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<p>Magnetorheological (MR) fluids exhibit field-dependent yield stress and viscosity, enabling their use in adaptive damping, braking, and clutch systems. However, precise rheological characterisation remains difficult due to issues such as fluid loss from centrifugal forces, non-uniform magnetic fields, and deformation of measurement gaps under magnetic loading. This work introduces the design, magnetic optimisation, and experimental validation of a new concentric cylindrical magnetorheometer that overcomes these challenges. The proposed device features an enclosed geometry to prevent fluid loss, a fixed-radius shear design to maintain consistent shear rates, and an optimised magnetic circuit to provide uniform flux distribution without creating normal magnetic forces. Magnetic circuit modelling, supported by finite element simulations, confirms enhanced field uniformity and efficiency. Rheological testing with custom-prepared MR fluids demonstrates the instrument’s capability to measure dynamic yield stress under varying magnetic field strengths, rotor–stator material combinations, particle concentrations, and gap sizes. Results show a strong link between magnetic material configuration and yield stress, significant increases in yield stress with higher carbonyl iron particle content, and performance reductions at larger gap sizes. The device’s accuracy and repeatability make it a reliable platform for advanced MR fluid research and application development at high shear rates.</p>

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Design, development, and performance assessment of a modified concentric cylindrical magnetorheometer for precise rheological characterisation of MR fluids

  • 期刊论文

  • 发表日期：

    2026年6月17日

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  • Bittu Kumar Singh,
  • Chiranjit Sarkar

摘要

Magnetorheological (MR) fluids exhibit field-dependent yield stress and viscosity, enabling their use in adaptive damping, braking, and clutch systems. However, precise rheological characterisation remains difficult due to issues such as fluid loss from centrifugal forces, non-uniform magnetic fields, and deformation of measurement gaps under magnetic loading. This work introduces the design, magnetic optimisation, and experimental validation of a new concentric cylindrical magnetorheometer that overcomes these challenges. The proposed device features an enclosed geometry to prevent fluid loss, a fixed-radius shear design to maintain consistent shear rates, and an optimised magnetic circuit to provide uniform flux distribution without creating normal magnetic forces. Magnetic circuit modelling, supported by finite element simulations, confirms enhanced field uniformity and efficiency. Rheological testing with custom-prepared MR fluids demonstrates the instrument’s capability to measure dynamic yield stress under varying magnetic field strengths, rotor–stator material combinations, particle concentrations, and gap sizes. Results show a strong link between magnetic material configuration and yield stress, significant increases in yield stress with higher carbonyl iron particle content, and performance reductions at larger gap sizes. The device’s accuracy and repeatability make it a reliable platform for advanced MR fluid research and application development at high shear rates.