Dynamic response of a MRE sandwich structure under a non-homogenous magnetic field

A viscoelastic layer improves the response of a sandwich structure under dynamic loading. Through integration of a magneto-sensitive elastomer core, the adaptability of the structure over a wider frequency can be achieved. The current work focuses on the influence of a non-homogeneous magnetic field on a magnetorheological elastomer (MRE)-based sandwich cantilever beam. The dynamic response of the structure is measured using the impact hammer test as per the ASTM E-756-05 standard. Results revealed that the fundamental natural frequency of the MRE sandwich beam is a function of the intensity and the location of the non-homogenous magnetic field. The fundamental natural frequency is reduced as the magnitude of the magnetic flux density is increased or the magnetized region is shifted towards the fixed end. This unique response of the MRE sandwich beam under a non-homogenous magnetic field is an exception to the usual stiffness-enhancing behavior of a MRE. To study this disparity, we independently investigated the contributions by the localized stiffness enhancement and the deflection due to magnetic pull. The effect of the localized overall stiffness enhancement on the overall stiffness of the sandwich beam is investigated using modal analysis in ANSYS to analyze the variation in the fundamental frequency. The contribution due to magnetic pull is studied by performing an experimental modal analysis on an equivalent ferromagnetic cantilever beam deflected under the influence of a magnetic field. By comparing the experimental results and the corresponding investigation on the influencing factors, we confirmed that magnetic pull induced under non-homogenous magnetic field is an important parameter that significantly contributes to the dynamic response of a MRE sandwich beam.