Magneto-rheological fluid behavior in squeeze mode

Abstract

Little published data exists on the behavior of MR fluids in squeeze mode. Many of thebasic properties of MR fluids in squeeze mode are still unknown. In squeeze mode, MRfluids can generate a large range of force associated with a small displacement.As a result, squeeze mode has recently received more attention. This researchfocuses on modeling and testing MR fluids in squeeze mode. A novel squeezemode rheometer is designed and built. MR fluid is tested in squeeze mode toevaluate its performance and behavior. The rheometer can test MR fluid underdifferent conditions (gap size, magnetic field density, speed, etc). It utilizes a Gaussmeter for direct measurement of the magnetic field density. MR fluid squeeze testresults show that MR fluid can deliver a large range of force that is comparable inmagnitude to the force in shear mode. The tests also indicate a clumping effectof the fluid when tested in repeated cycles that does not appear to have beendocumented previously. This paper describes, in detail, the clumping effect and providespossible reasons for this phenomenon. A non-dimensional mathematical model isdeveloped and validated experimentally. The non-dimensional model directlycompares the squeeze mode force to the shear mode force. The results indicate thatMR fluid in squeeze mode can be used in many applications requiring a largerange of controllable force in envelopes that can only accommodate small strokes.