As a part of research for the adaptability of abrasive grains to various workpieces, this paper presents the results of the theoretical and experimental analysis of fracture characteristics of the cutting edge of abrasive grains when applied to grinding of workpieces with various hardness.
On the assumption that the brittle fracture takes place at a certain stress in the grain, the expressions that show the condition of fracture are derived for the cutting edges with the assumed geometry of wedge shape, by analysing the slip line field that is produced in it by cutting force. Considering the average cutting edge geometry, practical parameters which characterize fracture are proposed as follows : B
2=
HV/5.9
k and B
3=
HV/14
k for the wedge shaped edge with and without flank face respectively, where Hv is the micro-Vickers hardness of workpieces and
k the shear strength of the grain. The fracture takes place when B>1 and not when B<1. The critical hardness of workpieces predicted by the parameters is about 1000kg/mm
2 for diamond, 100kg/mm
2 for aluminum oxide and 120kg/mm
2 for silicon carbide.
The theory well explains the results of observation of fracture and wear on the cutting edge of various abrasive grains.
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