In abrasive flow machining (AFM), material is abraded by active abrasive particles powered by solid-liquid contact between them and the abrasive medium. This contact characteristic is a key and unfortunately it is investigated scarcely.In this work, a soft-contact model was firstly proposed. Soft-contact parameters including protrusion ratio and covering inclination angle were then defined to characterize soft-contact characteristics. Finally, the effect of medium pressure and particle diameter on soft-contact parameters was studied by full factorial design. Results showed that average scratch depth of single active abrasive particle increases with increasing particle diameter and medium pressure. In addition, active abrasive particles are actually deeply wrapped to a large proportion by abrasive medium, and the descriptive protrusion ratio decreases with increasing medium pressure and particle diameter. Moreover, medium pressure offers tangential and normal force for active abrasive particle through a covering inclination angle, and the angle increases with increasing medium pressure and particle diameter. It provides guidance for further improvement of prediction accuracy of material removal in AFM process.

Abrasive flow machining (AFM) is increasingly preferred to finish closed complicated flow channels machined by electrical discharge machining (EDM) owing to its high machining accessibility, surface integrity, and efficiency. The machining accuracy of closed complicated flow channels by AFM is dependent on the uniformity of material removal distribution (named as finishing nonuniformity here), but few studies on the finishing nonuniformity have been done so far. Firstly the finishing nonuniformity for EDM machined complicated flow channel by AFM was modeled and analyzed theoretically. Then three blisk with EDM surface roughness of Ra 1.5 μm, Ra 2.0 μm, and Ra 3.0 μm were finished by AFM to Ra 0.8 μm, and their finishing nonuniformity was compared. Finally, AFM flow simulation was carried out, and the simulation results were compared with that from the experiments. Theoretical results showed that finishing nonuniformity is resulted from the non-uniform flow field of the abrasive medium, and it increases with increasing EDM surface roughness and decreasing AFM surface roughness. This is verified by the AFM experiments and flow simulations. On this basis, the guideline for parameter optimization in the combined EDM + AFM process was discussed.

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