DAMAGED LAYER AND GRINDING FORCE IN GRINDING OF MGO SINGLE-CRYSTALS - GRINDING OF BRITTLE MATERIALS (1ST REPORT)

(001) cleft surfaces of MgO single crystals were ground with a WA #120 grinding wheel. The depth of damaged layer and the grinding force were measured for [100] and [110] grinding directions. Both of them were much larger for [110] grinding than for [100] grinding. On the other hand, such dependence on the grinding direction extremely decreased when the ground surface was pre-processed by lapping. This must be due to the stress relaxation by the generation of micro-cracks introduced by lapping. Therefore it was concluded that the anisotropy of the grinding force must be attributed not only to the facility of plastic deformation but also the resistance against brittle fracture.