The linear viscoelastic behaviour of magnetorheological elastomers is analysed in this work according to their formulation and working conditions. This study comprised both the synthesis of different magnetorheological elastomers and the strain and frequency sweep characterization under different magnetic fields and temperatures. The characterization was performed by a Physica MCR 501 rheometer from Anton Paar, equipped with a magnetorheologic cell 70/1T MRD. In the synthesis with a given elastomeric matrix, samples with different magnetic particle content are studied with two types of curing conditions: under the action of a magnetic field (anisotropic magnetorheological elastomers) and without a magnetic field (isotropic magnetorheological elastomers). The working conditions are excitation frequency, temperature and the applied external magnetic field. In this work, a new procedure to determine the linear viscoelastic behaviour is proposed; the loss factor is analysed in addition to analysing the storage modulus to determine the linear viscoelastic region of each sample. The results show that high temperatures and magnetorheological elastomers with higher volume fraction of magnetic particles restrict the linear viscoelastic behaviour of magnetorheological elastomers.

In this paper, it is shown that the MR damper’s power dissipation capacity is determined by the time spent in the pre- and the post-yield damping regimes. This time is determined by its design, by the MR fluid’s rheological behavior and by the type of movement applied to the MR damper. To analyze those working regimes, two types of movement with different amplitudes have been applied to the MR damper at different magnetic field intensities and excitation frequencies. The first movement is an imposed harmonic movement, and in the second, power controlled unrestrained movement is obtained. These unrestrained conditions are equivalent to those the MR damper handles in a real application. For all the analyzed conditions, the obtained results have shown that when a harmonic movement is imposed on the damper, the MR fluid is forced to work in the post-yield regime for the majority of the cycle. In contrast, when the unrestrained response is measured, the pre-yield behavior becomes more significant. As a result, for equal maximum displacement, the MR damper dissipates more power when a harmonic movement is imposed compared to the unrestrained movement.

The objective of this article is to determine the optimal flow mode in an MR damper to maximize its performance. Flow mode is one of the main design issues in an MR damper, as it determines the velocity profile and the pressure drop across the gap. In this research, two MR dampers were designed and manufactured with two flow modes: valve and mixed. The response of these two dampers was compared experimentally. Additionally, the experimental tests were correlated by theoretical results that were obtained considering the rheological behaviour of the MR fluid, the shear stress distribution in the gap, and the damper movement. Interestingly, the obtained results suggest that flow mode is not a significant parameter for determining the behaviour of a MR damper.