This article presents a novel model to portray the behavior of magnetorheological elastomer in oscillatory shear test. The dynamic behavior of an isotropic magnetorheological elastomer is experimentally investigated at different input conditions. A modified Kelvin–Voigt viscoelastic model is developed to describe relationships between shear stress and shear strain of magnetorheological elastomers based on input frequency, shear strain, and magnetic flux density. Unlike the previous models of magnetorheological elastomers, the coefficients of this model, calculated by nonlinear regression method, are constant at various harmonic shear loads and different magnetic flux densities. The results show that the new phenomenological model can effectively predict the viscoelastic behavior of magnetorheological elastomers. Also, the results demonstrate that the trend of shear storage modulus of magnetorheological elastomer based on the frequency is nonlinear from 0.1 to 8 Hz, which is predicted by the present model. The proposed model is beneficial to simulate vibration control strategies in magnetorheological elastomer base devices under harmonic shear loadings.

Tension-compression operation in MR elastomers (MREs) offers both the most compact design and superior stiffness in many vertical load-bearing applications such as MRE bearing isolators in bridges and buildings, suspension systems and engine mounts in cars, and vibration control equipment. It suffers, however, from lack of good computational models to predict device performance, and as a result shear-mode MREs are widely used in the industry, despite their low stiffness and load-bearing capacity. We start with a comprehensive review of MREs modeling and their dynamic characteristics, showing previous studies have mostly focused on dynamic behavior of MRE in the shear mode, though the MRE strength and MR effect are greatly decreased at high strain amplitudes, due to increasing distance between the magnetic particles. Moreover, the characteristic parameters of the current models either frequency, strain or magnetic field are constant; hence, new model parameters must be recalculated for new loading conditions. This is an experimentally time consuming and computationally expensive task, and no models capture the full dynamic behavior of the MREs at all loading conditions. In this study, we present an experimental setup to test MREs in a coupled tension-compression mode, as well as a novel phenomenological model which fully predicts the stress-strain behavior of the as a function of magnetic flux density, loading frequency and strain. We use a training set of experiments to find the experimentally derived model parameters, which can predict by interpolation the MRE behavior in the relatively large continuous range of frequency, strain and magnetic field. We also challenge the model to make extrapolating predictions and compare to additional experiments outside the training experimental data set with good agreement. Further development of this model would allow design and control of engineering structures equipped with tension-compression MREs and all the advantages they offer.

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The rail irregularities and wheel-rail interactions in a train running at high speeds may result in large-amplitude vibrations in the train's car body and affect passengers by reducing ride comfort. The train suspension systems have a crucial role in reducing the vibrations and improving ride comfort to an acceptable level. In this context, an exclusive magneto-rheological (MR) damper with a favorable dynamic range was designed and fabricated. The MR dampers were installed in a high-speed train's secondary lateral suspension system, replacing passive hydraulic dampers to mitigate vibration of the car body and keep the ride comfort level in a proper condition. A unique full-scale experimental investigation on the high-speed train equipped with MR dampers was carried out to evaluate the MR damper functionality in a real operating situation. The full-scale roller experiments were conducted in a vast range of speeds from 80 to 350 km/hr. At each speed, different currents were applied to the MR dampers. The car body dynamic responses were collected with accelerometers and displacement sensors mounted on the carriage floor and sidewall. To investigate the ride quality of the high-speed train, ride comfort indices and car body rolling motion are evaluated. Ride comfort indices under various train operating conditions are calculated through Sperling and UIC513 rules. This study reveals that the designed MR dampers effectively reduce the car body's rolling motion. According to Sperling ride comfort index, the car body vibration was "clearly noticeable" at some running speeds when adopting the MR dampers, but it was not unpleasant. Besides, a "very good comfort" was achieved according to the UIC513 ride comfort criterion. Also, no train instability was whatsoever observed at high speeds.INDEX TERMS High-speed train, MR damper, full-scale experiment, ride comfort index, rolling motion, secondary suspension system.