TEMPERATURE DEPENDENCE OF MR FLUIDS

The rheological properties of MR fluids, MRF-132LD, are investigated under the steady shear and oscillatory shear for a range of operating temperatures from 20°C to 60°C. This was accomplished by using an advanced rheometer with the parallel-plate configuration. Under the steady shear, the Herschel–Bulkley model is used to model the rheology of the MR fluid. The corresponding parameters namely, τyd, K and n were determined at various temperatures, in an attempt to minimize the discrepancies between the experimental results and that predicted by the model. The results show that τyd, K and n all show decreasing trend with temperature. The results suggest that the MR fluid get "thinner" with increasing temperatures. Under the oscillatory shear, viscoelastic properties of the MR fluid were studied in the frequency sweep mode. The storage modulus, G′, decreases with increasing temperatures in both the linear viscoelastic region and the nonlinear viscoelastic region. In addition, two critical frequencies, ωcr and ωm, were identified in the latter region. They were found to decrease with increasing temperatures. Finally, thermodynamics are used to explain temperature dependence of MR properties.