Detection of Pressure or Flow Rate Variations in MR Valves through Magnetic Flux Analysis

Magneto-Rheological (MR) fluids consist in a suspension of ferromagnetic particles dispersed in a fluid carrier. If excited by a magnetic source, the nearby magnetic field induces the particles magnetization with the formation of chainlike structures aligned parallel to the field direction. This phenomenon is responsible of the rise of a magnetic field dependent yield stress required to counteract the interactions between adjacent particles and break the ferromagnetic clusters. Thus, in the case of an external effort applied to the fluid, chain-like structures are stretched and the increased distance among adjacent particles results in an augmentation in the reluctance of the gap in which the MR fluid flows. The consequent variation in the magnetic flux produced by an exciting magnetic source can be detected as an induced voltage appearing in the system. The presented work proposes and discusses experimental sessions intended to underline the possibility to employ the aforementioned phenomenon in order to detect pressure or flow variation in MR valves.