Magneto-viscoelastic Behavior of Magnetorheological Elastomers and Semi-active Control of Smart Structures Using Magnetorheological Isolation System
Magnetorheological elastomers (MREs), as one of smart composites, exhibit characteristics of both particle reinforced composites and magnetorheological materials. Their mechanical properties (e.g., stiffness and damping) can be tailored rapidly, continuously and reversibly with applied magnetic field.
In this research MREs specimens have been fabricated, with their micro-structures and dynamic properties subsequently characterized via scanning electron microscope (SEM) and dynamic mechanical analysis (DMA). The magneto-viscoelastic behaviors have been systematically studied under different external magnetic fields, excitation frequencies and strain amplitudes.
A new linear GMM (Generalized Maxwell model)-based magneto-viscoelastic model of MREs is proposed and investigated under small strain. Further, a nonlinear magneto-viscoelastic constitutive model of MREs is developed under large strain. The model predicts the frequency-, amplitude-, and magneto-dependent behaviors of MREs. The internal damping mechanisms are considered by multiplicative decomposition of the deformation gradient and magnetic induction into elastic and inelastic parts. The energy dissipation is assumed to occur due to the frequency- and amplitude-dependent mechanical viscoelasticity as well as the frequency-, amplitude-, and magneto-dependent magnetic-viscoelasticity. Constitutive laws for material behaviors and evolution equations are derived that agree with the laws of thermodynamics. Both mechanical force-induced Payne effect and magneto-induced Payne effect are considered for the amplitude-induced nonlinearities by the introduction of internal state variables integrated in the model, which are interpreted as phenomenological measures for the current state of the filler network. The parameters of the proposed constitutive model are identified by experimental data. Then the shear storage and loss moduli are analyzed and compared with the experimental results to validate the model’s effectiveness.
Instantaneous-minimum-input-energy-based semi-active control algorithm (IMIEKC) for the base isolation system with both stiffness and damping varying simultaneously has been proposed and applied to MREs-based smart isolation system. The algorithm has been demonstrated by numerical simulations and compared with other methods to indicate it as an efficient semi-active control method. The passive controls and IMIEKC-based semi-active controls of a 5-story building with both linear and nonlinear magneto-viscoelastic models-based isolation systems have been demonstrated and analyzed to evaluated the corresponding control performance.