Shear Rheological Properties of Polyurethane-Based Magnetorheological Gel

Polyurethane-based magnetorheological gels (MRG) with different mass fractions of carbonyl iron powder (50%,70%,80%) were prepared. The static and dynamic shear rheological properties of the MRG with a wide shear stress range under different magnetic induction intensities, shear rates and strain amplitudes were studied, and Herschel-Bulkley constitutive model parameters were identified based on the test results. The results show that the shear stress of MRG with 80wt% carbonyl iron powder had the widest range, and megnetorheological effect was the most obvious. The yield shear stress of MRG with 80wt% carbon iron powder increased with the magnetic induction intensity; the kinetic viscosity at different magnetic induction intensities decreased with the increase of shear rate. The MRG was a non-Newtonian fluid with yield shear stress and shear thinning characteristics, and its rheological properties satisfied Herschel-Bulkley shear thinning model. The storage or loss modulus was greatly affected by the shear strain amplitude and magnetic induction intensity, but had a weak dependence on the frequency. The megnetorheological effect and linear viscoelastic critical strain amplitude both increased with the increase of magnetic induction intensity. The effect of magnetic induction intensity on normal stress was more significant than that of shear rate and shear strain amplitude.