LINEAR VISCOELASTICITY OF MR FLUIDS: DEPENDENCE ON MAGNETIC FIELDS

Abstract

The paper presents investigation of dynamic properties of MR fluids by using a rheometer with parallel-plate geometry. The sample is reduced iron powder based MR suspensions. Linear viscoelastic properties of such sample, which can be variably controlled using a magnetic field, are obtained and summarized based on oscillatory tests. Four field-induced regimes, I, II, III, and IV, are found in the system, which are defined by three critical field strengths: BC1< BC2< BC3. MR fluids in regime I through IV experience four typical structural convolutions: coexisting of particles and random chains; coexisting of chains and random clusters; coexisting of clusters and chains; stable clusters. Such results are in good accord with experimental results achieved by Liu's group using light scattering techniques.