ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Rheological characterization and sedimentation stability of ferrofluid-modified magnetorheological fluids optimized via a novel hybrid algorithm

S. S. Stalin, P. Balamurugan, M. Uthayakumar, and M. Pethuraj

Department of Mechanical Engineering, Kalasalingam Academy of Research and Education, Krishnankoil, India

E-mail: pbala.klumech@gmail.com

Received: 24 June 2025  Accepted: 16 October 2025

Abstract:

Magnetorheological (MR) fluids which are characterized by their field-responsive rheological characteristics are very common in most engineering applications. In this study, a carrier fluid was silicone oil, carbonyl iron powder (1 µm and 5 µm) as the additives, and the final concentration of ferrofluid additives (1% and 2% denoted as MR-1 and MR-2) were optimized to form an MR fluid. A new Hybrid Ant Colony and African Buffalo Optimization (HACABO) algorithm was used to increase the total performance by reducing the sedimentation. Experiments showed that the fluid that has been optimized could attain a yield stress of 9000 Pa with a magnetic field strength of 400 kA/m. The braking torque rose by 22.04 percent, that is, 63.38 Nm to 85.32 Nm. The stabilities of the sedimentation were also greatly enhanced and the MR-1 formulated had sedimentation ratios of 95% (analytical) and 89% (experimental), as opposed to 90% with pure carbonyl iron and 81% with coated particles. The fluid was also optimized and showed better performance in terms of viscosity at various shear rates. More so, as the magnetic field strength was increased, the storage and loss moduli increased which means that the viscoelastic behavior was improved. The HACABO-MR fluid formulation has a high potential of high-efficiency damping, including rotary braking systems.

Keywords: Magnetorheological fluids; Ferrofluid additives; Rheological characterization; Sedimentation stability; Braking torque optimization; Metaheuristic algorithms

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-025-04460-3

Chemical Papers 80 (2) 1409–1421 (2026)