Fluid magnetic abrasives and its applications in the precision finishing process

Abstract

The fluid magnetic abrasives (FMA) are a new kind of precision finishing abrasives. In the absence of an applied magnetic field, FMA exhibit Newtonian-like behaviour. When exposed to a magnetic field, the viscosity and yield shearing stress of FMA increase several orders of magnitude rapidly, a reversible fluid-to-solid phase transition occurs, and a "soft abrasive layer" in conformity to the profile of work surface is created. Based on these distinctive features of FMA, a new type of precision finishing technology for complex geometrical shapes of engineering components has been developed. In this paper, the finishing mechanism, finishing process and applications of FMA are presented. Based on the yield shearing stress model of the FMA and the theory of fluid dynamics, The mathematic model of cutting force acted on the surface and the equation of material removal rate have been derived. The influence of some key parameters such as magnetic strength and direction, size of abrasives, volume concentrations of nonmagnetic abrasive and ferromagnetic particles, saturate magnetization, time of process and relative motion speed in respect to work pieces in finishing process on the finishing efficiency and the final surface roughness are discussed as well.