Article

Shear-thinning effects in annular-orifice viscous fluid dampers

Department of Civil Engineering, National Cheng Kung University, 臺南市, Taiwan, Taiwan
Journal- Chinese Institute of Engineers (Impact Factor: 0.21). 03/2007; 30(2):275-287. DOI: 10.1080/02533839.2007.9671254

ABSTRACT The number of construction projects using viscous fluid dampers for the purpose of seismic energy dissipation has been increasing in recent years. Usually, resisting forces provided by a viscous fluid damper are nonlinearly related to the damper op-eration velocity. In the current study, the mechanism of the nonlinear behavior is studied. It is found that the fluid shear rate in the orifices of a damper is high enough to cause shear thinning of the fluid, that is, the non-Newtonian behavior of the fluid must be considered to capture the viscous damper's non-linearity. Carreau's equation giving the shear-thinning relationship between fluid viscosity and shear rate is em-ployed in a finite element model. The model is used to calculate the fluid dynamics in viscous dampers and the calculated results successfully explain the nonlinear behavior. Effects of the damper geometry and the fluid viscosity on the damper non-linearity are also tested and discussed. Again, the trend shown in experimental results can be fully explained by the shear-thinning concept. In addition, the behavior of a damper operated at ultra high velocity is addressed.

1 Follower
 · 
332 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a study of the rheological properties of shear thickening fluids (STF) and the performance of a viscous damper filled with an STF by performing a cyclic loading test. In the rheological test, the STF samples were prepared by blending nanoscale fumed silica powder with polypropylene glycol fluid in different weight fractions. Using a strain-controlled rheometer with a cone and plate tool, both steady and oscillatory state experiments were performed and the rheological properties of the STF were observed. Experimental results showed an abrupt increase in complex viscosity beyond a critical dynamic shear strain rate [Inline formula]. In this study, a hydraulic steel tube was filled with an STF to develop an innovative passive damper device. The STF-filled damper performance test showed that the area and shape of hysteresis loops can vary with different loading conditions. The analytical models studied and a numerical approach showed that STF-filled dampers are potentially useful in practical engineering applications.
    Journal- Chinese Institute of Engineers 05/2014; 37(8):983-994. DOI:10.1080/02533839.2014.912775 · 0.21 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this article is to study and characterize experimentally two magneto-rheological dampers with short- and long-stroke, denoted hereafter as MRD-S and MRD-L. The latter was designed to improve the Earthquake performance of a 21-story reinforced concrete building equipped with two 160 ton tuned pendular masses. The MRD-L has a nominal force capacity of 300 kN and a stroke of ±1 m; the MRD-S has a nominal force capacity of 150 kN, and a stroke of ±0.1 m. The MRD-S was tested with two different magneto-rheological and one viscous fluid. Due to the presence of Eddy currents, both dampers show a time lag between current intensity and damper force as the magnetization on the damper changes in time. Experimental results from the MRD-L show a force drop-off behavior. A decrease in active-mode forces due to temperature increase is also analyzed for the MRD-S and the different fluids. Moreover, the observed increase in internal damper pressure due to energy dissipation is evaluated for the different fluids in both dampers. An analytical model to predict internal pressure increase in the damper is proposed that includes as a parameter the concentration of magnetic particles inside the fluid. Analytical dynamic pressure results are validated using the experimental tests. Finally, an extended Bingham fluid model, which considers compressibility of the fluid, is also proposed and validated using damper tests.
    Smart Materials and Structures 11/2014; 23(12):125028. DOI:10.1088/0964-1726/23/12/125028 · 2.45 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Viscous fluid dampers have been used in many building and bridge construction projects for earthquake damage mitigation. Previous study has shown that silicone oil properties, such as the fluid shear-thinning and relaxation effects, play important roles for the annular-orificed fluid damper behavior, and the Navier-Stokes equations based on these mechanisms were developed. In the current study, attempts are made to explain the effects of frequency, damper dimensions, and viscosity of silicone oil on the damper stiffness behavior using the developed equations. It is found that the developed equations successfully explain the observed phenomena. To avoid the complicated fluid dynamics analyses for damper parameters, such as the damping factor and the velocity power exponent, a new four-parameter equation considering both the fluid shear-thinning and stiffness effects, with a form similar to the widely used two- or three-parameter equation is proposed. The results of the new model successfully capture the damper behavior both at low and high frequencies and show an advantage that better consistent results can be obtained in the velocity range for the building and bridge applications.
    Archive of Applied Mechanics 01/2012; 82(1). DOI:10.1007/s00419-011-0534-z · 1.44 Impact Factor

Preview

Download
10 Downloads
Available from