Steady Shear Rheology and Magnetic Properties of Flake-Shaped Iron Particle-Based MR Fluid: Before and After Tribology Study

摘要

In this work, rheological properties and magnetic properties of flake-shaped iron particle-based magnetorheological (MR) fluid after tribology study were investigated and compared with that of before tribology study. With this aim, the flow properties of the MR suspensions in a steady shear regime were investigated, using a rotational rheometer with a parallel-plate measuring cell. The magnetic properties were studied using vibrational magnetometer. The rheological study was carried out for a broad range of magnetic fields. The results show that MR effect decreases for the fluid which is exposed to tribology study. The off-state viscosity and magnetization of the system increases. The surface morphology investigated using scanning electron microscopy shows that ball surface was ware and flake-shape particle morphology remains unaltered. The increase in off-state viscosity is attributed to the wear particles from the ball surface, which are of typically submicron sized as well as some particles from flake-shaped iron surface. These particles behave as a lubricant between the flake-shaped particles and reduce the particle-particle friction. As a result, the orientation ordering increases when the field is higher than frictional force. This results in increase in magnetization at higher fields. The oxidation stability of the iron particle is also confirmed form thermo gravimetric analysis of the particle. The present investigation suggests the use of flake-shape particle can avoid in-use thickening of MR fluid.