Characteristic analysis and squeezing force mathematical model for magnetorheological fluid in squeeze mode

Magnetorheological fluid is a kind of intelligent material with a controllable state. It has three working modes: valve mode, shear, and squeeze. The squeeze mode can produce greater response under the external excitation conditions, with significant application potential and advantages. In this paper, a magnetorheological fluid squeeze performance test device was designed, and the squeeze experiments under different magnetic field strengths and loading speed conditions were implemented, and then the MRF squeeze flow theory model was established, which is the key factor affecting the squeeze force are revealed. The experimental results show that the squeeze force change trend presents three stages, of which the first stage represents the state before yielding; the loading speed has a significant effect on the change of the squeeze force curves, especially around 1 mm/s, the squeeze force curves show different development trends. Through theoretical analysis, it is concluded that loading speed, magnetic field change gradient, and magnetorheological fluid dynamic yield strength are the key factors affecting the squeeze force, which provide basic theoretical support for the evaluation and research application of the extrusion performance of magnetic material.