Abstract. Keywords: Magnetorheological fluid, Shear stress, Shear rate, Shear viscosity, Phase angle. 1. Introduction

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1 INSTITUTE OF SMART STRUCTURES AND SYSTEMS (ISSS) J. ISSS Vol. 3 No. 2, pp , Sept JOURNAL OF ISSS REGULAR PAPER Preparation of a Silicon oil based Magneto Rheological Fluid and an Experimental Study of its Rheological Properties using a Plate and Cone Type Rheometer Shreedhar Kolekar 1, Rajashekar V. Kurahatti 2, Prashanth P.K 1, Vikram Kamble 1, Nitin Reddy 1 Mechanical Engineering Department, St. Joseph Engineering College, Mangalore Mechanical Engineering Department Basaveshwar Engineering College, Bagalkot Corresponding Author: shreedharkolekar@yahoo.co.in Keywords: Magnetorheological fluid, Shear stress, Shear rate, Shear viscosity, Phase angle. Abstract Magnetorheological (MR) fluids are suspensions of micron-sized magnetisable particles disperse in a nonmagnetic carrier fluid. The essential characteristic of these materials is that they can be rapidly and reversibly varied from the state of a Newtonian-like fluid to that of a stiff semisolid with the application of a moderate magnetic field. In this research work a silicon based magnetorheological fluid is prepared in the laboratory and tested using a cone and plate type rheometer for finding its characteristics of a MR fluid by measuring different rheological properties such as viscosity, shear stress, yield stress etc for different samples in detail. The properties of MR Fluids in terms of storage modulus (G'), loss modulus (G'') and loss factor (G''/G') are also presented. 1. Introduction Magnetorheological (MR) materials consist of micron size (typically 3 to 5 microns) particles which are magnetically permeable and suspended in a nonmagnetic medium. When a magnetic field is applied, the rheological properties of these materials are rapidly and reversibly altered. The mechanism responsible for this bulk effect is the induced magnetic interaction of the particles within the matrix. In MR fluids, the mutual interaction amongst the particles causes the formation of chain-like structures aligned roughly parallel to the applied magnetic field as shown in fig 1(A,B). It was first introduced by Jacob Rabinow at the National Bureau of Standards, now the National Institute for Science and Technology, in the United States in the 1940s and early 1950s. The configuration and rigidity of this structure depends upon several factors including the strength and distribution of the applied magnetic field. MR fluids are often modeled as Bingham plastics with a field dependent yield stress [Spasojevic et al. 1974]. MR solids have also been developed by incorporating magnetically permeable particles into an elastomer medium [Rigbi et al 1994]. Yield stresses of nearly 100 kpa have been reported in commercially available fluids by Lord Corporation A finite stress is developed to yield these chain structures [Jolly et al. 1996]. Hence, The tunability of the Rheological properties Available online at: Paper submitted on April 03, 2014; Accepted on May 04,

2 Silicon Oil Based Magneto Rheological Fluid and an Experimental Study of its Rheological Properties with the applied magnetic field provides the basis for a wide variety of commercial applications of MR Fluids including automobile clutches (Rabinow 1948), seismic vibration control (Dyke et al. 1996),active dampers (Spencer et al.1997), precision polishing (Kordonski and Golini 1999) prosthetics (Carlson et al. 2001), and drilling fluids (Zitha 2004). models and mechanisms of chain formation(parthasarathy and Klingenberg 1996; Goncalves et al.2006) MR Fluid formulation (Park et al.2010), MR fluids research and technology has been reviewed numerous times, with articles focusing on Rheology and flow properties (de Vicente et al. 2011a), and applications (Klingenberg 2001; Olabi and Grunwald 2007). to scatter in an oil medium, for instance silicone oil W H Li et al (1999) Muhammad Aslam et al (2006), Mark R. Jolly et al (1998), S. Genc et al (2002), hydrocarbon oil J Wang et al 2005, mineral oil J. H. Park et al (2001) J. Claracq et al 2004 and hydraulic oil. 3 Experimental systems: 3.1 Preparation of Magneto rheological fluid samples Preparation of MRFluid in the laboratory by using silicon oil is explained in the paper by S Elizabeth Premalatha et al (2012) Shreedhar Kolekar (2014) in detail. Here in this research work MR Fluid is prepared by using a low viscosity oil such as Silicon oil with iron powder in different concentrations and white lithium grease as an additive. 3.2 Composition of MR Fluid Silicon oil (viscosity Pas) Density=0.9659gm/ cm -3, Iron particles-4.7µm (BASF 2006) White lithium grease as an additive. Figure 1: Magnetorheological material A- before, B and after the application of an external magnetic field. 2 Composition and Properties of MR Fluid 2.1 Chemical Composition A typical MR Fluid consists of % by volume of relatively pure soft iron particles,soft iron particles size of 3-5 microns suspended in a carrier liquid such as mineral oil, synthetic oil, water or glycol. A variety of proprietary additives similar to those found in commercial lubricants are commonly added to discourage gravitational settling and promote particle suspension, enhance lubricity, modify viscosity, and inhibit wear. Table (1) Composition of constituents used and their weight percentage. Samples wt. % of materials for the preparation of MR Fluid Fe Particle Silicone oil Grease A 22% 78% 12% B 40% 60% 12% C 30% 70% 12% 3.3 Preparation of MR Fluid (1) The silicon oil is first mixed with grease in very small concentrations using a mechanical stirrer. This mixing process is done for 1 hour continuously till it is seen that the grease particles are dissolved and suspended in the silicon oil. The figure below shows how the grease mixed with silicon oil looks like on the completion of mixing. 2.2 Physical properties of MR fluids MR fluids exhibit dynamic yield strength values in excess of 50 KPa for applied magnetic field strength values of kam-1 and values over 100 KPa at saturation. An operational temperature for MR fluids ranges from -40 C to +150 C. Most of the researchers used carbonyl iron as particles Figure 2: Silicon mixed with grease. Please provide the correct text: 22

3 Kolekar et al. (2) After the solution is prepared as seen above, the required weighed iron powder is then poured into it, in parts while the stirring is carried out. As the iron powder mix into the container, it gets mixed along with the solution and becomes highly viscous and appears black in color. This stirring is carried out for about an hour and the end result obtained is MR Fluid. In the graph above the MR Fluid exhibits the linear viscosity relationship for the sample A&C decrease along with increase in shear rate, but sample B shows a high non linearity in terms of viscosity by an increase in the shear rate. 4.1 Frequency sweep (sample A): Figure 3: Prepared MR Fluid. In this way we prepared MR Fluid and it is almost 92% accurate in its rheological properties as compared to the commercially available fluid like Lord Corporation. 3.4 Characterization: The tests were carried out using a Kinexus (Plate and cone type) rheometer for finding its rheological properties such as viscosity, shear stress, yield stress etc for different samples. Specification of apparatus: Plate and cone diameter of 20mm through 60mm was used as the standard size range. Its ability to configure three critical rheometer functions independently, Rotational (shear) control - torque, speed and position, Vertical (axial) control gap and normal Force,temperature control, all rotational shear-based testing, advanced vertical (axial) testing including squeeze flow and track testing was measured. 4 Rheology test results: Figure 5: Storage and Loss modulus V/s Frequency Phase angle V/s Frequency of sample A In this part, the applied strain amplitude for all three MR samples was varied from %. And it can be seen that G', G'' and G''/G' are all very sensitive to the applied strain. The higher the strain, the higher the storage (elastic) modulus G' and loss (viscous) modulus G''. This may be attributed to the internal structures of the iron particles. Moreover, the storage modulus (G') of the MR Fluid was enhanced on increasing the applied magnetic field. 4.2 Frequency sweep (sample B): Figure 4: Viscosity v/s shear rate (flow curve) all samples. Journal of ISSS In the graph above the MR Fluid exhibits the linear viscosity relationship for the sample A&C decrease along with increase in shear rate, but sample B shows a high non linearity in terms of viscosity by an increase in the shear rate. 23

4 Silicon Oil Based Magneto Rheological Fluid and an Experimental Study of its Rheological Properties Figure 6: Storage and Loss modulus V/s Frequency Phase angle V/s Frequency of sample B Here the phase angle (δ) and elastic modulus (G') remains constant with an increase in frequency, but the viscous modulus (G'') shows some variations along with an increase in frequency. It has been found that the higher theweight fraction, the higher the storage modulus and loss factor. The experimental results are in good agreement with the effect of the volume fraction on the MR yield stress. 4.3 Frequency sweep (sample C): Figure 7: Storage and Loss modulus V/s Frequency Phase angle V/s Frequency of sample C The storage modulus G', loss modulus G'' and loss factor G''/G' were measured using the amplitude sweep method. GI and GII increase with a decrease in strain amplitude, as the frequency increases. However, the loss factor increases with increasing strain amplitude. The storage modulus does not rely on frequency. 5. Conclusions From the results above, it is clear that as the concentration of iron particles varies, the rheological properties also vary. The higher the weight fraction of iron particles, the higher the storage modulus and loss factor. The rheological property does not rely much on frequency. Acknowledgements Our sincere appreciation to Malvern Aimil Instruments, New Delhi for their kind support in this research work. References Aslam Muhammad, Yao liang, and Deng Zhong Chao (2006) Review of magneto-rheological (MR) fluids and its applications in vibration control- J. Marine Science and Application September, Volume 5, Issue 3, pp BASF(2006) Product datasheet: Carbonyl iron powders Carlson JD, Matthis W, Toscano JR (2001) Smart prosthetics based on magnetorheological fluids. In: Smart Structures and Materials 2001: Industrial and Commercial Applications of Smart Structures Technologies, vol Proceedings of the Society of Photo-Optical Instrumentation Engineers (Spie). Spie-Int Soc Optical Engineering, Bellingham, pp INSTITUTE OF SMART STRUCTURES AND SYSTEMS (ISSS) 24

5 Kolekar et al. Claracq J.J. Sarrazin and J. -P. Montfort, (2004) Viscoelastic Properties of Magnetorheological Fluids, Rheologica Acta, Vol. 43, De Vicente J, Klingenberg DJ, Hidalgo-Alvarez R (2011a) Magnetorheological fluids: a review. Soft Matter 7(7): Dyke.S.J, Spencer BF, SainMK, Carlson JD (1996) Modeling and control of magnetorheological dampers for seismic response reduction. Smart Mater. Struct. 5(5): Elizabeth P.S, R Chokkalingam, M Mahendran -Magneto Mechanical Properties of Iron Based MR Fluids-American J. Polymer Science, 2(4): Genc S. and P. Phule, Rheological Properties of Magnetorheological Fluids, Smart Materials and Structures, Vol. 11, 2002, Smart Mater. Struct doi: / /11/1/316. Jolly Mark R, J David Carlson and Beth C Munoz- Lord Corporation- A model of the behavior of magneto rheological materials- Thomas Lord Research Center, 405 Gregson Drive, Cary, North Carolina 27511, USA. Jolly Mark R., Jonathan W. Bender, J. David Carlson Proc. SPIE 3327, Smart Structures and Materials 1998: Passive Damping and Isolation, (16 June, 1998); doi: / Kolekar Shreedhar (2014) Preparation of Magnetorheological fluid and study on its rheological properties, International Journal of Nanoscience, Vol-13, No-2( , DOI /S X Kordonski WI, Golini D (1999) Fundamentals of magnetorheological fluid utilization in high precision finishing. J Intell Mater Syst Struct 10(9): Li.W.H, G Chen, S H Yeo (1999) Viscoelastic properties of MR fluids- Smart Mater. Struct doi: / /8/4/303 Lord (1994) Product Information: MR Fluid MRX- 100 and MRX-135CD, Lord Corp., Cary, NC, USA. Olabi AG, Grunwald A (2007) Design and application of magneto-rheological fluid. Mater Design 28(10): Parthasarathy M, Klingenberg DJ (1996) Electrorheology: mechanisms and models. Mat Sci Eng R 17(2): Park BJ, Fang FF, Choi HJ (2010) Magnetorheology: materials and application. Soft Matter 6(21): Journal of ISSS Park J.H., M. H. Kwon and O. O. Park, (2001) Rheological Properties and Stability of Magnetorheological Fluids using Viscoelastic Medium and Nanoadditives, Korean Journal of Chemical Engineering, Vol. 18, No. 5, Rabinow J (1948) The Magnetic fluid clutch AIEE Trans Rigbi Z and L Jilken (1983) the response of elastomers filled with soft ferrite to mechanical and magnetic influences J. Magnetism Magn Mat. pp Spasojevic D, T F Irvine and Afghan N (1974) The effect of a magnetic field on the rheodynamic behavior of ferromagnetic suspensions International Journal of Multiphase Flow, 01/1974; 1(5): DOI: / (74) Spencer BF, Dyke SJ, Sain MK, Carlson JD (1997) Phenomenological model for magneto rheological dampers. J Eng Mech-ASCE 123(3): Wang J., G. Meng, N. Feng, and E. J. Hahn, (2005) Dynamic Performance and Control of Squeeze Mode MR Fluid Damper-Rotor System, Smart Materials and Struct, Vol. 14, No. 4, Zitha PLJ (2004) Method of drilling with magnetorheological fluid. US Patent No Shreedhar Kolekar did his M.Tech(Machine Design) from Visvesvaraya Technological University Belgaum, currently he is Assistant Professor in Mechanical Engineering Department,St Joseph Engineering college Mangalore. His research interests includes smart materials, Vibration analysis,semiactive suspension control, fatigue of composites. Dr. Rajashekar V. Kurahatti obtained his PhD from Metallurgical and Materials Engineering department of National Institute of Technology Karnataka in He has teaching experience of 17 years. Presently he is working as Associate Professor in Basaveshwar Engineering College, Bagalkot. He has published 6 papers in international journals and presented 12 papers in international conferences. His research areas are heat treatment, composites and nanotechnology. Prashanth.P.K pursuing M.Tech in Computational Analysis in Mechanical sciences from St.Joseph Engineering college Mangalore. Vikram Kamble Pursuing B.E(Mechanical Engineering) from St Joseph Engineering College Mangalore.His research interests in smart materials like magnetorheological fluid, materials engineering. Nitin Reddy Pursuing B.E(Mechanical Engineering) from St Joseph Engineering College Mangalore research interests in smart materials like magnetorheological fluid, materials engineering. 25