Novel Bidirectional Volume Alternating Cavitation Technique for the Inner Surface Finishing of Small Holes

With the development of miniaturization and precision of cutting-edge equipment, functional parts with small holes have an increasing number of stringent requirements on their inner surface quality. The present work proposes a bidirectional volume alternating cavitation finishing (BVACF) method to refine the inner surface of small holes with a large aspect ratio (L/D ≥ 10). Using the self-design bidirectional volume alternating cavitation experimental apparatus, the finishing experiments on the inner surface of small holes were performed for Al 1060, T2Cu parts by drilling, as well as AlSi10Mg parts by additively manufactured method, to verify the availability of the BVACF method. Selecting Al 1060 small holes as the experimental sample and taking the profile surface roughness Ra and material removal rate (MRR) as the evaluation indexes, the influence of process parameters such as processing time, frequency, and volume change on the finishing quality is investigated. Furthermore, a physical model of the non-synchronous collapse of group cavitation bubbles is established to reveal the material removal mechanism of the BVACF method. The repeated impact of microjets and shock waves generated by cavitation bubble collapse causes the fatigue fracture of the surface material of small holes, which is the dominant mechanism to remove material in the BVACF process.