scholarly journals Experimental and numerical study on surface roughness of magnetorheological elastomer for controllable friction

Friction ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 917-929 ◽  
Author(s):  
Rui Li ◽  
Xi Li ◽  
Yuanyuan Li ◽  
Ping-an Yang ◽  
Jiushan Liu
Keyword(s):  
Magnetic Field ◽  
Surface Roughness ◽  
Surface Morphology ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Rubber Matrix ◽  
Magnetorheological Elastomer ◽  
Particle Volume ◽  
Simulation Results ◽  
The Magnetic Field

Abstract Magnetorheological elastomer (MRE) is a type of smart material of which mechanical and electrical properties can be reversibly controlled by the magnetic field. In this study, the influence of the magnetic field on the surface roughness of MRE was studied by the microscopic modeling method, and the influence of controllable characteristics of the MRE surface on its friction properties was analyzed by the macroscopic experimental method. First, on the basis of existing studies, an improved mesoscopic model based on magnetomechanical coupling analysis was proposed. The initial surface morphology of MRE was characterized by the W-M fractal function, and the change process of the surface microstructures of MRE, induced by the magnetic interaction between particles, was studied. Then, after analyzing the simulation results, it is found that with the increase in the magnetic field and decrease in the modulus of rubber matrix, the surface of MRE changes more significantly, and the best particle volume fraction is within 7.5%–9%. Furthermore, through experimental observation, it is found that the height of the convex peak on the surface of MRE decreases significantly with the action of the magnetic field, resulting in a reduction in the surface roughness. Consistent with the simulation results, a particle volume fraction of 10% corresponds to a maximum change of 14%. Finally, the macroscopic friction experiment results show that the friction coefficients of MREs with different particle volume fractions all decrease with the decrease in surface roughness under the magnetic field. When the particle volume fraction is 10%, the friction coefficient can decrease by 24.7% under a magnetic field of 400 mT, which is consistent with the trend of surface roughness changes. This shows that the change in surface morphology with the effect of the magnetic field is an important factor in the control of MRE friction properties by magnetic field.

scholarly journals Magnetorheological Fluids Behaviour in Oscillatory Compression Squeeze: Experimental Testing and Analysis

2019 ◽  
Vol 13 (4) ◽  
pp. 221-225
Author(s):  
Wojciech Horak ◽  
Marcin Szczęch ◽  
Bogdan Sapiński
Keyword(s):  
Magnetic Field ◽  
Volume Fraction ◽  
Experimental Testing ◽  
Magnetic Field Gradient ◽  
Particle Volume Fraction ◽  
Excitation Frequency ◽  
Magnetorheological Fluid ◽  
Density Level ◽  
Particle Volume ◽  
The Magnetic Field

Abstract This article deals with experimental testing of magnetorheological fluid (MRF) behaviour in the oscillatory squeeze mode. The authors investigate and analyse the influence of excitation frequency and magnetic field density level on axial force in MRFs that differ in particle volume fraction. The results show that, under certain conditions, the phenomenon of self-sealing can occur as a result of the magnetic field gradient and a vacuum in the working gap of the system.

Pre-Yield Shearing Regimes of Magnetorheological Fluids

2012 ◽  
Author(s):  
Waad Nassar ◽  
Xavier Boutillon ◽  
José Lozada
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Shear Strain ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Initial Response ◽  
Magnetic Pole ◽  
Particle Volume ◽  
Average Shear ◽  
The Magnetic Field

We analyzed experimentally the pre-yield regime of some MRFs. The hearing response is ruled by two successive regimes and limited by an interfacial phenomenon. The initial response is pseudo-elastic and independent from the magnetic field and of the particle volume fraction. The shear-stress limit of this regime is proportional to the square of the magnetic field and to the particle volume fraction. In the next regime, the shear strain is not uniform in the fluid. The increase in average shear stress varies linearly with the increase in average shear strain. The variation coefficient is proportional to the square of the magnetic field and decreases with the particle volume fraction. Finally, a loss of adhesion of the magnetic aggregates with the shearing plate or the magnetic pole occurs. The corresponding shear stress is proportional to the square of the magnetic field and to the particle volume fraction.

scholarly journals Dusty Nanofluid Past a Centrifugally Stretching Surface

2020 ◽  
Vol 2020 ◽  
pp. 1-16 ◽  
Author(s):  
Wubshet Ibrahim ◽  
Dachasa Gamachu
Keyword(s):  
Magnetic Field ◽  
Differential Equations ◽  
Velocity Profile ◽  
Ordinary Differential Equations ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Stretching Surface ◽  
Particle Volume ◽  
Magnetic Field Parameter ◽  
The Magnetic Field

This communication reports, the flow of Cu-water dusty nanofluid past a centrifugally stretching surface under the effect of second order slip and convective boundary conditions. The coupled nonlinear ordinary differential equations are get hold of from the partial differential equations which are derived from the conservation of momentum and energy of both nanofluid and dusty phases. Then, using apt resemblance transformation these ordinary differential equations were altered into a dimensionless form and then solved by bvp5c solver in Matlab software. The variation in velocity and temperature profiles of fluid and dusty phases for different parameters are thrash out in depth by figures and tables. The outcomes exhibit that the velocity profile of both fluid and dusty phases boot as the values of the dust particle volume fraction parameter is enlarged. Besides, the magnetic field parameter has similar effect on the velocity profile of both fluid and dusty phases. Also, the results illustrated that temperature profile of both Cu-water nanofluid and dusty particle phases are improved within an enhancement in the values of the temperature relaxation parameter, Cu-particle volume fraction, and Biot number. The results also confirm that for greater values of the magnetic field parameter the values of skin friction coefficient are enlarged for all values of the velocity ratio parameter.

scholarly journals Thermophoresis and suction/injection roles on free convective MHD flow of Ag–kerosene oil nanofluid

2020 ◽  
Vol 7 (3) ◽  
pp. 386-396
Author(s):  
Himanshu Upreti ◽  
Alok Kumar Pandey ◽  
Manoj Kumar
Keyword(s):  
Magnetic Field ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Mass Transfer Rate ◽  
Brownian Diffusion ◽  
Particle Volume ◽  
Ohmic Dissipation ◽  
Surface Mass

Abstract In this article, the mass and heat transfer flow of Ag–kerosene oil nanofluid over a cone under the effects of suction/injection, magnetic field, thermophoresis, Brownian diffusion, and Ohmic-viscous dissipation was examined. On applying the suitable transformation, PDEs directing the flow of nanofluid were molded to dimensionless ODEs. The solution of the reduced boundary value problem was accomplished by applying Runge–Kutta–Fehlberg method via shooting scheme and the upshots were sketched and interpreted. The values of shear stress and coefficients of heat and mass transfer were attained for some selected values of governing factors. The obtained results showed that when the amount of surface mass flux shifts from injection to the suction domain, the heat and mass transfer rate grew uniformly. However, they have regularly condensed with the rise in the magnitude of the magnetic field and particle volume fraction. Several researches have been done using cone-shaped geometry under the influence of various factors affecting the fluid flow, yet, there exists no such investigation that incorporated the response of viscous-Ohmic dissipation, heat absorption/generation, suction/blowing, Brownian diffusion, and thermophoresis on the hydro-magnetic flow of silver-kerosene oil nanofluid over a cone.

scholarly journals Effects of Filler Distribution on Magnetorheological Silicon-Based Composites

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3017 ◽  
Author(s):  
Sneha Samal ◽  
Marcela Škodová ◽  
Ignazio Blanco
Keyword(s):  
Magnetic Field ◽  
Surface Morphology ◽  
Smart Materials ◽  
Particle Distribution ◽  
Volume Fraction ◽  
Filler Particle ◽  
Iron Particles ◽  
Magnetorheological Elastomer ◽  
Linear Arrangement ◽  
Filler Distribution

The smart materials subclass of magnetorheological elastomer (MRE) composites is presented in this work, which aimed to investigate the influence of filler distribution on surface morphology. Iron particles with sizes ranging from 20 to 150 µm were incorporated into the elastomer matrix and a 30% volume fraction (V%) was chosen as the optimal quantity for the filler amount in the elastomer composite. The surface morphology of MRE composites was examined by 3D micro-computed tomography (µCT) and scanning electron microscopy (SEM) techniques. Isotropic and anisotropic distributions of the iron particles were estimated in the magnetorheological elastomer composites. The filler particle distribution at various heights of the MRE composites was examined. The isotropic distribution of filler particles was observed without any influence from the magnetic field during sample preparation. The anisotropic arrangement of iron fillers within the MRE composites was observed in the presence of a magnetic field during fabrication. It was shown that the linear arrangement of the iron particle chain induced magnetization within the composite. Simulation analysis was also performed to predict the particle distribution of magnetization in the MREs and make a comparison with the experimental observations.

Tunable isolator based on magnetorheological elastomer in coupling shear–squeeze mixed mode

2018 ◽  
Vol 29 (10) ◽  
pp. 2236-2248 ◽  
Author(s):  
Dingxin Leng ◽  
Tongtong Wu ◽  
Guijie Liu ◽  
Xiaojie Wang ◽  
Lingyu Sun
Keyword(s):  
Mixed Mode ◽  
Magnetic Particle ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Magnetorheological Elastomer ◽  
Applied Current ◽  
Particle Volume ◽  
Vibration Mitigation ◽  
Magnetorheological Elastomers ◽  
Design Construction

In this article, the systematic design, construction, and testing of a novel tunable isolator based on magnetorheological elastomers in coupling shear–squeeze mixed mode have been studied. The influence of magnetic particle volume fraction on field-induced properties of magnetorheological elastomer isolator is studied, and the performance of vibration mitigation of magnetorheological elastomer isolator is evaluated experimentally. The results show that the frequency-shift property of magnetorheological elastomer isolator is linearly proportional to the magnetic particle volume fraction and applied current, and vibration mitigation capacity of magnetorheological elastomer isolator is remarkably enhanced by increasing the applied current. The design of magnetorheological elastomer isolator in coupling mixed mode may provide a new insight for using magnetorheological elastomers in vibration reduction applications.

Radiation and non-uniform heat sink/source effects on 2D MHD flow of CNTs-H2O nanofluid over a flat porous plate

2019 ◽  
Vol 16 (4) ◽  
pp. 791-809
Author(s):  
Himanshu Upreti ◽  
Sawan Kumar Rawat ◽  
Manoj Kumar
Keyword(s):  
Magnetic Field ◽  
Heat Sink ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Porous Plate ◽  
Mhd Flow ◽  
Particle Volume ◽  
Content Type ◽  
Uniform Heat ◽  
The Impact

Purpose The purpose of this paper is to examine the velocity and temperature profile for a two-dimensional flow of single- and multi-walled nanotubes (CNTs)/H2O nanofluid over a flat porous plate, under the impact of non-uniform heat sink/source and radiation. The influence of suction/blowing, viscous dissipation and magnetic field is also incorporated. Design/methodology/approach The solution of the PDEs describing the flow of nanofluid is accomplished using Runge–Kutta–Fehlberg approach with shooting scheme. Findings Quantities of physical importance such as local Nusselt number and skin friction coefficient for both types of nanotubes are computed and shown in tables. Also, the impact of copious factors like Prandtl number, magnetic field, Eckert number, porosity parameter, radiation parameter, non-linear stretching parameter, injection/suction, heating variable, particle volume fraction and non-uniform heat sink/source parameter on temperature and velocity profile is explained in detail with the aid of graphs. Originality/value Till date, no study has been reported that examines the role of radiation and non-uniform heat sink/source on MHD flow of CNTs‒water nanofluid over a porous plate. The numerical outcomes attained for the existing work are original and their originality is authenticated by comparing them with earlier published work. This problem is of importance, as there are many applications of the fluid flowing over a flat porous plate.

scholarly journals Collective diffusion in sheared colloidal suspensions

2008 ◽  
Vol 597 ◽  
pp. 305-341 ◽  
Author(s):  
ALEXANDER M. LESHANSKY ◽  
JEFFREY F. MORRIS ◽  
JOHN F. BRADY
Keyword(s):  
Volume Fraction ◽  
Hard Spheres ◽  
Particle Volume Fraction ◽  
Strain Tensor ◽  
Density Fluctuations ◽  
Hydrodynamic Interactions ◽  
Simple Shear Flow ◽  
Particle Volume ◽  
Simulation Results ◽  
Sheared Suspensions

Collective diffusivity in a suspension of rigid particles in steady linear viscous flows is evaluated by investigating the dynamics of the time correlation of long-wavelength density fluctuations. In the absence of hydrodynamic interactions between suspended particles in a dilute suspension of identical hard spheres, closed-form asymptotic expressions for the collective diffusivity are derived in the limits of low and high Péclet numbers, where the Péclet number ${\it Pe}\,{=}\,\gamdot a^2/D_0$ with $\gamdot$ being the shear rate and D0 = kBT/6πη a is the Stokes–Einstein diffusion coefficient of an isolated sphere of radius a in a fluid of viscosity η. The effect of hydrodynamic interactions is studied in the analytically tractable case of weakly sheared (Pe ≪ 1) suspensions.For strongly sheared suspensions, i.e. at high Pe, in the absence of hydrodynamics the collective diffusivity Dc = 6 Ds∞, where Ds∞ is the long-time self-diffusivity and both scale as $\phi \gamdot a^2$, where φ is the particle volume fraction. For weakly sheared suspensions it is shown that the leading dependence of collective diffusivity on the imposed flow is proportional to D0 φPeÊ, where Ê is the rate-of-strain tensor scaled by $\gamdot$, regardless of whether particles interact hydrodynamically. When hydrodynamic interactions are considered, however, correlations of hydrodynamic velocity fluctuations yield a weakly singular logarithmic dependence of the cross-gradient-diffusivity on k at leading order as ak → 0 with k being the wavenumber of the density fluctuation. The diagonal components of the collective diffusivity tensor, both with and without hydrodynamic interactions, are of O(φPe2), quadratic in the imposed flow, and finite at k = 0.At moderate particle volume fractions, 0.10 ≤ φ ≤ 0.35, Brownian Dynamics (BD) numerical simulations in which there are no hydrodynamic interactions are performed and the transverse collective diffusivity in simple shear flow is determined via time evolution of the dynamic structure factor. The BD simulation results compare well with the derived asymptotic estimates. A comparison of the high-Pe BD simulation results with available experimental data on collective diffusivity in non-Brownian sheared suspensions shows a good qualitative agreement, though hydrodynamic interactions prove to be important at moderate concentrations.

A Novel Chain-Cluster Model of Magnetorheological Elastomer for the Dynamic Mechanical Performance Research

2021 ◽  
Author(s):  
Lili Fan
Keyword(s):  
Cluster Model ◽  
Mechanical Performance ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Dynamic Mechanical Properties ◽  
Magnetorheological Elastomer ◽  
Particle Volume ◽  
Microscopic Mechanism ◽  
Dynamic Mechanical ◽  
Response Characteristics

Abstract The existing research on magnetorheological elastomer (MRE) mainly focused on the improvement of MRE formula and structural design of MRE devices. As to the microscopic mechanism, less research has been done. Based on the scanning electron micrograph (SEM) of MRE, a novel chain-cluster model of MRE was constructed in this study. Particle size and particle distance were introduced simultaneously to the constitutive relation of MRE. The dynamic mechanical properties of MRE are studied theoretically and experimentally. Using the constructed chain-cluster model of MRE, the effect of magnetic field, particle volume fraction and strain on the magnetic-induced modulus of MRE were simulated. Rotating rheometer was adopted to test the magnetic response characteristics of MREs. Simulation and test results showed that the maximum magnetic-induced modulus tested experimentally was in good agreement with that calculated theoretically. Thus, the constructed chain-cluster model of MRE shows an important role in the field of intelligent vibration. It not only makes great sense in the prediction of MRE property but provides guidance on the property improvement of MRE.

scholarly journals Effects of magnetic field inclination and internal heat sources on nanofluid heat transfer and entropy generation in a double lid driven L-shaped cavity

2019 ◽  
pp. 325-325 ◽  
Author(s):  
Ali Chamkha ◽  
Zeinab Abdelrahman ◽  
Mohamed Mansour ◽  
Taher Armaghani ◽  
Ahmed Rashad
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Source ◽  
Mixed Convection ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Internal Heat ◽  
Performance Criteria ◽  
Particle Volume

Mixed convection has been one of the most interesting subjects of study in the area of heat transfer for many years. The entropy generation due to MHD mixed convection heat transfer in L-shaped enclosure being filled with Cu-water nanofluid and having an internal heating generation is explored in this investigation by the finite volume technique. Lid-motion is presented by both right and top parts of walls to induce forced convection and the cavity is under an inclined uniform magnetic field along the positive horizontal direction. The statistics concentrated specifically on the impacts of several key parameters like as the aspect ratio of the enclosure, Hartmann number, nano-particle volume fraction, and heat source length/location on the heat transfer inside the L-shaped enclosure. Outcomes have been manifested in terms of isotherm lines, streamlines, local and average Nusselt numbers. The obtained results show that addition of nanoparticles into pure fluid leads to increase of heat transfer. The maximum value of local Nusselt pertaining to the heat source occurs when L=0.1. Impacts of heat source size and location, internal heat generation absorption, angle of magnetic field on heat transfer and entropy generation are completely analyzed and discussed. The best configuration and values of important parameters are also presented using thermal performance criteria.

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