Abstract—This paper presents the design, fabrication and evaluation of magneto-rheological damper. Semi-active control devices have received significant attention in recent years because they offer the adaptability of active control devices without requiring the associated large power sources. Magneto-Rheological (MR) dampers are semi- active control devices that use MR fluids to produce controllable dampers. They potentially offer highly reliable operation and can be viewed as fail-safe in that they become passive dampers if the control hardware malfunction. The advantage of MR dampers over conventional dampers are that they are simple in construction, compromise between high frequency isolation and natural frequency isolation, they offer semi-active control, use very little power, have very quick response, has few moving parts, have a relax tolerances and direct interfacing with electronics. Magneto- Rheological (MR) fluids are Controllable fluids belonging to the class of active materials that have the unique ability to change dynamic yield stress when acted upon by an electric or magnetic field, while maintaining viscosity relatively constant. This property can be utilized in MR damper where the damping force is changed by changing the rheological properties of the fluid magnetically. MR fluids have a dynamic yield stress over Electro-Rheological fluids (ER) and a broader operational temperature range. The objective of this papert was to study the application of an MR damper to vibration control, design the vibration damper using MR fluids, test and evaluate its performance. In this paper the Rheology and the theory behind MR fluids and their use on vibration control were studied. Then a MR vibration damper suitable for vehicle suspension was designed and fabricated using the MR fluid. The MR damper was tested using a dynamic test rig and the results were obtained in the form of force vs velocity and the force vs displacement plots. The results were encouraging and greatly inspire further research on the topic. Keywords—Magneto-rheological Fluid, MR Damper, Semi- active controller, Electro-rheological fluid. I. INTRODUCTION HE passive suspension’s drawbacks can be overcome by resorting to one of three techniques, adaptive, semi active or fully active suspension. An adaptive suspension utilizes a passive spring and an adjustable damper with slow response to improve the control of ride and handling. A semi active A. Ashfak, A. Saheed and K. K. Abdul Rasheed are with Mechanical Engineering department, TKM College of Engineering, Kollam – 05, University of Kerala, India (e-mail: ashfaktkm@yahoo.com, saheedtkm@yahoo.com, kkrasheddtkm@yahoo.com). J. Abdul Jaleel is with Electrical & Electronics Engineering department, TKM College of Engineering, Kollam-05, University of Kerala, India (e-mail: contact@drabduljaleel.com, phone: +91 474 2708713, +919446318713, Fax:+91474271023). suspension is similar, except that the adjustable damper has fast response (less than 10 ms) and the damping force is controlled in real time. A fully active suspension replaces the damper with a hydraulic actuator which can achieve optimum vehicle control, but at high cost. Technology related to vibration control has grown recently and taken on a more interdisciplinary nature. This has been caused by more demanding performance criteria and design specifications of all types of machines and structures. This is particularly true in the case of structural vibration control, robotics and vehicle suspension. Vibration control is becoming increasingly important as the design of mechanisms becomes more and more precise and less tolerant to transient vibration. Active/semi active control provides an important new tool for the control engineer. Many structures, such as automotive vehicles, tall buildings, robotic manipulator arms and flexible spacecraft have already been designed using active/semi- active vibration isolation as part of the total design. In active vibration control (Fig. 2) the damping force can be altered as required and hence we can control the vibration characteristics of the system. The conventionally used active force generator (F-active in Fig. 2) is a very complex hydraulic system and requires a very large control power. Also the system may collapse in case of a failure of the active force generator. To overcome these shortcomings we use semi-active controllers depicted in Fig. 3. Fig. 1 Fig. 2 Fig. 3 Passive suspension Active suspension Semi-active suspension Various semi-active dampers are being employed in different vibration isolation systems. Two such dampers are the newly conceived Electro-Rheological (ER) and Magneto- rheological (MR) dampers. The main advantages of these dampers are that they need very less control power, have simple construction, quick response to control signal and very few moving parts. MR Fluids are non-colloidal suspensions of magnetizable particles that are of the order of tens of 20-50 μm in diameter. MR devices are capable of much higher yield strengths when Design, Fabrication and Evaluation of MR Damper A. Ashfak, A. Saheed, K. K. Abdul Rasheed, and J. Abdul Jaleel T World Academy of Science, Engineering and Technology International Journal of Mechanical and Mechatronics Engineering Vol:3, No:5, 2009 530 International Scholarly and Scientific Research & Innovation 3(5) 2009 scholar.waset.org/1307-6892/10225 International Science Index, Mechanical and Mechatronics Engineering Vol:3, No:5, 2009 waset.org/Publication/10225