Abstract:
Grinding with diamond wheels is the most widely used machining process for shaping and finishing advanced structural ceramics. Because of the high hardness and relatively low fracture toughness of these materials, surface and subsurface damage in the form of microcracks are often generated during grinding. Application of high removal rates and failure to select optimum grinding parameters can extenuate this damage. Recent observations on the types of grinding induced damage in a number of structural ceramics (silicon nitride, silicon carbide, zirconia and alumina with different microstructures) will be presented.. The consequence of this damage on strength determined through four-point flexure testing will be summarized. Data on the effect of grinding parameters (wheel depth of cut, grit size, and table speed) as well as the grinding direction with respect to the tensile stress direction during flexure testing will be presented. It will be shown that the size of subsurface microcracks and the influence of these cracks on strength are highly material dependent and controlled by the R-curve behavior of the ceramics. Examples of recent efforts in the detection of surface and subsurface grinding-induced microcracks by thermal wave imaging and normal incident ultrasound will be described. In addition, the need for in-process inspection and NDE for ceramic grinding will be discussed.
(Ref. SXVIII-005-97)
Source: NDE of Ceramics '97 May 4-7, Symposium on Nondestructive Evaluation of Ceramics
at the American Ceramic Society 99th Annual Meeting, Cincinnati, Ohio.
Buying the Symposium Proceedings from the American Ceramic Society.
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