Shear Thinning and Thickening Effect in Energy Dissipation Characteristics of STF Dampers

The shear-thickening fluid (STF) damper is a passive vibration-mitigation device. The damping force is passively regulated by shear-rate-dependent changes in STF viscosity during external excitation. The hysteretic behavior of the STF damper was examined using mechanical tests. The vibration-mitigation characteristics under different loading conditions were then analyzed. The viscosity distribution in the fluid domain at different shear rates was characterized through simulations. The effect of variations in STF viscosity on the hysteretic response was analyzed. A theoretical model was derived from the shear-rate distribution within the gap. These results show that the STF damper exhibits a passive, nonlinear rate-dependent response. The damping index α decreases with increasing velocity. Efficient energy dissipation over a broad frequency range can therefore be achieved. Finite element analysis further showed that the nonlinear damping-force response arises from shear-thickening and shear-thinning responses of the STF induced by the local shear-rate field in the gap. This study identifies a key finding: the peak damping force and hysteretic energy dissipation capacity are governed mainly by the viscosity of the STF in the shear-thinning regime, whereas viscosity changes in the shear-thickening regime mainly affect the initial damping-force growth rate.