Ductile Regime Grinding of Hard and Brittle Materials Based on Optimum Design of Cutting Edge Truncation

为了实现光学玻璃的延性状态磨削，重点研究了将金刚石切削刃截断并对准砂轮表面的截断方法，以优化截断条件。结果总结如下：1。利用扫描激光显微镜测量了金刚石颗粒切削刃的三维形状，发现切削刃的形状可以用三角锥来表示，其负前角平均为70度。硼硅酸盐玻璃是由一个单点金刚石磨料颗粒在超精密车床上磨削。利用上述方法对SD46晶粒的刃口特性进行了预先测量。研究发现，在负前角为70°时，材料去除过程从韧性状态过渡到脆性状态的临界切削深度约为100纳米。对表面切入磨削过程进行了计算机辅助模拟，结果表明：粗晶砂轮截断后容易产生纳米级的磨削表面粗糙度，但要实现切削最大晶粒深度小于临界深度dc的延性磨削，必须有细晶砂轮。为了实现亚微米平面度的砂轮轴向轮廓，提出了一种用圆弧包络的直线给出砂轮轴向轮廓的磨削技术。通过对金属结合剂金刚石砂轮的电接触放电加工实验，验证了该方法的有效性。

As a means to realize ductile regime grinding of an optical glass, a truncation method in which diamond cutting edges are truncated to be aligned on the grinding wheel surface is focused on in order to optimize the truncation conditions. The results are summarized as follows.1. Three-dimensional shape of diamond grain cutting edges was measured using a scanning laser microscope and it is found that the shape of cutting edge can be represented by triangular cone and the negative rake angle is 70 degrees in average.2. Boron-silicate glass was ground by a single point diamond abrasive grain on an ultra-precision face lathe. The cutting edge characteristics of SD46 grains were measured in advance using the above method. It is found that the critical depth of cut dc at which the material removal process transits from ductile regime to brittle regime is about 100 nanometers at the negative rake angle of 70 degrees.3. Computer-aided simulation of surface plunge grinding was carried out and it is found that a finished surface roughness of nanometer order is easy to be generated by the truncation of coarse-grained grinding wheel, but a fine-grained grinding wheel is prerequisite in order to realize ductile regime grinding in which the maximum grain depth of cut must be kept less than the critical depth dc.4. A truing technique in which the grinding wheel axial profile is given by a straight line enveloped by circular arcs is proposed in order to realize the wheel axial profile of sub-micron flatness. The effectiveness of this technique was confirmed experimentally by electro-contact discharge truing of a metal-bonded diamond wheel.