The concept of functional systems based on the smart fluids was introduced by the Carlson et.al4 on ER based composite structures. Don and Coulter5 worked on the dynamic behaviour of the ERFluid based adaptive structures using the very popular vibration theories namely the Ross,Kerwin Unagar(RKU), Mead and Markus(MM) models found the most effective ability of two theories for the ERFuid based structural modelling.Rahn and Joshi6derived the dynamic models for the ER structures on the basis of viscoelastic sandwich beam. The instability of all modes ensured by using Lyapunov theory, the response of the ERFluid filled cantilever beam stability condition shown as well.Yalcintas and coulter7found the transverse vibrations of simply supported three layered ERFluid sandwich beam under sinusoidal actuation, the results between experimental and optimum electric field is required to reduce the vibration of the structure in each excitation frequency. Recently, the materials with controllable rheology by semi active means such as electrorheological(ER)8and magnetorheological(MR)9 fluids have drawn much attention.
These fluids comprise micron sized particles sensitive to electric or magnetic fields, which are randomly suspended in the fluid. Whenever these fluids are subjected to an magnetic/electric field, which are randomly suspended in magnetic field. The particles are arranged in a uniform way this may leads to changes in the viscosity and converting its state from solid like gel form. Consequently, the rheological properties of these fluids changes in mechanical properties due to external excitation such as damping and stiffness of structure simulateneousaly.Whenever the external excitation is removed, the solid state gel returns to the original liquid form and the characteristics of the fluid are restored. The MR/ER adaptive beam consists of three layered structures comprising two elastic layers and core is made up of MR/ER material.
Whenever under the actuation of external magnetic/electric field, the mechanical properties of MR/ER material and the dynamic characteristics of the sandwich beam accordingly changes in significant way. Due to the shear deflection of the beam, the MR/ER core material undergoes a shear strain. A damping dependent potential energy stored in the core layer and therefore a considerable amount of vibrational energy is to be dissipated. The adaptive structures incorporating MR materials, have been analyzed by many researchers in recent years. Sun et al.10 presented the dynamic behaviour of an adaptive beam based on MR materials in the pre-yield regime. An MRFluid sandwich adaptive beam was fabricated and tested and both studies shows how vibration can be minimized under different magnetic field conditions.
Yeh and Shih 11 worked on dynamic response of simply supported adaptive beam subjected to the axial harmonic load and found natural frequency, loss factor, dynamic instability, buckling load etc.Rajamohan et al.12 developed the governing equation of a multi-layer beam structure employing MR fluid in the pre-yield regime by using the finite element and the Ritz methods. The validation of finite element results good agreement with those of Ritz and experimental methods.Nayak et al.13, 14 studied the dynamic behaviour of a non-rotating and rotating three-layered symmetric sandwich beam with MR viscoelastic core and conductive skins.Babu et al.15, 16 analyzed the dynamic performance of tapered composite sandwich plate with fully and partially treated MR elastomers core.