Magnetic Field-Dependent Normal Force of Magnetorheological Gel

Magnetorheological gel (MRG) is a new kind of MR material, and it can be regarded as the analogue of MR fluid. In this study, a MRG sample based on a polyurethane matrix was fabricated. The normal force of MRG was investigated by using an advanced commercial rheometer under rotational and oscillatory shear modes. The influence of time history, strain amplitude, frequency, shear rate, and temperature in the presence of a variable and constant magnetic field on the normal force of MRG was systematically studied. The experimental results indicated that the magnetic field has a greater impact on the normal force of MRG, and the increment of magnetic field enhanced the normal force obviously. However, the other factors in the presence of a constant magnetic field only have weak effects on the normal force. This behavior can be regard as the magnetic field-dependent normal force, and the mechanism of interaction between the magnetic field and normal force was investigated by microstructure analysis.