Wyniki wyszukiwania - Biblioteka Nauki

1

Próba wyznaczenia parametrów znamionowych bezszczotkowych silników synchronicznych wzbudzanych magnesami trwałymi

100%

Mrozek A.

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2008

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tom Nr 80

217-222

EN

The paper presents the results of measurements of brushless permanent magnet synchronous motors (PMSM) and the methodology of the rating determination. The PMSM have two different rotor construction. The first one has a surface mounted block magnets, while the second has radial embedded magnets in the rotor yoke. All the PMSM motors are based on a stator from the small power asynchronous motor. The investigated motors are supplied by the sinusoidal voltage sources during the test. The characteristics of the armature current versus the load torque for the several values of supply voltages are measured. The characteristics of the armature current versus the supply voltage for the several values of the load torque are measured, as well. During the tests temperature in several points of motor were measured. The motor performances were determined in thermal steady state. The temperature distribution on the motor casing were measured by the thermal camera.

2

Molecular models of polycrystalline and porous materials

100%

Mrozek A.

|

2014

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tom 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

Application of the Coupled Boundary Element Method With Atomic Model in the Static Analysis

63%

Mrozek A. , Burczyński T.

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tom Vol. 7, No. 2

284-288

EN

1. Introduction The models of material behaviour in the atomistic scale allows us to understand the micro and macroscopic events. The algorithm based on the boundary element method (BEM) coupled with a discrete atomistic model is presented in this paper. In this approach, the material behaviour at the molecular level can be simulated and the total number of degrees of freedom is reduced, because in most cases only a small part of the mulitiscale model contains molecules and BEM doesn’t need discretization of the continuum’s domain. 2. The molecular model The discrete molecular model is applied to simulate deformations of the atomistic lattice under loads. This model is based on the equilibrium equations of atomic interaction forces. These pair-wise interaction forces between each two molecules in the lattice are computed as derivative of the interatomic potential respect to the distance between two atoms. In this work, the empirical Lennard-Jones and the Morse potentials were used to describe interatomic behaviour [4]. The force equilibrium equations are computed for all the nearest-neighbour atoms interactions and then, assembled into the global non-linear system of equations [2]. Constraints are applied using elimination method. The Newton-Raphson method is used to solve that system of equations. The main concept is to assume some initial positions of molecules (eg. undeformed lattice) and obtain final, stable equilibrium configuration of atoms. The equilibrium state of the lattice corresponds to the minimal value of the total potential energy of the atomic structure. The process of minimization of the potential energy can be also done by using the evolutionary algorithm [3]. The applications of these algorithms in prediction of atoms distribution give a great probability of finding the global optimal solutions. 3. The mulitiscale model The multiscale model is composed from three main blocks: the continuum model, the interface domain and the discrete atomic model. The boundary element method [1] is used to simulate material behaviour at the continuum level. The interface domain contains so-called embedded atoms which coordinates are equal to the corresponding nodes of boundary elements. Firstly, the macroscale boundary conditions are applied and the BEM model is solved. Displacements of the interface atoms are obtained and introduced as initial displacements of the outer boundary of the atomic lattice. In the next step, equilibrium positions of the atoms in the nanoscale model are computed, using the method described above. Finally, forces acting on interface atoms are computed and introduced as a nodal forces to the BEM model. These computations are repeated until achieved displacements are satisfactory small. 3. Final remarks Some simulations of a dislocation behaviour and deformations of the atomic lattice are performed. Both hexagonal and orthogonal configurations of the lattice are considered. The convergence of the Newton-Raphson method and the total number of iterations strongly depend on the initial positions of the atoms and their displacements taken form BEM. However, for small deformations of the atomic structure, the Newton-Raphson method is faster than the evolutionary algorithm. This kind of analysis gives possibility of simulation, e.g. slips, crack behaviour and fracture at the molecular level and also may be used in modelling some technological processes in material science. The application of loads and displacements to the BEM continuum model is easier then direct in the molecular level. 4. Acknowledgement: The research is financed by the Foundation for Polish Science (2005-2008). 5. References [1] T. Burczynski (1995), The Boundary Element Method in Mechanics, WNT, Warsaw (in Polish) [2] Y. W. Kwon (2003). Discrete atomic and smeared continuum modelling for static analysis Engineering Computations, Vol. 20 No. 8. 964–978. [3] A. Mrozek, W. Kus, P. Orantek, T. Burczynski (2005). Prediction of the aluminium atoms distribution using evolutionary algorithm, Recent Developments in Artificial Intelligence Methods, ed. T. Burczynski, W. Cholewa, M. Moczulski, AI-METH Series, Gliwice. 127-130. [4] R. Sunyk, P. Steinmann (2002). On higher gradients in continuum-atomistic modelling, International Journal of Solids and Structures, No. 40. 6877-6896.

4

The quality of roe deer [Capreolus c. capreolus L.] and an assessment of the management of its populations in the Olsztyn district of the Polish Hunting Association

63%

Zalewski D. , Mrozek A.

Polish Journal of Natural Sciences

|

2006

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tom 20

277-289

5

Właściwości silników synchronicznych z magnesami trwałymi rozmieszczonymi na powierzchni wirnika

63%

Miksiewicz R. , Mrozek A.

Zeszyty Naukowe. Elektryka / Politechnika Śląska

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1999

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tom z. 168

137-146

PL

W artykule przedstawiono wyniki analizy 3-fazowego silnika synchronicznego z magnesami trwałymi rozmieszczonymi na powierzchni wirnika. Na podstawie wyznaczonych rozkładów indukcji magnetycznej w szczelinie stojan-wirnik (przy wykorzystaniu MES i programu FEMAG-DC) obliczono indukcyjności oddziaływania twornika w zależności od prądu twornika dla różnych sposobów umieszczenia magnesów na biegunach i sposobu magnesowania oraz wyznaczono moment reluktancyjny silnika wynikający z użłobkowania stojana. Opierając się na wyznaczonych nieliniowych parametrach schematu zastępczego obliczono charakterystyki eksploatacyjne silnika.

EN

Results of calculations of armature inductances of a synchronous motor with permanent magnets mounted on the rotor surface have been presented in the paper. The method based on the theory of a two-axis, salient pole synchronous machine and field analysis have been used for investigation of the motor properties. The program FEMAG-DC, which uses the FEM method, has been applied to field calculations. The armature reaction inductances as a function of armature current for different thickness of the air gap as well as for embedded and surface mounted magnets have been determined basing on the calculated distribution of magnetic flux density in the air gap The exemplary characteristics of the motor armature current as a function of a supply voltage have been calculated.

6

Examination of mechanical properties of graphene allotropes by means of computer simulation

63%

Mrozek A. , Burczyński T.

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tom Vol. 20, no. 4

309--323

EN

The eﬀective mechanical properties and the stress-strain relations of the eight types of the graphene allotropes are presented in this paper. Series of the tensile and shear tests are performed using the nonequilibrium molecular dynamics (NEMD) and the adaptive intermolecular reactive bond order (AIREBO) potential. The methodology of the investigation as well as obtained results are explained and discussed in detail. Where possible, the achieved results are compared with the data available in the scientiﬁc literature in order to validate our molecular dynamics models and simulations. In other cases, i.e., where only information about structural or electronic properties is available, presented results can complement the knowledge about these particular planar carbon networks.

7

Hybrid parallel evolutionary algorithm in optimization of 2d grapehene-like materials

51%

Mrozek A. , Kuś W. , Burczyński T.

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tom Vol. 15, No.1

103--110

EN

Development and application of the hybrid parallel evolutionary-conjugated gradient algorithm for searching for new, stable atomic arrangements of the two-dimensional graphene-like carbon lattices was described in this paper. The main goal of the optimization is to find stable arrangements of carbon atoms under imposed conditions (e.g. density, shape and size of the unit cell). Such configurations correspond to the minimal values of the total potential energy of the atomic system. Thus, the fitness function is formulated as the total potential energy of the atoms. Interactions between carbon atoms are modeled using Adaptive Intermolecular Reactive Bond Order potential. The parallel approach used in computations allows significant reduction of computation time. Validation of the achieved results and example of the model of new 2D material obtained using presented method were presented in this paper. The numerical scalability tests of the algorithm were performed on the IBM BlueGcne/Q supercomputer

PL

W artykule przedstawiona została metoda optymalizacji płaskich sieci zbudowanych z atomów węgla. Proponowane podejście bazuje na połączeniu równoległego algorytmu ewolucyjnego z metodą gradientu sprzężonego. Funkcją celu jest wartość energii potencjalnej całego układu atomów. Głównym zadaniem algorytmu jest znalezienie stabilnych położeń atomów w komórce elementarnej - odpowiadających minimum energii potencjalnej całego układu. Algorytm ewolucyjny został zrównoleglony (podział populacji na części), ponadto wspomagający go algorytm gradientowy (wbudowany w program LAMMPS) może również być uruchomiony w wersji sekwencyjnej, jak i równoległej. Jako model oddziaływań między atomami węgla zastosowano potencjał AIREBO, uwzględniający różne stany hybrydyzacji atomów węgla. W pracy zaprezentowano wyniki optymalizacji obejmujące poszukiwania znanych materiałów literatury płaskich materiałów grafenopodobnych, jak i nowych konfiguracji. Ponadto, dla nowych struktur wyznaczono parametry mechaniczne.