Research on the underlying mechanism behind abrasive flow machining on micro-slit structures and simulation of viscoelastic media

In this study, the machining mechanism of abrasive flow machining (AFM) microstructures was analyzed in depth according to the transmission morphology and rheological behaviors of the abrasive media. The transmission morphology demonstrated the excellent combination of the polymer melt with abrasive grains at the interface, indicating that the polymer melt, combined with the uniform distribution of the polymer chains, could exert a harmonious axial force on the abrasive grains. Based on the rheological behavior analysis of the abrasive media, for example, the stress relaxation and moduli of storage and loss, a machining mechanism model was established incorporating the effect of microplastic deformation and continuous viscous flow, which was further verified by the grooves along the flow direction. In addition, the Phan-Thien-Tanner (PTT) model combined with a wall slipping model was employed to simulate the machining process for the first time here. The value of the simulated pressure (1.3 MPa) was similar to the measured pressure (1.45 MPa), as well as the simulated volumetric rate (0.011 4 mL/s) to the measured volumetric rate (0.067 mL/s), which further proved the validity of the simulation results. The flow duration (21 s) derived from a velocity of 1.2 mm/s further confirmed the residual stretched state of the polymer chains, which favored the elasticity of the abrasive media on the grains. Meanwhile, the roughly uniform distribution of the shear rate at the main machining region exhibited the advantages of evenly spread storage and loss moduli, contributing to the even extension of indentation caused by the grains on the target surface, which agreed with the mechanism model and machined surface morphology.