Size effect for specific energy in grinding of silicon nitride

Abstract

An investigation is reported of the `size effect' for specific energy in grinding of silicon nitride. Experimental measurements over a wide range of operating parameters using two different grit size diamond wheels show an increase in specific energy as the grit depth of cut (uncut chip thickness) is reduced. An attempt was made to account for these results by modifying an upper bound plowing model, which shows an increase in specific energy with a pyramidal tool as its semi-included angle increases. Fitting the measured specific energy to the upper bound model leads to a triangular grit cross-sectional cutting profile rounded at its tip, which can be characterized in terms of an average tip radius and semi-included angle. A plot of dimensionless specific grinding energy (specific energy divided by workpiece hardness) vs. dimensionless depth of cut (depth of cut divided by tip radius) yields a single inverse linear relationship whereby the dimensionless specific grinding energy increases steeply as the dimensionless grit depth of cut decreases below about 0.5. This would indicate that the `grit size effect' is mainly due to rounding at the abrasive cutting points.