Prediction analysis of subsurface damage of work-part ZnS in fixed abrasive lapping

The subsurface damage of workpiece formed in lapping and polishing process is the main reference to evaluate the quality of processing technology and decide the machining allowance. Therefore, the accurate prediction of subsurface damage is helpful to improve the machining efficiency. Discrete element method (DEM) was used to simulate the subsurface damage of the fixed abrasive lapping process of typical soft and brittle material ZnS, and the depth of subsurface microcrack layer after diamond machining with different particle sizes was predicted. The angle polishing method was used to polish the workpiece to an inclined plane as the sub surface damage observation plane. The corrosion of hydrochloric acid makes the subsurface microcracks appear. Under the metallographic microscope, the end point of microcracks disappearance was found and converted into the depth of subsurface microcrack layer, and the simulation results were verified by experiments. The results show that the predicted values of the depth of subsurface microcrack layer caused by grain size of 5 μm, 15 μm, 25 μm and 30 μm are 2.28 μm, 3.62 μm, 5.93 μm and 7.82 μm respectively, and the measured values of angle polishing method are 2.02 μm, 3.98 μm, 6.27 μm and 8.27 μm respectively. The results show that the wear particle size has a great influence on the subsurface damage of ZnS. With the increase of wear particle size, the depth and number of micro cracks increase. The deviation between predicted value of discrete element method and measured value is 5% - 15%. The subsurface damage of soft and brittle material ZnS after processing can be accurately predicted by using the discrete element method, which provides a reference for the formulation of polishing process.