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1

An Orientation-space Super Sampling Technique for Six-dimensional Diffraction Contrast Tomography

Viganò N., Batenburg K. J., Ludwig W.

Fundamenta Informaticae

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2016

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Vol. 146, nr 2

219--230

EN

Diffraction contrast tomography (DCT) is an X-ray full-field imaging technique that allows for the non-destructive three-dimensional investigation of polycrystalline materials and the determination of the physical and morphological properties of their crystallographic domains, called grains. This task is considered more and more challenging with the increasing intra-granular deformation, also known as orientation-spread. The recent introduction of a sixdimensional reconstruction framework in DCT (6D-DCT) has proven to be able to address the intra-granular crystal orientation for moderately deformed materials. The approach used in 6D-DCT, which is an extended sampling of the six-dimensional combined position-orientation space, has a linear scaling between the number of sampled orientations, which determine the orientation-space resolution of the problem, and computer memory usage. As a result, the reconstruction of more deformed materials is limited by their high resource requirements from a memory and computational point of view, which can easily become too demanding for the currently available computer technologies. In this article we propose a super-sampling method for the orientation-space representation of the six-dimensional DCT framework that enables the reconstruction of more deformed cases by reducing the impact on system memory, at the expense of longer reconstruction times. The use of super-sampling can further improve the quality and accuracy of the reconstructions, especially in cases where memory restrictions force us to adapt to inadequate (undersampled) orientation-space sampling.

2

Molecular models of polycrystalline and porous materials

Mrozek A.

Computer Methods in Materials Science

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2014

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Vol. 14, No. 1

27--36

EN

This paper is contribution to the special issue of the CMMS journal, devoted to modelling of the polycrystalline structures. Creation of the metallic polycrystalline and porous structures based on the molecular dynamics (MD) simulations are presented in this paper. The simple Morse potential, as well as, the more sophisticated Embedded Atom Method (EAM) are engaged to model atomic interactions. The presented methods of creation of the polycrystalline and porous molecular models are discussed and illustrated with proper numerical examples. The series of tensile tests and comparison of the mechanical properties between obtained polycrystalline structures is included, along with the description of the algorithm of the computation of the mechanical properties and the stress-strain relations. Additional tests are carried out with ideal Morse and EAM monocrystals in order to validate our molecular models and results. The simulations of creation polycrystalline and porous models are performed using the massively-parallel MD solver with NVT ensemble and tensile tests utilize so-called Non-Equilibrium Molecular Dynamics (NEMD).

PL

Tematyka pracy dotyczy metod tworzenia oraz badania własności mechanicznych atomowych modeli materiałów polikrystalicznych oraz porowatych przy wykorzystaniu Dynamiki Molekularnej. Przedstawionych zostało kilka różnych technik otrzymywania w/w struktur, m. in. kontrolowane schładzanie układu atomów oraz modyfikacja zasięgu oddziaływań międzyatomowych (funkcji potencjału atomowego). Każda metoda zilustrowana została przykładami, omówiony został również wpływ wybranych parametrów na wyniki symulacji numerycznej. W dalszej części artykułu opisano sposób wyznaczania własności mechanicznych modeli molekularnych: wyznaczania składowych tensora mikronaprężenia, krzywych naprężenie-odkształcenie i modułu Younga. Utworzone przedstawionymi metodami, zrównoważone i stabilne modele atomowe mogą posłużyć jako materiał wejściowy - rozwiązania początkowe - do dalszych symulacji wykorzystujących dynamikę lub statykę molekularną.

3

Geometryczny opis polikryształów w IMIM PAN

Morawiec A.

LAB Laboratoria, Aparatura, Badania

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2013

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R. 18, nr 6

12--15

4

Modeling structures of cellular materials for application at various length - scales

Wejrzanowski T., Skibiński J., Madej Ł., Kurzydłowski K. J.

Computer Methods in Materials Science

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2013

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Vol. 13, No. 4

493--500

EN

The paper presents the spectrum of methods and results for design of structures, which are frequently applied in numerical simulations of properties and processes taking place in cellular materials. The methods described here are universal for many applications at various length-scales. They can be efficiently applied for complex cellular structures such as polycrystals or foams, where the elements (grains or pores) are distributed and shaped in a controlled way. The digital material representations created by these methods can be used for a number of numerical techniques such as: Molecular dynamics (MD), Monte Carlo (MC), Cellular Automaton (CA), Finite Element Method (FEM) or Finite Volume Method (FVM). The examples of structures consisting of atoms, fields or finite elements are presented in this paper. The applications of such structures are demonstrated by the properties and processes relevant to the specific length scales.

PL

W artykule przedstawiono metody oraz wyniki projektowania struktur, które są stosowane do numerycznej symulacji własności i procesów występujących w materiałach komórkowych. Zaprezentowane metody mają charakter uniwersalny dla zastosowań w różnych skalach wymiarowych. Mogą być stosowane do takich materiałów jak polikryształy lub pianki, w których elementy (ziarna lub pustki) są rozłożone i ukształtowane w sposób kontrolowany. Cyfrowe reprezentacje materiału utworzone za pomocą zaproponowanych w pracy rozwiązań mogą stanowić podstawę dla takich numerycznych metod jak Dynamika Molekularna (ang. Molecular Dynamics - MD), Monte Carlo (MC), Automaty Komórkowe (ang. Cellular Automaton -CA), Metoda elementów Skończonych (ang. Finite Element Method - FEM) lub Metoda Objętości Skończonych (ang. Finite Volume Method - FVM). W artykule zaprezentowano przykłady struktur składających się z atomów, pól lub elementów skończonych. Przedstawiono również zastosowania tych struktur do opisu własności i procesów charakterystycznych dla różnych skal wymiarowych.

5

Study of the relaxor behaviour in Ba0.68Na0.32Ti0.68Nb0.32O3 ceramic

Bąk W.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 37, nr 1

24-27

EN

Purpose: The purpose of this work was to synthesize a new ceramic solid solution Ba0.68Na0.32Ti0.68Nb0.32O3 (BNTN32), as well as to measure and analyse its dielectric properties within the temperature range 123 K-473 K, where dielectrically active phase transition was supposed to occur. Design/methodology/approach: The new ceramic composition was prepared by means of conventional method. Dependence of phase transition features on temperature and frequency of measuring field were measured using dielectric spectroscopy method within the frequency range from 20 Hz to 1 MHz. Findings: The electric susceptibility along with temperature decrease generally rises up and has transient dispersion vanishing at about 230 K. At higher and low temperatures, frequency dependence of dispersion differs in character: at temperatures at ~400 K, low frequency values dominate. Dielectric energy losses are very high at ~high temperature, they decline down while temperature decrease, and at about 200 K range its frequency dependence is reversed and less scattered with maximum at ~150 K. The whole transition of ferroelectric - paraelectric (FE - PE) type can be described by means of Curie-Weiss law and it gets diffused character. Research limitations/implications: For modelling purposes the structure parameters of BNTN32 have to be measured by X-ray diffraction in order to establish the dielectric/structural activities of transitions taking place within used the temperature range. Additionally, dielectric measurements within broader frequency range up to 1.8 GHz will be performed. Originality/value: The new type of ceramic material was prepared with interesting dielectric properties. Dispersion reverse of energy losses activated thermally and low frequency memory of barium titanate (BT) transition effect visible at ~400 K is to be a subject of modelling further work.

6

Bounds and self-consistent estimates of overall properties for random polycrystals described by linear constitutive laws

Kowalczyk-Gajewska K.

Archives of Mechanics

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2009

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Vol. 61, nr 6

475-503

EN

Analytical solutions for bounds of overall properties are derived for singlephase polycrystalline materials of random texture, composed of grains with arbitrary anisotropy and described by the linear constitutive law. Self-consistent estimates are found for these materials and they are studied in more details when anisotropic grains are volumetrically isotropic. Reduction of the above solutions for incompressible materials or materials with constraint modes of deformation is also derived. Existence and uniqueness of the obtained solutions are discussed. In order to obtain the solutions, simultaneously the spectral and harmonic decomposition of fourth order Hooke's tensor are used. Utility of the obtained results is demonstrated on the examples of metals and alloys of high specific strength and stiffness.

7

Micromechanical modelling of polycrystalline materials under non-proportional deformation paths

Kowalczyk-Gajewska K., Mróz Z., Pęcherski R. B.

Archives of Metallurgy and Materials

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2007

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Vol. 52, iss. 2

181-192

EN

The rigid-plastic crystal plasticity model with single yield surface of 2n-degree is applied to simulate the polycrystalline behaviour and the crystallographic texture development under non-proportional deformation paths. The role of two controlling parameters: the amplitude and frequency for the processes of tension or compression assisted by cyclic torsion of thin-walled tubes made of copper is analysed. The effect of micro-shear bands on the reduction of global hardening rate is described by means of the contribution function of shear banding in the rate of plastic deformation. The conclusions drawn from the study can find also application in the extension of the analysis for high strength and hard deformable materials.

PL

Przeprowadzono symulacje zachowania się polikryształu oraz rozwoju tekstury krystalograficznej dla nieproporcjonalnych scieżek deformacji wykorzystując sztywno-plastyczny model plastyczności kryształu z powierzchnią plastyczności stopnia 2n. Przeanalizowano wpływ dwóch parametrów kontrolnych: amplitudy i częstości dla procesów rozciągania lub ściskania przy udziale cyklicznego skręcania cienkościennych rurek wykonanych z miedzi. Efekt działania mikropasm ścinania w postaci redukcji globalnego modułu wzmocnienia odkształceniowego został opisany poprzez funkcje udziału pasm ścinania w przyroście deformacji plastycznej. Wnioski wysnute z powyższego studium mogą znaleźć docelowo zastosowanie w rozszerzeniu analizy dla materiałów o podwyższonej wytrzymałości oraz materiałow trudno odkształcalnych.

8

Elasto-plastic models of polycrystalline material deformation and their applications

Wierzbanowski K., Baczmański A., Lipiński P., Lodini A.

Archives of Metallurgy and Materials

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2007

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Vol. 52, iss. 1

77-86

EN

Then elasto-plastic models, used for analysis of polycrystalline material deformation are presented and discussed. Two models are presented in details: the Leffers-Wierzbanowski model and the elasto-plastic self-consistent model, developed by Lipinski, Berveiller and Zaoui. The crystallographic mechanisms of plastic deformation, being the basis of the models, are evoked. The both models have many common elements, they differ, however, in the type of assumed grain-matrix interaction. Some current applications of the decribed models are shown. They are e.g.: prediction of deformation textures, stress-strain curves and distribution of the stored energy as well as the interpretation of residual stress measurement by diffraction technique.

PL

W pracy przedstawiono podstawowe modele typu sprężysto-plastycznego, używane do opisu odkształcenia materiałów polikrystalicznych. Omówiono w szczegółach dwa modele: model Leffersa-Wierzbanowskiego oraz sprężysto-plastyczny model samo-uzgodniony, opracowany przez Lipińskiego, Berveillera i Zaoui. Scharakteryzowano mechanizmy krystalograficzne odkształcenia plastycznego, leżące u podstaw modeli. Oba modele mają wiele wspólnych elementów, róznią się one jednak typem założonego oddziaływania pomiędzy ziarnem i otaczającym go materiałem. Pokazano kilka najczęstszych zastosowań omówionych modeli. Są nimi np.: przewidywanie tekstur odkształcenia, makroskopowych krzywych umocnienia oraz rozkładu energii zgromadzonej w materiale jak również interpretacja dyfrakcyjnych badań naprężeń wewnętrznych.

9

Wpływ wybranych technik wytwarzania na efekt dyspersji fazy metalicznej w nanokompozytach na osnowie tetragonalnych polikryształów tlenku cyrkonu

Kluczkowski R., Śliwa R., Pędzich Z.

Rudy i Metale Nieżelazne

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2004

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R. 49, nr 8

393-397

PL

Przedstawiono wyniki badań mikrostruktury kompozytów wytworzonych na osnowie TZP (tetragonalne polikryształy tlenku cyrkonu) z dodatkami 2 i 5% udziału objętościowego wolframu, niklu i molibdenu wprowadzanymi dwoma sposobami, w postaci metalicznej i w postaci tlenku metalu, który następnie poddawano redukcji wodorem. Ustalono wpływ obu metod wprowadzania wtrąceń na zahamowanie rozrostu ziaren osnowy, co prowadzi do ujednorodnienia mikrostruktury kompozytu, zapewniając poprawę jego właściwości mechanicznych.

EN

Microstructure of the TZP-based composites (tetragonal zirconia polycrystal) with an addition of 2 and 5 vol. % of tungsten, nickel and molybdenum has been examined. These additives were introduced into the matrix directly as metallic grains or in a form of metal oxide subjected subsequently to reduction with hydrogen. It was found that the inclusions introduced by both methods inhibited growth of the matrix grains which resulted in homogenization of the composite microstructure and improvement of its mechanical properties.

10

Statystyczny opis rozmieszczenia ziarn w polikryształach

Ryś J., Wiencek K.

Rudy i Metale Nieżelazne

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2004

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R. 49, nr 6

282-286

PL

Rozmieszczenie ziarn w polikrysztale może być opisane za pomocą przestrzennego rozmieszczenia środków ziarn oraz relacjami między położeniem środków i rozmiarami ziarn. Stereologiczna analiza za pomocą funkcji korelacji par (PCF) dla środków przekrojów ziarn polikrystalicznego tytanu wskazuje, że ziarna tytanu są rozmieszczone przypadkowo w przestrzeni (tzn. środki ziarn tworzą poissonowskie pole punktowe), natomiast rozmiary sąsiednich ziarn są statystycznie zależne.

EN

The grains arrangement in a polycrystal can be described by the spatial distribution of grain centres as well as by the relations between centre positions and grain sizes. A stereological analysis by means of the pair correlation function (PCF) for grain cross-section centres of polycrystalline titanium indicates that titanium grains are randomly distributed in the space (i.e. the grain centres from Poissonian point field), whereas the sizes of neighbouring grains are statistically dependent.

11

Relation between microstructure and grain boundary conductivity in yttria-doped zirconia.

Rizea A., Petot C., Petot-Ervas G., Kusinski J.

Inżynieria Materiałowa

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2001

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R. XXII, nr 5

784-786

EN

The microstructure grain boundary relation in yttria-doped zirconia has been investigated on polycrystals sintered from powders prepared through two different processing routes. Samples with no evidence for continuous glassy boundary films show the highest grain boundary conductivities (sigma gb) which decrease in presence of alumina additions. On the contrary, samples with boundary glassy films show an increase of sigma gb for small alumina additions (< or = 2 mole%) do likely to a change in the glass phase composition. The same sigma gb activation energy found for the different samples suggests that only "clean" grain-boundaries contribute to the transport processes.

12

Particulate Composites in the TZP-Carbide Systems

Haberko K., Pędzich Z.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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1999

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Vol. 47, nr 4

379-395

EN

The paper presents the results of investigations on particulate ceramic composites with the tetragonal zirconia polycrystalline (TZP) matrix. The WC, CrxCy and TiC particles were used as additives. The possibility of a chemical reaction in these systems was taken into account. Stresses caused by coefficient of thermal expansion mismatch of composite constituents were estimated. Phase composition and microstructure of the composite constituents were estimated. Phase composition and microstructure of the composites were described. Mechanical properties of the composites were measured and compared.

13

Symulacja rozrostu ziarn polikryształu zawierającego cząstki drugiej fazy metodą Monte Carlo.

Sławuta K., Jeziorski L.

Archiwum Nauki o Materiałach

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1999

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T. 20, nr 1

5-25

PL

Kinetykę rozrostu ziarn w polikrysztale zawierającym cząstki drugiej fazy analizowano numerycznie, stosując metodę symulacji Monte Carlo. Opracowany program pozwala śledzić zmiany wyjściowej struktury modelu oraz dokumentuje obraz i wyliczone parametry stereologiczne w każdym punkcie planu eksperymentu. Do ilościowego opisu hamowania rozrostu ziarn przez cząstki drugiej fazy zastosowano wskaźnik, który uzależniono od względnej powierzchni przekrojów cząstek, ich rozdrobnienia, oraz czasu symulacji. Na podstawie otrzymanych wyników stwierdzono, że w analizowanych przypadkach rozkład wielkości ziarn jest logarytmonormalny, a jego parametry można wyrazić również za pomocą AA, LA(A) i czasu symulacji. Wyniki analizy wyznaczanej funkcji rozkładu porównano z teorią Hillerta.

EN

The kinetics of grain growth in the polycrystal containing second-phase particles was analysed numerically using the Monte Carlo simulation method. The developed program makes it possible to monitor changes in the initial model structure, and documents the image and computed stereological parameters in each point of the experiment plan. For the quantitative description of the grain growth inhibition by second-phase particles, an index was used which was related to the relative area and dispersion of particle cross-sections and the simulation time. On the basis of the results obtained it was found that, in the cases analysed, grain size distribution is logarithmic-normal, and its parameters may also be expressed with the use of: AA, L(A) and the simulation time. The results of the determined distribution function were compared with Hillert's theory.

14

Transport properties of (Sn,Ti)O2 polycrystalline ceramics and thin films.

Radecka M., Rękas M., Sobaś P., Zakrzewska K.

Inżynieria Materiałowa

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1998

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R. XIX, nr 4

852-855

EN

Polycrystalline ceramics of (Sn,Ti)O2 were prepared by the impregnation of TiO2 with SnCl4 in the presence of NH3 aq. Rf reactive sputtering from Ti-Sn metallic target was used to deposit thin films. The re-equilibration kinetics were monitored by measuring dc electrical conductivity as a function of temperature, 850 K

15

Ceramic composites based on silicon carbide.

Stobierski L., Lis J., Groger B.

Inżynieria Materiałowa

|

1998

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R. XIX, nr 4

717-722

EN

Silicon carbide possesses many important features. It is very hard, mechanically and chemically resistanced, and retains these properties to high temperature. Because of this, it is an excellent material for ceramic composite matrix. The second, dispersed phase should modify selected properties of SiC. The authors investigations were focused on the preparation of the SiC-based composites for structure application, therefore mechanical properties of the materials were mainly controlled. Simultaneously, electrical properties were also measured for to apply such materials as high-temperature ceramic resistors. The following systems were investigated: SiC-C, SiC-B4C, SiC-TiC and SiC-TiB2. The experiments showed that mechanical and electrical properties could be controlled, particularly a doubled fracture hardness and considerable increasing of strength were noticed. The electrical resistance could be changed by 10 raising to a power 8th times.

16

A study of the residual stresses and their potential effect on yielding of the austenitic stainless steel.

Mizera J., Fillit R., Stolarz J., Kurzydłowski K.J.

Inżynieria Materiałowa

|

1998

|

R. XIX, nr 5

1316-1317

17

3D models of polycrystals.

Cwajna J., Chrapoński J., Maliński M.

Inżynieria Materiałowa

|

1998

|

R. XIX, nr 4

671-676

EN

The 3D computer simulated models of homogenous as well as of inhomogenous microstructure of one phase polycrystalline materials are presented. The models were applied for: verification of correctness of polycrystalline materials models existing in theory of materials properties, assessment of precision and versatility of hitherto used methods for the determination of grains and particles volume distribution as well as for estimation of other stereological parameters and searching for new relations between parameters of plain and spatial materials microstructure. It was shown that the method ensuring the required versatility and accuracy of grain size evaluation at acceptable cost and labor consumption had not been worked out yet. The relationships between mean plane section area of grains and mean grain volume as well as between coefficient of variation of grains plane section area and coefficient of variation of grain volume are presented. They may be the basis of the simple method for the determination of parameters of grain volume distribution.