Modeling and experiment on elastic material removal in nanoparticle jet polishing

Nanoparticle jet polishing (NJP) is based on the principle of comprehensive physical and chemical effects, and has broad application prospects in the field of ultra-smooth surface polishing. It is necessary to further analyze the factors influencing non-destructive material removal and polishing ability. In this study, the movement of fluid and particles is analyzed using computational fluid dynamics to reveal the influence of the injection angle on the material removal distribution in a three-dimensional space. To analyze the elastic material removal process in the NJP, the elastic-plastic transition criterion and contact area model were established when the particles come in contact with the workpiece, and the critical vertical velocity of the particles is defined. The contact force between the particles and the workpiece at different injection angles is calculated. It is confirmed that the workpiece deformation was always within the elastic range. Based on the proposed model, the tool influence functions (TIFs) at different injection angles are predicted, which are consistent with the experimental results. To improve polishing accuracy, a method for solving the optimal fitting Gaussian function of TIF was presented, and its Gaussian characteristics were analyzed. The TIF obtained by oblique injection and a smaller-diameter nozzle has a concentrated material removal distribution and the preferred Gaussian characteristics, which can realize accurate material removal at the target position. The polished surface of the monocrystalline silicon is evaluated using various characterization methods. The established elastic-plastic transition criterion is helpful for NJP in selecting appropriate parameters to obtain an ultra-smooth surface without defects. This study lays a theoretical foundation and provides technical support for the process optimization of NJP.