A.2.4 Optimal Design of a New Magnetorheological Mount Using Flexible Valve-Type Structure D.X. Phu, S.-H. Choi, H.-C. Kim, S.-B. Choi Inha University, Incheon, Korea Abstract: In this paper, a new type of vibration isolation mount utilizing magnetorheological fluid (MR mount in short) is proposed. This design is based on two operating modes of MR fluid : flow mode and shear mode. These modes are applied in the design which includes two components: fixed plates for applying the flow mode, and a flexible plate for applying the shear mode of MR fluid motion. These plates belong to the valve-type structure of mount. The primary objective such a MR mount is to overcome the lock-up phenomenon in the conventionaltype MR mount which normally appears at high frequencies with a very small excitation amplitude. The theoretical analysis for the design is undertaken followed by design optimization using ANSYS ADPL software. The objective functions are chosen by maximal damping force of MR mount. It has been shown through computer simulation that the lock-up phenomenon can be avoided and initial requirements with high damping force are successfully achieved by utilizing the proposed MR mount. Keywords: Magnetorheological (MR) Fluid, MR Mount, Flexible Valve-type Structure, Vibration Control, Optimal Design. Introduction As well known, a magnetorheological (MR) fluid is a type of smart materials which is currently applied in many helds of engineering such as dampers, clutches, brakes, mounts, etc. The applications of MR fluid can drive a new direction in vibration control and provide many benefits such as energy saving, stability guarantee, simple rnechanism, low cost easy control strategy compared with tradition vibration control method. So far, numerous application devices have been proposed using MR fluid in terms of theory and experiment. The MR valve structure was presented in [1] for the damper system. In this study, the MR valve was applied for design MR damper based on analytical method. This structure was simple with one coil or two coif outside of piston, and there are two mode of MR fluid; flow mode and shear mode. A different MR valve with both annular and radial was studied in [2]. In this structure, the efficiency was high and only flow mode was applied in here. A complex mode of MR fluid was presented in [3]. In this study, three modes of MR fluid; flow mode, shear mode and squeeze mode were appeared in the structure which was used as an isolator. A full review of MR structure was summarized in [a]. This study was undertaken as a base to develop a new design MR structure for both damper and mount. Two modes of MR fluid using squeeze mode and flow mode was applied in design MR mount in [5]. In this design, two coils was separated following the applied modes. MR fluid elastomer (MRFE) was also used for MR mount in [6]. A simple MR valve was also presented in [7] which was applied in design MR mount. The MR valve which was similar as [2] was also applied in design of MR mount [8,9]. Three mode of MR fluid was also applied in design MR mount in which two coils was separated [10]. From the above analysis, many of valve strucfures to design both damper and mount have been proposed. However, most of the proposed valve strucfures have a fixed damping gap in flow mode and shear mode. This may cause lock problem when the excitation magnitude is very small at high frequency operation. It is noted here that MR fluid does not flow in the lock-up state. Consequently, in order to resolve this problem in this work a new valve structure featuring flexible plates is proposed and optimally designed. An analytical model for mount is formulated followed by calculation damping force. And optimal design to determine principal design parameters of mount is performed by choosing the objective functions as maximal damping force of MR mount. It has been shown that the initial requirement of damping force can be achieved by applying the desiga parameters obtained from optimization of the proposed valve structure Confrguration and Modelin g Configuration of MR mount is presented in Figure I. In this structure, the shear mode and flow modes of MR fluid are applied in design. This is also called MR valve structure [8]. This configuration includes 9 components: rubber element for static loads, MR fluid, oring, housing, upper plate, flexible plate, coil, lower plate and base. In Figure l, the flexible plate will be varying depending on the variation of upper pressure and lower pressure. This variation will 82 ACTUATOR 2014,14th International Conference on NewActuators, Bremen, Germany, 23-25 June2014
prevent the "lock-up" phenomenon of MR fluid when the mount operates at high freqriency. Rubber MRF Ormg Housing Ipper Plate Flexible Plate N,Iagnetio Line Loter Plate Fig. 1: ConJiguration of proposed MR mount. Fig. 2: Parameters for optimizing the proposed MR mount. When the MR valve is activated by the applied magnetic field, the yield stress of MR fluid is increased acrossing the valve regions. This pressure drop Lpr^is controllable and is a function of the magnetic field strength. Thus, damping force g the MR damper is determined as follows: Fo : Lp uut rv + Lp roao,sgn(v) of To analyze design parameters in optimization, parametric model of MR mount is presented in Figure 2. In Figure 2, the damping gaps are dot,do2,d$,d,o,dor. Values of db,do4 are normally larger than dobdoz,dos to get advantage MR flow into valve structure. In this valve structure, the lockup phenomenon is frequently appeared at damping gaps such as dobdo2. Thus, the added damping gap do, will prevent this phenomenon. In design of damping gap of MR structure, values of gap are chosen from 1.2 mm to 2 mm.it is remarked that the higher value chooses, the smaller damping force gets. In this design, values of du,do2,dv,doo,do, are chosen by 1.5 mm, 1.5 mm, 1.6 mm, 1.6 mm, 1.2 mm, respectively. In this mount MRF 132DG is used whose yield stress is expressed as follows [9]: z" = 0.15+0.30858H +2.83544euH' -5.34429eaH' +9.20846e-eH* (tpu) where t, is the yield stress (kpa), t1 is the magnetic field intensity (ka/m). At the off-state, the passive pressure drop is caused by the base viscosity of the MR fluid. The total viscous pressure drop Apu* is associated with a Newtonian flow through the passages inside the MR valve. (t) where, r 4 r 1 4, _ (Rr + Rr+dr.r+a) -(n, +\+drr+a+dor). m[(n, + n, + dor+ a+ dorl nr+ $r* aor+ a)] - r / Y, t lh **, +ds3+a+dory -@r*^r*a,y'*ofil' Aois area of the central plate, v is the velocity of MR flow, ry is base viscosity of MR fluid at offstzte, ca and Cr are chosen constant. In this work, the range of these values is from 2 to 3. tro and rnare yield, stress of MR fluid at two different valve areas. Optimal Design and Results Materials using for optimization are steel 1018 as magnetic steel with maximal magnetic flux density B 1.93 Tesla and aluminum as non-magnetic steel with B 0 Tesla. The MRF l32dg used in this work has B 1.65 Tesla. The information is also used for evaluation optimizing results. In progress of optimization, ANSYS Parametric Design Language software is used to program for optimization. The progresses of optimization are concentrated in three parameters ; R3,Rt,Lt. Note that value of Z, is set up ACTUATOR 20'14, 14th International Conference on New Actuators, Bremen. Germanv. 23-25 June 2O14 83
equally Z, to get beneht in manufacturing. These parameters are more important than the others in maintaining the damping force, limit the difference between practical value and objective damping force. The objective value of damping force in this design is 25 kn. The initial values of L1, R1, R, are 14.5 mm, 12 mm, 20 mm, respectively. Initial optimized parameters of those are limited by 13<4<18, 8 < R1 < 20, 15 < R3 <20 mm, respectively. It is remarked that damping gaps such as dol,do2,d,,doo,dorare chosen as 1.5 mm, 1.5 mm, 1.4 mm, 1.4 mm, 1.2 mm, respectively. These values are chosen based on the calculation and the affection of parameters before optimizing. Values of du,do2should be equal for determining the range of movement of flexible plate. In Figure 3, all results of optimization are shown. After 7 iterations as shown in Figure 4, the results obtained by Lt =13.73 ffiffi, & = 15.14 ffiffi, & =15.56mm, respectively. The vertical damping gap dorin this optimization is 1.2 mm for this MR valve, and hence it also contributes to prevent the lock-up phenomenon. Before optimizing, the maximal magnetic flux density value is 1.61 Tesla but changed to1.66 Tesla after optimizing. These values are appropriate to the requirement of saturation of magnetic flux density for steel 1018 1.93 Tesla and MRF 1.65 Tesla. In Figure 5, the variation of damping force and magnetic flux density when the flexible plate changes are shown. It can be seen that the damping force is obtain to be minimal values 22 kn at 1.8 mm, and nearly 34 kn at 1.2 mm as shown in Figure 5(a). These values satisff the initial requirement. In addition, the magnetic flux density is always less than the saturation magnetic flux density of the choosing materials as shown in Figure 5(b). (d) Fig. 3: Optimization results of the proposed MR mount: (a) Meshing, (b) Distribution of magnetic lines, (c) MagneticJlux density, (d) Magneticflux vector. ^ 0.022 ':, 0.020 g, I 0.018 o f; o.ore! o.or+ a 0.012 o = 0010 C > 0.008 -t \ ' " \ /-R3 \, --Rl \/., Ll (L2) / Iteration Fig. 4: Optimization results of design variables of the proposed MR mount. 84 ACTUATOR 2014, 14th International Conference on New Actuators, Bremen, Germany, 23-25 June 2014
^34 =* t' Ero 828.Eo ru 724 822-1.72 E t.to E 1.68,$ r.oo.ff r.aq E ta. 13 14 1.5 1,6 1.7 1.8 Damping gap dol (mm) 1.60 1.2 1.3 1.4 1.5 1.6 17 1.8 Magnetic Flux Density (Tesla) (b) Fig. 5: Variation of damping gap dorwith other parameters: (a) Damping gap dotversus Damping force, (b) Damping gap dorversus Magnetic flux density. Conclusions This research has presented a new modified flexible mount which can change the damping gap to prevent lock-up problem which is frequently occurred at high frequency operation. The proposed type of valve structure featuring flexible plate can prevent the lock-up phenomenon which appears in fixed damping gap of MR valve structures. It has been shown through modeling and optimization that some requirements and magnetic flux density of the design are satisfied and the variation of damping force of MR mount is relatively small with respect to the change of damping gap. Acknowledgement This work was partially supported by the National Research Foundation of Korea (NRF) grant funded by the Korea govemment (MEST). (No. 2012-0005613) ral L-l Mikel Brigley, Young-Tai Choi, Norman M. Wereley and Seung-Bok Choi, "Magnetorheological isolators using multiple fluid modes", Journal of Intelligent Material Systems and Structures l8: 1143 (200'/). t4l Xiaocong Zhu,XingSian Jing and Li Cheng, "Magnetorheological fluid dampers: A review on structure design and analysis", Journal of Intelligent Material Systems and Structures, Published online. DOI: 10.1177 / r0 4s389X1243673 s (2012\. t5l T. M. Nguyen, C. Ciocanel, M. H. Elahinia, "A squeeze-fl ow mode magnetorheological mount: design, modeling, and experimental evaluation", Journal of Vibration and Ac ou s tic s, 134(2), 0210 13 (2012). t6l David York, Xiaojie Wang, Paramarz Gordaninejad, "A new magnetorheological mount for vibration control", Journal of Vibration and Acoustics, 133(3), 031003 (2011). I7l Young Kong Ahn, Mehdi Ahmadian, Shin Morishita, "On the design and development of a magneto-rheological mount", Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility, 32:2-3,199-216 (reee). t8l O.H. Kang, W.H. Kim, W.H. Joo, J.H. Park, "Design of the magnetorheological mount with high damping force for medium speed diesel generators", Active and Passive Smart Structures and Integrated Systems 2013, edited by Henry A. Sodano, Proc. of SPIE Vo1.8688, 86881E (2013). t9] Nguyen Quoc Hung, Phu Do Xuan, Park Joon Hee, Choi Seung Bok, Kang Ok Hyun, "Development of high damping magnetorheological mount for ship engines", Applied Mechanics and Materials, Vols. 336-338,9s3-9s9 (2013). [10] Xuan Phu Do, Joon Hee Park, Jae Kwan Woo and Seung Bok Choi, "Optimal design of new magnetorheological mount for diesel engines of ships", Transactions of the KSNVE,23(3), 209-217 (2013). References tll Q. H. Nguyen, S. B. Choi, Y. S. Lee and M. S. Han, "An analytical method for optimal design of MR valve structures", Smart Mater. Struct. 18,095032 (2009). l2l D.H. Wang, H. X. Ai andw. H. Liao, "A magnetorheological valve with both annular and radial fluid flow resistance gaps", Smart Mater. Struct. 18,115001 (2009). ACTUATOR 2014,14th International Conference on NewActuators, Bremen, Germanv, 23-25 June2014 85