Electrorheological (ER) Damper Is A Damper That Utilizes Electrorheological Fluid As The Working Fluid. By Changing The Strength Of Applied Electric Field To The Fluid, The Flow Resistance Of The Fluid Changes And Hence The Damping Characteristic Could Be Adjusted. This Paper Provides

Theoretical Formulation To Calculate The Damping Constant Of Semi-Active Flow Mode ER Damper. The Formula Is Developed By Analyzing Fluid Velocity Profile That Flows In Electrode Gap. From The Simulation, It Shows That Electric Field Strength Gives Severe Effect To The Damping Level Of The

Damper. Without Applying Electric Field, A Reduction On The Gap Of Electrode From 3 To 1 Mm Will Increase The Damping Constant Value By A Factor Of Only 27, While With A 3 Kvmmâ€“1 Electric Field Being Applied, The Increase Is By A Factor Of 595

Mohd. Nor, Mohd. Jailani

Mukhlis, Reiza Zakia

Nik Mohamed2, Nik Abdullah

English

Universiti Teknologi Malaysia Institutional Repository

THE DESIGN AND SIMULATION OF FLOW MODE ELECTRORHEOLOGICAL DAMPER 115Jurnal Teknologi, 44(A) Jun 2006: 115–125© Universiti Teknologi MalaysiaTHE DESIGN AND SIMULATION OF FLOW MODEELECTRORHEOLOGICAL DAMPERREIZA ZAKIA MUKHLIS1, NIK ABDULLAH NIK MOHAMED2 &MOHD JAILANI MOHD NOR3Abstract. Electrorheological (ER) damper is a damper that utilizes electrorheological fluid asthe working fluid. By changing the strength of applied electric field to the fluid, the flow resistanceof the fluid changes and hence the damping characteristic could be adjusted. This paper providestheoretical formulation to calculate the damping constant of semi-active flow mode ER damper.The formula is developed by analyzing fluid velocity profile that flows in electrode gap. From thesimulation, it shows that electric field strength gives severe effect to the damping level of thedamper. Without applying electric field, a reduction on the gap of electrode from 3 to 1 mm willincrease the damping constant value by a factor of only 27, while with a 3 kVmm–1 electric fieldbeing applied, the increase is by a factor of 595.Keywords: Vehicle suspension, electrorheological damper, electrode gapAbstrak. Peredam elektroreologi (ER) adalah peredam yang menggunakan bendalirelektroreologi sebagai bendalir kerja. Dengan mengubah kekuatan medan elektrik yang diberikankepada bendalir ER, ketahanan alir daripada bendalir tersebut berubah dan kerananya ciriredamannya dapat dilaras. Kertas kerja ini menyediakan perumusan teori untuk menghitung pemalarredaman daripada peredam separa aktif ER ragam alir. Rumusan tersebut diterbitkan melaluianalisis daripada profil halaju bendalir yang mengalir di dalam sela elektrod. Daripada hasil simulasi,didapati bahawa kekuatan medan elektrik memberikan pengaruh yang sangat besar terhadaptingkat redaman daripada peredam. Tanpa pemberian medan elektrik, pengurangan sela antaraelektrod daripada 3 mm kepada 1 mm akan menaikkan nilai pemalar redaman sebesar 27 kaliganda sahaja. Manakala dengan pemberian medan elektrik sebesar 3 kVmm–1, nilai pemalarredaman meningkat sebanyak 595 kali ganda.Kata kunci: Ampaian kenderaan, peredam elektroreologi, sela elektrod1.0 INTRODUCTIONIn the design of vehicle suspension system, there must be a compromise betweentwo conflicting requirement, which are road handling and ride comfort. To get agood ride comfort, lightly damped suspension is needed. On the other hand, heavilydamped suspension is needed to get good handling. Since the road condition israndom in nature and may vary from one profile to another, the optimum performance1,2&3 MEMS-B Research Group, Department of Mechanical and Materials Engineering, UniversitiKebangsaan Malaysia, 43600 Bangi, Selangor, MalaysiaJTJun44A[08].pmd 02/15/2007, 18:53115REIZA ZAKIA, NIK ABDULLAH & MOHD JAILANI116of the suspension system can only be obtained using damper with adjustable dampingcharacteristic. There are two ways to adjust the damping level, whether controllingthe fluid properties or modifying the orifice. Electrorheological fluid is a class of dispersion which is commonly composed ofpolarisable solid particles as dispersion phase and non conducting oil as dispersedphase. Upon the imposition of external electric field, the particle will polarised andform a chainlike structure along the directions of the electric field. This structureis responsible for the rheological properties alteration of the ER fluid from a fluid-like state to a solid-like state which exhibits a yield stress. The reversible anddramatic change in the rheological properties of ER fluids coupled with the instantresponse made the fluid suitable to be used as working fluid for the system mentionedabove.2.0 DESIGN CONCEPT OF INTELLIGENT SUSPENSIONSYSTEMAn intelligent suspension system which utilize ER damper has been proposed byMukhlis et al. [1], as shown in Figure 1.Figure 1 Schematic diagram of an intelligent ER suspension system [1]ProcessingControlsystemProcessingElectricsourceERFdamperActualdampinglevelDesired dampinglevelSensorRoadprofileSensorSuitable dampinglevelA sensor, which can be a camera or laser apparatus, will get information fromroad profile. This information is then processed to determine the required dampinglevel. Simultaneously, another sensor i.e. load cell and LVDT, through someprocessing will determine the actual damping level. From these information, thecontrol system will then give command to electrical source to apply a certain amountof electrical field to ER-damper. Finally, the ER-damper will then produce a suitabledamping level according to the measured road profile. This system is classified asJTJun44A[08].pmd 02/15/2007, 18:53116THE DESIGN AND SIMULATION OF FLOW MODE ELECTRORHEOLOGICAL DAMPER 117semi-active system since it can only dissipate energy but cannot inject energy to thesystem. The damper used in the system is flow mode-ER damper. Flow mode is chosensince this mode gives higher yield stress than shear mode for the same electric fieldstrength applied [2]. The relationship between electric field strength to the yieldstress and damping constant of the damper is discussed in the following section.3.0 MATHEMATICAL MODELBasically, the flow mode ER-damper consists of piston rod and piston head inconcentric cylinder tubes which also act as electrodes (Figure 2). If a certain level offorce is given to the piston rod, there will be a pressure drop between the uppersection and the lower section inside the annular gap and the fluid will move with acertain flux or velocity.Figure 2 Flow mode ER damperPiston rodPiston headElectrodesER fluidBushingSealLDR1R2In the case where electrode gap (D) is much less than inner electrode diameter(2Rl), the solution for the Poiselle flow between concentric cylinders collapses tothat flow between parallel plates [3]. For the fluid between parallel plates, the forceequilibrium is [4]:d Pdr Lτ ∆=  (1)F, VoJTJun44A[08].pmd 02/15/2007, 18:53117REIZA ZAKIA, NIK ABDULLAH & MOHD JAILANI118where τ is the shear stress, L is the electrode length and ∆P is the pressure drop.Without the application of external electric field, the particle phase of ER fluid israndomly distributed in dispersed phase and act as Newtonian fluid (Figure 3).The shear stress of Newtonian fluid is proportional to the velocity profile gradientthrough the gap as:0dudrτ µ= (2)where µ0 is the viscosity and u is the velocity.Figure 3 Schematic illustrations of the ER particles before and after application of an electricfield. The two parallel dark lines stand for two electrodes [5]E EThe equation for the velocity profile (Figure 4) can be obtained by substitutingEquation (2) to Equation (1) and integrating with respect to r, as:( ) ( )202Pu r r Drµ∆= − (3)By inserting the non-slip condition at the boundary such that u(0) = u(D) = 0,yields( ) ( )22Pr r DLτ∆= − (4)Figure 4 Newtonian fluid velocity profileDxrR1JTJun44A[08].pmd 02/15/2007, 18:53118THE DESIGN AND SIMULATION OF FLOW MODE ELECTRORHEOLOGICAL DAMPER 119The fluid volume flux through the electrodes (QN) is obtained via integrating thevelocity profile over the annular electrode gap, which is:πµ∆= −3106NR D PQL (5)The fluid volume flux through annulus (QN) is equal to the fluid volume fluxdisplaced by the piston head (Qp). Since Qp = Apv0 and ∆P = −F/Ap, yields:200316pA LF vR Dµπ= (6)By noting that F = CNv0, gives:20316pNA LCR Dµπ= (7)In the above equations, Ap, CN and v0 are area of piston head minus area of rod,zero-field damping constant and piston head velocity respectively.If a certain amount of electric field strength is applied to ER fluid, the particlephase of the fluid will polarize and form a chainlike structure between the electrodes(Figure 3). The fluid will only flow if the stress given is greater than a critical pointcalled yield stress, τy. This condition can be modeled by Bingham plastic behavioras:sgny pdu dudr drτ τ µ = =   (8)The higher electric field strength (E) applied, the higher τy will be produced. Therelationship between E and τy is [6,7]:( ) 2y E E Eτ α β χ= + + (9)where α, β  and χ are the characteristic value for the particular ER fluid which areobtained via experiment.Figure 5 Bingham fluid velocity profileRegion 3Region 2Region 1R1xrrp1δrp2Du(D) = 0u(0) = 0JTJun44A[08].pmd 02/15/2007, 18:53119REIZA ZAKIA, NIK ABDULLAH & MOHD JAILANI120The velocity profile of Bingham flow can be divided into three regions (Figure 5).Regions 1 and 3 are called post yield conditions while region 2 is called as pre yieldcondition. On regions 1 and 3, τ  is higher than τ y so that the material is sheared. Onthe other hand, τ  in region 2 is lower than τ y so that the material will flow as a plug.From the integration of Equation (1), shear stress in region 2 is:2 1Pr CLτ∆= + (10)By inserting boundary condition such that τ(rp1) = τy and τ(rp2) = –τy yields:1 1y pPr CLτ∆= + and 2 1y pPr CLτ∆− = +   (11)Subtraction of these equations yields equation for plug thickness as:2 12y pp pA Lr rFτδ− = = (12)By introducing non dimensional plug thickness Dδδ =  and noting that rp2 – rp1= δ  and  gives equations:( )112pDrδ−= (13)( )212pDrδ+= (14) Substituting Equation (8) into Equation (1), integrating it with respect to r andinserting boundary condition such that shown in Figure 5, yields velocity profileequations for each region as:( )1 1ppPu r r rLµ∆= − (15)( )µ∆= −22 12 ppPu r rL (16)( ) ( )2 23 2 22 22 p ppPu r r r r r D DLµ∆= − + − (17)by integrating fluid velocity profile for the whole regions with respect to r yieldsequation for volume flux of Bingham flow as:( ) ( )π δ δµ∆= − +3 21 1 212B pR PDQL(18)JTJun44A[08].pmd 02/15/2007, 18:53120THE DESIGN AND SIMULATION OF FLOW MODE ELECTRORHEOLOGICAL DAMPER 121since pP F / A∆ = − , gives:( ) ( )( )2 12 031121 2p pBLAF vR Dµδ δπ−= − + (19)so that the damping constant is:( ) ( )( )2 1231121 2p pBLACR Dµδ δπ−= − + (20)For Newtonian condition (E = 0 and 0δ = ), Equation (20) is similar with Equation(7).All preceding equations are valid for the assumption that the flow is steady andlaminar and the viscosity of the fluid remains constant at working temperature. Thecomplete equation can be found in [8].4.0 RESULTS AND DISCUSSIONSSeveral simulations have been done by using some commercially available ER fluid:Al 3565 (made by Bayer AG Germany), TX-ER5 (made by Nippon Shokubai, Co.,Ltd. Japan) and ER-100 (made by Lord Corp. USA). The viscosity of the fluids at25°C are 66.13, 48 and 220.31 mPa respectively. The nominal damper design is: L is101.6 mm, R1 is 25.4 mm, piston head diameter is 50.8 mm, and electrode gap is2 mm.The relationship between electric field to the yield stress for each fluid is obtainedfrom data in [9] and shown in Figure 6.Figure 6 Effect of electric field strength to the τy80Al 3565y = 0.1439x2 + 0.2733xYield stress (kPa)TX-ER5y = 0.1079x2 + 0.0237xER-100y = 0.0145x2 + 0.1916x1 2 3 4 5 6 723456710Electric field strength (kV/mm)JTJun44A[08].pmd 02/15/2007, 18:53121REIZA ZAKIA, NIK ABDULLAH & MOHD JAILANI122The damping constant produced by the nominal damper filled up with each fluidis shown in Figure 7. The damping constant is obtained by substituting the dimensionof the damper and the fluid properties to Equations (8), (12) and (20).Figure 7 Relationship between electric field strength to the damping constant for nominal damperfilled up with particular fluid25000Al 3565Damping constant (Ns/m)ER-100TX-ER50.5 1 1.5 2 2.5 3 3.55001000150020000Electric field strength (kV/mm)4 4.5From Figure 7, it can be concluded that the damper filled with Al 3565 has thewidest controllable range. This condition prevail since the fluid has low viscosity atzero field condition and has the highest yield stress in the application of externalFigure 8 Force versus velocity diagram for nominal damper filled up with Al 3565Force (N)Piston velocity (m/s)4kV/mm0.13kV/mm2kV/mm1kV/mm0kV/mm0.3 0.5 0.7–400–800–1200400800–0.1–0.3–0.5–0.71200JTJun44A[08].pmd 02/15/2007, 18:53122THE DESIGN AND SIMULATION OF FLOW MODE ELECTRORHEOLOGICAL DAMPER 123electric field. For the application of electric field strength up to 4 kVmm–1,the damping constant produced by Al 3565 is in the range between 250 to 2000Nsm–1. The following discussion is focused on damper that is filled up with Al 3565fluid.Figure 8 shows the relationship between force versus piston velocity for eachelectric field strength applied. For a given electric field strength, the applied loadmust exceed a minimum force before the piston starts to move. From Figure 8, it canbe seen that for a given piston velocity, the damping force for 4 kVmm–1 electricfield strength applied is higher by a factor of 7 compared with zero-field condition.The higher this difference factor, a wider controllable range for the semi-active damperwill be obtained.Figure 9 shows the effect of electrode gap variation to the damping constant fornominal damper design filled up with Al 3565 in logarithmic scale. The dampingconstant appears to be very sensitive to the gap dimension. In zero-field condition,as the gap tapered from a maximum of 3 mm to a minimum of 1 mm, the dampinglevel increase by a factor of 27. It increases from 75 to 2000 Nsm–1. This trendbecomes even more severe as the applied electric field increase to 3 kVmm–1. In theapplication of 3 kVmm–1 electric field, the damping level increase by a factor of 595as the gap tapered from a maximum of 3 mm to a minimum of 1 mm. The resultsagree with [6]. In zero field condition, the damping constant is influenced by gapdimension only. While in the on-field condition, the damping constant is alsoinfluenced by the chainlike structures, which are stronger as the electric field strengthincreases.Figure 9 Effect of electrode gap variation to the damping constant for various electric field strength0 kvDamping constant (Ns/m)0.51000Electrode gap (mm)10000100000100100 1 1.5 2 2.5 3 3.51 kV/mm2 kV/mm2.5 kV/mm3 kV/mmJTJun44A[08].pmd 02/15/2007, 18:53123REIZA ZAKIA, NIK ABDULLAH & MOHD JAILANI124Figure 10 shows the effect of electrode length variation to the damping constant.Similar to electrode gap variation, the variation of electrode length also has higherinfluence on the damping constant in on-field condition. However, the influence ofelectrode length variation is not as severe as electrode gap variation.In zero-field condition, the alteration of electrode length from a minimum of 75mm to a maximum of 150 mm yields the increase in damping constant value by afactor of 2, while in a condition when 3 kVmm–1 of electric field strength is applied,the increasing is by a factor of 6. In on-field condition, the electrode length variationdoes not only influence the pressure drop, but also effects the yield stress of the ERfluid. The amount of ER fluid involved in chainlike structure formation increases asthe electrode longthens, which in turn increases the yield stress.5.0 CONCLUSIONSFrom the mathematical model and the simulations presented, it can be concludedthat the high damping level can be obtained by increasing the electric field strength,choosing an appropriate ER fluid, increasing the electrode length or decreasing thegap between the electrodes.The ER damper filled with Al 3565 has a wider controllable range compared tounits ER damper filled with TX-ER5 or ER-100 since Al 3565 produces the highestyield stress for a given electric field strength.The variation of electrode gap and electrode length has a significant effect on thedamping value of the damper. In on-field condition, the effect is even more severeFigure 10 Effect of electrode length variation to the damping constant for various electric fieldstrength0 kvDamping constant (Ns/m)75100015002000500050 100 125 150 1751 kV/mm2 kV/mm3 kV/mm2500Electrode length (mm)JTJun44A[08].pmd 02/15/2007, 18:53124THE DESIGN AND SIMULATION OF FLOW MODE ELECTRORHEOLOGICAL DAMPER 125since the variation of the gap and the length of the electrode do not only influencethe pressure drop, but also the yield stress of the material.ACKNOWLEDGEMENTSThe authors would like to thank the Malaysian Ministry of Science, Technology andEnvironment for sponsoring this research under project IRPA 03-02-02-0016 SR0003/07-02.REFERENCES[1] Mukhlis, R. Z., N. A. N. Mohamed, and M. J. M. Nor. 2004. A Preliminary Study on Developing anIntelligent Automotive Suspension using Electrorheological Fluid. Proceeding of Engineering MaterialsSeminar and Exhibition 2004. Institut Teknologi Bandung Indonesia. 111-121.[2] Len, H. G., and S. B. Choi. 2002. Dynamic Properties of an ER Fluid Under Shear and Flow Modes.Material and Design. 23: 69-76.[3] Makris, N., S. A. Burton, and D. P. Taylor. 1996. Electrorheological Damper with Annular Ducts forSeismic Protection Applications. Smart Materials and Structures. 5: 551-564.[4] Hughes, W. F. 1979. An Introduction to Viscous Flow. London: McGraw-Hill Book Company.[5] Hao, T. 2002. Electrorheological Suspensions. Advances in Col loid and Interface Science. 97: 1-35.[6] Kamath, G. M., M. K. Hurt, and N. M. Wereley. 1996. Analysis and Testing of Bingham Plastic Behaviorin Semi-active Electrorheological Fluid Dampers. Smart Materials and Structures. 5: 576-590.[7] Lindler, J., and N. M. Wereley. 2003. Quasy-steady Bingham Plastic Analysis of an ElectrorheologicalFlow Mode Bypass Damper with Piston Bleed. Smart Materials and Structures. 12: 305-317.[8] http://www.tudresden.de/mw/ilr/lampe/DATENBAN/ERF-UEB (29 July 2005).[9] Mohamed, N. A. N., M. J. M. Nor, and R. Z. Mukhlis. 2005. Compromising Vehicle Handling andPassenger Ride Comfort Using ER Damper. Mechanika. 4(54) : 50-54.JTJun44A[08].pmd 02/15/2007, 18:53125

The Design And Simulation Of Flow Mode Electrorheological Damper

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The Design And Simulation Of Flow Mode Electrorheological Damper

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