弹性基体软固结磨料磨具的材料去除机理

Material Removal Mechanism of the Elastic Soft-bonded Abrasive Tool

基于弹性磨具的磨抛工艺为硬脆材料超精密加工效率与加工质量的兼顾平衡提供了新的解决思路,但其磨抛过程的材料去除机理尚未明确。为研究弹性磨抛过程中的材料去除行为,以硅橡胶作为磨具基体材料,混合微米级金刚石磨料制备弹性基体软固结磨料磨具,利用有限元仿真分析方法研究弹性基体软固结磨粒的受力状态,结合接触力学与运动学分析建立考虑单颗磨粒磨损行为与有效磨粒数量的材料去除模型,通过石英玻璃试件的弹性磨抛加工试验验证预测模型的准确性。结果表明:石英玻璃试件的材料去除率随着磨抛压力、主轴转速、磨具偏角的增大而显著增加,而磨料粒径对其影响程度较小;当工艺参数组合为磨料粒径100μm、磨抛压力7 N、主轴转速1500 r/min、磨具偏角20°时,经60 min磨抛后,工件已加工表面粗糙度由1.069μm降至0.089μm,材料去除率为8.893×10^(8)μm^(3)/min;该试验条件下,建立的材料去除模型预测准确度相比Preston经典模型提高36.7%。研究成果可为实现硬脆材料的确定性材料去除提供技术支持和理论依据。

Hard and brittle materials such as sapphire(α-Al_(2)O_(3)),silicon carbide(SiC),and optical glass are widely used in aerospace,biomedicine,optoelectronic information,and other advanced fields.The compound demand for efficiency and quality has been a long-standing problem in the development of ultraprecision machining technology for hard and brittle materials.Abrasive tools based on rubber or other matrix materials can achieve nanometer-scale surface roughness while maintaining a high material removal efficiency and avoiding surface scratches and damage through elastic contact adaptive grinding and polishing.However,the grinding and polishing processes based on elastic abrasive tools are complex,and the material removal mechanism is unclear.An elastic soft-bonded abrasive tool is proposed to evaluate the mechanism of flexible-contact ultraprecision grinding and polishing.Silicon rubber is selected as the matrix material,and an elastic soft-bonded abrasive tool is prepared by mixing micrometer-sized diamond abrasives.A contact model between the elastic matrix and the processing object is established based on the Hertz contact theory.The stress distribution in the contact area is then visualized and analyzed.The stress state of the soft-bonded abrasive grains in the matrix during the grinding and polishing processes is analyzed using theoretical derivation and finite element simulation.Based on the Preston equation,contact stress distribution,and kinematic analysis,an optimal material removal model for compliant grinding and polishing is proposed,which considers the wear mechanism of a single abrasive grain and the number of effective abrasive grains.The material removal rate and material removal profile in the machining area of the single-point dwell grinding and polishing are predicted.The accuracy of the predictive model is verified by conducting compliant grinding and polishing experiments on quartz glass specimens.The results showed that the material removal profiles measured by the theoretical simulation and experiment did not exactly match;however,they had a high similarity,and the maximum deviation in the material removal depth was 13.1%.In the y-z profile,the cross-sectional curve of the material-removal profile was distributed axially symmetrically.In the x-z profile,the position of the maximum material removal shifted slightly along the x-axis direction.This is because the relative velocities in the contact area are not symmetrically distributed when the elastic abrasive tool is at a certain inclination angle.The material removal rate of the quartz glass specimen significantly increased with an increase in the grinding and polishing pressure,spindle speed,and tool inclination angle,whereas the effect of the abrasive grain size was relatively small.When the process parameters were set to the abrasive grain size of 100μm,grinding and polishing pressure of 7 N,spindle speed of 1500 r/min,and tool inclination angle of 20°,after 60 min of grinding and polishing,the surface of the workpiece changed from having obvious grooves to having good uniformity and the surface roughness of the machined workpiece was reduced from 1.069μm to 0.089μm;the material removal rate was 8.893×10^(8)μm^(3)/min,obtaining excellent surface quality while maintaining a high material removal rate.Under the aforementioned experimental conditions,the accuracy of the material removal model proposed in this study was 36.7%higher than that of the classic Preston model.The elastic abrasive tool has good technical feasibility in ultra-precision grinding and polishing for hard and brittle materials The optimized material removal model can effectively describe the compliant grinding and polishing process of the elastic abrasive tool,and provides technical and theoretical bases for deterministic material removal of hard and brittle materials.