Recent advances in contact fracture mechanics have created an opportunity to apply contact fracture mechanics to investigate mechanisms of material removal and damage penetration during abrasive machining of ceramics. Because the mechanisms of material removal influence the magnitudes and distributions of the residual stresses induced by elastic relaxation against the irreversibly deformed zone on unloading, and they, in turn, influence the damage penetration, we plan to emphasize investigation of the mechanisms of material removal in this project. These mechanisms include crushing by mixed mode fracture ahead of, beneath, and behind the diamond point and chipping at lateral cracks propagating in response to the residual stresses. Material also may be displaced from the groove by plastic flow. By modifying available mathematical models for stress distributions and crack propagation at static indentations, mathematical models will be developed to predict the extent of crushing and lateral cracking in the elongated grooves formed during grinding. The objective is to determine the relative importance of crushing and chipping alongside the track as a result of lateral cracking, as mechanisms of material removal, for various material properties and grinding conditions. The role of crushing in reducing the residual stresses that are responsible for lateral cracking will be investigated. The analytical results will be compared with the results of suitable experiments. These comparisons will be extended to include comparisons of up and down grinding, and single-point and multipoint grinding.Anticipated Results/Potential Commercial Applications as described by the awardee: This research is expected to yield improved understanding of the mechanisms of material removal and damage penetration during abrasive machining of ceramics, and improved me"hods for designing and controlling these processes. In addition, the results are likely to be useful for future research in contact fracture mechanics, which is a field ot' growing importance and where phenomena at elongated grooves represent a new area of interest, and to the understanding of other types of crushing such as that occurring during mineral processing.
