What is it and how do they work? You may very well ask ! A typical MR fluid consists of 20% 40% by volume of relatively pure, soft iron particles, typically 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.
MAGNETO RHEOLOGICAL
SHOCKShock ABSORBER FLUID Magneto Rheological Absorber Fluid
Issue 19/2018 Magneto Rheological (MR) fluids are materials that respond to an applied field with a dramatic change in (MR Fluid, not Mister Fluid) their rheological behaviour. The essential characteristic these fluids is their ability to reversibly change SHOCK ABSORBER,of SUSPENSION, BRAKES, TOWBARS ALIGNMENT SPECIALISTS from a free-flowing, linear, viscous liquidAND to WHEEL a semi-solid with controllable yield strength in milliseconds when to a magnetic field.work? What is exposed it and how do fluid they Magneto Rheological is a nonNewtonian fluid. These types of liquids You change may very ! theirwell state ask depending on the pressure and force applied to them.
A typical Magneto A typical MR fluidRheological consists (MR) of Shock 20% Absorber 40% byfluidvolume of relatively pure, soft iron particles, typica consists of soft iron particles, typically 3–5 microns in Fig. 2a microns, suspended carrier diameter, suspendedin in aacarrier liquidliquid such as such mineralas mineral oil, synthetic oil, water, or glycol. A var oil or synthetic oil. A variety of proprietary proprietary additives similar to thoseadditives found in commercial lubricants are commonly added to disc like those found in commercial lubricants help to keep gravitational settling and promote particle suspension, enhance lubricity, modify viscosity, and inhibit particles suspended, enhance lubrication, change viscosity, and reduce wear.
Fig. 2b Fig. 2c Magneto Rheological (MR) fluids are materials that respond when they meet a magnetic field and change Magneto Rheological (MR) fluids are materials that respond to an applied field with a dramatic ch small moving parts. It is based on the MR Fluid, passing their behaviour. The essential characteristic of these theirIntroduced rheological behaviour. The characteristic these fluids isfield. theirrheological ability to reversibly throughSTS, aof regulated forability the first time infrom 2002, on GM's Cadillac Seville the so magnetic called magneto fluids is their to reverse a essential free-flowing fromsuspension a free-flowing, viscous liquid to semi-solid with controllable yield strength in millis viscous liquid to a semi-solid controlled strength system is linear, slowly with but surely catching on.inaAlthough it has been made on several When the magnetic coil ofavailable the damper system, isvehicles, not milliseconds (as shown in Figure 1). when exposed to a magnetic field. energized – the oil has a high viscosity and the iron
including Buick and Chevrolet, the system has been made famous by German manufacturer Audi, with its particles move about randomly, acting like a regular introduction on the TT and R8. In Australia, M.R. units are fitted to the HSV Commodores. damper fluid (as shown in Figure 2a).
However, when the system is charged the magnetic field
What sets it apart from other suspension systems is the fact that it the lacks any electro-mechanical valves and is applied, particles align into fibrous structures, withit low viscosity in Figure 2b). This restricts the a basically has no small moving parts. Instead, the suspension is based(as onshown a magneto rheological fluid (MR), movement of the fluid, and the velocity of the piston. The type of smart fluid, as it is called, which reacts to a magnetic field. magnetic field only needs to be generated in the piston of the damper so it only effects the fluids viscosity as it passes through. This creates greater efficiencyWhen and the with micrometer-sized magnetic particles. need for only a relatively small magnetic device.
MR is in fact a carrier fluid, usually oil, which is filled subjected to a magnetic field, the magnetic particles inside increase the fluid's viscosity, rendering it en the coil of the damper the system MR fluid, is notof four magneto rheological struts or shock viscoelastic solid. system, Usually,which a MR contains suspension is made rgized –absorbers, the so called "off" set position the MR fluid is notunit magnetized a sensor and an– electronic control (ECU). and particles inside, distributed randomly, allow the fluid to move freely, ng like a regular damper fluid. Fig. 1
Introduced the isfirst time in and 2002, on GM's wever, when thefor system turned "on", a charge whichCadillac creates a Seville STS, the so called magneto rheological Introduced for the first time in 2002, on General Motor gnetic field is applied, theisparticles become energized and align vehicles, the so-called MR suspension system is slowly suspension system slowly but surely catching on.into Although it has been made available on several ve becoming main stream. Although it has been made ous structures, usually perpendicular on the direction of the magnetic including Buick and Chevrolet, the system been made famous by German manufacturer Audi, wit available on several vehicles, the system has beenhas made x. This restricts the movement of the fluid, proportional to the power and famous byon Audi, introduction the TT and R8. introduction thewith TTitsand R8. InonAustralia, M.R. units are fitted to the HSV Commodores. nsity of the magneticM.R. field according to the velocity the piston. In Australia, units are optional fitment to theof Holden Special Vehicles (HSV).
What What sets sets it apart othersuspension suspension systems it apartfrom from other systems is the is the fact that it lacks any electro-mechanical valves fluid (
anks to thefact ECU in accordance withvalving the riding stylenochosen byFig. the3 MR Suspension System thatand it lacks any regular style and has basically has no small moving parts. Instead, the suspension is based on a magneto rheological ver, the system adjusts the MR system once every millisecond. Sensors monitor road and vehicle type of smart fluid, asmodifies it is called, which characteristics reacts to a magnetic field. times per second. ditions, while the controller the damping up to one thousand
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instance, case, the driver can choose betweenis"Normal" and "Sport" programs by flipping a MR is in inAudi fact TT's a carrier fluid, usually oil, which filled with micrometer-sized magnetic
particles. Wh
m adjusts the MR system once every millisecond. Sensors monitor road and vehicle the controller modifies the damping characteristics up to one thousand times per second.
Audi TT's case, the driver can choose between "Normal" and "Sport" programs by flipping a stem reacts accordingly, providing different damper response.
MAGNETO RHEOLOGICAL
suspension system allows for a better ride due to the flat and stable ride it ensures. The MR r the action of each wheel to be smoothened and isolated. The system can be integrated with y control to enhance stability on gravel, and slippery road surfaces. Thanks to the ECU's Issue 19/2018 force control and high bandwidth for fast R system allows for a wide range of damping
SHOCK ABSORBER FLUID SHOCK ABSORBER, SUSPENSION, BRAKES, TOWBARS AND WHEEL ALIGNMENT SPECIALISTS
t that magnetic polarization is not affected by temperature, the performance of MR-based Controlled by the vehicle Electronic Control Unit (ECU) If you looked at the fluid under high magnification in the ely insensitive to temperature over a broad temperature range (-40 degrees Celsius – 105 and the sports or comfort ride chosen by the driver, the absence of a strong magnetic field it would be similar in system adjusts every millisecond. Sensors monitor road appearance to Figure 4a. Once a strong magnet field and vehicle conditions, while the controller modifies the the iron would appear uniformly liquid helps the iron or iron oxide particles to stay suspended.is applied This allows theparticles particles dampening characteristics. orientated (as shown in figure 4b).
er ith minimal clumping when the MR fluid is stirred or poured. It also allows the particles to The use of a MR suspension system allows for more Note: This style of suspension is found on many of mensions tunable when aride magnet is brought near the mixture. In this way the particles can orient conditions. The system can allow for each the high performance super cars and luxury style the magnetic field and peaks can form. rates if needed to wheel to be dampened at individual vehicles. As it is controlled by the vehicles ECU there
enable the vehicle’s stability on gravel, and slippery road is a chance that some programming exists to control surfaces do somagnetic with a fastfield response. its behavior. should be observed if replacing it uid is exposed to aand strong the iron or iron oxide particles alignCaution with the or removing it from the vehicle as vehicle performance charging the fluid is not affected temperature nd form a The network thatoftraps the carrier fluid. by This is sort of likemay a large group ofand people be affected warning codes may be lodged and will perform over a broad temperature range (-40 in the ECU. Contact the vehicles manufacturer to t becomesdegree very difficult one person to move very far. This causes the bulk fluid to Celsius –for 105any degrees Celsius). resource correct specifications before performing work a solid. on vehicles with this suspension.
4a Fig. 4b an MR fluid underFig. high magnification in the absence of a strong magnetic field it would stration on the left. There you can see individual iron oxide particles suspended in a viscous ou brought a strong magnet near the MR fluid the individual iron oxide particles would agnetic field and clump together like the image on the right.
e of unit fails, they are not repairable.
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