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Fracture surfaces of ZAC (a) and silicon nitride (b) SEPB specimens. The colored penetrant on the ZAC is quite definitive. The silicon nitride was more difficult to dye penetrate and low-angle incident lighting was necessary. The position of the shadow in (b) could be altered significantly, however, depending upon the lighting angle. Considerable care had to be taken to make proper size measurements as marked by the arrows in (c).
