Magnetorheological elastomers (MREs) are solid analogue of the well-known smart material magnetorheological fluids (MRFs). They are composed of micron-sized ferromagnetic particles embedded in an elastomeric medium. Compared to MRFs which generally provide variable damping by variation of an applied magnetic field, MREs are capable of altering both stiffness and damping in the presence of an external magnetic field. The field-dependent viscoelastic properties of MREs can be effectively used for the development of MRE-based adaptive devices and structures to mitigate vibration semi-actively over a broad range of frequencies.
Extensive research studies have been carried out on the application of MREs in semi-active vibration isolators and absorbers. One emerging application is the use of MREs as part of structures, such as MRE-based sandwich beams and plates, with MRE acting as the core layer. MRE-based sandwich structures may be used for vibration control of light-weight flexible structures; however, their practical implementation is limited partially due to the weight of the integrated electromagnet having to be mounted onto these vibrating structures in order to activate the MRE layer. 
This research explores an alternative method of vibration control of flexible beam type structures via boundary conditioning using MRE at the support location. Having the MRE at the beam support rather than the core layer resolves the mounting issue of the electromagnet on the structure itself. This study explores a novel MRE-based control method on a cantilever beam, where the cantilever beam is approximately modelled using an overhanging flexible continuous beam. The overhang support is replaced with MRE support to control the rigidity of the boundary condition. The Rayleigh-Ritz method has been effectively used to formulate dynamic equations of motions of the beam with MRE support and to extract its natural frequencies and mode shapes. The MRE based adaptive continuous beam is then converted into an equivalent single-degree-of-freedom system for the purpose of control implementation, assuming that the system’s response is dominated by its fundamental mode. Three different types of control methods are explored including optimal control based on nonlinear mathematical programming technique (NLP), proportional-integral-derivative control, and on-off control. The performance of controllers is evaluated for three different loading conditions including shock, harmonic and random vibration excitations.
The proposed method of vibration control through boundary conditioning using MRE technology can provide essential guidance on the vibration control of light-weight structures using MREs without directly integrating heavy electromagnets to energize MREs. Such a design can be retroactively fitted onto an existing structure. Applications can include electronics packaging, where the electromagnet can be placed at a safe distance from electronics that are sensitive to a magnetic field.