This paper studies magnetic field control and velocity-activated magnetorheological shear thickening fluid
(MR-STF). High-concentration STF is composed of nano-sized silica particles suspended in a solvent polyethylene
glycol (PEG), and then micron-sized carbonyl iron particles of different mass fractions are added to the
STF to manufacture different MR-STF. The rheometer is used to study the viscoelasticity of all four samples.
The correlation between dynamic behavior and shear rate, angular frequency, and external magnetic field is
studied and discussed. In the lower angular frequency range, the loss modulus is slightly larger than the storage
modulus, and MR-STF behaves as a viscoelastic state. After the critical angular frequency, the storage
modulus decreases sharply, well below the loss modulus. MR-STF appears in a viscous state and a liquid state.
With the start of external field excitation, MR-STF is more inclined to MRF. Finally, the apparent viscosity and
shear rate of MR-STF are fitted. The results show that with the increase of magnetic induction strength, the
plastic viscosity coefficient of MR fluid increases, the flow characteristic index decreases, and the shear thinning
effect becomes more significant.