INFLUENCE OF GRAIN-SIZE ON THE GRINDING RESPONSE OF ALUMINA

The effect of grain size on the grinding response, i,e., grinding forc es, surface roughness, and grinding-induced subsurface damage, is inve stigated in a series of alumina ceramics with the average grain size r anging from 3 to 35 mu m. The grinding forces are measured as a functi on of depth of cut in surface grinding, It is found that the grinding forces decrease as the grain size is increased from 3 to 9 mu m. But a t larger grain sizes, the grinding forces are independent of the grain size, Subsurface damage in grinding is observed using a bonded-interf ace sectioning technique. The subsurface damage is found to consist of intragrain twin/slip bands and intergranular microcracks. The density of grinding-induced subsurface microcracks increases with the grain s ize, In addition to using optical microscopy on the sections of the gr ound specimens, a nondestructive thermal wave measurement technique is used directly on the ground surfaces for the detection of grinding-in duced subsurface microcracks. The grain size dependence of the microcr ack density estimated from the thermal images is found to agree with t he results obtained using the bonded-interface technique.