Squeeze-strengthening of magnetorheological fluids (part 1): Effect of geometry and fluid composition

Recent research has shown that magnetorheological fluid can undergo squeeze-strengthening when flow conditions promote filtration. While a Péclet number has been used to predict filtration in non-magnetic two-phase fluids submitted to slow compression, the approach has yet to be adapted to magnetorheological fluid behavior in order to predict the conditions leading to squeeze-strengthening behavior of magnetorheological fluid. In this article, a Péclet number is derived and adapted to the Bingham rheological model. This Péclet number is then compared to the experimental occurrence of squeeze-strengthening behavior obtained from several squeeze geometries and magnetorheological fluid compositions submitted to pure-squeeze conditions. Results show that the Péclet number well predicts the occurrence of squeeze-strengthening behavior in high-concentration magnetorheological fluid made from various particle sizes and using various squeeze geometries. Moreover, it is shown that squeeze-strengthening occurrence is increased when using annulus geometries or by increasing average particle radius. While lowering concentration increases filtration, tested conditions only led to squeeze-strengthening behavior after concentration had increased close to packing limit. Altogether, results suggest that the Péclet number derived in this study can be used to predict the occurrence of squeeze-strengthening for various magnetorheological fluids and squeeze geometries using the well-known rheological properties of magnetorheological fluids.