Study on rheological behaviors of media and material removal mechanism for abrasive flow machining (AFM) micro structures and corresponding simulations

Abstract

The abrasive flow machining (AFM) technique has great potentials for machining micro and complicated structures, when the specific media with both favorable fluidity and machinability are essential. In the present study, components, structures and rheological behaviors of a typical type of media were analyzed, based on with the material removal mechanism was firstly discussed. The Carreau-Yasuda model was applied for simulating the AFM process, in which the shear viscosity and relative parameters were precisely determined by analyzing the rheological behaviors of the media. The wall slipping behavior was analyzed and defined by the Generalized Navier slipping model. It was showed that the polymer melt and plasticizer oil presented similar compositions and structures, containing linear chains with few side groups, contributing to the fluidity of the media. The intense peak value in the creep curve (3.55 Pa−1) demonstrated a higher value of the viscous component than that of the elastic component, while the occurrence of saltatory regression further verified the linear structure of polymer chains. Owing to the retraction of streamlines from larger chambers into micro structures, and the combined effects of the shear stress and first normal stress difference, the polymer chains remained in stretched states, leading to uniform indentation depths and machining effects all over the machined surfaces. The flow velocity in the micro holes, which was obtained by the new simulation method, was roughly 1.5 m/s, proving that the retention time (2 × 10−3 s) was much shorter than the relaxation time of the media (230 s), indicating long-standing stretched states. The homogenous and a certain degree of shear stress, storage and loss moduli close to the inner hole surface further verified the favorable and uniform machining effects. This research is valuable for guiding the design of the media and abrasive flow machining procedures for micro structures, from aspects of either experiments or simulations.