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1

Boundary element modeling of pyroelectric solids with shell inclusions

Sulym H., Pasternak I., Pasternak V.

Mechanics and Mechanical Engineering

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2018

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Vol. 22, nr 3

727--737

EN

The paper presents general boundary element approach for analysis of thermoelectroelastic (pyroelectric) solids containing shell-like electricity conducting permittive inclusions. The latter are modeled with opened surfaces with certain boundary conditions on their faces. Rigid displacement and rotation, along with constant electric potential of inclusions are accounted for in these boundary conditions. Formulated boundary value problem is reduced to a system of singular boundary integral equations, which is solved numerically by the boundary element method. Special attention is paid to the field singularity at the front line of a shell-like inclusion. Special shape functions are introduced, which account for this square-root singularity and allow accurate determination of field intensity factors. Numerical examples are presented.

2

Torsion of functionally graded anisotropic linearly elastic circular cylinder

Baksa A., Ecsedi I.

Engineering Transactions

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2018

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Vol. 66, iss. 4

413--426

EN

The object of this paper is Saint-Venant torsion of functionally graded anisotropic linearly elastic circular cylinder. The class of anisotropy considered has at least one plane of elastic symmetry normal to the axis of the circular cylinder. The elastic coefficients have radial dependence only. Here, we give the solution of Saint-Venant torsion problem for circular cylinder made of functionally graded anisotropic linearly elastic materials.

3

Boundary element analysis of anisotropic thermomagnetoelectroelastic solids with 3D shell-like inclusions

Pasternak I., Sulym H.

Acta Mechanica et Automatica

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2017

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Vol. 11, no. 4

308--312

EN

The paper presents novel boundary element technique for analysis of anisotropic thermomagnetoelectroelastic solids containing cracks and thin shell-like soft inclusions. Dual boundary integral equations of heat conduction and thermomagnetoelectroelasticity are derived, which do not contain volume integrals in the absence of distributed body heat and extended body forces. Models of 3D soft thermomagnetoelectroelastic thin inclusions are adopted. The issues on the boundary element solution of obtained equations are discussed. The efficient techniques for numerical evaluation of kernels and singular and hypersingular integrals are discussed. Nonlinear polynomial mappings are adopted for smoothing the integrand at the inclusion’s front, which is advantageous for accurate evaluation of field intensity factors. Special shape functions are introduced, which account for a square-root singularity of extended stress and heat flux at the inclusion’s front. Numerical example is presented.

4

Application of anisotropic thin plate theory for development of displacements for silicon <111> crystals plates in cylindrical systems

Javidinejad A.

International Journal of Applied Mechanics and Engineering

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2016

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Vol. 21, no. 4

879--890

EN

Silicon <111> crystal is one of the crystal orientations, which shows potential for application in micro device developments of pressure diaphragms for measurement purposes. To date, no theoretical basis has been examined to develop the deflections for computational analysis purposes [1]. This paper presents the development of the diaphragm deflections for Silicon <111> Crystal in Cylindrical coordinates system. The Silicon <111> crystal possesses transverse isotropic properties. Thus, an anisotropic thin plate theory is used here to develop the plate deflection. A numerical example is given to compare the theoretical results with Finite Element Analysis (FEA) results.

5

Electrical Properties of PPy-Coated Conductive Fabrics for Human Joint Motion Monitoring

Hu J., Zhang X., Li G., Yang X., Ding X.

Autex Research Journal

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2016

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Vol. 16, no. 1

7--12

EN

Body motion signals indicate several pathological features of the human body, and a wearable human motion monitoring system can respond to human joint motion signal in real time, thereby enabling the prevention and treatment of some diseases. Because conductive fabrics can be well integrated with the garment, they are ideal as a sensing element of wearable human motion monitoring systems. This study prepared polypyrrole conductive fabric by in situ polymerization, and the anisotropic property of the conductive fabric resistance, resistance–strain relationship, and the relationship between resistance and the human knee and elbow movements are discussed preliminarily.

6

Boundary integral equations for an anisotropic bimaterial with thermally imperfect interface and internal inhomogeneities

Sulym H., Pasternak I., Tomashivskyy M.

Acta Mechanica et Automatica

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2016

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Vol. 10, no. 1

66--74

EN

This paper studies a thermoelastic anisotropic bimaterial with thermally imperfect interface and internal inhomogeneities. Based on the complex variable calculus and the extended Stroh formalism a new approach is proposed for obtaining the Somigliana type integral formulae and corresponding boundary integral equations for a thermoelastic bimaterial consisting of two half-spaces with different thermal and mechanical properties. The half-spaces are bonded together with mechanically perfect and thermally imperfect interface, which model interfacial adhesive layers present in bimaterial solids. Obtained integral equations are introduced into the modified boundary element method that allows solving arbitrary 2D thermoelacticity problems for anisotropic bimaterial solids with imperfect thin thermo-resistant interfacial layer, which half-spaces contain cracks and thin inclusions. Presented numerical examples show the effect of thermal resistance of the bimaterial interface on the stress intensity factors at thin inhomogeneities.

7

Determination of material parameters of isotropic and anisotropic hyper-elastic materials using boundary measured data

Hajhashemkhani M., Hematiyan M. R.

Journal of Theoretical and Applied Mechanics

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2015

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Vol. 53 nr 4

895—910

EN

Identification of mechanical properties of isotropic and anisotropic materials that demonstrate non-linear elastic behavior, such as rubbers and soft tissues of human body, is critical for many industrial and medical purposes. In this paper, a method is presented to obtain the mechanical constants of Mooney-Rivlin and Holzapfel hyper-elastic material models which are employed to describe the behavior of isotropic and anisotropic hyper-elastic materials, respectively. By using boundary measured data from a sample with non-standard geometry, and by using an iterative inverse analysis technique, the material constants are obtained. The method uses the results of different experiments simultaneously to obtain the material parameters more accurately. The effectiveness of the proposed method is demonstrated through three examples. In the two first examples, the simulated measured data are used, while in the third example, the experimental data obtained from a polyvinyl alcohol sample are used.

8

Blank shape optimization on deep drawing of a twin elliptical cup using the reduced basis technique method

Golshani M H, Jabbari A.

Advances in Science and Technology. Research Journal

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2015

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Vol. 9, nr 27

72--77

EN

In this project thesis, initial blank shape optimization of a twin elliptical cup to reduce earring phenomenon in anisotropic sheet deep drawing process was studied .The purpose of this study is optimization of initial blank for reduction of the ears height value. The optimization process carried out using finite element method approach, which is coupled with Taguchi design of experiments and reduced basis technique methods. The deep drawing process was simulated in FEM software ABAQUS 6.12. The results of optimization show earring height and, in addition, a number of design variables and time of process can be reduced by using this methods. After optimization process with the proposed method, the maximum reduction of the earring height would be from 21.08 mm to 0.07 mm and also it could be reduced to 0 in some of the directions. The proposed optimization design in this article allows the designers to select the practical basis shapes. This leads to obtain better results at the end of the optimization process, to reduce design variables, and also to prevent repeating the optimization steps for indirect shapes.

9

Determination of the Elastic Constants of Plain Woven Fabrics by a Tensile Test in Various Directions

Penava Ž., Šimić-Penava D, Knezic Ž

Fibres & Textiles in Eastern Europe

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2014

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Vol. 22, no. 2 (104)

57--63

EN

In this paper the values of elastic constants of woven fabrics for different angles of extension direction were analysed. Four types of fabric samples of different raw material composition and the same type of weave were tested under tensile forces in seven directions oriented with a 15° increment with respect to the weft direction. The elasticity modulus and Poisson’s ratio of the woven fabrics were determined experimentally in a laboratory. Based on the experimentally obtained values, theoretically calculated elastic constants for arbitrarily chosen fabric directions were calculated. A good agreement between the experimental results and values of the elastic constants calculated was shown, hence the theoretical equations can be used with high accuracy to calculate the elastic constants of fabric in various directions. Therefore the measurements need to be undertaken when the tensile force is acting on the fabric only in the warp, weft and at an angle of 45°.

PL

W pracy przeanalizowano stałe elastyczności tkanin rozciąganych pod różnymi kątami. Badano próbki wykonane z różnych materiałów ale o tym samym splocie. Próbki rozciągano w kierunkach o przesunięciu co 150 licząc od kierunku wątku. Badano moduł elastyczności i współczynnik Poissona. Testy przeprowadzono w warunkach laboratoryjnych. Korzystając z wyników eksperymentów przeprowadzono teoretyczne obliczenia stałych elastyczności dla wybranych kierunków rozciągania. Stwierdzono dobrą zgodność wyników, dzięki czemu można wyciągnąć wniosek, że zastosowane wzory mogą służyć do obliczeń stałych elastyczności z dużą dokładnością. Dlatego pomiary takie powinny być przeprowadzane jeżeli siły rozciągające tkaninę działają tylko w kierunku osnowy, wątku i pod kątem 45 stopni.

10

Doubly periodic cracks in the anisotropic medium with the account of contact of their faces

Maksymovych O., Pasternak I., Sulym H., Kutsyk S.

Acta Mechanica et Automatica

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2014

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Vol. 8, no. 3

160--164

EN

The paper presents complex variable integral formulae and singular boundary integral equations for doubly periodic cracks in anisotropic elastic medium. It utilizes the numerical solution procedure, which accounts for the contact of crack faces and produce accurate results for SIF evaluation. It is shown that the account of contact effects significantly influence the SIF of doubly periodic curvilinear cracks both for isotropic and anisotropic materials.

11

Doubly Periodic Sets of Thin Branched Inclusions in the Elastic Medium: Stress Concentration and Effective Properties

Sulym H., Pasternak I., Kutsyk S., Grodzki W.

Acta Mechanica et Automatica

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2013

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Vol. 7, no. 1

48-52

EN

This paper considers the doubly periodic problem of elasticity for anisotropic solids containing regular sets of thin branched inclusions. A coupling principle for continua of different dimension is utilized for modeling of thin inhomogeneities and the boundary element technique is adopted for numerical solution of the problem. The branches of the inclusion can interact both inside the representative volume element and at the interface of neighbor representative elements. A particular example of the elastic medium reinforced by a doubly periodic set of I-beams is considered. Stress intensity and stress concentration inside and outside thin inclusions are determined. The dependence of the effective mechanical properties of the reinforced composite material on the volume fraction of the filament and its rigidity is obtained.

12

Calculation of reflection and transmission coefficients for qP waves incident on a planar interface between isotropic and triclinic media

Li L.

Acta Geophysica

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2008

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Vol. 56, no. 2

518-528

EN

In the paper by Chattopadhyay and Rajneesh (2006, "Reflection and refraction of waves at the interface of an isotropic medium over a highly anisotropic medium", Acta Geophysica, vol. 54, no. 3, pp. 239-249), the authors proposed a process to calculate R/T (reflection and transmission) coefficients at the interface between isotropic and triclinic half-spaces, with incident qP waves in triclinic media. Unfortunately, besides several misprints, the authors made a fatal assumption that there is no transmitted SH wave generated in isotropic media, which led the successive analytical derivations and numerical calculations thoroughly wrong. In this paper, the errors are analyzed at length and corrections are given. Then an alternative approach to solve the problem is proposed and numerical results are shown and discussed.

13

Mikrostruktura i właściwości anizotropowych magnesów NdFeB wytwarzanych w procesie odkształcenia termoplastycznego.

Lipiec W.

Prace Naukowe Instytutu Podstaw Elektrotechniki i Elektrotechnologii Politechniki Wrocławskiej. Konferencje

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2006

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Vol. 44, nr 18

238-242

PL

Obecnie stopy NdFeB są stosowane na skalę przemysłową jako materiały do produkcji magnesów trwałych 0 najwyższej gęstości energii. Aby w pełni wykorzystać możliwości tetragonalnej fazy Nd2FeMB konieczne jest uporządkowanie osi "c" krystalicznych ziaren. Istnieją dwie, zupełnie różne, metody wytwarzania anizotropowych magnesów NdFeB o wysokiej gęstości energii. Jedna oparta jest na konwencjonalnej technologii proszkowej, w której stosuje się proszek o monokrystalicznych cząstkach oraz pole magnetyczne w celu ich uporządkowania [1]. Druga metoda wykorzystuje drobnokrystaliczny (50 nm) stop NdFeB, który jest rozdrabniany do stosunkowo dużych palikrystalicznych cząstek. Drobnokrystaliczną morfologię materiału wytwarza się w wyniku szybkiego chłodzenia (10 5-10 6 st C/s) ciekłego metalu. Taka postać proszku zapewnia dużą koercję magnesu (wskutek bardzo małych ziaren w polikrystalicznych cząstkach) a jednocześnie utrudnia utlenianie (mała powierzchnia kontaktu materiału z atmosferą). Proszek o polikrystalicznych cząstkach nie może być orientowany za pomocą pola magnetycznego. Stąd anizotropię magnesu uzyskuje się w tym wypadku na drodze dwuetapowego prasowania na gorąco [2-3]. W pierwszym etapie powstaje izotropowy magnes o gęstości bliskiej teoretycznej. Natomiast drugi etap ma na celu wytworzenie tekstury, którą uzyskuje się w procesie odkształcenia termoplastycznego. Napisano wiele prac analizujących wpływ odkształcenia plastycznego na gorąco na mikrostrukturę, właściwości magnetyczne, oraz na związek między ciśnieniem a prędkością odkształcenia [4-16]. Mimo to mikrostrukturalny mechanizm zarówno samego odkształcenia jak i porządkowania ziaren nie jest jeszcze w pełni zrozumiały. Najczęściej przyjmuje się, że odkształcenie i orientacja powstają w wyniku kombinacji anizoiropowego rozrostu ziaren i ich obrotów oraz poślizgu na granicach. Anizoiropowy rozrost ziaren miałby zachodzić w wyniku dyfuzji wzdłuż lub w poprzek granic ziaren. Poślizg na granicach rozumiany jest jako mechaniczne przemieszczanie ziaren ułatwiane przez międzyziarnową fazę ciekłą, która pełni rolę środka poślizgowego. Inna teoria (tłumacząca powstawanie makroskopowej anizotropii w tego typu magnesach opiera się na mechanizmie rozpuszczania 1 wytrącania. Mówi ona, że pod wpływem nacisku i temperatury ziarna zorientowane osią c inaczej niż równolegle do siły nacisku rozpuszczają się całkowicie, natomiast pochodząca z cieczy materia zarodkuje i rozrasta się na ziarnach, które się nie rozpuściły [17]. Przy czym, przyjmuje się, że kryształy zorientowane kierunkiem c zgodnie z siłą nacisku nie ulegają rozpuszczeniu. Dzieje się tak wskutek anizotropowych właściwości sprężystych tetragonalnej fazy NdFeB. Anizotropia ta powoduje, że energia nagromadzona w krysztale zależy od jego orientacji względem siły nacisku. W tych ziarnach, gdzie jest ona większa rozpuszczanie materiału zachodzi w niższej temperaturze. Czynniki te dają w efekcie selektywną rozpuszczalność ziaren w zależności od ich orientacji.

EN

Using MQP - A powder NdFeB hot pressed isotropic magnets was produced. Then, applying thermoplastic deformation process isotropic precursors were processed into anisotropic mugnets. Isotropic samples shown satisfactory magnetical proprieties. However anisotropic magnets characterized comparatively small remanence and coercivity. In the aim of explanation such result following investigations were executed: content of oxygen, microstructural and magnetical proprieties of the material.

14

Reflection and refraction of waves at the interface of an isotropic medium over a highly anisotropic medium

Chattopadhyay A., Rajneesh H.

Acta Geophysica

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2006

|

Vol. 54, no. 3

239-249

EN

In this paper, we have considered the reflection and refraction of a plane wave at an interface between two half-spaces. The lower half-spaces is composed of highly anisotropic triclinic crystalline material and the upper half-space is homogeneous and isotropic. It has been assumed that due to incidence of a plane quasi-P (qP) wave, three types of waves, namely, quasi-P (qP), quasi-SV (qSV) and quasi-SH (qSH), will be generated in the lower half space whereas P and S waves will be generated in the upper half space. The phase velocities of all the quasi waves have been calculated. It has been assumed that the direction of particle motion is neither parallel nor perpendicular to the direction of propagation. Some specific relations have been established between directions of motion and propagation, respectively. The expressions for reflection coefficients of qP, qSV, qSH and refracted coeffi-cients of P and SV waves are obtained. Results of reflection and refraction coeffi-cients are presented.

15

HBV deep mesa etching in InGaAs/InAlAs/AlAs heterostructures on InP substrate

Górska M., Wrzesińska H., Szerling A., Hejduk K., Ratajczak J., Łysko J.M.

Materials Science Poland

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2005

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Vol. 23, No. 1

221--226

EN

The chemical composition of newly developed anisotropic etching solution and several experimental results obtained with heterostructure barrier varactor (HBV) deep mesa formation are presented. The novel solution enables the deep etching of the InGaAs/InAlAs/AlAs heterostructure over InP substrate, up to 5 žm in the [100] crystal direction. It ensures etch-stop at the InP substrate and gives almost perfect surface quality, with mesa profiles meeting device design requirements. The etching solution is a mixture of two components: A (H2SO4:H2O2:H2O = 1:1:8) and B (C6H8O7:H2O = 1:1), in the proportion B:(H2O2 content in A) =1:1.

16

FDTD analysis of magnetized plasma using an equivalent lumped circuit

Moryc A., Gwarek W.

Journal of Telecommunications and Information Technology

|

2005

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nr 2

75-78

EN

The paper describes a new approach to electromagnetic analysis of magnetized plasma using finite difference time domain (FDTD) method. An equivalent lumped circuit describing an FDTD cell filled with plasma is developed and applied in the analysis. Such a method is proved more effective than previously reported methods. The new approach is verified on a canonical example of known analytical solution.

17

Razruszenije anizotropnych plastinok s ostrougolenymi otverstijami

Bożidarnik V., Sulim G.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Mechanika

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2001

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Z. 73

289-296

EN

A limiting loading and an angle of an initial crack growth direction from a hole's sharprecovery point in an anisotropic plate under an all-round bending are examined. It is considered, that the crack grows in a direction of greatest possible damage ratio in a prefracture zone, defined by the stress intensity factors of circular stress and a fracture toughness of a material at the moment ehen damage ratio achieves a critical value.

18

Fluktuacje prędkości na wysokości samozasysającego mieszadła tarczowego

Stelmach J.

Inżynieria Chemiczna i Procesowa

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2001

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T. 22, z. 3E

1315--1320

PL

Dopplerowskim anemometrem laserowym zmierzono pulsacje prędkości na wysokości otworów wylotowych samozasysającego mieszadła tarczowego. Stwierdzono bardzo duże różnice fluktuacji prędkości w obszarze mieszadła, świadczące o anizotropowości przepływu. Poza mieszadłem można przyjąć izotropowość przepływu z wyjątkiem bezpośredniej bliskości ścianki mieszalnika.

EN

Using laser Doppler anemometer the velocity fluctuations were measured at high of self-aspirating disk impeller outlets. Significant differences of the velocity fluctuations were found near the impeller blades. In this region the flow was anisotropic. Outside of impeller, the isotropic flow can be assumed (except for the tank wall neighbourhood).