Machining uniformity and property change of abrasive media for micro-porous structures

Abstract

To accurately analyze the flow behavior of abrasive media in microporous structures, CFD simulation coupled with the Brid-Carreau model, Mixture model, and Discrete Phase model were adopted. By comparing the simulated and measured volumetric rates, the results validity was verified. The similar distribution of flow parameters, e.g., pressure, velocity, wall shear stress and shear rate, along with the roughly uniform distribution of grooves in all micro-holes demonstrated the machinability and uniformity of abrasive flow machining (AFM) microporous structures. Despite the vast shear rate caused by sharp shrink of flow diameters, the composition and rheology of the media after machining 0.1 mm holes would not be damaged. Moreover, due to the high temperature sensitiveness of polymer components, thermogravimetric analysis (TGA) was conducted. The 80.85 loss ratio of plasticizer oil to polymer matrix further indicated the major factor of plasticizer oil in total weight loss of media. With regard to the rheology under a series of temperatures (25 ℃, 50 ℃, 75 ℃, and 100 ℃), the values of rheological behaviors differed from each other, mainly resulted from the dynamic variation between the strengthening effect and the weakening effect caused by loss of plasticizer oil and the rise of temperature respectively. While the similar variation tendency of all rheological behaviors indicated that the rheology of the media would not be harmed when the temperature was below 100 ℃. All results demonstrated excellent uniformity and stability of abrasive media when machining microporous structures and provided a certain guide on AFM procedures. • Brid-Carreau model coupled with mixture and discrete phase models were employed and further verified by measured results. • Simulation results and surface morphology demonstrate the machining uniformity on micro-porous structures. • The huge external shear effect could not damage the composition and rheology of media. • The weight loss of plasticizer oil was the major factor affecting total weight loss of media. • Rheology of the media will not be disturbed when the temperature is below 100 ℃.