熔石英磨削的残余应力层深度预测研究

Prediction of Residual Stress Layer Depth in Grinding Fused Quartz

目的磨削后工件表面残余应力处于裂纹层下方其位置隐蔽、不易检测,使用过程中受到应力作用易扩展成裂纹,影响后续工艺参数设计和工件使用寿命。因此,研究磨削后表面残余应力层深度有助于确定后续工艺加工余量,提高工件使用性能。方法本文采用离散元法建立单颗磨粒磨削熔石英的离散元模型,研究磨粒粒径对工件亚表面损伤深度的影响。采用角度抛光法和差动腐蚀法测量熔石英亚表面裂纹层和损伤层深度,计算残余应力层深度并验证模型。结果当磨粒粒径分别为7、14、28、40μm时,仿真得到的裂纹层深度分别为2.53、3.02、4.07、7.39μm,残余应力层深度分别为0.75、1.00、1.34、2.33μm;实验测得的裂纹层深度分别为2.51、3.14、4.65、8.16μm,残余应力层深度分别为0.86、0.93、1.31、1.87μm。由此可见,随着磨粒粒径的增大,工件表面的脆性去除愈加明显,表面质量变差,亚表面裂纹层深度和残余应力层深度增大。仿真预测裂纹层深度与实验值偏差小于15%,残余应力层深度偏差小于25%,残余应力层深度约为裂纹层深度的1/4~1/3,随磨粒粒径增大,比例逐渐减小。结论离散元仿真可有效预测熔石英磨削后的残余应力层深度,为其磨削工艺的制定提供参考。

Fused quartz has excellent physical and chemical properties,and is widely used in manufacture of optical components and other industries and many fields of modern science and technology.However,fused quartz glass is a high hard and brittle material.Cracks,residual stress and other damage are likely to occur during processing.The surface residual stress layer of the workpiece after grinding is under the crack layer,its position is hidden and difficult to observe.During the use of the workpiece,it is easy to expand into cracks under the action of external load,which affects the design of subsequent process parameters and the service life of the workpiece.Therefore,researching on the depth of surface residual stress layer after grinding is helpful to determine the residual processing allowance and improve the working performance of the workpiece.In this paper,the discrete element model of single particle grinding fused quartz was established by the discrete element method.By changing the cutting depth corresponding to different particle sizes in the simulation process,the influence of diamond particle size on the subsurface damage depth of the workpiece was studied.In the experiment,the fused quartz workpiece was ground with resin-based corundum grinding wheel.The grinding process only changed the particle size of the grinding wheel,and the other process parameters were fixed.Angle polishing method and differential corrosion method were used to measure the depth of the subsurface crack layer and the damaged layer,and the depth of the residual stress layer was calculated and the discrete element simulation results were verified.The results showed that when the particle size was 7,14,28,40μm,the simulated crack layer depth was 2.53,3.02,4.07,7.39μm,and the residual stress layer depth was 0.75,1.00,1.34,2.33μm,respectively.The depth of crack layer was 2.51,3.14,4.65,8.16μm,and the depth of residual stress layer was 0.86,0.93,1.31,1.87μm.It could be seen that with the increase of particle size,the removal of brittleness on the workpiece surface became more obvious,the surface quality deteriorated,and the depth of subsurface crack layer and residual stress layer increased.The residual stress layer was distributed below the crack layer,and there would be stress concentration at the crack tip.When the particle size was large,the stress at the tip would also increase as the subsurface crack of the workpiece expanded to the inside of the material after grinding.The depth of the residual stress layer also increased.The deviation between the crack depth and the experimental value was less than 15%,and the residual stress depth was less than 25%.The depth of the residual stress layer was about 1/4~1/3 of the depth of the crack layer.The proportion decreased gradually with the increase of the particle size.Therefore,the depth of residual stress layer can be predicted by obtaining the crack layer depth.The discrete element method can be used to simulate the grinding process of a single abrasive particle,so as to obtain the crack layer depth,and then predict the residual stress layer depth after grinding of fused quartz.The reference is provided for the grinding process parameters.