Celem niniejszej pracy jest opracowanie modelu numerycznego procesu hartowania wyrobów ze stali z uwzględnieniem wpływu przemian fazowych z wykorzystaniem komercyjnego oprogramowania numerycznego ANSYS. W artykule zaproponowano model numeryczny swobodnego chłodzenia pierścieni stalowych z uwzględnieniem zaimplementowanego modelu przemiany bainitycznej oraz martenzytycznej. Kluczowa w proponowanym rozwiązaniu jest możliwość rozpatrywania niejednorodności w polu temperatury wynikająca z różnych prędkości chłodzenia na przekroju poprzecznym pierścienia, co w rezultacie wpływa na dokładność przewidywania naprężeń szczątkowych. Weryfikacja opracowanego modelu z wykorzystaniem wyników badań laboratoryjnych potwierdza jego duże możliwości określania zmian zachodzących podczas procesu chłodzenia pierścieni.
EN
The main goal of the paper is development of the numerical model for cooling simulations of steel products taking into account phase transformations. The phase transformation model was incorporated via the user subroutines to the commercial finite element software. The cooling process of steel rings used in the aircraft industry was selected as a case study. Particular attention was put on heterogeneities occurring in temperature field, which will influence phase transformations and eventually residual stresses. Developed model was validated with experimental results and its good predictive capabilities have been proved.
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The proposed energy diagrams reveal a clear link between development of the spatial design and energy management in buildings. This relationship has an impact on the energy efficiency and microclimate of a given building. The mentioned relationship highlights an importance of incorporating the energy diagrams at the first step of the building design process since they have a very practical value. Showing a graphic representation of the heating and cooling processes can be an advantageous tool in energy efficiency analysis and finally the basis for adopting the optimum spatial as well as the construction and material solutions.
PL
Między kształtowaniem przestrzennym a gospodarowaniem energią w budynku istnieje wyraźny związek, który przekłada się na sprawność energetyczną i mikroklimat wnętrza budynku. Zależność ta uzasadnia potrzebę stosowania schematów energetycznych już na wstępnym etapie projektowania obiektu. Mają one wartość praktyczną. Przedstawiając w graficzny sposób procesy zachodzące w ramach strategii ogrzewania i chłodzenia, mogą być one pomocnym narzędziem analiz efektywności energetycznej i, w końcowym rozrachunku, podstawą przyjęcia optymalnych rozwiązań przestrzennych i konstrukcyjno-materiałowych.
The article deals with the effect on the quality of casting moulds (metal, bentonite mixture) on the structure of the alloy AlZn5,5MgCu and selected mechanical properties of the alloy. The effect of foundry moulds can significantly affect formation and range of crystal segregation and the subsequent thermal process of homogenization which has an influence on the final quality of the alloy. The research focuses on the formation and range of crystal segregation and its removal with homogenization annealing, in which the observed influence of individual factors influencing the diffusion process and quality of the aluminium alloy.
W pracy zastosowano sztuczne sieci neuronowe do określania wymaganej wartości współczynnika przejmowania ciepła od odlewu staliwnego. Wielowarstwowa sztuczna sieć neuronowa wyznacza wartości współczynnika przejmowania, tak aby uzyskać odpowiednie ułamki faz w wewnętrznych węzłach kontrolnych odlewu. Wartości tego współczynnika wyznaczane są dla kontrolnych węzłów brzegowych i są aproksymowane na pozostałe elementy brzegowe. Dane uczące oraz testowe uzyskano z rozwiązania równania przewodzenia ciepła z wykorzystaniem metody elementów skończonych (zadania 2D). Ułamki faz wyznaczono z zastosowaniem makroskopowego modelu przemian fazowych w stanie stałym (analiza wykresów CTP).Przedstawiono błędy opracowanej metody oraz jej skuteczność w automatyzacji projektowania procesu chłodzenia.
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n the paper the artificial neural network to determine value of heat transfer coefficient (α∞) for the steel casting has been used. On the basis of phase fraction in the control nodes which were located in the area of casting the required values of heat transfer coefficient have been determined by the multilayer artificial neural network. The values of α∞coefficient are set down for the boundary control nodes and approximated on the other elements. On the basis of numerical solution of the thermal conductivity equation with finite element method the learning and testing data have been obtained (2D tasks). The macroscopic model of phase transformations in the solid state (analysis of CCT diagrams) has been used to calculate the phase fractions. In this paper the errors of implemented method and the effectiveness of this method in automatization of the optimization for the cooling process are presented.
The user friendly computer system that have the capability of modelling material behaviour both at the macro and micro scales was developed in this work. The system was designed to predict microstructure evolution during phase transformation in laminar cooling conditions with the use of the multi scale cellular automata finite element (CAFE) model. The finite element (FE) part is based on the conventional Fourier type equation and is used to predict macroscopic temperature distribution. This is an input for the micro scale cellular automata (CA) model of austenite-ferrite phase transformation. To facilitate the research, proposed micro scale CA model was implemented within developed universal object-oriented programming framework CAF. Description of major assumptions and functionality of the developed numerical system including efficient Graphical User Interface (GUI) is presented in the paper. The intuitive visualization of data obtained in different length scales facilitates work with the software.
In the paper, the description of an unsteady heat transfer for a two-dimensional problem is presented. It is assumed that all the thermophysical parameters appearing in the mathematical model of the problem analyzed are given as fuzzy numbers. The problem discussed has been solved by means of the 1st scheme of the fuzzy boundary element method using α-cuts. The application of α-cuts allows one to avoid complicated arithmetical operations in the fuzzy numbers set. The interval Gauss elimination method with the decomposition procedure has been applied to solve the obtained fuzzy system of equations. In the final part of the paper, the results of numerical computations are shown.
In this paper a mathematical model of cooling process for steel castings is presented. Effect of convective motion of the coolant on material structure after cooling process is investigated. Mathematical and numerical model based on Generalized Difference Method for axysimmertric elements is used. To solve the Navier-Stokes equation the characteristic based split scheme (CBS) has been applied. The solution of the heat transport equation with the convective term has been obtained by a stabilized meshless method. To determine of the phase transformation the macroscopic model built on the basis of Time Temperature Transformation diagrams for continuous cooling of medium-carbon steel has been used. The temporary temperature fields, the phase transformation, thermal and structural strains for the cooled element and the fields of temperature and velocity for the coolant have been determined.
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Modeling of coolant flow is increasingly important in the problems of heat treatment. Variation of the coolant characteristics is not possible to present, as a boundary condition at the appropriate level of detail. This paper presents a solution of the heat transfer equation with a convective term and a Navier-Stokes equation for forced flow, which is characteristic for a hardening process. These equations are solved by means of a meshless method. The emerging models for solving thermal processes in coolants require a stable numerical method. In this paper a stabilization of the numerical models for the generalized finite difference method for both temperature and fluid flow models are proposed. The results obtained with software implementations of the proposed models are compared with the an analytical solution and with the numerical benchmarks.
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One of the most commonly used methods of numerical simulation is the finite element method (FEM). Its popularity is reflected in the number of tools supporting the preparation of simulation models. However, despite its usefulness, FEM is often very troublesome in use; the problem is the selection of the finite element mesh or shape function. In addition, MES assumes a complete knowledge of the simulated process and of the parameters describing the investigated phenomena, including model geometry, boundary conditions, physical parameters, and mathematical model describing these phenomena. A comparison of the data obtained from physical experiments and simulations indicates an inaccuracy, which may result from the incorrectly chosen shape of element or geometry of the grid. The application of computational intelligence methods, combined with knowledge of the manufacturing technology of metal products, should allow an efficient selection of parameters of the mathematical models and, as a consequence, more precise control of the process of the casting solidification and cooling to ensure the required quality. The designed system has been integrated with the existing simulation environment, which will significantly facilitate the preparation and implementation of calculations of this type. Moreover, the use of a distributed model will significantly reduce the time complexity of calculations, requiring multiple repetition of complex simulations to estimate the quality of the different sets of parameters.
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Classical finite difference method (FDM) is typically used for solving Navier-Stokes (N-S) equation. However to obtain a solution on irregular grid of points other methods have to be applied. Generalized finite difference method (GDFM) is one of the methods that my be used to solve mentioned problem. In this paper N-S and heat transfer equation have been solved using the GFDM. Results of numerical solutions for cooling processes with convection move in two-dimensional region are presented.
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ADI (Austempered Ductile Iron) cast iron, owing to its unique combination of high tensile strength and abrasion resistance with very good plasticity, founds implementation in many branches of industry as a substitute of alloy cast steel and carburized or heat treated steels. In spite of its solid position among producers and recipients of castings, there are still undertaken studies aimed at perfection of its properties and recognition of mechanisms enabling obtaining such properties. The paper presents implementation of thermal-voltage-derivative (ATND) method to registration of heating and cooling course of ADI cast iron with EN-GJS-1200-2 grade. ADI cast iron with EN-GJS-1200-2 grade underwent the study. Heat treatment of the cast iron was performed in Foundry Institute with use of LT ADI-350/1000 processing line. Results obtained from the testing illustrate in graphic form registered heating and cooling curves of investigated cast irons obtained with use of the ATND method.
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Przeprowadzono obliczenia równowagowego składu wtrąceń MnO-SiO2, dla stopu Fe-36Ni w porównaniu ze stalą bez niklu, w przypadku oziębiania metalu o zróżnicowanej zawartości manganu w obszarze kadzi. Obliczenia wykonano w zakresie od 1873 do 1773 K. Założono wariant bez mieszania oraz z częściowym mieszaniem. Zmiany składu wtrąceń okazały się w dużym stopniu zależne od zawartości niklu oraz zróżnicowania stężenia manganu.
EN
Computations of equilibrium compositions for MnO-SiO2., inclusions formed in Fe-36Ni alloy were performed. The data were compared to the ones of nickel-less steel in case of cooling the alloys with different Mn contents within the ladle compartment. The computations were carried out for the temperatures from 1873 to 1773 K. Two variants were considered: with no mixing and with partial mixing. It was found that changes in compositions of inclusions were to a large extent dependent on niekel content and non-uniformity of Mn content in steel.
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W referacie zaprezentowano autorski program komputerowy KOMORA wspomagający działania w zakresie projektowania małych i średnich komór chłodniczych. Szczególną uwagę zwrócono na możliwość symulowania na etapie projektu specyficznych sytuacji eksploatacyjnych dotyczących: - przenikania wilgoci przez przegrody budowlane, - zmiany mikroklimatu wewnątrz obiektu chłodniczego, - dynamiki procesu schładzania. Opis algorytmów symulacyjnych uzupełniono przykładami obliczeniowymi.
EN
In the report was presented author is computer program KOMORA which aids designing little and average cooling rooms. The main stress is on possibility of simulation during specify exploitation situations relatives to: - infiltration of humidity threw building barriers, - changes of microclimate in cooling object, - dynamic of cooling process. The description of algorithms was completed with computable examples.
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W referacie omówiono podstawy bilansu ciepła i wilgoci sporządzonego dla procesu chłodzenia masy obiegowej w złożu wibrofluidalnym. Na podstawie bilansu przeprowadzono ocenę efektów chłodzenia z uwzględnieniem wpływu parametrów urządzeń. Omówiono warunki realizacji przepływu wibrofluidyzacyjnego w chłodziarkach.
EN
In the paper the basis of heat and moisture balance for moulding sand cooling process in vibro-fluidised bed has been presented. The balance was started point for cooling results evaluation with concerning cooling device parameters. The moulding sand flow conditions in vibro-fluidised bed have been also described.
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This paper presents an analysis of the cooling process of a solid, induced by the impingement of an air jet. Solutions of the inverse heat conduction problem were obtained by applying the heat functions to formulate the base functions of the Finite Element Method. The applied heat functions identically satisfy the heat conduction equation in dimensionless co-ordinates. The minimisation of the functional, presented in this paper, leads to the solutions of the analysed problem. The temperature distribution of the analysed solid was determined by solving the inverse heat conduction problem by means of the temperature measurements taken inside the solid. Properties of the heat function were applied to reconstruct the distribution of the Bi number on the heat exchange surface; this in turn enables to determine the heat transfer coefficient on the analysed surface. The results of the analysis were compared with the data found in the literature.
In the paper the example of numerical simulation of heat transfer proceeding during the cooling process in domain of infinite plate is presented. The model is constructed on the basis of generalized finite differences method - GFDM [1 , 2]. On the outer surfaces of the plate the Robin conditions are assumed, at the same time the heat transfer coefficient is the sum of radial and convective components.
In the paper the numerical model of heat transfer proceeding during the heating and cooling processes in domain of solid is presented. The model is constructed on the basis of generalized finite differences method - GFDM [1 , 2]. In order to simplify the considerations, a 1D task is discussed (the infinite plate). More complex (from the geometrical point of view) problems are in details described in [2].
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In the paper the quantitative description of phase changes in flat wall of the casting is presented. TTTc -diagram for steel with chemical composition equivalent for cast steel 50L has been selected. Cooling rate of casting has been obtained by surface film conductance [....] depending on kind of cooling medium. Dilatometric curves, phase change diagrams and distribution of hardness for examples of cooling in casting mould and water have been show.
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W pracy przedstawiono możliwość wykorzystania tzw. kombinowanej metody elementów brzegowych do obliczeń procesu stygnięcia odlewu o geometrii walcowej. Wykorzystano algorytm dla zadania płaskiego i równania energii ze składnikiem źródłowym. Rozważano procesy bez przemian fazowych (np. obróbka cieplna). Uzupełnienie prezentowanego algorytmu dodatkowymi procedurami uwzględniającymi proces krzepnięcia pozwala również na jego wykorzystanie do analizy bardziej złożonych procesów cieplnych.
EN
The problem of application of the BEM using discretization in time in numerical computations of cooling processes proceeding in domain of cylindrical casting is discussed. The energy equation for 2D problem with additional component called the artificial source function is considered. In the paper only the cooling processes (e.g. the heat treatment) are analyzad, but the supplement of algorithm proposed by the procedures simulating the solidification process allows to solve more complex problems, too.
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