固结磨料研磨硫化锌的亚表面损伤预测分析

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

研磨抛光后产生的工件亚表面损伤是评价工艺优劣及确定加工余量的主要参考,因此对亚表面损伤准确的预测有助于提高加工效率。采用离散元法对典型的软脆材料硫化锌固结磨料研磨过程中产生的亚表面损伤进行模拟,预测不同粒径金刚石加工工件后的亚表面微裂纹层深度。利用角度抛光法将工件抛光出一个斜面,作为亚表面损伤观测平面,通过盐酸的腐蚀使亚表面微裂纹显现,在金相显微镜下寻找微裂纹消失的终点位置并转换成亚表面微裂纹层深度,对仿真结果进行实验验证。结果表明:粒径为5、15、25、30μm的磨粒造成的亚表面微裂纹层深度预测值分别为2.28、3.62、5.93、7.82μm,角度抛光法实测值分别为2.02、3.98、6.27、8.27μm。以上结果表明磨粒粒径对硫化锌亚表面损伤情况有很大的影响,随着磨粒粒径的增大,亚表面微裂纹深度增加,微裂纹数量增多。离散元法预测值与实测值偏差范围处在5%~15%之间,利用离散元法能有较为准确的预测软脆材料硫化锌加工后的亚表面损伤情况,为其研抛工艺的制定提供参考。

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 5μm,15μm,25μm and 30μm are 2.28μm,3.62μm,5.93μm and 7.82μm respectively,and the measured values of angle polishing method are 2.02μm,3.98μm,6.27μm and 8.27μm 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.