Smart Nanofluid Viscous Dampers (II)

Smart Nanofluid Viscous Dampers (II)

Nanofluid dampers feature a force-velocity curve described by a dual nonlinear exponent, in which an exponent with α > 1 describes the low-velocity range while α < 1 describes the working-velocity range, typical of deformations induced by earthquake excitations. This property can be used in bridge systems to significantly decrease the inner pressure of dampers and the wear on oil seals, which increases the durability of the dampers. This study attempts to use the shear thickening and thinning characteristics of a nanofluid and a damper with a simple solid piston head. This study aims to show that the performance of the damper can be adjusted by changing the formula and concentration of the nanofluid to achieve dual-nonlinear-exponent force-velocity mechanical properties in the damper. The results of this study indicate that (1) the initial viscosity of the nanofluid is greater than that of the corresponding pure polypropylene glycol (PPG) fluid；(2) the initial viscosity is proportional to the PPG polymer chain length and fluid concentration；(3) the shear thickening, cluster effect, and maximum viscosity are all proportional to fluid concentration；(4) as the temperature increases, the viscosity corresponding to shear strain rate decreases, although the shear strain rate corresponding to relatively low and high viscosities increases with temperature；and (5) the area enclosed by the hysteresis loop for the nanofluid damper is proportional to frequency and maximum velocity. Finally, after temperature correction, the force curve and regression equation of the nanofluid damper show the mechanical characteristics associated with a dual nonlinear exponent.