Study of failure symptoms of a single-tube MR damper using an FEA-CFD approach

Abstract

A new magnetorheological (MR) damper has been designed, manufactured, modelled and tested under cyclic loads. A faulty behaviour of the damper was accidentally detected during the experiments. It was deduced that the presence of air bubbles within the MR fluid is the main reason for that failure mode of the damper. The AMT-Smartec+ MR fluid used in the current study, a new MR fluid whose characteristics are not available in the literature, exhibits good magnetic properties. However, the fluid has a very high viscosity in the absence of magnetic field. It is assumed that this high viscosity enables the retention of air bubbles in the damper and causes the faulty behaviour. To prove this assumption, a coupled numerical approach has been developed. The approach incorporates a Finite Element Analysis (FEA) of the magnetic circuit and a Computational Fluid Dynamics (CFD) analysis of the fluid flow. A similar approach was presented in a previous publication in which an ideal behaviour of an MR damper (no effect of air bubbles) was investigated. The model has been modified in the current study to include the effect of air bubbles. The results were found to support the assumptions for the reasons of the failure symptoms of the current MR damper. The results are shown in a comparative way between the former and current studies to show the differences in flow parameters, namely: pressure, velocity and viscosity, in the faultless and faulty modes. The results indicate that the presence of air bubbles in MR dampers reduces the damper force considerably. Therefore, the effect of the high yield stress of MR fluids due to the magnetic field is reduced.

Study on operational temperature of magneto-rheological fluid and design dimensions of magneto-rheological damper for optimization

“…The curve gradually changes to an elliptical shape as the frequency and amplitude increase, as explained by coulomb damping [33]. The change in shape of the force-amplitude graphs is due to the air bubbles trapped in the fluid [40]. 12(a)-(c) shows us the input parameters' forces and results for all the input conditions following the same decreasing trend in damping for LV-1 and LV-2 with varying values in force magnitude.…”

Magnetorheological fluids: A concise review of composition, physicochemical properties, and models

“…Thus, the results obtained by (Panowicz and Janiszewski, 2016) indicate that MRF can be more modeled with the Robertson–Stiff model (so-called Vocadlo model) (Chen et al, 1999), which was proposed to describe the rheological behavior with nonlinear characteristics of the concrete solutions, gels, and polymers. The Robertson–Stiff model is described by the following equations being the combination of the Bingham plastic model (4), and the Ostwald de Waele equation (Elsaady et al, 2021)…”

Influence of temperature on magnetorheological fluid properties and damping performance

“…Along with accumulator and air bubble effect and inertial and frictional effects also has a minimal impact on force reduction. The characterisation of MR damper in this study is carried out in the absence of the accumulator which is creating average compression load of 36.9% more than the expansion stroke [55,56]. The air bubble effect also adds to the distortion in force displacement graphs at lower temperatures as the damper operating time increased the temperature of the fluid increases which reduces the viscosity of the fluid making the air escape from the MR fluid decreasing the distortion in force-displacement graph.…”