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1

Difficulties of hydrofracturing in sandstone - experimental study

Vikram S., Kumar Dheeraj, Subrahmanyam D. S.

Journal of Sustainable Mining

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2024

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Vol. 23, iss. 2

160--176

EN

Hydrofracturing in sandstone is not an easy task. Sandstone is porous; fluid dissipation is common hence unable to obtain breakdown pressures in certain flow rates (0.0000005-0.0001 m3/s). The higher flow rate (0.00025 m3/s) is ascertained to determine the fracturing pressures. Due to this, fracture propagation and delineation are observed (Satya Subrahmanyam, 2022) [1]. To enhance, an experimental method is adopted by carrying out 6 Hydrofracturing tests in a borehole comprising sandstone. A high flow rate of 0.00025 m3/s and viscosity 0.001 Pa s is applied. Later, the fracture simulation was run on 12 core samples collected from the same depths in a lab. The fluid flow rates of 0.0000005-0.0000015 m3/s, viscosity 0.27 Pa- second, pore pressure of 4 MPa, confining pressures in vertical-12 MPa and horizontal 6, 18, 24, 30 MPa is applied. The fracture traces and the stress results exhibit a difference of 80°-300° observed in both cases. The major principle stress orientation obtained in the borehole is 20° and 40°. In lab tests with confining horizontal pressures at 6 and 18 MPa, it is 120° and 130°, and at 24 and 30 MPa is 20°. This indicated that there is fracture delineation occurred. It is observed in the higher flow rate and confining pressures.

2

Tests of the Mechanical and Acoustic Parameters of Electric Guitar Bodies

Ryniewicz Andrzej, Pietruch Marcin, Ryniewicz Anna M., Bojko Łukasz

Drewno : prace naukowe, doniesienia, komunikaty

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2024

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Vol. 67, nr 214

Art. no. 194995

EN

The aim of this work was to perform a mechanical and acoustic analysis of electric guitar bodies. Sam ples of ash, oak, walnut, lime tree, and fir were selected for mechanical tests - with constant moisture content, made of latewood, and free from defects. The tests were carried out on a Brinell device to determine the hardness of the wood, and on an MCT3 machine from Anton Paar to determine the microhardness and elastic moduli. The elastic properties of wood are determined by its anisotropy and have different values depending on the direction of force in relation to the fibers. The wood showed the greatest stiffness along the fibers; in the case of forces acting perpendicular to the fibers, the stiffness was much lower. Sound transmission tests of selected acoustic parameters were carried out. They involved measuring and analyzing the frequency and damping of vibrations of guitar bodies using a special vibration sensor. The acoustic parameters of a guitar body experimentally made from walnut were compared with those of a mass-produced Ibanez guitar made of ash wood. Each species of wood has its own characteristic blend of physical properties, such as grain structure, density, weight, and strength, which influence the final tonal power of the guitar. The test results of various wood species indicate significant differences in strength and acoustic-resonance properties, which determine the absorption of vibrations, sound amplification, and sound transmission. The use of a specific wood for a guitar body is dependent on the musician’s artistic vision and the purpose of the instrument.

3

Cubic elasticity of porous materials produced by additive manufacturing: experimental analyses, numerical and mean‑field modelling

Kowalczyk-Gajewska Katarzyna, Maj Michał, Bieniek Kamil, Majewski Michał, Opiela Kamil C.

Archives of Civil and Mechanical Engineering

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2024

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Vol. 24, no. 1

art. no. e34, 2024

EN

Although the elastic properties of porous materials depend mainly on the volume fraction of pores, the details of pore distribution within the material representative volume are also important and may be the subject of optimisation. To study their effect, experimental analyses were performed on samples made of a polymer material with a predefined distribution of spherical voids, but with various porosities due to different pore sizes. Three types of pore distribution with cubic symmetry were considered and the results of experimental analyses were confronted with mean-field estimates and numerical calculations. The mean-field ‘cluster’ model is used in which the mutual interactions between each of the two pores in the predefined volume are considered. As a result, the geometry of pore distribution is reflected in the anisotropic effective properties. The samples were produced using a 3D printing technique and tested in the regime of small strain to assess the elastic stiffness. The digital image correlation method was used to measure material response under compression. As a reference, the solid samples were also 3D printed and tested to evaluate the polymer matrix stiffness. The anisotropy of the elastic response of porous samples related to the arrangement of voids was assessed. Young’s moduli measured for the additively manufactured samples complied satisfactorily with modelling predictions for low and moderate pore sizes, while only qualitatively for larger porosities. Thus, the low-cost additive manufacturing techniques may be considered rather as preliminary tools to prototype porous materials and test mean-field approaches, while for the quantitative and detailed model validation, more accurate additive printing techniques should be considered. Research paves the way for using these computationally efficient models in optimising the microstructure of heterogeneous materials and composites.

4

Mechanical Properties of X3NiCoMoTi 18-9-5 Produced via Additive Manufacturing Technology – Numerical and Experimental Study

Owsiński Robert, Miozga Rafael, Łagoda Agnieszka, Kurek Marta

Advances in Science and Technology. Research Journal

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2024

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Vol. 18, no. 6

45--61

EN

The purpose of the article is to analyze the influence of print orientation, using the DLMS method, on the strength of the tested material before and after heat treatment. The heat treatment involved heating the material to 490˚C and subsequently cooling it within the furnace for four hours. Experimental research involves X3NiCoMoTi 18-9-5 tool steel. Analysis of the test results indicates a strength increase following heat treatment. Additionally, a numerical study was conducted to investigate the mechanical characteristics of X3NiCoMoTi 18-9-5 tool steel fabricated via 3D printing. Fractographic analysis of specimen failure was performed, and the results were subsequently compared.

5

Modelling hysteresis loops of non-oriented electrical steel

Chwastek Krzysztof, Koprivica Branko, Rosić Marko, Gozdur Roman, Gębara Piotr

Przegląd Elektrotechniczny

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2023

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R. 99, nr 11

221--223

EN

Non-oriented electrical steels constitute the most important segment of the market of soft magnetic materials. In the paper the usefulness of the model based on hyperbolic tangent nonlinear transformation for the description of quasi-static hysteresis loops for this type of material is verified.

PL

Blachy elektrotechniczne o ziarnach niezorientowanych stanowią najważniejszy segment rynku materiałów magnetycznie miękkich. W pracy zweryfikowano użyteczność modelu opartego na nieliniowej transformacji tangens hiperboliczny do opisu quasi-statycznych pętli histerezy dla tego typu materiału.

6

Electro-optical performance and anisotropic transport study of a Ga-free type-II superlattice barrier structure

Bouschet Maxime, Arounassalame Vignesh, Ramiandrasoa Anthony, Perez Jean-Philippe, Péré-Laperne Nicolas, Ribet-Mohamed Isabelle, Christol Philippe

Opto-Electronics Review

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2023

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Vol. 31, Special Issue

art. no. e144549

EN

In the past ten years, InAs/InAsSb type-II superlattice has emerged as a promising technology for high-temperature mid-wave infrared photodetector. Nevertheless, transport properties are still poorly understood in this type of material. In this paper, optical and electro-optical measurements have been realised on InAs/InAsSb type-II superlattice midwave infrared photodetectors. Quantum efficiency of 50% is measured at 150 K, on the front side illumination and simple pass configuration. Absorption measurement, as well as lifetime measurement are used to theoretically calculate the quantum efficiency thanks to Hovel’s equation. Diffusion length values have been extracted from this model ranging from 1.55 μm at 90 K to 7.44 μm at 200 K. Hole mobility values, deduced from both diffusion length and lifetime measurements, varied from 3.64 cm²/Vs at 90 K to 37.7 cm²/Vs at 200 K. The authors then discuss the hole diffusion length and mobility variations within temperature and try to identify the intrinsic transport mechanisms involved in the superlattice structure.

7

Influence of anisotropy of mechanical properties on hydrogen induced cracking

Kukołowicz Łukasz, Oleszak Dariusz

Ochrona przed Korozją

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2023

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nr 2

38--43

EN

Hydrogen induced cracking is a form of wet H2S cracking. Blistering or crack propagation is a result of the mechanical tearing of material by high-pressure hydrogen gas forming on internal material discontinuities, like non-metallic inclusions. This failure mechanism is typically associated with low and medium-strength pipeline steels, however, it does also occur in high-strength rolled wire. This evaluation aims to elucidate the mechanism of this susceptibility. The characteristic failure pattern where cracking occurs near the wire centreline and propagates perpendicular to the rolling direction leads to believe that the wire anisotropy, developed during cold rolling, plays a critical role. A mechanical property – flow resistance in principal directions – was measured using the Wheeler and Ireland technique. It was found that the “weak” direction is perpendicular to the crack propagation direction. The failure rate does not correspond to the flow resistance, but rather to the flow resistance ratios. It is proposed that those ratios are not only a measure of anisotropy but also a measure of microstructural damage inflicted by the cold rolling process. This microstructural damage is partially reversible by heat treatment processes.

PL

Pękanie wodorowe jest mechanizmem degradacji często zachodzącym w środowiskach korozyjnych, w których występuje siarkowodór. Propagacja pęknięć postępuje na skutek fizycznego rozrywania materiału przez cząsteczkowy wodór pod wysokim ciśnieniem, tworzący się na nieciągłościach wewnętrznych, takich jak na przykład wtrącenia niemetaliczne. Praca badawcza dotyczy mechanizmu pękania wysoko wytrzymałego kształtowego drutu stalowego. Drut pęka w charakterystyczny sposób: pęknięcie tworzy się w pobliżu środka drutu i propaguje równolegle do płaskich powierzchni. Obserwacja ta każe przypuszczać, że propagacja związana jest z anizotropią właściwości mechanicznych drutu. Anizotropię zbadano jako opór płynięcia plastycznego materiału pod wgłębnikiem twardościomierza metodą Wheelera i Irelanda. Zaobserwowano, że pęknięcia propagują prostopadle do kierunku, w którym występuje najmniejszy opór płynięcia. Pękanie podczas testów w środowisku korozyjnym z siarkowodorem nie jest skorelowane bezpośrednio z oporem płynięcia, a ze stosunkiem oporów płynięcia w dwu kierunkach, a więc miarą anizotropii. Z badań wynika, że proces walcowania na zimno powoduje uszkodzenia mikrostruktury, które można szacować miarą anizotropii właściwości mechanicznych drutu i które są częściowo odwracalne w procesie obróbki cieplnej.

8

Influence of soil anisotropic stiffness on the deformation induced by an open pit excavation

Lisewska Katarzyna, Cudny Marcin

Archives of Civil Engineering

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2023

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Vol. 69, nr 4

141--156

EN

In this paper, the problem of deformation induced by an open pit excavation in anisotropic stiff soils is analysed by FE modelling. The presented research is focused on the influence of material model with anisotropic stiffness on the accuracy of deformation predictions as compared with the field measurements. A new hyperelastic-plastic model is applied to simulate anisotropic mechanical behaviour of stiff soils. It is capable to reproduce mixed variable stress-induced anisotropy and constant inherent cross-anisotropy of the small strain stiffness. The degradation of stiffness depending on strain is modelled with the Brick-type model. The model formulation and parameters are briefly presented. General deformation pattern obtained in the exemplary 2D boundary value problem of an open pit excavation is investigated considering different values of inherent cross-anisotropy coefficient of small strain stiffness. The numerical simulations are performed as a coupled deformation-flow analysis which allows to properly model the drainage conditions. The excavation phases are simulated by removal of soil layers according to the realistic time schedule. Finally, the monitored case of the trial open pit excavation in heavily overconsolidated Oxford Clay at Elstow, UK is simulated with proposed material model both in 2D and 3D conditions. The obtained calculation results are compared with displacement measurements and discussed.

PL

Modelowanie numeryczne zagadnień geotechnicznych związanych z odciążeniem podłoża (np. tunelowanie, wykopy) wymaga odpowiedniego opisu materiałowego gruntu, który pozwala na prawidłową symulację charakterystyki mechanicznej w zakresie małych odkształceń. Najważniejszymi elementami są tutaj nieliniowość sztywności związana z barotropią oraz degradacją stycznego modułu ścinania z odkształceniem oraz inherentna anizotropia sztywności. Modele konstytutywne dostępne w popularnych systemach obliczeniowych rzadko pozwalają na uwzględnienie anizotropii sztywności w zakresie małych odkształceń. Najczęściej przyczyną jest bardziej skomplikowana procedura implementacji niż w przypadku modeli z izotropową sztywnością, jak również ograniczona dostępność parametrów materiałowych związanych z anizotropią. Rozwój technik pomiarowych w eksperymentalnej mechanice gruntów, obserwowany w ostatnich latach na całym świecie, pozwala jednak na zaprojektowanie i przeprowadzenie badań anizotropii sztywności w warunkach ważnych inwestycji lub projektów badawczych. Najczęściej jest to pomiar współczynnika anizotropii αG w aparacie trójosiowym wyposażonym w elementy sejsmiczne bender zorientowane zarówno w pionie jak i w poziomie. System taki pozwala na bezpośrednie wyznaczenie modułów ścinania w płaszczyźnie pionowej Gvh oraz poziomej Ghh (αG= Ghh/Gvh). W artykule przedstawiono własny hipersprężysto-plastyczny model konstytutywny uwzględniający zarówno nieliniowość jak i anizotropię sztywności w zakresie małych odkształceń. W modelu tym wykorzystano anizotropową hipersprężystość do opisu sztywności początkowej, system zagnieżdżonych powierzchni plastyczności w przestrzeni odkształcenia do opisu degradacji sztywności (tzw. model Brick) oraz konwencjonalne kryterium wytrzymałości na ścinanie do ograniczenia dewiatorowych stanów naprężenia. Model został zaimplementowany w programie metody elementów skończonych Plaxis w ramach opcji User Defined Soil Model (UDSM). Analizowanym zagadnieniem brzegowo początkowym jest próbny otwarty wykop wykonany w ile oxfordzkim w Elstow, Wielka Brytania. Szeroka baza danych dotyczących niestandardowych badań laboratoryjnych iłu oksfordzkiego zorientowanych, oprócz wyznaczenia parametrów standardowych, na charakterystykę anizotropii sztywności dostępna jest w literaturze. Dokładny opis realizacji wykonanego próbnego wykopu z danymi pozwalającymi na przeprowadzenie własnych analiz wraz z wynikami monitoringu przemieszczeń dostępne są w publikacji Hird&Pierpoint (Geotechnique 47(3), 1997). Umożliwiło to, kalibrację parametrów anizotropowego modelu hipersprężysto-plastycznego i przeprowadzenie analizy wstecz będącej cenną weryfikacją przydatności opracowanego modelu konstytutywnego. Przed wykonaniem symulacji numerycznych próbnego wykopu w Elstow przeprowadzono również serię obliczeń na uproszczonym przykładowym modelu wykopu otwartego w płaskim stanie odkształcenia w celu rozpoznania wpływu czystej anizotropii inherentnej na deformację powstającą podczas odciążenia podłoża gruntowego takim wykopem. Symulację numeryczną wykopu próbnego w Elstow przeprowadzono zarówno w płaskim stanie odkształcenia jak i na modelu przestrzennym. Metoda symulacji odpowiadała podejściu sprzężonemu konsolidacji z równoczesnym uwzględnieniem przepływu wody w gruncie (coupled deformation flow analysis). Warunki czasowe wykonania wykopu próbnego, jak również parametry filtracyjne oraz mechaniczne zalegających gruntów powodują jednak, że przedmiotowe zagadnienie brzegowo-początkowe zachodzi ostatecznie w warunkach bliskich warunkom braku drenażu. Wyniki przeprowadzonych symulacji numerycznych porównano z wynikami monitoringu przemieszczenia. Uzyskano zadowalającą zgodność obliczonego i pomierzonego pola przemieszczenia. Dokładność wyników obliczeń jest jednak zmienna w zależności od obszaru analizowanego zagadnienia. Odpowiednie porównania przedstawiono na rysunkach w artykule.

9

Anisotropy on the ductile-to-brittle transition for rock in process of drilling

He Mingming, Wang Jing, Yuan Zhuoya, Wang Haoteng, Ma Xudong, Luo Bo

Acta Geophysica

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2023

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Vol. 71, no. 5

2107--2124

EN

Anisotropy is an inherent property of rocks. It refers to the different response of the rock properties in each direction. Understanding the anisotropy characteristics of rock failure by drilling has practical applications in improving drilling efficiency, especially for engineering applications. In this paper, a criterion is established to clarify the ductile-to-brittle transition in the drilling process of rock. Moreover, a new anisotropy index has been proposed to evaluate the effect of anisotropy on the critical state of the ductile-to-brittle transition. The digital drilling tests are conducted on six types of rock to study the drilling mechanical performance in the X, Y, and Z directions. The anisotropy characteristics of drilling parameters and mechanical specific energy (MSE) are analysed at the critical state of ductile–brittle failure. The results show that the critical state of ductile–brittle failure is manifested as an inflection point of the depth of cut. The evolution of MSE is fitted as two linear functions, which corresponds to the two stages. The order of anisotropy in MSE is obtained as: gneiss > slate > red sandstone > granite > argillaceous sandstone > sandstone. The anisotropy in the uniaxial compressive strength and MSE for different rock types has the same sequences. The advantages of the proposed method in determining rock anisotropy are illustrated.

10

Anisotropic Interfacial Adhesion between Fluoropolymers and RDX Single Crystal Faces

Liu Jiahui, Zhou Xiaoqing, Qian Wen, Gong Feiyan, Yang Zhijian, Li Hongzheng, Nie Fude

Central European Journal of Energetic Materials

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2022

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Vol. 19, no. 4

409--423

EN

Interfacial interactions have an important influence on the properties of energetic materials. The anisotropy of interfacial adhesive strength between various 1,3,5-trinitro-1,3,5-triazinane (RDX) single crystal faces and a typical binder was studied in this work by experimental and theoretical investigations. An RDX single crystal was prepared and processed into three kinds of orientated crystal faces, including (002), (020) and (210). These crystal slices were used as substrates, and fluorinated polymer F2314 was used as a binder. The surfaces of the RDX slices were analyzed by X-ray photoelectron spectroscopy (XPS) and an atomic force microscope (AFM). The work of adhesion was obtained from direct tensile tests, using designed samples of the sandwich structure of RDX-F2314-RDX, with various RDX single crystal surfaces. The polarity component of the surface energy and the work of adhesion was obtained by Young’s equation and the Fowkes theory, based on surface contact angle tests. The results in this work indicated the anisotropy of the interfacial adhesion of F2314 on various RDX crystal faces.

11

Anisotropy of structural and mechanical properties in CuCrZr alloy following hydrostatic extrusion process

Przybysz Sylwia, Kulczyk Mariusz, Skiba Jacek, Skorupska Monika

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2022

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Vol. 70, nr 4

art. no. e141725

EN

The methods of severe plastic deformation (SPD) of metals and metal alloys are very attractive due to the possibility of refinement of the grains to nanometric sizes, which facilitates obtaining high mechanical properties. This study investigated the influence of SPD in the process of hydrostatic extrusion (HE) on the anisotropy of the mechanical properties of the CuCrZr copper alloy. The method of HE leads to the formation of a characteristic microstructure in deformed materials, which can determine their potential applications. On the longitudinal sections of the extruded bars, a strong morphological texture is observed, manifested by elongated grains in the direction of extrusion. In the transverse direction, these grains are visible as equiaxed. The anisotropy of properties was mainly determined based on the analysis of the static mini-sample static tensile test and the dynamic impact test. The obtained results were correlated with microstructural observations. In the study, three different degrees of deformation were applied at the level necessary to refine the grain size to the ultrafine-grained level. Regardless of the applied degree of deformation, the effect of the formation of a strong morphological texture was demonstrated, as a result of which there is a clear difference between the mechanical properties depending on the test direction, both by the static and dynamic method. The obtained results allow for the identification of the characteristic structure formed during the HE process and the more effective use of the CuCrZr copper alloy in applications.

12

Effects of the Coiling Temperature and Anisotropy on the Tensile Properties of High-Strength API X70 Linepipe Steel

Oh Dong-Kyu, Shin Seung-Hyeok, Lee Sang-Min, Hwang Byoungchul

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 4

1487--1490

EN

In this study, the effect of the coiling temperature on the tensile properties of API X70 linepipe steel plates is investigated in terms of the microstructure and related anisotropy. Two coiling temperatures are selected to control the microstructure and tensile properties. The API X70 linepipe steels consist mostly of ferritic microstructures such as polygonal ferrite, acicular ferrite, granular bainite, and pearlite irrespective of the coiling temperature. In order to evaluate the anisotropy in the tensile properties, tensile tests in various directions, in this case 0° (rolling direction), 30°, 45° (diagonal direction), 60°, and 90° (transverse direction) are conducted. As the higher coiling temperature, the larger amount of pearlite is formed, resulting in higher strength and better deformability. The steel has higher ductility and lower strength in the rolling direction than in the transverse direction due to the development of γ-fiber, particularly the {111}<112> texture.

13

Shear-Induced Molecular Orientation of Compression Moulded PE-HD Sheets

Chomiak Monika, Stabik Józef

Advances in Science and Technology. Research Journal

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2022

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Vol. 16, no. 4

85--95

EN

The article presents experimental results on orientation of polymer macromolecules in compression moulded high density polyethylene sheets. Properties anisotropy of thermoplastic films or sheets, that are usually formed in the extrusion process, causes deformation of thermoformed products and is a serious technological problem. One of the possible solutions of this problem is application of compression moulded sheets. The paper presents the results of tests of selected strength characteristics of compression moulded PE-HD sheets. A static tensile test was performed and Charpy impact strength was determined. Additionally Chrystler’s orientation test was executed. For comparison the same experiments were performed on extruded sheets. Samples were cut in directions perpendicular and parallel to the direction of polymer flow in pressing and extrusion processes. The obtained results indicate that the compression moulding technique allows the production of sheets that do not exhibit statistically significant anisotropy of the tested strength properties.

14

An Elastic-Plastic Analysis of Polycrystalline Structure Using Crystal Plasticity Modelling – Theory and Benchmark Tests

Wójcik Marta, Skrzat Andrzej

Advances in Science and Technology. Research Journal

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2022

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Vol. 16, no. 5

163--177

EN

Numerical simulations of tension and shear tests for a polycrystalline, anisotropic material were performed using crystal plasticity theory. The slip was considered here as the main mechanism of plastic deformation. Constitutive equations to describe the elastic-plastic deformation caused by the slip are presented. The generation and meshing of various shapes geometries (cubic and paddy shapes) with randomly-orientated grains by means of open source program NEPER program was shown. The Voronoi tessellation was used in order to include morphological properties of a crystalline material. The selected results of elastic-plastic analyses (stress, strain distributions and the macroscopic stress-strain resulting from homogenization) are presented here. The results obtained show the non-uniform distribution of stress and strain for different grains associated with their crystal orientation. The crystal plasticity finite element modelling of materials subjected to plastic deformation is important for microstructure-based mechanical predictions, as well as for the engineering design and to perform simulations involving not only the change of a material’s shape at a macro level but also the phenomena occurring in material in a micro-scale.

15

Hydrodynamics and turbulence anisotropy for complex flow in a sinuous channel

Taye Jyotismita, Kumar Bimlesh

Acta Geophysica

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2022

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Vol. 70, no 5

2269--2282

EN

Sinuous channel flows are the most natural form of alluvial streams. The complex flow in the channel bends has been the main focus of the study. This paper examines the flow velocity and the three-dimensional velocity fluctuations in a pure sinuous channel. The main focus of the study is on the characterization of turbulence anisotropy along the sinuous bend. Experiments were conducted in a sinuous channel of a rectangular cross-section to identify the turbulence present in the flow. Secondary flow, Reynolds shear stress, turbulent kinetic energy, and anisotropy turbulence were evaluated in the sinuous bend. The bend apex is composed of a large circulation cell at the center of the bend section. The maximum Reynolds shear stress (RSS) is located at the bend apex with the streamwise-transverse and transverse-vertical components of RSS showing high peaks of positive and negative values. This fact is in support of the secondary flow observed in this study. Anisotropic stress tensors were estimated at different bend sections and are shown to have greater contribution toward streamwise and transverse direction. Anisotropic invariant map (AIM) identified the turbulence at bend sections and varying flow depth. Two dimensional, cigar-shaped, and pancake-shaped turbulence was observed at the bend upstream and downstream. Isotropic turbulence was observed at the bend apex. Near the bed (z∕h ≤ 0.2) and away from the bed (z∕h ≥ 0.4), pancake-shaped and cigar-shaped turbulence was observed.

16

Elastic full waveform inversion in VTI media using logging data constraints and gradient precondition

Xu Yipeng, Zhang Kai, Li Zhenchun, He Zilin, Gao Jinfeng, Zhao Xianyang

Acta Geophysica

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2022

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Vol. 70, no 4

1665--1676

EN

Elastic full waveform inversion (EFWI) in VTI media using velocity model-based parameterization (PARM-VTIEFWI) can improve the sensitivity of anisotropic parameters, but there are still the problems of gradient’s interference and Nonunique. Research has shown that logging data can constrain the Non-unique of FWI. Therefore, in this paper, we use the logging data as a constraint to limit the Non-unique of the PARM-VTIEFWI. We derive the objective function and gradient equation for the PARM-VTIEFWI based on the constraint of logging information. In addition, to reduce the interference between the gradients of parameters in VTI media, we incorporate a pseudo-Hessian matrix to precondition the gradients and derive a gradient preconditioning formula based on the pseudo-Hessian matrix in this paper. In summary, we propose a new PARM-VTIEFWI method based on logging information constraint and gradient precondition, which reduces the interference between the parameter gradients and constrains the Non-unique of the inversion. The correctness and validity of the method were demonstrated by examples.

17

Nowe metody charakteryzacji materiałów dielektrycznych w zakresie mikrofalowym oraz fal milimetrowych

Karpisz Tomasz

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

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2021

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nr 4

101--105

PL

Artykuł jest poświęcony rozwojowi jednowymiarowego, skalarnego, wielowarstwowego, elektromagnetycznego modelu otwartego rezonatora Fabry-Perot, wykorzystanego do pomiarów własności elektromagnetycznych elektrycznie cienkich warstw dielektryków na częstotliwości od 20 do 110 GHz. Pokrótce omówiono podstawy teoretyczne metody opisującej zachowanie fali elektromagnetycznej w otwartym rezonatorze Fabry-Perot oraz proces projektowania takiego układu pomiarowego. Następnie przedstawiono układ pomiarowy, kolejno zaprezentowano niektóre z wyników pomiarów wykonanych podczas prac związanych z doktoratem autora publikacji. Pod koniec omówiono ograniczenia omawianej metody oraz możliwe ścieżki rozwoju.

EN

This paper is focused on the introduction of a one-dimensional scalar multi-layer electromagnetic model of a Fabry-Perot open resonator and its use in the measurement of electromagnetic properties of electrically thin dielectric sheet materials in frequencies from 20 to 110 GHz. Short theoretical description of an electromagnetic wave inside resonator have been described. Furthermore, results of measurement for frequencies exceeding 50 GHz have been shown as well as unique capability of measurement of the samples with in-plane anisotropy. In the end measurement system limitation have been discussed with possibilities for further system development.

18

Influence of atherosclerosis on anisotropy and incompressibility of the human thoracic aortic wall

Kozun Marta, Chwilkowska Agnieszka, Pezowicz Celina, Kobielarz Magdalena

Biocybernetics and Biomedical Engineering

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2021

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Vol. 41, no. 1

15--27

EN

In this study, we analysed the influence of atherosclerosis on the anisotropic and incompressible behaviour of the human thoracic aortic wall under mechanical loads. The mechanical tests involved preparations of the human thoracic aortic wall, which were evaluated based on the six-stage histological classification of atherosclerosis proposed by Stary. Anisotropy was evaluated on the basis of directional tests of mechanical properties, which were determined based on a uniaxial tensile test conducted in two directions, i.e. longitudinal and circumferential. The evaluation of incompressibility was carried out based on the product of the stretch ratios obtained in the x–y and y–z planes and on the basis of Poisson's ratio. The results presented in this study indicate that the blood vessel wall is an anisotropic material only in the case of normal vessels and in early atherosclerotic lesions. Atherosclerosis progression causes a gradual loss of the anisotropic character of the work of the thoracic aortic wall in moderate and very advanced stages of atherosclerosis under mechanical loads. The results show that the wall of the thoracic aorta is an incompressible material. Development of atherosclerosis does not cause a loss of incompressibility of the thoracic aorta. This study is the only one so far that presents changes in the mechanical properties at all stages of atherosclerotic development. A large number of preparations were included in the study, which is important for the results obtained due to the multi-factorial etiology of atherosclerosis development.

19

Linking static and dynamic mechanical properties for metamorphic rocks from Austria including their anisotropic efect

Gegenhuber Nina, Krueger Melanie

Acta Geophysica

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2021

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Vol. 69, no. 2

539--546

EN

The derivation of geomechanical properties from petrophysical/geophysical data is not only of great importance in the oil industry but also in mining, geothermal projects and tunnelling, for reduction of costs and to improve security. For the oil industry and geothermal sector, it is mainly important for drilling rate and the stability of the borehole and, as a result, the economic factor. A key issue is that geomechanical properties, which can support a better planning of a project, cannot be measured in the borehole or on the surface directly. In this study, the focus is put on anisotropic efects on the correlation between static and dynamic properties, which is neglected in most studies but important because values can vary extremely. Therefore, measurements in the geotechnical laboratory of compressional and shear wave velocity during uniaxial compression strength test were taken. Additionally, typical properties like bulk and grain density as well as porosity were determined too. Diferent samples (carbonate–silica schist, marble and phyllite) from the "Zentrum am Berg"-research tunnelling centre at the "Erzberg" in Austria were used. Shown are correlations between uniaxial compression strength and compressional wave velocity as well as for static and dynamic Young’s modulus including their anisotropic efect. The results are promising and provide an opportunity for further applications on log data.

20

An efcient multiparameter acoustic anisotropic full-waveform inversion depending on parameterization

Shin Youngjae, Oh Ju Won, Min Dong Joo

Acta Geophysica

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2021

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Vol. 69, no. 4

1257--1267

EN

The pressure-based acoustic approximation of the elastic wave equations in anisotropic media has advantages corresponding to computational efciency and numerical stability. However, the numerical scattering potentials from the anisotropic parameter perturbations for the pressure wavefeld are not consistent with the elastic scattering theory. In multiparameter full-waveform inversion (FWI), choosing a suitable parameterization, considering the acquisition parameters (e.g., the ofsetto-depth ratio and frequency band) and the accuracy of the anisotropy information in the background initial velocity model, is an important component to a successful anisotropic parameter estimation, because the parameterization determines the trade-of between inverted model parameters and their resolution power. However, because it is difcult to perform multiparameter FWI with various types of parameterization using the pressure-based acoustic wave equation, inaccurate scattered wavefelds cause the gradient direction to lose its unique properties with respect to each model parameter. To overcome these issues, we adopt the combination of pressure- and vector-based acoustic wave equations converted vector virtual sources, which preserves the computational efciency and the angular dependency of the partial derivative wavefelds in elastic media. With the proposed method, we generate the numerical PP scattering patterns for various parameterizations, which are consistent with the elastic scattering theory. Through the numerical tests using the synthetic anisotropic Marmousi-II models and a real ocean bottom cable dataset from the North Sea, we conduct acoustic FWI with three diferent parameterizations using the proposed method and verify that the modifed scattering patterns accurately refect the characteristics of the anisotropic parameter perturbations.