Electrorheological Research Articles

Electrorheological Response Behavior of PANI@MoS2 Core–Shell Nanocomposites

Electrorheological (ER) fluid, as an intelligent material, is a kind of suspension composed of polarized micro‐ and/or nanoparticles dispersed into insulating oil. In recent years, molybdenum disulfide (MoS2), as the hottest 2D material, has provided a new strategy to develop the high‐performance ER materials. 2D‐based ER composites can provide large surface to enhance the polarization. But the MoS2 ER material has many disadvantages such as low polarization strength and high electrical conductivity. To make up these defects, polyaniline (PANI) is used to combine with lamellar MoS2. Herein, PANI and MoS2 hybrid composite nanoparticles with special morphology are prepared by two‐step method. The coating material has special morphology, high interfacial polarization, specific surface area, and low density. The optimum reaction ratio is obtained by adjusting the proportion of MoS2 and PANI. When the proportion of PANI and MoS2 is 4:1, the material performance is best, in which the shear stresses can reach 150 Pa. In a word, it is proved that the material is an excellent electrorheological material.

Enhanced Electrorheological Polishing Efficiency of Alumina-Doped Titanium Dioxide Particles.

Electrorheological (ER) polishing is a novel polishing technology having flexible and tunable characteristics. At present, ER polishing uses ER particles to drive abrasive particles to polish the material surface. Under the action of high-speed centrifugation, the abrasive particles are easily separated from ER particles due to their significantly different ER effect, and this can easily cause the degradation of polishing ability. In this work, alumina-doped titanium dioxide ER polishing particles were developed via a sol-gel method. As a classical abrasive, alumina has higher hardness and can improve the ER effect of titanium dioxide by doping. Thus, alumina-doped titanium dioxide particles simultaneously possess high ER effect and high hardness. No phase separation appears in the polishing process and the result shows that alumina-doped titanium dioxide has a good polishing efficiency for materials with Mohs hardness of 3 and below.

Enhanced electro-responsive electrorheological efficiency of polyethylene oxide-intercalated montmorillonite nanocomposite suspension

Polyethylene oxide (PEO)-salt complex is an important polymer electrolyte-based anhydrous electrorheological (ER) material. However, it is difficult to get PEO-based ER material in particle form owing to the low glass transition temperature. Cross-linking and copolymerization with other polymers are widely used ways to form polyether-salt complex with desired dimensions and stability. However, these ways are relatively complex, and the ionic conductivity of resulting products is also too high for ER application. In this paper, we report a simple way to form PEO-based nanocomposite ER particles by intercalation chemistry with montmorillonite (PEO-MMT) under the help of ethanol solvent. The structure and composition of samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry, and so on. An increase in basal d001-spacings demonstrates successful intercalation of PEO in MMT. The electro-responsive ER effect of PEO-MMT suspension under electric fields was studied. It demonstrated that PEO intercalation not only effectively solved the problem of difficult granulation of PEO ER material but also replaced the absorbed water in the interlayer of MMT and greatly limited the ionic conductivity of MMT. Under electric fields, the suspension of PEO-MMT nanocomposite was found to show significant ER effect, weak current density, and wide working temperature range. A significant interfacial polarization process was observed by dielectric spectra measurement, which can explain the significant ER effect of PEO-MMT nanocomposite.

Morphology-controlled stabilised polyaniline nanoparticles and their electrorheological properties

Nanoparticles and sub-microparticles of the conducting polymers polyaniline (PANI), polyanisidine (PoANIS) and their copolymers were synthesised, deprotonated and dispersed in viscous media in order to study the influence of their synthetic conditions and of steric stabilisers (cellulose-based materials) on the physical, chemical and morphological characteristics of the polymers. Electrorheological (ER) measurements were performed and related to the polymer properties. The polymer particles had various loadings of stabilisers, depending on the polymer/stabiliser interactions and the stabiliser concentration. When stabilised with hydroxyethylcellulose (HEC), the PANI particles contained traces of HEC, while PoANIS, less stabilised by the electron-rich HEC molecules, did not. Stabilised PANI-HEC synthesised at 0°C readily formed small fibres that, when deprotonated, displayed a large electrorheological response (yield stress ca. 800 Pa at 3.2 kV.mm−1). PoANIS prepared under the same conditions yielded a polydisperse cenospheric material with no ER activity.

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.

Effect of the electric field on the sound transmission loss of double-walled electro-rheological fluid sandwich plates with functionally graded carbon nanotube reinforced composite facesheets

Numerous studies have been conducted to examine the vibroacoustic characteristics of lightweight double-walled structures due to the anticipated applications of these structures in noise reduction engineering. In this study, third-order shear deformation theory (TSDT) is used to develop a theoretical model that predicts sound transmission loss (STL) across double-walled electro-rheological fluid (ERF) sandwich plates with functionally graded carbon nanotube reinforced composite (FG-CNTRC) facesheets. The extended rule of mixture is utilized to evaluate the properties of the FG-CNTRC material in the thickness. Depending on the four FG models, the CNT volume fraction varies. A sufficient displacement continuity condition is taken into account between layers. Furthermore, it should be noted that changing the electric field affects the pre-yield zone’s ERF features. The vibroacoustic equations are derived using Hamilton’s principle and solved utilizing weighted residual (Galerkin) technique considering simply supported and clamped boundary conditions. Several studies are done to compare the results of the suggested model with other results found in the literature. An extensive numerical study is conducted to examine the dependence of STL on several parameters, including electric field strength, volume percentage of the CNTs, CNTs distribution, depth of acoustic cavity.

The preparation and smart electrorheological behavior of MOF-Ti@PANI core-shell nanoparticles

In this paper, a kind of core–shell composite nanoparticles for electrorheological (ER) fluid was successfully prepared and showed good ER effect. The material possesses the high specific surface area and low density of metal organic frameworks (MOFs), and combines with the excellent dielectric properties of polyaniline (PANI). PANI precursors were prepared by a rapid mixing method, and then MOF-Ti (an MOF containing Ti) grew in situ on PANI under the solvothermal conditions. The MOF-Ti@PANI composite nanoparticles with core–shell structure were generated. These characteristics of PANI and MOF-Ti are conducive to stronger interfacial polarization of nanoparticles, which in turn leads to a good ER effect. The nanoparticle morphology as well as its ER and dielectric properties was modulated by using different amounts of PANI addition. The addition amount of PANI had a certain effect on the particle morphology, which was proved by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). We also determined particle size at the nanoscale in this process. The measured results of the X-ray powder diffractometer (XRD) are consistent with the characteristic peaks of MIL-125 (a kind of MOF-Ti). The internal chemical structure of the material and the chemical environment of the elements were analyzed using Fourier infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Finally, the ER and dielectric properties of the nanoparticles in ER Fluids were investigated using high-speed rotational rheometry and broadband dielectric spectroscopy. The analysis revealed that the MOF-Ti@PANI core–shell nanoparticles have good ER properties under proper coating. For the core–shell modified MOFs, it is expected to be a promising development direction in the field of ER materials.

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.

Formula omitted]-regularity for steady flows of electrorheological fluids in 2D

We prove interior C1,α-regularity of every weak solution and the existence of global C1,α-solutions for steady flows of electrorheological fluids with Dirichlet type boundary condition under 32<p(x)<∞ in 2D.

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.

Design Optimization of a Hydrodynamic Brake with an Electrorheological Fluid

This article describes the design optimization of a hydrodynamic brake with an electrorheological fluid. The design optimization is performed on the basis of mathematical model of the brake geometry and the brake’s electrical circuit. The parameters of the mathematical models are selected based on experimental tests of the prototype brake. Six different objective functions are minimized during the design optimization. The functions are created taking into consideration the following factors: the braking torque, brake weight, electric power absorbed by the brake, and the torque rise time. The assumed design variables are: the number of blades and the radii (inner and outer) of the brake’s working space. The optimization calculations are performed for two design variables intervals. The first interval is defined taking into consideration the accuracy of the mathematical model. The second, narrower interval is assumed for the tested prototypical brake. On the basis of the optimization calculation results, general guidelines are presented for the optimization of the hydrodynamic brakes with an ER fluid. In addition, the possibilities of optimizing the prototype brake are determined.

Variable stiffness and fast-response soft structures based on electrorheological fluids

A soft structure with continuously variable stiffness and fast response was designed. Varying the electric field strength (0 to 4.5 kV mm−1), the rate of stiffness variation is over 1500%. The response time to load change is within 65 ms.

On the partial boundary value condition basing on the diffusion coefficient

The paper follows with interest in a nonlinear parabolic equation coming from the electrorheological fluid ut = div(a(x)|?u|p(x)?2?u) + ?N i=1 ?bi(u, x, t)/ ?xi with a(x) being positive in ?. We study the well-posedness problem of the equation under the condition bi(?, x, t) = 0 on the partial boundary ?? \ ?1 for every i = 1, 2,...,N, where ?1 = {x ? ?? : a(x) &gt; 0}. The stability of the weak solutions is obtained only basing on a partial boundary value condition u(x, t) = 0, (x, t) ? ?1 ? (0, T).

Existence of entropy solutions for some quasilinear anisotropic elliptic unilateral problems with variable exponents

In this paper, we shall be concerned with the study of the following quasilinear anisotropic elliptic Dirichlet problems of the type \begin{document}$\begin{equation} -\mbox{div }\;a(x,u,\nabla u) = f -\mbox{div } F \qquad \mbox{in}\quad \Omega,\quad\quad\quad\quad\quad(1) \end{equation}$ \end{document} where $ f\in L^{1}(\Omega) $ and $ F \in \prod_{i = 1}^{N} L^{p'_{i}(\cdot)}(\Omega), $ and $ a_{i}(x,u,\xi) $ are Carathéodory functions from $ \Omega \times I\!\!R \times I\!\!R^{N} $ into $ I\!\!R $, which satisfy assumptions of growth, coercivity and strict monotonicity. We prove the existence of entropy solutions for the quasilinear elliptic equation associated to the unilateral problem by relying on the penalization method, in the anisotropic variable exponent Sobolev spaces. Our approach is also based on the techniques of monotone operators in Banach spaces, the existence of weak solutions, and some approximations methods. The problems of the type $ (1) $ are very interesting from the purely mathematical point of view. On the other hand, such equations $ (1) $ appear in different contexts, in particular, the mathematical description of motions of the non-newtonien fluids; we quote for instance the electro-rheological fluids; the deformation of membrane constrained by an obstacle, the image processing and other various physical applications.

On the absence of collective motion in a bulk suspension of spontaneously rotating dielectric particles.

A suspension of dielectric particles rotating spontaneously when subjected to a DC electric field in two dimensions next to a no-slip electrode has proven to be an ideal model for active matter [Bricard et al., Nature, 2013, 503, 95-98]. In this system, an electrohydrodynamic (EHD) instability called Quincke rotation was exploited to create self-propelling particles which aligned with each other due to EHD interactions, giving rise to collective motion on large length scales. It is natural to question whether a suspension of such particles in three dimensions will also display collective motion and spontaneously flow like bacterial suspensions do. Using molecular dynamics type simulations, we show that dielectrophoretic forces responsible for chaining in the direction of the applied electric field in conventional electrorheological fluids and the counter-rotation of neighboring particles in these chains prevent collective motion in suspensions undergoing spontaneous particle rotations. Our simulations discover that the fundamental microstructural unit of a suspension under Quincke rotation is a pair of counter-rotating spheres aligned in the direction of the electric field. We perform a linear stability analysis that explains this observation.

DURABILITY INVESTIGATION OF A DISC-TYPE CLUTCH WITH ELECTRORHEOLOGICAL FLUID

The article concerns experimental research on the durability of a viscotic disc-type clutch with an electrorheological fluid. Viscotic clutches are currently used in the power transmission of multiple machines. The development of the viscotic clutch design is possible due to the use of working fluids with electrorheological properties, which renders it possible to control the drivetrain with the use of an electric current. The durability of the clutches with electrorheological fluid is important in determining the possibility of industrial use. On the basis of bench tests of a viscotic disc clutch, the article presents considerations regarding the operating factors of the clutch. These factors considerably impact the durability of the clutch and its components, including the working fluid.

Hydrocarbon Lubricating Oils with Admixture of Ionic Liquid as Electrorheological Medium

The article describes the results of experimental studies of electrorheological (ER) properties of lubricating oils containing an admixture of an ionic liquid as the electrically active ingredient. The novelty of these studies consists of the use of selected ionic liquids as additives to hydrocarbon oils in order to obtain quasi-homogenous mixtures with electrorheological properties. So far, such studies have not been carried out. Basic research, which consisted in determining the rheological characteristics in the presence of an external direct electric field, was carried out on a specially designed and built stand, which used a modified Brookfield DV-III Ultra viscometer. The conducted research showed that the produced mixtures generated the ER effect in the presence of a direct electric field with an intensity of up to 0.2 kV·mm-1. The tested mixtures showed different electrorheological characteristics. The research was also carried out in the so-called dielectric spectroscopy using the Hewlett Packard HP4192A impedance analyzer. The mechanism of generating and decaying the ER effect was diagnosed by in situ microscopy using the Nikon Eclipse LV100D optical microscope. It was found that the course of the τ = f(γ˙) characteristic of a mixture of hydrocarbon oil with a small admixture of an ionic liquid is mainly influenced by the so-called dielectric properties of the electrically active component, or rather their change as a function of the applied BIAS (DC) voltage. At the same time, the obtained results of the research gave grounds to state that the electrorheological characteristics also depend on many physicochemical properties of the mixture components and on the differentiation of their values e.g., from the difference in viscosity of the insulating base oil and the added ionic liquid, and also from the difference in the value of the surface tension of the base oil and the added ionic liquid. In these studies, it was found that the surface tension of the CJ001 ionic liquid at 25 °C was 26.032 mN·m-1. The surface tension of CJ008 was 28.099 mN·m-1 and that of PAO-6 oil was almost the same, i.e., 27.523 mN·m-1. The first mixture (GP1 + CJ001) showed Bigham characteristics and the second (PAO6 + CJ008) Newtonian, in the second mixture, the viscosity difference of the components was two times lower than in the first one (GP1-12.61 mPa·s, CJ001-552.42 mPa·s and PAO6-47.35 mPa·s, CJ008-327.24 mPa·s).

Electrorheological and dielectric analysis of self-crosslinked poly(ionic liquid)s with different flexible chain spacer

Three kinds of self-crosslinked poly(ionic liquid)s (S-PILs) with different flexible chain spacers, namely P[B2V][TFSI], P[C8DVIM][TFSI] and P[TEGDVIM][TFSI], were prepared. The influence of flexible chain spacer on electrorheological (ER) effect of S-PIL suspension in silicone oil under electric fields was studied by rheological method and dielectric spectroscopy. It is found that as the flexibility of chain spacer increases, the ER effect increases. However, the dielectric spectrum shows that the variation of ER effect is not completely consistent with that of interfacial polarization but is related to the competition between interfacial polarization induced by ion motion and electrode polarization formed by ion leakage. By combining wide-angle X-ray scattering spectra and ion activation energy analysis, we further clarify that the reason for the inconsistence of dielectric property and ER effect is not only related to the flexibility of chain spacer but also related to the interaction between oxygen on chain spacer and counter-anions in the S-PILs. The result provides an insight for the molecular design of S-PIL ER materials.

Self‐powered In‐Phase Sensing and Regulating Mechanical System Enabled by Nanogenerator and Electrorheological Fluid

AbstractMechanical system with adjustable stiffness and damping (ASAD) shows great potential in vibration suppression of aircraft, vehicle, precise instrument, etc. However, current ASAD systems consist of power, sensing, and controlling components, which bring huge challenges of system reliability and integrability, and critically limit its application diversity. Herein, we proposed the first strategy for regulating ASAD system that is system simplification, self‐powered and no‐delay by deeply coupling triboelectric nanogenerator (TENG) and electrorheological fluid (ERF). Under the time‐varying mechanical triggering, the local and time correlated output of TENG instantaneously applied on the ERF regulates the entire mechanical system dynamically and “in‐phase”. As an illustration, the resonance of a cantilever system is effectively suppressed naturally without complicated controlling strategy, and the vibration isolating efficiency reaches up to 85.2%. Finally, a mechanical transmission system is demonstrated utilizing a rotary TENG and ERF, excellent soft‐start performance is enabled by this self‐regulating ASAD strategy. This work may provide the opening arsenal of methodologies used in self‐powered and self‐regulating mechanical systems.

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.