na oblasti návarů, ve kterých se mohla vyskytnout nežádoucí poškození a na místa s možným nežádoucím poklesem mechanických vlastností.
- ItemPossibilities of using interlayers during diffusion welding of Ti Gr2 and AISI 316L(2018) Moravec, Jaromír; Nováková, Iva; Kik, TomaszJoining of materials with different physical and mechanical properties is always very problematic. As one of the possibilities, there can be used method of joint creation in solid state - e.g. by the diffusion welding. With this method it is possible to joint very different materials - even metals with non-metals. Despite the unquestionable advantages of this method, there is necessary to take into account also its limits. Among of them, there is creation of brittle intermetallic phases on the boundary of materials. This occurs e.g. at creation heterogeneous joints between titanium and highly- alloyed austenitic steel. The major aim of this paper is to describe how it is possible to eliminate brittle intermetallic phases created on boundary between Ti Grade 2 and AISI 316L steel by using metal interlayers.
- ItemPrecipitační vytvrzování odlitků ze slitin hliníku(Technická Univerzita v Liberci, 2009) Krejčí, Tomáš; Nováková, IvaThis bachelor thesis deals with precipitation hardening of aluminum alloys. The work is of searching character. There are property descriptions of aluminum and its alloys, summary of aluminum alloys divided to hardenable and unhardenable and physical-metallurgical principle of hardening.
- ItemPrediction of foaming process in the production of aluminium foams(J. E. Purkyne University in Usti nad Labem, 2019) Nová, Iva; Sobotka, Jiří; Fraňa, Karel; Solfronk, Pavel; Koreček, David; Nováková, IvaThe paper deals with the physical-chemical effects of a blowing agent on production the cellular metal systems (in this case aluminium foams). Based on the isothermal concertation and pressure curves for the H-Ti system and by using the maximum gas volume obtained from equation of state, there was applied the blowing agent to 1 kg of AlSi12 aluminium alloy. Moreover, using relation to determine aluminium foam relative density (ρREL) from alloy AlSi12, there was done prediction to determine density of 1 kg metal foam from AlSi12 alloy at different blowing agent contents from 0.1 up to 1.5 wt% of titanium hydride TiH2. These isothermal calculations were compared with the density of aluminium foal from alloy AlSi12, which was produced by an industrial process. Basic mechanical properties were subsequently measured on the produced foam samples.
- ItemThe prediction of grain size of the heat affected zone of welded s304h steel tubes using a mathematical model(Technická univerzita v Liberci, Česká republika, 2013) Moravec, Jaromír; Bradáč, Josef; Nováková, Iva; Neumann, HeinzAustenitické oceli S304H se využívají především pro parní kotle tepelných elektráren a jiných energetických zařízení. Jednou z nejdůležitějších vlastností u trubek v parních kotlích je jejich vysokoteplotní odolnost. Rozdíly materiálových vlastností ocelí S304H, především creepové odolnosti, v porovnání s austenitickými ocelemi obdobného složení jsou dosaženy hlavně přidáním cca 3 hm. % mědi. Tvorba na měď bohatých precipitátů během provozu vede ke zvýšení creepové odolnosti precipitačním zpevněním. Příspěvek popisuje vliv svařovacího cyklu u materiálu S304H na zhrubnutí zrna v tepelně ovlivněné oblasti. Budou také uvedeny možnosti a způsoby predikce velikosti zrna pomocí numerických simulací svařování a tepelného zpracování. Dále bude ukázán a popsán princip získávání vstupních dat potřebných pro numerické simulace predikující velikost zrna.
- ItemProduction of porous aluminium using sodium chloride(J. E. Purkyne University in Usti nad Labem, 2020-01-07) Fraňa, Karel; Nová, Iva; Sobotka, Jiří; Solfronk, Pavel; Koreček, David; Nováková, IvaOur workplace, Technical University of Liberec, is currently engaged in research and production of cellular metal systems. Basically, cellular metal systems are materials with lower density. It is a research in the field of mechanical engineering that is focused on the development of new materials. In general, many methods have been developed for the p oduction of cellular metal systems, e.g. by BANHART [2] or ASHBY [4]. At their production, the direct gassing of molten metals (mostly aluminium ones) or gassing by the powder agents (e.g. specially formulated aluminium powders) are mostly used. Depending on the manufacturing method, a cellular system with open or closed cells can be obtained. The most commonly used metal is aluminium and its alloys. We are currently focusing on the production of porous aluminium by using sodium chloride. Sodium chloride occupies regular sites in the aluminium material and thus contributes to the aluminium porosity. After solidification of the aluminium, sodium chloride is dissolved in water. Sodium chloride is relatively inert to the aluminium and together with it, has a favourable density (2160 kg·m-3) compared to the aluminium density (2700 kg·m-3). The values of these physical quantities were observed on the produced aluminium test specimens having O 60 × 10 mm: relative density of porous system ρREL; porosity of metal system P; amount of solid phase system volume fraction VPM; density of porous metal system ρPM and porous material Young's modulus of elasticity EPM.
- ItemSledování životnosti tlakových licích forem(Technická Univerzita v Liberci, 2016) Dobeš, Jan; Nováková, IvaTato diplomová práce je zaměřena na problematiku degradačních procesů a s nimi spojených poškození líce forem pro tlakové lití hliníku během jejich provozu. Teoretická část práce je věnována nejvýznamnějším vlivům ovlivňujících životnost. Ve spolupráci s firmou Beneš a Lát byly dále zkoumány čtyři typy takovýchto porušení. Cílem práce je určit pravděpodobnou příčinu vzniku těchto porušení a uvést kroky vedoucí k jejich eliminaci u podobných aplikací
- ItemSpisovnost a nespisovnost ve vybraných rozhlasových pořadech(Technická Univerzita v Liberci, 2010) Nováková, Iva; Röhrich, Alex
- ItemTechnologie I.-Slévárenství, svařování, základy ochrany kovů proti korozi(2019) Nová, Iva; Nováková, Iva