Author(s): Wojciech Grzeskowiak, Urszula Hajduk and Witold Iwanicki

Abstract: Magneto-Rheological (MR) dampers promise tunable ride comfort, yet their long-term performance depends on whether the MR fluid retains its rheological properties after hundreds of thousands of shear cycles. This research subjected a commercial MR fluid (LORD MRF-140CG) to 600,000 sinusoidal shear cycles (±25 mm amplitude, 2 Hz, 25 °C) in a purpose-built cyclic-loading rig and measured apparent viscosity at three magnetic field strengths (0, 0.3, and 0.6 T) at six sampling intervals. Fluid samples were also tested in a production MR damper on a servo-hydraulic test machine to quantify the resulting change in damping force. After 600,000 cycles the off-state viscosity fell by 8.3% (from 48.2 to 44.2 mPa·s), the 0.3 T viscosity by 18.5% (312.4 to 254.6 mPa·s), and the 0.6 T viscosity by 17.7% (847.3 to 697.4 mPa·s). The damping-force retention at 0.6 T and 0.40 m/s piston velocity dropped to 79.1% of the fresh value a loss that would be perceptible to the vehicle occupant as a softer ride on rough roads. Particle-size analysis by laser diffraction showed that the mean iron-particle diameter decreased from 7.1 µm (fresh) to 5.8 µm (600 k cycles) owing to mechanical attrition, while sedimentation height increased from 2.4 mm to 6.1 mm over a 72-hour settling test, indicating weakened suspension stability. These data provide damper-system engineers with degradation curves that can be embedded in durability-calibration models to schedule fluid replacement or controller-gain compensation over the vehicle's service life.

DOI: https://www.doi.org/10.22271/27078205.2026.v7.i2a.87

Pages: 47-50 | Views: 139 | Downloads: 54

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