Modelling, Characterisation and Development of New Magnetorheological Materials With Enhanced Vibration Control Performance K. Sapouna, Supervisors: Y.P. Xiong and R.A. Shenoi Faculty of Engineering and the Environment, University of Southampton, UK Fluid Structure Interactions Research Group FSI Away Day 2012 Background Magnetorheological elastomers (MRE) are solid materials composed of magnetisable (usually iron) particles suspended in a low permeability carrier matrix (usually rubber). They are the solid equivalent of magnetorheological fluids that already find applications in vibration isolation systems. In the presence of an external magnetic field the particles are magnetized and form chains while trying to align in the direction of the field. As a consequence the viscoelastic behaviour of the material can be controlled. In vibration control system design, materials with dynamically variable stiffness and damping, like magnetorheological elastomers, could be useful tools. When an external field is applied to the MR elastomer during curing, the filler particles tend to align parallel to the direction of the magnetic field forming anisotropic elastomers. On the other hand, when the elastomer is cured without the presence of the field the particles are randomly dispensed inside the matrix forming an isotropic material. Further Work  Manufacture natural rubber MRE  Investigate the dynamic properties of MRE under multi loading conditions  Derive a constitutive equation model for both types of MRE  Design and manufacture a semi active vibration isolation device and the appropriate control system Modelling Methodology Aims  Investigate the mechanical characteristics of the MR elastomers  Develop a mathematical model capable of predicting the response of the material  Manufacture a vibration isolator prototype device for marine applications MR elastomers, are governed by a nonlinear stress-strain relationship with a complex modulus of elasticity that depends weekly on the frequency and strongly on the applied magnetic field. To model the material the simple Kelvin Voight viscoelastic model is used where both stiffness and damper are amplitude, frequency and magnetic field dependent. Figure 1: Kelvin Voight viscoelastic model Where and e=strain amplitude, ω=2 π f, B= intensity of the magnetic field Transmissibility of a SDOF system Material Characterisation Figure 2: Modulus E of anisotropic MRE at zero field and 0.3T magnetic field Figure 3: Damping factor tand of anisotropic MRE at zero field and 0.3T magnetic field The mechanical properties characterization of silicon MR elastomers were performed under static and dynamic loading conditions for a range of frequencies and amplitudes following the directions of British standard BS ISO :2005 for compression loads in rubber. Figure 7: Transmissibility curves for anisotropic and isotropic MRE at zero and 0.3T field Figure 4: Damping factor tand of isotropic MRE at zero field and 0.3T magnetic field Figure 5: Modulus E of isotropic MRE at zero field and 0.3T magnetic field Figure 6: Transmissibility curves for isotropic MRE at different strain amplitudes F1 F2 M This project is funded by: Conclusion  Isotropic MREs have a higher MR effect than anisotropic MREs  When the field is applied the natural frequency and damping factor changes  Transmissibility and damping factor depends heavily on the amplitude of the applied force and thus a nonlinear model is needed