Wyniki wyszukiwania - BazTech

1

Fundamental solution of the steady oscillations equations in couple stress micropolar viscoelastic thermoelastic solid

Sahrawat Ravinder Kumar, Rani Sonam

International Journal of Applied Mechanics and Engineering

|

2025

|

Vol. 30, no. 2

140--160

EN

In this article, we study case of steady oscillations to solve the system of differential equations by using elementary functions in the theory of microploar couple stress viscoelastic solid . Four waves were discovered: two coupled longitudinal waves and two coupled transverse waves that propagate at various wave speeds. The penetration depth, specific loss, attenuation coefficients, and phase velocity - all of which have been computed numerically and plotted graphically for the LS and GL models - are affected by couple stresses and viscous parameters. Specific cases are created and contrasted with the earlier outcomes.

2

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

Khan Muhammad Sabeel, Sagheer Ayesha, Azeem Zarafshan

|

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

|

2025

|

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

Performance evaluation of nonlinear viscoelastic materials using finite element method

Sabri Laith Abed, Al-Tamimi Adnan Naji Jameel, Alshamma Fathi A., Mohammed M. N., Salloomi Kareem N., Abdullah Oday I.

International Journal of Applied Mechanics and Engineering

|

2024

|

Vol. 29, no. 1

142--158

EN

This research paper applies the finite element method as a methodology to evaluate the structural performance of nonlinear viscoelastic solids. A finite element algorithm was built and developed to simulate the mathematical nonlinear viscoelastic material behavior based on incremental constitutive equations. The derived Equation of the incremental constitutive included the complete strain and stress histories. The Schapery’s nonlinear viscoelastic material model was integrated within the displacement-based finite element environment to perform the analysis. A modified Newton-Raphson technique was used to solve the nonlinear part in the resultant equations. In this work, the deviatoric and volumetric strain–stress relations were decoupled, and the hereditary strains were updated at the end of each time increment. It is worth mentioning that the developed algorithm can be effectively employed for all the permissible values of Poisson’s ratio by using a selective integration procedure. The algorithm was tested for a number of applications, and the results were compared with some previously published experimental results. A small percentage error of (1%) was observed comparing the published experimental results. The developed algorithm can be considered a promising numerical tool that overcomes convergence issues, enhancing equilibrium with high-accuracy results.

5

Water hammer mitigation by internal rubber hose

Kubrak Michał

Archives of Civil Engineering

|

2024

|

Vol. 70, nr 1

275--288

EN

The aim of this research was to experimentally analyse the possibility of using a rubber hose placed inside a pipeline to mitigate the water hammer phenomenon. The experiments were conducted using a steel pipeline with an inner diameter of 53 mm and an EPDM rubber hose with a diameter of 6 mm. Hydraulic transients were induced by a rapid closure of the valve located at the downstream end of the pipeline system. In order to analyse the influence of steady-state flow conditions on the maximum pressure increase, measurements were carried out for different values of initial pressure and discharge. The experimental results indicate that placing a rubber hose inside a pipeline can substantially attenuate valve-induced pressure oscillations. It was observed that the initial pressure has a significant influence on the capacity of the rubber hose to dampen the water hammer phenomenon. Comparative numerical calculations were performed using the Brunone–Vitkovský instant acceleration-based model of unsteady friction. It was demonstrated that this approach does not allow satisfactory reproduction of the observed pressure oscillations due to the viscoelastic properties of the EPDM hose used in the tests.

PL

Celem przeprowadzonych badan była eksperymentalna analiza możliwości zastosowania węza gumowego umieszczonego wewnątrz rurociągu do łagodzenia zjawiska uderzenia hydraulicznego. Pomiary przeprowadzono wykorzystując stalowy rurociąg o średnicy wewnętrznej 53 mm i długości 48.5 m oraz wąż gumowy EPDM o średnicy 6 mm ułożony na całej długości rurociągu. Uderzenia hydrauliczne inicjowane były poprzez gwałtowne i całkowite zamknięcie zaworu znajdującego się na końcu układu. W celu przeanalizowania wpływu parametrów przepływów panujących w rurociągu w ruchu ustalonym na maksymalne przyrosty ciśnienia, pomiary przeprowadzono dla różnych wartości początkowego ciśnienia i natężenia przepływu. Wyniki eksperymentów wskazują, że umieszczenie węza gumowego w obszarze nieustalonego przepływu cieczy może skutecznie tłumic oscylacje ciśnienia podczas prostego, dodatniego uderzenia hydraulicznego. Zaobserwowano, że ciśnienie początkowe ma istotny wpływ na zdolność węza gumowego do tłumienia fal ciśnienia. Celem przeprowadzonych obliczeń numerycznych było sprawdzenie przydatności najczęściej wykorzystywanego w praktyce modelu tarcia nieustalonego (tzw. IAB Brunone–Vitkovský model) do symulowania analizowanego zjawiska. Wykazano, że podejście to nie pozwala na zadowalające odtworzenie obserwowanych oscylacji ciśnienia ze względu na lepkosprężyste właściwości użytego w badaniach węza EPDM.

6

Three‑dimensional piezo‑viscoelastic behavior of FGM cylindrical panel with piezoelectric layers under electro‑mechanical loads

Maslak A. Taheri, Alibeigloo A.

Archives of Civil and Mechanical Engineering

|

2024

|

Vol. 24, no. 1

art. no. e10, 2024

EN

In the framework of 3D elasticity theory, the static behavior of functionally graded viscoelastic cylindrical panels with piezoelectric layers under electro-mechanical loads is investigated. The viscoelastic material is modeled using Boltzmann's integral model, and its Poisson's ratio is constant, and for its time-dependent Young’s modulus, spatially, the power distribution in the radial direction is considered. Modulus time changes are also expressed using the Prony series. For simply supported edges, the state space method and Fourier expansion, and for other boundary conditions, the semi-analytical approach by the state space differential quadrature method (DQM) are used. Equations of motion are solved in the Laplace domain and by the Laplace inverse technique, results are transferred back to the time domain numerically. Also, the results of this research have been validated with other similar research. Finally, the effect of different parameters such as the type of supports, the relaxation time constant, thickness of the piezoelectric layer, and other important parameters on the static response of the panel have been investigated. Results demonstrate that if the ratio of the total layer thickness to the piezoelectric thickness exceeds a specified value, the effect of the thickness of the piezoelectric layer on mechanical behavior can be disregarded. Furthermore, when relaxation time constant increases, the amount of stress remains constant for a constant thickness and equals the amount of stress in the elastic panel. However, the amount of displacement decreases.

7

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

Guan Ling, Liu Xiaolin, Liu Xinyuan

Archives of Civil Engineering

|

2023

|

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.

8

Rheological properties of elastic-visco-plastic liquid

Dadash-Zade Mirza A., Aliyev Inglab N.

Nafta-Gaz

|

2022

|

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.

9

General decay for a nonlinear pseudo-parabolic equation with viscoelastic term

Vu Ngo Tran, Dung Dao Bao, Dung Huynh Thi Hoang

Demonstratio Mathematica

|

2022

|

Vol. 55, nr 1

737--751

EN

This work is concerned with a multi-dimensional viscoelastic pseudo-parabolic equation with critical Sobolev exponent. First, with some suitable conditions, we prove that the weak solution exists globally. Next, we show that the stability of the system holds for a much larger class of kernels than the ones considered in previous literature. More precisely, we consider the kernel g:[0,∞)⟶(0,∞) satisfying g′(t)⩽−ξ(t)G(g(t)) , where ξ and G are functions satisfying some specific properties.

10

Forced and free vibrational analysis of viscoelastic nanotubes conveying fluid subjected to moving load in hygro-thermo-magnetic environments with surface effects

Sarparast Hoda, Alibeigloo Akbar, Borjalilou Vahid, Koochakianfard Omid

Archives of Civil and Mechanical Engineering

|

2022

|

Vol. 22, no. 4

art. no. e172, 2022

EN

Forced and free vibrational analyses of viscoelastic nanotubes containing fluid under a moving load in complex environments incorporating surface effects are conducted based on the nonlocal strain gradient theory and the Rayleigh beam model. To model the internal nanoflow, the slip boundary condition is employed. Adopting the Galerkin discretization approach, the reduced-order dynamic model of the system is acquired. Analytical and numerical methods are exploited to determine the dynamic response of the system. The impacts of geometry, scale parameter ratio, Knudsen number, fluid velocity, rotary inertia parameter, viscoelastic parameter, surface residual stress, surface elastic modulus, and hygro-thermo-magnetic environments on the dynamic magnification factor, critical moving load speed, cancellation, and maximum free vibration of the system are evaluated. The results indicate that the effects of the viscoelastic parameter on the dynamic behavior of the system differ significantly from those of other parameters. It is indicated that the dynamic magnification factor and critical moving load speed are enhanced by increasing the surface residual stress and the surface elastic modulus. The model and results of the current investigation can serve as a comprehensive benchmark for the optimum design of nanoflow sensors and targeted drug delivery systems.

11

Wykorzystanie reologii oscylacyjnej do określenia parametrów mechanicznych hydrożeli krzemianowo-polimerowych

Słupecki Szymon, Mastalska-Popławska Joanna, Izak Piotr

Materiały Ceramiczne

|

2021

|

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.

12

Dynamic vibration extinguished on a viscously elastic base

Ishmamatov M., Kulmuratov N., Khalilov S., Akhmedov N.

International Journal of Applied Mechanics and Engineering

|

2021

|

Vol. 26, no. 2

1--10

EN

The aim of the work is to develop algorithms and a set of programs for studying the dynamic characteristics of viscoelastic thin plates on a deformable base on which it is installed with several dynamic dampers. The theory of thin plates is used to obtain the equation of motion for the plate. The relationship between the efforts and the stirred plate obeys in the hereditary Boltzmann Voltaire integral. With this, a system of integro-differential equations is obtained which is solved by the method of complex amplitudes. As a result, a transcendental algebraic equation was obtained to determine the resonance frequencies, which is solved numerically by the Muller method. To determine the displacement of the point of the plate with periodic oscillations of the base of the plate, a linear inhomogeneous algebraic equation was obtained, which is solved by the Gauss method. The amplitude - frequency response of the midpoint of the plate is constructed with and without regard to the viscosity of the deformed element. The dependence of the stiffness of a deformed element on the frequency of external action is obtained to ensure optimal damping of vibrational vibrations of the plate.

13

Analytical study of the damping vibration behavior of the metal foam nanocomposite plates reinforced with graphene oxide powders in thermal environments

Zhang Chunwei, Wang Limin, Eyvazian Arameh, Khan Afrasyab, Sebaey Tamer A., Farouk Naeim

Archives of Civil and Mechanical Engineering

|

2021

|

Vol. 21, no. 4

100--122

EN

This article performs an analytical study on the damping vibration behavior of metal foam nanocomposite plate reinforced with graphene oxide powders (GOPs) in thermal environment. The GOPs are dispersed through the thickness of the structure according to three functionally graded (FG) and one uniform distribution patterns. The Halpin–Tsai micromechanical model is chosen for estimating the effective material properties of the structure having GOPs as reinforcement phase. Also, different porosity types are taken into account for the metal foam matrix. The plate is resting on a three-parameter viscoelastic medium containing Winkler and Pasternak layers in combination with viscous dampers which can dissipate the oscillation of the structure in some special cases. The Governing differential equations are derived via Hamilton’s principle on the basis of refined higher order shear deformation theory and then solved with employing Galerkin solution method to obtain the natural frequencies of the proposed structure. Moreover, various boundary conditions (B.Cs) including simply supported, fully clamped and different combinations of these B.Cs are considered in this study. The influences and confrontation of different significant parameters such as GOPs’ weight fraction, foundation parameters, aspect and side-to-thickness ratios, porosity coefficients, thermal environment, and FG patterns are investigated through various graphical and numerical results. Our findings declare that the dynamic behavior of the graphene oxide powder reinforced metal foam (GOPRMF) plate remarkably depends on these parameters.

14

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

Łagan Sylwia D., Liber-Kneć Aneta

Acta of Bioengineering and Biomechanics

|

2021

|

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.

15

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

|

2020

|

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.

16

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

Klimek Aleksandra

Vibrations in Physical Systems

|

2019

|

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.

17

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

|

2019

|

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.

18

Decay rates for a coupled quasilinear system of nonlinear viscoelastic equations

Mustafa Muhammad I., Kafini Mohammad

Journal of Applied Analysis

|

2019

|

Vol. 25, nr 1

97--110

EN

In this paper, we consider a nonlinear quasilinear system of two coupled viscoelastic equations and investigate the asymptotic behavior of this system. We establish an explicit and general formula for the energy decay rates. Our result allows a wider class of relaxation functions, which improves earlier results existing in the literature.

19

Impact of carrageenan addition on rheological characterisation of some hydrocolloid aqueous solutions during long-lasting agitating with rotational speed changes

Neupauer Krzysztof, Kabziński Maciej

Chemical and Process Engineering

|

2019

|

Vol. 40, nr 4

351–-360

EN

The paper presents the impact of carrageenan addition on rheological characterisation of some hydrocolloid aqueous solutions during stirring with rotational speed changes. Carboxymethyl cellulose, guar gum and xanthan gum were used. Measurements were conducted in a vessel equipped with an anchor stirrer under rotational speed increase and decrease conditions, equivalent to a hysteresis loop rheological test. Rheological parameters were calculated using the power-law equation. It was found that a carrageenan addition generally causes a reduction of liquid apparent viscosity and time-dependent rheological behaviour intensification, with some exceptions.

20

Forced response of plate with viscoelastic auxetic dampers

Stręk T.

Vibrations in Physical Systems

|

2018

|

Vol. 29

art. no. 2018003

EN

The example studies a forced response of plate with viscoelastic auxetic damper located at the free end of the plate. Damping elements consist of the cover layer and layer of viscoelastic material with positive or negative Poisson's ratio. Viscoelastic materials are often used for reduction of vibration (seismic or wind induced vibrations in building structures or other structures). The common feature is that the frequency of the forced vibrations is low. Calculations are made using finite element method with Comsol Multiphysics software.