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1

Metody oceny pianotwórczości i stabilności piany

Traczyk-Truba Olga, Marzec Marta, Nowak Izabela

Chemik

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2025

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Nr 2-3

116--120

PL

Przeprowadzono przegląd literaturowy dotyczący piany i jej stabilności. Zwrócono uwagę na kluczowe czynnikami reologiczne takie jak napięcie powierzchniowe, lepkość roztworu, lepkoelastyczność filmu międzyfazowego oraz parametry geometrii bąbli. Skoncentrowano się na stabilizacji piany dzięki surfaktantom, które obniżają napięcie powierzchniowe i tworzą warstwy ochronne na granicy faz. Ich efektywność zależy od budowy cząsteczki, stężenia względem CMC oraz kinetyki adsorpcji. Podano także informacje na temat lepkoelastyczności filmu międzyfazowego (mechanizm Plateau–Marangoniego–Gibbsa), która decyduje o odporności na deformacje, zaś równowaga sił van der Waalsa, elektrostatycznych i sterycznych determinuje ciśnienie rozłączające w ściankach bąbli. W ostatniej części omówiono metody pomiaru parametrów pianotwórczości i stabilności.

EN

A review, with 27 refs., of foam formation and its stability. Key rheological factors, such as surface tension, solution viscosity, interfacial film viscoelasticity, and bubble geometry parameters, were highlighted. The focus was on foam stabilization through surfactants, which lower surface tension and form protective layers at the interface. Their effectiveness depends on the molecular structure, concentration relative to CMC, and adsorption kinetics. Information on interfacial film viscoelasticity (Plateau–Marangoni–Gibbs mechanism), which determines resistance to deformation, was also provided, while the balance of van der Waals, electrostatic, and steric forces determines the separation pressure in bubble walls. The methods for measuring foam formation and stability parameters were presented.

2

Analytical solution of Atangana-Baleanu fractional viscoelastic relaxation model – Laplacian approach

Khan Muhammad Sabeel, Sagheer Ayesha, Azeem Zarafshan

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2025

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Vol. 73, nr 5

art. no. e154145

EN

In this contribution, a new novel approach based on the Atangana-Baleanu fractional in conjunction with the Laplacian approach is utilized to obtain an analytical solution of a fractional time relaxation viscoelastic model. The fractional time relaxation model is based on the upper convected Maxwell constitutive relaxation equation. Results for the existence and uniqueness of the solution are presented. Analytical expressions of the solutions are obtained for the underlying physical time relaxation viscoelastic model. Two test model problems with prescribed initial conditions are used to investigate the intricate behaviour of the viscoelastic two-dimensional fluid. The influence of key parameters such as relaxation time, Reynolds number and the order of the fractional derivative on fluid flow characteristics is analyzed and discussed.

3

Methods of assessing concrete creep in prestressed bridge structures

Nowak Krzysztof, Oleszek Radosław, Zbiciak Artur

Archives of Civil Engineering

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2025

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Vol. 71, nr 3

369--384

EN

The paper discusses the phenomenon of concrete creep, its mechanical models and simplified as well as more sophisticated methods of estimating creep effects applied in the design of bridge structures. The section on simplified methods describes the metod of substitutive concrete elasticity modulus and the method of estimating creep effects with the correction factor Ccreep for spans with precast beams. Among the precise methods, it presents the modified effective modulus method (Trost 1967), age-adjusted effective modulus method (Bažant 1972) and the general incremental method according to the linear theory of elasticity. Methods for computationally accounting for creep according to current PN-EN standards, withdrawn Polish standards, and recommendations from foreign literature are characterized. The impact of creep on the redistribution of internal forces during the incremental erection of the structure was demonstrated using examples of a viaduct made of precast beams and a bridge constructed using balanced cantilever method. Attention was drawn to the possibilities of extending the description of creep phenomena in concrete bridge structures using the conceptual framework of fractional-order derivatives.

PL

W referacie omówiono zjawisko pełzania betonu, jego modele mechaniczne oraz uproszczone i bardziej wyrafinowane sposoby szacowania efektów pełzania stosowane w projektowaniu konstrukcji mostowych. W części dotyczącej metod uproszczonych opisano metodę – efektywnego modułu sprężystości oraz metody współczynnika korekcyjnego Ccreep stosowane w przypadku przęseł z belek prefabrykowanych. Spośród dokładnych metod przedstawiono m.in. metodę zmodyfikowanego efektywnego modułu sprężystości (Trost 1967), metodę efektywnego modułu sprężystości betonu dostosowanego do wieku jego obciążenia (Bažant 1972) oraz metodę przyrostową według liniowej teorii sprężystości. Scharakteryzowano metody obliczeniowego ujęcia pełzania według aktualnych przepisów PN-EN, wycofanych norm polskich oraz w zaleceniach i literaturze zagranicznej. Zaprezentowano wpływ pełzania na redystrybucję sił wewnętrznych przy etapowym wznoszeniu ustroju na przykładzie wiaduktu z belek prefabrykowanych i mostu budowanego metodą betonowania nawisowego. Zwrócono uwagę na możliwości rozszerzenia opisu zagadnień pełzania w betonowych konstrukcjach mostowych przy użyciu aparatu pojęciowego pochodnych ułamkowego rzędu.

4

Stress relaxation in sugar beet root under various mechanical load conditions

Kołodziej Paweł, Stropek Zbigniew, Gołacki Krzysztof

Advances in Science and Technology. Research Journal

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2025

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Vol. 19, no. 2

296--303

EN

Identification and determination of the mechanical properties of biological materials, especially fruits, vegetables and industrial plants, can be made using commonly applied stress relaxation tests. They are of particular significance because their results make it possible to propose a mechanical model of studied material. The aim of the study was to determine the effects of initial deformation and deformation velocity on the parameters of generalised Maxwell model during stress relaxation in the sugar beet root. The tests were carried out by means of the texture analyser (model TA.HD plus, Stable Micro Systems, Goldaming, UK) at the three deformations: 2.0, 3.5 and 5.0 mm and the four deformation velocities: 1, 2, 10, and 20 mm·s–1. The cut sugar beet samples used in the experiment were cylindrical in shape, with a 9.5 mm diameter and a 20 mm height. They were initially compressed along the vertical axis in a state of uniaxial stress and constant deformation was maintained while recording the force response for 35 seconds. The two-branched generalised Maxwell model with an additional elastic element was used to describe the experimental force response curves. The sample dimensions as well as the initial deformation velocity were taken into consideration in the model formula. Two relaxation times of the model decreased with the increasing deformation velocity and increased with the increasing deformation value. The dependences of the obtained relaxation times on the phenomena inside the tissue such as the flow of fluids and gases under the load were interpreted. Changes of model parameters as a function of deformation velocity could testify the appearance of internal micro damages in the material during deformation. The tendency of increase in the peak force response along with the increase of deformation velocity shows typical viscoelastic behaviour of sugar beet root flesh.

5

Analysis of the dynamics of the rolling process of multilayer viscoelastic bodies

Rydz Dariusz, Salwin Mariusz, Pałęga Michał, Chmielewski Tomasz

Advances in Science and Technology. Research Journal

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2025

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Vol. 19, no. 2

63--72

EN

The paper identifies deformations in layers of laminated composite sheets shaped in the rolling process. Rolling process of layered composites is a dynamic issue, for which the problem is to precisely determine the value of deformations of individual sheet components resulting from differences in their properties. The aim of this work was to determine the impact of delayed viscoelastic effects on increasing the computational accuracy of deformations of metal layers constituting the AlMg5+Al1050+M1E layered composite. Three three-parameter Jeffreys models connected in parallel were used to analyze the course of changes in deformation of laminar composite layers. The presented test results refer to the determination of the deformation values in the rolling valley and the zone of delayed viscoelastic effects. The work showed that the solution used contributed to increasing the accuracy of the calculations.

6

Random eigenvibrations of beams with viscoelastic layers

Kamiński Marcin, Przychodzki Maciej, Łasecka-Plura Magdalena, Guminiak Michał, Lenartowicz Agnieszka

Journal of Theoretical and Applied Mechanics

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2024

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Vol. 62 nr 4

763--767

EN

This paper is devoted to the study of the influence of random variation of model parameters of a beam with viscoelastic layers on probabilistic characteristics of its natural frequencies and dimensionless damping coefficients. The relationships between the model parameters and the dynamic characteristics of the beam were approximated by quartic polynomials based on the results of calculations using FEM, where beam finite elements were used, taking into account lamination of the beam. The nonlinear eigenproblem was solved using the continuation method. The calculation results for an example laminated beam are presented.

7

Study on Viscoelastic Poisson's Ratio of Nonwovens

Yong Li, Yuhang Kou, Tengteng Xia, Heying Chu, Lei Li

Fibres & Textiles in Eastern Europe

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2024

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Vol. 32, no. 2

51--56

EN

Combined with Laplace transform and creep stress conditions, an accurate expression of the viscoelastic Poisson’s ratio calculated from the transverse strain and relax modulus is derived. From creep and relax tests data, Prony series of the transverse strain and relax modulus of nonwovens with time were obtained, and the time-varying curve of the viscoelastic Poisson’s ratio of nonwovens was simulated by 1stOpt software. The method proposed can effectively obtain the viscoelastic Poisson’s ratio of nonwovens and provide a reference value for calculating mechanical indexes involved in its subsequent production and processing.

8

Design and application of ISSA-BP neural network model for predicting soft tissue relaxation force

Yan Yongli, Ren Teng, Dind Li, Sun Tiansheng

Acta of Bioengineering and Biomechanics

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2024

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Vol. 26, no. 4

89--98

EN

Accurate biomechanical modeling is crucial for enhancing the realism of virtual surgical training. This study addressed the computational cost and complexity associated with traditional viscoelastic models by incorporating neural network algorithms, thereby augmenting the predictive capability of soft tissue modeling. Methods: To address these challenges, the present study proposed a novel biomechanical modeling approach. The approach establishes a relaxation prediction model based on the backpropagation (BP) neural network and optimizes it using an enhanced sparrow search algorithm (ISSA). This hybrid method leverages the dynamic characteristics of forceps to predict the relaxation force of soft tissues more accurately. The ISSA optimizes the model by integrating chaos mapping, nonlinear inertia weight, and vertical–horizontal crossover strategy, which helps overcome the issue of local optima and boosts the predictive performance. Results: The experimental results demonstrated that the R2 values reached 0.9956 for the pig kidney and 0.9896 for the pig stomach, indicating the model’s exceptional precision in predicting relaxation forces. Conclusions: The relaxation force prediction model based on ISSA-BP neural network provides excellent predictive performance, offering a new and effective strategy for biomechanical modeling of soft tissues in virtual surgical systems.

9

Assessment of the mechanical properties of muscles in adults in relation to the position of the hip bones – preliminary study

Szajkowski Sebastian, Dwornik Michał, Pasek Jarosław, Cieślar Grzegorz

Acta of Bioengineering and Biomechanics

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2024

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Vol. 26, no. 4

19--27

EN

Asymmetry in the form of Lumbo–Pelvic–Hip Complex (LPHC) is a common phenomenon in the adult population. No consensus has been reached in the literature reviewed, as far as the impact of posture defects upon the occurrence of muscle imbalance, faster development of degenerative changes in the joints and pain intensity are concerned. Thus, it needs to be defined clearly in which cases the diagnosis of (LPHC) asymmetry in adults provides the basis for starting rehabilitation. The aim of the study was to determine whether in the case of this asymmetry changes in the viscoelastic and biomechanical properties of LPHC muscles occur. Methods: The study comprised 64 adults, divided into two groups on the basis of physical examination: pelvic symmetrical (n = 34), and pelvic asymmetrical (n = 30). Myotonometric measurements of output parameters: tension, stiffness and elasticity were carried out to assess the mechanical properties of LPHC muscles in both groups. Results: Tension, stiffness and elasticity of the examined muscles, namely: abdominal muscles, rectus femoris muscle, erector muscle of the spine and biceps femoris muscle were measured. The pelvic symmetrical group, and the pelvic asymmetrical group did not differ with statistical significance as regards the comparison between the left and right sides of the body of the subjects. Also, no statistically significant differences in the occurrence of pain were found between the study groups. Conclusions: Our findings have important clinical implications. The asymmetry of LPHC, commonly diagnosed in adults during functional examination for the purpose of physiotherapy, should not provide the basis for starting rehabilitation, in the absence of pain.

10

Effect of hydroxypropyl methyl cellulose on rheological properties of cement-limestone paste

Guan Ling, Liu Xiaolin, Liu Xinyuan

Archives of Civil Engineering

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2023

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Vol. 69, nr 1

593--612

EN

The effects of hydroxypropyl methylcellulose (HPMC) on the rheology and viscoelasticity of cement-limestone paste were evaluated, as was the mechanism of HPMC from the viewpoint of zeta potential and adsorption amount. The results revealed that the greater the content of HPMC or the viscosity of its aqueous solution, the lower the fluidity of the composite paste and therefore the higher the rheological parameters. The relation between torque and rotational velocity of cement-limestone paste is linear; nevertheless, the shear thickening degree of paste increased following the addition of HPMC, demonstrating typical viscoelastic properties. The addition of HPMC prolonged the induction duration and delayed the emergence of the exothermic peak of hydration, decreased zeta potential and conductivity, and increased the propensity of suspension particles to agglomerate. The adsorption amount of polycarboxylate superplasticizer (PCE) decreased with increasing aqueous solution viscosity and HPMC concentration due to the winding effect of HPMC’s high molecular chain structure and the competing adsorption of HPMC and PCE.

11

Rheological and tribological behavior of polyacrylamide-base solutions for artificial synovial fluid

Klekotka Marcin, Grykin Monika Izabela, Dąbrowski Jan Ryszard

Acta of Bioengineering and Biomechanics

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2023

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Vol. 25, no. 2

49--59

EN

This paper presents tribological and rheological analysis results of artificial synovial fluid base solutions. Special attention was paid to polyacrylamide preparations with different molecular weights and concentrations. Methods: Tribological tests were conducted using the Al2O3–CoCrMo friction pair in the presence of investigated lubricants. Confocal microscopy was used to analyze and assess of volume, depth, and width of wear traces. Moreover, the viscosity and viscoelasticity tests of analyzed solutions were carried out. The rheological measurements were focused on the oscillatory tests, which allowed us to determine the elasticity modulus (G′) and viscosity (G″). Results: Viscoelastic nature of the tested preparations depends on the strain rate. It has been shown that elastic properties dominate at higher frequencies. The molecular weight of the polymer has a particular influence on these properties. The most promising results were obtained for 6% and 8 % high molecular weight polyacrylamide compositions. Conclusions: However, all tested polyacrylamide solutions show better rheological and tribological characteristics than commercial preparation based on hyaluronic acid.

12

Rheological properties of elastic-visco-plastic liquid

Dadash-Zade Mirza A., Aliyev Inglab N.

Nafta-Gaz

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2022

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R. 78, nr 11

801--804

EN

A model for the motion of a compressible elastic-viscous-plastic fluid in a round pipe is proposed. The main indicators of the flow, volume flow and speed are obtained. Numerous hydrodynamic processes are associated with the properties of liquids. It is known that the mechanical and physical properties of liquids can be described by various models. Various models have been proposed that partially describe the processes of hydromechanics. The proposed model makes it possible to qualitatively describe the deformation processes that occur in various systems. To describe a closed theory of motion of a continuous medium and, in particular, between stress and strain, it is necessary to have a mechanical model. From the literature analysis it is known that there are simple models, which include elastic, viscous and plastic. At the same time, it should be noted that the mechanical model partially shows the mechanical state of the elastic body in the form of Hooke's law. Practice shows that there are more complex liquids that do not obey this law. One of these fluids is an elastic-viscousplastic fluid. In this work, a model is proposed that describes the elastic-viscous-plastic properties of liquids, which sequentially connects the elastic and viscous-plastic elements. For such a medium, the total resistance will be the sum of the stress corresponding to the elastic deformation and the stress caused by the viscous-plastic resistance. Based on the proposed model, an equation is obtained taking into account the coefficient of volumetric elastic expansion, and an equation is obtained for determining the velocity distribution over the pipe section and volume flow for a given liquid. Calculations have shown that with an increase in compressibility, the flow rate of the liquid partially increases, which in some practical cases produces a positive effect.

PL

W artykule zaprezentowano model ruchu ściśliwej cieczy sprężysto-lepkoplastycznej w rurze o przekroju okrągłym. Uzyskano główne wskaźniki przepływu, przepływu objętościowego i szybkości. Liczne procesy hydrodynamiczne są związane z właściwościami cieczy. Wiadomo, że właściwości mechaniczne i fizyczne cieczy można opisać za pomocą różnych modeli. Zaproponowano modele, które częściowo opisują procesy mechaniki cieczy. Przedstawiony model umożliwia jakościowy opis procesów odkształcenia zachodzących w różnych systemach. Model mechaniczny jest konieczny do opisania zamkniętej teorii ruchu ośrodka ciągłego, w szczególności pomiędzy naprężeniem i odkształceniem. Z analizy literatury wiadomo, że istnieją proste modele obejmujące ciecze sprężyste, lepkie i plastyczne. Należy jednocześnie zauważyć, że model mechaniczny częściowo przedstawia stan mechaniczny ciała sprężystego, wykorzystując prawo Hooke’a. Praktyka pokazuje, że istnieją ciecze bardziej złożone, niezachowujące się zgodnie z tym prawem. Jednym z takich płynów jest płyn sprężysto-lepkoplastyczny. W niniejszej pracy zaproponowano model opisujący właściwości sprężysto-lepkoplastyczne cieczy, który sekwencyjnie łączy elementy sprężyste i lepkoplastyczne. W przypadku takiego ośrodka opór całkowity jest sumą naprężenia odpowiadającego odkształceniu sprężystemu i naprężenia spowodowanego przez opór lepkoplastyczny. Na podstawie zaproponowanego modelu uzyskano równanie uwzględniające współczynnik objętościowej rozszerzalności sprężystej, a także uzyskano równanie do określenia rozkładu szybkości na przekroju rury oraz przepływu objętościowego dla danej cieczy. Obliczenia pokazały, że ze wzrostem ściśliwości szybkość przepływu cieczy częściowo wzrasta, co w pewnych praktycznych przypadkach daje pozytywny efekt.

13

A new conservative finite difference scheme for 1D Cahn-Hilliard equation coupled with elasticity

Shimura Kazuki, Yoshikawa Shuji

Journal of Applied Analysis

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2022

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Vol. 28, nr 2

311--332

EN

In this article, we give analysis for a structure-preserving finite difference scheme to the Cahn-Hilliard system coupled with elasticity in one space dimension. In the previous article [K. Shimura and S. Yoshikawa, Error estimate for structure-preserving finite difference schemes of the one-dimensional Cahn-Hilliard system coupled with viscoelasticity, in: Regularity and Asymptotic Analysis for Critical Cases of Partial Differential Equations, RIMS Kôkyûroku Bessatsu B82, Research Institute for Mathematical Sciences (RIMS), Kyoto (2020), 159-175], we studied the system coupled with viscoelasticity, where we proposed a conservative numerical scheme for the system which inherits the total energy conservation and momentum conservation laws, and showed the error estimate. However, the error estimate can not be applied to the system without viscosity, due to the fact that the proof relies on the viscous term. Here, we show the error estimate for the system without viscosity by proposing a new structure-preserving finite difference scheme for the system. In addition, we also give the proof of existence of solution for the scheme.

14

Wykorzystanie reologii oscylacyjnej do określenia parametrów mechanicznych hydrożeli krzemianowo-polimerowych

Słupecki Szymon, Mastalska-Popławska Joanna, Izak Piotr

Materiały Ceramiczne

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2021

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T. 73, nr 2

92--100

PL

W pracy przedstawiono wyniki pomiarów reologicznych mających na celu określenie właściwości lepkosprężystych hydrożeli krzemianowo-polimerowych na bazie szkła wodnego sodowego i poliakrylanu sodu o stosunku masowym 1:2, 1:1 i 2:1. Do tego celu wykorzystano dwa rodzaje badań reologicznych, tj. pomiary oscylacyjne przy stałej częstotliwości i amplitudzie drgań (1 Hz i 0,3%), a także testy pełzania przy stałym naprężeniu ścinającym wynoszącym 10 Pa. Na podstawie otrzymanych wyników badań stwierdzono, że wszystkie analizowane próbki można zakwalifikować jako ciała lepkosprężyste ze znaczną przewagą właściwości sprężystych, gdyż ich kąt przesunięcia fazowego δ był znacznie mniejszy niż 45°. Właściwości najbardziej zbliżone do idealnie sprężystych wykazywały próbki hydrożeli o stosunku masowym szkła wodnego sodowego do akrylanu sodu 1:2. Uzupełnieniem tych informacji były wyniki testów pełzania. Stwierdzono, że wraz z rosnącym udziałem szkła wodnego sodowego i poliakryloamidu wzrasta stopień odkształcenia próbki w trakcie obciążenia. Czyli rosnący udział wagowy szkła wodnego i akryloamidu zwiększa udział sprężystości opóźnionej (lepkiej), kosztem sprężystości nieopóźnionej.

EN

The paper presents the results of rheological measurements aimed at determining the viscoelastic properties of polymer-silicate hydrogels based on sodium water glass and sodium polyacrylate with a mass ratio of 1:2, 1:1 and 2:1. For this purpose, two types of rheological tests were used, i.e., oscillation measurements at a constant frequency and vibration amplitude (1 Hz and 0.3%), as well as creep tests at a constant shear stress of 10 Pa. Based on the obtained test results, it was found that all analysed samples can be classified as viscoelastic bodies with a significant predominance of elastic properties, as their phase shift angle δ was much lower than 45°. The properties closest to perfectly elastic were demonstrated by hydrogel samples with a weight ratio of sodium water glass to sodium acrylate of 1:2. The results of the creep tests supplemented this information. It was found that with the increasing content of sodium water glass and polyacrylamide, the degree of sample deformation increased during loading. That is, the increasing weight content of water glass and acrylamide increases the proportion of retarded (viscous) elasticity at the expense of undelayed elasticity.

15

Problems of steady vibrations in the coupled linear theory of double-porosity viscoelastic materials

Svanadze M. M.

Archives of Mechanics

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2021

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Vol. 73, nr 4

365--390

EN

In the present paper the coupled linear theory of double-porosity viscoelastic materials is considered and the basic boundary value problems (BVPs) of steady vibrations are investigated. Indeed, in the beginning, the systems of equations of motion and steady vibrations are presented. Then, Green’s identities are established and the uniqueness theorems for classical solutions of the BVPs of steady vibrations are proved. The fundamental solution of the system of steady vibration equations is constructed and the basic properties of the potentials (surface and volume) are given. Finally, the existence theorems for classical solutions of the above mentioned BVPs are proved by using the potential method (the boundary integral equations method) and the theory of singular integral equations.

16

Stress relaxation of porcine tendon under simulated biological environment: experiment and modeling

Łagan Sylwia D., Liber-Kneć Aneta

Acta of Bioengineering and Biomechanics

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2021

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Vol. 23, no. 1

59--68

EN

Purpose: The aim of the study was to investigate the viscoelastic response in the low and high physiological strain with the use of experimental and modeling approach. Methods: Viscoelastic response in the low, transition and high physiologic strain (3, 6 and 9%) with consideration of simulated biological environment (0.9% saline solution, 37 °C) was measured in relaxation tests. Preconditioning of tendons was considered in the testing protocol and the applied range of load was obtained from tensile testing. The quasi-linear viscoelasticity theory was used to fit experimental data to obtain constants (moduli and times of relaxation), which can be used for description of the viscoelastic behavior of tendons. The exponential non-linear elastic representation of the stress response in ramp strain was also estimated. Results: Differences between stress relaxation process can be seen between tendons stretched to the physiological strain range (3%) and exceeding this range (6 and 9%). The strains of 6% and 9% showed a similar stress relaxation trend displaying relatively rapid relaxation for the first 70 seconds, whereas the lowest strain of 3% displayed relatively slow relaxation. Conclusions: Results of the model fitting showed that the quasi-linear viscoelastic model gives the best fit in the range of low physiological strain level.

17

Viscoelasticity expression and extension of seismic dispersion and attenuation in porous media with multiple fracture sets

Zhang Jinwei, Ding Renwei, Zhao Lihong, Wang Deying

Acta Geophysica

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2020

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Vol. 68, no. 6

1679--1688

EN

Intensive studies have been conducted on fuid-related seismic dispersion and attenuation in saturated anisotropic media. Most of the studies are concentrated on the transversely isotropy media. However, the fractures distribution in subsurface reservoirs is often complex. When there are multiple fracture sets developing in a porous background, the signatures of seismic dispersion and attenuation remain unclear. In this paper, we propose a method to calculate the frequency-dependent stifness matrix of a porous medium with multiple fractures sets from a perspective of viscoelasticity. Due to the favorable approximation performance of the generalized standard linear solid model and Chapman model, we use a modifed form of generalized standard linear solid model to simulate the frequency-dependent stifness tensor of porous media with multiple fracture sets. The representation of the stifness tensor utilizes the modulus defect to denote the efects the fractures including fracture density and geometry. With the procedure of calculating the stifness tensors at low- and high-frequency limits, we can easily calculate the frequency-dependent stifness tensor for media with multiple fracture sets with arbitrary orientations and directions. We then analyze the efects of the fracture parameters on the viscoelasticity characteristics taking orthotropic medium as an example. The results can help to understand the viscoelasticity and the mesoscopic seismic attenuation associated with fractures and fuids and can provide a practical rock physics model when dealing with reservoirs with complex fracture patterns.

18

Fluid-fluid phononic crystal with elastic coat working in audible frequencies

Klimek Aleksandra

Vibrations in Physical Systems

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2019

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Vol. 30, nr 1

art. no. 2019145

EN

Phononic Crystals are receiving rising attention in the field of modern acoustic materials. PCs are artificial structures of periodically arranged scatterers. Such a structure enables creating a band gap in which, due to the Bragg diffraction phenomenon, vibrations are restrained or even forbidden. In this paperwork, the fluid-fluid PC is tested and simulated - the scatterers are constructed of water cylinders with an ethylene propylene diene monomer coat (EPDM - a hyperelastic rubber) and are embedded in air. The band gap is calculated to emerge in the audible range of frequency. Every simulation is performed with the use of the finite element method.

19

Investigation of the mechanism of moisture absorption in colloidal museum materials in order to improve the safety of exhibits and improve the hygiene of museum rooms

Dovhaliuk Volodymyr, Ujma Adam, Chovniuk Yurii

System Safety : Human - Technical Facility - Environment

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2019

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Vol. 1, nr 1

805--809

EN

Moisture sorption is one of the most important destruction factors for colloidal capillary-porous exhibits in museums (painting, clothing etc.), which is dependent on microclimate in museum rooms. The analysis of moisture sorption properties, kinetics of sorption and swelling of textile museum exhibits is carried out. Isotherms of desorption of viscose and woollen yarns and fabrics of different density (and threads of them) are identical. The analysis of the isotherms of fabrics of various fibre cloths and threads of them shows that they all are similar in shape to the curves and have the form typical for leading capillary-porous bodies. The hysteresis loop for almost all tissues is observed throughout the range of relative humidity of the medium. In this work, the characteristics of the hysteresis loop (area, limited by it, length of the loop), which are of informational significance in the description of the processes of isothermal sorption-desorption of the materials mentioned above, are indicated. The research results allow optimizing of microclimate control in museum rooms for elimination of destruction of exhibits, improve the safety of storage and ensure the hygiene of the air indoor environmental.

20

Electrohydrodynamic instability of a rotating Walters’ (model B’) fluid in a porous medium: Brinkman model

Rana G. C., Chand R., Sharma Veena

Mechanics and Mechanical Engineering

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2019

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Vol. 23, nr 1

138--143

EN

In this study, the instability of Walters’ (model B’) viscoelastic fluid in a Darcy-Brinkman-Boussinesq system heated from below saturating a porous medium in electrohydrodynamics is considered. By applying the linear stability analysis and normal modes, the dispersion relations accounting for the effect of Prandtl number, electric Rayleigh number, Darcy number, Brinkman-Darcy number, Taylor number and kinematic viscoelasticity parameter is derived. The effects of electric Rayleigh number, Darcy number, Brinkman-Darcy number and Taylor number on the onset of stationary convection have been investigated both analytically and graphically.