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1
Content available Estimation of Cast Iron Substitute Thermal Capacity Using the Experimental Data
Majchrzak E., Mendakiewicz J., Mochnacki B.
Archives of Metallurgy and Materials
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2016
|
Vol. 61, iss. 1
307--314
EN
In the paper the problem of the cast iron substitute thermal capacity estimation is discussed. This parameter appears when the macroscopic mathematical model of alloys solidification bases on the one domain method (fixed domain approach). In the case of cast iron the form of function describing the course of temperature-dependent thermal capacity is quite complex. Using the experimental data, in particular the measured cooling, heating curves at the set of points selected in the casting – mould domain the identification problem has been solved using the gradient methods. The results presented concern the gray iron 3.21% C and 1.9% Si.
2
Content available Numerical Model Of Binary Alloys Solidification Basing On The One Domain Approach And The Simple Macrosegregation Models
Majchrzak E., Mochnacki B., Mendakiewicz J.
Archives of Metallurgy and Materials
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2015
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Vol. 60, iss. 3
2431--2435
EN
In the paper the thermal processes proceeding in the domain of solidifying binary alloy are considered. The mathematical model of solidification and cooling processes bases on the one domain method (or fixed domain method). In such a model the parameter called a substitute thermal capacity (STC) appears. At the stage of STC construction the macrosegregation process described by the lever arm rule or the Scheil model is taken into account. In this way one obtains the formulas determining the course of STC resulting from the certain physical considerations and this approach seems to be closer to the real course of thermal processes proceeding in domain of solidifying alloy. In the final part the examples of numerical solutions basing on the finite difference method are presented.
PL
W pracy rozpatruje się procesy cieplne zachodzące w obszarze krzepnącego i stygnącego stopu dwuskładnikowego. Model matematyczny tych procesów bazuje na podejściu nazywanym metodą jednego obszaru. W modelach tego typu pojawia się parametr nazywany zastępczą pojemnością cieplną. Na etapie jej definiowania autorzy uwzględnili proste modele makrosegregacji wynikające z reguły dźwigni i znanego modelu Scheila. Otrzymane zależności determinujące przebiegi pojemności zastępczej na podstawie pewnych rozważań fizycznych wydają się lepiej przybliżać rzeczywisty przebieg procesów cieplnych zachodzących w obszarze krzepnącego stopu. W końcowej części pracy pokazano wyniki rozwiązań numerycznych uzyskanych przy wykorzystaniu metody różnic skończonych.
3
Content available remote Influence of the shielding gas on the properties of VP MIG/MAG braze-welded joints in zinc coated steel sheets
Pikuła J, Pfeifer T, Mendakiewicz J.
Biuletyn Instytutu Spawalnictwa w Gliwicach
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2014
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Vol. 58, No. 1
35--41
EN
The article presents the results of research on overlay brazing and weldbrazing of hot-dip galvanized sheets carried out in order to determine the influence of shielding gas composition and electrode-negative (EN) ratio on the process and properties of overlay brazes and weldbrazed joints. The parameters analysed included joint geometry, wettability, zinc coating oxidation, spatter and porosity.
PL
Przedstawiono wyniki badań procesu lutonapawania i lutospawania blach ocynkowanych przeprowadzonych w celu określenia wpływu gazu osłonowego i udziału składowej ujemnej prądu o zmiennej biegunowości na przebieg procesu oraz własności lutonapoin i połączeń lutospawanych. Analizowane były: geometria złączy, zwilżalność, uszkodzenie powłoki cynkowej, rozprysk i porowatość.
4
Określenie zastępczej pojemności cieplnej żeliwa na podstawie badań doświadczalnych
Mendakiewicz J.
Zeszyty Naukowe. Mechanika / Politechnika Opolska
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2010
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z. 97
63-64
PL
Symulacja numeryczna krzepnięcia i stygnięcia stopów metali wymaga znajomości zastępczej pojemności cieplnej. Funkcję tą wyznaczono na podstawie przeprowadzonych badań eksperymentalnych.
5
Content available remote Experimental and numerical determination of temperature distibution in solidifying casting
Mendakiewicz J.
Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej
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2010
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Vol. 9, nr 2
193-196
EN
The thermal processes proceeding in a system casting-mould are considered. The casting is made from cast iron. The temperature and its time derivative at the central point of sample casting have been obtained experimentally. Using finite difference method the temperature distribution in the domain considered has been determined. Next, the calculated and measured cooling curves have been compared. The good agreement between these curves has been observed.
6
Content available remote Identification of solidification process parameters
Mendakiewicz J.
Computer Assisted Mechanics and Engineering Sciences
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2010
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Vol. 17, no. 1
59-73
EN
In the paper, the identification problems connected with estimation of cast iron and mould thermophysical parameters are discussed. The additional information necessary to solve the problem results from the knowledge of cooling (heating) curves at the set of points from casting (mould) domain. The course of cooling (heating) curves results from the temperature measurements done in the real conditions of technological process, but at the present stage of research the numerical solution of direct problem plays the role of measured temperatures. In this place the problem of optimal sensors position in a system castingmould appears. Both the choice of measuring points and also the solution of inverse problem, using the gradient methods, require the application of sensitivity analysis methods. The theoretical considerations are illustrated by the examples of computations. The numerical algorithms presented base on the finite difference method (2D problems are considered).
7
Content available remote Optimum location of sensors used for mould parameters estimation
Majchrzak E., Mendakiewicz J.
Archives of Foundry Engineering
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2010
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Vol. 10, iss. 1
97-100
EN
Heat transfer processes proceeding in the system casting-mould-environment are considered. In particular, the inverse problem connected with the estimation of thermal conductivity and volumetric specific heat of mould material is presented. To estimate the parameters, the additional information concerning the temperature history at the points selected from domain considered is necessary. The essential problem is a proper choice of sensors localization. The application of sensitivity analysis assures the increase of identification efficiency and this problem is here presented. In the final part of the paper the examples of computations are shown.
8
Content available remote Algorithms of optimum location of sensors for solidification parameters estimation
Mendakiewicz J.
Archives of Foundry Engineering
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2010
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Vol. 10, iss. 4
141--146
EN
The algorithms of optimal sensor location for estimation of solidification parameters are discussed. These algorithms base on the Fisher Information Matrix and A-optimality or D-optimality criterion. Numerical examples of planning algorithms are presented and next for optimal position of sensors the inverse problems connected with the identification of unknown parameters are solved. The examples presented concern the simultaneous estimation of mould thermophysical parameters (volumetric specific heat and thermal conductivity) and also the components of volumetric latent heat of cast iron.
9
Location of sensors assuring the optimal solution of identification problems
Mendakiewicz J.
Zeszyty Naukowe. Mechanika / Politechnika Opolska
|
2009
|
z. 95
85-86
10
Content available remote Optimal location of sensors for estimation of cast iron latent heat
Majchrzak E., Mendakiewicz J.
Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej
|
2009
|
Vol. 8, nr 1
123-130
EN
The thermal processes proceeding in a system casting-mould are considered. The casting is made from cast iron and the austenite and eutectic latent heats should be identified. To estimate these parameters the knowledge of temperature history at the points selected from the domain considered is necessary. The location of sensors should assure the best conditions of identification process. In the paper the method of optimum location of sensors basing on the D-optimality criterion is presented.
11
Content available remote Identification of cast steel latent heat on a basis of thermal and differential analysis
Majchrzak E., Mendakiewicz J.
Computer Methods in Materials Science
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2009
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Vol. 9, No. 2
195-199
EN
Thermal and differential analysis (TDA) constitutes a very popular and effective tool of quantitative estimation of solidification process parameters, such as border temperatures, evolution of latent heat etc. TDA registering system is connected to the thermocouple located at a central point of sampling casting. Using the adequate program of automatic data processing one obtains the information concerning the cooling curve and its time derivative at the point corresponding to sensor position. In the paper the solution of inverse problem consisting in the identification of cast steel latent heat is discussed. The additional information neccessary to solve the problem results both from a knowledge of cooling curve T(t) and its time derivative T'(t). The criterion determining the optimum value of latent heat bases on the input data concerning not only T(t) but also T'(t). On a stage of numerical computations the finite difference method has been used. In a final part of the paper the examples of identification process are shown.
PL
Analiza termiczna i różniczkowa (ATD) stanowi bardzo popularne i efektywne narzędzie jakościowej estymacji parametrów procesu krzepnięcia takich jak temperatury graniczne, utajonego ciepło krzepnięcia itp. System rejestrujący ATD połączony jest z termoparą umieszczoną w centralnej części odlewu próbnego. Wykorzystując odpowiedni program komputerowy automatycznego przetwarzania danych otrzymuje się informacje dotyczące krzywej stygnięcia i jej pochodnej względem czasu (szybkości krzepnięcia) w punkcie odpowiadającym położeniu sensora. W artykule przedstawiono tzw. problem odwrotny polegający na identyfikacji utajonego ciepła krzepnięcia. Dodatkową informacją niezbędną do rozwiązania tego typu zadania była znajomość przebiegu zarówno krzywej stygnięcia T(t) jak i jej pochodnej T (t). Na etapie obliczeń numerycznych zastosowano metodę różnic skończonych. W końcowej części pracy przedstawiono wyniki identyfikacji.
12
Sensitivity analysis as an accessary tool in experiments design
Mendakiewicz J.
Zeszyty Naukowe. Mechanika / Politechnika Opolska
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2008
|
z. 92
33-34
EN
The system casting-mould is considered and it is assumed that the aim of experiments is to determine the latent heat of casting material. To find the optimal location of sensors the sensitivity analysis methods are applied.
13
Content available remote Application of sensitivity analysis in experiments design
Mendakiewicz J.
Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej
|
2008
|
Vol. 7, nr 1
141-148
EN
The system casting-mould is considered and it is assumed that the aim of experiments is to determine the course of substitute thermal capacity of casting material. The casting is made from cast iron and the austenite and eutectic latent heats should be identified. To find the optimal location of sensors the methods of sensitivity analysis are applied. In the final part of the paper the results of computations are shown.
14
Content available remote Application of identification methods in solidification process modelling
Mendakiewicz J.
Archives of Foundry Engineering
|
2008
|
Vol. 8, iss. 1 spec.
203-210
EN
In the paper the identification problems connected with the estimation of cast iron and mould thermophysical parameters are discussed. The additional information necessary to solve the problem results from a knowledge of cooling (heating) curves at the set of points from casting (mould) domain. The course of cooling (heating) curves results from the temperature measurements done in the real conditions of technological process, but on the present stage of research the numerical solution of direct problem plays a role of measured temperatures. The identification algorithm basing on the gradient methods is used to estimate the parameters of casting-mould system (a case of simultaneous estimation of bigger number of parameters is also considered). On the stage of numerical realization the FDM is used (2D task). In the final part of the paper the examples of computations are shown.
PL
W pracy przedstawiono problemy identyfikacji związane z estymacją parametrów odlewu żeliwnego i masy formierskiej. Dodatkową informacją niezbędną do rozwiązywania tego typu zadań jest znajomość krzywych stygnięcia (nagrzewania) w zbiorze punktów odlewu/formy. Krzywe stygnięcia (nagrzewania) można otrzymać na podstawie pomiarów wykonanych w rzeczywistych warunkach przebiegu procesu. Na obecnym etapie badań krzywe te uzyskiwano poprzez rozwiązanie zadania bezpośredniego dla zadanych wartości parametrów procesu. Algorytmy identyfikacji bazujące na metodach gradientowych zastosowano do estymacji parametrów występujących w układzie odlew-forma. W końcowej części artykułu pokazano przykłady obliczeń.
15
Content available remote Application of experimental data for numerical simulation of cast iron solidification
Mendakiewicz J.
Archives of Foundry Engineering
|
2008
|
Vol. 8, iss. 4
111-114
EN
Numerical analysis of cast iron solidification process is presented. The system casting - shell mould is discussed. The parameter controlling the solidification process called a substitute thermal capacity (STC) has been constructed in this way in order to take into account the evolution of latent heats connected with the solidification of austenite and eutectic phases. The information concerning the proper approximation of STC results from the experimental data using the thermal and derivative analysis (TDA).
16
Content available remote Application of evolutionary algorithm for cast iron latent heat identification
Mendakiewicz J., Paruch M.
Archives of Foundry Engineering
|
2008
|
Vol. 8, iss. 4
115-120
EN
In the paper the cast iron latent heat in the form of two components corresponding to the solidification of austenite and eutectic phases is assumed. The aim of investigations is to estimate the values of austenite and eutectic latent heats on the basis of cooling curve at the central point of the casting domain. This cooling curve has been obtained both on the basis of direct problem solution as well as from the experiment. To solve such inverse problem the evolutionary algorithm (EA) has been applied. The numerical computations have been done using the finite element method by means of commercial software MSC MARC/MENTAT. In the final part of the paper the examples of identification are shown.
17
Identification of temperature dependent thermal conductivity of alloy using Gradient Method
Majchrzak E., Mendakiewicz J., Freus K.
Zeszyty Naukowe. Mechanika / Politechnika Opolska
|
2007
|
Vol. 321, z. 89
57-58
EN
The temperature dependent thermal conductivity of metal is identified. To solve the problem the gradient method is used. On the stage of numerical computations boundary element method is applied, at the same time in order to simplify the algorithm the Kirchhoff transformation is introduced. The example of computations is also shown.
18
Content available remote Estimation of boundary heat flux during cast iron solidification
Mendakiewicz J.
Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej
|
2007
|
Vol. 6, nr 1
191-198
EN
In the paper the inverse problem consisting in estimation of boundary heat flux during cast iron solidification is presented. In order to solve the inverse problem formulated it is assumed that the cooling curves at selected set of points from the casting domain are given. The algorithm bases on the gradient method coupled with the finite differences method. In the final part of the paper the results of computations are shown.
19
Content available remote Application of evolutionary algorithms in identification of solidification parameters
Majchrzak E., Mendakiewicz J., Paruch M.
Journal of Achievements in Materials and Manufacturing Engineering
|
2007
|
Vol. 23, nr 2
67-70
EN
Purpose: The casting-mould system is considered. Additionally, it is assumed that part of internal parameters determining the course of thermal processes, e.g. volumetric specific heat of mould, mould thermal conductivity, casting thermal conductivity and the like is unknown. Formulated in this way an inverse problem can be solved using different methods and in this paper the possibility of evolutionary algorithms application is presented. To solve the problem knowledge of cooling/heating curves at selected set of points from casting/mould domain is necessary. The evolutionary algorithm allows to minimize the fitness function containing the differences between the 'measured' cooling curves and the same curves found on the basis of boundary initial problem numerical solution for the assumed set of parameters. The calculated cooling/heating curves have been found using explicit scheme of finite difference method. It turned out that the algorithm proposed gives sufficiently exact results of identification and it can be successfully applied in the scope of thermal theory of foundry process. Design/methodology/approach: In this work numerical modelling of solidification process is applied. A cast iron solidifying in a sand mould is analyzed. The information concerning the courses of cooling/heating curves at the selected set of points from the domain considered is used in order to identify the unknown parameters of the process analyzed. Findings: Application of evolutionary algorithms gives sufficiently exact results of identification of solidification parameters. Research limitations/implications: Further work requires an introducing of real temperature measurements to the model presented. Practical implications: The paper shows the possibilities of solidification parameters identification on the basis of temperature measurements. Originality/value: The evolutionary algorithms presented allow to identify the parameters of solidification process e.g. volumetric specific heat of mould, mould thermal conductivity, casting thermal conductivity and the like.
20
Content available remote Gradient method of cast iron latent heat identification
Majchrzak E., Mendakiewicz J.
Archives of Foundry Engineering
|
2007
|
Vol. 7, iss. 4
121-126
EN
In the paper the cast iron latent heat in the form of three components corresponding to solidification of austenite and eutectic phases is identified. The basic information concerning the form of adequate functions approximation has been taken on the basis of cooling curve and temperature derivative courses found by means of the TDA technique. On the stage of inverse problem solution the gradient method has been used. The numerical computations have been done using the finite difference method. In the final part of the paper the example of latent heat identification is shown.
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