Electrorheological (ER) and magnetorheological flow mode dampers can exhibit biviscous damping behavior. Such behavior is characterized by a high damping pre-yield region for low velocities, with a transition to a relatively lower post-yield damping, once the damper force exceeds the static yield force of the damper. The biviscous damping behavior is typically the result of leakage, that is, a second path of Newtonian flow in addition to the Bingham plastic flow through the ER or MR valve. We experimentally demonstrate such bilinear damping behavior in a monotube ER shock absorber. Leakage is typically introduced to smooth the force response of the damper as the damper undergoes transitions through the low velocity. The ER fluid is typically assumed to behave as a Bingham plastic fluid. Thus, two perspectives are examined for modeling damping performance of the ER monotube shock absorber. First, the quasisteady Bingham plastic analysis is coupled with a mechanical analysis of the leakage effects. Second, a biviscous constitutive perspective is described that allows the leakage effects to be described as an apparent pre-yield viscosity of the ER fluid. Both perspectives prove to be useful in describing damping performance of the ER monotube shock absorber.

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