Wyniki wyszukiwania - Biblioteka Nauki

1

Solidification of superalloys in shell moulds and its numerical simulation

100%

Roučka J. , Kováč M. , Odložil J. , Hrbáček K.

Archives of Foundry Engineering

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2010

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tom Vol. 10, iss. 1

137-146

EN

The paper presents the results of the experiments on the solidification of superalloys in shell moulds. The analysis of heat transfer during the solidification of castings in ceramic moulds was carried out theoretically and confirmed by the results of earlier experiments conducted on model shells. Results of experimental temperature measurement were compared with numerical calculations (performed using the ProCast software) and corrections of the calculation parameters were proposed. A model of structure simulation was verified on a selected real casting. It can be assumed that simulating the structure will be a theoretically and computationally demanding problem.

2

Study of Casting and Solidification of Slab Ingot from Tool Steel Using Numerical Modelling

88%

Tkadlečková M. , Michalek K. , Machovčák P. , Kováč M. , Socha L.

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tom Vol. 60, iss. 4

2879--2886

EN

The main problem in the production of forgings from tool steels, especially thick plates, blocks, pulleys and rods which are used for special machine components for demanding applications, it is the inhomogeneous structure with segregations, cracks in segregations or complex type of non-metallic inclusions MnS and TiCN. These forgings are actually produced from conventional forging ingots. Due to the size of forgings, it would be interesting the production of these forgings from slab ingots. It is possible that the production of forgings from slab ingots (which are distinguished by a characteristic aspect ratio A/B), it would reduce the occurrence of segregations. The paper presents the verification of the production process of slab steel ingots in particular by means of numerical modelling using finite element method. The paper describes the pre-processing, processing and post-processing phases of numerical modelling. The attention was focused on the prediction of behavior of hot metal during the mold filling, on the verification of the final porosity, of the final segregation and on the prediction of risk of cracks depending on the actual geometry of the mold.

PL

Głównym problemem w produkcji odkuwek ze stali narzędziowych, szczególnie grubych płyt, bloków, kół pasowych i prętów, używanych do specjalnych elementów maszyn dla żądanych zastosowań, jest niejednorodna struktura z segregacją, pęknięciami w segregacji lub złożonego typu niemetaliczne wtrącenia MnS i TiCN. Te odkuwki są rzeczywiście produkowane z konwencjonalnych wlewków przeznaczonych do kucia. Ze względu na wielkość odkuwek, można by produkować te odkuwki z wlewków płaskich. Możliwe, że produkcja odkuwki z wlewków płaskich (które wyróżniają się charakterystycznym stosunkiem A/B), pozwoli zmniejszyć występowanie segregacji. W pracy przedstawiono weryfikację procesu produkcji wlewków płaskich za pomocą modelowania numerycznego z wykorzystaniem metody elementów skończonych. Artykuł opisuje fazy modelowania numerycznego: wstępną fazę przetwarzania, obróbkę i przetwarzanie końcowe. Zwrócono uwagę na zachowanie się ciekłego metalu podczas napełniania wlewnic, na weryfikację końcowej porowatości, końcowej segregacji i przewidywania ryzyka pęknięcia w zależności od rzeczywistej geometrii wlewnic.

3

Study of Casting and Solidification of Slab Ingot from Tool Steel Using Numerical Modelling / Modelowanie Numeryczne Odlewania I Krzepnięcia Wlewków Stalowych Ze Stali Narzędziowej

88%

Tkadlečková M. , Michalek K. , Socha L. , Machovčák P. , Kováč M.

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nr 4

4

The network of permanent GPS stations in Central Europe as the reference for CERGOP related activities

88%

Hefty J. , Gerhátová L. , Igondová M. , Kováč M. , Hrčka M.

Reports on Geodesy

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2004

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tom nr 2/69

115--123

EN

Reference for geodynamical projects in Central Europe based on permanent GPS observations in the region. Experiences from one-year interval of data analysis. Method of processing the permanent GPS data and inclusion of epoch campaigns.

5

Late Miocene fluvial distributary system in the northern Danube Basin (Pannonian Basin System): depositional processes, stratigraphic architecture and controlling factors of the Piešťany Member (Volkovce Formation)

75%

Šujan M. , Kováč M. , Hók J. , Šujan M. , Braucher R. , Rybár S. , Leeuw A. d.

Geological Quarterly

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2017

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tom Vol. 61, No. 3

521--548

EN

Aim of the study was to investigate the detailed stratigraphic architecture of the alluvial Volkovce Formation, which was deposited in the northern Danube Basin during the interval between 10 and 6 Ma. Two type locality exposures were subject to facies analysis and interpretation of depositional processes and >500 boreholes served for correlation of spatial variability in the character of the formation. The study was focused on the northern Blatné and western Rišňovce depressions, which are partly separated by the Považský Inovec Mountains horst. It was revealed, that a mostly gravelly fluvial distributary system of the Piešťany Member was deposited in the northern Blatné depression, partly confined by the exposed horst and by incised palaeotopography. The sequence is composed of amalgamated braided river channel bodies with no overbank strata, in response to high sediment supply and low accommodation. The palaeo-stream then crossed the horst in its southern part towards the Rišňovce depression, where there was four times more accommodation. The submerged horst acted as a boundary, where the depositional processes changed to a meandering river and significant overbank deposits started to be preserved. Only small streams were present in the northern Rišňovce depression, which led to very low sediment supply compared to the high accommodation there. The depositional system was affected mainly by the incised palaeotopography, by the location of sediment input together with spatial differences in accommodation rate caused by the activity of the Ripňany Fault on the southeastern side of the Považský Inovec Mts.

6

Pliocene to Quaternary stress field change in the western part of the Cen tral West ern Carpathians (Slovakia)

75%

Vojtko R. , Hók J. , Kováč M. , Sliva L. , Joniak P. , Šujan M.

Geological Quarterly

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2008

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tom Vol. 52, No 1

19-19

EN

Knowledge of the current tectonic regime plays an essential role in natural hazard assessment, especially in the risk assessment of fault activity. Structural analysis of brittle deformations (using in version techniques) was used to determine the stress field state occurring within Pliocene and Quaternary deposits in the western part of the Central Western Carpathians. The deformation pattern of the reduced stress tensor showed that all structural measurements could be separated into two groups. An older, Late Pliocene fault population was activated un der NNW-SSE oriented extension. A younger, Quaternary fault population reflected origin in a NE–SW extensional tectonic regime and it distinctly showed a change the orientation of the S3 of about 70. The change in tectonic activity, as well as in the stress field orientation, is dated to the Pliocene-Pleis to cene boundary. The Quaternary stress field developed dur ing the post-collisional stage of the orogen. Our study shows that the West ern Carpathian internal units document NE-SW to NNE-SSW extension in the broader region around of the north ern Danube Basin.

7

Study of Solidification of Continuously Cast Steel Round Billets Using Numerical Modelling

63%

Merder T. , Pieprzyca J. , Tkadlečková M. , Michalek K. , Socha L. , Saternus M. , Válek L. , Kováč M.

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nr 1

8

Study of Solidification of Continuously Cast Steel Round Billets Using Numerical Modellin

63%

Tkadleckova M. , Válek L. , Socha L. , Saternus M. , Pieprzyca J. , Merder T. , Michalek K. , Kováč M.

Archives of Metallurgy and Materials

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2016

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tom Vol. 61, iss. 1

221--226

EN

The paper is dedicated to the verification of solidification of continuously cast round steel billets using numerical modelling based on the finite element method. The aim of numerical modelling is to optimize the production of continuously cast steel billets of round format. The paper describes the pre-processing, processing and post-processing phases of numerical modelling. Also, the problems with determination of the thermodynamic properties of materials and the heat transfer between the individual parts of the casting system, including the definition of the heat losses along the casting strand in the primary and secondary cooling, were discussed. The first results of numerical simulation show the so-called thermal steady state of continuous casting. The temperature field, the metallurgical length and the thickness of the shell at the end of the mould were predicted. The further research will be concentrated on the prediction the risk of the cracks and the porosity based on the different boundary conditions.