Electrorheological Fluid Core Research Articles

Smart hybrid active/semi-active distributed structural acoustic control of thin- and thick-walled piezo-sandwich bimorph spherical shell cloaks

A novel three dimensional underwater smart piezo-sandwich spherical shell cloak is designed and analyzed based on the hybrid active/semi-active distributed structural acoustic control strategy. The sandwich configuration consists of series- or parallel-connected piezoelectric (PZT) bimorph actuator skin layers collocated with a semi-active electro-rheological fluid (ERF) core layer. Two separate coupled elasto-acoustic formulations are systematically developed. The first model is based on the variational principle of structural mechanics and the approximate Kirchhoff-Love thin shell theory while the standard sliding mode control (SMC) scheme is utilized to activate the acoustic scattering extinction capability of the hybrid structure. The second model is built on the exact linear theory of 3D piezoelasticity and the classical state-space transfer matrix approach along with the active damping control (ADC) strategy. Extensive numerical simulations reveal that the best broadband backscattering cancellation performance can effectively be achieved with the smart hybrid active/semi-active bimorph piezo-sandwich spherical shell cloak operating in parallel connection. To quantify the overall cloaking performance of the proposed design, the percentage error (%Err) of the external cloaked field relative to the background incident pressure field is calculated at selected dominant structural resonance frequencies within eight designated frequency bands (regions I to VIII). The remarkable (near-perfect) cloaking performance of the parallel-connected thick-walled hybrid bimorph piezo-sandwich shell (25%shellcloak) is demonstrated in the intermediate to high frequency regions (i.e., below 1.5% error in regions I, and III to VIII). This excellent invisibility performance is somewhat degraded in a narrow low frequency band (i.e., up to 8% error in region II) which is primarily linked to the elasto-acoustic resonances due to the coherent coupling of various types of highly interacting fluid- and shell-borne peripheral waves. On the other hand, the superior cloaking performance of the parallel-connected thin-walled hybrid bimorph piezo-sandwich shell (7%shellcloak) is observed predominantly in the low frequency range (i.e., below 1.5% error in regions I and II), while this exceptional performance is gradually degraded as the incident wave frequency is increased (i.e., up to 6.5% error in regions III to VIII), where partial or directional cancellation of the scattered field mostly occurs. Also, some important practical issues and limitations regarding the experimental implementation of proposed hybrid active/semi-active acoustic cloaking device are briefly discussed.

Stability/instability of electrorheological nano pipes used in braking nanosystems by the machine learning method

ABSTRACT Electro-rheological fluids change their viscosity properties due to their application in an electrical field. This property could be acquired and maintained by accurately controlling the external electrical field. Besides brake systems, such electro-rheological (ER) fluids could be utilized in small-scale damping systems. In the present study, for the first time, the effects of using an electrical field in improving the dynamic stability of nanostructure containing ER fluids are presented. In this regard, a cylindrical sandwich structure, with an inner and outer layer composed of two-directional functionally graded (2D-FG) material and ER fluid core, is considered. Employing energy methods and modified power law the equations of motion of the structure are derived. Between FG and ER layers’ compatibility conditions are imposed in terms of displacement and strains. Moreover, to bypass computational complications, the inputs and outputs are utilized for training a deep neural network (DNN). In this way, the inputs and outputs are related to each other through the regression method without numerically solving the equations of motion all over again. Finally, the effects of different parameters on the frequency and loss factor characteristics of the current nanostructure will be presented.

Nonlinear vibration of electro-rheological sandwich plates, coupled to quiescent fluid

The current paper aims to study the free vibration analysis of a sandwich plate in contact with quiescent fluid. The structure is made of an electro-rheological (ER) fluid core, and two laminated composite skins. The fluid is ideal, interacting partially with a plate, and fluid potential velocity is derived, satisfying continuity equation. Higher-order shear deformable theory is employed for the displacement field, and nonlinear Von-Karman strains are taken into account. After calculating the structural strain energy and kinetic energies of the fluid and plate, Galerkin approach and harmonic balance method are adopted to obtain natural frequencies of the system. Next, the accuracy and reliability of the developed model are confirmed, and then a detailed parametric study is conducted to examine the effects of different parameters such as geometrical dimensions of plate, fluid parameters and electric field strength on vibrational characteristics of the structure. The novelty of the presented model focuses on the nonlinear analysis of an ER sandwich panel coupled to ideal fluid, and the obtained results can guide the future design of composite ER panels.

Dynamic and electrical damping of deep spherical sandwich shells with electrorheological fluid core and FG-GPLRC skins

This paper focuses on the vibration and damping of a deep spherical sandwich shell with a new composition. The shell is made with a core of electrorheological (ER) fluid and skins made of a nanocomposite material with graphene platelets (GPL) to make them stronger. The displacement field is governed by first-order sandwich theory. The properties of the skins, ER fluid, and sealants are dependent on the position, applied electric field, and frequency, respectively. Combining the strain-displacement relation based on the deep shells and linear constitutive laws based on the Hooke and Kelvin-Voigt theories provides the governing motion equations of this structure. The highly coupled differential equations are solved by a semi-analytical solution. The analytical portion is a trigonometric expansion (TE) technique that solves the equations along the circumferential direction. The generalized differential quadrature (GDQ) method is employed as the numerical part to solve the remaining equations along the meridional path. After performing the convergence and verification studies, the frequencies and loss factors correlated to the first ten vibrational angular modes under the effect of various parameters are analyzed.

Vibration and damping analysis of sandwich electrorheological fluid deep arches with bi-directional FGM containers

In this project, for the first time, the dynamic features of a deep sandwich arch with an electrorheological fluid (ERF) core are evaluated. The retentive face sheets of this structure are composed of novel bi-directionally functionally graded materials (FGMs) according to a dual-index power law. The curved beam's displacement field is predicted by applying the sandwich theory, which takes into account shear deformations and rotating inertias for all layers. When calculating the equivalent features of FGM face layers, the rule of mixtures is utilized as a homogenization technique. The ERF core's constitutive law is found to be in the pre-yield zone by considering the magnitudes of the electric field applied. Employing Hamilton's principle, the dynamic equations in terms of displacement components are derived. The discrete version of these equations is achieved by the use of the Chebyshev collocation tool. Parametric investigations are carried out after analyzing the efficacy and precision of the used approach and formulation via the presentation of verification cases. In the parametric section, the contribution of each geometric and material characteristic, as well as different boundary conditions, on the system frequencies and related mode shapes and loss factors, will be explored.

Dynamic analysis of electrorheological fluid sandwich cylindrical shells with functionally graded face sheets using a semi-analytical approach

The present research is performed to calculate the natural frequencies, loss factors, and associated mode shapes of a sandwich cylinder with moderately thick functionally graded (FG) face sheets and an electrorheological (ER) fluid core. Each face sheet is assumed to be made of FG materials, and its displacement field is estimated based on the first-order shear deformation theory, like the ER constrained layer. A suitable displacement continuity condition is considered between layers. The ER fluid used in the central middle is analyzed in the pre-yield area and considered electric field dependent. Hamilton’s principle is used to acquire the motion equations related to each layer and appropriate boundary conditions. A computational code is implemented based on the combination of trigonometric expansion and the generalized differential quadrature (GDQ) methods to extract the complex eigenvalue problem for the vibration and damping of the assumed structure. After carrying out a comprehensive verification study, some novel numerical results are obtained. In the parametric study, the effects of the applied electric field, the FG power-law index, various boundary conditions, and structure geometry to control the natural frequencies and modal loss factors, as well as mode shapes, are investigated.

Comparison of the application of smart electrorheological and magnetorheological fluid cores to damp sandwich panels’ vibration behavior, based on a novel higher-order shear deformation theory

Background: Magnetorheological and electrorheological materials show variations in their rheological properties when subjected to magnetic and electric fields. We analyzed the vibration control behavior of a sandwich panel with elastic face sheets and an electrorheological or magnetorheological fluid core, using an improved higher-order theory. The theory was applied to the analysis of the structure's components as a combination of exponential, trigonometric, and polynomial functions. The core's flexibility was analyzed based on Frostig's second model, which has attracted material science researchers’ attention. Methods: Using the new theory, we analyzed the transverse shear and rotary inertia effects of the cover sheets. The governing equations and boundary conditions were derived by Hamilton's principle. The natural frequencies and loss factors were derived by solving the eigenvalue problem. The effects of changing the geometric parameters, the thickness of the magnetorheological or electrorheological layer, and thickness ratios on the vibration behavior of the panel were determined. Results: The panel's natural frequencies increased when the magnetic or electric field strength, and the panel's aspect ratio increased. It decreased when the core to panel thickness ratio increased. The magnetorheological material showed higher strength and lower sensitivity to external impurities than did the electrorheological material. Conclusions: We conclude that the magnetorheological materials minimize the structure's vibration at high-frequency operation, and the electrorheological materials are optimal for minimizing the structure's vibration at lower frequency operation. The findings of this study are useful to better understand the vibration behavior of sandwich panels with laminates under free vibration conditions.

Improved High-order Analysis of Linear Vibrations of a Thick Sandwich Panel With an Electro-rheological Core by Using Exponential Shear Deformation Theory

In In this paper, the behavior of free vibrations of the thick sandwich panel with multi-layer face sheets and an electrorheological (ER) fluid core using Exponential Shear Deformation Theory were investigated. For the first time, Exponential shear deformation theory is used for the face sheets while the Displacement field based on the second Frostig's model is used for the core. The governing equations and the boundary conditions are derived by Hamilton’s principle. Closed form solution is achieved using the Navier method and solving the eigenvalues. Primary attention is focused on the effects of electric field magnitude, geometric aspect ratio,and ER core layer thickness on the dynamic characteristics of the sandwich plate. The rheological property of an ER material, such as viscosity, plasticity, and elasticity may be changed when applying an electric field. When an electric field is applied, the damping of the system is more effective. The effects of the natural frequencies and loss factors on the dynamic behaviorof the sandwich plate are studied.the natural frequency of the sandwich plate increases and the modal loss factor decreases. With increasing the thickness of the ER layer, the natural frequencies of the sandwich plate are decreased.

Control of sound transmission into a hybrid double-wall sandwich cylindrical shell

A 3D analytical model is formulated for diffuse sound field transmission control through a smart hybrid double concentric sandwich circular cylindrical shell structure in presence of external and internal air gap mean flows. The multi-input multi-output sliding mode control is applied to enhance the sound transmission loss characteristics via direct control action of a uniform force piezoelectric actuator layer along with semi-active variation of the stiffness/damping characteristics of the electrorheological fluid core layer incorporated in a non-collocated configuration within the external or internal shell structure. Extensive numerical simulations examine the uncontrolled/controlled diffuse field sound transmission loss spectrums in a broad frequency range for single-wall and hybrid double-wall sandwich shells at selected external and air gap Mach numbers. The proposed smart hybrid active/semi-active double-wall configuration is demonstrated to provide satisfactory overall acoustic insulation control performance with much lower operative energy requirements. Limiting cases are considered, and validity of the formulation is verified against the available data.

Wave propagation analysis of electro-rheological fluid-filled sandwich composite beam

In this article, wave propagation of the sandwich composite beam with tunable electro-rheological (ER) fluid core is investigated. The sandwich composite beam is made of three layers consisting of the basic layer, ER fluid core, and the limiter layer. ER fluid core embedded withindoors the basic and limiter layers. The upper and lower layers are constructed of the elastic materials. Hamilton’s principle is utilized for deriving the governing equations of motion. Using an analytical solution, the wave frequency and the phase velocity can be gathered by solving eigenvalue problem. Moreover, the effect of different parameters such as electric field, core-to-top layer thickness ratio, and thickness of ER core is investigated on the wave dispersion characteristics.

Free and forced vibration of sandwich plates with electrorheological core and functionally graded face layers

The free and forced vibration of a sandwich plate with functionally graded face layers and electrorheological fluid core is presented in this article. Assuming classical thin plate theory for face sheets and first order shear theory for the core layer, the equations of motions are derived using Hamilton’s principle. The simply-supported boundary condition is considered for all edges and the generalized Fourier series are employed to represent the displacements of the sandwich plate. The natural frequencies and loss factors are obtained by solving the complex eigenvalue problem. The results of free and forced responses are compared and validated with the previous articles and effects of electric field, geometric aspect ratio, functionally graded component ratios and core layer thickness on the dynamic behavior of the sandwich plate are studied.

Active damping of sound transmission through an electrorheological fluid-actuated sandwich cylindrical shell

An exact model is proposed for sound transmission through a sandwich cylindrical shell of infinite extent that includes a tunable electrorheological fluid core, and is obliquely insonified by a plane progressive acoustic wave. The basic formulation utilizes Hamilton’s variational principle, the classical and first order shear deformation shell theories, the Kelvin–Voigt viscoelastic damping model (for the electrorheological fluid-core layer), and the wave equations for internal/external acoustic domains coupled by the proper fluid/structure compatibility relations. The Fourier–Bessel series expansions are used to arrange the governing (coupled) system equations in state-space form. The classical Sliding Mode Control law is then applied to semi-actively reduce sound transmission through the composite cylinder by smart variation of stiffness and damping characteristics of the electrorheological fluid-core actuator layer according to the control command. Numerical results present both the uncontrolled and controlled sound transmission loss spectra of the sandwich cylindrical shell at three angles of incidence for three distinct sets of material input parameters that represent the electric-field dependency of the complex shear modulus of the electrorheological fluid-core layer. The superior soundproof performance of electrorheological fluid-based sliding mode control system in avoiding the highly detrimental sound transmission loss dips occurring throughout the critical resonance and coincidence regions is demonstrated. Likewise, remarkable enhancements in the sound insulation characteristics of the electrorheological fluid-actuated structure utilizing the first or second electrorheological fluid material model are achieved within the stiffness-controlled region, especially at lower frequencies in near-grazing incidence situation. A number of limiting cases are introduced and validity of the formulation is confirmed by comparison with the available data.

Differential quadrature method for vibration analysis of electro-rheological sandwich plate with CNT reinforced nanocomposite facesheets subjected to electric field

In this study, free vibration analysis of smart sandwich plate rested on Winkler-Pasternak foundation is investigated. Sandwich plate is made of electro-rheological (ER) fluid core embedded within two nanocomposite layers which are included ZnO matrix and carbon nanotubes (CNTs) fiber. Due to electrical properties of core and nanocomposite facesheets, the external electric fields are applied to them, separately. The material properties of ER core are determined by Don and Yalcintas models. Also, Eshelby-Mori-Tanaka approach is used to obtain the material properties of nanocomposite facesheets. Hamilton’s principle is utilized to derive the governing equations of motion. Numerical characteristics of the differential quadrature method (DQM) are shown through solving selected ER sandwich plate with CCCC and SSSS boundary conditions, core to facesheets thickness ratios, volume fractions of CNTs, external voltage and Winkler-Pasternak foundation coefficients. The results obtained for ER sandwich plate show that DQM has very good accordance with results of finite element method available in literature. Also, it is observed that increasing the volume fraction of CNTs in facesheets leads to increase the stability of ER sandwich plate. These finding can be employed to design building smart structures and machines.

Design and dynamic modeling of electrorheological fluid-based variable-stiffness fin for robotic fish

Fish actively control their stiffness in different swimming conditions. Inspired by such an adaptive behavior, in this paper we study the design, prototyping, and dynamic modeling of compact, tunable-stiffness fins for robotic fish, where electrorheological (ER) fluid serves as the enabling element. A multi-layer composite fin with an ER fluid core is prototyped and utilized to investigate the influence of electrical field on its performance. Hamilton's principle is used to derive the dynamic equations of motion of the flexible fin, and Lighthill's large-amplitude elongated-body theory is adopted to estimate the hydrodynamic force when the fin undergoes base-actuated rotation. The dynamic equations are then discretized using the finite element method, to obtain an approximate numerical solution. Experiments are conducted on the prototyped flexible ER fluid-filled beam for parameter identification and validation of the proposed model, and for examining the effectiveness of electrically controlled stiffness tuning. In particular, it is found that the natural frequency is increased by almost 40% when the applied electric field changes from 0 to .

Elasto-acoustic response damping performance of a smart cavity-coupled electro-rheological fluid sandwich panel

The transient vibroacoustic response mitigation of a rectangular sandwich panel with an adaptive electro-rheological fluid core layer, and backed by a hard-walled reverberant rectangular parallelepiped acoustic enclosure, is investigated. The problem is analyzed in a multidisciplinary framework that involves the thin sandwich electro-rheological fluid-based plate model, the 3D wave equation for the acoustic enclosure domain, the first-order Kelvin–Voigt viscoelastic model for the electro-rheological fluid core material, the pertinent structure–fluid compatibility relation, and the inherently robust sliding mode control strategy. The generalized Fourier expansion method is utilized to set up the fully coupled system equations in the state–space domain, and the fourth-order Runge-Kutta time marching technique is then utilized to compute both uncontrolled and controlled coupled system responses in three basic external loading configurations. It is found that increasing the cavity depth has a substantial restraining effect on the overall sound pressure response levels, while the electro-rheological fluid-panel displacement response amplitudes experience only moderate reductions. Also, a purely passive electro-rheological fluid-based system is observed not to be very effective for vibroacoustic response suppression of the cavity-coupled structural system, while the overall success of the applied sliding mode control methodology in reasonable reduction of both panel displacement and sound pressure time response amplitudes is demonstrated. Furthermore, the control system authority with regard to the acoustic cavity pressure (panel displacement) is found to moderately (slightly) decrease as the cavity depth increases. Limiting cases are considered and accuracy of the suggested analytical model is checked against the output of an FEM package as well as with the accessible literature results. Moreover, the main components of a prospective experimental platform for verifying the performance of proposed vibroacoustic control system are briefly described.

Aeroelastic analysis and active flutter suppression of an electro-rheological sandwich cylindrical panel under yawed supersonic flow

Supersonic flutter control of a three-layered sandwich curved panel of rectangular plan form with an adaptive electro-rheological fluid (ERF) core layer is investigated. The panel is excited by an arbitrary transient transverse load along with an arbitrary airflow yaw angle. The problem formulation is based on Kirchhoff–Love thin shell theory, the first order Kelvin–Voigt viscoelastic material model, and the linear quasi-steady Krumhaar's modified supersonic piston theory that accounts for both the panel curvature and flow yaw angle. The classical Hamilton's principle and the Galerkin method are used to set up the equations of motion which are then put in the state-space form. The effects of applied electric field, panel aspect ratio, panel shallowness angle, and airflow direction on the critical free stream static pressure are studied. Also, the aeroelastic response of the cylindrical panel excited by an impulsive central point load is calculated using the Runge–Kutta time integration scheme. Subsequently, a Sliding Mode Control (SMC) methodology is implemented to actively attenuate the structural response in the supersonic flow regime. Numerical simulations establish the effectiveness of the applied control configuration in successful suppression of the structural oscillations. The validity of results is demonstrated by rigorous comparisons with the existing data.

Vibroacoustic Response of an Annular Sandwich Electrorheological Disc

The steady-state sound radiation characteristics of a rigidly-baffled clamped-free sandwich annular disc with a tunable electrorheological fluid (ERF) core is studied. Hamilton's principle is employed to derive the governing equations of motion for the composite plate along with the associated boundary conditions in general form. The classical Galerkin procedure is subsequently utilized to reduce the structural problem into a linear system of algebraic equations for the unknown displacement coefficients. A modal summation approach based on Rayleigh integral formula along with the proper integral representation of the cylindrical Bessel functions are used to arrive at a useful single integral relation for the far-field modal radiated sound pressure and subsequently determine the radiation power and efficiency. Numerical results reveal the imperative influence of the applied electric field strength (0–3.5kV/mm) on controlling acoustic radiation from the adaptive panel in a wide frequency range. In particular, an effort is made to find the optimal electric field which yields improved sound radiation characteristics for each excitation frequency. Limiting cases are considered and good agreements with the calculations made by using a commercial finite element package as well as with the solutions available in the literature are obtained.

Axisymmetric dynamic instability of polar orthotropic sandwich annular plate with ER damping treatment

The axisymmetric dynamic instability of polar orthotropic sandwich annular plate combined with electrorheological (ER) fluid core layer and constraining layer are studied in this paper. And, the ER core layer and constraining layer are used to improve the stability of the annular plate system. The boundaries of instability regions for the polar orthotropic sandwich annular plate system are obtained by discrete layer annular finite element and the harmonic balance method. The rheological property of an electrorheological material, such as viscosity, plasticity, and elasticity can be controlled by applying different electric field strength. Thus, the damping characteristics of the sandwich system are more effective when the electric field is applied on the sandwich structure. Additionally, variations of the instability regions for the polar orthotropic sandwich annular plate with different applying electric field strength, thickness of ER layer and some designed parameters are investigated and discussed in this study.

SUPERSONIC FLUTTER CONTROL OF AN ELECTRORHEOLOGICAL FLUID-BASED SMART CIRCULAR CYLINDRICAL SHELL

In this paper, active flutter suppression of a simply supported circular sandwich cylindrical shell with a tunable electrorheological fluid (ERF) core, under axial supersonic gas flow, is studied. The structural analysis is based on the classical thin shell theory, the ERF core is modeled as a first-order Kelvin–Voigt material, and the Krumhaar's modified supersonic piston theory is utilized to model the aerodynamic loading. Hamilton's principle is used to formulate the dynamic equations of motion together with the relevant boundary conditions. The generalized Fourier expansions in the circumferential and axial directions in conjunction with the classical Galerkin method are employed to set up the governing equations in the state-space domain. The critical free stream static pressures at which unstable oscillations arise are calculated for selected applied electric field strengths and cylinder length ratios. The Runge–Kutta time integration algorithm is used to determine the open-loop aeroelastic response of the system in two basic loading configurations, namely, a concentrated impulse point load and a sonic boom line load. Subsequently, a sliding mode control (SMC) strategy is adopted to actively suppress the closed loop system dynamic response in supersonic flight condition. Simulation results demonstrate performance and effectiveness of the adopted ERF-based SMC scheme. Limiting cases are considered and good agreements with the data available in the literature are obtained.

Structural modeling, vibration analysis and optimal viscoelastic layer characterization of adaptive sandwich beams with electrorheological fluid core

This paper deals with the vibration analysis of adaptive sandwich beams with electrorheological fluid (ERF) core. In this study, Timoshenko beam theory has been employed to derive the governing equations of motion of variable structure sandwich beams. A consistent procedure is proposed for optimal characterization of the viscoelastic core. Herein, the experimental ASTM E756 method is combined with the computational particle swarm optimization (PSO) to estimate and update the complex shear modulus of the viscoelastic layer. The effects of thickness of the layers and applied electric fields on natural frequencies and modal loss factors are investigated.