Clutch and Brake Related Testing of Magnetorheological Fluids Using the Basf Twin Gap Magnetocell

Abstract

A new magnetocell, based on a plate-plate twin gap with housing and integrated online flux density measurement, allows for a reliable rheological characterization of magneto¬rheological fluids (MRF). Various modifications introduced into the commercial magnetocell version MRD180/1T (Physica/Anton Paar), distinctly improve the homogeneity of the magnetic flux density distribution and broaden the range of accessible shear rates in a MCR501 rheometer up to more than 3000 s-1. The new design has been licensed to the manufacturer, to provide a commercial twin gap magnetocell. Fixed volume dosing of MRF yields an improved reproducibility of flow curve measurements, as required for the design of technical devices like MR clutches and MR brakes. The twin gap magnetocell enables the mimicking of MRF response relevant for clutch and brake applications, like shear rate or shear stress step or ramp testing, and drive cycle testing. The dynamic shear stress response to changes of flux density and/or shear rate may be characterized. Testing of MRF is possible for brake applications under constant holding torque conditions in the pre-yield regime. MRF creep and recovery for various imposed shear stresses may be monitored as a function of time. Comparison with a concentric cylinder pilot clutch underlines the validity of the shear stress versus flux density characteristic as determined with the twin-gap magnetocell.

Keywords

• magnetorheological fluid (mrf)
• twin gap magnetorheometer
• high shear rates
• clutch and brake application
• creep compliance
• ramp test
• drive cycle test
• durability test