单颗金刚石磨粒切削氮化硅陶瓷仿真与试验研究

Simulation and Experiment Study for Silicon Nitride Cutting with Single Diamond Grain

为探索氮化硅陶瓷单颗磨粒切削加工的机理，进行单颗金刚石磨粒切削氮化硅陶瓷的仿真与试验。选用截角八面体模拟金刚石磨粒，基于Johnson—Holmquist ceramic硬脆材料本构模型，采用有限元网格法进行单颗磨粒直线切削仿真，分析工件材料的切屑去除、划痕形貌、应力动态变化与分布、切削力变化等现象，以及工艺参数对切削力的影响。制备单颗金刚石磨粒工具，在平面磨床上进行单颗磨粒切削氮化硅陶瓷的试验，进一步分析划痕形貌、切削力的变化，并验证有限元仿真的正确性。研究表明，划痕光直平整，塑性隆起很少，边缘存在较大尺寸的破碎，划痕内有局部小尺寸的破碎；划痕的深度和宽度比磨粒的切削深度和宽度尺寸略大。应力与切削力存在动态波动。随着砂轮速度的增加，切向力和法向力减小；随着切削深度的增加，切向力和法向力增大。切削力比在4～6之间变化。

To explore the mechanism of silicon nitride cutting with single grain, simulation and experimental are carried out on silicon nitride cutting with single diamond grain. Choosing truncated octahedron to simulate diamond grain, based on the Johnson-Holmquist ceramic brittle material constitutive model, the single grain linear cutting simulation is modeled by finite element method. The phenomena is analyzed for workpiece material chips, scratches morphology, stress changes and distribution, and cutting forces changes, and the effect of process parameters on the cutting force is studied. With the preparation of single diamond grain tools, the silicon nitride cutting experiments are carried on surface grinding machine with cutting depth changing, to further analyze the changes of scratches morphology and cutting forces, and verify the correctness of finite element simulation. The results show that the scratches are direct and brightness, little plastic ridges, with the larger size of broken edge and small partially broken; the scratch depth and width are slightly larger than the grain cutting depth and width. Fluctuations are existed in stress and cutting force. As the wheel speed increases, the tangential force and normal force reduce; cutting depth increases, the tangential force and normal force increase. The cutting force ratio is changing between 4 and 6.