B Questions regarding Magnetorheological fluids

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Magnetorheological fluids (MR fluids) respond to external magnetic fields rather than electric currents, requiring a setup like a Helmholtz Coil to generate the necessary magnetic field. When exposed to a magnetic field, MR fluids significantly increase their viscosity, becoming viscoelastic solids, with the yield stress adjustable by varying the magnetic field intensity. This property allows for precise control in applications that require force transmission. MR fluids differ from ferrofluids, as they contain larger particles that do not remain suspended through Brownian motion. Understanding these distinctions is crucial for effectively utilizing MR fluids in projects.
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Hello, has anyone worked with magnetorheological fluids before?

I plan on creating one for a project by using carbonyl iron powder, a surfactant, and some oil. I have heard that when subject to a current, these liquids basically become solids. However, I am not sure if they become complete solids. How much more viscous, or how much more solid do these liquids become when subject to a current?

Also, just to confirm, the viscosity should increase as the current increases as well, right?

Thanks!
 
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dliu1004 said:
Hello, has anyone worked with magnetorheological fluids before?

I plan on creating one for a project by using carbonyl iron powder, a surfactant, and some oil. I have heard that when subject to a current, these liquids basically become solids. However, I am not sure if they become complete solids. How much more viscous, or how much more solid do these liquids become when subject to a current?

Also, just to confirm, the viscosity should increase as the current increases as well, right?

Thanks!

I haven't used them before, but according to a couple articles that I found with a Google search, they respond to external magnetic fields, not to currents flowing through them. You would need to use something like a Helmholtz Coil or similar arrangement to generate a B-field through your material.

A magnetorheological fluid (MR fluid, or MRF) is a type of smart fluid in a carrier fluid, usually a type of oil. When subjected to a magnetic field, the fluid greatly increases its apparent viscosity, to the point of becoming a viscoelastic solid. Importantly, the yield stress of the fluid when in its active ("on") state can be controlled very accurately by varying the magnetic field intensity. The upshot is that the fluid's ability to transmit force can be controlled with an electromagnet, which gives rise to its many possible control-based applications. Extensive discussions of the physics and applications of MR fluids can be found in a recent book.[1]

MR fluid is different from a ferrofluid which has smaller particles. MR fluid particles are primarily on the micrometre-scale and are too dense for Brownian motion to keep them suspended (in the lower density carrier fluid). Ferrofluid particles are primarily nanoparticles that are suspended by Brownian motion and generally will not settle under normal conditions. As a result, these two fluids have very different applications.
https://en.wikipedia.org/wiki/Magnetorheological_fluid

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