Magnetorheological Elastomers (MRE) are composed of a ferromagnetic filler, micron sized iron particles, in an elastomer matrix. When a magnetic field is applied to an MRE, the iron particles develop a dipole interaction energy, which results in the material displaying a field dependent modulus. MRE materials have received attention in the last decade due in part to their potential application in semi-active vibration isolators. However, compared to MR fluid dampers, few applications of MRE materials have been developed, and no commercial devices are available. This paper describes the development of an MRE based isolator. Unique to this design is the introduction of a field induced modulus bias via a permanent magnet, which can be offset with a current input to the electromagnetic control coil. If the field bias is not significant enough to saturate the iron particles then an appropriately directed input current can also further increase the field induced modulus. Such a Biased Magnetorheological Elastomer (B-MRE) could be useful for applications where the designer wishes to decrease the system stiffness, something that has not been addressed by other MRE based devices.
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