Hydrodynamic response time of magnetorheological fluid in valve mode: model and experimental verification

Abstract

The transient behaviour of magnetorheological (MR) actuators affects their performance in progressive semiactive control suspension systems. The two sources of the time delay between the control signal and damping force are (a) dynamics of MR damper hardware and (b) the MR fluid dynamics. The significant part of the MR fluid response time is the so-called hydrodynamic response time which is connected with the transient flow. Due to the above, the main aim of this paper is to experimentally determine the hydrodynamic response time of MR fluid and present systematic means for characterizing it via computational fluid dynamics (CFD) or analytical tools. The unique measurement method using an in-house patented slit flow rheometer is presented. The essence of the method relies on determining the pressure drop variation with the time spent by the fluid in the MR gap. The experimental determined hydrodynamic response time of MR fluid ranges from 0.4 to 1 ms for a selected gap size and a range of magnetic field stimuli. The results show that the higher the magnetic field, the lower the hydrodynamic response time is. Both CFD and analytical models exhibit similar trends as the experimental data. Moreover, the impact of temperature and gap size was determined. Here, the higher the gap size and temperature of MR fluid, the longer the response time is.

Analysis and experimentation of variable gap magnetorheological transmission device driven by electromagnetic force

“…Magnetorheological fluid (MRF) is a type of intelligent material made from a mixture of soft magnetic particles with high permeability and low hysteresis, a non-conductive liquid with low viscosity and additives that prevent the soft magnetic particles from settling and oxidizing and corroding and cover their surface (Ashtiani et al, 2015; Daniel et al, 2018). Under the action of an applied magnetic field, soft magnetic particles form a chain of particles in the direction of the magnetic field within a very short period of time, allowing the magnetorheological fluid to transform from a liquid to a solid-like fluid in less than a millisecond (Horváth et al, 2022; Kubík et al, 2021; Laun and Gabriel, 2007), increasing the apparent viscosity by several orders of magnitude, and when the applied magnetic field is withdrawn, the magnetorheological fluid reverts to a liquid and the apparent viscosity decreases (Imaduddin et al, 2013; Olabi and Grunwald, 2007). The transformation of a magnetorheological fluid from a liquid to a solid-like fluid is known as the magnetorheological effect (de Vicente et al, 2011; Mazlan et al, 2007).…”

Magnetically induced stiffening for soft robotics

“…The microscopic iron particles align themselves along magnetic field lines, leading to the macroscopic stiffening effect in the bulk fluid. 70 The solidification of magnetorheological fluids occurs within a few milliseconds [71][72][73][74][75][76] when a magnetic field is applied, and this solidification increases with increasing magnetic field such that the stiffness of the material can be proportionally tuned. 31 This effect has historically been used in the production of active dampers [77][78][79][80] and when conforming around objects for gripping.…”

Structural Design and Controllability of Magnetorheological Grease Buffers under Impact Loading

“…When operating in harsh environments, large shock loads may be transmitted to the interior of the carrier, and the high-intensity loads may cause damage to the equivalent load [ 1 , 2 , 3 ]. Magnetorheological energy absorbers (MREAs) are widely used in carriers such as aircraft landing gear [ 4 , 5 , 6 ], helicopters [ 7 , 8 ], watercraft [ 9 ], and ground vehicles [ 10 ] that are subjected to linear reciprocating shock loads for long periods of time because of their outstanding advantages of continuously controllable rheological characteristics and fast response time of magnetic fields [ 11 ] and the magnetorheological fluid itself [ 12 ]. Since the impact conditions are often accompanied by high collision energy, the controllable damping force of magnetorheological buffers is highly demanded.…”