Magnetorheological (MR) fluids are the fluids that respond to an applied magnetic field with a vivid change in rheological behavior. An MR fluid is a free-flowing liquid in the absence of magnetic field, but under a strong magnetic field its viscosity can be increased by more than two orders of magnitude in a very short time (milliseconds) and it exhibits solid-like characteristics. The strength of an MR fluid can be described by shear yield stress. Moreover, the change in viscosity is continuous and reversible, i.e. after removing the magnetic field the MR fluid can revert to a free flowing liquid. This paper describe two quasi-static models, a parallel-plate model and an axisymmetric model, based on the Navier-Stokes equation are developed for MR damper behavior. The Herschel-Bulkley viscoplasticity model is employed to describe the MR fluid field dependent characteristics and shear thinning/thickening effects. Simple equations based on these damper models are given which can be used in the initial design phase. Effects of geometry on MR damper performance, controllable force and dynamic range, are also discussed. Also, describe the complete design and some practical design considerations for developing and testing small capacity prototype MR fluid linear vibration damper. In design process we come across geometry design to choose an appropriate gap size`g’ and active pole length`L’ such that the design requirements of dynamic range and controllable force are achieved. Tasks in the design of a magnetic circuit are to determine necessary amp-turns (NI) for the magnetic circuit.
