The response of a magneto-rheological (MR) damper is often characterized by a force-velocity response plot from a sinusoidal input. These plots are created in a shock dynamometer in which one end of the damper is attached to a load frame and the other end is moved in a sine wave with a given peak velocity and frequency. The peak damper force from a series of sine wave tests of varying peak velocity is measured and plotted as discrete data points versus the relative velocity across the damper. This is a standard procedure for characterizing passive shock absorbers in the automotive industry. The validity of this characterization relies on the assumption that the damper is dominantly a velocity-dependent device. However, it is well-known that the internal dynamics of the damper depend not only on the velocity of the input, but also the frequency of the excitation. Therefore both velocity and frequency should be considered as independent parameters to achieve a more complete characterization of a MR damper's response under sinusoidal excitation. This paper investigates the dependence of the force response to both peak velocity and frequency, for several different MR dampers from a wide variety of applications. By treating the velocity and frequency as two independent parameters, a complete characterization of the damper's response under sinusoidal excitation can be characterized. After investigating how damper force varies with both peak velocity and frequency, efficient test procedures are recommended for future MR damper characterizations.

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