Characterization of Fluid Viscous Dampers for Shock Excitation

Fluid viscous dampers (FVDs) are especially attractive for enhancing the performance of the structure subject to dynamic excitation because they not only reduce the deformation demand but also the force demand. The control of transient response of a structure to shock excitations is of interest to various engineering applications. The loading is, in general, made up of a single major impulse of arbitrary form (Belytschko and Hughes (1983), Chopra (1997), Clough and Penzien (1993)). The shock can produce large transient response, which is very important in design of certain classes of structural system. The use of FVDs can considerably reduce the response of such structures. This paper presents the experimental results for characterization of fluid viscous dampers subjected to half-cycle sine shock excitations. The main purpose of shock tests conducted on the fluid viscous dampers was to evaluate the shock parameters and response at the damper piston end. The research program for shock testing of fluid viscous dampers made use of the two sets of nonlinear fluid viscous dampers with different damper exponent (α) and coefficient of damper (cα), supplied by M/s Taylor Devices, USA. The dampers were tested on a pendulum-type shock test facility, wherein the shock parameters are varied by changing the drop height (DH) of the stand and the rubber thickness (RT) of a pulse shaper attached to the impact point- the buffer mass. The experimental investigations indicates that, the damper exponent (α) of a nonlinear fluid viscous damper changes depending on the nature of excitation (sinusoidal or shock). However, the values of damper exponent for the entire range of shock tests conducted on dampers do not vary significantly, indicating that for all the ranges of shock tests conducted, the value of damper exponent remains fairly constant. Further, it is concluded that practical use of such nonlinear fluid viscous dampers for various ranges of shock excitations is feasible due to the relative constant values of the damper properties under such excitations.