FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
PROVISIONAL/COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION: Magnetorheological Fluid base Semi Active Damper
2. APPLICANT(S)
1. (a) NAME: Registrar
(b) NATIONALITY: INDIAN
(c) ADDRESS: Maharaja Krishnakumarsinhji Bhavnagar University,
Gaurishankar Lake Road, Bhavnagar-364001, Gujarat India.
3. PREAMBLE TO THE DESCRIPTION
COMPLETE The following specification particularly describes the invention and the manner in which is to be performed

4. DESCRIPTION (Description shall start from next stage.)
The following specification particularly describes the invention and the manner in which it is to be
performed.
A conventional damper oil is considered to be a Newtonian liquid, in that it has a simple viscosity,
albeit temperature dependent. Whereas, the Magneto Rheological (MR) fluids have a yield stress
and a post-yield marginal viscosity, both dependent on the applied magnetic field. Hence, the MR
fluids are basically Bingham plastics, characterised by two parameters, the yield shear stress and the
subsequent marginal viscosity. In practical use, it is the controlled variation of the yield stress that is
the main operational parameter for this invention.
Accordingly, the present invention relates to a new and efficient method of controlling damping
force produced in a damper of vibrating system using magneto rheological (MR) fluid. MR fluids
are responsive mediums to an external excitation field. When this medium is subject to an electric
or magnetic field, its rheological properties undergoes significant changes. This phenomena makes
these fluids as smart fluids. MR fluids are getting more acceptance because of their ability to
produce highest stress. This highest stress variability is used to develop semi active damper. An MR
fluid is a suspension of micron-sized magnetically soft particles mixed in a carrier liquid. This
suspension is able to undergo dramatic changes in rheological properties. For instance, when
magnetic field is applied, MR fluid changes from free-flowing liquid state to a solid-like state in a
reversible way. Iron powder has high saturation magnetization property and because of this, it is
used as particle inclusion. When magnetic field is applied, these particles are arranged to form a
very strong chain of flux with the pole of one particle being attracted to the opposite pole of another
particle. Once particles are arranged in this pattern, these are restrained from moving away from
their respective flux lines and behave as barrier against the flow of the carrier fluid.
This work is solely based for automotive type shock absorber with magnetoreholocal fluid as
working medium.
The ultimate strength of an MR fluid depends on the square of the saturation magnetization of the
suspended particles. The key to a strong MR fluid is to choose a particle with a large saturation
magnetization. The best practical particles are simply pure iron, as they have saturation
magnetization of 2.15 Tesla. Typically, the diameter of the magnetisable particles is 3*to 10 microns.
Functional MR fluids may be made with larger particles; however, particle suspension becomes
increasingly more difficult as the size increases. Smaller particles which are easier to suspend could
be used, but the manufacturing of such particles is difficult. Due to the special behaviour of MR
fluid, it is used for developing semi active damper.
MR damper is capable of generating the force with magnitude sufficient for rapid response in large
scale applications, with requirement of only a battery for power. Additionally, these devices offer

highly reliable operations and their performance is relatively insensitive to temperature fluctuations or impurities in the fluid.
The present invention relates to a technique for producing varying damping force in a damper by using MR fluid. The damping force can be controlled by controlling magnetic field surrounded to MR fluid passes through orifice of damper.
The damper for present investigation (Figure 2) is made up of two principal components: housing and piston. Housing contains a volume of magnetorheological (MR) fluid. One fluid which has shown itself to be particularly well-suited for this application consists of iron particles suspended in an oil. Housing is a cylindrical tube with a first closed end with an accumulator and attachment eye associated therewith. A second or open end of the cylinder is closed by upper end cap. A seal is provided to prevent fluid leakage from housing. Accumulator is necessary to accommodate fluid displaced by piston rod as well as to allow for thermal expansion of the fluid. It also prevents cavitation effect. Piston head is spool shaped having an upper and a lower outwardly extending flange. Coil is wound upon spool-shaped piston head between upper flange and lower flange. Piston head is made of a magnetically permeable material, in this case, low carbon steel. Guide rails are attached above and below side of piston to keep the piston in center position to housing during operation. Piston head is formed with a smaller maximum diameter than the inner diameter, of housing. The external surfaces of guides are contoured to engage the inner diameter of housing. Guides are made of non-magnetic material, in this case, bronze, and it maintains piston centred within gap. In this model, gap (in conjunction with coil) functions as a valve to control the flow of MR fluid past piston. Electrical connection is made to coil through piston rod by lead wires. A first wire is connected to a first end of an electrically conductive rod which extends through piston rod to outside of damper. The second end of the windings of coil is attached to a "ground" connection on the outside of damper. The upper end of piston rod has threads formed thereon to permit attachment of damper, as depicted in figure. An external power supply, which provides a current in the range of 0-4 amps at a voltage of 12-24 volts, is connected to the leads. The outer surface of coil is coated with epoxy paint as a protective measure. The damper of this experiment functions as a Bingham type damper, i.e., this configuration approximates an ideal damper in which the force generated is independent of piston velocity and large forces can be generated with low or zero velocity. This independence improves controllability of the damper making the force a function of the magnetic field strength, which is a function of current flow in the circuit Novel features of the invention:
A novel feature of the invention is a Magnetorheological fluid based damper by using magnetorheological fluid instead of tradition fluid like oil. The Department of Physics, MK Bhavnagar University, Bhavnagar has Been a leading place where a variety of MR fluids have been

synthesized and characterized. The MR fluid developed in house was used in the prototype. The fluid is a suspension of a 4 to 10 micron diameter sized magnetically susceptible particles, in oil as carrier fluid. According to the data available by testing this MR fluid on rheometer at this laboratory, the density of the liquid is around 3 g/cm3 and off state viscosity of a 3.5 Pas. The maximum yield stress value is 15 kPa and it is achieved with the magnetic induction of 0.7 T. When exposed to a magnetic field, the rheology of the fluid reversibly and instantaneously changes from a free-flowing liquid to a semi-solid state with the controllable yield strength as a consequence of the sudden change in the particles arrangement. Figure 1 shows the detail relations of magnetic flux density, viscosity and shear stress available from rheometer.
Objectives of the invention:
The main objective of this invention is development of a semi active damper based on MR fluid. In order to achieve this we have used specially developed MR fluid having appropriate viscosity and suitable for predefine dynamic range which makes it superior to available designs.
To demonstrate our concept we have fabricated prototype of damper and characterized it by specially fabricated test rig at Physics department, M. K. Bhavnagar University, Bhavnagar, Gujarat.
Advantages over other known alternatives:
MR fluid dampers can be widely used because of their mechanical simplicity, high dynamic range (Ratio of Controllable force to uncontrollable force), low power requirements, large force capacity and robustness. This class of device has shown to match well with application demands and constraints to offer an attractive means of protecting various engineering systems against interrupted force. MR dampers are being developed for a wide variety of applications where controllable damping is desired. MR damper which utilize the advantages of MR fluids, are semi-active control devices and is popular topic for researchers.

5. CLAIMS (Not applicable for provisional specification. Claims should start with the preamble -
"I/We claim" on separate page)
We Claim developement of a MR fluid based damping device for shock and vibrarion isolation
using a MR fluid of our own design and specifically matched damper body and other parts of our
own design for a low cost solution and as import substitute.
Following steps comprise in development of MR fluid based damper (shock absorber):
(i) a magnetic field sensitive magnetorheological fluid with higher magnetic
saturation, low viscosity, and stable against sedimentation. (ii) The MR fluids have to be tuned for this particular application. These would also be useful for other applications requiring similar fluid like clutch or break. (iii) Prepare a prototype of MR fluid base damper comprising magnetic coil and
arrangement for supplying current to the coil. (iv) Testing of newly developed damper for characterization (Figure 3).
Thus by utilization of MR fluid in damper would produce a new technique of controlling damping force, which converts a passive damping system to semi active controlled damping system, having advantage of both passive and active control damping system.