Grant: Research Tools and Instruments

Magnetorheological (MR) materials are advanced materials whose rheological behavior can be controlled using the applied magnetic field. MR materials can be in liquid (MR fluids) or solid (MR elastomers) states. MR fluids are typically composed of micron-sized magnetically polarizable particles (typically carbonyl iron particles) dispersed in a carrier medium such as mineral or silicone based oils. When exposed to a magnetic field, these magnetic dipoles align themselves along the lines of magnetic flux causing the MR fluid to change from a free-flowing viscous fluid to a semi-solid with controllable yield strength in the order of milliseconds. MR fluids can also be confined in an absorbent matrix such as sponge by capillary action to form MR fluid foams. MR elastomers are rubber-like materials (magnetic particles are suspended in a solid polymeric medium) whose modulus can be adaptively controlled. The ability of MR materials to provide simple, quiet and rapid-response interfaces between electronic controls and mechanical systems have made them attractive materials for new generation of high bandwidth semi-active devices which can be efficiently used to improve the performance of adaptive structural systems under unpredictable environmental changes. MR materials can be effectively utilized to control vibration and structure-born noise in wide range of frequencies and thus allow to design next generation of ground, aerospace and marine vehicles which are cost-effective and reliable while meeting the standards for passenger comfort. To effectively design these MR-based adaptive structures, fundamental understanding of the dynamic behaviour of MR materials under varying applied magnetic field, frequency and amplitude of excitations as well as temperature is of paramount importance. Considering this, the proposed equipment is needed to conduct fundamental and systematic study on the behavior of all types of MR materials under varying intensities of magnetic field and varying external excitations in both pre-yield and post-yield regions. The requested magneto-rheometer is a unique device to characterize the behavior of MR materials under wide range of excitation frequencies and amplitudes, and temperature under the application of external uniform magnetic field intensities which can reach up to 1 Tesla. The linear and nonlinear viscoelastic properties of MR materials as well as their viscoplastic behavior in post-yield region can be investigated using the proposed equipment. This will eventually lead to development of constitutive models that can accurately characterize the rheological behavior of MR materials in different operating regions and thus can be effectively used in modeling of novel MR-based adaptive structures under unpredictable external excitations.