Experimental analysis of large capacity MR dampers with short- and long-stroke

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.

Transient multi-physics analysis of a magnetorheological shock absorber with the inverse Jiles–Atherton hysteresis model

“…The induced electromotive force (EMF) generates eddy currents in the piston and external casing of the MR absorber. An eddy current creates a magnetic field that opposes the target magnetic field and thus the net magnetic flux is reduced, which is identif ied as the principal cause of the slower force increase or decrease than that of the input current as the MR damper switches between its passive and active modes [16]. To better understand the influence of the eddy current on the resultant magnetic flux density, a finite element simulation concerning variable magnetic fields was performed based on the COMSOL Multi-physics software.…”

“…shown in figure 3. One possibility to reduce the eddy current by simple geometric modification has been deemed ineffective [16]. However, regardless of eddy current, overshooting current intensity steps may be an option to achieve the desired net magnetic flux density in the fluid region.…”

“…At the moment the factors that affect the delay phenomenon of current and force can be concluded as: fluid compressibility, ferromagnetic material hysteresis and eddy current. It is noted that the influence of fluid compressibility on the delay phenomenon can be ignored under high velocity [16].…”

Design and analysis of an innovative combined magneto-rheological damper-mount

“…Hence, this mount was also a high-loaded mount, and its central plate could self-adjusted its damping gap following the magnitude of excitations. The adjustment of [8]. In this study, a long stroke damper and a short stroke damper were used to investigate characteristics.…”

“…From the above analysis, the valve of MR damper includes two groups such as bypass [1] and piston-type [2,3,4,8,5,10]. …”