An experimental investigation into nonlinear dynamics of a magneto-rheological elastomer sandwich beam

An experimental investigation has been carried out on the nonlinear dynamics of a clamped–

clamped Magneto-Rheological Elastomer (MRE) sandwich beam with a point mass when

subjected to a point excitation. Three sets of experiments have been conducted namely for (i) an

aluminium beam, (ii) a MRE sandwich beam in the absence of a magnetic field and (iii) a MRE

sandwich beam in the presence of a magnetic field. An electrodynamic shaker was used to excite

each system and the corresponding displacement of the point mass was measured: for the third

experiment (iii), an array of magnets has been placed at various distances away from the centre of the

point mass to investigate the effect of changing stiffness and damping properties on the nonlinear

dynamical behaviour. An interesting feature for the third group is the beam point mass displacement

was no longer symmetric as the stiffness and damping of the system are increased when moving

towards the magnets. Both the first and second groups exhibited distinct nonlinear behaviour;

however, for the third group this work shows that for a low magnetic field the sandwich beam

exhibits two distinct resonance peaks, one occurring above and the other below the fundamental

natural frequency of the transverse motion, with the right one larger. For a larger magnetic field,

these peaks even out until the magnetic force was large enough that the hardening-type nonlinear

behaviour changes to a softening-type; a significant qualitative change in the nonlinear dynamical

behaviour of the system, due to the presence of the magnetic field, was observed.