Magneto-rheological fluid behavior in squeeze mode

Little published data exists on the behavior of MR fluids in squeeze mode. Many of the basic properties of MR fluids in squeeze mode are still unknown. In squeeze mode, MR fluids can generate a large range of force associated with a small displacement. As a result, squeeze mode has recently received more attention. This research focuses on modeling and testing MR fluids in squeeze mode. A novel squeeze mode rheometer is designed and built. MR fluid is tested in squeeze mode to evaluate its performance and behavior. The rheometer can test MR fluid under different conditions (gap size, magnetic field density, speed, etc). It utilizes a Gauss meter for direct measurement of the magnetic field density. MR fluid squeeze test results show that MR fluid can deliver a large range of force that is comparable in magnitude to the force in shear mode. The tests also indicate a clumping effect of the fluid when tested in repeated cycles that does not appear to have been documented previously. This paper describes, in detail, the clumping effect and provides possible reasons for this phenomenon. A non-dimensional mathematical model is developed and validated experimentally. The non-dimensional model directly compares the squeeze mode force to the shear mode force. The results indicate that MR fluid in squeeze mode can be used in many applications requiring a large range of controllable force in envelopes that can only accommodate small strokes.