*2.5.1 Shear mode*

In this type of mode of ER damper there are one or two parallel electrodes which can move parallel to each other and is always perpendicular to the electric field applied so that the fluid can have uniform shear and the ER fluid is present in between the two electrodes. From **Figure 5a** c and l are the breath and length of the electrode and j is the electrodes gap. Here E is given voltage, F is net damping force and V is the relative velocity of the electrodes. Two forces are acting in this ER damper (a) Active force Fc because of ER effect and (b) Passive force Fy due to the fluid viscosity. Fy, i.e., the passive force is always present and directly linked with the viscosity of the fluid as well as the damper geometric properties. During application of the electric field a force Fc (because of creation of particles suspension lining up between the electrodes) i.e. static force which is needed to overwhelmed so that the motion can occur [10]. The force Fc is product of area of electrode and the yield strength of the fluid and does not depend on the electrode plate velocity. The net force F of damping of this ER damper is the sum of two components of force. The main aim of this ER damper is to give large ratio of off-field to on-field damping by force ratios Fy and Fc. Because of this large ratio gives various responses by ER unit with changing voltage.

## *2.5.2 Valve mode*

In this type of mode the ER fluid is pressed between the two electrodes as given in **Figure 5b**. Because of this the ER fluid is exposed to tensile, compression as wells as shear. In the absence of the given electric field if the ER fluid is pressed it behaves like Newtonian fluid. There is a pressure drop AP occurs at flow rate volume Q. This pressure change in between the valve is because of the velocity of the ER fluid. Moreover, during the presence of the electric field, yield stress is generated by the ER fluid which results more pressure drop between the electrodes plates length. The net damping force is summation of two force components of this type of ER

**135**

*A Review on Electro-Rheological Fluid (ER) and Its Various Technological Applications*

damper. In this type of mode the device effectiveness is the across valves pressure

In this mode the gap between the electrodes are changed and the ER fluid is pressed or squeezed by the force acting normally. **Figure 5c** represents the squeez-

ER fluids have wide applicability, economic benefit, social benefit high performance for these advantages these smart fluids will find path in various engineering applications in various technological fields. Without any doubt we can say in the future ER technology is going to rule various applications in engineering technological fields. As soon as this technology is accepted then it will be a revolution in both economy and society. From all these advantages of the ER fluids we can predict that in the near future the ER fluids will be used in various technological fields as given below.

Scientists and Engineers can develop new kind of parts that can easily fulfill the needs of the motor vehicles using the technology of ER. Like for example ER

The electrorheological fluids which are totally dependent on the applied electric fields are used in resistive force creation and damping. Examples of applications are active vibration suppression and motion control. L. Wang et al. [4] have presented the uses of ER fluids in microfluidics. Various industries like automobiles industries are demanding modified ER fluids with more efficiency Gurka et.al [6] introduced ER-Fluid RheOil®3.0 which improves the sedimentation and re-dispersing behavior. Brennan et al. [7] studied and distinguished the two classes of the ER dampers, first one acts by shearing the stationary fluid and the second one acts by pumping

*DOI: http://dx.doi.org/10.5772/intechopen.90706*

drop with or without the effect of ER [10].

*Modes of operation: (a) shear, (b) valve, and (c) squeeze.*

*2.5.3 Squeeze mode*

**Figure 5.**

ing mode of the ER fluid.

the ER fluid. The two classes are described in details below.

*2.5.4 Applications of ER fluid technique in engineering field*

*2.5.4.1 Automobile/motor vehicle industry*

**Figure 4.** *Actuator friction (a) friction columbic, (b) friction viscous, and (c) total friction.* *A Review on Electro-Rheological Fluid (ER) and Its Various Technological Applications DOI: http://dx.doi.org/10.5772/intechopen.90706*

**Figure 5.** *Modes of operation: (a) shear, (b) valve, and (c) squeeze.*

damper. In this type of mode the device effectiveness is the across valves pressure drop with or without the effect of ER [10].

The electrorheological fluids which are totally dependent on the applied electric fields are used in resistive force creation and damping. Examples of applications are active vibration suppression and motion control. L. Wang et al. [4] have presented the uses of ER fluids in microfluidics. Various industries like automobiles industries are demanding modified ER fluids with more efficiency Gurka et.al [6] introduced ER-Fluid RheOil®3.0 which improves the sedimentation and re-dispersing behavior. Brennan et al. [7] studied and distinguished the two classes of the ER dampers, first one acts by shearing the stationary fluid and the second one acts by pumping the ER fluid. The two classes are described in details below.

#### *2.5.3 Squeeze mode*

*Extremophilic Microbes and Metabolites - Diversity, Bioprospecting and Biotechnological...*

is known as motion of stick–slip.

ER unit with changing voltage.

*2.5.2 Valve mode*

is taken.

*2.5.1 Shear mode*

small vibrations can cause poor accuracy [9]. Bad effect of the friction is also present in the system when the force applied is near to overwhelm the static friction this

At a near to zero velocity the stick–slip motion happens like an unexpected motion of jerking. Naturally, kinetic friction coefficient in between the two surfaces is smaller than the static friction coefficient. When the given force is more to overwhelm than the static friction then the friction decreases from static to dynamic. Because of this sudden decrease of the friction there will be a sudden velocity jump movement. To show this effect the system of two degree of freedom

In this type of mode of ER damper there are one or two parallel electrodes which can move parallel to each other and is always perpendicular to the electric field applied so that the fluid can have uniform shear and the ER fluid is present in between the two electrodes. From **Figure 5a** c and l are the breath and length of the electrode and j is the electrodes gap. Here E is given voltage, F is net damping force and V is the relative velocity of the electrodes. Two forces are acting in this ER damper (a) Active force Fc because of ER effect and (b) Passive force Fy due to the fluid viscosity. Fy, i.e., the passive force is always present and directly linked with the viscosity of the fluid as well as the damper geometric properties. During application of the electric field a force Fc (because of creation of particles suspension lining up between the electrodes) i.e. static force which is needed to overwhelmed so that the motion can occur [10]. The force Fc is product of area of electrode and the yield strength of the fluid and does not depend on the electrode plate velocity. The net force F of damping of this ER damper is the sum of two components of force. The main aim of this ER damper is to give large ratio of off-field to on-field damping by force ratios Fy and Fc. Because of this large ratio gives various responses by

In this type of mode the ER fluid is pressed between the two electrodes as given in **Figure 5b**. Because of this the ER fluid is exposed to tensile, compression as wells as shear. In the absence of the given electric field if the ER fluid is pressed it behaves like Newtonian fluid. There is a pressure drop AP occurs at flow rate volume Q. This pressure change in between the valve is because of the velocity of the ER fluid. Moreover, during the presence of the electric field, yield stress is generated by the ER fluid which results more pressure drop between the electrodes plates length. The net damping force is summation of two force components of this type of ER

*Actuator friction (a) friction columbic, (b) friction viscous, and (c) total friction.*

**134**

**Figure 4.**

In this mode the gap between the electrodes are changed and the ER fluid is pressed or squeezed by the force acting normally. **Figure 5c** represents the squeezing mode of the ER fluid.

#### *2.5.4 Applications of ER fluid technique in engineering field*

ER fluids have wide applicability, economic benefit, social benefit high performance for these advantages these smart fluids will find path in various engineering applications in various technological fields. Without any doubt we can say in the future ER technology is going to rule various applications in engineering technological fields. As soon as this technology is accepted then it will be a revolution in both economy and society. From all these advantages of the ER fluids we can predict that in the near future the ER fluids will be used in various technological fields as given below.

#### *2.5.4.1 Automobile/motor vehicle industry*

Scientists and Engineers can develop new kind of parts that can easily fulfill the needs of the motor vehicles using the technology of ER. Like for example ER technology used for cooling engine i.e. speed fan clutch of the motor vehicle, shock absorber, brake having break torque controlled, system for suspensions by damping controlled etc., These components using ER technologies will have less wear and tear, more performance, less cost, prolong life service, controlled easily, easy to produce by microcomputer, fast response, high sensitivity.

## *2.5.4.2 Hydraulic industry*

The valves which are used nowadays for control of pressure and flow rate control can be replaced by ER technology in the future. Because ER technology valves will have no or less movable parts, simple easy structure, low cost, prolong service life, no mechanical processing, minimal tear and wear and electronical control of pressure and rate of flow. For this reasons ER technology will rule the hydraulic industry in the near future.

#### *2.5.4.3 Fluid sealing field*

By utilizing the benefits of the ER technology engineers can produce new type of rotational sealing controlled devices for face the challenges of the magnetic fluid sealing and rubber fluid sealing. Because of the pros like good effect of sealing, minimal tear and wear, less magnetic field and prolong life of service.

#### *2.5.4.4 Robotic industry*

In robotic industries nowadays for flexible joints are being controlled by hydroelectric control devises instead of ER fluidic joints technology which can perform much better function than the hydraulic-electric control. Engineers are designing and manufacture flexible joints which will have less volume, fast response time, minimal wear as well as tear, nimble, and which can be easily controlled by microcomputers. ER fluids can provide all these advantages over the hydraulic-electric controls.

#### *2.5.4.5 Commercial uses*

There are various commercial uses of the ER fluids and many uses are still undiscovered, in automotive industries the ER fluids are used in clutches, seat dampers, shock absorber, engine mount etc. Many other applications of the ER fluids are listed as follows: (a) Fluid flow via thin channel, (b) for friction instruments clutches, (c) servomechanism for impact and vibrator instruments, (d) pick-pick applications, (e) damping isolator, (f) automobile damping, (g) mounts for engine, (h) power transmission in robots, (i) machine tool artificial intelligence, etc. This list is not the final list because still now many uses of the ER fluid in various fields are yet to discover.
