Investigation of the ability of low-frequency acoustic energy for polishing of the CK60 steel using a hybrid FE/BE/DEM approach

摘要

The polishing process based on abrasive ceramic particles is one of the non-conventional techniques that is hired extensively by manufacturers. There are different methods to generate kinematic energy for abrasive powders in order to impact the workpiece. In this study, low-frequency acoustic energy was utilized directly to provide motion in abrasive grits for the polishing of the CK60 (high carbon steel) workpiece. Wave shape and frequency of excitations were chosen as the two most important of the process parameters that were dependent on the acoustic source. The effects of these parameters on the kinematics of the particles and contact forces were investigated using the discrete element method (DEM). To this end, three main different types of parameters should be defined for modeling the polishing process: size and distribution of particles, particle-particle and particle-workpiece contact parameters, and boundary conditions of the process for different excitations. The shape, size, and distribution of particles were determined using experimental measurements and verified by simulations. Contact parameters between particles and workpiece were derived by experimental techniques. To define the boundary condition of the process, hybrid finite element/boundary element methods were employed to derive the response of the container due to different acoustic excitations and use it as an input for further DEM simulations. Kinematics of particles were computed at different conditions and compared with the experimental particle image velocimetry tests. The numerical results for the particle's velocity were in good agreement with the experiments. In the next phase, the most efficient condition for polishing process was computed using DEM. Roughness and microscopic studies of the process approved that employing a square wave shape at 70 Hz for acoustic excitation, which was predicted by numerical simulations, enhances the surface quality of the workpiece significantly.