Magnetorheological fluid durability test—Iron analysis

Hua

Struct Control Health Monit

et al. 2018

In this paper, 30 magnetorheological (MR) dampers used for vibration control of stay cables after one decade of service were selected to study their long-term mechanical behavior. The damping capacity of the used MR dampers, including the damping force amplitude and the equivalent damping coefficient, was compared with those of new MR dampers. One used damper still with considerable damping capacity was utilized for the comparative study with a new MR damper under various input voltages, excitation frequencies, and excitation amplitudes. A modified phenomenological mechanical model for used MR dampers was developed based on the experimental observation. Moreover, some used dampers were cut in half, and the remaining volumes of the MR fluid were measured. The iron particles of the MR fluid in the used damper with the worst damping capacity were analyzed using a scanning electron microscopy (SEM). The results show that 24 dampers among the used dampers can still generate considerable damping force. However, the equivalent damping coefficient and the damping force amplitude of these 24 used MR dampers decreased by 32.4% and 29.8%, respectively, on the average. Furthermore, six dampers among the used dampers failed to provide enough damping.The proposed modified mechanical model is more accurate to reflect the mechanical behavior of used MR dampers. It was found that the performance degradation of the used dampers is related to the leakage of the MR fluid and the factor that the surface of MR iron particles became rough and uneven, as observed by the SEM. KEYWORDS damper durability, damping capacity, magnetorheological (MR) damper, magnetorheological (MR) fluid, modified mechanical model

Section: Discussion On Performance Degradation Of Used Mr Dampersmentioning

confidence: 99%

Mechanical behavior of magnetorheological dampers after long-term operation in a cable vibration control system

Hua

Struct Control Health Monit

et al. 2018

“…Other studies also reported similar IUT problems with most MR devices and systems after long-term operation applications [16,17,18]. Of interest is a study conducted on long-term operation of an MR fan clutch, which operated for 540 h to observe the change in MR fluid characteristics [13]. The study focused on analysis of the iron particles within the MR fluid.…”

Section: Introductionmentioning

confidence: 87%

“…So far, numerous application devices and systems, such as automotive damper, have been investigated, and some of the systems are used in the practical environment. Some of the specific applications include truck seat damper [11], a prosthetic knee joint [12], and fan clutches [13]. Although these devices or systems have shown great performances, some problems were not evident in the initial phase, and need to be addressed at a later time.…”

Section: Introductionmentioning

confidence: 99%

Material Characterization of a Magnetorheological Fluid Subjected to Long-Term Operation in Damper

et al. 2018

This paper investigates the field-dependent rheological properties of magnetorheological (MR) fluid used to fill in MR dampers after long-term cyclic operation. For testing purposes, a meandering MR valve was customized to create a double-ended MR damper in which MR fluid flowed inside the valve due to the magnetic flux density. The test was conducted for 170,000 cycles using a fatigue dynamic testing machine which has 20 mm of stroke length and 0.4 Hz of frequency. Firstly, the damping force was investigated as the number of operating cycles increased. Secondly, the change in viscosity of the MR fluid was identified as in-use thickening (IUT). Finally, the morphological observation of MR particles was undertaken before and after the long-term operation. From these tests, it was demonstrated that the damping force increased as the number of operating cycles increases, both when the damper is turn on (on-state) and off (off-state). It is also observed that the particle size and shape changed due to the long operation, showing irregular particles.

Proceedings of the 7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COM

“…This phenomenon causes an increase of the off-state viscosity and of the reacting force of the device. The coating of magnetic particles with a protective surface layer can be a solution to enhance the durability of MR fluids from this point of view [11,12]. c) Particle oxidation The MR fluid is characterized by a modification of its compositional properties, due to the absorption of carbon dioxide and the corresponding corrosion.…”

Section: Ageing Issues Of Mr Dampersmentioning

confidence: 99%

Short- Versus Long-Term Readiness and Dissipative Capability of MR Dampers for Structural Control

Spizzuoco¹

2019

The proposed work is based on an experimental activity aimed at comparing the long-term behavior of control devices based on the use of magneterheological (MR) fluids for seismic protection of framed structures. They have been tested three times in ten years: first in 2008, then in 2013 after five years of inactivity, and finally in 2017 after further four years of quiescence. The results of the three campaigns of passive and promptness experimental tests, in terms of force-displacement loops, electrical delay of the electromagnetic circuit, dissipated energy and maximum reacting force. The evolution of the response of such dampers due to inactivity over the time is assessed and discussed, aiming at recognize those phenomena are most probably responsible of a MR fluid deterioration (namely oxidation of iron particles, their sedimentation, fluid thickening, seal wearing), finally trying to give practical suggestions to the designers of smart control systems who should take this issues into account when dealing with the above kind of devices.