EFFECT OF CUTTING EDGE SHAPE OF DIAMOND ABRASIVE GRAIN ON DUCTILE MODE GRINDING OF OPTICAL BRITTLE MATERIAL

1) SD46金刚石磨粒刃口负前角分布在35 ~ 90度之间。实现硼硅玻璃延性切割的临界切割深度取决于切削刃前角，随着负前角的增大，临界切割深度从160 nm减小到60 nm。杯状切割的临界切割深度比下切大10 nm。2)对各种光学材料进行了纳米压痕实验，研究了压痕材料在压痕载荷和压痕类型下的弹性、塑性和脆性行为。结果表明，在压痕载荷相同的情况下，维氏压痕实现的最大弹性变形大于球形压痕实现的最大弹性变形。脆性断裂产生裂纹时，维氏压头的压痕载荷大于球形压头。3)通过蒙特卡罗仿真研究了切削刃截断对表面切入磨削的影响。结果表明，最大切削粒深随切削刃截断量的增大而减小，并收敛于一个由磨料粒度和砂轮浓度决定的恒定值。4)对玻璃石英进行了表面切入磨削实验，发现切削刃截断后，磨削表面粗糙度显著提高；然而，为了实现延性磨削，应选择较小的砂轮切削深度和较慢的工件速度。

1) SD46 diamond abrasive grain has a cutting edge of which negative rake angles are distributed from 35 to 90 degrees. The critical depth of cut which realizes the ductile-mode cutting of borosilicate glass depends on the cutting edge rake angle and decreases from 160 run to 60 nm with an increase in the negative rake angle. The critical depth of cut in the case of cup-cutting is 10 nm larger than that in the case of down-cutting.2) Nano-indentation was conducted for various kinds of optical materials and the elastic and/or plastic behaviors were investigated as well as the brittle behavior in terms of the type of indenter and the indentation load. It was found that the maximum elastic deformation achieved by the Vickers-type indenter is larger than that achieved by the sphere-type indenter when the indentation load is the same. The indentation load at which a crack caused by brittle fracture occurs is larger in the case of Vickers-type indenter than that in the case of sphere-type indenter.3) The effect of cutting edge truncation on the surface plunge grinding was investigated by means of Monte Carlo simulation. It was found that the maximum grain depth of cut decreases with a progress of cutting edge truncation and converges to a constant value determined by the abrasive grain size and the grinding wheel concentration.4) The surface plunge grinding experiments of glass quartz were conducted and it was found that the ground surface roughness is significantly improved by the cutting edge truncation; however, a smaller wheel depth of cut and a slower workpiece speed should be selected in order to achieve the ductile-mode grinding.