Geometry of Edge Chips Formed at Different Angles

In the edge-chip test, an increasing force is applied near the edge of a specimen until a chip is formed. At greater distances from the specimen edge, higher forces are required for chip formation. A plot can be constructed by graphing the force necessary to form a chip against the distance from the specimen edge where the force is applied. The slope of the line resulting from such a plot constitutes the edge toughness. Studies have shown that chip geometries are self-similar, such that the chip width, depth and height ratios are independent of material or total chip size. Such previous studies, however, refer to edge chips made with a force perpendicular to the specimen surface. The current work addresses the issues of applied force direction and subsequent changes in edge toughness and chip geometry when chips are formed from forces that are not perpendicular. Greater force is required to produce a chip when the force is angled away from the edge, for example, and some aspects of the resulting chip geometry resemble a flattened cone. Quantitative analyses of such geometric changes can enable back calculation of force and direction in performing edge chip failure analyses, and would aid in designing components for edge integrity when the forces are not perpendicular.